Asteroid Top Spin

An aerial view of Meteor Crater, Arizona. The asteroid 2008 HJ
Credit: Jim Hurley, 1978

A British amateur astronomer has discovered the fastest rotating natural object known in our solar system.

His observations, made using a telescope normally shared by school students and professional scientists, have proved that the newly-discovered asteroid, 2008 HJ is revolving once every 42.7 seconds, classifying it is as a ‘superfast rotator’. His discovery will boost our sparse knowledge of near Earth asteroids and is another successful find for the Faulkes Telescope near-Earth asteroid project.

The astronomer Richard Miles made his exciting discovery on Tuesday 29th April using the Faulkes Telescope South (located at Siding Spring, Australia), which he operated remotely via the Internet from his home in Dorset. Confirmation of his discovery was formally announced by the International Astronomical Union on Thursday 22nd May. The previous record holder was asteroid 2000 DO8, discovered eight years ago and found to rotate once every 78 seconds. The Science and Technology Facilities Council (STFC) was involved in the initial set-up of the Faulkes Telescope Project and continues to provide support.

2008 HJ is the fastest rotating natural object known in the solar system. The asteroid made almost a complete revolution in the time it took to take this picture.
Credit: Dr Richard Miles

This latest discovery is the most recent outcome of a new project to use the Faulkes Telescopes, situated in Hawaii and Australia, to survey the properties of small (<150-metre) near-Earth asteroids. UK schools and colleges have already participated in the project, which in April had an early success having found that asteroid 2008 GP3 rotates once every 11.8 minutes. Asteroid 2008 HJ was only the fourth object observed as part of this study.

The observations suggest that 2008 HJ is a compact stony object some 12m x 24m in size, smaller than a tennis court yet probably having a mass in excess of 5,000 tons. It was moving at almost 45 kilometers per second (more than 100,000 mph) when it hurtled past the Earth in late April. Despite being classified as a "near-Earth asteroid", it came no closer than 1 million km and never posed a threat to our planet.

Dr Paul Roche, the director of the Faulkes Telescope Project at Cardiff University, said: "A discovery like this demonstrates the capabilities of amateur astronomers and school students to produce exciting scientific results if given the right tools. By providing Richard with access to a big telescope we have smashed the previous record, and opened up the search for even faster objects to UK amateur astronomers and school students. This helps to put all that classroom science, maths and IT to real use!"

The observation was made using the Faulkes Telescope in Australia. The aim of the Faulkes Telescope Project is to provide free access to robotic telescopes and a fully supported education program. This image shows one of the Faulkes Telescopes in construction.
Credit: Faulkes Telescope Project

The early success for the Faulkes Telescope near-Earth asteroid project bodes well for the future and should prove especially encouraging to schools, colleges and other amateur astronomers looking to participate. It now appears that the chances of success are high and one challenge will be to find objects spinning even faster than 2008 HJ. Cooperation between all the observing groups, whether they are astronomers or schools students, will be essential if asteroid rotation rates are to be accurately identified.

Dr Petr Pravec, an astronomer at the Ondrejov Observatory (Czech Republic) and an expert in this field, commented: "A period of 42.7 seconds for an asteroid with a size of about 20 meters is perfectly consistent with theory … there may be a significant population of asteroids measuring up to a few tens of metres across, rotating in less than a minute, that have not been observed until now".

Our knowledge of the near-Earth population of small asteroids is very sparse, so schools and others can contribute directly to our understanding of these nearest neighbors of ours. It is believed that most of these objects are probably fragments ejected from collisions between larger bodies which took place some time in the distant past. However, other objects may have originated when the solar nebula was formed over 4.6 billion years ago. Studying near-Earth, small asteroids can thereby yield important information about the early solar system and the formation of planets. Additionally, the information can be used to search for asteroids that could potentially pass within striking distance of the Earth. Even small asteroids can potentially have a profound affect on the Earth’s climate and biosphere if they do impact with our planet.

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