ESA’s Gaia spots a ‘ghost’ galaxy next to Milky Way

Milky Way collides with another galaxy

Dubbed Antlia 2 (or Ant 2), the galaxy is remarkably faint but is located only about 130,000 light-years away from our galaxy. In addition, now the milky Way absorbs dwarf elliptical galaxy with a diameter of about 10 thousand light years.

A team of researchers from the University of Cambridge along with an worldwide team of astronomers has recently discovered a dwarf galaxy which is situated on the outskirts of Milky Way. One such stellar stream, dubbed S1 and discovered previous year by scientists examining data from the European Space Agency's Gaia satellite, passes directly through the path of our sun.As our solar system speeds through the outer reaches of the Milky Way, it flies through dark matter at around 230 kilometres per second ( around 143 miles per second). "We are wondering whether this galaxy is just the tip of an iceberg, and the Milky Way is surrounded by a large population of almost invisible dwarfs similar to this one". Like many other dwarf galaxies, Ant 2 - quite old, and most of its stars are old, small and with a low metallicity (content of elements heavier than helium).

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.

After the discovery, the lead researcher Pieter van Dokkum of Yale University said, "This invisible, mysterious substance is by far the most dominant aspect of any galaxy". In a paper presented at the online library of preprints arXiv.orgscientists describe 2 Antlia (Ant 2) as a small galaxy,"Ghost", unique among about 60 companions of the milky Way. But a dedicated research team has managed to spot Ant 2 by venturing deep into the data collected by the European Space Agency's Gaia satellite, which has so far observed almost 1.7 billion stars.

Gaia is on a mission to create the richest star catalog ever made with high precision measurements of nearly 1.7 billion stars.

In April past year, a team of astronomers found that stars in the vicinity of the Solar system are moving in the direction opposite to the direction of rotation of our galaxy, writes National Geographic. They also found that the ghost galaxy's mass is much lower than expected for an object of its size. These old stars often encountered in the dark galaxies shine with a palpitating blue light that throbs at a rate signifying their intrinsic glare permitting researchers to zero in on their distance.

"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", explained co-author Vasily Belokurov of Cambridge University.

"But", he continued, "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". Using the Australian telescope AAT scientists have obtained spectra of more than 100 red giants Ant 2, and then the neighboring galaxy for a long time disappeared from sight.

What remains unexplained is the object's giant size, says astronomer Sergey Koposov at Carnegie Mellon University. The reason behind Antlia 2 having too little mass is that the galaxy is "being taken apart by the Galactic tides of the Milky Way", astronomers believe.

"From these properties we conclude that Antlia-2 inhabits one of the least dense Dark Matter (DM) halos probed to date". The study concedes that current iterations of WIMP detectors will likely not see dark matter from the S1 stream.

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