Space and Physics

Enormous Asteroid Discovered Last Week Will Whizz Past Earth On Halloween


Dr. Alfredo Carpineti

Senior Staff Writer & Space Correspondent

clockOct 20 2015, 23:42 UTC
3075 Enormous Asteroid Discovered Last Week Will Whizz Past Earth On Halloween
Asteroid 253 Mathilde, measuring about 50 kilometers (30 miles) across, by NASA via Wikimedia Commons.

Two asteroids will pass by Earth this Halloween. The first is 2009 FD, a peculiarly dark asteroid, which will make its closest approach on October 29. The second, 2015 TB145, will fly-by on Halloween. The two asteroids won't be visible to the naked eye, even at their closest approach. The astronomical events have been announced in NASA's Goldstone Radar Observation Plan.


2009 FD will approach within 6,194,000 km of Earth, about 16.3 times further away than the Moon. The asteroid was discovered in February 2009, a month before its closest recorded approach to Earth on March 27, 2009, at a distance of 624,100 km. 2015 TB145 will pass about 500,000 km from Earth, just beyond the lunar orbit.

2009 FD has been tracked by several instruments since its discovery. It was first estimated to be 130 meters in size by NASA’s Near Earth Program. A better estimate for its size came from NASA’s NEOWISE, which gave a value of 470 meters, although this is considered an upper limit.

2015 TB145 was discovered just over a week ago by the Pan-STARRS I telescope in Hawaii, and it has an estimated size of 320 meters. The passing of 2015 TB145 will be the closest approach by something this large until asteroid August 2027, when 1999 AN10 will pass within one lunar distance (380,000 km). NASA has given these objects a value of 1 on the Torino Scale, which is the value assigned to non-dangerous asteroids. 

The Torino scale is an integer 0-10 scale used to communicate the risk of an impact to the general public. So far, no object has been rated over 4.


Both objects will be tracked and studied by the Goldstone Observatory in California. 

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