In 2020 a crew led by European Southern Observatory (ESO) astronomers reported the closest black gap to Earth, situated simply 1000 light-years away within the HR 6819 system. However the outcomes of their examine had been contested by different researchers, together with by a global crew primarily based at KU Leuven, Belgium. In a paper printed at present, these two groups have united to report that there’s in reality no black gap in HR 6819, which is as a substitute a “vampire” two-star system in a uncommon and short-lived stage of its evolution.
The unique examine on HR 6819 acquired important consideration from each the press and scientists. Thomas Rivinius, a Chile-based ESO astronomer and lead writer on that paper, was not stunned by the astronomy group’s reception to their discovery of the black gap. “Not solely is it regular, but it surely must be that outcomes are scrutinised,” he says, “and a outcome that makes the headlines much more so.”
Rivinius and his colleagues had been satisfied that the most effective rationalization for the information they’d, obtained with the MPG/ESO 2.2-metre telescope, was that HR 6819 was a triple system, with one star orbiting a black gap each 40 days and a second star in a a lot wider orbit. However a examine led by Julia Bodensteiner, then a PhD pupil at KU Leuven, Belgium, proposed a distinct rationalization for a similar information: HR 6819 is also a system with solely two stars on a 40-day orbit and no black gap in any respect. This different state of affairs would require one of many stars to be “stripped,” that means that, at an earlier time, it had misplaced a big fraction of its mass to the opposite star.
“We had reached the restrict of the present information, so we needed to flip to a distinct observational technique to determine between the 2 situations proposed by the 2 groups,” says KU Leuven researcher Abigail Frost, who led the brand new examine printed at present in Astronomy & Astrophysics.
To unravel the thriller, the 2 groups labored collectively to acquire new, sharper information of HR 6819 utilizing ESO’s Very Massive Telescope (VLT) and Very Massive Telescope Interferometer (VLTI). “The VLTI was the one facility that may give us the decisive information we wanted to differentiate between the 2 explanations,” says Dietrich Baade, writer on each the unique HR 6819 examine and the brand new Astronomy & Astrophysics paper. Because it made no sense to ask for a similar commentary twice, the 2 groups joined forces, which allowed them to pool their sources and information to search out the true nature of this method.
“The situations we had been in search of had been relatively clear, very completely different and simply distinguishable with the suitable instrument,” says Rivinius. “We agreed that there have been two sources of sunshine within the system, so the query was whether or not they orbit one another intently, as within the stripped-star state of affairs, or are far aside from one another, as within the black gap state of affairs.”
To differentiate between the 2 proposals, the astronomers used each the VLTI’s GRAVITY instrument and the Multi Unit Spectroscopic Explorer (MUSE) instrument on ESO’s VLT.
“MUSE confirmed that there was no vibrant companion in a wider orbit, whereas GRAVITY’s excessive spatial decision was capable of resolve two vibrant sources separated by solely one-third of the space between the Earth and the Solar,” says Frost. “These information proved to be the ultimate piece of the puzzle, and allowed us to conclude that HR 6819 is a binary system with no black gap.”
“Our greatest interpretation thus far is that we caught this binary system in a second shortly after one of many stars had sucked the ambiance off its companion star. This can be a widespread phenomenon in shut binary techniques, generally known as “stellar vampirism” within the press,” explains Bodensteiner, now a fellow at ESO in Germany and an writer on the brand new examine. “Whereas the donor star was stripped of a few of its materials, the recipient star started to spin extra quickly.”
“Catching such a post-interaction part is extraordinarily troublesome as it’s so brief,” provides Frost. “This makes our findings for HR 6819 very thrilling, because it presents an ideal candidate to review how this vampirism impacts the evolution of huge stars, and in flip the formation of their related phenomena together with gravitational waves and violent supernova explosions.”
The newly fashioned Leuven-ESO joint crew now plans to watch HR 6819 extra intently utilizing the VLTI’s GRAVITY instrument. The researchers will conduct a joint examine of the system over time, to raised perceive its evolution, constrain its properties, and use that information to be taught extra about different binary techniques.
As for the seek for black holes, the crew stays optimistic. “Stellar-mass black holes stay very elusive owing to their nature,” says Rivinius. “However order-of-magnitude estimates counsel there are tens to a whole bunch of hundreds of thousands of black holes within the Milky Means alone,” Baade provides. It’s only a matter of time till astronomers uncover them.
This analysis was offered within the paper “HR 6819 is a binary system with no black gap: Revisiting the supply with infrared interferometry and optical integral discipline spectroscopy” to seem in Astronomy & Astrophysics.
It has acquired funding from the European Analysis Council (ERC) beneath the European Union’s Horizon 2020 analysis and innovation programme (grant settlement quantity 772225: MULTIPLES; PI: Hugues Sana).
The crew consists of A. J. Frost (Institute of Astronomy, KU Leuven, Belgium [KU Leuven]), J. Bodensteiner (European Southern Observatory, Garching, Germany [ESO]), Th. Rivinius (European Southern Observatory, Santiago, Chile [ESO Chile]), D. Baade (ESO), A. Mérand (ESO), F. Selman (ESO Chile), M. Abdul-Masih (ESO Chile), G. Banyard (KU Leuven), E. Bordier (KU Leuven, ESO Chile), Ok. Dsilva (KU Leuven), C. Hawcroft (KU Leuven), L. Mahy (Royal Observatory of Belgium, Brussels, Belgium), M. Reggiani (KU Leuven), T. Shenar (Anton Pannekoek Institute for Astronomy, College of Amsterdam, The Netherlands), M. Cabezas (Astronomical Institute, Academy of Sciences of the Czech Republic, Prague, Czech Republic [ASCR]), P. Hadrava (ASCR), M. Heida (ESO), R. Klement (The CHARA Array of Georgia State College, Mount Wilson Observatory, Mount Wilson, USA) and H. Sana (KU Leuven).