The Rock passes by Earth
An asteroid the size of Gibraltar passed by the Earth on 19 April, and will continue to grow in brightness for several nights giving a fantastic observing opportunity.
The asteroid passed 1.8 million km from Earth
Credit: EAAE Astronomy
An asteroid the size of Gibraltar made its closest pass of the Earth last night at 12:24 UTC. 2014 JO25, nicknamed ‘The Rock’, came within 4.6 lunar distances of Earth, the closest pass by such a sized asteroid in 13 years. Over the next few nights, the asteroid will continue to grow in brightness, giving a spectacular opportunity to glimpse the asteroid through a telescope.
The asteroid is between 650m and 1.4 km in size, and was first spotted in 2014 by Catalina Sky Survey. Its origin is currently unknown, however it is an exceptionally bright object with an albedo of 0.25. It has a highly elliptical orbit that carries its path within the orbit of Mercury before swining out again as far as Jupiter.
The orbital path of asteroid 2014 JO25. Credit: NASA
Though there is no risk of the asteroid colliding with Earth on this pass, astronomers are using its proximity to study the asteroid in close detail. Several observing campaigns are already in progress in the hopes of ascertaining the asteroid's origin and composition.
The Rock is bright enough that amateur scopes will be able to observe it. At its brightest the asteroid will be +10.7 mag, meaning it will require at least a 4-inch aperture scope to see it. The easiest way to track the asteroid is to focus on a star that it will pass by ahead of time and wait for it to appear in the eyepiece. It should appear like a star moving slowly, but perceptively, across the field of view. The asteroid will pass two full moon widths west of beta Comae Berenices at 3am BST on 20 April. To track the asteroid's path more precisely, you can use the Asteroid Ephemeris Service provided by the International Astronomical Union.
However, if clouds should deny you or you do not have access to a telescope there are several livestream services available to watch the asteroid as it goes past:
Slooh, 19 April 2017, 23:00 -23:30 UTC