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.

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.

Early Risers: You’re In For A Treat! June brings Blazing Comet & Lunar Eclipse

Are you an early riser and up before the crack of dawn?  If so, I encourage you to look up as you pick up that morning paper as there are two special treats in the June 2010 morning sky.

Comet McNaught
Creative Commons License photo credit: c.j.b

In January 2007, a brilliant comet, known as Comet McNaught dazzled observers in the Southern Hemisphere. Houstonians missed out on it, though, because of cloudy weather in our area during the brief time that comet was well placed for us. Now, in 2010, a different comet McNaught is becoming visible in our sky at dawn.

Robert H. McNaught, an astronomer at the Australian National Observatory, discovered this comet on September 9, 2009, using a telescope at Australia’s Sliding Spring Observatory.  McNaught, a prolific discoverer of comets, has discovered 44 comets (including this one) and is a co-discoverer of 12 others, for a total of 56.  This comet’s formal designation is C/2009 R1, where ‘C’ indicates a long period comet and ‘R’ indicates the time of year it was discovered.

Comet McNaught, though, is more than a ‘long-period’ comet.  Astronomers have determined that its eccentricity is greater than 1, meaning that its orbit has the shape of a hyperbola.  A hyperbolic orbit is the trajectory of a comet that passes near the sun once and never returns.  Once McNaught recedes from view, we’ll never see it again.

A hyperbolic orbit also means that McNaught has never been in the inner solar system before.  This challenges astronomers who want to predict how it will behave and just how bright it will become in our skies.  Already, McNaught is brighter than expected; many expect McNaught to become a naked-eye object by month’s end, especially for those able to observe at a dark site far from light pollution.  McNaught is now easily observable in binoculars.

This is a chart from Sky and Telescope, showing the path of Comet McNaught against the background stars.  Keep in mind that in June, the stars in this map rise in the northeast just before dawn.  McNaught continues to approach the sun until reaching perihelion on July 2, so we expect it to brighten until that date.  Unfortunately, a comet near perihelion is generally also close to the sun in our sky, and this comet is no exception.  Therefore, McNaught will also get harder to see as it brightens towards the end of the month.   After perihelion, McNaught is poorly placed for observers in the Northern Hemisphere.

17-08-2008 lunar eclipes
Creative Commons License photo credit: emrank

If you’re looking for the comet on Saturday morning, June 26, you might as well turn around and watch the moon set in partial eclipse.  Since the Moon is not precisely aligned with the Earth this time, it will not enter fully into the Earth’s shadow; it goes a little less than halfway in instead.  Still, from 5:17 a.m. until moonset at 6:25 a.m., you’ll notice a chunk of the moon’s upper right side missing.  (Actually, its the northern limb of the Moon that passes through the shadow.  The Moon’s northern limb is on the right as the Moon sets.)  The Moon is only about 10 degrees high when the eclipse starts, so you’ll need a southwest horizon clear of tall trees and buildings.  Note that the eclipse is still in progress at moonset; we will see less than half of it.  Folks far to our west will see a much longer event.

Go Stargazing! June Edition

Size comparison of terrestrial planets (left to right):
Mercury, Venus, Earth, and Mars

Saturn is now in the south southwest at dusk.  Look just to the west of due south, about 2/3 of the way up from the horizon to the zenith, and you will see Saturn in the sky.

Venus remains high in the evening sky during June.  Face west at dusk and look for a point of light that outshines everything in the sky but the sun and the moon.

Mars is high in the evening sky, although not as bright as it was in winter.  Since January 29, Earth has been pulling ahead of Mars on its faster orbit.  As a result, Mars gets slightly dimmer each night for the rest of 2010.  As June opens, Mars is approaching the star Regulus in Leo from the right.  Mars is right next to the star on June 5, then pulls away from the star to the left after that.  Look high in the west at dusk for a reddish point of light.

Jupiter is in the south-southeast at dawn this month.  It outshines all stars in the sky, so it’s easy to find.

Spring stars are high in the south and west.  A distinct backwards question mark shape outlines the mane and forepaws of Leo, the Lion.  Three stars forming a right triangle are to its upper left; they mark Leo’s hindquarters.  The Big Dipper is as high as it ever gets in the north at dusk. You can extend the curve of its handle to ‘arc to Arcturus’ and then ‘speed on to Spica.’  These stars high in the east and south, respectively, by dusk tonight.  Arcturus, by the way, is the fourth brightest star we ever see at night, but the brightest one Americans ever see in all of June and July.

In the east, look for the enormous Summer Triangle, consisting of the stars Deneb, Vega, and Altair.   This triangle is up all night long in June and July, hence its name.  Scorpius, the Scorpion, is in the southeast at dusk.  Sagittarius, the Archer, known for its ‘teapot’ asterism, rises just after dusk on June 1, but is up by nightfall on June 30.

Moon Phases in June 2010:

Last Quarter                  June 4, 5:13 p.m.

New Moon                      June 12, 6:14 a.m.

First Quarter                  June 18, 11:30 p.m.

Full Moon                        June 26, 6:30 a.m.

It's ba-ack!
Creative Commons License photo credit: ronnie44052

The full moon of Saturday, June 26, will set in partial eclipse.  At 3:55 a.m., the moon first touches the penumbra of the Earth, the region where Earth partially blocks the sun.  The main event starts at 5:16 a.m., when the moon begins to enter the umbra, or the shadow itself.  The moon is not truly aligned with the Earth and sun this time, though, so it will not go all the way into the shadow.  This is why we have only a partial eclipse, with only the north (upper) limb of the moon in shadow.  The moon is still partly inside the umbra as it sets at 6:25 a.m.  (Although we no longer see it, the moon remains partially eclipsed until 8 a.m.)

This eclipse is merely a ‘warm-up’ for the spectacular total lunar eclipse we will have just after midnight on December 21.

At 6:29 a.m. on Monday, June 21, the sun is directly overhead at the Tropic of Cancer. Therefore, this day’s midday sun as high as possible in our skies.  This, then, is the moment of the summer solstice.  Those of us in the Northern Hemisphere enjoy more daylight on this day than on any other day of the year.

Science Doesn’t Sleep (8.14.08)

Granny Smith
Nutritous and delicious.
Creative Commons License photo credit: Steve Navarro

So here’s what went down after you logged off.

For the 2008 Olympians, what’s nutritious and delicious? Powdered apple peel.

Humans and wild elephants in Indonesia have come into repeated conflict over habitat - resulting in property losses for humans and deaths of wild elephants. So, locals have developed a squadron of trained “flying elephants” that patrol the perimeter villages and warn their brethren away.

Insects that dive underwater create an “underwater lung” – an air bubble they carry with them as they swim – in order to breathe. Scientists have just figured out how it works.

Don’t forget to sleep on it: sleep plays a sophisticated role in what we remember – and what we forget.

Geographic profiling: what works for bees also works for serial killers.

Ready the wonderment: the Moon goes into partial eclipse this Saturday night.

Where have all the sea monsters gone? A variety of factors are transforming Earth’s oceans into “simplistic ecosystems dominated by microbes, toxic algal blooms, jellyfish and disease.”