Tag Archives: black hole

Star becomes black hole without supernova explosion

The uncertainty of science: Astronomers think they have identified a star that, rather than die and become a black hole in a supernova explosion, merely fizzled into a black hole.

Starting in 2009, one particular star in the Fireworks Galaxy, named N6946-BH1, began to brighten weakly. By 2015, it appeared to have winked out of existence. The astronomers aimed the Hubble Space Telescope at the star’s location to see if it was still there but merely dimmed. They also used the Spitzer Space Telescope to search for any infrared radiation emanating from the spot. That would have been a sign that the star was still present, but perhaps just hidden behind a dust cloud.

All the tests came up negative. The star was no longer there. By a careful process of elimination, the researchers eventually concluded that the star must have become a black hole.

There are a lot of uncertainties here. Nonetheless, astronomers have theorized that some stars could collapse into black holes with any explosions, and it appears they might have found their first example of that.

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Did a giant black hole eat a star?

New data now suggests that what astronomers had thought was the brightest supernova ever detect might have instead been the ripping apart of a star as it passed too close to a supermassive black hole.

In this scenario, the extreme gravitational forces of a supermassive black hole, located in the centre of the host galaxy, ripped apart a Sun-like star that wandered too close — a so-called tidal disruption event, something so far only observed about 10 times. In the process, the star was “spaghettified” and shocks in the colliding debris as well as heat generated in accretion led to a burst of light. This gave the event the appearance of a very bright supernova explosion, even though the star would not have become a supernova on its own as it did not have enough mass. The team based their new conclusions on observations from a selection of telescopes, both on the ground and in space. Among them was the NASA/ESA Hubble Space Telescope, the Very Large Telescope at ESO’s Paranal Observatory and the New Technology Telescope at ESO’s La Silla Observatory

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It turns out that the object dubbed G2 that is zipping past the Milky Way’s central black hole is behaving not like a cloud but more like a star.

The uncertainty of science: It turns out that the object dubbed G2 that is zipping past the Milky Way’s central black hole is behaving not like a cloud but more like a star.

The latest observations by the Keck Observatory in Hawaii show that the gas cloud called “G2” was surprisingly still intact, even during its closest approach to the supermassive black hole at the center of our Milky Way galaxy. Astronomers from the UCLA Galactic Center Group reported today that observations obtained on March 19 and 20, 2014 show the object’s density was still “robust” enough to be detected. This means G2 is not just a gas cloud, but likely has a star inside.

When I wrote a piece about this object for Sky & Telescope I found that among astronomers there was great skepticism about it being just a gas cloud that would be ripped apart when it flew past the black hole. The early data was not conclusive, but enough of it suggested G2 was a star, not a cloud. It turns out here that the skeptics were right.

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The biggest black hole yet found, 17 billion times the mass of our sun.

The biggest black hole yet found, 17 billion times the mass of our sun.

The unusual black hole makes up 14 percent of its galaxy’s mass, rather than the usual 0.1 percent. … NGC 1277 [the galaxy] lies 220 million light-years away in the constellation Perseus. The galaxy is only ten percent the size and mass of our own Milky Way. Despite NGC 1277’s diminutive size, the black hole at its heart is more than 11 times as wide as Neptune’s orbit around the Sun.

Based on these measurements, it appears that this black hole is literally eating this galaxy whole.

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The supermassive black hole in the center of the Milky Way is about to get a snack.

The supermassive black hole in the center of the Milky Way is about to get a snack.

Update: The recently launched NuStar telescope in July detected its first flare from the central black hole (which by the way is called Sagittarius A* and is pronounced Sagittarius A-star). If the gas cloud produces any fireworks as it whips past the black hole in the coming year then NuStar should see it.

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Astronomers have discovered a star that circles the supermassive black hole at the center of the Milky Way in only 11.5 years.

Dizzy: Astronomers have discovered a star that circles the supermassive black hole at the center of the Milky Way in only 11.5 years.

This newly discovered star joins another that is 15 times brighter and has a 16 year orbit. The combined orbital data from both will allow astronomers to measure precisely the size of the black hole while also measuring the distortion of space caused by its intense gravitational field.

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