Asteroid 2004 BL86 makes close pass by Earth; closest pass of large asteroid for the next 13 years

Sunday, January 25, 2015, 9:30 AM - Heads up, astronomers! On Monday, half-kilometre wide asteroid 2004 BL86 will be making a close flyby of Earth, and this will be your last chance until 2027 to see such a large object fly past us so close.

Asteroid 2004 BL86, discovered on the 30th of January, 2004 by the Lincoln Near-Earth Asteroid Research (LINEAR) project, is certainly no stranger to Earth. Shortly after its discovery, astronomers plotted out its orbit and found that it has been swinging past our planet - coming within about half an astronomical unit (half the distance between the Earth and the Sun, or about 75 million kilometres) - at least once every decade or so.

However, its scheduled flyby on January 26, 2015 is a bit more special than its other visits.

"Monday, January 26 will be the closest asteroid 2004 BL86 will get to Earth for at least the next 200 years," veteran asteroid hunter Don Yeomans, the manager of NASA's Near Earth Object Program Office, said in a Jet Propulsion Laboratory (JPL) press release. "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."

Credit: NASA/JPL-Caltech

Right around midday on the day in question, this huge hunk of space rock, estimated at between 400 and 1,000 metres wide, will come to within about 1.2 million kilometres of Earth, or a little over three times the distance to the Moon. As Yeomans says, at that distance, the asteroid poses no risk, but it's an incredible opportunity for astronomers.

According to JPL, as 2004 BL86 flys by, two giant antennas - one at NASA's Goldstone Deep Space Communications Complex and the one at the Arecibo Observatory in Puerto Rico - will track the asteroid and bombard it with microwaves to get radar images and collect science data to learn more about its exact size and composition.

"When we get our radar data back the day after the flyby, we will have the first detailed images," said Lance Benner, a JPL radio astronomer and principal investigator for the observations made by Goldstone, according to the press release. "At present, we know almost nothing about the asteroid, so there are bound to be surprises."

In Case You Missed It: When asteroid nicknamed 'The Beast' flew by Earth last June, we paused to reflect on exactly how many asteroids there are out there.

A chance to see it for yourself

With an object this big flying by this close, it offers amateur astronomers and space enthusiasts a chance to check it out for themselves.

To find asteroid 2004 BL86, you can use a good pair of binoculars or a backyard telescope, as long as you're reasonably far away from any large sources of light pollution (like cities) and the skies are fairly clear. The best time is after midnight, since the moon will have set by then, and viewing conditions will be best.

As the animation below shows, the asteroid will be above the eastern horizon, and will track across the constellation Cancer throughout the night, setting by daybreak.

The track of asteroid 2004 BL86 on January 26-27, 2015. Credit: Stellarium

"I may grab my favorite binoculars and give it a shot myself," Yeomans, who is retiring from his position in the NASA NEO office after 16 years, said in the press release. "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 makes me want to look up."

If the weather doesn't cooperate with your attempt to view the asteroid, there are other ways of watching this remarkable event.

The Slooh Space Camera will be tracking its passage midday Monday, presenting views of 2004 BL86 from telescopes on the dark side of the planet. Their show begins live at 1600 UTC (11 am EST), and can be viewed, for free, on their website (click here).

Closest until 2027

Not only is this the closest pass of 2004 BL86 in 200 years, but it's also going to be more than 13 years from now before another asteroid of comparable size gets this close to Earth. In August of 2027, asteroid 1999 AN10 - at least 800 metres wide and tipping the cosmic scales at nearly 3 billion metric tons - comes to within around twice the distance of the Moon.

So, if you miss this opportunity, it's going to be a long wait before the next one comes along.