You may think that the distance of 745,000 miles (1.2 million kilometers) when the asteroid is closest to Earth is vast, but on the astronomical scale, particularly for an asteroid estimated from its reflected brightness to be about 500 meters in diameter (0.5 kilometers), it is very close, the closest for the asteroid in the next 200 years.
The flyby will also be the closest for any space rock in its size category until asteroid 1999 AN10 passes in 2027, according to NASA. AN10, estimated to be about 0.6 miles in diameter, will pass perilously closer to Earth, 19,000 miles at closest approach.
Don Yeoman, retiring head of NASA’s Near-Earth Object Program Office at the Jet Propulsion Laboratory (JPL) in Pasadena, said, “Monday, January 26, will be the closest asteroid 2004 BL86 will get to Earth for at least the next 200 years. 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.”
NASA scientists and technicians will be using the Deep Space Network antenna at Goldstone, California and the Arecibo Observatory in Puerto Rico, to collect data and generate radar images of the asteroid as it passes close to Earth.
“When we get our radar data back the day after the flyby, we will have the first detailed images. At present, we know almost nothing about the asteroid, so there are bound to be surprises,” said NASA’s radar astronomer Lance Benner, who is leading the radar observation team at Goldstone.
In its present position as it orbits the sun, the asteroid is visible only to astronomers in the southern hemisphere equipped with large telescopes. But at closest approach around Jan. 26, it will become visible also to astronomers in the northern hemisphere.
At a maximum visual magnitude of 9, it will never become bright enough to be seen with the naked eye. But after nightfall on Jan. 26, both professional and amateur astronomers will be able to observe it as a faint star in the constellation Cancer, through telescopes with aperture of at least 4 inch (10 cm).
It will also be visible as a faint star on big binoculars.
Yeoman said, “I may grab my favorite binoculars and give it a shot myself. Asteroids are something special. Not only did asteroids provide Earth with the building blocks of life and much of its water, but in the future, they will become valuable resources for mineral ores and other vital natural resources. They will also become the fueling stops for humanity as we continue to explore our solar system. There is something about asteroids that make me want to look up.”
Real-time images and commentary on the flyby will be available online at The Virtual Telescope Project 2.0, beginning at 2:30 p.m. EST.
According to Earthsky, observers in the Americas, Europe and Africa will have the best opportunity to see it on the night of Jan. 26, near the constellation Cancer. Although it will appear to be moving slowly across the sky compared with meteors and shooting stars, it will actually be travelling in its orbit around the sun at a speed of about 35,057 miles per hour (56,420 km/h).
Asteroid 2004 BL86 was first discovered on Jan. 30, 2004 at the Lincoln Near-Earth Asteroid Research (LINEAR) survey in White Sands, New Mexico.
NASA’s JPL-managed Near-Earth Object Program, popularly called “Spaceguard,” tracks and characterizes asteroids and comets to determine their closest approach and assess their potential danger to our planet.
