A new report from the European Southern Observatory (ESO):

Most massive stellar black hole in our galaxy found

Astronomers have identified the most massive stellar black hole yet discovered in the Milky Way galaxy. This black hole was spotted in data from the European Space Agency’s Gaia mission because it imposes an odd ‘wobbling’ motion on the companion star orbiting it. Data from the European Southern Observatory’s Very Large Telescope (ESO’s VLT) and other ground-based observatories were used to verify the mass of the black hole, putting it at an impressive 33 times that of the Sun.

Stellar black holes are formed from the collapse of massive stars and the ones previously identified in the Milky Way are on average about 10 times as massive as the Sun. Even the next most massive stellar black hole known in our galaxy, Cygnus X-1, only reaches 21 solar masses, making this new 33-solar-mass observation exceptional [1].

Remarkably, this black hole is also extremely close to us — at a mere 2000 light-years away in the constellation Aquila, it is the second-closest known black hole to Earth. Dubbed Gaia BH3 or BH3 for short, it was found while the team were reviewing Gaia observations in preparation for an upcoming data release.

“No one was expecting to find a high-mass black hole lurking nearby, undetected so far,”

says Gaia collaboration member Pasquale Panuzzo, an astronomer from the National Centre for Scientific Research (CNRS) at the Observatoire de Paris – PSL, France.

“This is the kind of discovery you make once in your research life.”

To confirm their discovery, the Gaia collaboration used data from ground-based observatories, including from the Ultraviolet and Visual Echelle Spectrograph (UVES) instrument on ESO’s VLT, located in Chile’s Atacama Desert [2]. These observations revealed key properties of the companion star, which, together with Gaia data, allowed astronomers to precisely measure the mass of BH3.

Astronomers have found similarly massive black holes outside our galaxy (using a different detection method), and have theorised that they may form from the collapse of stars with very few elements heavier than hydrogen and helium in their chemical composition. These so-called metal-poor stars are thought to lose less mass over their lifetimes and hence have more material left over to produce high-mass black holes after their death. But evidence directly linking metal-poor stars to high-mass black holes has been lacking until now.

Stars in pairs tend to have similar compositions, meaning that BH3’s companion holds important clues about the star that collapsed to form this exceptional black hole. UVES data showed that the companion was a very metal-poor star, indicating that the star that collapsed to form BH3 was also metal-poor — just as predicted.

The research study, led by Panuzzo, is published today in Astronomy & Astrophysics.

“We took the exceptional step of publishing this paper based on preliminary data ahead of the forthcoming Gaia release because of the unique nature of the discovery,”

says co-author Elisabetta Caffau, also a Gaia collaboration member and CNRS scientist from the Observatoire de Paris – PSL. Making the data available early will let other astronomers start studying this black hole right now, without waiting for the full data release, planned for late 2025 at the earliest.

Further observations of this system could reveal more about its history and about the black hole itself. The GRAVITY instrument on ESO’s VLT Interferometer, for example, could help astronomers find out whether this black hole is pulling in matter from its surroundings and better understand this exciting object.

Notes

[1] This is not the most massive black hole in our galaxy — that title belongs to Sagittarius A*, the supermassive black hole at the Milky Way’s centre, which has about four million times the mass of the Sun. But Gaia BH3 is the most massive black hole known in the Milky Way that formed from the collapse of a star.

[2] Aside from UVES on ESO’s VLT, the study relied on data from: the HERMES spectrograph at the Mercator Telescope operated at La Palma (Spain) by Leuven University, Belgium, in collaboration with the Observatory of the University of Geneva, Switzerland; and the SOPHIE high-precision spectrograph at the Observatoire de Haute-Provence – OSU Institut Pythéas.

Links

• Research paper
• Photos of the VLT
• ESA news article on this research
• For journalists: subscribe to receive our releases under embargo in your language
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An Infinity of Worlds:
Cosmic Inflation and the Beginning of the Universe

The latest report from the European Southern Observatory (ESO):

Beautiful nebula, violent history:
clash of stars solves stellar mystery

When astronomers looked at a stellar pair at the heart of a stunning cloud of gas and dust, they were in for a surprise. Star pairs are typically very similar, like twins, but in HD 148937, one star appears younger and, unlike the other, is magnetic. New data from the European Southern Observatory (ESO) suggest there were originally three stars in the system, until two of them clashed and merged. This violent event created the surrounding cloud and forever altered the system’s fate.

“When doing background reading, I was struck by how special this system seemed,”

says Abigail Frost, an astronomer at ESO in Chile and lead author of the study published today in Science. The system, HD 148937, is located about 3800 light-years away from Earth in the direction of the Norma constellation. It is made up of two stars much more massive than the Sun and surrounded by a beautiful nebula, a cloud of gas and dust.

“A nebula surrounding two massive stars is a rarity, and it really made us feel like something cool had to have happened in this system. When looking at the data, the coolness only increased.”

[Frost say:]

“After a detailed analysis, we could determine that the more massive star appears much younger than its companion, which doesn’t make any sense since they should have formed at the same time!”

The age difference — one star appears to be at least 1.5 million years younger than the other — suggests something must have rejuvenated the more massive star.

Another piece of the puzzle is the nebula surrounding the stars, known as NGC 6164/6165. It is 7500 years old, hundreds of times younger than both stars. The nebula also shows very high amounts of nitrogen, carbon and oxygen. This is surprising as these elements are normally expected deep inside a star, not outside; it is as if some violent event had set them free.

To unravel the mystery, the team assembled nine years’ worth of data from the PIONIER and GRAVITY instruments, both on ESO’s Very Large Telescope Interferometer (VLTI), located in Chile’s Atacama Desert. They also used archival data from the FEROS instrument at ESO’s La Silla Observatory.

“We think this system had at least three stars originally; two of them had to be close together at one point in the orbit whilst another star was much more distant,”

explains Hugues Sana, a professor at KU Leuven in Belgium and the principal investigator of the observations.

“The two inner stars merged in a violent manner, creating a magnetic star and throwing out some material, which created the nebula. The more distant star formed a new orbit with the newly merged, now-magnetic star, creating the binary we see today at the centre of the nebula.”

[Co-author Laurent Mahy, currently a senior researcher at the Royal Observatory of Belgium, adds: ]

“The merger scenario was already in my head back in 2017 when I studied nebula observations obtained with the European Space Agency’s Herschel Space Telescope,”

“Finding an age discrepancy between the stars suggests that this scenario is the most plausible one and it was only possible to show it with the new ESO data.”

This scenario also explains why one of the stars in the system is magnetic and the other is not — another peculiar feature of HD 148937 spotted in the VLTI data.

At the same time, it helps solve a long-standing mystery in astronomy: how massive stars get their magnetic fields. While magnetic fields are a common feature of low-mass stars like our Sun, more massive stars cannot sustain magnetic fields in the same way. Yet some massive stars are indeed magnetic.

Astronomers had suspected for some time that massive stars could acquire magnetic fields when two stars merge. But this is the first time researchers find such direct evidence of this happening. In the case of HD 148937, the merger must have happened recently.

“Magnetism in massive stars isn’t expected to last very long compared to the lifetime of the star, so it seems we have observed this rare event very soon after it happened,”

Frost adds.

ESO’s Extremely Large Telescope (ELT), currently under construction in the Chilean Atacama Desert, will enable researchers to work out what happened in the system in more detail, and perhaps reveal even more surprises.

Links

• Research paper (preprint; for the final version of the embargoed paper, please check https://www.eurekalert.org/press/scipak/ or contact scipak@aaas.org while the embargo lasts)
• Photos of the VLT/VLTI
• Find out more about ESO’s Extremely Large Telescope on our dedicated website and press kit
• For journalists: subscribe to receive our releases under embargo in your language
• For scientists: got a story? Pitch your research

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An Infinity of Worlds:
Cosmic Inflation and the Beginning of the Universe

A new report from the European Southern Observatory (ESO):

Groundbreaking survey reveals secrets of planet birth
around dozens of stars

In a series of studies, a team of astronomers has shed new light on the fascinating and complex process of planet formation. The stunning images, captured using the European Southern Observatory’s Very Large Telescope (ESO’s VLT) in Chile, represent one of the largest ever surveys of planet-forming discs. The research brings together observations of more than 80 young stars that might have planets forming around them, providing astronomers with a wealth of data and unique insights into how planets arise in different regions of our galaxy.

“This is really a shift in our field of study,”

says Christian Ginski, a lecturer at the University of Galway, Ireland, and lead author of one of three new papers published today in Astronomy & Astrophysics.

“We’ve gone from the intense study of individual star systems to this huge overview of entire star-forming regions.”

To date more than 5000 planets have been discovered orbiting stars other than the Sun, often within systems markedly different from our own Solar System. To understand where and how this diversity arises, astronomers must observe the dust- and gas-rich discs that envelop young stars — the very cradles of planet formation. These are best found in huge gas clouds where the stars themselves are forming.

Much like mature planetary systems, the new images showcase the extraordinary diversity of planet-forming discs.

“Some of these discs show huge spiral arms, presumably driven by the intricate ballet of orbiting planets,”

says Ginski.

“Others show rings and large cavities carved out by forming planets, while yet others seem smooth and almost dormant among all this bustle of activity,”

adds Antonio Garufi, an astronomer at the Arcetri Astrophysical Observatory, Italian National Institute for Astrophysics (INAF), and lead author of one of the papers.

The team studied a total of 86 stars across three different star-forming regions of our galaxy: Taurus and Chamaeleon I, both around 600 light-years from Earth, and Orion, a gas-rich cloud about 1600 light-years from us that is known to be the birthplace of several stars more massive than the Sun. The observations were gathered by a large international team, comprising scientists from more than 10 countries.

The team was able to glean several key insights from the dataset. For example, in Orion they found that stars in groups of two or more were less likely to have large planet-forming discs. This is a significant result given that, unlike our Sun, most stars in our galaxy have companions. As well as this, the uneven appearance of the discs in this region suggests the possibility of massive planets embedded within them, which could be causing the discs to warp and become misaligned.

While planet-forming discs can extend for distances hundreds of times greater than the distance between Earth and the Sun, their location several hundreds of light-years from us makes them appear as tiny pinpricks in the night sky. To observe the discs, the team employed the sophisticated Spectro-Polarimetric High-contrast Exoplanet REsearch instrument (SPHERE) mounted on ESO’s VLT. SPHERE’s state-of-the-art extreme adaptive optics system corrects for the turbulent effects of Earth’s atmosphere, yielding crisp images of the discs. This meant the team were able to image discs around stars with masses as low as half the mass of the Sun, which are typically too faint for most other instruments available today. Additional data for the survey were obtained using the VLT’s X-shooter instrument, which allowed astronomers to determine how young and how massive the stars are. The Atacama Large Millimeter/submillimeter Array (ALMA), in which ESO is a partner, on the other hand, helped the team understand more about the amount of dust surrounding some of the stars.

As technology advances, the team hopes to delve even deeper into the heart of planet-forming systems. The large 39-metre mirror of ESO’s forthcoming Extremely Large Telescope (ELT), for example, will enable the team to study the innermost regions around young stars, where rocky planets like our own might be forming.

For now, these spectacular images provide researchers with a treasure trove of data to help unpick the mysteries of planet formation.

“It is almost poetic that the processes that mark the start of the journey towards forming planets and ultimately life in our own Solar System should be so beautiful,”

concludes Per-Gunnar Valegård, a doctoral student at the University of Amsterdam, the Netherlands, who led the Orion study. Valegård, who is also a part-time teacher at the International School Hilversum in the Netherlands, hopes the images will inspire his pupils to become scientists in the future.

Links

• Research paper
• Photos of the VLT
• Find out more about ESO’s Extremely Large Telescope on our dedicated website and press kit
• For journalists: subscribe to receive our releases under embargo in your language
• For scientists: got a story? Pitch your research

=== Amazon Ads ===

Celestron – NexStar 130SLT Computerized Telescope –
Compact and Portable –
Newtonian Reflector Optical Design –
SkyAlign Technology –
Computerized Hand Control –
130mm Aperture

====

An Infinity of Worlds:
Cosmic Inflation and the Beginning of the Universe