Astronomy

Astronomers have found the largest stellar mass black hole in the Milky Way so far. At 33 solar masses, it dwarfs the previous record-holder, Cygnus X-1, which has only 21 solar masses. Most stellar mass black holes have about 10 solar masses, making the new one—Gaia BH3—a true giant.

Supermassive black holes (SMBH) like Sagittarius A Star at the heart of the Milky Way capture most of our black hole attention. Those behemoths can have billions of solar masses and have enormous influence on their host galaxies.

But stellar-mass holes are different. Unlike SMBHs that grow massive through mergers with other black holes, stellar black holes result from massive stars exploding as supernovae. SMBHs are always found in the center of a massive galaxy, but stellar black holes can be hidden anywhere.

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

Pasquale Panuzzo, National Centre for Scientific Research (CNRS) at the Observatoire de Paris

Astronomers found BH3 in data from the ESA’s Gaia spacecraft. It’s Gaia’s third stellar black hole. BH3 has a stellar companion, and the black hole’s 33 combined solar masses tugged on its aged, metal-poor companion. The star’s tell-tale wobbling betrayed BH3’s presence. At only 2,000 light-years away, BH3 is awfully close in cosmic terms.

Astronomers have found the most massive stellar black hole in our galaxy, thanks to the wobbling motion it induces on a companion star. This artist’s impression shows the star’s orbits and the black hole, dubbed Gaia BH3, around their common centre of mass. The European Space Agency’s Gaia mission measured this wobbling over several years. Image Credit: ESO/L. Calçada

A new research letter in Astronomy and Astrophysics presented the discovery. Its title is “Discovery of a dormant 33 solar-mass black hole in pre-release Gaia astrometry.” The lead author is Pasquale Panuzzo, an astronomer from the National Centre for Scientific Research (CNRS) at the Observatoire de Paris.

“No one was expecting to find a high-mass black hole lurking nearby, undetected so far,” said Panuzzo. “This is the kind of discovery you make once in your research life.”

This black hole is remarkable for its considerable mass. Researchers have found stellar black holes with similar masses, but always in other galaxies. The size is confounding, but astrophysicists have pieced together how they may become so massive.

They could result from the collapse of metal-poor stars. These stars are composed almost entirely of hydrogen and helium, the primordial elements. Scientists think these stars lose less mass over their lifetimes of fusion than other stars. They retain more mass, so they collapse into more massive black holes. This idea is based on theory; there’s no direct evidence.

But BH3 could change that.

Binary stars tend to form together and have the same metallicity. Follow-up observations showed that BH3’s companion star is likely a remnant of a globular cluster that the Milky Way absorbed more than eight billion years ago. Since binary stars tend to have the same metallicity, this metal-poor companion bolsters the idea that low-metallicity stars can retain more mass and form larger stellar black holes. This is the first evidence supporting the idea that ancient and metal-poor massive stars collapse into massive black holes. It also supports the idea that these early stars may have evolved differently than modern stars of similar masses.

But there’s another interpretation.

Artist’s impression of a Type II supernova explosion, which involves the destruction of a massive supergiant star. When stars explode as supernovae, they eject matter into space, potentially polluting nearby companion stars. Image Credit: ESO

When stars explode as supernovae, they forge heavier elements that are blown out into space. Shouldn’t the companion show evidence of contamination by the metals from BH3’s supernova?

“What strikes me is that the chemical composition of the companion is similar to what we find in old metal-poor stars in the galaxy,” explains Elisabetta Caffau of CNRS, Observatoire de Paris, also a member of the Gaia collaboration. “There is no evidence that this star was contaminated by the material flung out by the supernova explosion of the massive star that became BH3.” From this perspective, the pair may not have formed together. Instead, the black hole could’ve acquired its companion only after its birth, capturing it from another system.

BH3 and the two other black holes found by Gaia are dormant. That means there’s nothing close enough for them to “feed” on. Even though BH3 has a companion, it’s about 16 AU away. If BH3 was actively accreting matter, it would release energy that would betray its presence. Its dormancy enabled it to remain undetected.

Simulation of glowing gas around a spinning black hole. As the gas heats up, it emits energy that makes it visible. If the black hole has no nearby companion, it’s dormant and harder to find. Image Credit: Chris White, Princeton University

At only 2,000 light years away, astronomers are bound to keep studying BH3.

“Finally, the bright magnitude of the system and its relatively small distance makes it an easy target for further observations and detailed analyses by the astronomical community,” the discoverers write in their research letter.

This discovery may have been serendipitous, but it was no accident. A dedicated team of researchers scours Gaia data for stars with odd companions. This includes light and heavy exoplanets, other stars, and black holes. Gaia can’t spot planets or dormant black holes but can spot their effect on their stellar companions.

The researchers behind the discovery released their findings before Gaia’s next official data release. They felt it was too important to sit on. “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,” said co-author Elisabetta Caffau, also a Gaia collaboration member and CNRS scientist from the Observatoire de Paris – PSL.

“We have been working extremely hard to improve the way we process specific datasets compared to the previous data release (DR3), so we expect to uncover many more black holes in DR4,” said Berry Holl of the University of Geneva, in Switzerland, member of the Gaia collaboration.

“This discovery should also be seen as a preliminary teaser for the content of Gaia DR4, which will undoubtedly reveal other binary systems hosting a BH,” the authors conclude.

Gaia DR4 is scheduled to be released no sooner than the end of 2023. If past data releases are any indication, the data will be full of new discoveries. If there are enough binary stellar mass black holes in the data, astronomers may get closer to understanding where they come from and if massive stars behaved differently in the early Universe.

The post The Milky Way’s Most Massive Stellar Black Hole is Only 2,000 Light Years Away appeared first on Universe Today.

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The last total solar eclipse across the Mexico, the U.S. and Canada for a generation wows observers.

Did you see it? Last week’s total solar eclipse did not disappoint, as viewers from the Pacific coast of Mexico, across the U.S. from Texas to Maine and through the Canadian Maritime provinces were treated to an unforgettable show. The weather threw us all a curve-ball one week out, as favored sites in Texas and Mexico fought to see the event through broken clouds, while areas along the northeastern track from New Hampshire and Maine onward were actually treated to clear skies.

Many eclipse chasers scrambled to reposition themselves at the last minute as totality approached. In northern Maine, it was amusing to see tiny Houlton, Maine become the epicenter of all things eclipse-based.

A composite of images snapped every five seconds during totality, showing off solar prominences. Credit: György Soponyai observing from Montreal, Canada. Tales of a Total Solar Eclipse

We were also treated to some amazing images of the eclipse from Earth and space. NASA also had several efforts underway to chase the eclipse. Even now, we’re still processing the experience. It takes time (and patience!) for astro-photos to make their way through the workflow. Here are some of the best images we’ve seen from the path of totality:

Tony Dunn had an amazing experience, watching the eclipse from Mazatlan, Mexico. “When totality hit, it didn’t look real,” Dunn told Universe Today. “It looked staged, like a movie studio. the lighting is something that can’t be experienced outside a total solar eclipse.”

Totality on April 8th, with prominences. Credit: Tony Dunn.

Dunn also caught an amazing sight, as the shadow of the Moon moved across the low cloud cover:

#Eclipse2024 #Mazatlan The shadow of the Moon crosses the sky. pic.twitter.com/9FEf4TTK8r

— Tony Dunn (@tony873004) April 14, 2024

Black Hole Sun

Peter Forister caught the eclipse from central Indiana. “It was my second totality (after 2017 in South Carolina), so I knew what was coming,” Forister told Universe Today. “But it was still as incredible and beautiful as anything I’ve ever seen in nature. The Sun and Moon seemed huge in my view—a massive black hole (like someone took a hole punch to the sky) surrounded by white and blue flames streaking out. Plus, there was great visibility of the planets and a few stars. The memory has been playing over and over in my head since it happened—and it’s combined with feelings of awe and wonder at how beautiful our Universe and planet really are. The best kind of memory!”

Totality over Texas. Credit: Eliot Herman

Like many observers, Eliot Herman battled to see the eclipse through clouds. “As you know, we had really frustrating clouds,” Herman told Universe Today. “I shot a few photos (in) which you can see the eclipse embedded in the clouds and then uncovered to show the best part. For me it almost seemed like a cosmic mocking, showing me what a great eclipse it was, and lifting the veil only at the end of the eclipse to show me what I missed…”

Totality and solar prominences seen through clouds. Credit: Eliot Herman Totality Crosses Into Canada

Astrophotographer Andrew Symes also had a memorable view from Cornwall, Ontario. “While I’ve seen many beautiful photos and videos from many sources, they don’t match what those us there in person saw with our eyes,” Symes told Universe Today. “The sky around the Sun was not black but a deep, steely blue. The horizon was lighter–similar to what you’d see during a sunset or sunrise–but still very alien.”

“The eclipsed Sun looked, to me, like an incredibly advanced computer animation from the future! The Sun and corona were very crisp, and the Sun looked much larger in the sky than I’d expected. The eclipsed Sun had almost a three-dimensional quality… almost as if it were a dark, round button-like disk surrounded by a bright halo affixed to a deep blue/grey background. It was as if a ‘worm hole’ or black hole had somehow appeared in front of us. I’m sure my jaw dropped as it was truly a moment of utter amazement. I’m smiling as I type it now… and still awestruck as I recall it in my mind!”

An amazing eclipse. Credit: Andrew Symes. Success for the Total Solar Eclipse in Aroostook County Maine

We were met with success (and clear skies) watching the total solar eclipse with family from our hometown of Mapleton, Maine. We were mostly just visually watching this one, though we did manage to nab a brief video of the experience.

What I was unprepared for was the switch from partial phases to totality. It was abrupt as expected, but there almost seemed to be brief but perceptible pause from day to twilight, as the corona seemed to ‘switch on.’ We all agreed later on that the steely blue sky was not quite night… but not quite twilight, either.

The elusive diamond ring, seen from Wappappello Lake, Missouri on April 8th. Credit: Chris Becke

When’s the next one? I often wonder how many watchers during a given eclipse were ‘bitten by the bug,’ and looking to chase the next one. Spain is set to see an eclipse a year for the next three years, starting in 2026:

Spain is set to become ‘solar eclipse central’ in the coming years, with the next total solar eclipse crossing N. Spain on August 12, 2026, another total solar eclipse on August 2, 2027 crossing the Strait of Gibraltar, and a sunset annular solar eclipse on January 26, 2028. pic.twitter.com/acO4urNG45

— Dave Dickinson (@Astroguyz) April 12, 2024

Spain in August… be sure to stay cool and bring sunblock. Don’t miss the next total solar eclipse, and be thankful for our privileged vantage point in time and space.

The post Amazing Amateur Images of April 8th’s Total Solar Eclipse appeared first on Universe Today.

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