Key Takeaways
- Massive Discovery: Astronomers identified Gaia BH3, a dormant black hole nearly 33 times the Sun’s mass, 1,926 light-years from Earth, the most massive stellar black hole known in the Milky Way.
- Unexpected Find: Gaia BH3’s discovery was serendipitous, revealing itself through the wobble of a companion star in the Aquila constellation, detected via ESA’s Gaia telescope.
- New Research Insights: This is the third dormant black hole identified by Gaia, offering new data on high-mass black holes and their potential formation from metal-poor stars.
- Companion Composition Clues: Gaia BH3’s companion star is metal-poor, linking it to stars likely formed within the first 2 billion years post-Big Bang, enriching theories on high-mass stellar black holes’ origins.
- Next Steps for Gaia’s Data: The ongoing Gaia mission’s data will be vital in expanding astronomical knowledge, with future releases expected to reveal more about the Milky Way’s structure and contents.
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Astronomers recently made a groundbreaking discovery: a dormant black hole named Gaia BH3, residing about 1,926 light-years away in the Milky Way’s Aquila constellation. Known as a “sleeping giant,” Gaia BH3 is approximately 33 times the Sun’s mass, making it the largest stellar black hole known in our galaxy. This black hole is only the second nearest to Earth, with Gaia BH1 slightly closer at around 1,500 light-years away.
The find was unintentional. Researchers were sifting through data from the European Space Agency’s Gaia space telescope, anticipating an upcoming data release when they noticed an unusual wobbling motion in a nearby star. This disturbance revealed the presence of Gaia BH3, whose immense gravitational force was causing a nearby giant star to orbit around it. This wobble marked the third dormant black hole identified by Gaia, a significant milestone in astronomical research.
Unlike active black holes that feed on surrounding material and emit detectable X-rays, dormant black holes like Gaia BH3 lack a close companion to consume. Their presence is usually detected only when they exert gravitational effects on neighboring stars. Gaia BH3’s detection was made possible by Gaia’s data, which highlighted its unique influence on the companion star’s movement, sparking a deeper investigation.
Insights Into Black Hole Formation
To confirm the mass and characteristics of Gaia BH3, scientists utilized the European Southern Observatory’s Very Large Telescope (VLT) in Chile, along with other observatories. This research revealed that Gaia BH3 stands out as one of the most massive stellar black holes known. Typically, stellar black holes in the Milky Way are about ten times the Sun’s mass, with Cygnus X-1 previously holding the record at 21 times the Sun’s mass. Gaia BH3’s sheer size opens doors for new studies on stellar black holes and their unique characteristics.
A significant aspect of Gaia BH3’s formation is its metal-poor nature. Stellar black holes are thought to form from massive stars’ deaths. Gaia BH3’s mass suggests that it originated from the collapse of a metal-poor star. These ancient stars, composed mainly of hydrogen and helium, lose less mass during their lifetimes, retaining more material for high-mass black holes. While astronomers suspected this relationship between metal-poor stars and massive black holes, direct evidence was limited until Gaia BH3’s discovery. The chemical makeup of its companion star supports this theory, indicating both stars likely share an ancient, metal-poor origin.
The companion star’s trajectory also suggests a fascinating history. Its orbit within the Milky Way moves counter to the general motion of stars in the galactic disk, indicating it may have once belonged to a smaller galaxy that merged with the Milky Way over 8 billion years ago. This discovery not only hints at Gaia BH3’s ancient origins but also provides clues about the Milky Way’s own formation.
With future Gaia data releases, astronomers hope to uncover more about Gaia BH3 and similar massive stellar black holes. Gaia’s mission, originally intended to map stars, is evolving beyond its initial goals, significantly advancing our understanding of black holes and the broader structure of our galaxy. The next Gaia data release is anticipated in 2025, likely bringing new revelations in our cosmic neighborhood.
Beyond being close, everyone in astro I know is extremely excited this morning because of the mass of this black hole- 33 solar masses is tough to form from just a normal star collapsing, but the paper shows the black hole’s companion star is a low metallicity one that likely formed in the galactic halo that migrated in, so one of the rare stars capable of leaving behind a big black hole like this. likely too big to form just from a star collapsing at the end of its life, and would possibly have had to be created by two black holes merging. (A merger of two smaller black holes is also possible. Cool!) Just like what LIGO and the gravitational wave folks are looking for! And implies that there are a ton of these black holes out there if there’s one so close to us!
Finding them, however, is tough. Gaia is a satellite surveying a billion stars or so to find slight wobbles in their motion over time, which tells us their distance and also (in this case) if there’s a mystery companion. They periodically release the data every few years, and this one is from the team as part of pre-release data analysis, which found a star wobbling in its orbit in such a way that it can only work if it is orbiting a black hole at 16 times the Earth-sun distance. What’s more, there’s hints from the star’s composition that it would have formed separately from the black hole and then captured by it later after they both formed- also exciting if you’re interested in how these systems form!
to answer two common questions:
We know dark matter is not a bunch of black holes (or a bunch of Jupiters) because people have in fact looked for them as a possible answer! There was a huge push back in the day to look for MAssive Compact Halo Objects (MACHOs), as they were called, by looking for gravitational microlensing between us and the Magellanic clouds (satellite galaxies of the Milky Way). And… they did find some! But nowhere NEAR enough to explain the effects of dark matter.
There is no danger from this black hole being there, any more than a star system with ~30x the mass of the sun would have a gravitational influence on us at this enormous distance. It’s worth noting that black holes don’t actually suck in material around them and that’s a common misconception- If the sun for example shrunk right now into a black hole, it would shrink to 3km wide, but our orbit and those of everything else wouldn’t change a bit, and we’d just keep going around as we always had.
To help comprehend the distance, Voyager 1 will be 1 light day away from Earth in November 2026.
2,000 light years is still an astounding distance and we don’t even have the ability to fully comprehend just how much of an expanse that is
Even if I become light, I need to travel for 2 fucking thousand years? No. Give me a worm hole to the black hole.
My question is: is this close enough and big enough for us to point the EHT at it and get a decent image?
Isn’t that a small black hole? I’m not good at scale.
Is this the closest known black hole?
I understand that this is significant due to medium size black holes being quite rare. Something to do with not fully understanding the process that leads to small black holes becoming supermassive