New Rivers of Stars in the Milky Way

DES deep image

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The first three years of data obtained by the Dark Energy Survey have been released to the public today. Using these data, astronomers have discovered 11 new stellar streams around our own Milky Way galaxy -- evidence of the “building blocks” out of which our Galaxy was formed. Astronomers have involved the public in the naming of these new astronomical discoveries, some of which have received Aboriginal names.

The Dark Energy Survey (DES) collaboration is an international team of scientists, including researchers from the Australian Astronomical Observatory, whose primary goal is to better understand dark energy, the mysterious force believed to be accelerating the expansion of the Universe.

Today, the DES collaboration has publically released their first three years of data, which compiles information on more than 400 million astronomical objects, including distant galaxies billions of light years away as well as stars in our own Galaxy.

The enormous DES dataset (hundreds of terabytes’ worth of images) covers about 5,000 square degrees, or one eighth of the entire sky, and includes more than 100,000 exposures. These data were obtained with the Dark Energy Camera, one of the world’s most sensitive digital imaging devices, mounted on the U.S. National Science Foundation’s 4m Blanco Telescope at Cerro Tololo Inter-American Observatory in Chile.

While DES was designed with the primary goal of understanding dark energy and its effect on the entire universe, astronomers have also discovered something new, not in the farthest reaches of the cosmos, but near to our own Galaxy, the Milky Way.

Digging in the very rich and deep DES data, astronomers have found 11 new stellar streams, or “rivers of stars” moving around our Galaxy. These faint filaments are the remnants of dwarf galaxies or other clusters of stars that have been ripped apart by the huge gravity of their monster neighbor, own our Galaxy.

“Just like we can tell how a finished building was made by looking at the piles of leftover steel or wood or bricks, we can tell how the Milky Way formed by looking at the remains of the cosmic ‘construction site’ --- the long filaments of stars orbiting at the edges of the Galaxy”, says AAO Instrument Scientist and DES Collaboration member Dr Kyler Kuehn.

The Milky Way grows by pulling in, ripping apart and absorbing these smaller systems. As groups of stars are torn away from their original system, they are stretched to form streams across the sky.

“The streams are not so close that they’re lost among the billions of other stars of the Milky Way, but they’re not so far away that they’ve escaped the gravitational pull of the Milky Way“, says Dr Kuehn.

However, stellar streams are extremely difficult to find since they are composed of relatively few stars spread out over a large area of sky.

Prior to the new discoveries by DES, only about two dozen stellar streams had been seen. Many of the brighter streams were found by the Sloan Digital Sky Survey, another large telescopic survey operating in the United States, but the fainter streams avoided detection entirely – until now.

“Due to the large field of view and extreme sensitivity of the Dark Energy Camera, with just these three years of data from one single instrument, we have increased by 50% the number of known stellar streams,” Dr Kuehn explains.

Unlike some celestial objects that have very specific naming conventions according to the International Astronomical Union, stellar streams have a bit of flexibility in how they are named. The DES collaboration engaged the public in Australia and Chile to name the stellar streams after aquatic words in native languages from aboriginal Australia and northern Chile.

“The people attending the public events where we unveiled these discoveries were very enthusiastic. I don’t know if they are aware how rarely people get to name things that are newly discovered in space—or anywhere, for that matter—but I was pretty excited about it", says Dr Kuehn.

Dr Kuehn worked with an Aboriginal storyteller and tribal elders to pick culturally sensitive and appropriate names in native languages.

“I wanted to honor the long history of aboriginal Australians doing astronomy. Today's Aboriginal populations are the caretakers of some of the oldest continuous cultures on the planet, and their collective knowledge—including astronomical observations—date back tens of thousands of years”, Dr Kuehn says.

With a list of half a dozen potential names, Dr Kuehn spoke at two different public events – one including about 100 adults at the Sydney’s Royal Botanic Gardens, and the other including about 40 preschool children – and asked the attendees to cheer to select their favorites.

Based on the feedback from these two groups, two of the newly-discovered stellar streams were given names derived from Aboriginal words:

  • Wambelong, meaning Crazy Water in the Gamilaraay language, is the name of a stream that runs near the Anglo-Australian Telescope in rural New South Wales.
  • Turranburra is the Dharug name for the Lane Cove River that runs near the headquarters of the Australian Astronomical Observatory in Sydney’s northern suburbs.

Meanwhile in Chile, DES collaboration members worked with students in the town of Vicuña, near Cerro Tololo Inter-American Observatory to name more of the streams. Students there decided to provide the Aymara name Aliqa Uma, meaning Quiet Water; two Quechua names, Palca, meaning Crossing Rivers, and Willka Yaku, or Sacred Water; and two Spanish names, Elqui and Turbio.

The rest of the new stellar streams, located in the sky near the Indus constellation, received names of Indian rivers: Indus, Jhelum, Chenab and Ravi.

Scientists hope the names build connections between the nations that host the observatories and the discoveries they make about the Universe that hosts us all.

 

The AAO is a division of the Department of Industry, Innovation and Science.

The Dark Energy Survey is a collaboration of more than 400 scientists from 26 institutions in seven countries. Funding for the DES Projects has been provided by the U.S. Department of Energy Office of Science, U.S. National Science Foundation, Ministry of Science and Education of Spain, Science and Technology Facilities Council of the United Kingdom, Higher Education Funding Council for England, ETH Zurich for Switzerland, National Center for Supercomputing Applications at the University of Illinois at Urbana- Champaign, Kavli Institute of Cosmological Physics at the University of Chicago, Center for Cosmology and Astro-Particle Physics at Ohio State University, Mitchell Institute for Fundamental Physics and Astronomy at Texas A&M University, Financiadora de Estudos e Projetos, Fundação Carlos Chagas Filho de Amparo à Pesquisa do Estado do Rio de Janeiro, Conselho Nacional de Desenvolvimento Científico e Tecnológico and Ministério da Ciência e Tecnologia, Deutsche Forschungsgemeinschaft, and the collaborating institutions in the Dark Energy Survey, the list of which can be found at  www.darkenergysurvey.org/collaboration.

 

Publication details:

The results of this research were presented today at a special session of the American Astronomical Society Annual Meeting occurring this week in Washington, DC, and are submitted for publication in The Astrophysical Journal.

The DES data can be accessed online here: https://des.ncsa.illinois.edu/releases/dr1.

Science Contacts:

- Dr Kyler Kuehn

Instrument Scientist,

Australian Astronomical Observatory

M: +61 405 073 010 E: kyler.kuehn@aao.gov.au

Media contact:

- Dr Ángel López-Sánchez,

Research Astronomer and Science Communication Officer,

Australian Astronomical Observatory and Macquarie University

M: +61 406 265 917 E: angel.lopez-sanchez@aao.gov.au

Images:

DES deep image

Caption: This image shows the entire Dark Energy Survey field of view – roughly one-eighth of the sky – captured by the Dark Energy Camera, with different colors corresponding to the distance of stars. (Blue is closer, green is further away, red is even further.) Several stellar streams are visible in this image as yellow, blue and red streaks across the sky.

Credit: Dark Energy Survey.

This image is available at: https://www.aao.gov.au/files/press/2018-01-11-DES-AAO-Stellar-Streams-Fig01.jpg

DES Stellar Streams map

Caption: This image shows the full area of sky mapped by the Dark Energy Survey, and the eleven newly discovered stellar streams. Four of the streams in this diagram - ATLAS, Molonglo, Phoenix and Tucana III – were previously known. The others were discovered using the Dark Energy Camera, one of the most powerful astronomical cameras on earth.

Credit: Dark Energy Survey.

This image is available at: https://www.aao.gov.au/files/public/images/2018-01-11-DES-AAO-Stellar-Streams-Fig02.jpg

The 4m Blanco Telescope at Cerro Tololo Inter-American Observatory in Chile, where the Dark Energy Camera, the main instrument used for the Dark Energy Survey (DES) and one of the world’s most sensitive digital imaging devices, is mounted.

Caption: The 4m Blanco Telescope at Cerro Tololo Inter-American Observatory in Chile, where the Dark Energy Camera, the main instrument used for the Dark Energy Survey (DES) and one of the world’s most sensitive digital imaging devices, is mounted.

Credit: Fermilab.

This image is available at: https://www.aao.gov.au/files/public/images/2018-01-11-DES-AAO-Stellar-Streams-Fig03.jpg

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