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Your guide to the asteroid encounter

NASA releases a new radar image of asteroid 2005 YU55 as it approaches Earth for a Tuesday close encounter. Watch Brian Williams' report for "NBC Nightly News."

Last updated 5:25 p.m. ET Nov. 8

The asteroid 2005 YU55 will pose no threat to Earth when it zooms by on Tuesday, but it will spark a frenzy of picture-taking and online chatting. So where do you find the good stuff?

The hottest action will be up in the sky: This space rock (which we'll call YU55 from here on out) is about a quarter-mile (400 meters) wide, which makes it wider than an aircraft carrier. It's due to zoom past us at 30,000 mph (50,000 kilometers per hour) at a minimum distance of 198,000 miles (319,000 kilometers) at 6:28 p.m. ET. That would bring it just within the orbit of the moon. But don't worry: YU55 is on course to miss the moon as well as Earth, and even if it did hit the lunar surface, the only thing that'd happen would be a fantastic fireworks show.


Aerospace engineers from Analytical Graphics Inc. created this animation of the asteroid flyby, including a comparison of the asteroid's size with an aircraft carrier. (Courtesy of AGI)

If YU55 did smash into Earth, it could conceivably turn a city into a smoking crater, or stir up a destructive tsunami. But the asteroid's orbital path doesn't pose any risk in the foreseeable future. It's not expected to have any effect on Earth's tides, or on seismic activity. From the cosmic perspective, this is no big deal. In fact, YU55 has come even closer to Earth over the centuries, but went undetected until just six years ago.

The fact that YU55 went unnoticed for so long does raise a question, however: What else are we missing out there?

The science team for NASA's Wide-field Infrared Survey Explorer recently estimated that more than 90 percent of the near-Earth asteroids wider than a kilometer (0.6 miles) have been identified, but that thousands of asteroids in YU55's size range still remain to be detected. That's why astronomers around the world are so interested in watching for YU55 during this go-round. Getting a close look at this space rock should provide good practice for monitoring other potentially hazardous asteroids.

Asteroid experts say the last time a space rock as big as YU55 came this close was in 1976, and the next time will be in 2028.

Watching it pass by
You won't be able to see YU55 zoom by with your naked eye. Even at its closest approach, the asteroid will be no brighter than magnitude 11 — much dimmer than the magnitude-6.5 threshold for naked-eye observations. Astronomers say you'd need something on the order of a 6-inch telescope, and you'd have to know exactly where to look.

Sky & Telescope's editors have offered viewing advice as well as charts that show YU55's progress through the constellations. If you have your telescope aimed in the right place, you should be able to see a starlike point moving from west to east. "It will be gliding fast enough to move along in real time as you watch using a moderately high-magnification eyepiece," Sky & Telescope says.

Sky & Telescope

Best seen from North America, the asteroid 2005 YU55 will race far across the constellations in just 11 hours on the night of Nov. 8-9. The times shown on this chart are GMT. Subtract five hours for Eastern Standard Time. Click on the image for a larger view.

Some amateur astronomers are involved in an effort to monitor variations in the asteroid's brightness during the encounter. Those variations can be used to determine how YU55 is rotating as it flies by. Check out this Sky & Telescope webpage for details.

Most of us won't be peering through telescopes when 6:28 p.m. ET rolls around. Instead, we'll be looking for pictures from the professionals. The best pictures are expected to come from radar observations: NASA's Goldstone radio telescope in California and the Arecibo observatory in Puerto Rico are the big guns in this field, but the National Radio Astronomy Organization will be putting other assets on the case as well, including the Green Bank Telescope in West Virginia, the Very Large Array in New Mexico, and the Very Long Baseline Array.

Other telescopes around the world will be watching as well. The Clay Center Observatory in Massachusetts, which became known for its telescopic imagery of high-flying SpaceShipOne, is planning to track the asteroid on video. Stay tuned for that imagery, which will be streamed online via msnbc.com as well as on Ustream and other outlets.

Watching it on the Web
NASA is offering two main portals to asteroid imagery: Asteroid and Comet Watch on the main NASA site, and Asteroid Watch on the Jet Propulsion Laboratory's website. Both those sites should feature the latest and greatest images available to the space agency, and you should be able to see movies of YU55's encounter by late Tuesday or Wednesday.

NASA has just released a new radar view of the asteroid, produced from Goldstone data at 2:45 p.m. ET Monday when it was about 860,000 miles (1.38 million kilometers) from Earth. The image looks pretty pixellated, but it nevertheless reveals what appear to be lumps and craters on the surface. Arecibo is due to join the observing campaign on Tuesday, and the pictures should get progressively better as the asteroid zooms closer.

NASA / JPL-Caltech

The radar image at left shows the asteroid 2005 YU55, as imaged by NASA's Goldstone radio telescope from a distance of 860,000 miles. At right, a diagram shows the asteroid's trajectory past Earth and the moon.

Another popular place to look for space imagery is SpaceWeather.com, which is already passing along intelligence for the flyby. If amateurs come up with cool pictures of YU55, you can bet some of them will appear on that website. Space.com is keeping close watch on the asteroid encounter, and we'll be sharing the best of their coverage.

French astrophotographer Thierry Legault has made a name for himself as the chronicler of fast-moving space phenomena, ranging from space shuttles and the International Space Station to high-flying satellites. I'd be surprised if he didn't at least attempt to catch YU55 on video as it flies by. And if you can read German, you'll enjoy science writer Daniel Fischer's live blog of the flyby.

Share what you see
Have you got questions about the asteroid, or about asteroids in general? The Washington Post's website is hosting a live online chat at 1:30 p.m. ET Tuesday with Thomas Statler, a planetary scientist with the National Science Foundation. The chat follows up on last week's online encounter with NSF's Scott Fisher and NASA's Don Yeomans.

JPL's Lance Benner explains what's going on with asteroid 2005 YU55.

There's a growing buzz about the YU55 encounter on Facebook: You can easily find a whole bunch of event pages. And some wag has already set up a Twitter account for @AsteroidYU55 ("Uncomfortably Close"). For the real lowdown in tweets, do a search on YU55 or #YU55.

If you've made a great sighting, or even if you've found a great site on the Web, I hope you'll share it with the rest of the class. You can pass along links or observations in your comments below. You can also share comments or pictures via the Cosmic Log Facebook page or our brand-new Google+ page. We may use your submissions in our own follow-up coverage of the Great Asteroid Encounter.

Update for 11 p.m. ET: Discovery News' Ian O'Neill lets fly with an "Angry Asteroid" mashup.

More about the encounter:


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