Tag Archives: Globular

Astronomers find intermediate-mass black hole in largest globular cluster in Milky Way

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Using more than 500 images from the NASA/ESA Hubble Space Telescope, astronomers have found evidence of a 20,000-solar-mass black hole at the center of Earth. Omega CentauriIt is a globular cluster located in the constellation Centaurus, 5,430 parsecs (17,710 light years) from the Sun.

Omega Centauri is about 10 times more massive than other large globular clusters. Image credit: NASA / ESA / Hubble / Maximilian Häberle, MPIA.

Astronomers know that stellar-mass black holes (black holes with masses between 10 and 100 times that of the Sun) are the remnants of dying stars, and that supermassive black holes, with masses more than a million times that of the Sun, exist at the center of most galaxies.

But the universe is littered with what appear to be more mysterious types of black holes.

These intermediate-mass black holes, with masses between 100 and 10,000 times that of the Sun, are so difficult to measure that their very existence is sometimes debated.

Only a few intermediate-mass black hole candidates have been discovered so far.

Determining the black hole population is an important step towards understanding the formation of supermassive black holes in the early universe.

“Omega Centauri is a special example among globular clusters in the Milky Way,” said astronomer Maximilian Höberle of the Max Planck Institute for Astronomy and his colleagues.

“Omega Centauri is widely accepted to be the stripped core of an accreted dwarf galaxy due to its high mass, complex stellar population and kinematics.”

“These factors, combined with its proximity, make the planet a prime target in the search for intermediate-mass black holes.”

Omega Centauri is made up of about 10 million stars, making it about 10 times more massive than any other large globular cluster.

In the study, the authors measured the velocities of 1.4 million stars from images of the cluster taken by the Hubble Space Telescope.

Although most of these observations were intended for calibration of Hubble's instruments rather than for scientific use, they proved to be an ideal database for the team's research activities.

“We looked for fast-moving stars that are expected to be near concentrated masses such as black holes,” said astronomer Holger Baumgart of the University of Queensland.

“Identifying these stars was the smoking gun we needed to prove the existence of black holes, and we've done just that.”

“We found seven stars that shouldn't be there,” Dr Hebel said.

“They're moving so fast that they're likely to escape the herd and never come back.”

“The most likely explanation is that a very massive object is gravitationally tugging on these stars, keeping them near the center.”

“The only objects this massive are black holes, which have a mass at least 8,200 times that of the Sun.”

“This discovery is the most direct evidence to date for the presence of an intermediate-mass black hole at Omega Centauri,” said Dr Nadine Neumayer, an astronomer at the Max Planck Institute for Astronomy.

“This is extremely exciting because very few other black holes with similar masses are known.”

“The black hole at Omega Centauri may be the best example of an intermediate-mass black hole in our cosmic neighborhood.”

Team paper Published in the journal Nature.

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M. Heberle others2024. Stars moving at high speed around the intermediate-mass black hole at Omega Centauri. Nature 631, 285-288; Source: 10.1038/s41586-024-07511-z

Source: www.sci.news

Hubble Observes Large Globular Cluster in Large Magellanic Cloud

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Astronomers using the NASA/ESA Hubble Space Telescope have captured detailed images of the globular star cluster NGC 1651 in the constellation Mensa.

This Hubble image shows the globular cluster NGC 1651 about 162,000 light-years away in the constellation Mensa. Image credits: NASA / ESA / Hubble / L. Girardi / F. Niederhofer.

Globular clusters are densely packed spherical clusters of hundreds of thousands or even millions of stars.

They are among the oldest known objects in the universe and are preferentially associated with the oldest components of galaxies.

There are at least 150 such objects in our Milky Way, and several more may be hidden behind the galaxy's thick disk.

NGC1651 is part of the Large Magellanic Cloud, the largest and brightest of the Milky Way's satellite galaxies.

beginning discovered Discovered by British astronomer John Herschel on November 3, 1834, this globular cluster is located approximately 162,000 light-years away in the constellation Mensa.

NGC 1651, also known as ESO 55-30 or LW 12, has a diameter of 120 light years.

“A remarkable feature of this image is that NGC 1651 nearly fills the entire image, even though the globular cluster is only about 10 to 300 light-years in diameter,” Hubble astronomers said. Masu.

“In contrast, there are many Hubble images that feature entire galaxies, tens or even hundreds of millions of light-years in diameter, that more or less fill the entire image.”

Color images of NGC 1651 consist of observations from. Hubble's Wide Field Camera 3 Found in the near-infrared and optical portions of the spectrum.

“A common misconception is that Hubble and other large telescopes can observe objects of vastly different sizes by zooming in, much like we would with special cameras on Earth,” the astronomers said. Ta.

“However, while smaller telescopes may have the option to zoom in and out to some extent, larger telescopes do not.”

“Each telescope instrument has a fixed 'field of view' (the size of the area of the sky that can be observed in a single observation).”

“For example, WFC3's ultraviolet/visible light channel, the channel and instrument used to collect the data used in this image, has a field of view that is approximately one-twelfth the diameter of the moon as seen from Earth. Masu.”

“Every time WFC3 makes an observation, it becomes the size of the region of sky it can observe.”

“There are two reasons why Hubble is able to observe objects with such widely different sizes,” the researchers said.

“First, the distance to an object determines how big that object appears from Earth, so an entire galaxy that is relatively far away is compared to a relatively nearby globular cluster like NGC 1651. could take up the same amount of space as the sky.''

“In fact, a distant spiral galaxy lurks just to the left of the cluster in this image. It's undoubtedly much larger than the cluster, but here it appears small enough to blend in with the foreground stars.”

“Second, multiple images across different parts of the sky can be mosaicked to create a single image of an object too large for Hubble's field of view.”

Source: www.sci.news

Hubble Observes NGC 1841 Globular Cluster

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This new image from the NASA/ESA Hubble Space Telescope shows the globular star cluster NGC 1841 in the Large Magellanic Cloud.

This Hubble image shows the globular cluster NGC 1841 about 162,000 light-years away in the constellation Mensa. The color images include ultraviolet, optical, and near-infrared observations from both Hubble's Wide Field Camera 3 (WFC3) and Survey Altitude Camera (ACS). Three filters were used to sample different wavelengths. Color is obtained by assigning different hues to each monochromatic image associated with an individual filter. Image credits: NASA / ESA / Hubble / A. Saragedini / F. Niederhofer.

NGC1841 It is located approximately 162,000 light years away in the constellation Mensa.

The cluster is discovered It was proposed by British astronomer John Herschel on January 19, 1836.

Also known as ESO 4-15, this galaxy is part of the Large Magellanic Cloud, a satellite galaxy of our Milky Way.

“Satellite galaxies are galaxies that are gravitationally bound in orbit around a larger host galaxy,” Hubble astronomers said in a statement.

“While we usually think of our galaxy's closest galactic companion as the Andromeda galaxy, it would be more accurate to say that the Andromeda galaxy is the closest galaxy that does not orbit the Milky Way.”

“In fact, our galaxy is orbited by dozens of known satellite galaxies much closer than Andromeda, the largest and brightest of which is the Large Magellanic Cloud, which is easily visible to the naked eye even from the southern hemisphere. can.”

Globular clusters, such as NGC 1841, are very old systems of stars bound together by gravity into a single structure about 100 to 200 light-years in diameter.

These objects contain hundreds of thousands, or perhaps millions, of stars. The large mass in the cluster's rich stellar center pulls the stars inward, forming a star ball.

These are among the oldest objects known in the universe, relics from the earliest era of galaxy formation.

It is believed that all galaxies contain globular clusters. There are at least 150 such objects in our Milky Way galaxy.

“There are many globular star clusters in the Large Magellanic Cloud,” the astronomers said.

“These objects lie somewhere between open clusters (much less dense and tightly bound) and small, compact galaxies.”

“Increasingly sophisticated observations have revealed that the stellar populations and other characteristics of globular clusters are diverse and complex, but how these dense clusters form is poorly understood. yeah.”

“But all globular clusters have a certain consistency. They are so stable that they can persist for long periods of time, and therefore can be very old.”

“This means that globular clusters often contain large numbers of very old stars, making them similar to 'fossils' in the sky.”

“Just as fossils provide insight into the early development of life on Earth, globular clusters like NGC 1841 provide insight into the very early formation of stars in galaxies.”

Source: www.sci.news