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Discovery of New Stellar Streams Indicate that Milky Way Pulls Stars from its Neighbors

What is the origin of the stars in our Galaxy? The stars visible in the sky at night are from our Milky Way galaxy, and although majority of the stars possibly originated in the Milky Way, a number of them seem to have migrated to our galaxy from other galaxies.

Prognostic proof is derived from streams of stars formed upon interaction of small galaxies with the Milky Way. New evidence for this theory is provided by 11 new stellar streams, found out from data obtained the Dark Energy Survey, carried out at present at the NSF’s Cerro Tololo Inter-American Observatory (CTIO).

Color image of the Dark Energy Survey field. Several of the streams are visible as yellow streaks. (Image credit: Alex Drlica-Wagner (Fermilab), Nora Shipp (U. Chicago), and the DES Collaboration.)

Our Galactic Melting Pot

The Milky Way Galaxy is considered to have been enriched by stars migrating from other galaxies in separate migration incidents. If a small galaxy travels close to the Milky Way, it's gravitational pull attracts coils of stars from the nearest galaxy, which trail at its back in a stream. Various such interactions are considered to have donated stars to Milky Way’s halo.

Eleven New Streams Found by Dark Energy Survey

Eleven new stellar streams, found out from data derived from the Dark Energy Survey (DES), were described in a special session conducted at the American Astronomical Society meeting in Washington, DC on 10th January 2018. Before the discovery, the existence of just close to two dozen stellar streams was known, majority of which were found out from data derived from a precursor survey, the Sloan Digital Sky Survey (SDSS).

DES data have been earlier used to find out a number of dwarf neighboring galaxies of the Milky Way. While it is highly difficult to discover dwarf galaxies as they are diffuse and faint, it is even more challenging to discover stellar streams as their stars are scattered over a huge area of sky. “These discoveries are possible because the Dark Energy Survey is the widest, deepest, and best-calibrated survey out there,” elucidated Alex Drlica-Wagner (Fermilab), one of the members of the DES team.

Crowdsourcing Discoveries with a Public Data Release

Data derived from the initial 3 years of the survey—performed by using the Dark Energy Camera (DECam) on the 4-m Blanco telescope at CTIO—were also made accessible to the public at the same time as the announcement.

Despite the fact that DES was performed mainly to gain an in-depth knowledge of the nature of dark energy, “The great thing about a big astronomical survey like this is that it also opens a door to many other discoveries, like the new stellar streams,” stated Adam Bolton, Associate Director for the Community Science and Data Center at the National Optical Astronomy Observatory (NOAO). “With the DES data now available as a ‘digital sky’ accessible to all, our hope is that the data will lead to the crowdsourcing of new and unexpected discoveries.”

Indeed, the DES data have already enabled diverse science, ranging from studies of Near Earth Orbiting objects to distant quasars formed not long after the Big Bang,” stated Alistair Walker (NOAO), a member of the DES team and the DECam Instrument Scientist.

Ever Larger Astronomical Surveys

The public release of the DES data sustains an inclination toward expanding data sets in astronomy.

The DES data release includes measurements of 400 million stars and galaxies, about twice the number of objects in the SDSS, the premier survey of the last decade. The survey data extend deep and wide, to stars 40 million times fainter than the human eye can see, covering 1/8 of the entire sky.

Knut Olsen, Team Leader of NOAO’s Data Lab

Survey images and catalogs can be accessed from the NOAO Data Lab and the NOAO Science Data Archive. The aim of the NOAO Data Lab is to make possible community re-use of huge data sets, such as the DES data, by allowing visualization, exploration, and analysis of their catalogs and images.

Similar to the way DES is a successor to the SDSS, “The Large Synoptic Survey Telescope (LSST), currently under construction on Cerro Pachon in Chile, is the next generation sky survey after DES,” stated Bolton. “In the 2020s, LSST will deliver a yet wider and deeper view of the Universe—from distant galaxies, to our Milky Way, down to the Solar System—and not just as a still photo, but as a high-definition movie that will capture the rich variability of the sky.”

LSST is anticipated to catalog a massive 18 billion objects in its first year of use, overshadowing the number of objects in the DES as well as SDSS catalogs.

Toward a Big Data Future for Astronomy

The DES outcomes and data release have strong alliance with progressive investments at the National Science Foundation (NSF). “This result is an excellent example of how ‘data mining’—the exploration of large data sets—leads to new discoveries,” proclaimed Richard Green, Director of the NSF’s Division of Astronomical Sciences. “NSF is investing in this approach through our Foundation-wide ‘Harnessing the Data Revolution’ initiative, which encourages fundamental research in data science. We’re expecting a drumbeat of exciting discoveries, particularly when the LSST data floodgates are opened!

According to Bolton, the DES data publicization is a remarkable chance to make ourselves ready for the era of “Big Data.” “It’s a great way for all of us to exercise the new modes of investigation and analysis that will be essential in the LSST era, while also sharpening our understanding of the open questions in astrophysics and cosmology that LSST is being built to address.”

The Cerro Tololo Inter-American Observatory (CTIO) belongs to the National Optical Astronomy Observatory (NOAO), which is controlled by the Association of Universities for Research in Astronomy (AURA) under a collaborative agreement with the National Science Foundation (NSF). NSF is an independent federal agency formed in the year 1950 by Congress to encourage the advances in the field of science. NSF assists fundamental research and people to develop knowledge that revolutionizes the future.

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