Stay up late for a great cosmic show: The first eclipse of April 2014 is tonight!

Don’t forget: there’s a lunar eclipse tonight! The eclipse will begin shortly before midnight and continue until 4:30 in the morning on April 15. You’ll be able to see the eclipse from just about everywhere in Houston, but especially well at the George Observatory, where you can watch through telescopes away from city lights.

We’ve been getting a lot of people asking, “What exactly is a lunar eclipse?” Well, a lunar eclipse is when the Moon passes into the Earth’s shadow, or umbra. For this to happen, the Sun, Earth, and Moon have to be perfectly aligned.

For those who have never seen an eclipse, it is quite breathtaking. The Moon will start out full. As it rises, it will reach the edge of the umbra shortly before midnight, where it will begin to disappear. As the Moon continues to rise, it will slowly be engulfed by the Earth’s shadow. Then, as it sets, the Moon will slowly reappear until it is full again (roughly around 4:30 in the morning).

Since this a total eclipse, it can be viewed anywhere in the world that is facing away from the Sun. You can sit outside, even in the city, and view the eclipse yourself.

However, the George Observatory will be open all night to the public tonight. For $5 per person, you can enjoy our three large telescopes. Then, once the eclipse begins, relax on our deck and watch the eclipse with our astronomers. Besides the Moon, Mars will also be visible (we’ve just passed opposition, so tonight’s a really a great chance to see the red planet, as it’s much brighter than usual).

Want to know more about the Moon while you gaze up at it tonight? This great video from Live Science goes through the history of the formation of the Moon and how it got some of its most famous features!

Seeing Stars with James Wooten: Mars and the Moon share the limelight

This star map shows the Houston sky at 10 pm CDT on April 1, 9 pm CDT on April 15, and dusk on April 30.  To use the map, put the direction you are facing at the bottom.  Jupiter is high in the west in Gemini, the Twins. Below them, Dazzling Orion, the Hunter sets with Taurus, the Bull.  To Orion’s left are the two Dog Stars—little dog Procyon and big dog Sirius.  Sirius outshines all other stars we see at night.  The Big Dipper is high in the north. Leo, the Lion, is high in the south. These stars, along with Arcturus, announce the spring.  Mars is up all night long this month.

This star map shows the Houston sky at 10 p.m. CDT on April 1, 9 p.m. CDT on April 15, and dusk on April 30. To use the map, put the direction you are facing at the bottom. Jupiter is high in the west in Gemini the Twins. Below them, Dazzling Orion the Hunter sits with Taurus the Bull. To Orion’s left are the two Dog Stars: little dog Procyon and big dog Sirius. Sirius outshines all other stars we see at night. The Big Dipper is high in the north. Leo the Lion, is high in the south. These stars, along with Arcturus, announce the spring. Mars is up all night long this month.

This month, Jupiter remains well placed for evening observing all spring. Look for it high in the west at dusk.

Mars is up virtually all night long this month. On April 8, Earth passes between the Sun and Mars. This places Mars at opposition, an alignment where we see Mars rise at dusk and set at dawn — Mars is up literally all night long. It turns out that Mars is farther from the Sun than average when Earth passes it, so at this opposition Mars is not as big or bright as in years past. Still, Mars now rivals the brightest star at night, Sirius, and is now as bright as it will get until May 2016.

Saturn remains in the pre-dawn sky. Face south right before sunup to see it. You can also begin observing Saturn in late evening. It rises just after 10:30 p.m. tonight, and then about a half hour earlier each night until by month’s end, it’s up until twilight. Saturn comes to opposition next month.

Venus remains in the morning sky. Look southeast at dawn for the brightest point of light there; only the Sun and Moon outshine Venus. Venus remains a morning star for almost all of 2014.

Brilliant winter stars shift towards the west during April. Dazzling Orion is high in the southwest at dusk. His three-starred belt is halfway between reddish Betelgeuse and bluish Rigel. Orion’s belt points right to Aldebaran in Taurus the Bull. Above Orion are the twin stars Castor and Pollux, marking the heads of Gemini the Twins. Jupiter is among the Twins this month. You can find Sirius, the brightest star we ever see at night, by drawing a line south from Orion’s belt (left as you face west). Forming a triangle with Betelgeuse and Sirius is Procyon the Little Dog Star.

Joining the winter stars are stars of spring in the south and east. Look for Leo the Lion almost overhead at dusk. In the east, extend the Big Dipper’s handle to “arc to Arcturus” and then “speed on to Spica.”

Moon Phases in April 2014:

1st Quarter: April 7, 3:31 a.m.
Full: April 15, 2:44 a.m.
Last Quarter: April 22, 2:52 a.m.
New: April 29, 1:17 a.m.

The Full Moon of Tuesday morning, April 15, fully enters the Moon’s shadow, causing a total eclipse of the Moon. The Moon first encounters the shadow at 12:58 a.m.; that’s when the partial phases begin. By 2:06 a.m., the Moon is all the way inside the shadow, and thus totally eclipsed. The Moon takes 78 minutes to cross the shadow, so totality lasts until 3:24 a.m.. The Moon then emerges from the Earth’s shadow until the eclipse is over at 4:33 a.m.

Keep in mind that the eclipse happens in the morning hours of Tues., April 15. Don’t go out looking for this Tuesday night! Our George Observatory will be open from sundown Mon., April 14 until dawn on Tues., April 15 for observing the eclipse. If you can’t come to the George at such early morning hours, remember that anyone who sees the Moon sees the eclipse. You can observe this eclipse from your backyard or even through your window if you have one that faces south/southwest.

The only thing that can stop you from seeing the eclipse is overcast weather. If we do get clouded out, or if you can’t get up in the middle of the night, we can observe another eclipse on Oct. 8, 2014, right before dawn.

Click here to see the HMNS Planetarium Schedule

On most clear Saturday nights at the George Observatory, you can hear me do live star tours on the observation deck with a green laser pointer. If you’re there, listen for my announcement.

Clear skies!

Coming Soon: Total Eclipse of the Moon! [Dec. 21, 2010]

A total eclipse of the moon will occur very early Tuesday morning, Dec. 21, 2010. Houstonians will be able to see the whole event, which begins shortly after midnight.  If you happen to be traveling for the holidays, don’t worry – our entire continent has a full view of this eclipse.

When will the Lunar Eclipse Occur?

Note the timing, which might throw off some people.  The night we’re talking about is Monday night, December 20, and Tuesday morning, December 21.  For people in Houston, the eclipse starts at about 12:30 a.m., so the date is December 21.  If you go out on the night of the 21st looking for this event, you will have missed it by one day.

All times are listed in CST:

Stage Tuesday, Dec. 21
Partial Eclipse 12:32 a.m.
Totality Begins 1:40 a.m.
Mid-eclipse 2:17 a.m.
Totality Ends 2:54 a.m.
Eclipse Ends 4:01 a.m.

Why do Lunar Eclipses Occur?

Lunar eclipses occur when the full moon moves into the Earth’s shadow.  The orbits of the Earth and moon are not exactly in the same plane; the moon’s orbit is inclined to ours by about 5 degrees.  This may not seem like much, but it is enough to make the full moon miss the Earth’s shadow most of the time.

About twice a year, the full moon is close enough to Earth’s orbital plane to encounter the shadow rather than passing above it or below it.  Even at that, a slightly imprecise alignment may cause the moon to skirt the edge of the shadow (resulting in only a partial eclipse) or even just the penumbra (no noticeable change for us).  For example, on the morning of June 26, the moon never fully entered Earth’s shadow, and we saw it set in partial eclipse.

Finally, when the moon does go all the way into the Earth’s shadow, we see the event only if it happens during our nighttime, and if skies are clear.  During the last total lunar eclipse visible in America, on February 20, 2008, we were clouded out in Houston.  Given all of these factors, the opportunity to watch a lunar eclipse is quite special.  Let’s all hope the weather cooperates and we all can take some time to enjoy this spectacular sight.

What to Watch For: Observing An Eclipse

Lunar Eclipse March 2007
Creative Commons License photo credit: foxypar4

Observing the eclipse is quite simple; everyone who sees the moon sees the eclipse. Unlike the sun, the moon presents no danger to our eyes when observed directly. No special observing equipment is necessary. Unlike dimmer objects such as meteors, the moon shows up clearly even among bright city lights. You can enjoy the eclipse from your backyard, even if this is in the middle of Houston.

As the Earth blocks sunlight and casts a shadow across space, we can define two regions.  The umbra is the region of space in which Earth completely blocks the sun.  The penumbra is the region of space in which Earth only partially blocks the sun.

The first part of the Earth’s shadow that the moon will encounter is the penumbra. The penumbral shadow’s faintness means that even sharp-eyed observers will notice only a slight dimming of the moon between 11:28 p.m. on Monday night and 12:32 a.m. Tuesday. The moon moves into the darkest part of the earth’s shadow, the umbra, at 12:32 a.m, and will be totally eclipsed by 1:40 a.m.  Totality lasts 73 minutes because once in, the moon takes until 2:53 a.m. to cross to the other side of the umbra.  The moon then takes just over an hour to re-emerge from the umbra.  By 4:01 a.m., the moon has moved out of the Earth’s shadow, and the eclipse is over.

How Bright will the Eclipse Be?

Eclipse burning bright
Creative Commons License photo credit: ericskiff

The moon’s brightness during a total eclipse depends on the amount of dust particles in the atmosphere. A large amount of dust from a volcanic eruption, for example, can make the totally-eclipsed moon almost invisible. With little dust in our atmosphere, the moon glows reddish-orange during totality. This is because only the sun’s red light is bent enough by the Earth’s atmosphere that it lands on the moon even while it is in the Earth’s shadow.

As this diagram shows, the moon will pass through the northern part of the shadow, for about 73 minutes of totality. As a result, the bottom (southern) limb, closer to the center of Earth’s shadow, will appear darker.

Last Chance to See A Lunar Eclipse?

There are two lunar eclipses in 2011, but Houstonians won’t get a good look at either one.  The eclipse of June 15, 2011 occurs while we’re having daytime.  On the morning of December 10, 2001, an eclipse gets underway just as the moon sets for us.  In Houston, we see only the first 15 minutes of that eclipse.  (Observers farther north and west see more.)  We won’t see our next total lunar eclipse in Houston until just after midnight on April 15, 2014.

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.