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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.

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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 Found Ancient Star Formed By Big Bang

This suggests that it could be as little as one generation removed from the beginning of the universe, the researchers noted

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Astronomers discover ancient star formed by Big Bang, pixabay

A team of astronomers have found what could be one of the universe’s oldest stars, almost entirely made of materials formed by the Big Bang.

Residing in the same part of the Milky Way galaxy as our own solar system, the star is believed to be up to 13.5 billion years old which is evidenced by its extremely low metal content, or metallicity, Xinhua news agency reported.

According to co-author Andrew Casey, it was previously believed that the first stars that formed in the universe could not possibly still exist today.

“The findings are significant because for the first time we have been able to show direct evidence that very ancient, low mass stars do exist, and could survive until the present day without destroying themselves,” Casey said.

Keplar, NASA
According to co-author Andrew Casey, it was previously believed that the first stars that formed in the universe could not possibly still exist today. VOA

The metallicity of stars increases as they are born and die, in a cycle which results in the creation of more and more heavy metals, with the Earth’s sun being around 100,000 generations down that line and holding a metal content roughly equal to 14 Jupiters.

Stars created at the beginning of the universe, however, would have consisted entirely of elements like hydrogen, helium and small amounts of lithium – meaning the extremely low metallicity of the newly discovered star, about the same as the planet Mercury.

This suggests that it could be as little as one generation removed from the beginning of the universe, the researchers noted.

Also Read- Artificial Intelligence Will Match Humans By 2062: Experts

Up until around 1990, scientists believed that only massive stars could have formed in the early stages of the universe, and could never be observed because they burn through their fuel so quickly and die.

However, the new study has shown that it is possible for low mass stars to last as long as the 13 billion years since the Big Bang — Red Dwarf stars for instance, which have a fraction of the mass of the sun, are thought to live for trillions of years. (IANS)