Chelyabinsk Meteoroid tracked back to the Apollo asteroid group

Astronomers at the University of Antioquia, Medellin in Colombia have back-tracked the trajectory of the Chelyabinsk meteoroid and have concluded that it was from the Apollo asteroid group which regularly intersect with Earth’s orbit. The Apollo group contains at least 5,000 asteroids and more than 240 of these are over 1 km in size. The largest known Apollo asteroid is 1866 Sisyphus, with a diameter of about 10 km.

The Chelyabinsk meteoroid crossed from northeast to southwest on February 15th at an angle of 20 degrees above the horizontal at a speed of about 18 km/s. It is estimated to have been about 17-m in size with an estimated mass of between 7,000 and 10,000 tonnes. It exploded at 03:20:26 GMT over 55° 10′ N, 61° 25′ E at an altitude of 15 to 20 kilometers (9.3 to 12.4 miles) with a force of 500 kilotons – the equivalent of 30 Hiroshima atomic bombs.

The astronomers have published their findings:

A preliminary reconstruction of the orbit of the Chelyabinsk Meteoroid

by Jorge I. Zuluaga, Ignacio Ferrin

http://arxiv.org/abs/1302.5377 (abstract)

complete paper (pdf)

Reconstructing the orbit

The Chelyabinsk Meteor Friday 15th Feb. 2013: image from http://www.sott.net

BBC:…. Astronomers have traced the origin of a meteor that injured about 1,000 people after breaking up over central Russia earlier this month.

Using amateur video footage, they were able to plot the meteor’s trajectory through Earth’s atmosphere and then reconstruct its orbit around the Sun. Using the footage and the location of an impact into Lake Chebarkul, Jorge Zuluaga and Ignacio Ferrin, from the University of Antioquia in Medellin were able to use simple trigonometry to calculate the height, speed and position of the rock as it fell to Earth.

To reconstruct the meteor’s original orbit around the Sun, they used six different properties of its trajectory through Earth’s atmosphere. Most of these are related to the point at which the meteor becomes bright enough to cast a noticeable shadow in the videos.

…. The results suggest the meteor belongs to a well known family of space rocks – known as the Apollo asteroids – that cross Earth’s orbit.

Of about 9,700 near-Earth asteroids discovered so far, about 5,200 are thought to be Apollos. Asteroids are divided into different groups such as Apollo, Aten, or Amor, based on the type of orbit they have.

MIT Technology Review: 

“According to our estimations, the Chelyabinski meteor started to brighten up when it was between 32 and 47 km up in the atmosphere,” say Zuluaga and Ferrin, who estimate the velocity at between 13 km/s and 19 km/s relative to Earth.

They then calculated the likely orbit by plugging these figures into a piece of software developed by the US Naval Observatory called NOVAS, the Naval Observatory Vector Astrometry. This allowed them to include the gravitational influence on the rock of the Moon and the 8 major gravitational bodies in the Solar System.

 

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