Asteroid 2004 BL86 visible in your telescope


Sky map showing the track of asteroid 2004 BL86 across the evening sky. Image credit:, made with Chris Marriott’s SkyMap program.

In our previous article we already introduced you to a big asteroid that is coming into our neighborhood soon: Asteroid 2004 BL86 will pass by at approximately 3.1 lunar distances (or 1.2 million kilometers). Thanks to its size (somewhere around 680m in diameter) the asteroid will even be visible through small telescopes and maybe even through large binoculars.

The asteroid will pass closest to Earth on the evening of Monday the 26th of January. When it does it will be the largest asteroid to approach the direct neighborhood of Earth for quite a long time. The next one is projected to be asteroid 1999 AN10, that will visit in 2027.

Trajectory of 2004 BL86 when it passes by the Earth. Image credit: NASA/JPL-Caltech.

Due to the large size of the asteroid it is expected to reach a magnitude of +9.0 and will be best visible for observers in the Americas, Europe and Africa. It will move across the evening sky at a noticable rate, so if you follow it with a telescope you should be able to see it move through your field of view. It will move at approximately 2 degrees per hour(four Moon diameters).

To track the asteroid you will need a sky map such as this image to find it in the sky. Note that the position of the asteroid might vary slightly depending on where you are on the Earth. You can also use software such as Starry Night, Guide, MegaStar and others to generate such a map and find the current position of asteroid. For this you can find the latest orbital data of the object here.

Next to all the amateur astronomers that will surely be trying to find the asteroid in their telescopes, NASA is also going to have a look using the big radar observatories at Arecibo in Puerto Rico and Goldstone, California. They will try to bounce microwaves of the surface of the asteroid to get a clearer picture of how it actually looks.