Irish astronomers measure star diameters

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A team of astronomers, including researchers from NUIG, UCD and Cork IT have measured the angular diameter of stars using VERITAS telescopes.

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16 April 2019 | 0

Astronomers at NUI Galway, UCD and Cork IT have, for the first time used the VERITAS gamma-ray telescope to measure the angular diameter of stars.

The collaboration revealed the smallest known star size, located 700 light years from Earth that is shown to be 2.17 times the diameter of our sun.

As part of an international team, Irish researchers at the Whipple Observatory in Arizona found success with a new method.

Gamma rays entering the Earth’s atmosphere produce short flashes of visible light. Through measuring these, VERITAS can detect high-energy gamma radiation from exotic objects in space.

Dr Gary Gillanders of the School of Physics, Centre for Astronomy at NUI Galway, says “Stars are so far away from us that they appear as points of light in the sky. Their diameters are usually estimated indirectly using measurements of temperature and brightness.”

The team were successful in using asteroid occultation, the measurement of a shadow that has been cast on earth from an asteroid crossing between us and a star.

The type of telescope used by VERTIAS had not achieved such a significant result in the past so this outcome could significantly pave the way for the future of direct measurement of stars.

Amy Joyce, a former MSc student at NUI Galway was part of the observing crew now based at the European Space Agency in Madrid, said that the telescope was the right tool for the job, “The occultation is like a mini solar eclipse, although it is extremely faint and only lasts a few seconds, VERITAS is an ideal instrument to detect it.”

“Normally we use VERITAS to observe objects like the supermassive black hole in M87, recently imaged by the Event Horizon Telescope.” Says Dr Mark Lang of the School of Physics, Centre for Astronomy at NUI Galway. “Now we have shown that VERITAS can make other types of measurements”.

The study was led by Dr Michael Daniel of the Harvard-Smithsonian Centre for Astrophysics and Dr Tarek Hassan of German physics institute DESY.

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