In 2020 a crew led by European Southern Observatory (ESO) astronomers reported the closest black gap to Earth, positioned simply 1000 light-years away within the HR 6819 system. However the outcomes of their research have been contested by different researchers, together with by a world crew based mostly at KU Leuven, Belgium. In a paper printed at this time, these two groups have united to report that there’s actually no black gap in HR 6819, which is as an alternative a “vampire” two-star system in a uncommon and short-lived stage of its evolution.
The unique research on HR 6819 obtained vital consideration from each the press and scientists. Thomas Rivinius, a Chile-based ESO astronomer and lead creator on that paper, was not shocked by the astronomy group’s reception to their discovery of the black gap. “Not solely is it regular, however it must be that outcomes are scrutinised,” he says, “and a outcome that makes the headlines much more so.”
Rivinius and his colleagues have been satisfied that the very best rationalization for the information that they had, 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 research led by Julia Bodensteiner, then a PhD scholar at KU Leuven, Belgium, proposed a special 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 various situation 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 special observational technique to resolve between the 2 eventualities proposed by the 2 groups,” says KU Leuven researcher Abigail Frost, who led the brand new research printed at this time in Astronomy & Astrophysics.
To resolve the thriller, the 2 groups labored collectively to acquire new, sharper information of HR 6819 utilizing ESO’s Very Giant Telescope (VLT) and Very Giant Telescope Interferometer (VLTI). “The VLTI was the one facility that will give us the decisive information we wanted to differentiate between the 2 explanations,” says Dietrich Baade, creator on each the unique HR 6819 research and the brand new Astronomy & Astrophysics paper. Because it made no sense to ask for a similar statement 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 eventualities we have been searching for have been somewhat clear, very totally different and simply distinguishable with the appropriate 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 carefully, as within the stripped-star situation, or are far other than one another, as within the black gap situation.”
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 vivid companion in a wider orbit, whereas GRAVITY’s excessive spatial decision was capable of resolve two vivid sources separated by solely one-third of the gap 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 to date is that we caught this binary system in a second shortly after one of many stars had sucked the environment off its companion star. It is a frequent phenomenon in shut binary methods, typically known as “stellar vampirism” within the press,” explains Bodensteiner, now a fellow at ESO in Germany and an creator on the brand new research. “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 section 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 large 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 carefully utilizing the VLTI’s GRAVITY instrument. The researchers will conduct a joint research of the system over time, to raised perceive its evolution, constrain its properties, and use that information to be taught extra about different binary methods.
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 lots of of thousands and thousands of black holes within the Milky Manner alone,” Baade provides. It’s only a matter of time till astronomers uncover them.
This analysis was introduced 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 look in Astronomy & Astrophysics.
It has obtained funding from the European Analysis Council (ERC) underneath 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).