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!

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.

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.