Weekly Space Hangout: March 9, 2022 — HR 6819: Black Hole? Vampire 2-Star System? Dr. Abigail Frost Explains

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On March 2, 2022, the European Southern Observatory (ESO) reported that the HR 6819 system, believed to be the home of the closest black hole to earth, is, in fact, “a ‘vampire’ two-star system in a rare and short-lived stage of its evolution.” HR 6819, just 1000 light-years from earth, does not include a black hole. The study was led by Dr. Abigail Frost from KY Leuven, and we are extremely please to welcome Dr. Frost to the Weekly Space Hangout tonight.

Dr. Abigail Frost is a postdoctoral research associate at KU Leuven, a research university in Belgium. Born and raised in the UK, her journey into astrophysics started with her master’s studies at the University of Exeter (UK). She then did her PhD at the University of Leeds before moving to Belgium to start her academic career. Her research focuses on studying the most influential stars in our Universe – massive stars. Using multiple observing techniques and modelling, she investigates how these stars form and how stars that exist in pairs (or even greater groups) evolve and how their companion stars can affect that evolution.

You can learn more about Abigail by visiting her website. You can also follow her on LinkedIn as well as on Twitter (@AstroDrFrost).

Left Image: This artist’s impression shows the orbits of the objects in the HR 6819 triple system. This system is made up of an inner binary with one star (orbit in blue) and a newly discovered black hole (orbit in red), as well as a third object, another star, in a wider orbit (also in blue).

The team originally believed there were only two objects, the two stars, in the system. However, as they analysed their observations, they were stunned when they revealed a third, previously undiscovered body in HR 6819: a black hole, the closest ever found to Earth. The black hole is invisible, but it makes its presence known by its gravitational pull, which forces the luminous inner star into an orbit. The objects in this inner pair have roughly the same mass and circular orbits.

The observations, with the FEROS spectrograph on the 2.2-metre telescope at ESO’s La Silla, showed that the inner visible star orbits the black hole every 40 days, while the second star is at a large distance from this inner pair. Credit: ESO/L. Calçada Original may be viewed here: https://www.eso.org/public/images/eso2007a/

Right Image: This chart shows the location of HR 6819 in the constellation of Telescopium. This map shows most of the stars visible to the unaided eye under good conditions and the system itself is marked with a red circle. The two stars in HR 6819 can be viewed from the southern hemisphere on a dark, clear night without binoculars or a telescope. Credit: ESO, IAU and Sky & Telescope. Original may be viewed here: https://www.eso.org/public/images/eso2007b/

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