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.
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 wouldnâ€™t expect an object this big to pass this close but every 30 years,â€ said Don Yeomans, manager of NASAâ€™s Near-Earth Object Program Office and the Jet Propulsion Laboratory in Pasadena.
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.
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.