Go Stargazing! August Edition

Saturn is the only planet visible to the naked eye at night this August.  Face southwest at dusk and you’ll see Saturn near a star of similar brightness—Spica in Virgo.  Saturn is a bit to the right of Spica as you face southwest.   The ringed planet remains well placed for evening viewing and remains in the night sky until late September 2011.

Hubble Images Suggest Rogue Asteroid Smacked Jupiter
Creative Commons License photo credit: NASA Goddard Photo and Video

Mars and Jupiter are in the pre-dawn sky.  Jupiter, set against a background of very dim stars, dominates the southeastern pre-dawn sky and is due south at dawn by the end of the month.  Mars is dimmer and much lower in the east northeast.  It has fully emerged from the sun’s glare and will brighten slightly each morning. Venus is now out of sight.  Superior conjunction (alignment on the far side of the sun) is on August 16.

The Big Dipper is to the left of the North Star, with its handle pointing up.  From that handle, you can ‘arc to Arcturus’ and then ‘speed on to Spica’; those stars are in the west and southwest at dusk.  Antares, brightest star of Scorpius, the Scorpion, is in the south, with the ‘teapot’ of Sagittarius to its left.  Meanwhile, the Summer Triangle is approaching the zenith.  The stars of summer now dominate the evening sky.  In late evening, you can watch the Great Square of Pegasus rise in the east.

Moon Phases in August 2011:

1st Quarter                     August 6, 6:08 a.m.

Full Moon                       August 13, 1:57 p.m.

Last Quarter                  August 21, 4:56 a.m.

New Moon                      August 28, 10:03 p.m.

The annual Perseid Meteor Shower peaks this year on Saturday morning, August 13.  Unfortunately, the moon (full on the 13th) hides all but the very brightest meteors and thus spoils the show.  If you want to see just how many Perseids can outshine the moonlight, the best hours are from roughly 2 a.m. to dawn.

Go Stargazing! December Edition

Jupiter dominates this month’s evening skies.  It outshines all stars in the sky, so it’s easy to find.  Face south at dusk and look for the brightest thing there.

Mercury has emerged into the evening sky, and is visible at the beginning of this month.  Look low in the southwest at dusk, right over the point of sunset.  By mid-month, Mercury is again lost in the Sun’s glare; it re-aligns with the sun (is at inferior conjunction) on Dec. 19.

Venus remains a dazzling morning star.  Face southeast at dawn, and you can’t miss it.

Saturn is in the southeast at dawn, above the much brighter Venus.

mars-06-crop
Creative Commons License photo credit: chipdatajeffb

Mars is now lost in the sun’s glare; it will remain invisible to us all winter as Earth passes around the far side of the sun from it.

Look for the enormous Summer Triangle in the night sky, consisting of the stars Deneb, Vega, and Altair, in the west.  These stars were up all night long back in June and July, hence the name. The Great Square of Pegasus, not quite as bright as the Summer Triangle, is high in the south at dusk.  The star in its upper left hand corner is also the head of Andromeda.  Rising after Andromeda is Perseus, the hero that saved her life.  Facing north, you’ll see five stars in a distinct ‘M’ like shape—this is Cassiopeia, the Queen.  Her stars are about as bright as those in the Big Dipper, and she is directly across the North Star from that Dipper.  Taurus, the Bull rises in the northeast.  Look for the Pleiades star cluster at the feet of Perseus.  Dazzling Orion, the Hunter rises shortly after dusk (by month’s end, it is already up at dusk).  As Orion enters the evening sky, we transition from the relatively dim evening skies of autumn to the brilliant stars of winter.

Moon Phases in December 2010:

New Moon                             December 5, 11:36 a.m.

1st Quarter                            December 13, 7:58 a.m.

Full Moon                              December 21, 2:14 a.m.

Last Quarter                         December 27, 10:19 p.m.

Eclipse burning bright
Creative Commons License photo credit: ericskiff

The full moon of early Tuesday, December 21, enters the Earth’s shadow, causing a total lunar eclipse.  This eclipse is visible in its entirety from all of North America, including Houston.  The moon first encounters the Earth’s shadow (umbra) at 12:32 a.m.  This marks the beginning of the partial eclipse.  The moon takes just over an hour, until 1:40 a.m., to enter the shadow.  That is when totality begins.  In this eclipse, the Moon does not quite cross the center of Earth’s shadow but instead passes through the northern part of it.  Even so, the moon takes 74 minutes to cross to the other side of the shadow, so totality lasts from 1:40 to 2:54 a.m.  By 4:02 a.m., the moon has re-emerged from the shadow, and the eclipse is over.  Remember, seeing a lunar eclipse requires no special equipment at all; anyone who sees the moon sees the eclipse.  The only thing that could stop us from seeing this would be a cloudy night on December 20-21, 2010.  The next total lunar eclipse we see here in Houston occurs just after midnight on April 15, 2014.

At 5:42 p.m. on Tuesday, December 21, the sun is overhead at the Tropic of Capricorn, the most southerly latitude where the sun can be overhead.  This is therefore the winter solstice for those of us in the Northern Hemisphere, and the summer solstice for people south of the equator.

At Houston’s latitude, the earliest sunset of the year occurs Thursday, December 2.  Of course, days continue to shorten until the solstice, which makes sunset earlier and sunrise later.  However, Earth is also accelerating as it approaches perihelion (closest approach to the sun) in early January.  This causes sunrise, local noon, and sunset to occur slightly later each day.  This close to the solstice, the second effect actually predominates, so sunset gets a little later during December even while the days are getting shorter.  As you head out to ring in the New Year, notice that sunset on New Year’s Eve is about 10 minutes later than it is now.

2009 Leonid Meteor (cropped, afterglow closeup)
Creative Commons License photo credit: Navicore

The Geminid meteor shower peaks every year in mid-December, this year on the 14.  This shower and the Perseids in August are the two most reliable showers of the year, producing about 1 or two meteors per minute.  The Geminids are not as popular, though, because of colder nights (yes, sometimes even in Houston) and a greater chance of cloudy skies.  Still, it’s worth a look if the skies are clear.  Unlike most meteor showers which are comet debris, the Geminids originate from an asteroid (3200 Phaethon.  The shallower angle between this debris path and Earth’s orbit means that Earth rotates us towards the debris field before midnight.  We can thus observe meteors from late evening all the way until dawn.  Meteors will seem to radiate from the constellation Gemini, hence the shower’s name.

Go Stargazing! August Edition

This month the great planet race continues, as Venus, Mars and Saturn form a triangle in the west.  Watch the triangle change shape each night as Venus overtakes Saturn and then Mars!

Venus is by far the brightest of the three planets.  Face west at dusk and look for a point of light that outshines everything in the night sky.

Saturn and Mars are to the upper left of Venus as August opens.  Mars is below Saturn and a bit to its left.  Although these two planets of similar brightness are much dimmer than Venus, they outshine all the other stars near them.

Observe all three carefully throughout August and watch as their configuration changes.  Mars aligned with Saturn last Saturday (July 31) and now begins to move farther to Saturn’s left.  Venus, moving faster than the other two, continues to approach from the right; it will pass Saturn on August 8.  Venus then continues to gain on Mars as they both move away from Saturn.  Venus finally overtakes Mars on August 19-20.  On the night of August 31, Venus and Mars are to either side of the star Spica in Virgo.

Jupiter is now a late evening object, rising by 11 p.m now and by 8:45 p.m. at month’s end.  It outshines all stars in the sky, so it’s easy to find.  Face east in late evening or south southwest at dawn to see it.

The Big Dipper is in the northwest at dusk. You can extend the curve of its handle to ‘arc to Arcturus’ and then ‘speed on to Spica’.  These stars are in the west at dusk tonight.  Arcturus, by the way, is the fourth brightest star we ever see at night, but the brightest one Americans ever see on an August evening.  Spica is in Virgo, the constellation where this month’s ‘planet race’ occurs.

In the east, look for the enormous Summer Triangle, consisting of the stars Deneb, Vega, and Altair.   This triangle is up all night long from June to early August, hence its name.  Scorpius, the Scorpion, is in the south at dusk.  Sagittarius, the Archer, known for its ‘teapot’ asterism, is to its left.  Between these two star patterns is the center of our Milky Way—the brightest part of that band as wee see it.  On a cloudless night far from the big city, see if you notice the Milky Way glow near the ‘teapot’ of Sagittarius.  In late evening, look for the Great Square of Pegasus rising in the east.

Moon Phases in August 2010:

Last Quarter                        August 3, 12:00 a.m.

New Moon                              August 9, 10:08 p.m.

1st Quarter                           August 16, 1:14 p.m.

Full Moon                              August 24, 12:05 p.m.

Perseid Meteor 8/12/08
Creative Commons License photo credit: aresauburn™

On Friday morning, August 13, the Earth passes through a stream of debris left long ago by Comet Swift-Tuttle.  This produces the Perseid Meteor Shower, one of the best meteor showers each year.   The Perseids occur every year at about this time, producing on average about one meteor per minute.  Keep in mind that even a short period such as a minute can seem longer if you are waiting for something to happen.  Since Earth is running into the meteors, not the other way around, the leading edge of the Earth encounters the shower.  This is the side going from night into day.  Accordingly, we see more meteors as dawn approaches.  Big city lights or the Moon can limit the meteors you see by dimming out fainter ones.  This August, however, the New Moon is on the 10th, giving us a skinny crescent on the 12th which sets long before the shower really gets going.  The main challenge, then, is to avoid city lights.

If skies that night are clear, our George Observatory will open Thursday night, August 12 at 9pm and remain open until dawn for observing the shower.  If you come out to George or go elsewhere, you’ll want to lie on your back (to see as much of the sky as at once as possible) and orient yourself towards the constellation Perseus.  (The shower is called the ‘Perseids’ because they seem to radiate from that constellation.)  Perseus rises in the northeast at dusk and is high in the north at dawn.

Leonids Meteor Shower Tonight!

Don’t miss out on your chance to see the Leonids meteor shower, tonight and early tomorrow morning. It won’t be as strong as the yearly December Geminids or August Perseid meteor showers. However, the Leonids meteor shower could produce as many as 500 meteorites in an hour during its peak, which will be in Tuesday’s early predawn hours.

Perseid Meteor 8.12.09
Creative Commons License photo credit:
aresauburn™

The Leonids will be less frequent and appear weaker this year than at the turn of the century. This is because from 1999 to 2002, the Earth was moving through a clump of debris left by comet Tempel-Tuttle. In those years the Leonids were strong enough to be considered a storm (over 1,000 meteorites per hour).

Now Tempel-Tuttle has receded from the Sun, taking its main debris clumps with it.  Therefore, the Leonid showers aren’t as dramatic anymore, typically averaging only about one every few minutes.  The 2009 Leonids are expected to be stronger than usual, but not nearly as good as at the beginning of the decade.  Although they may be few in number, many Leonid meteors are quite bright.

The meteors will seem to radiate from the constellation Leo, which will be high in the east (hence the name of the shower).  You’ll see approximately one meteor every 2 or 3 minutes, or fewer if clouds or city lights are present.