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Sky Roundup for August 2010
Astronomical highlights for the month of August
A Twilight Trio and Midnight Meteors
Two years ago this month, sky watchers were treated to the twilight sight of Venus, Mars, and Saturn clustering close to the horizon at sunset. That same apparition is back this month; look for it as evening twilight gives way to the full dark of night. (See Chart 1.)
The three planets continue to cluster all month long in the west-southwest and are joined by the waxing crescent Moon on August 12th as an opportunity for photogenic composition. Venus and Mars appear to draw closest together by August 20th, and ought to be easy to spot with a binocular or at low magnification with your telescope. See Chart 2.) Saturn drops from view in early twilight by month’s end.
Tiny Mercury puts in an appearance just above the horizon as evening twilight starts but disappears into the glare of the Sun by mid-month. (See Chart 3.)
The date of August 12th is also significant since that is the traditional peak for the annual Perseid meteor shower. Every year at this time, planet Earth swings through the dusty debris left in the wake of Comet Swift-Tuttle, the acknowledged source of the Perseid meteor shower. The minute particles slam into Earth’s upper atmosphere at ramjet speed, whereupon the fiery glow of meteors comes from both the ionizing air layer around the particles and the particles themselves burning up.
The Perseids are noted for producing approximately 100 meteors per hour and occasionally bright fireballs, the kind that light up across the sky for an instant. With the peak of the meteor shower occurring after New Moon (on August 10th), this year’s meteors ought to be a fine event for the whole family. Here is additional information about predictions for the peak of the shower.
Of course, the name for the meteor shower traditionally derives from the point in the sky whence meteors seem to radiate. In this case, the general direction of the constellation Perseus would be the ideal place to look, but the meteors themselves will fan out across the sky generally from east to west by midnight and thereafter as we seen from your earthly vantage.
In recent years during the meteor shower, some observers have watched the Moon with cameras. This may sound odd but it has practical value from the perspective of observation. Both amateur and professional astronomers have recorded impacts of Perseid meteors on unlit parts of the Moon! With the Moon at waxing crescent, perhaps there’s the chance to spot lunar impacts. For more information on this practice, check here.
For this month, stately Jupiter rises just before midnight and majestically marches across the night sky all night long, standing high in the south-southwest by dawn. The king of the gods, easily spotted with eyes alone or a good binocular, is quietly accompanied by his own mythic father, Uranus, only visible with moderate-to-high magnification in a good telescope. (See Chart 4. The pinpoint of Uranus is shown by the red cross around it.)
All in all, August rates as a good month to catch our cosmic neighbors at play.
Sky Roundup Almanac for August 2010
August 1:
Cluster of Venus, Mars, and Saturn in west-southwest at sunset
August 2:
Last Quarter Moon
August 10:
New Moon
August 12:
Waxing crescent Moon joins Venus, Mars, and Saturn at sunset; Perseid meteors at annual peak
August 16:
First Quarter Moon
August 24:
Full Moon
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Sky Roundup for July 2010
Astronomical highlights for the month of July
Freedom from Wont
It’s both customary and appropriate this month to celebrate our many freedoms. And we ought to be encouraged to do so with a grand show of unabashed patriotism. Enshrined in the Declaration of Independence and enumerated in the Constitution, our freedoms are enviable liberties granted to the people of the United States that no elected leader or foreign entity shall take away from us.
However one shall celebrate, with hometown parades, backyard barbecues, family vacations, lawful assemblies, or earnest prayers, this month of remembering our country’s founding perhaps should include a quiet recognition of yet another liberty.
Implicit in the freedoms that are ours to enjoy by right and by law, we also have the freedom not to follow the crowd. This does not mean shirking patriotic duties and lawful responsibilities, but it does imply that we have an obligation to think freely for ourselves, to make up our own mind, and to act rationally on our thoughtful commitment.
One might think this is an obvious sentiment already enjoyed by many. If so, then it is to be commended. But if you haven’t seen much original thinking on display, then perhaps you yourself can exercise it. Prepare yourself by honing an ability to fashion solutions to knotty situations. Practice to think. Then put into practice that thought with sound action.
Let July mark your month of independence from your usual observations and outlook. Re-cast your priority to view the night sky with greater enthusiasm. Make it a point to set up for observation, to spy a few more nightly glimmers in the humid haze, to spot a few untried star clusters, to fashion finally that homebuilt telescope, and to plan the rest of your summer excursions to area star parties.
For this month, let’s see what’s out of the ordinary and worth spotting with modest magnification or even eyes alone. Of course, take time to gaze at the stars, peek at the planets, and swoon over the Moon, but take time, too, to view the odd and out-of-the-way. It may seem like we’re simply destined to see what others already have thought to observe; rather, we ought to look at all of these celestial objects with renewed wonderment, perhaps as we did when we first spied the heavens all on our own.
Be original in your pursuit of the night sky. Take an individual approach. No need to view what others are wont to observe. Free yourself to choose your own favorites. It may sound too easy and naïve to say, but so is following the crowd. When pursuing your avocation, live in liberty; don’t lumber with lemmings.
Sky Roundup Almanac for July 2010
July 4:
Last Quarter Moon
July 11:
New Moon; total solar eclipse (not visible from the Midwest)
July 18:
First Quarter Moon
July 25:
Full Moon
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Sky Roundup for June 2010
Astronomical highlights for the month of June
The Moon in June
The last several installments of Sky Roundup have looked at a few of the more notable aspects of the recent seasons, namely, the stars and planets that are noteworthy to view. Several of the typical and brighter seasonal constellations were mentioned and, of course, the positions of the visible planets. And, at a bare minimum, the dates of the phases of the Moon were listed in the Sky Roundup Almanac.
But, of course there is more to the night sky. And the Moon is often a prominent part of that night sky. The Moon in June offers a fine diversion.
Known by the Algonquin Indians as the “strawberry moon”, since the red fruit was ripe and ready to eat by this month, the Moon in June was also known variously by Europeans, who called it the Flower Moon, the Rose Moon, or the Hot Moon. (Btw, there is a Cold Moon, i.e., the Moon in December, as known to us by Native Americans.)
This month the Moon runs its usual course of phases, as listed (below) in the Sky Roundup Almanac, but runs near a few planets as well.
On June 6th, around 4 a.m. in the vicinity of Pisces (the Fishes), the Moon, just passed Last Quarter, passes north of a pairing of Jupiter and Uranus. (See Chart 1 for the general location.) Those two faraway planets will appear less than ½º apart! The king of the gods paired with the father of the gods ought to make an interesting contrast when viewed through a large telescope.
The bright, banded, white-and-tan disk of Jupiter paired with the dim greenish dot of Uranus nearby to the north will be a good challenge to capture with the right magnification in the same field of view. (See Chart 2 for a close-up and note that dim Uranus would appear within the small circle). With a telescope outfitted with electronic setting circles, the two planets ought to be relatively easy to find since they are a Moon’s width from the intersection of the celestial equator and the ecliptic.
On June 14th, the waxing crescent Moon, between Cancer (the Crab) and Gemini (the Twins), passes south of Venus in the early evening sky. (See Chart 3 for the general location in evening twilight.) Typically, the growing, or “waxing”, phases of the Moon are viewed always in the first half of the lunar month in the early evening sky after sunset; the shrinking, or “waning”, phases are only seen in the latter half of the lunar month late at night and before sunrise.
Two days later, on June 16th, the thickening crescent will move below Mars and nearby Regulus, the brightest star in Leo (the Lion), seen in evening twilight. (See Chart 4.)
On June 18th around midnight, the First Quarter Moon, leaving Leo, moves south of Saturn in Virgo (the Maiden). (See Chart 5.)
Even though the daily rotation of Earth makes celestial things move from east to west, note that the Moon moves gradually farther to the east every night, an effect we see of its own motion in orbit around Earth.
The start of a typical lunar month is the phase of New Moon, generally unseen due to the glare of the Sun, unless there is an exact alignment for a total solar eclipse to occur, and only then will that phase actually be visible. Since the time it takes the Moon to orbit Earth, i.e., a lunar month, is the basis for our calendar month, then two weeks after New Moon phase is Full Moon phase, at which the Moon rises in the east as the Sun sets in the west.
On its way to its full phase, the Moon passes a bright star this month. On June 21st, the waxing gibbous Moon steers south of singular Spica, the brightest star in Virgo, of which the Maiden is otherwise forlorn of bright stars to observe.
This date also marks the Summer Solstice, the start of Summer for the Northern Hemisphere, when the axial tilt of Earth aligns to the center of the Sun. (See the Almanac, below.)
Typically, this is the longest day of the year in terms of hours that the Sun remains above one’s local horizon, but it is not typically the hottest day. The hottest time usually arrives about one month later, due to the time it takes the effect of heating from that day’s maximum hours of sunlight to circulate to us.
In ancient pre-Christian calendars, this time of year was designated as Midsummer, when calendrical timekeeping was governed by cross-quarter days. (See Sky Roundup Archives for February 2010.) Flowers were gathered, bonfires were lit, and dances were held to welcome warmly this marriage of Heaven and Earth, as symbolized by the solstice, and was seen as a lucky time of year. This appears to be the origin for the popularity of the month of June for weddings.
But the Moon itself is not left out of the wedding ritual. You’ve heard of newlyweds going on a “honeymoon”? The term and the practice arose from an old tradition in Ireland, where the newlyweds’ parents sought to keep them imbibed with a good supply of mead, a drink fermented from honey, for a full cycle of lunar phases. After the sweet interlude of this “honeymoon”, the hopeful parents then expected the newly wedded couple to have a son within the first year of marriage.
After midnight on June 24th, the waxing gibbous Moon continues its travels past stars, including the look-alike to Mars, ruddy Antares, brightest star in Scorpius (the Scorpion) and 15th brightest in the whole night sky.
The waning gibbous Moon closes out the month, appearing in the night to nod to nearby Neptune. This is only an apparition, of course, as both are not at all close to one another, while Neptune, far more distant than the Moon, appears in Aquarius (the Water-Bearer) only as a tiny bluish dot when viewed through a large telescope.
In this pre-dawn pairing on June 30th, the Moon is too far from Neptune to be seen in the same field of view as this most distant planet. (See Chart 6, which shows about how far the planet appears from the waning gibbous Moon. Note that the planet will be found within the small circle.)
Certainly the Moon in June is busy with most of the planets this month. You can get busy, too, to welcome the celestial start of observing for the warm months of the year.
Sky Roundup Almanac for June 2010
June 4:
Last Quarter Moon
June 6:
Waning crescent Moon north of Jupiter and Uranus
June 12:
New Moon
June 14:
Waxing crescent Moon south of Venus
June 16:
Waxing crescent Moon south of Mars
June 18:
First Quarter Moon; Moon south of Saturn
June 21:
Summer Solstice arrives at 6:38 a.m. CDT
June 26:
Full Moon
June 30:
Waning gibbous Moon near Neptune
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Sky Roundup for May 2010
Astronomical highlights for the month of May
May We All Observe
From April showers we do get May flowers. In this grand month the greening of Spring continues apace as fresh blooms dot the roadsides and a riot of color appears in the neighbors’ gardens. The night sky also blooms with a fresh set of constellations easing their way into the purpling mantle of evening.
The large constellation of Boötes (the Herdsman) heralds the full arrival of Spring as this ancient pattern is a patron of the outdoors and also occasionally represents a vintner in the fields. Its brightest star, Arcturus, a red-giant star, appears orange in our night sky.
In planetariums, this star is most often pointed out as one found from the direction of the Big Dipper’s handle. That is, the bend in the handle of the Big Dipper forms an arc, which one then uses to “arc to Arcturus” away from the bowl of the Dipper.
Another springtime pattern is the constellation of Virgo (the Virgin), typically a symbol of fertility. After one arcs to Arcturus, one then can “speed on to Spica” by dropping to the south from Arcturus to that star, which is the brightest one in Virgo.
Hercules (the Strongman) flexes his muscles and starts to climb into the night sky. His most famous asterism, the Keystone (since it resembles the shape of the capstone found in Roman arches) represents his tight torso. Amid the stars of this pattern are found a couple of summertime favorites, namely, globular clusters, about more will be presented in a later installment of Sky Roundup.
And between these two springtime patterns is a small gem of a constellation, Corona Borealis, with its brightest star, Gemma. The name of the pattern translates from Latin as the Northern Crown. This semi-circle of stars is also fine to scan with a binocular, but contains no well-known deep-sky objects that amateurs may easily observe.
This is just a sampling of patterns to be glimpsed as we get set for warmer months of observing and the opening of a promising season of star parties across the middle of the country. If you’re interested in upcoming gatherings under the stars, check here and here.
In the meantime, let’s see what May brings of the planets:
Mercury has disappeared in the western sky, lost in the glare of the Sun, and is no longer visible like last month.
Venus shines brightly, and higher this month than last, after sunset in the western sky. In a telescope, the brilliant planet appears in a gibbous phase, that is, nearly full, as seen from Earth.
Mars continues to stand high toward the southwest in Cancer (the Crab), gleaming a distinct light orange in the night sky.
Jupiter, like Mercury last month, has re-emerged from the glare of the Sun into our morning sky, rising ahead of the Sun. A good telescope can glimpse it in morning twilight.
Saturn in Virgo (the Maiden) still can be found east and south of Mars.
Uranus and Neptune are re-emerging and rise ahead of the Sun, in the vicinity of Jupiter.
May we all observe all we can this month.
Sky Roundup Almanac for May 2010
May 6:
Last Quarter Moon
May 14:
New Moon
May 20:
First Quarter
May 27:
Full Moon
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Sky Roundup for April 2010
Astronomical highlights for the month of April
April Showers and Stars' Powers
Since we as Earthlings began looking at the stars so very long ago, our imagination has filled in the night sky where a lack of knowledge had kept us wanting. We have connected the stars to our daily lives in ways that have both entertained and informed. We have peopled the sky with an array of winged birds, mighty heroes, mythic beasts, and crawling creatures. Not only have their storied depictions aroused wonder, but a few of those depictions are wonders themselves.
Look at a typical star chart and you begin to notice some interesting things about the creatures that the charts purport to show. It has been known for some time that the various beasts of the night sky can be grouped by their apparent height in the sky during a particular season. Constellations of birds generally are found winging high across the sky in the warm months of the year while star patterns of beasts great and small lumber along the horizon in colder times.
For the month of April, and at our mid-latitude location, Corvus (the Crow) appears to hop along the treetops in April while Hydra (the Water Snake) slithers close to the horizon. Taurus (the Bull) heads toward the west where the Sun sets, while Cygnus (the Swan) stands poised to take flight on the northeast horizon.
Cancer (the Crab) snaps its pincers at the hind quarters of Canis Major (the Smaller Dog) in the southwest, while Leo (the Lion) and Leo Minor (the Smaller Lion) march proudly halfway up in the sky from east to west. Ahead of the them, Lynx (the Lynx) and Camelopardalis (the Giraffe) move stealthily past Ursa Major (the Greater Bear) and Ursa Minor (the Smaller Bear). Behind them, Canes Venatici (the Hunting Dogs) chase those two bears around and around Polaris, the North Star, in the tail of Ursa Minor (the Smaller Bear). Between the latter two coils Draco (the Dragon).
These star patterns are just a few of the beasts imagined in the night sky. Of course, all of these constellations are only available to us as long as we can view them. And as April is traditionally wet and rainy, it may not be often this month that we can glimpse the glory of the night sky.
Observing each pattern alone is fun enough to do, when weather permits, especially with low power of a good telescope or a large binocular. Take a lingering look at Taurus to get a glimpse of the star clusters of the Hyades and the Pleiades, which won’t return to pre-dawn skies until early Autumn. With a decent large telescope, look also to Leo and Leo Minor for a gaggle of galaxies. Mere specks of light at high magnification, you’ll witness light from millions of light-years away. Next door in Cancer is the well known Beehive Cluster and a pretty sight at low magnification.
Again, these are just a few wondrous gems that represent the power of the stars, that is, their ability to hold our interest and draw us back again and again to observe them. That power will be strong enough this month to lure us out-of-doors, especially when we see what’s on tap with some of our closer and more familiar nighttime neighbors:
Mercury reappears in the western sky after sunset, no longer lost in the glare of the Sun. Before mid-month will be one of the better apparitions for this hot, little world.
Venus shines brightly, but low, after sunset in the western sky.
Mars continues to stand high toward the southwest in Cancer (the Crab), gleaming a distinct light orange in the night sky. Through a good telescope, Mars’s size is shrinking and it simply appears as a fading dot.
Jupiter, like Mercury last month, is now lost in the glare of the Sun and will re-emerge in our morning sky, rising earlier and earlier ahead of the Sun. A good telescope can glimpse it in morning twilight.
Saturn in Virgo (the Maiden) still can be found east of Mars before morning twilight and is a pretty, pale, ringed wonder at even modest magnification in a telescope. Look for its line-up of moons. Saturn has many moons, several of which are visible with an amateur astronomer’s telescope.
Uranus and Neptune are re-emerging from the glare of the Sun and rise ahead of the Sun.
Answer the lure of the night sky as often as you can this month. If you happen not to have a clear night this month, there are always plenty of cloudy night activities to occupy one’s time, but let’s hope you don’t find the time to do those things.
Sky Roundup Almanac for April 2010
April 6:
Last Quarter Moon
April 8:
Mercury at greatest elongation (19° east of the Sun), in the western sky after sunset
April 14:
New Moon
April 21:
First Quarter Moon
April 28:
Full Moon
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Sky Roundup for March 2010
Astronomical highlights for the month of March
Out Like a Lamb, In Like a Lion
Doesn‘t the folklore expression for the month of March read more like: Comes in like a lion, goes out like a lamb? Well, yes, it does, if one were to describe the weather of March. In meteorological terms, the start of this month is usually considered blustery while the end of the month is more tame.
However, this year, like much of the wild weather around the entire northern hemisphere, has been topsy-turvy. And March seems to be following the unsettled nature of this season’s weather and has actually arrived in the Midwest more tame than in previous years.
Does that portend nasty weather for the departure of the month? No, not necessarily. The weather for a single month, or for a single season, or for several years of seasons, does not necessarily portend a genuine trend in meteorology or even climatology.
But in astronomical terms and in the night sky, the month of March is accurately described here for the moment as we say farewell to the constellation of Aries (the Lamb) and say hello to the star pattern of Leo (the Lion).
In early March, the Lamb nears the western horizon by early evening; by month‘s end, it has disappeared altogether. The Lion, though, is seen higher in the sky every night in the eastern sky, so that by mid-month it stands at the zenith by 11:00 p.m. Its bright star Regulus, the heart of the lion, glows bluish-white.
Aries is a small constellation of the Zodiac but doesn‘t look like a lamb; Leo is a much larger constellation of the Zodiac and really does resemble the profile of a lion with a furry mane. Within the Zodiac, that swath of sky and star patterns through which the planets move, let’s see what planets are visible.
Mercury has disappeared for the month as it’s lost in the glare of the Sun.
Venus emerges from the glare of the Sun this month, shines brightly, and is seen low in the western sky sunset.
Mars continues to stand high all night long in Cancer (the Crab), gleaming a distinct light orange in the night sky. Having reached opposition in January, the Red Planet is still seen, for the most part, rising as the Sun sets, making the small, dry, cold world visible all night long. Through a good telescope, Mars’s size is shrinking as Earth pulls ahead of it in its orbit.
Jupiter, like Mercury, is also lost in the glare of the Sun for this month. By month’s end, it has crossed into our morning sky and will rise ahead of the Sun. A good telescope can barely glimpse it in morning twilight.
Saturn in Virgo (the Maiden) still can be found east of Mars before morning twilight and is a pretty, pale, ringed wonder at even modest magnification in a telescope.
Uranus and Neptune are both lost in the twilight glare of the Sun and cannot be seen well. The twin large worlds have crossed over into our morning sky and rise ahead of the Sun.
By the way, get set for Daylight Saving Time when we “spring ahead” on March 14. Make certain that your clocks and computers and phones are set ahead one hour. And, if the weather outside isn‘t roaring like a lion, don’t be sheepish about observing the night sky. Get out under the stars as often as you can this month.
Sky Roundup Almanac for March 2010
March 7:
Last Quarter
March 15:
New Moon
March 23:
First Quarter
March 30:
Full Moon
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Sky Roundup for February 2010
Astronomical highlights for the month of February
Short Month For a Reason
Our modern calendar is an amalgam of ancient rituals, holdover festivals, feast days, and artifacts from previous calendars. Without delving too deeply into the origin of the modern Gregorian calendar (other than to say that the name comes Pope Gregory XIII, who, in 1582, introduced it to replace the older, former Roman calendar), a more modern calendar keeps us from becoming increasingly out-of-sync with the seasons.
Hence, our more modern calendar is based on the change of seasons, astronomically defined, than of the more ancient rituals on which it was originally constructed. For example, when the axis of Earth lines up with the center of the Sun (no matter which side of the Sun the Earth is on), then we have a solstice. At right angles to that line-up either side of the Sun, we have an equinox. But any of these line-ups seem to occur when the weather suggests that the season is already well underway.
“Solstice” and “equinox” are old words, derived from Latin, but which have apparent roots deeper and older than that ancient language itself. Also known as “quarter days” since they divide the calendar into fourths, solstices and equinoxes have long traditions that hearken back to Roman, Teutonic, Gaelic, and pagan seasonal festivals. Though our modern calendar duly marks seasonal change with perfunctory regularity, the trappings of older timekeeping lingers throughout the seasons, enlivening their passage with ritual meaning.
Cross-quarter days might sound odd, but we still include most of them in our modern calendrical cycle; we simply know them by other, popular names.
So, while the quarter-day defined by, say, the Autumnal Equinox, marks the start of Fall and the quarter-day defined by the Winter Solstice marks the start of Winter, the cross-quarter day known as Hallowe‘en, comes midway between the equinox and the solstice and is celebrated on October 31. This date marked Summer’s end and a time to prepare for Winter by mending torn seams to hold against the blustery winds ahead. At this time, too, those same winds stretched wide the seams of Earth, allowing spirits of the underworld to rise and haunt those ill-prepared for Winter’s arrival.
Similarly, the period from the Winter Solstice to the Vernal Equinox has its own cross-quarter day, and it is February 2, also known as Candlemas Day or Ground Hog Day. Both dates look with anticipation to a brighter, warmer future with the arrival of Spring.
From the Vernal Equinox to the Summer Solstice, the cross-quarter day occurs on May 1, also known as May Day, which has various secular and religious connotations worldwide. Dancing around maypoles, holding marches and rallies, and honoring the Virgin Mary are all part of May Day observances.
For the period from the Summer Solstice to the Autumnal Equinox, the cross-quarter day is August 1, and has, as its observance, such festivals as Lammas (literally “loaf-mass day”) in certain European countries and Lughnasadh (as presented in Gaelic); these observances traditionally have involved the preparation of breads to anticipate a bountiful harvest. Curiously, there is no known popular festival in this country commensurate with the observance of this particular date.
One thing we can celebrate is that this month is mercifully short, a point not lost in previous calendars when February was also often listed as the shortest month and one often associated with inclement or cold weather.
On a positive note, though, the month was also one of sincere preparation for the anticipated and eventual greening of Earth. In addition, it became a time to profess one’s love for another, to stand together against the vagaries of a cold world and to look ahead to happier, warmer times. Not being a very long month, then, preparation was expected to be both deliberate and genuine, for, like the chance for love, the passing season waits for no one.
Though it’s foul and cold now, let’s not wait to get outside and attempt to observe some of the lovely sights that can prepare us for longer, happier sky gazing during the warmer days ahead.
Mercury barely clears the eastern horizon before sunrise by the start of the month for viewers in the Northern Hemisphere. By the end of this short month it veers into the glare of the Sun and is lost from view. (See Chart 1.)
Venus cannot be seen well from our vantage on Earth since the glare of the Sun keeps this brilliant planet fairly hidden all month long; pretty Venus emerges in the western sky, though, after sunset by month‘s end. One can glimpse it through a telescope in close proximity to Jupiter just after sunset near the western horizon on the 16th.
Mars continues to stand high all night long in Cancer (the Crab). Having reached opposition last month, the Red Planet is still seen, for the most part, rising opposite the setting Sun, making the small, dry, cold world visible all night long. Through a good telescope, Mars’s size is shrinking as Earth pulls ahead of it in its orbit.
Jupiter (in Aquarius) is still visible as it heads into the glare of the Sun toward the southwest horizon by evening twilight and becomes less visible by month‘s end, but for the aid of a good telescope. (See Chart 2.)
Saturn in Virgo (the Maiden) still can be found east of Mars before morning twilight and is a pretty sight at modest magnification in a telescope. (See Chart 3.)
Uranus and Neptune, amid Pisces (the Fishes) and Aquarius (the Water-Bearer), are barely visible to the southwest. These twin worlds are only visible with fairly large telescopes just after sunset.
The Moon is always a pleasing sight to watch as it wends its way through its expected phases. (See the Sky Roundup Almanac for dates of these phases.) This month the Moon pairs with planets near the horizon. On the 11th and 12th, the waning lunar crescent can be spotted near Mercury, which hugs the southeastern horizon just before dawn. (See Chart 4.)
On the 16th, a waxing lunar crescent is poised high above the pairing of Jupiter and Venus near the west-southwestern horizon. (See Chart 5. Yes, that's both Jupiter and Venus crowded close to the horizon.)
Both of these slim crescents in February are worth observing, since one can attempt to spot these thin slices of the Moon without optical aid.
Don’t let the month go by without an observation. It’s a short one and will be gone before you know it.
Sky Roundup Almanac for Feb. 2010
February 5:
Last Quarter Moon
February 14:
New Moon
February 22:
First Quarter Moon
February 28:
Full Moon
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Sky Roundup for January 2010
Astronomical highlights for the month of January
However Round We Like Them
It was a curious thing to see on TV as we ended the previous year and welcomed the new one: News reports heralded the end of a decade and the start of a new one. Which decade was that? It was a good bet that the newsies were referring to the Aughts, that is, the most recent double-zero decade. In that case, we have had ten of those double-aught years, but one of them belonged to the last millennium.
The last day of the last year of the last century occurred on December 31, 2000. That well-rounded number for that year also capped the end of the last millennium. The start of the current decade in the new century in the new millennium really began on January 1, 2001. That is, if anyone is counting accurately, the actual decade of the first millennium is still underway; so, we ought to have another year to go, and an aught-year at that, to cap this first decade. That is, the date of December 31, 2010, will mark the end of this first decade.
But when it comes to round numbers, like dates in time, we seem to like them, celebrate them, even if they aren’t always accurate. A close approximation appears sufficient. So, if we haven’t actually had ten years in the first decade of the new millennium, who cares? We just had ten double-zero years in a row. That’s something to celebrate. Next year we’ll celebrate that actual first decade.
Well, let’s examine this affinity for things well-rounded and see how well we go for it.
Let’s take the length of a day, our daily unit of time, and the length of a year, our annual unit of time. How long does Earth take to spin once, or, more accurately, how fast does Earth rotate? How long does it take Earth to move in its orbit, or, more exactly, how long does it take Earth to revolve around the Sun? Of course, we know “our” day as 24 hours, a nice small number, but no zeroes in it, and we know “our” year as 365 days, a nice whole number. Actually, Earth rotates once every 23 hours, 56 minutes, 4.2 seconds, and, it revolves once every 365 days, 5 hours, 49 minutes, 12 seconds in a single calendar year. But we usually round off the spin both on Earth’s axis and around the Sun because we like round numbers.
Let’s take the velocity of light, the speed limit of the cosmos. How fast does light travel? We learn in school that light travels 186,000 miles per second, a nice round, big number with zeroes in it. Actually, light travels at 186,282.6 miles per second. But we usually round off the speed because we like round numbers.
Let’s take a light-year, a unit of interstellar distance but not of time. How far is that distance? We also learn in school that in one year light travels nearly 6 trillion miles, a really big number with lots of zeroes in it, and represents a convenient yardstick, so to speak, for measuring distances to the stars. More exactly, that’s 5,865,696,000,000 miles, indeed a huge number. But we usually round off the measure because we like round numbers.
However faraway are the stars in light-years does represent the amount of time in our years it takes stars’ light to reach us on Earth. The closest star to Earth (after our own Sun) is Alpha Centauri, which is 4.3 light-years from us; it also takes 4.3 years for that star’s light to reach us. Light from our Sun, which is much closer, takes nearly 8½ minutes to reach us. So, for example, if there’s any change on the Sun, it would be nearly that many minutes later for us to observe the change.
The precise terms of rotation, revolution, velocity, and distance are all things common to a serious astronomer’s approach to observing the cosmos, whereas a casual stargazer is more likely to refer to these same things, though less precisely, as spin, speed, and space when viewing the night sky. The difference may be in the precision of expression; however, both still want accuracy in what they observe.
This point of precision is not lost on astronomers, amateur or professional, for they need it to be able to pinpoint observations and report on them with accuracy. Earth spinning in rounded-off time won’t have the necessary precision for long-term timekeeping. Consequently, an inaccurate clock won’t get us to work on time, just as an inexact calendar won’t show us the timely passage of round numbers. And, using a rounded-off velocity of light may be sufficient to gauge the vastness of space, but it will not pinpoint with precision the location of spacecraft exploring the Solar System or one day heading to the stars.
Certainly in our daily lives we round off both time and distance for convenience, since we don’t need the precision of astronomers, but let’s not forget the importance of accuracy; otherwise, we’re celebrating our round numbers for nothing. Though however round we like them, our numbers need a level of precision to let us accurately know our world.
Do you still want to round off the accuracy? Accuracy we ought or it’s all for nought.
What won’t be all for nought is a look at January skies to open this last year of the first decade of the first century of the new millennium. We ought to brave the cold, for, if it’s clear outside, it’ll make you well-rounded to observe some of the round, though distant, objects in the night sky.
Mercury last month sneaked back below the western horizon and has been lost in the glare of the morning Sun. It re-emerges above the eastern horizon before sunrise by mid-month. The hot little planet goes through phases like the Moon, so it doesn’t always appear round when you view it safely near the Sun through a good telescope. (See Chart 1.)
Venus cannot be seen from our vantage on Earth since the glare of the Sun keeps this brilliant planet hidden all month long.
Mars stands high all night long between Leo (the Lion) and Cancer (the Crab). Mars reaches opposition, which means that the Red Planet is seen rising opposite the setting Sun, which is why the cold, small planet is visible in the night sky all this month. (See Chart 2, which by mid-month shows Mars and Saturn above the western horizon before dawn.)
Jupiter makes its way farther west in the sky as the month progresses, heading toward the southwest horizon by evening twilight. Still a bright light in the evening sky, the big planet looks nice and round at decent magnification in a large telescope. (See Chart 3.)
Saturn in Virgo (the Maiden) stands pale and cold east of Mars before morning twilight. For part of this month, its big, bright rings become just a bit more rounded in a telescope as we view it gradually increasing its angle from the Sun. (See Chart 2 again.)
Neptune and Uranus, twin large worlds, barely appear round even in large telescopes, due to their great distance from us, rounded off or not.
The Moon, our closest round celestial object, rounds out the month with an extra-large appearance, when its closest approach to Earth, or perigee, coincides with its Full Moon phase on the 30th, making the Moon appear even larger and rounder. Other dates for its phases are listed in a rounded-off Sky Roundup Almanac this month.
By the way, Earth itself makes its closest approach to the Sun this month on the 3rd. At perihelion, Earth reaches that annual point in its out-of-round orbit where it swings to about 91,000,000 miles from the Sun, which is just a tad closer than its average distance of 93,000,000 miles, another nice round number.
Though Earth is closer to the Sun during the Northern Hemisphere’s winter, the Southern Hemisphere’s summer is no hotter due in part to the excess of water that rounds lands south of the equator, moderating the influence of the Sun’s incoming radiation on those lands.
All in all, 2010 looks like a good bet for observing a host of astronomical phenomena, including all of the familiar round objects we’re used to viewing. You can be as accurate as you want in your observations as a serious amateur, or, you can simply be well-rounded and enjoy your night-sky views all year long as a casual stargazer.
Sky Roundup Almanac for January 2010
January 7:
Last Quarter Moon
January 15:
New Moon
January 22:
First Quarter
January 30:
Full Moon
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Sky Roundup for December 2009
Astronomical highlights for the month of December
The Night Before Christmas
This stargazer’s parody of “A Visit of St. Nicholas”
—with apologies to Clement Clark Moore
‘Twas the night before Christmas,
When all through his house
A stargazer was stirring, clicking his mouse;
His mounting set up in the backyard with care,
In hopes that clearing skies soon would be there.
He could’ve been nestled all snug in his bed,
But visions of nebulae danced in his head;
And grabbing a kerchief to dust a lens from its cap,
He caffeined his brain to shun a long winter’s nap—
When out on the lawn there arose such a clatter,
He sprang from his chair to see what was the matter:
Away to his set-up he flew like a flash,
Hoping his ‘scope didn’t loosen and crash.
The moon, on the breast of new-fallen snow,
Gave a luster of mid-day to objects, ya’ know:
When, what to his wandering eyes should appear,
But a case full of eyepieces amid his old gear;
Fellow geeks always bought these, so lively and quick,
He knew in a moment they’d all be heartsick.
More lenses he now owned and savored his claim,
And he whistled, and shouted, and called them by name—
“Now, Brandon! now, Nagler! now, Ethos! and Vixen!
No coma! Flat fields! Star parties I’m blitzin’;
To the top of each planet, to the top of Straight Wall,
I’ll dash to see nebulae, faraway all!”
He gathered his new gear, so pleased he might cry,
And carried all to his ‘scope, its mount to the sky,
So, up past his house-top his ‘scope aimed anew,
A case full of lenses—and such neat stuff too.
With stars all a-twinkling from heat off the roof,
The night sky unveiled its warp and its woof;
As he drew up a chair, and was turning around,
Down next to his ‘scope the ‘gazer came with a bound.
His parka lined in fur
From his head to his foot,
And his clothes came all furnished
With pockets to boot:
This new bunch of toys
He now kept near his back,
And he thrilled like a youngster
As he opened his pack;
His eyes how they twinkled!
Each eyepiece how merry—
Were just what he wanted,
Whence they came he was wary;
Ev’ry ocular gleamed
Each drawn up with a bow,
Who could’ve left them and
Left no tracks in the snow?
He thought for a bit
Of this season of year,
And thought it unlikely he’d
Earned such good cheer.
Still he was thankful
And humbled quite by it;
He vowed to do better
And stay on a diet.
He was chubby and plump—
His right jolly old self;
From too much late snacking
In spite of himself.
A wink of his eye,
And a twist of his head,
Soon gave him to know
Where each eyepiece might thread.
He spoke not a word,
But went straight to his work,
And logged all his sightings:
Then turned with a jerk,
And laying his pencil
Aside of his prose,
And giving a nod,
To his warm room he rose.
He sprang to its desk,
Jotted notes in a whistle,
And away he then flew
To look through a Plössl:
But all heard him exclaim
Ere he gazed in the night,
“Merry Christmas to all,
And to all A Clear Night.”
Year-End Cosmic Roundup
Now for some enjoyment from the cosmos itself as the month of December closes out the year with planets aplenty and the Moon’s light on the landscape.
Mercury, the closest planet to the Sun, graces our horizon as the “evening star” this month but not as a Christmas star. Its relative brightness is due to its observed position east of the Sun, hence it shows up in the western sky after sunset. At this position, the planet shines best since it’s at its greatest angle from the Sun as seen from our earthly vantage. By the end of this month, this little hot world can be glimpsed just above the treetops, and only carefully with a telescope, as a thin crescent. (See Chart 1, and note that the little world in evening twilight is actually seen to the left of the “M” in the word Mercury.)
Venus disappears into the glare of the dawn Sun and is not well placed to be seen. When we next see it emerge in February on the other side of the Sun, it, too, will be a brilliant “evening star” seen in the western sky just after sunset.
Mars stays relatively bright to nearly zero magnitude by month’s end as it begins its characteristic retrograde motion (or, backward movement) in Leo (the Lion), whose star pattern is best seen rising by midnight. (See Chart 2.) Late next month, the cold Red Planet reaches opposition, which means that it stands opposite the Sun from our vantage. So, late next month as the Sun is seen setting, Mars will be seen rising.
Jupiter gleams at it transits by sunset this month. And the largest planet puts on a month-long show as it appears through a good telescope to pass south of distant Neptune; its closest apparition is on the 19th. There is also a double shadow transit visible with good magnification across the face of Jupiter’s disk on the 20th, which means that two of Jupiter’s moons will cast their shadows onto the cloudtops of the largest planet.
Saturn stays poised near the celestial equator in the constellation of Virgo (the Maiden) in our pre-dawn sky. (See Chart 3 for a look where to find the Ringed Planet at about 3 o’clock in the morning.) Its famous bright rings are beginning to tilt outward and are visible with a good telescope, but not with a small binocular.
The Moon doesn’t disappoint as it glides past star clusters and planets throughout this month. On the 1st, the Moon passes the Pleiades; on the 3rd, it’s by open cluster M35; on the 6th, it’s near Mars; on the 10th, it stands near Saturn; on the 18th, it moves near Mercury; on the 21st, it’s just above Jupiter; on the 28th, it’s passing the Pleiades again; and on the 31st, it moves by M35 one more time. (See the Sky Roundup Almanac.)
In other months, passing the same star clusters would not usually happen with the Moon in the same month, but this is a long month and the Moon is full near the start of the month and at the end of the month; so, we have two Full Moons this December. Popularly (though for reasons not clear-cut), this second Full Moon is known as a “Blue Moon”, though it’s unlikely to appear blue in hue. The Moon also finishes out the year in a partial lunar eclipse on New Year’s Eve, though we in the Midwest will not see it to welcome in the New Year.
But we do welcome the astronomical start of the coldest season in the Northern Hemisphere with the Winter Solstice on the 21st.
Here’s wishing you clear skies, a very Merry Christmas, and a Happy New Year!
Sky Roundup Almanac for Dec. 2009
December 1:
Moon less than ⅛º from the Pleiades
December 2:
Full Moon
December 3:
Moon just past Full glides north of M35
December 6:
Waning gibbous Moon 5º north of Mars
December 8:
Last Quarter Moon
December 10:
Saturn 8º north of Moon
December 13:
Geminid meteors at their peak
December 16:
New Moon
December 18:
Mercury at greatest eastern elongation, 1½º south of waxing crescent Moon
December 19:
Jupiter just over ½º south of Neptune
December 20:
Double shadow transit on Jupiter (by 7:30 p.m.)
December 21:
Winter Solstice (when the season starts at 11:47 a.m.) on this date); Jupiter 4º south of Moon
December 24:
First Quarter Moon
December 28:
Moon less than ⅛º from the Pleiades again
December 31:
Moon just before Full glides north of M35 again; Full Moon (“Blue Moon”)
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Sky Roundup for November 2009
Astronomical highlights for the month of November
Give Thanks for the Planets
The month of November marks our national holiday of Thanksgiving and the start of a headlong seasonal plunge toward Christmas. Of course there is much to be thankful for in the night sky this month as well. The visible planets of the Solar System are set to give us some of our better views, if the unsettled, blustery weather of November permits us to see them.
Mercury, the closest planet to the Sun, can often be tough to spot either before or after sunset, since it appears so close to the Sun. Most of the month the little hot world remains in the glare of the Sun, invisible from our vantage on Earth. By month’s end after sunset, it becomes barely visible as a pinkish dot, close to the horizon, in the evening sky. (See Chart 1, which shows how close Mercury is to the horizon in early evening twilight. The planet itself is just next to the “M” in the “Mercury” label. Lines of nearby constellations are shown for reference.)
Venus shines with its characteristic brilliance in morning twilight as it appears to gradually approach the Sun through the month. Shrouded with clouds, the planet reflects much of the Sun’s light into outer space, making it a gem of a showpiece to glimpse with a binocular or telescope from our earthly vantage. (See Chart 2.)
Mars puts in a sparkling cameo appearance in the Beehive Cluster, aka M44, near the first of this month and remains in Cancer (the Crab) all month long. Orangish red at modest magnification, Mars is joined by the Moon on the night of November 9th. (See Chart 3, which shows a binocular close-up of Mars and M44, also known as the Praesepe.)
Jupiter glows brightly all night long as it transits by mid-month. This means that the planet is due south at sunset and is visible till around midnight. (See Chart 4.) Another kind of transit, that is, of two of Jupiter’s moons, will occur across the face of the Solar System’s largest planet on November 6th, though this particular apparition happens during daylight for us. At any other time when both a shadow transit and Jupiter are visible at night, relatively high magnification in a modest telescope is necessary to see this well. (For example, a refracting telescope of 96-millimeter aperture, set to a power of 100 times, is sufficient to see a shadow transit.)
Saturn emerges from the glare of the Sun for serious observation in morning twilight all this month. Recall that the Ringed Planet showed less and less of its rings all last Summer in evening twilight and finally disappeared behind the Sun by the start of Autumn. The planet has re-appeared in our pre-dawn sky and by mid-month shows a slight inclination of its rings when viewed through a telescope. (See Chart 5 for Saturn’s location in the constellation Virgo.)
Though of course not a star or a planet, the Moon sidles past a star cluster and the visible outer planets during November. On the 4th, the waxing gibbous Moon grazes the Pleiades, aka M45. (See Chart 6 for a binocular view of this apparition, showing the Pleiades to the right of Moon after midnight.) The Moon also slips past Mars on the 6th, Saturn on the 12th, and Jupiter on the 23rd.
It’s a pleasing sight to see the planets throughout the month. Give thanks that we can observe them with whatever optical aid we can employ. Be certain to check the times in the Sky Roundup Almanac for when to see our planetary neighbors best. And while you’re checking the time, be certain set your clock back an hour as November 1st marks the end of Daylight Saving Time. Give thanks, too, for that extra hour of sleep.
Sky Roundup Almanac for Nov. 2009
November 1:
Daylight Saving Time ends; Mars only 0.05º from the
Beehive Cluster, aka M44
November 2:
New Moon
November 4:
Waning gibbous Moon glides south the Pleiades, aka M45
November 6:
Double shadow transit on Jupiter
November 9:
Last Quarter Moon; Mars 3º north of Moon
November 12:
Peak of the North Taurid meteors; Saturn 8º north of Moon
November 16:
New Moon
November 17:
Peak of the Leonid meteors
November 23:
Jupiter 4º south of Moon
November 24:
First Quarter Moon
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Sky Roundup for October 2009
Astronomical highlights for the month of October
October Nights, Autumn Lights
The month of October heralds the arrival of our favorite Autumn constellations and a pre-dawn parade of planets. Mighty Pegasus (the Winged Horse) flies across the Fall heavens, followed by Andromeda (the Woman Chained) and Perseus (the Champion).
Pegasus harbors several interesting deep-sky objects, including a nice globular cluster, aka M15, near the horse’s nose, for a good look with a telescope. In next-door Andromeda an edge-on galaxy, NGC 891, typically a difficult object to spot, can be glimpsed near the star Almach, one of the “legs” of the female Andromeda.
Less difficult to spot in Triangulum is the face-on galaxy M33, though still low in overall surface brightness, just above its brightest star at the apex of the star pattern’s triangular shape. Also not to be missed is the nighttime showpiece M31, the Andromeda Galaxy, on a general line up from M33 through the star Mirach in Andromeda. Use low magnification or a solid binocular on a tripod to savor these Autumn lights. (See Chart 1.)
Nearby one can see the fine naked-eye Double Cluster (aka NGC 869 and NGC 864) in Perseus; in a telescope at modest magnification with a wide-angle eyepiece, this celestial sight is another showpiece in Autumn. On an arc of stars from the Double Cluster down through Perseus, one ends up at another naked-eye cluster, the Pleiades, or M45, in the shoulder of Taurus (the Bull). This is also a fine sight, best seen at a telescope’s low power or with a good binocular. (See Chart 1).
Mighty Orion, typically a Winter constellation, rises earlier and earlier in the evening and becomes well-placed before dawn to see its bright stars Rigel and Betelguese. Two distinct stars, blue-white Rigel gleams as Orion’s knee as orange-red Betelguese shines as Orion’s shoulder. (See Chart 2.)
Of course, it is ritual among serious stargazers to observe in Autumn the Great Nebula in Orion, aka M42, the filmy gas cloud surrounding an asterism of young stars known as the Trapezium. This great stellar cloud, along with over a hundred other celestial objects, were first catalogued by the Parisian astronomer Charles Messier in the late 1700’s as a guide to deep-sky wonders that were not to be mistaken for comets in the Solar System. (See Chart 3.)
Autumn is a fine season to catch “Messier objects” heading to the west that have been visible all Summer, such as the globular clusters M13 and M92 in Hercules, and, to get a sneak preview of coming attractions rising in the east in time for Winter, such as M42 in Orion and M44, the Beehive Cluster, in Cancer (the Crab).
On October 6th, our Solar System’s smallest planet, Mercury, jumps out in front of a planetary parade with a quick brightening in the eastern sky as it achieves greatest western elongation, or, its greatest angle west of the Sun before dawn as seen from our vantage on Earth. Look for it just above the eastern horizon before sunup as this is likely to be the best apparition of the little planet this month.
On October 9th, that same small, hot world teems with distant, cold Saturn, which has just emerged from the glare of the Sun as we view it from Earth. (See Chart 4.) In recent months, Saturn’s rings appeared slimmer and slimmer, as we on Earth approached the ring plane of that faraway planet. Now the northern hemisphere of Saturn is tilted slightly toward us, so we will see its rings tilted more and more open over the next several years. Another ring-plane crossing will not be visible here for about another 15 years.
Mars and the waning Moon are not to be left out of the pre-dawn parade as they pair high in the southeast before dawn on October 12th. (See Chart 5.)
Nearby the morning planets is brilliant Venus, which stands above Mercury and Saturn throughout the first half of the month. Saturn also pairs with Venus on October 13th, which ought to make for a striking sight in the field of view through a modest telescope at moderate magnification, as one can view pale yellow Saturn with its rings in spiky profile next to bright white crescent Venus. Both Saturn and Venus dance in morning twilight for the next several days and are joined by the waning crescent Moon on October 15th, while Mercury rapidly drops out of sight by mid-month. (See Chart 6.)
Among the early morning lights of October, one may have the chance to witness a fairly rare phenomenon, known as the Zodiacal light. Not an atmospheric apparition, the Zodiacal light is the faint reflection of sunlight from dust grains along the plane of Earth’s orbit.
Since the plane of Earth’s orbit, as we see it from Earth, is represented by a great circle across the sky known as the ecliptic, this faint glow appears to extend up from the horizon and through Zodiac constellations. This is a seasonal occurrence, which can be best viewed for about two weeks after evening twilight in Spring and for about two weeks before morning twilight in Autumn. But one must have dark skies well away from city lights to see this phenomenon at all.
The Zodiacal light is certainly a rarity for city dwellers and suburban denizens alike. One really must live in, or venture to, the countryside to experience this Autumn delight first-hand. Look to the east on a clear morning well before twilight begins to get a glimpse of this wedge of light known as the “false dawn”.
Far more ephemeral than the familiar planets in morning twilight, one ought to look for morning meteors as well. The occasional, sporadic meteor is often a surprising and welcome treat to see when observing, but staying up late or rising early for a meteor shower can be even more rewarding.
The Draconid meteor shower and the Orionid meteor shower just might be worth losing some sleep to go outside and view, especially since both coincide with times of the month when the Moon will be largely absent from the night sky.
Named for the constellations out of which the meteors appear to emanate, the Draconids peak in the wee hours of October 8th while the Orionids peak on October 21st before sunrise. The radiant for the earlier shower is largely circumpolar, favoring Draco (the Dragon); the radiant for the later shower lies between Orion (the Hunter) and Gemini (the Twins). The former appear relatively slow-moving; the latter often appear as fast ones, which can leave a long smoky trail across the sky.
Certainly a cold nip in the air will greet October observers when you step out this month for some casual stargazing. Attempting to observe on a frigid evening or in brisk morning twilight, you’ll probably want to go right back inside to a warm bed. But if you plan your moments at night to view clusters, galaxies, and nebulae, or to pinpoint the planets and glimpse shooting stars before dawn, you’ve done well to view some true Autumn lights.
Sky Roundup Almanac for Oct. 2009
October 4:
Full Moon
October 5:
Mercury at greatest western elongation
October 7:
Waning gibbous Moon glides past the Pleiades, aka M45
October 9:
Mercury within ½º of Saturn; peak of Draconid meteors
October 11:
Last Quarter Moon; Mars less than 2º north of Moon
October 13:
Venus less than 1º south of Saturn
October 15:
Zodiacal light visible before morning twilight for next two weeks
October 18:
New Moon
October 21:
Peak of Orionid meteors
October 25:
First Quarter Moon
October 27:
Jupiter 3º south of Moon
October 30:
Double shadow transit on Jupiter
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Sky Roundup for September 2009
Astronomical highlights for the month of September
September Skies, Time Flies
The month of September is already upon us. Where’d the Summer go? The Labor Day holiday in September usually signals the unofficial end of Summer as neighborhoods get in one last backyard barbecue, families head to the great outdoors for a quick campout, friends make time for a road trip, and students head back to school. Indeed, the astronomical start of Summer just happened last June, and already we’re headed toward the Autumnal Equinox on the 21st.
Not to be hurried along, though, the night sky has behaved as expected and familiar Fall constellations are slowing rising to replace our summertime romances with the stars. Cygnus (the Swan) flies high overhead before midnight and beats its wings westward for the rest of the month. Mighty Pegasus (the Winged Horse) has been on the rise for the last month and becomes more prominently placed in the northeast, flying across the heavens all night long. (See Chart 1.)
Also biding its time in the sky is the bright planet Jupiter, poised in the southeast by dusk. Its majestic march through the sky continues from its opposition last month, as the largest planet in the Solar System will be visible till dawn all this month. It dallies with the Moon early in the month and also treats us to an oddity not normally seen. On September 2nd, Jupiter will appear moonless!
Usually flanked by the satellites made famous by Galileo’s observations 400 hundred years ago, the four largest moons of Jupiter, namely, Io, Europa, Ganymede, and Callisto, will not appear to flank that kingly world on the night of the 2nd-3rd. Instead, the big moons will either be in front of or behind the big planet; so, Jupiter will have no visible Galilean satellites for several hours (from about 11:00 p.m. till about 1:00 a.m., CDT) that night. That’s a narrow window of observation which will fly by before you know it; the next opportunity for this apparition won’t come again until the year 2019. (See Chart 2, for a telescopic view of Jupiter without visible moons.)
Several planets spend time near the Moon this month, which will make for time well spent in observing them. Big Jupiter shines within several degrees of the waxing gibbous Moon on the 2nd and 3rd, and then less so by the 4th, when the Moon goes full. Mars is clipped by the Moon on the 13th and occults the Red Planet, but only for those in northern climes. By mid-month, brilliant Venus pulls within a few degrees of the waning crescent Moon before sunrise on the 16th. (See Chart 3 for a pleasing apparition of Jupiter and the nearly Full Moon in the evening, Chart 4 for the Moon and Mars before dawn, and Chart 5 for Venus and the Moon in morning twilight.)
While the planets attend the Moon this month, the showstopper for the last several months, Saturn, has now disappeared into the glare of the Sun. Its slimming rings were a treat to see for many observers at summertime star parties, but now that time has passed. The apparition of a ringless Saturn won’t return again for 15 years.
Certain bright stars do not escape attention without a couple of planets and the Moon sidling up to them to pass the time. In the morning sky on the 2nd, Venus appears within a couple of degrees of the Beehive Cluster (aka M44) and then within a degree of the star Regulus in Leo (the Lion) on the 20th, while the Moon marches past the Pleiades (aka M45) on the 10th and around the star Antares in Sagittarius (the Archer) on the 24th. These particular apparitions, except for the last one, are all visible above the eastern horizon during morning twilight, so don’t waste time slumbering too soundly. (See Chart 6, for a view of Venus next to Regulus, which ought to be a neat sight through a telescope.)
As with any observation at an odd hour, one has to convince oneself that sleep is overrated. If you don’t observe September skies late at night, in morning’s wee hours, or just before sunup, the best parts of the month slip away!
Sky Roundup Almanac for Sept. 2009
September 2:
No Galilean moons seen flanking Jupiter; Venus 1.5º south of Beehive Cluster, aka M44
September 4:
Full Moon
September 10:
Moon about ½º north of Pleiades, aka M45
September 11:
Last Quarter
September 13:
Mars just over 1º south of waning crescent Moon
September 16:
Venus within 3º of Moon
September 17:
Uranus at opposition
September 18:
New Moon
September 20:
Venus ½º north of Regulus
September 22:
Autumnal Equinox at 21:19 Universal Time, 4:19 p.m., CDT
September 24:
Antares less than 1º south of Moon (no occultation seen)
September 25:
First Quarter Moon
September 29:
Jupiter at 3º south of Moon
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Sky Roundup for August 2009
Astronomical highlights for the month of August
Celestial Crossings
The month of August crosses into familiar territory for most sky observers. It is during this month that we look for the Sun crossing high toward the South, the Full Moon crossing low over the trees, Perseid meteors crossing the sky from the northeast, and the first of our best known Winter stars cross the horizon into morning twilight before sunrise.
The Sun we see not at its highest, but feel it at its hottest during this time of the year. It is the expected seasonal lag in temperature that we experience in August. Though the Sun was highest in our sky at the Summer Solstice in June and delivered its greatest amount of sunlight to us in the Northern Hemisphere, the effect of that sunlight heating the Earth is not felt fully until late July through early August. Often we call these days the “dog days” of Summer. When the weather is hot and sultry, we tend to imitate our canine friends and simply content ourselves to lie around and wait for a break in the heat.
Too, stars that we anticipate seeing in our evening Winter sky peep into morning twilight and rise earlier and earlier through the approaching Autumn season. For example, Sirius makes itself barely seen at the horizon as it rises just ahead of Sun on August 4th. This is an heliacal rising, when a star rises with the Sun, which often heralded important changes in an ancient calendar or told our forebears they were crossing into a new season.
For those in ancient Egypt, the sighting of Sirius, as the goddess Isis, portended her watch over the seasonal flooding of the Nile River. In our modern world, Sirius, the brightest star of Canis Major (the Larger Dog), is known as the Dog Star, for which we name the “dog days” of Summer when that star rises during that hot time of August.
The Moon glides low across the southern sky as its position in its orbit mimics the path of the Sun in Winter. The Moon’s orbit is tilted with respect to Earth’s orbit and the apparent path of the Sun across our sky, known as the ecliptic. When the Sun appears high in our sky, as it typically does in Summer, we see the Moon low in that same Summer sky, in about the same part of the sky one will see the Sun in Winter.
In addition, the Moon becomes a part of a subtle show as Earth crosses between it and the Sun. On August 5th, the Moon will barely cross into Earth’s outer shadow in outer space. This is known as a penumbral eclipse. If the Moon were more fully immersed in that shadow, we would witness a partial or perhaps a total lunar eclipse. But the crossing is minimal, so Earth’s shadow on the Moon is barely perceptible. For us in the Midwest, this particular eclipse will occur at moonrise and will not be visible to the eye.
The most dramatic celestial crossing this month is the eagerly anticipated Perseid meteor shower. At mid-August every year, serious observers and casual stargazers look to the skies after sunset to witness one of Nature’s finer displays. Seeing streaks of light across the night sky still awe and enthuse, and many municipalities attempt to accommodate the observation with late hours at local parks for folks to bring lawn chairs and unfurl blankets to watch the spectacle.
Peaking every year on August 12th, the Perseids offer the best summertime, naked-eye observing, especially since they occasionally produce bright meteors, known as fireballs. To watch this fine display, simply sit back or lie back and look up. Scan around and see how many you can catch at first glance. Most of the meteors appear to emanate from the northeast, that is, from the constellation Perseus, hence the name for the meteor shower.
This year Nature cooperates as the Moon, nearing Last Quarter, rises late, so a number of faint meteors every hour may be visible before the light of the Moon appears in the sky. As Perseus itself also does not rise until after midnight, one can likely see many meteors before moonrise.
The Moon makes its own celestial crossing in August as well. The Moon will cross between the Earth and the orangish star Antares, the brightest distant sun in the constellation of Scorpius (the Scorpion). We saw this apparition, known as an occultation, last June, when the Moon passed in front of that bright star. This will happen again on August 27th. (See Chart 1.)
The Earth also crosses between two distant planets this month. When that happens, the planets themselves are at their best viewing from our vantage. That celestial crossing, known as opposition, is when Earth in its orbit crosses between the Sun and a planet. In August, the planets in opposition are Jupiter and Neptune! This means that these planets are seen rising as the Sun is setting; in other words, they are seen opposite the Sun in the sky, hence the name of this apparition. On August 14th, Jupiter stands opposite the Sun; on August 17th, it is Neptune’s turn. Both will require telescopes to see them best.
More subtle to see is the crossing of Jupiter’s moons across its disk. Such a celestial crossing is called a transit. In several instances this month, though, it is the shadow of moons one can see with a telescope aimed at Jupiter. Requiring a firmly mounted telescope and a modicum of patience, one can witness at fairly high magnification the telltale presence of Jovian moons crossing the bright face of the planet itself.
The moons themselves one will not see across the disk of Jupiter, but their shadows cast onto the planet’s thick, gassy atmosphere. In fact, two moons at a time will make the crossing, so one has the prospect to witness a double shadow transit! See the Sky Roundup Almanac for dates and approximate times for these crossings.
Rarer still is the showpiece of one of our distant planets on a clear evening this month. Through a telescope, pale yellow Saturn can be glimpsed in early evening twilight with an uncommon look about it. Best known for its bright rings, Saturn will now appear nearly ringless! For the last several months, Earth has approached that point in its orbit that coincides with the ring plane of that distant world. This occurs about every 15 years, and it allows us the vantage of seeing Saturn as if had no rings around it.
Though the actual ring-plane crossing will not occur until early September, Saturn itself will be lost in the glare of the Sun by that time. So, the first half of this month of August will be the best (and last) time to see Saturn’s rings nearly edge-on. You won’t have another chance to see such a celestial crossing for another 15 years after this month. (See Charts 2a and 2b; Note the edge-on rings and a labeled sampling of the moons’ placement in early August.)
Quite a number of fine sights to see this month. And all you have to do to see them is cross the threshold and go outside.
Sky Roundup Almanac for August 2009
August 5:
Full Moon; penumbral lunar eclipse at moonrise, barely perceptible; Jupiter 3º south of Moon
August 12:
Peak of Perseid meteor shower; double shadow transit on Jupiter
August 13:
Last Quarter Moon
August 14:
Jupiter at opposition; Moon about ½º north of Pleiades, aka M45
August 17:
Venus (before dawn) less than 2º south of waning crescent Moon; Neptune at opposition
August 19:
Double shadow transit on Jupiter
August 20:
New Moon
August 22:
Saturn 7º north of Moon (look for its slim rings!)
August 24:
Mercury at greatest elongation (at 27º east of the Sun, seen in the western sky in twilight after sunset)
August 26:
Double shadow transit on Jupiter
August 27:
First Quarter Moon; Antares less than 1º south of Moon, occultation
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All almanac events corrected to Central Daylight Time (when in force from March to November) and to Central Standard Time (when in force from November to March), as necessary.
If you'd like to check past editions of Sky Roundup, click here for access to archives kept by the Cleveland Museum of Natural History, where Roy Kaelin headed up its Astronomy Department from 2007 to 2009.
Comments or questions? Please contact Roy Kaelin at roy@roykaelin.com.
