A mountain-size space rock will sail past Earth on Monday, offering stargazers a close look at an interplanetary pinball. Luckily, NASA says there is no risk of collision, but it will be a rare astronomically close encounter that backyard telescope owners can watch.
The large asteroid, called 2004 BL86, measures about a third of a mile (half a kilometer) across. It will make its closest approach to Earth on January 26, coming within only 745,000 miles (1.2 million kilometers) from our planet—about three times the distance separating the Earth and the moon.
While there have been many asteroids that have barnstormed Earth much closer, this will be the largest one to come that close until 2027, when a slightly smaller asteroid, 1999 AN10, may come closer to Earth than the moon. What makes Monday's flyby most unusual is that it will be bright enough for small backyard telescopes to glimpse as it sweeps past our planet.
Also making it of interest to astronomers is the fact that it belongs to a group of 551 known near-Earth asteroids that have the potential for impact sometime in the future. Luckily, 2004 BL86 doesn't seem to have our number just yet.
"Monday, January 26, will be the closest asteroid 2004 BL86 will get to Earth for at least the next 200 years," said Don Yeomans, manager of NASA's Near Earth Object Program Office at the Jet Propulsion Laboratory in Pasadena, California, in a statement.
"And while it poses no threat to Earth for the foreseeable future, it's a relatively close approach by a relatively large asteroid, so it provides us a unique opportunity to observe and learn more."
See for Yourself
Asteroid 2004 BL86 was discovered on January 30, 2004, by a telescope of the Lincoln Near Earth Asteroid Research (LINEAR) survey in White Sands, New Mexico. Now backyard sky-watchers can enjoy a chance to find it.
This will be a rare opportunity to see a bright flyby of a potentially hazardous asteroid from your backyard. For several hours on Monday, 2004 BL86 will reach a visual brightness of magnitude 9. That means small telescopes and possibly even large binoculars will reveal the asteroid—as long as you know where to look.
The asteroid will travel through the constellations Hydra and Cancer in the south-southeastern evening sky and will glide just to the right of a bright celestial guidepost, the planet Jupiter. Between 10 p.m. and 12 a.m. EST, it will be making a close pass of the famed Beehive star cluster.
"I may grab my favorite binoculars and give it a shot myself," added Yeomans.
The timing and location of the closest approach means the best views will be from North America, South America, Europe, and Africa.
You will have to act quickly, though, because 2004 BL86 will be moving at a fast clip on Monday, zipping through Earth's skies at 2.7 degrees per hour, which is equal to almost five and half times the width of the disk of the full moon. Confirmation of its observation will come courtesy of it moving clearly across a background of fixed stars.
If you do get clouded out or don't have a scope handy, never fear: You can catch a live webcast of the cosmic encounter provided by the Virtual Telescope Project.
Let us know if you manage to snag a view of this cosmic interloper in your skies.