Nasa is tracking an asteroid dubbed the "Great Pumpkin" that will fly past Earth on Halloween. Officially named Asteroid 2015 TB145, it is flying so close that scientists are hoping to observe it in "unprecedented" levels of detail.
What do we know about the Great Pumpkin?
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It is estimated to be 400 metres wide and is being tracked with several optical observatories and radar equipment. It was discovered on 10 October by the University of Hawaii's Panoramic Survey Telescope and Rapid Response System, which is part of the Nasa-funded Near-Earth Object Observation (NEOO) programme. Sometimes called "Spaceguard", the NEOO programme keeps a watch on the skies, hunting for asteroids that might hit the planet and predicting their paths through space.
When will it fly past?
The asteroid is due to fly past Earth on October 31 at 10.05am PDT – 5.05pm in the UK.
Are we in danger?
No. Nasa describes it as a "close pass" but says the Great Pumpkin will travel at a "safe distance slightly further than the moon's orbit". According to Paul Chodas, manager of the Centre for Near Earth Object Studies in California, it will be no closer than about 300,000 miles at its nearest point of approach. "Even though that is relatively close by celestial standards, it is expected to be fairly faint, so night-sky Earth observers would need at least a small telescope to view it," says Chodas. Its "gravitational influence" is so small that it will have "no detectable effect on the moon or anything here on Earth, including our planet's tides or tectonic plates", says Nasa.
Why is it important?
Its close approach and size suggests it will be "one of the best asteroids for radar imaging we'll see for several years", says Lance Benner, who leads Nasa's asteroid radar research programme. "We plan to test a new capability to obtain radar images with two-metre resolution for the first time and hope to see unprecedented levels of detail," he says. With radar images as fine as two metres per pixel, Nasa says it should be able to discover a "wealth of detail about the object's surface features, shape, dimensions and other physical properties". The next closest known approach by an object this large is expected to be in August 2027, when asteroid 1999 AN10 that's around 800 metres in size is due to pass the Earth from about 238,000 miles away.
