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Ghostly galaxy without dark matter stuns astronomers

To find an explanation, the team is already hunting for more dark-matter deficient galaxies as they analyse Hubble images of 23 ultra-diffuse galaxies

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Countless galaxies exist in the universe, each hiding secrets that humankind is yet to unearth. Pixabay
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  • Astronomers discovered galaxy missing its dark matter
  • Dark matter is believed to be integral to any galaxy
  • It is the glue which holds everything together

In a shocking discovery, astronomers have found a galaxy that is missing most — if not all — of its dark matter. This discovery of the galaxy NGC 1052-DF2, detailed in the journal Nature, challenges currently-accepted theories of and galaxy formation and provides new insights into the nature of dark matter.

Black hole in milky way
Astronomers discovered a galaxy missing its dark matter. VOA

“Dark matter is conventionally believed to be an integral part of all galaxies — the glue that holds them together and the underlying scaffolding upon which they are built,” explained study co-author Allison Merritt from Yale University in the US and the Max Planck Institute for Astronomy, Germany.

“This invisible, mysterious substance is by far the most dominant aspect of any galaxy. Finding a galaxy without any is completely unexpected; it challenges standard ideas of how galaxies work,” said lead researcher Pieter van Dokkum of Yale University. “There is no theory that predicts these types of galaxies — how you actually go about forming one of these things is completely unknown,” Merritt said.

For the study, the researchers used the NASA/European Space Agency’s Hubble Space Telescope and several other observatories. Hubble helped to accurately confirm the distance of NGC 1052-DF2 to be 65 million light-years and determined its size and brightness.

Saraswati
Dark matter is the glue which holds everything together in a galaxy. Wikimedia

Based on these data the team discovered that the newly discovered galaxy is larger than the Milky Way, but contains about 250 times fewer stars, leading it to be classified as an ultra diffuse galaxy. “I spent an hour just staring at this image,” van Dokkum said as he recalled first seeing the Hubble image of NGC 1052-DF2.

“This thing is astonishing: a gigantic blob so sparse that you see the galaxies behind it. It is literally a see-through galaxy,” he added. Further measurements of the dynamical properties of 10 globular clusters orbiting the galaxy allowed the team to infer an independent value of the galaxies mass.

This mass is comparable to the mass of the stars in the galaxy, leading to the conclusion that NGC 1052-DF2 contains at least 400 times less dark matter than astronomers predict for a galaxy of its mass, and possibly none at all.

Also Read: Milky Way’s neighbouring galaxy is of same size, not bigger

This discovery is unpredicted by current theories on the distribution of dark matter and its influence on galaxy formation. The discovery of NGC 1052-DF2 demonstrates that dark matter is somehow separable from galaxies. This is only expected if dark matter is bound to ordinary matter through nothing but gravity.

Cosmic rays
Dark matter is integral to all galaxies. Pixabay

Meanwhile, the researchers already have some ideas about how to explain the missing dark matter in NGC 1052-DF2. Did a cataclysmic event such as the birth of a multitude of massive stars sweep out all the gas and dark matter? Or did the growth of the nearby massive elliptical galaxy NGC 1052 billions of years ago play a role in NGC 1052-DF2’s dark matter deficiency?

These ideas, however, still do not explain how this galaxy formed. To find an explanation, the team is already hunting for more dark-matter deficient galaxies as they analyse Hubble images of 23 ultra-diffuse galaxies — three of which appear to be similar to NGC 1052-DF2. IANS

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Astronomers Capture 15,000 Galaxies Using Hubble Telescope

Hubble can provide some of the most sensitive space-based ultraviolet observations possible.

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Hubble Telescope
Hubble Telescope. Flickr

On one of the largest panoramic views of star birth, astronomers using the ultraviolet vision of NASAs Hubble telescope have assembled an image that features approximately 15,000 galaxies, about 12,000 of which are forming stars.

This image is a portion of the GOODS-North field, which is located in the northern constellation Ursa Major, NASA said in a statement Thursday.

The image straddles the gap between the very distant galaxies, which can only be viewed in infrared light, and closer galaxies, which can be seen across a broad spectrum.

Galaxy, hubble telescope
Representational Image of Galaxy. Wikimedia Commons.

The light from distant star-forming regions in remote galaxies started out as ultraviolet, but the expansion of the universe shifted the light into infrared wavelengths.

Also Read: NASA’s Parker Solar Probe Launches Successfully

By comparing images of star formation in the distant and nearby universe, astronomers glean a better understanding of how nearby galaxies grew from small clumps of hot, young stars long ago, NASA said.

Because Earth’s atmosphere filters most ultraviolet light, Hubble can provide some of the most sensitive space-based ultraviolet observations possible. (IANS)