SpaceX's first Falcon 9 rocket launching toward the International Space Station ignites its nine main engines briefly in this NASA photo shortly before aborting the launch try on May 19, 2012 due to an unexpected engine sensor reading. The Falcon 9 rocket will now launch the Dragon cargo capsule to the space station on May 22.
CREDIT: NASA

CAPE CANAVERAL, Fla. — SpaceX engineers have replaced a faulty engine valve on a private rocket carrying the first commercial space capsule bound for the International Space Station following the last-second abort during an attempted liftoff Saturday (May 19).

The valve replacement came after SpaceX's Falcon 9 rocket, which will loft the firm's unmanned Dragon capsule toward the station, aborted its launch attempt a half-second before liftoff from a pad here at Cape Canaveral Air Force Station. Technicians investigating the glitch discovered a faulty check valve was to blame for the high engine pressure that forced the booster's engines to unexpectedly shut down.

SpaceX engineers replaced the balky valve late Saturday, and are now inspecting the Falcon 9 rocket in preparation for a possible second launch attempt early Tuesday (May 22).

"We will continue to review data on Sunday," company officials said in a statement Saturday evening. "If things look good, we will be ready to attempt to launch on Tuesday, May 22nd at 3:44 AM Eastern."

Dragon is set to become the first non-governmental spaceship to rendezvous and berth at the space station during a mission sponsored by NASA's COTS program (Commercial Orbital Transportation Services) aimed at procuring commercial U.S. vehicles capable of filling the gap left by the retired space shuttles.

The Hawthorne, Calif.-based SpaceX (short for Space Exploration Technologies Corp.) planned to launch Dragon atop its Falcon 9 rocket Saturday, but a high pressure reading in the booster's fifth engine caused a last-second abort.

"We had a nominal countdown right until about T minus 0.5 seconds," SpaceX president Gwynne Shotwell said during a news briefing following the abort. "Software did what it was supposed to do, aborted engine five, and we went through the remaining engine shutdown."

Technicians went out to the rocket's launch pad at the Air Force station's Complex 40 Saturday to examine the engines for signs of the issue's root cause.

"During rigorous inspections of the engine, SpaceX engineers discovered a faulty check valve on the Merlin engine," officials said in the statement.

The robotic Dragon capsule is due to deliver food, clothes, science equipment and other supplies to the space station when it arrives.

The mission is the final test flight scheduled for SpaceX before it can begin running regular delivery missions to the outpost. The company is contracted to fly at least 12 of these for NASA at a total price tag of $1.6 billion.

You can follow SPACE.com assistant managing editor Clara Moskowitz on Twitter @ClaraMoskowitz. Follow SPACE.com for the latest in space science and exploration news on Twitter @Spacedotcom and on Facebook.

On Jan. 4, 2011, the moon passed in front of the sun in a partial solar eclipse - as seen from parts of Earth. Here, the joint Japanese-American Hinode satellite captured the same breathtaking event from space. The unique view created what's called an annular solar eclipse.
CREDIT: Hinode/XRT

Skywatchers from China to Texas are in for a rare celestial treat today when the moon blots out most of the sun to create dazzling "ring of fire" solar eclipse.

The eclipse today (May 20) is known as an annular solar eclipse and is the first of its kind to be widely visible from much of the United States since 1994. Annular eclipses only occur when the moon is at a point in its orbit that is too far from Earth to completely block the sun's disk. The result is a  ring-like, or annulus, effect that will be visible to observers lucky enough to be in the path of the eclipse's shadow.  

"This is going to be a great photo opportunity," said Robert Naeye, editor in chief of Sky & Telescope magazine, in a statement.

During today's solar eclipse, the moon will block up to 94 percent of the sun's disc and last about 4 1/2 minutes for skywatchers inside a 186-mile-wide (300-kilometer) track that begins at 6:36 p.m. EDT (2236 GMT) in southern China (where the local time will be May 21), crosses the northern Pacific Ocean, then makes landfall in northern California. [Annular Solar Eclipse of May 20 (A Photo Guide)]

The eclipse's track will cross eight western U.S. states before it ends at sunset in northwestern Texas. While the "ring of fire" effect is only visible from the eclipse's primary track, wide regions around the eclipse path will get partial solar eclipse views, according to NASA eclipse expert Fred Espenak. The parts of the United States to miss the partial eclipse views are on the East Coast, he explained in NASA eclipse guide.

This NASA graphic depicts the path of best viewing for the annular solar eclipse of May 20, 2012.
CREDIT: Fred Espenak, NASA/GSFC

From start to finish, the annular solar eclipse — the first solar eclipse of 2012 — will last about 3 1/2 hours and cross about 8,450 miles (13,600 km) as it moves across the Earth.

"It certainly will not become as dark as night; instead you might call it a weird 'counterfeit twilight' as the quality of the light, may become unearthly," SPACE.com skywatching columnist Joe Rao explains in a viewing guide. "A clear sky should turn deep blue and the landscape oddly silvery. The temperature may take a perceptible drop; a cool breeze may begin to blow."

And the sun and moon aren't the only objects to see in the sky during the eclipse.

"Look for Venus — it's shining east of the sun by about two fist-widths at arm's length," advises Alan MacRobert, a senior editor with Sky & Telescope magazine. "Jupiter and Mercury will be tougher. They're on the other side of the sun by about a quarter and a third as far, respectively, and they're not as bright."

This NASA graphic of the United States depicts the path of the annular solar eclipse of May 20, 2012, when the moon will cover about 94 percent of the sun's surface as seen from Earth.
CREDIT: NASA/JPL, Jane Houston Jones Eclipse chasers around the world

Today's solar eclipse has drawn out intense interest from veteran astronomers and amateur skywatchers around the world.

Supplies of solar eclipse glasses reportedly ran low in many locations directly in the path of the eclipse and one venue – the University of Colorado at Boulder — is expecting a crowd of at least 13,000 people to fill to Folsom Field (a football stadium) for a free day of eclipse observing in what university official have billed the world's largest solar eclipse viewing party.

Astronauts may even see the solar eclipse from space, NASA officials said. The six-crew of the International Space Station may get a chance to observe the moon's shadow on Earth cast by the eclipse, they added.

Many organizations plan to offer live broadcasts of the solar eclipse. In Japan, for example, the electronics company Panasonic is staging an expedition to webcast the solar eclipse from the top of Mt. Fuji. [Webcast Info: How to Watch the Solar Eclipse Online]

In the United States, several groups have mounted expeditions to observe the solar eclipse from picturesque viewing spots.

Scientists at NASA's Lunar Science Institute at the Ames Research Center in Moffett Field, Calif., have ventured to Grand Canyon National Park in Arizona to witness the eclipse and offer free information sessions to park visitors. Well before today's event, the U.S. National Park Service issued a national invitation to the public to watch the solar eclipse from a national park.

Today, the National Park Service will gather astronomers and park rangers at Petroglyph National Monument in Albuquerque, N.M., from 5 p.m. to 8:30 p.m. MDT to discuss the solar eclipse.  

For a list of solar eclipse viewing times for 52 cities in the United States, see this NASA chart Espenak.

For a list of solar eclipse viewing times in Canada, Mexico and Asia, Espenak has prepared this handy chart.

Solar eclipse safety

One important thing to keep in mind when planning to observe today's solar eclipse is eye safety. The sun can cause serious eye damage if observed by the unaided eye or through an unfiltered telescope.

NEVER observe the sun directly of with telescopes or binoculars without using proper solar filters. Regular sunglasses do NOT provide adequate protection for solar eclipse observing.

Seasoned skywatchers use solar filters for telescopes or binoculars to safely view the sun. Special eclipse glasses or welder's glass No. 14 can also serve as a proper filter.

A simple way to observe the sun is to create a pinhole projector, or a pinhole camera. The most simple version can be created by punching a tiny hole in a piece of paper holding it between the sun and another shaded piece of paper. Light from a telescope or binoculars can also be projected onto a separate paper viewing.

You can also build a pinhole project from a shoebox. Staff writer Natalie Wolchover of SPACE.com's sister site Life's Little Mysteries gives you complete, easy-to-follow pinhole camera instructions in this video.

SPACE.com will be providing team coverage of today's solar eclipse:

In San Francisco, SPACE.com senior writer Mike Wall will monitor the solar eclipse from the city's Exploratorium science center. In Boulder, Colo., Livescience senior writer Stephanie Pappas will cover the University of Colorado's giant solar eclipse viewing party at Folsom Field. In Arizona, SPACE.com contributors Imelda Joson and Edwin Aguirre — veteran eclipse chasers and space photographers— are seeking out a choice observing spot of the eclipse at Horseshoe Bend near Page, Ariz.

Visit SPACE.com tonight for more updates, photos and reports of May 20, 2012 annular solar eclipse.

Editor's note: If you snap a great photo of Sunday's annular solar eclipse and would like it to be considered for use in a story or gallery, please send images and comments to SPACE.com managing editor Tariq Malik at tmalik@space.com.

You can follow SPACE.com Managing Editor Tariq Malik on Twitter @tariqjmalik. Follow SPACE.com for the latest in space science and exploration news on Twitter @Spacedotcom and on Facebook.

The International Space Station (ISS) was in position to view the umbral (ground) shadow cast by the moon as it moved between Earth and the sun during a solar eclipse on March 29, 2006. This astronaut image captures the umbral shadow across southern Turkey, northern Cyprus and the Mediterranean Sea.
CREDIT: NASA

When the moon blocks the sun in a rare "ring of fire" solar eclipse Sunday (May 20), six astronauts living in space just might see the shadow on Earth created by the event from their home in space, NASA officials say.

The International Space Station crew will likely not see the peak of the solar eclipse, but the astronauts may see the shadow from a partial solar eclipse as it moves across the Pacific Ocean, NASA spokesman Bill Jeffs told SPACE.com.

"They may be able to see the moon’s shadow as a disc on Earth when they are nearest the full eclipse point at 23:36 (between Kamchatka [Peninsula] and the Aleutian Islands)," Jeffs told SPACE.com in an email. The space station crew operates on Greenwich Mean Time (Universal Time), putting their time closest to the eclipse's peak at about 7:36 p.m. EDT.

On Earth, observers along a wide section of East Asia, the Pacific Ocean and western United States will also see a partial solar eclipse. Other observers, located along the center line of the eclipse's path, will see the moon block out 94 percent of the sun, weather permitting. [Annular Solar Eclipse of May 20 (A Photo Guide)]

Sunday's solar eclipse is a relatively rare event known as an annular solar eclipse, an eclipse in which the moon is at a point in its orbit that makes it too small (as viewed from Earth) to completely block the sun. Instead, the moon blocks most of the sun, leaving a ring of light (formally known as an "annulus"), that can be a dazzling sight to onlookers observing through safe solar filters. The effect is also known informally as a "ring of fire" solar eclipse.

The eclipse's so-called "path of annularity" begins in China's Gulf of Tongking, to the north-northwest of Hainan Island, where the local time will actually be May 21. The moon's shadow then moves east, passing over Tokyo, Japan, and heading out over the Pacific Ocean before making landfall in northern California and crossing seven other western U.S. states to end in northwestern Texas at sunset.

But exactly what the space station crew may see remains to be seen.

Past observations of solar eclipse shadows from space have revealed dark, roughly circular blemishes on Earth. During solar eclipses, this shadow moves across the Earth at a speed of about 1,243 mph (2,000 kph).

The space station is currently home to two Americans, three Russians and one Dutch astronaut. The crew is scheduled to be in its sleep period during the best times to see the eclipse shadow from space, Jeffs said.

However, one of the American astronauts — NASA veteran Don Pettit — has been a prolific photographer of Earth from space and it is possible he or his crewmates may make an effort to observe the moon's shadow making its way across the western Pacific Ocean.

Editor's note: If you snap a great photo of Sunday's annular solar eclipse and would like it to be considered for use in a story or gallery, please send images and comments to SPACE.com managing editor Tariq Malik at tmalik@space.com.

You can follow SPACE.com Managing Editor Tariq Malik on Twitter @tariqjmalik. Follow SPACE.com for the latest in space science and exploration news on Twitter @Spacedotcom and on Facebook.

As the solar eclipse on May 20, 2012, progresses, its partial and annular phases will look very similar to this eclipse on May 10, 1994
CREDIT: Fred Espenak/SkyandTelescope.com

The moon will block the sun in a unique solar eclipse on Sunday, offering a potentially dazzling solar sight for skywatchers in parts of Asia and North America. But if you live anywhere else on the planet, don't fret – you can watch the solar eclipse online, too. And there are many webcasts to choose from.

Today's annular solar eclipse begins in southern China (where the local time is May 21) at about 6:06 p.m. EDT (2206 GMT)  and gradually makes its way eastward over 3 1/2 hours to cross the northern Pacific Ocean to the western United States, where it will end in northern Texas at local sunset. The peak eclipse views will be along a path about 186 miles wide (300 km) and 8,450 miles long (13,600 km), according to NASA eclipse expert Fred Espenak.

Editor's note: If you snap a great photo of Sunday's annular solar eclipse and would like it to be considered for use in a story or gallery, please send images and comments to SPACE.com managing editor Tariq Malik at tmalik@space.com.

Here's a look at several live webcasts of solar eclipse, beginning with the online Slooh Space Camera, which is offering views from several different observatories around the world beginning at 5:30 p.m. EDT (2130 GMT).  Slooh will track the eclipse as it leaves Japan and makes landfall on the western U.S., with viewers able to snap images from the website to share online.

You can view the webcast the Slooh website: http://www.slooh.com and below:

The U.S. National Parks Service will webcast the solar eclipse live from 9 p.m. to 12 a.m. EDT (0100 to 0400 May 21 GMT) from Petroglyph National Monument in Albuquerque, N.M. You can see the feed directly here or view it below:

interior on livestream.com. Broadcast Live Free

Colorado University in Boulder, Colo., will hold a massive solar eclipse viewing party at Folsom Stadium  - a football stadium - with more than 13,000 spectators expected. The university has partnered with Sommers-Bausch Observatory to offer a live solar eclipse webcast here from 5:30 p.m. to 8 p.m. MDT (7:30 p.m. to 11 p.m. EDT, 0030 to 0300 GMT).

See the Sommers-Bausch Observatory feed directly below:

Live broadcasting by Ustream

Sky and Telescope Magazine has also posted a list of webcast events for the solar eclipse, many of which are reproduced below.

The Hong Kong Observatory and Hong Kong SpaceMuseum are providing a joint feed, letting the world see the eclipse from the vantage point of the huge city in southern China.  Webcast available here starting at 5:41 p.m. EDT (2241 GMT).

Also here:

Streaming live video by Ustream

According to Sky and Telescope, the electronics company Panasonic will also broadcast live eclipse footage from the top of Japan's iconic Mt. Fuji,  The broadcast crew will scale the 12,390-foot (3,776-meter) peak with the aid of climbing guides. Panasonic's feed can be found below:

Streaming live video by Ustream

Sky and Telescope reports that amateur astronomer Scotty Degenhart will broadcast from Nevada's Area 51, a patch of desert about 80 miles (130 kilometers) northwest of Las Vegas. His feed will be available here: 

Free live streaming by Ustream

More solar eclipse feeds from Sky and Telescope Magazine here.

Editor's note: If you snap a great photo of Sunday's annular solar eclipse and would like it to be considered for use in a story or gallery, please send images and comments to SPACE.com managing editor Tariq Malik at tmalik@space.com.

Follow SPACE.com for the latest in space science and exploration news on Twitter @Spacedotcom and on Facebook.

The safest and simplest technique to observe and photograph the eclipse is to use your telescope (or one side of your binoculars) to project a magnified image of the sun’s disk onto a shaded white piece of cardboard. This view was taken near Boston during the partial solar eclipse on Christmas Day 2000.
CREDIT: Imelda Joson and Edwin Aguirre

With a potentially spectacular solar eclipse to grace the skies of the western United States on Sunday (May 20), here's a helpful reminder for new eclipse chasers: Be safe. A fraction of a second of magnified, unfiltered sunlight will sear your eye’s retina irreparably.

Imagine a horrible sunburn on your eyeball. Your eye cannot grow new layers and slough off the singed ones like your skin tissue can, so staring directly at the sun is dangerous without the protection of safety equipment used by veteran skywatchers and astronomers.

So, practice Safe Sun: Don't ever look directly at it! Not with your eyes, binoculars, and certainly not with a telescope unless you have proper optical filters. Whether there's a solar eclipse or not, direct sunlight harms eyesight.

Imelda Joson and Edwin Aguirre captured the May 10, 1994 annular solar eclipse from the eclipse path’s northern limit near Lordsburg, N.M.. They used a filtered 4-inch Meade telescope with a focal length of 1,000 millimeters and Kodak Royal Gold 400 color-negative film.
CREDIT: Imelda Joson and Edwin Aguirre Warning: Sunday's solar eclipse is dangerous!

Solar eclipses such as annular eclipse on Sunday can be treacherous for the inexperienced. A ring ("annulus") of the sun's disk remains in view even at the moment of maximum coverage by the moon. Your eye's iris will be fooled by the relative darkness of the moon's silhouette. But dangerous direct sunlight appears around the edges and can hurt you badly without precautions. [Solar Eclipse of May 20, 2012 (Photo Guide)]

Experienced eclipse chasers watching a total solar eclipse will have a short time — during totality only — when they may view the eclipse directly. Don’t try this unless you are with someone who has done it before and can still see. But don’t try it at all under Sunday's annular solar eclipse.

Eclipse or not, always use a proper filter when observing or photographing the sun. Regular sunglasses and photographic polarizing or neutral-density (ND) filters are not safe for use on the sun.
CREDIT: Imelda Joson and Edwin Aguirre Safe sun observing

If you’re planning to watch a solar eclipse or look for sunspots, what is the proper optical filter material for sun-watching?

Eclipse glasses are designed and marketed for exactly this purpose. Shop them online if you have time before the event you’re planning to watch. Your local museum store may stock them. Try and buy them online from a reputable telescope maker (e.g., Orion, Meade, Celestron).

If you can get hold of them, welder's goggles rated at 14 or higher will protect your vision. The nice thing about goggles as opposed to glasses: They have straps. They’re not likely to fall off. Less safe is to hold a piece of No. 14 welder's glass up to the sun.

Seasoned eclipse observers and astronomers who know what they’re doing sometimes use aluminized Mylar sheeting. The aluminum residue blocks much of the harmful infrared and ultraviolet light. But be sure the material really is aluminized Mylar. And don't use it to jury-rig a filter over binoculars, telescopes or any other kind of lens-based or mirrored device.

The best way to attach your digital SLR camera to the telescope is to use an appropriate T ring and T adapter for your camera brand. (Check with your local camera retailer.) Other helpful accessories include an electronic cable release to operate the shutter and a right-angle magnifier that attaches to the camera’s viewfinder to assist you in focusing.
CREDIT: Imelda Joson and Edwin Aguirre

Despite what you may have heard, DO NOT USE PHOTOGRAPHIC FILM — especially not medical X-rays that you may have around. While there are some emulsions which, when developed after being fully exposed, can make effective filters, it is very difficult to know if the film stock you have will be safe.

Only black and white film made with a silver emulsion, fully exposed and fully developed, can be used, and only if you are absolutely sure. Color films are never safe.

Other "Unsafe for Sun" filters include smoked glass, brown or green glass (think beer bottles), polarized sunglasses /car windshields or "neural density" filters for cameras. Just because the sun looks dark through the substance does not mean that perilous invisible infrared light or hazardous ultraviolet light is not reaching your delicate retina. [How to Look at the Sun and Not Go Blind (Infographic)]

Pinhole camera/projector and telescope — pinhole projector

The safest way to view solar eclipses using items you probably have at home is to build a pinhole camera. Our colleague Natalie Wolchover of Life's Little Mysteries gives you complete, easy-to-follow pinhole camera instructions in this video.

If you have a telescope, make sure to get the correct solar filter for it. An unfiltered telescope pointed at the sun is very dangerous, even if no one looks through it. It can start fires in seconds. [Remember those unfortunate ants the neighbor kid incinerated with his magnifying glass?] 

The right filter is not only very dark at most wavelengths; it tightly grips the optical tube — or the first element in the light path — so that it can’t be knocked off.

Also, remember to remove your finder scope or any other secondary magnifier. Even if capped, these can get hot in extended sunlight and easily warp or crack.

But if your finder scope is off, how to you align your telescope to that big bright star you want to see? Simple: look at the shadow in the ground. Move your scope around until the shadow’s footprint is smallest. Now you’re perfectly on the sun!

To see these tips in action, watch this video on observing the sun with a telescope.

See the sun online

Of course, the sun is always available online. NASA's Solar Dynamics Observatory — in geosynchronous orbit — has a better view than you and I will ever get. This smart spacecraft keeps itself pointing on the sun, down-linking 130MB of science data every second. NASA's Goddard Space Flight Center publishes SDO’s stunning images to an interactive online player. You can zoom in on active regions, fly across the flares silhouetted off the sun’s limb, spot solar tornadoes … Our star's surface is a fascinating and frightening place.

NOTE:The Solar Dynamics Observatory will not be in a position to "see" the May 20 annular eclipse. Neither NASA's Solar Terrestrial Relations Observatory nor the joint ESA/NASA Solar Heliospheric Observatory will see it, either. But the Japanese-U.S. Hinode satellite will catch four discrete partial eclipses during this time.

This NASA graphic of the United States depicts the path of the annular solar eclipse of May 20, 2012, when the moon will cover about 94 percent of the sun's surface as seen from Earth.
CREDIT: NASA/JPL, Jane Houston Jones Final Warning

By the way, did I mention? Don't EVER stare directly at the sun! Not with your eyes, not with binoculars, certainly not with a telescope unless you have PROPER optical filters.

I practice Safe Sun. So should you.

Editor's note: If you snap any safe and amazing solar eclipse photos that you'd like to be considered for use in a story or gallery, please send images and comments to SPACE.com managing editor Tariq Malik at tmalik@space.com.

Follow SPACE.com for the latest in space science and exploration news on Twitter @Spacedotcom and on Facebook.

As the solar eclipse on May 20, 2012, progresses, its partial and annular phases will look very similar to this eclipse on May 10, 1994
CREDIT: Fred Espenak/SkyandTelescope.com

When the moon blots out the sun in a solar eclipse on Sunday (May 20), producing a "ring of fire" in the sky, it will cover roughly 94 percent that of the sun and offer a rare view of our nearest star.

The remaining sun ring visible at the peak of the solar eclipse will  appear with a width of 3 percent of the sun’s diameter. While that might not sound like a lot, it will still be enough to drown out the beautiful solar corona, as well as the sun’s ruby red chromosphere and any prominences — such as plumes of hydrogen gas, leaping off of the limb of the sun.

Meanwhile, the sky (while getting somewhat dimmer) will never darken enough to see any bright stars or planets. All of these sights are reserved solely for a total eclipse.

Or are they?

As it turns out, we can have a wide variety of annular solar eclipses and that ring of fire can appear quite different depending on specific circumstances, namely the distance of the Earth to the sun and of the moon to the Earth. 

In fact, if the Earth revolved around the sun in a perfect circle, at its mean distance of 92.9 million miles (149.5 million kilometers), and the moon revolved around the Earth in a perfect circle equal to its mean distance of 238,857 miles (384,320 km), then a total eclipse of the sun would be impossible, because the moon as seen from the Earth would appear too small to completely cover the sun. So we would always see an annular or ring eclipse.

Fortunately, the moon can come closer to Earth than its mean distance. As a result, there are times when it will be large enough to totally eclipse the sun. In fact, there are occasions when the moon will be at a point in its orbit where its apparent diameter literally matches that of the sun (or very nearly so). The result is an annular eclipse that displays some of the characteristics of a total eclipse. [Annular Solar Eclipse of May 20 (A Photo Guide)]

Skinny ring: Some of our readers may remember an annular eclipse that swept across parts of the Southeast and Mid-Atlantic States on May 30, 1984. On that day, the tip of the moon’s dark umbral shadow missed the Earth by less than 500 miles (800 km) and the moon’s disk had an apparent diameter less than two-tenths of 1 percent that of the sun. 

And because of the moon’s rugged topography, instead of a ring, observers who were positioned along the eclipse track that day (which included Atlanta and Greensboro, N.C.) saw an exceedingly thin ring, punctuated here and there by bright beads of sunlight. Those who blocked out the beads with their thumb could actually glimpse the corona. And even though it was only a few degrees from the sun, Venus popped into view. 

Because the ring was so delicately thin, annularity did not last very long – less than 10 seconds.

This NASA graphic of the United States depicts the path of the annular solar eclipse of May 20, 2012, when the moon will cover about 94 percent of the sun's surface as seen from Earth.
CREDIT: NASA/JPL, Jane Houston Jones

Fat ring: In contrast, on Dec. 24, 1973, an annular eclipse swept across parts of Mexico, Central America and Africa. It occurred around the time that the moon was at its most distant from Earth (called apogee), so it appeared to be very small. But it also took place near the time that Earth was near its closest point to the sun (called perihelion), so the sun appeared larger than normal. 

In the end, the moon appeared 9 percent smaller than the sun, creating a very "fat" ring nearly 5 percent of the sun’s diameter in width and causing the ring phase to last  almost 12 minutes for some. With so much of the sun left uncovered, the sky didn't get overly dim; some who witnessed it later said that if you didn't know in advance that an eclipse was taking place, you wouldn’t have noticed it at all. [Quiz: How Well Do You Know the Sun?]

Sunday’s eclipse falls in the middle of these two extremes. 

The moon will be near its apogee point, making it appear rather small, but the sun is also approaching its farthest point from Earth (aphelion) in early July, making it appear somewhat smaller than normal and thus compensating for the moon’s smaller than normal size. So the ring will not be as wide as it was in 1973, but it will be nowhere near as thin as it was when it was almost total in 1984.

Next year: Interestingly, next year on Nov. 3, 2013, there will be a very special kind of solar eclipse — a "hybrid eclipse."

The hybrid solar eclipse will start as an annular over the Atlantic Ocean about midway between Bermuda and Puerto Rico then transition into a total eclipse as the moon’s shadow heads for Africa. That eclipse will result in a partial eclipse at sunrise for the U.S. East Coast.  And for some places, like Boston (which will not see any of this Sunday’s solar show), it will be their first solar eclipse since the year 2000. 

Mark your calendars!

Editor's note: If you snap any amazing solar eclipse photos that you'd like to be considered for use in a story or gallery, please send images and comments to SPACE.com managing editor Tariq Malik at tmalik@space.com.

Joe Rao serves as an instructor and guest lecturer at New York's Hayden Planetarium. He writes about astronomy for The New York Times and other publications, and he is also an on-camera meteorologist for News 12 Westchester, New York.

SpaceX's first Falcon 9 rocket launching toward the International Space Station ignites its nine main engines briefly in this NASA photo shortly before aborting the launch try on May 19, 2012 due to an unexpected engine sensor reading. The Falcon 9 rocket will now launch the Dragon cargo capsule to the space station on May 22.
CREDIT: NASA

CAPE CANAVERAL, Fla. — A potential rocket engine problem may be to blame for the unexpected abort of a private SpaceX rocket launch before dawn on Saturday (May 19), officials said.

SpaceX was slated to blast off its unmanned Dragon capsule and Falcon 9 rocket at 4:55 a.m. EDT (0855 GMT) from here at the Cape Canaveral Air Force Station. Just after igniting its main engines, the computer onboard the booster initiated an automatic abort due to a high pressure reading in one of the rocket's nine main engines.

Dragon was due to fly to the International Space Station to become the first non-governmental vehicle to berth there. The spacecraft's next chance to launch is Tuesday (May 22) at 3:44 a.m. EDT (0744 GMT), followed by a potential opportunity Wednesday (May 23) at 3:22 a.m. EDT (0722 GMT).

Before SpaceX will officially target a new launch date, however, the company will search for the root cause of today's glitch.

"We should have some technicians up into that engine at about noon today," SpaceX president Gwynne Shotwell said during a news briefing following the abort. "We'll be up looking for whatever we can find."

Initial indications suggest that the high pressure reading wasn't a sensor error, but did in fact indicate an abnormally high pressure inside the chamber of the Falcon 9's engine five, Shotwell said.

"Now we're just going to have to go in and spend a little bit more time looking at the data," she added.

If the engine looks to be unusable, SpaceX has another Falcon 9 here from which an engine could be swapped out, Shotwell said.

The flight is a trial run for SpaceX's plan to deliver cargo, and eventually crew, to the space station. The mission is partially funded by NASA's COTS (Commercial Orbital Transportation Services) program, and the firm has a NASA contract to fly 12 delivery missions to the outpost once test flights are completed.

"We're ready to support when SpaceX is ready to go," Alan Lindenmoyer, manager of NASA's commercial crew and cargo program, said during the briefing.

Officials from both NASA and SpaceX have emphasized the uncertain nature of test flights, and said that the main goal was to gather more data about the vehicle.

"This is not a failure," Shotwell said. "We aborted with purpose. It would have been a failure if we had lifted off with an engine trending in this direction."

You can follow SPACE.com assistant managing editor Clara Moskowitz on Twitter @ClaraMoskowitz. Follow SPACE.com for the latest in space science and exploration news on Twitter @Spacedotcom and on Facebook.

SpaceX's first Falcon 9 rocket launching toward the International Space Station ignites its nine main engines briefly in this NASA photo shortly before aborting the launch try on May 19, 2012 due to an unexpected engine sensor reading. The Falcon 9 rocket will now launch the Dragon cargo capsule to the space station on May 22.
CREDIT: NASA

When a privately built rocket aborted its launch attempt at the very last second today (May 19), it was likely a familiar sight to the booster's builders: the California-based company SpaceX.

SpaceX's unmanned Falcon 9 rocket aborted its launchattempt this morning just as the countdown reached T minus 0.5 seconds and the rocket's nine main engines ignited, apparently due to an unexpectedly high engine pressure reading. The rocket will now have to wait until at least Tuesday (May 22) to attempt to launch SpaceX's first robotic Dragon space capsule flight to the International Space Station.

The launch abort, while a delay, isn't a surprising turn of events for SpaceX. The company repeatedly pushed back the launch in recent months to allow extra time to review the rocket and Dragon capsule's flight software. The goal, SpaceX and NASA officials said at the time, was to make sure the rocket was as ready to fly as possible.

As recently as April 30, SpaceX pushed the launch back when the Falcon 9 rocket experienced a hiccup during an engine test atop the launch pad. A second engine test later proved everything was ready for launch.  [Photos: SpaceX Poised for Historic Launch]

No guarantees

SpaceX has a $1.6 billion contract to provide 12 Dragon capsule cargo flights to the space station for NASA, with this mission aimed at proving the space capsule's capabilities. With NASA's space shuttle fleet retired, the agency is depending on SpaceX and other commercial spaceship builders to provide much needed robotic cargo and manned vehicles to fill the void left by the shuttle program's end.

But SpaceX has repeatedly stated that the Falcon 9 and Dragon launch to the space station is an unprecedented test flight, one in which success is never guaranteed. 

"This mission is important, although I wouldn't want to place too much emphasis on the success of this mission, because it is a first time effort," SpaceX CEO and founder Elon Musk told SPACE.com in a recent interview. "If there's any danger or concern with respect to the space station, then we will have to abort and try again on a different flight."

Musk is a billionaire entrepreneur and co-founder of the Internet payment service Paypal. He founded the Hawthorne, Calif.-based SpaceX, formally known as Space Exploration Technologies Corp.,  in 2002 with the intention of developing a manned spacecraft capable of orbital and deep space flight.

The Falcon 9 rocket stands 157 feet tall (48 meters) and is a two-stage booster fueled by liquid oxygen and kerosene.

The challenge of private spaceflight

On Friday (May 18), SpaceX President Gwynne Shotwell acknowledged the company's challenges in hitting liftoff at launch time on the first try.

"We have not hit a T-Zero yet," Shotwell said, adding that she felt SpaceX had a better than 50-50 chance of launching today.

The current Falcon 9 mission is SpaceX's third mission for the rocket design, which made its debut in June 2010. A second flight successfully launched a Dragon capsule prototype into orbit in December 2010. The earlier Falcon 9 launches also saw delays or aborts, Shotwell said.

The Falcon 9 rocket's successful track record marked a major step forward for SpaceX, which launched three of its smaller Falcon 1 rockets before achieving a successful flight on the fourth try.

The spaceflight company SpaceX is one of several firms building private space taxis and cargo ships to launch astronauts and supplies into space. But there's more to SpaceX than meets the eye. Test your SpaceX know-how here.

Questions

SpaceX's next chance to launch the Falcon 9 rocket and Dragon capsule toward the space station comes before dawn on Tuesday, with Wednesday (May 23) available as a backup day if it is needed, NASA officials said.

After standing down from today's launch attempt, Shotwell stressed that there's a big difference between a launch abort and an outright launch failure.

"This is not a failure," Shotwelll said. "We aborted with purpose. It would have been a failure if we had lifted off with an engine trending in this situation."

You can follow SPACE.com Managing Editor Tariq Malik on Twitter @tariqjmalik. Follow SPACE.com for the latest in space science and exploration news on Twitter @Spacedotcom and on Facebook.

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Computers aboard the Falcon 9 rocket cut off the engines after seeing a high pressure warning. Next launch attempt could occur on Tues May 22nd after the problem is investigated.

Credit: NASA / SpaceX