Gaia Satellite Spots Ghost Galaxy On Outskirts Of Milky Way

Posted: Nov 13 2018, 2:26pm CST | by , Updated: Nov 13 2018, 2:32pm CST, in Latest Science News


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Gaia fings Ghost Galaxy
Image Credit: V. Belokurov based on the images by Marcus and Gail Davies and Robert Gendler

Astronomers Spots Ghost Galaxy that Remained Invisible Earlier

The hardly visible Galaxy is situated behind the discs of our own Milky Way Galaxy

It is 10,000 times fainter than any satellite in the milky way, it has been dubbed ANT 2 by the scientists.

Scientists consider it a dwarf galaxy the formed during early stages of the universe.

A team of researchers from the University of Cambridge along with an international team of astronomers has recently discovered a dwarf galaxy which is situated on the outskirts of Milky Way. The team discovered the new galaxy while they were studying the data collected and sent by the European Space Agency's Gaia satellite.

According to their findings that the researchers published online today, the dwarf galaxy which has been coined Antlia 2 (Ant 2), the location behind the Milky way discs and very low density of the dwarf galaxy were the main reasons why it was kept hidden from astronomers till date.

During the early stage of the universe, dwarf galaxies were the first to be formed, being so ancient most of their stars are very old with little mass and low presence of metals. But if compared with dwarf satellites that are present in our galaxy, the size of Ant 2 is quite huge, it is around one third the size of our own Milky Way galaxy, which is as big as an LMC (Large Magnetic Cloud).

What’s unusual is that it emits a very low amount of light, the amount of light it emits is around 10,000 times fainter than LMC, which made the scientists conclude that either it is too large which results in low luminosity or its stars are too dim for its size.

"This is a ghost of a galaxy," said Gabriel Torrealba, the paper's lead author. "Objects as diffuse as Ant 2 have simply not been seen before. Our discovery was only possible thanks to the quality of the Gaia data."

ERA’s Gaia Mission has proved to be a great asset for astronomers worldwide, due to data provided by Gaia, researchers worldwide have been able to catalog more than 1.7 billion stars with precise details about their size and measurements. During starting months of this year, the second set of data obtained by Gaia was released to scientists from different countries, the new set of data made available information about details of Milky Way that were not available for study earlier.

The team wrote that all stars in the ghost galaxy were moving together and the galaxy always maintained a distance of around 130,000 light years distance from our own galaxy. The researchers were also surprised when they estimated the mass of the ghost galaxy, it was very low for its vast size.

Studying RR Lyrae stars had been crucial in finding the dwarf galaxy, RR Lyrae stars can be categorized by being metal-poor and have formed very long ago. These stars change their luminosity after every half day period, these changes in brightness variations helped in finding them in the vast cosmos.

"RR Lyrae had been found in every known dwarf satellite, so when we found a group of them sitting above the Galactic disc, we weren't totally surprised," said co-author Vasily Belokurov from Cambridge's Institute of Astronomy. "But when we looked closer at their location on the sky it turned out we found something new, as no previously identified object came up in any of the databases we searched through."

According to researchers the gap between other galactic dwarfs and ANT 2 is astonishing and it seems scientists and researchers have no proper information how these celestial bodies formed, if scientists can solve the Ant 2 puzzle and few more similar cases, they might be able to connect some missing dots in current physics about the formation of dwarf galaxies and how early Universe came into being.

"The simplest explanation of why Ant 2 appears to have so little mass today is that it is being taken apart by the Galactic tides of the Milky Way," said co-author Sergey Koposov from Carnegie Mellon University. "What remains unexplained, however, is the object's giant size. Normally, as galaxies lose mass to the Milky Way's tides, they shrink, not grow."

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The Author

<a href="/latest_stories/all/all/47" rel="author">Hira Bashir</a>
The latest discoveries in science are the passion of Hira Bashir (). With years of experience, she is able to spot the most interesting new achievements of scientists around the world and cover them in easy to understand reporting.




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