A study published last week in Physical Review D, with Ciaran O’Hare (University of Zaragoza, Spain) as lead author, says that a stellar stream is moving towards the Sun at the speed of 500 kilometers per second. It is a collection of stars in the stellar neighborhood, remnants of a dwarf galaxy swallowed by the Milky Way millions of years ago. They have been shredded by gravitational forces, and now they pass through our galaxy. Dark matter being the gravitational support for dwarf galaxies, it is almost certain that the stellar stream contains it. The dark matter particles in the stream can be detected by the dark matter experiment that can be done now.
Dark matter is not like regular matter, and it can be observed only by tracing its gravitational effects. The research team spotted huge masses of dark matter moving along S1 towards the sun. There are tons of these streams all over the galaxy, says O’Hare, and some them are so big that they can be seen in the sky. And we are inside the stream, he added. The stream was spotted by the European Space Agency’s Gaia spacecraft. It was spotted as the thousands of stars in it are of a different chemical structure than the stars in our galaxy. Scientists know of about 30 streams of this sort, but the S1 stream elicits interest because the solar system is inside it now.
The Gaia spacecraft has collected an unbelievably huge amount of data on the stream, giving scientists a plethora of material to work on. Sownak Bose, of the Harvard-Smithsonian Center for Astrophysics, said that the amount of dark matter that the stream may contain can vary depending on the composition of the dwarf galaxy that created them. The potential for further exploration provided by the collected data is tremendous. O’Hare says that since we don’t know much about dark matter, any new piece of new information will help us understand it better.
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