These ‘pebbles’ detected for 1st time: crucial link in building planets. Since1990s, astronomers have found both disks of gas and dust, and nearly 2000 fully formed planets, but the intermediate stages of formation are harder to detect.
Dr Greaves and Dr Anita Richards from Manchester University used e-MERLIN array of radio telescopes centred on Jodrell Bank, Cheshire, and that stretches across England in an interferometer, mimicking resolution of a single large telescope. They observed the star DG Tauri, a youthful star just 2.5 million years old and 450 light years away in constellation of Taurus. Looking at radio wavelengths, they discovered a faint glow characteristic of rocks in orbit around the newly formed star.
An artist’s impression of the belt of ‘pebbles’ in orbit around the star DG Tauri. The inset is a close up view of a section of the belt. Credit: J. Ilee. Adapted from original work by ESO/L. Calçada/M. Kornmesser, ALMA (ESO/NAOJ/NRAO)/L. Calçada (ESO).
“This was the first time for this project that we folded in data from the 76m-diameter Lovell Telescope at Jodrell Bank, which is the heart of the e-MERLIN array. We knew DG Tauri had a jet of hot gas flowing off its poles – a beacon for stars still in the process of forming – so we had an idea of what to look for.”….”It was a real surprise to also see a belt of pebbles, with only a fraction of the data we hope to acquire. With the 4-fold increase in radio bandwidth we are now working on, we hope to get similar images for a whole zoo of other young stars.”…. “The extraordinarily fine detail we can see with the e-MERLIN telescopes was the key to this discovery.”
e-MERLIN observations were made at a wavelength of 4.6 cm (~1/3 of that used in microwave ovens). To give off these radio waves, rocky chunks at > 1cm in size are needed, and the shape of the belt confirms the rocks as the source of the radio waves.
The e-MERLIN network of up to seven radio telescopes is linked by an optical fibre network to a control centre at Jodrell Bank. They operate as a single telescope with a diameter of 217 kilometres, producing extremely sharp views of the radio universe. Credit: University of Manchester’s School of Physics & Astronomy and its Jodrell Bank Observatory
“Long wavelength data, such these fantastic e-MERLIN results, will be essential in constraining the next generation of computer models of discs around young stars. Having an accurate idea of the location and amount of the centimetre-sized material in the disc will bring us closer to a consistent picture of how planets may eventually form.”
Greaves leads PEBBLeS – the Planet Earth Building Blocks Legacy e-MERLIN Survey. By imaging rocky belts of many stars, they will look for clues to how often planets form, and where, around stars that will evolve into future suns like our own. The ultimate aim is to zoom in and see ‘extrasolar Earths’ being born, 5X closer in to their host stars than Jupiter’s orbit. Upgrades to e-MERLIN’s capabilities in the next few years, as well as the construction of the new Square Kilometre Array (with its HQ at Jodrell Bank), make this a real possibility.
http://www.ras.org.uk/news-and-press/2656-astronomers-see-pebbles-poised-to-make-planets
An e-MERLIN map of the star DG Tauri. The yellow and red areas show what is thought to be a ring of pebble-sized clumps in orbit around the star. Credit: J. Greaves / A. Richards / JCBA
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