Go Stargazing! July Edition

Saturn is the only planet visible to the naked eye in the evening skies of July, 2011.  Face south-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 evening 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 now higher in the pre-dawn sky.  Jupiter, set against a background of very dim stars, dominates the eastern sky at dawn.  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, as it is passing around the far side of the sun from our perspective.

The Big Dipper is above 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 southwest at dusk.  Leo, the Lion, sets in the west at dusk.

Antares, brightest star of Scorpius, the Scorpion, is in the south, with the ‘teapot’ of Sagittarius rising behind it.  The Summer Triangle has fully risen in the northeast.  The stars of summer now dominate the evening sky.

Moon Phases in July 2011:

New Moon                       July 1, 4:02 p.m.

1st Quarter                     July 8, 9:09 p.m.

Full Moon                        July 15, 3:12 p.m.

Last Quarter                  July 23, 6:48 a.m.

Winter Solstice Lunar Eclipse
Creative Commons License photo credit: Bruce McKay~YSP

The new moon of July 1 partially blocks the sun, but only as seen from the Antarctic.  No one will get to see a total eclipse because the moon’s full shadow, or umbra, passes just below the Earth.

As we celebrate our independence this July 4, Earth will be at aphelion (at its greatest distance from the sun).  The precise time is 10 a.m.  Perihelion, the Earth’s closest approach to the sun, occurs in January.  Earth has perihelion and aphelion because its orbit is not a circle but an ellipse with an eccentricity (out-of-roundness) of about 1.6%.  Such a small variation, however, exerts no significant influence on our seasons, as you can determine for yourself by stepping outside.  The 23.5 degree tilt of Earth’s axis, on the other hand, is a much more dominant effect.  The very high midday sun of July ensures long days and baking heat in Houston and across much of the Northern Hemisphere.

By popular demand, our George Observatory will open to the public Fridays and Saturdays this summer (except July 8, due to a prior booking).  The Discovery Dome, our traveling planetarium, will be set up each of these Fridays to show films throughout the evening.

Go Stargazing! June Edition

Saturn
Creative Commons License photo credit: Elsie esq.

Saturn is the only planet visable to us at night this June.  Face south at dusk, and you’ll see Saturn near a star of similar brightness — Spica in Virgo.  Saturn is significantly higher in the sky than Spica and a bit to its right as you face south.   The ringed planet is now well placed for evening viewing, and remains in the evening sky until late September 2011.

Mars and Jupiter are now higher in the pre-dawn sky.  Jupiter, set against a background of very dim stars, dominates the eastern sky at dawn.  Mars is dimmer and much lower in the east northeast.  It has fully emerged from the sun’s glare, however, and will brighten slightly each morning.  Venus does not rise until morning twilight.  Look for it very low in the east northeast as day breaks.

The Big Dipper is above 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 south at dusk.  Leo the Lion, is high in the west at dusk.

Antares, brightest star of Scorpius, the Scorpion, is in the southeast, with the ‘teapot’ of Sagittarius rising behind it.  The Summer Triangle has fully risen in the northeast.  The stars of summer are here. 

Moon Phases in June 2011:

New Moon                    June 1, 4:02 p.m.

1st Quarter                  June 8, 9:09 p.m. 

Full Moon                     June 15, 3:12 p.m.

Last Quarter               June 23, 6:48 a.m.

Red Light...
Sunset
Creative Commons License photo credit: Kıvanç Niş

The full moon of June 15 passes through the Earth’s shadow, causing a total eclipse of the Moon. Unfortunately, we miss out on that one, too, as the eclipse occurs during our daylight hours.  Anyone in the Eastern Hemisphere, though, can observe a central (and therefore especially long) total eclipse of the moon. 

At 12:17 p.m. on Tuesday, June 21, the sun is directly overhead at the Tropic of Cancer, the farthest point north where this is possible.  This makes the midday sun as high in our sky as possible and gives us more daylight than on any other day of the year.  This moment is, therefore, the summer solstice.  However, the earliest sunrise for us is the morning of June 11 and the latest sunset is on June 30.  Those of us who sleep through sunrise and witness sunset may get the impression that the days are lengthening all the way to the end of the month.

By popular demand, our George Observatory will open to the public not only on Saturdays, but also all Friday nights in June and July (except July 8).  The Discovery Dome, our traveling planetarium, will be set up each of these Fridays to show films throughout the evening.

Go Stargazing! May Edition

Saturn is the only planet in May 2011 evening skies.  Face south southeast at dusk, and you’ll see Saturn near a star of similar brightness— Spica in Virgo.  Saturn is significantly higher in the sky than Spica and a bit to its right as you face south.  Last month, Earth passed between the Sun and Saturn.  That alignment, called opposition, put Saturn in the sky all night long.  The ringed planet is now well placed for evening viewing, and remains in the evening sky until late September 2011.

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

The other four naked eye planets are involved in a very close gathering low in the east at dawn.  You will need a clear view all the way to the east northeastern horizon at daybreak to observe this planet massing.  However, the planets do outshine all stars in this general area. If you’re able to observe any points of light just above the horizon as dawn begins, you’re probably seeing the planets.  As of now, Venus and Mercury rise first, with Mercury about a degree under the brighter Venus.  Mars and Jupiter are a bit to their lower left, with Mars a little to the left of Jupiter.  Mars was less that half a degree above Jupiter on May 1, and is now slowly pulling away from it.  Venus and Mercury are moving faster, so they are closing the gap on Mars and Jupiter.

On the morning of May 11, Venus and Mercury will be aligned with Jupiter, with Venus less than one degree from Jupiter.  This is also when the entire grouping is the most compact, with all four planets within six degrees of one another.  By May 21, Mercury and Venus will have caught up with Mars, with Venus just over a degree from the red planet.  After this, Mercury and Venus pull ahead of Mars and thus go deeper into the sun’s glare.  Mars and Jupiter, left behind, remain in the morning sky all summer.

Star Gazing
Creative Commons License photo credit: jurvetson

A swath of brilliant winter stars sets in the west at dusk this month.  Orion, the Hunter, is still visible in the west as May begins.  His two dogs, represented by Sirius and Procyon, are to his left.  To Orion’s right is Taurus, the Bull, with the star Aldebaran as its eye. Gemini, the Twins, are above Orion.  The Big Dipper is above the North Star, with its handle pointing to the right.  From that handle, you can ‘arc to Arcturus’ and then ‘speed on to Spica;’ those stars are in the east and southeast at dusk.  Leo, the Lion, passes almost overhead in late evening.

As Orion and Taurus set, look for Antares, brightest star of Scorpius, the Scorpion, to rise in the southeast.  At the same time, Vega, brightest star of the Summer Triangle, appears low in the northeast.  These stars remind us that summer is on the way.

Moon Phases in May 2011:

New Moon                              May 3, 1:50 a.m.

1st Quarter                             May 10, 3:32 p.m.

Full Moon                               May 17, 6:07 a.m.

Last Quarter                          May 24, 1:51 p.m.

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.