Just under two weeks from now, on Monday, Jan. 26, the 1/3-mile (0.5-km) -wide potentially hazardous asteroid 357439 (2004 BL86) will pass by Earth at 3.1 lunar distances, or 739,680 miles (1,190,400 km). While this may sound like a long way off, in the grand scheme of things it’s still a close pass… especially for an object as wide as the Burj Khalifa is high!
Don’t worry though – there’s no risk of an impact from 2004 BL86. It will go sailing by harmlessly at a relative 15.6 km/s velocity (that is, 34,900 mph) back out into the Solar System, just another rocky reminder that Earth is definitely not alone out here.
And, thankfully, astronomers will be watching.
“Monday, January 26 will be the closest asteroid 2004 BL86 will get to Earth for at least the next 200 years,” said Don Yeomans of NASA’s Near Earth Object Program Office at the Jet Propulsion Laboratory in Pasadena, California. “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.”
Yeomans will soon be retiring from his position as NEO program manager after 16 years.
NASA’s Deep Space Network antenna at Goldstone, California, and the Arecibo Observatory in Puerto Rico will attempt to acquire science data and radar-generated images of the asteroid during the days surrounding its closest approach to Earth.
“When we get our radar data back the day after the flyby, we will have the first detailed images,” said radar astronomer Lance Benner of JPL, the principal investigator for the Goldstone radar observations of the asteroid. “At present, we know almost nothing about the asteroid, so there are bound to be surprises.”
Asteroid 2004 BL86 was initially discovered on Jan. 30, 2004 by a telescope of the Lincoln Near-Earth Asteroid Research (LINEAR) survey in White Sands, New Mexico. This will be the closest pass of an object its size until 2027.
While classified as a PHA (potentially hazardous asteroid), that doesn’t mean 2004 BL86 will hit Earth. PHAs are classified as having “a minimum orbit intersection distance of 0.05 AU or less and an absolute magnitude (H) of 22.0 or less.” Still, they are monitored closely whenever possible to fine-tune the knowledge of their orbits and physical characteristics.
2004 BL86 will be visible from Earth to amateur astronomers through small telescopes or strong binoculars, peaking at about +9 magnitude. (Ephemerides here.) According to astronomer Scott MacNeill at Frosty Drew Observatory in Charlestown, RI:
“Viewing the asteroid should be easy. The asteroid’s closest point will occur about 11:20 a.m. EST, though visibility will be excellent for U.S. stargazers that night. Passing into the constellation Cancer just after sunset, 2004 BL86 will visibly traverse the constellation Cancer over the course of the night. Additionally, between midnight and 1:00 a.m. EST (Jan 27th), 2004 BL86 will have a visibly close encounter with the fabulous Beehive Star Cluster (Messier 44) in Cancer, passing just to the East of the cluster. This will make it easily identifiable for non-computerized telescopes. Over the course of 10 minutes, the asteroid’s visible position in a telescope will chance dramatically, moving almost the diameter of the full Moon among fixed stars. Look for the star that changes position over the course of a minute, that’s the asteroid.”
Below is a map showing the path of BL86 as it reaches its brightest (+9 mag) appearance on the night of Jan. 26-27 (via Sky & Telescope):
There will also be a live viewing event online by the Virtual Telescope Project here on the 26th.