The ‘blood moon’ in Houston: Stay up late at the George for a stunning celestial show

A total eclipse of the Moon will occur very early Tuesday morning, April 15. Houstonians will be able to see the whole event, which begins just before 1 a.m. You’ll be able to see the evening’s cosmic events unfold even under city lights, but if you’d like a more detailed (and dare I say captivating) look at the eclipse, the George Observatory will be open all night long!

Lunar eclipses occur when the full Moon moves into the Earth’s shadow. The first part of the Earth’s shadow that the Moon will encounter is the penumbra. The penumbral shadow’s faintness means that sharp-eyed observers will notice only a slight dimming of the Moon between 11:55 p.m. on Monday night and 12:58 a.m. Tuesday. The Moon moves into the darkest part of the earth’s shadow, the umbra, at 12:58 a.m., and will be totally eclipsed by 2:06 a.m.

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 comes through the Earth’s atmosphere and falls on the Moon even while it is in the Earth’s shadow. As the diagram shows, the Moon will pass through the southern part of the shadow, for about 78 minutes of totality. As a result, the northern limb, closer to the center of Earth’s shadow, will appear darker.

We’ll see our next total lunar eclipse in Houston just before dawn on October 8, 2014 (the second of four occurring between 2014 and 2015!).

For more on how lunar eclipses work, watch the video below from NASA and USA Today.

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! August Edition

Jupiter is up all night long this month.  On August 14, the Earth passes between Jupiter and the Sun.  This alignment is called ‘opposition’ because it places Jupiter opposite the Sun in our sky, making it visible from dusk to dawn.  Tonight, Jupiter rises just before 9 p.m.—in late twilight.  It could take some time for Jupiter to clear trees or buildings around your observing site.  Soon, however, Jupiter will be already in the sky even as night is falling.  Face southeast and look for the brightest point of light there.  Early risers can still see Jupiter in the southwest before dawn.  Remember, Jupiter outshines everything in the sky except the Sun, the Moon, and Venus, so if you’re looking in the right direction, you can’t miss it.  

Venus is a dazzling morning star this month.  Look east right as day begins to break for the brightest thing unless the Moon is nearby.  Venus remains the ‘morning star’ for the rest of 2009.  Mars is a little higher in the east at dawn than it has been.  Still, it remains fairly dim.  Look for Mars above Venus in the east. 

is now low in the west at dusk, and will become difficult to observe by mid and late August.  The rings continue to appear thinner and thinner as Earth continues to align with Saturn’s ring plane, making the rings appear edge-on from our perspective.  On September 4, the Earth is exactly in Saturn’s ring plane, and the rings actually vanish from view!  It turns out, though, that Saturn is too close to the Sun in our sky on that date; the Earth will be about to pass on the far side of the Sun from Saturn.  No one can get a good look at Saturn this September.  Still, we can watch through our telescopes as Saturn’s rings appear thinner and thinner throughout August.  Since we’re seeing the rings edgewise, Titan and other moons have been passing in front of and behind Saturn’s disk.  This happens again on August 18, when Titan transits (passes in front of) Saturn’s disk.  By August 18, however, Saturn is so close to the Sun in our sky that it is only about five degrees high during late twilight and sets before night completely falls. 

Saturn
Creative Commons License photo credit: Elsie esq.

Saturn

The Big Dipper is high in the northwest on summer evenings.  From the Big Dipper’s handle, you can ‘arc to Arcturus.’  Arcturus, in the west at dusk, is the fourth brightest star we ever see at night and will be the brightest star in our evening skies during all of August. Continuing the curve of the Big Dipper’s handle past Arcturus, you can ‘speed on to Spica,’ a star lower in the southwest at dusk.  Spica is a stalk of wheat held by the constellation Virgo, the Virgin, who represents the harvest goddess.

Milky Way and a meteor?
Creative Commons License photo credit: madmiked

In the south as night falls is Antares in Scorpius, the Scorpion.  This is a red supergiant star about 700 times as wide across as our Sun.  To the Scorpion’s left, look for eight stars in the shape of a teapot.  These stars are the bow and arrow of Sagittarius, the Archer.  High in the east, the Summer Triangle dominates the evening sky.  The Triangle is up all night long until mid-August.  Vega is the brightest of the triangle’s three stars, followed by Altair in Aquila and Deneb in Cygnus.  Rising in the east on August evenings is the Great Square of Pegasus, heralding the upcoming autumn. 

Moon Phases in August 2009:

Full                                    August 5, 7:55 pm
Last Quarter                  August 13, 1:55 pm
New                                   August 20, 5:01 am
1st Quarter                     August 27, 6:41 am 

The Full Moon of August 5 almost enters the Earth’s shadow.  It does skirt the edge of the penumbra, in which the Earth partially blocks the Sun.  The resulting penumbral eclipse is scarcely noticeable at all, however.  When there is a central solar eclipse, as occurred last month in Asia, there are often penumbral (or very short partial) lunar eclipses two weeks before and after. 

Perseid Meteor
Creative Commons License photo credit: aresauburn™

The Perseid meteor shower peaks on the morning of August 12.  Our George Observatory will be open on the night of August 11-12 until dawn for observing the meteors.  Keep in mind that instead of the meteors running into the Earth, Earth is running into the meteors.  Thus, the leading edge of the Earth—the side going from night into day—sees more meteors.  This means you’ll see more meteors towards dawn than at dusk.  The Perseid shower averages about 2 meteors per minute each year, but this year a large waning gibbous Moon will hide many of those shooting stars from us.  If you observe the shower anywhere near a big city, light pollution will hide even more. 

The following Friday, August 14, is Members Night at the George Observatory.  The Perseid shower and the Members Night are events 63 and 64 of our Fun Hundred events to celebrate the museum’s 100th anniversary.

Go Stargazing! July edition

Jupiter becomes a late evening object by the end of the month.  It rises in the southeast just after 11 p.m. on July 1, although you may need to wait awhile for it to clear trees or buildings in that direction.  By month’s end, Jupiter rises at 9 p.m. — in late twilight.  Early risers can still see Jupiter in the southwest before dawn.  Next month, Jupiter is in the sky literally all night long.  Remember, Jupiter outshines everything in the sky except the Sun, the Moon, and Venus, so if you’re looking in the right direction, you can’t miss it.

Venus is a dazzling morning star this month.  Look east right as day begins to break for the brightest thing unless the Moon is nearby.  Venus remains the ‘morning star’ for the rest of 2009.  Mars is a little higher in the east at dawn than it has been.  Still, it remains fairly dim.  Look for Mars above Venus and to its right.  This is quite a mismatched pair; Venus is about 100 times brighter than Mars.

Saturn portrait
Creative Commons License photo credit: Elsie esq.

Saturn remains well placed in the evening sky this month.  Look for it in the west at dusk.  If you have seen Saturn through a telescope this year, you may have noticed how much thinner the rings appear now than in years past.  This is because Earth is beginning to align with Saturn’s ring plane, making the rings appear edge-on from our perspective.  On September 4, the Earth is exactly in Saturn’s ring plane, and the rings actually vanish from view!  It turns out, though, that Saturn is too close to the Sun in our sky on that date; the Earth will be about to pass on the far side of the Sun from Saturn.  No one can get a good look at Saturn this September.  However, we can still watch through our telescopes as Saturn’s rings appear thinner and thinner throughout July and August.

Saturn’s moons orbit in the same plane as its rings.  Since we ordinarily have a perspective looking over one of Saturn’s poles, moons such as Titan and Rhea can usually appear above or below Saturn as well as to its right or left in a telescopic image.  These moons are not normally blocked by Saturn.  That changes, however, when Earth aligns with Saturn’s ring plane.  Now that we’re seeing the entire system edgewise, we’re beginning to see Saturn’s moons pass in front of and behind Saturn’s disk.  The passage of a moon in front of a planet’s disk is a transit, while an occultation occurs when a planet’s disk blocks a moon.  When a moon transits, we can often see its shadow on the planet’s disk.  Here are some upcoming events for Saturn and Titan as seen from Houston:

7/9        Titan is partly occulted (blocked) by Saturn until 9:30 pm.

7/17      Titan is already in transit as night falls; it leaves the Sun’s disk between 9:45 and 10:20. (Titan appears as a disk and not a point, so it takes some time to move all of the way off Saturn’s disk.  Saturn sets by 11:15.

7/25      Titan is occulted by Saturn.

8/2        Titan is in transit from dusk until Saturn sets.  Titan’s shadow appears on Saturn’s disk at 9:30.

8/10      Titan occulted by Saturn

8/18      Titan transits Saturn.

By August 18, however, Saturn is so close to the Sun in our sky that it is only about five degrees high during late twilight and sets before night completely falls.

M42 Orion
Creative Commons License photo credit: makelessnoise

Look high in the west at dusk for stars in the shape of a backwards question mark, with a right triangle to the left of that.  These stars are in Leo, the Lion.  Saturn is under the ‘right angle’ in that right triangle.  The Big Dipper is high in the northwest on summer evenings.  From the Big Dipper’s handle, you can ‘arc to Arcturus.’  Arcturus, in the west at dusk, is the fourth brightest star we ever see at night and will be the brightest star in our night skies during all of July. Continuing the curve of the Big Dipper’s handle past Arcturus, you can ‘speed on to Spica,’ a star lower in the southwest at dusk.  Spica is a stalk of wheat held by Virgo, the Virgin, who represents the harvest goddess.

In the south as night falls is Antares in Scorpius, the Scorpion.  This is a red super giant star about 700 times as wide across as our Sun.  To the Scorpion’s left, look for eight stars in the shape of a teapot.  These stars are the bow and arrow of Sagittarius, the Archer.  In the east, the Summer Triangle dominates the evening sky.  The Triangle is up all night long until mid-August.  Vega is the brightest of the triangle’s three stars, followed by Altair in Aquila and Deneb in Cygnus.

Moon Phases in July 2009:

Full                                   July 7, 4:21 am
Last Quarter                     July 15, 4:53 am
New                                  July 21, 9:34 pm
1st Quarter                       July 28, 4:59 pm

Eclipsed? Not totally.
Creative Commons License photo credit: James Jordan

The New Moon of July 21 lines up well enough with the Earth and Sun to cast its shadow on the Earth.  This causes a total solar eclipse.  The Moon’s shadow first encounters the Earth just north of Mumbai in India, so that’s where the path of totality begins.  From there, the shadow moves across Bhutan and then southern China, including Shanghai.  The shadow then ends up over the Pacific Ocean and leaves Earth before ever again reaching land.  The only part of the US anywhere close to this path is Hawaii, which experiences a partial eclipse.  This is mostly an event for Asia, where the date will be July 22.

The next total solar eclipse visible in the USA will occur August 21, 2017.

The Full Moon of July 7 almost enters the Earth’s shadow.  It does skirt the edge of the penumbra, in which the Earth partially blocks the Sun.  The resulting penumbral eclipse is scarcely noticeable at all, however.

At 3 a.m. on Friday, July 3, Earth is as far as possible from the Sun (i.e., at aphelion).  Planetary orbits are not perfect circles but ellipses.  Thus, Earth does not remain at the same distance from the Sun throughout its orbit, but gets slightly closer in January and slightly farther in July.  The difference is only about 3.4%, however—not enough to affect our seasons.  The change in seasons is due to the Earth’s tilt on its axis, not the distance from the sun.