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Black Hole Police Discover First Dormant Black Hole Outside the Milky Way

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Artist's impression of the binary system VFTS 243. Located in the Tarantula Nebula in the Large Magellanic Cloud, the system consists of a hot blue star with a mass of 25 times that of the Sun and a black hole with a mass of at least nine times that of the Sun
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A dormant black hole at least nine times the mass of the Sun has been discovered just 160,000 light-years from Earth, orbiting a star.

A group of researchers, known as the “black hole police” because they debunked so many black hole discoveries, searched nearly 1,000 stars in the Tarantula Nebula in the constellation Dorado before finding it.

They claim it is the first dormant stellar-mass black hole discovered outside the Milky Way galaxy.

Stellar-mass black holes form when massive stars reach the end of their lives and collapse under their own gravity.

A black hole is said to be “sleeping” if it is not actively absorbing matter and, as a result, does not emit any light or other radiation.

The discovery has been compared to looking for a “needle in a haystack” as dormant black holes are notoriously difficult to detect because they don’t interact with their environment.

Co-author Dr. Pablo Marchand of KU Leuven in Belgium said: “It’s incredible, we hardly know of any sleeping black holes, given how ordinary astronomers think they are.”

Artist’s impression of the binary system VFTS 243. Located in the Tarantula Nebula in the Large Magellanic Cloud, the system consists of a hot blue star with a mass of 25 times that of the Sun and a black hole with a mass of at least nine times that of the Sun

Artist's impression of the binary VFTS 243. The background image shows an image taken by the Visible and Infrared Survey Telescope for Astronomy (VISTA) of a segment of the Large Magellanic Cloud marking the region in which VFTS 243 resides. Sizes of the star, black hole, and orbits are not to scale

Artist’s impression of the binary VFTS 243. The background image shows an image taken by the Visible and Infrared Survey Telescope for Astronomy (VISTA) of a segment of the Large Magellanic Cloud marking the region in which VFTS 243 resides. Sizes of the star, black hole, and orbits are not to scale

WHAT IS A BINARY SYSTEM?

A binary star is a system of two stars that are bound by gravity and revolve around each other.

One or both of the stars in the system could be a black hole.

In this case, they are often identified by their bright X-ray emission.

X-rays are produced when matter falls from one component, called a donor (usually a relatively normal star), to another component, called an accretor (black hole).

The matter forms a luminous accretion disk rotating around the black hole.

However, observations from NASA’s Chandra X-ray Telescope show that VFTS 243 is weak in X-rays.

The newly discovered black hole is located in the Large Magellanic Cloud, a satellite galaxy neighboring the Milky Way.

The Large Magellanic Cloud orbits a hot blue star that is almost three times the size of our galaxy.

It is believed that there are thousands of stellar-mass black holes in the Milky Way and the Magellanic Clouds.

They are much smaller than the supermassive black hole 27,000 light-years from Earth that powers the Milky Way, known as Sagittarius A*.

The black hole is part of a “binary system” with a luminous companion star, where they orbit each other in a system known as VFTS 243.

Co-author Dr Julia Bodensteiner from the European Southern Observatory (ESO) in Germany said: “For more than two years we have been looking for such black hole binaries.

“I was very excited when I heard about VFTS 243, which I believe is the most compelling candidate reported to date.”

It took six years of data from ESO’s Very Large Telescope (VLT) to officially identify VFTS 243.

The FLAMES (Large Fiber Array Multi-Element Spectrograph) scanner on the VLT can simultaneously observe more than a hundred objects.

Historically, binaries containing stellar-mass black holes have been identified by the presence of bright X-rays from the accretion disk.

The glowing accretion disk is made up of gases from the living star’s atmosphere that flow towards and around the black hole.

However, observations from NASA’s Chandra X-ray Telescope show that VFTS 243 is weak in X-rays.

This image, taken by the VLT Survey Telescope at ESO's Paranal Observatory in Chile, shows the Tarantula Nebula and its surroundings in the Large Magellanic Cloud.  It shows star clusters, glowing gas clouds, and the scattered remnants of supernova explosions.

This image, taken by the VLT Survey Telescope at ESO’s Paranal Observatory in Chile, shows the Tarantula Nebula and its surroundings in the Large Magellanic Cloud. It shows star clusters, glowing gas clouds, and the scattered remnants of supernova explosions.

Historically, binaries containing stellar-mass black holes have been identified by the presence of bright X-rays from the accretion disk (pictured).  A luminous accretion disk is made up of gases from the atmosphere of a living star that flow towards and surround the black hole (illustrated in illustration)

Historically, binaries containing stellar-mass black holes have been identified by the presence of bright X-rays from the accretion disk (pictured). A luminous accretion disk is made up of gases from the atmosphere of a living star that flow towards and surround the black hole (illustrated in illustration)

The study, published today in the journal Nature Astronomy, also sheds light on how black holes are created from the cores of dying stars.

The star that gave birth to VFTS 243 seems to have completely collapsed, leaving no trace of a powerful supernova explosion.

Dr. Shenar explained: “Evidence for this ‘outright collapse’ scenario is recent, but our study may provide one of the most direct indications.

“This has huge implications for the origin of black hole mergers in space.”

It took six years of data from ESO's Very Large Telescope (pictured) to identify VFTS 243.

It took six years of data from ESO’s Very Large Telescope (pictured) to identify VFTS 243.

The FLAMES instrument mounted on the Nasmyth A platform of ESO's Very Large Telescope.  FLAMES is a high resolution VLT spectrograph that can access targets in a large corrected field of view.  It allows you to observe more than a hundred objects at the same time.

The FLAMES instrument mounted on the Nasmyth A platform of ESO’s Very Large Telescope. FLAMES is a high resolution VLT spectrograph that can access targets in a large corrected field of view. It allows you to observe more than a hundred objects at the same time.

Artistic rendering of NASA's Chandra X-ray Observatory Space Telescope

Artistic rendering of NASA’s Chandra X-ray Observatory Space Telescope

Despite the nickname “black hole police”, the international team of researchers actively encourages careful study of their work.

Lead author Dr. Tomer Schenar of the University of Amsterdam said: “As a researcher who has debunked potential black holes in recent years, I was extremely skeptical about this discovery.

“This is the first time our team has come together to report the discovery of a black hole, not dismiss it.”

Dr. Karim El-Badri of Harvard University in Boston has been dubbed the “black hole buster” because of his notoriety for debunking discoveries.

Dr El-Badri said: “When Tomer asked me to double-check his findings, I had my doubts.

“But I couldn’t find a plausible explanation for the non-black hole data.

“Of course, I expect others in the field to take a close look at our analysis and try to come up with alternative models.

“This is a very exciting project to be involved in.”

WHAT IS INSIDE A BLACK HOLE?

Black holes are strange objects in the universe that get their name from the fact that nothing can escape their gravity, not even light.

If you venture too close and cross the so-called event horizon, a point from which no light can escape, you will also be trapped or destroyed.

In the case of small black holes, you will never survive such close encounters anyway.

Tidal forces near the event horizon are enough to stretch any matter until it is just a string of atoms, in a process physicists call “spaghettification.”

But for large black holes, such as the supermassive objects at the core of galaxies like the Milky Way, which weigh tens of millions, if not billions of times the mass of a star, crossing the event horizon will be uneventful.

Since the transition from our world to the world of black holes should be possible, physicists and mathematicians have long wondered what this world would look like.

They turned to the equations of Einstein’s general theory of relativity to predict the world inside a black hole.

These equations work well until the observer reaches a center or singularity, where, in theoretical calculations, the curvature of spacetime becomes infinite.

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