Big Asteroid To Fly By Earth This Fall

The near-Earth asteroid 2005 YU55 as "seen" by radar with the Arecibo telescope on April 19, 2010. At the time, the asteroid was 1.5 million miles from Earth. Credit: NASA/Cornell/Arecibo

It’s not unusual for tiny asteroids tens of feet across to pass within the moon’s distance (240,000 miles) of Earth every few months, but one 1/4 mile (1,300 feet) across, well, that’s a bit out of the ordinary. But come November 8 at 5:28 p.m. CST, asteroid 2005 YU55 will fly by Earth at a distance of only 186,000 miles.

The C-type asteroid 253 Mathilda photographed by the NEAR Shoemaker space probe. Credit: NASA

That’s close enough that amateur astronomers in both northern and southern hemispheres will be able to spot the 11th magnitude object with small telescopes. Because of its proximity, the asteroid will jog quickly across the sky, appearing like a dim star on the move through the eyepiece. At closest approach, 2005 YU55 will be speeding at 8.6 degrees per hour or one full-moon diameter every three minutes. Zippy!

2005 YU55 was discovered by the Spacewatch Project on December 28, 1995. It’s classified as a C-type asteroid, meaning it’s similar to meteorites fallen here on Earth called carbonaceous chondrites (CCs). CCs contain small amounts of carbon and also clay, an indication they’ve been exposed to liquid water sometime in the distant past. C asteroids are commonly found in the colder, ‘outer suburbs’ of the bustling asteroid belt between Mars and Jupiter. 2005 YU55 has a rounded shape and a surface darker than charcoal.

“On average, one wouldn’t expect an object this big to pass this close but every 30 years,” said Don Yeomans, manager of NASA’s Near-Earth Object Program Office and the Jet Propulsion Laboratory in Pasadena.

2005 YU55's flyby of Earth on November 8-9, 2011 as seen from above the plane of Earth's orbit. Click the diagram for an animation. Credit: NASA

The asteroid’s close approach makes it wonderful target for radio telescopes. Astronomers plan to use the globe-spanning Goldstone network and the huge Arecibo radio telescope in Puerto Rico to ping it with radio waves and then analyze the returning echoes to make a detailed map of the flying rock. Features as small as 15 feet across should be visible. That’s better than recent spacecraft missions to other asteroids.

Astronomers will also be using optical and infrared telescopes in a coordinated effort to pull in more data on the asteroid. Among other things, they want to refine its orbit to determine if it might be a threat to our planet in the distant future.

The 1000-foot (305-meter) Arecibo dish is built into a mountain valley and covers about 20 acres. It's the most sensitive radio telescope on Earth. Credit: NAIC

2005 YU55 was initially seen as a potential threat to Earth because of its size and how closely its orbit brings it to Earth. Thanks to precise observations with the Arecibo telescope in 2005, scientists have ruled out any impacts for at least the next 100 years.

It’s next encounter with Earth will be in 2046. That year the asteroid could pass a similar distance from Earth or up to 46 million miles farther away. Just for fun, let’s use the Impact Simulator to see what would happen if one day 2005 YU55 hit the Earth. We’ll assume the asteroid’s made of porous rock, moving at at 50,000 km/hour and strikes the igneous (volcanic) rock on which Duluth is built at a 45-degree angle. Add it up and the strike would create a five-mile diameter crater 1,800 feet deep. That would easily obliterate the city and destroy the homes, infrastructure and forests for miles around.

But who wants to think about that on this lovely spring morning when the song sparrows have returned to sing in my trees.

16 Responses

  1. Mario

    This article is quite curious in that it says, on the next fly by in 2046, it could come the same distance close, or 46 million miles away. That is quite a difference in distance. Is this called precise scientific observations, or what? Who knows at its present distance what might effect it, before it comes our way? How curious that there will be three comet/asteroid events occurring within a four month period, centered around the oct. 18th event of elenin comet.

    1. astrobob

      Dear Mario, I’m not sure what article you’re referring to, but Comet Elenin has a very long orbital period — at least in the thousands of years — and will not be returning in 2046. As for the three events, you can find several events/alignments happening routinely. The key is: none of these you’re referring to is gravitationally significant and will not effect the Earth.

  2. Brandon r

    What’s the chance of an impact, and what are your thoughts about an “ascension” or spiritual awakening in 2012 is there any science behind it?

    1. astrobob

      Hi Brandon,
      Zero chance of an impact from that asteroid. It will safely pass by Earth at nearly the distance of the moon. As for a spiritual awakening, that’s a private experience that can happen anytime to anyone. It doesn’t need help from the hype that’s sure to come our way in 2012.

  3. Debra

    Hi bob if this was to somehow hit the earth where do you think it would most likely hit I’m from the uk will it hit near there

    1. astrobob

      I’ll be doing a write-up on it with a link to a map on how to find it when we get closer to the date.

  4. shawn

    astrobob how close will it get i heard it will hit the moon and earth gravitional poll will bring it closer what are your thoughts on that

    1. astrobob

      Asteroid 2005YU55 is 400 meters across and will pass about 192,000 miles from Earth on Nov. 8. It won’t hit the moon and our gravity won’t bring it closer. Though this is a close pass, the asteroid’s orbit is very well known and it absolutely will not hit Earth or the moon.

  5. Kevin Heider

    On 19 January 2029, 2005 YU55 will pass about 0.0019 AU (280,000 km; 180,000 mi) from Venus. The close approach to Venus in 2029 will determine how close the asteroid will pass the Earth in 2041. The uncertainties in the post-2029 trajectory will cause the asteroid to pass anywhere from 0.002 AU (300,000 km; 190,000 mi) and 0.3 AU from the Earth in 2041. Radar astrometry in November 2011 should clarify the Earth encounter situation in 2041 and beyond.

    — Kevin Heider

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