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Astronomers Discover Dragonfly 44, a Milky Way–sized Galaxy consisting of 99.99 percent Dark Matter

Dragonfly 44's mass is estimated to be one trillion times the mass of the Sun, which is similar to the mass of the Milky Way

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Little Cub galaxy
The Little Cub galaxy - so called because it sits in the Ursa Major or Great Bear constellation. Galaxy (Representational Image). Wikimedia
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New York, August 27, 2016: An international team of astronomers has found a massive galaxy — about the size of the Milky Way — that consists almost entirely of dark matter.

The galaxy, Dragonfly 44, is located in the nearby Coma constellation and had been overlooked until last year because of its unusual composition. It is a diffuse “blob” about the size of the Milky Way, but with far fewer stars, the researchers said.

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“Very soon after its discovery, we realised this galaxy had to be more than meets the eye. It has so few stars that it would quickly be ripped apart unless something was holding it together,” said lead author Pieter van Dokkum from Yale University in New Haven, Connecticut.

Dragonfly 44’s mass is estimated to be one trillion times the mass of the Sun, which is similar to the mass of the Milky Way. However, only one-hundredth of one percent of that is in the form of stars and “normal” matter.

The dark galaxy Dragonfly 44. The image on the left is a wide view of the galaxy. Source: VOA news
The dark galaxy Dragonfly 44. The image on the left is a wide view of the galaxy.
Source: VOA news

The other 99.99 percent is in the form of dark matter — a hypothesised material that remains unseen but may make up more than 90 percent of the universe, the researchers reported in a paper published in the Astrophysical Journal Letters.

Van Dokkum’s team was able to get a good look at Dragonfly 44 thanks to the W.M. Keck Observatory and the Gemini North telescope, both in Hawaii.

Astronomers used observations from Keck, taken over six nights, to measure the velocities of stars in the galaxy.

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They used the eight-metre Gemini North telescope to reveal a halo of spherical clusters of stars around the galaxy’s core, similar to the halo that surrounds our Milky Way galaxy.

Star velocities are an indication of the galaxy’s mass, the researchers noted. The faster the stars move, the more mass its galaxy will have.

“Amazingly, the stars move at velocities that are far greater than expected for such a dim galaxy. It means that Dragonfly 44 has a huge amount of unseen mass,” co-author Roberto Abraham of the University of Toronto, explained.

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  • Kabir Chaudhary

    A great find by the astronomers in the field of space exploration. After reading about Dragonfly 44, i realised that the Universe have many hidden secrets and that humans will always be curious to explore it.

  • Manakas

    I’m curious as to what is in the center of the galaxy. Does it also have a supermassive black hole made out of regular matter or is there some equally dense dark matter equivalent of a black hole?

  • Kabir Chaudhary

    A great find by the astronomers in the field of space exploration. After reading about Dragonfly 44, i realised that the Universe have many hidden secrets and that humans will always be curious to explore it.

  • Manakas

    I’m curious as to what is in the center of the galaxy. Does it also have a supermassive black hole made out of regular matter or is there some equally dense dark matter equivalent of a black hole?

Next Story

NASA positive on next planet-hunting mission launch

The spacecraft will be looking for a phenomenon known as a transit, where a planet passes in front of its star, causing a periodic and regular dip in the star's brightness

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NASA to release two missions focused on moon soon in 2022. Pixabay
NASA positive about next planet-hunting mission. Pixabay

Meteorologists with the US Air Force 45th Space Wing have predicted an 80 per cent chance of favourable weather for SpaceX Falcon 9 rocket’s launch with NASA’s Transiting Exoplanet Survey Satellite aimed at detecting planets outside our solar system.

ISS is a permanent base for astronauts stationed in the outer sky. Wikimedia Commons
This mission has NASA very positive. Wikimedia Commons

The launch is scheduled for Sunday at 6.32 p.m. (4.02 a.m. on Monday, India time) on a SpaceX Falcon 9 rocket from Space Launch Complex 40 at Cape Canaveral Air Force Station in Florida. The primary weather concern for the launch day are strong winds, NASA said in a statement late Saturday. The survey, also known as Tess, is NASA’s next step in the search for exoplanets, including those that could support life.

Once in orbit, Tess will spend about two years surveying 200,000 of the brightest stars near the Sun to search for planets outside our solar system. Tess will find the most promising exoplanets orbiting relatively nearby stars, giving future researchers a rich set of new targets for more comprehensive follow-up studies, including the potential to assess their capacity to harbour life.

Also Read: NASA sending first-ever mission to study Mars’ deep interior

With the help of a gravitational assist from the Moon, the spacecraft will settle into a 13.7-day orbit around Earth, NASA said in an earlier statement. Sixty days after the launch and following tests of its instruments, the satellite will begin its initial two-year mission. Four wide-field cameras will give Tess a field-of-view that covers 85 per cent of our entire sky.

NASA Kepler spaceship will be used.

Within this vast visual perspective, the sky has been divided into 26 sectors that Tess will observe one by one. The first year of observations will map the 13 sectors encompassing the southern sky, and the second year will map the 13 sectors of the northern sky.

The spacecraft will be looking for a phenomenon known as a transit, where a planet passes in front of its star, causing a periodic and regular dip in the star’s brightness. NASA’s Kepler spacecraft used the same method to spot more than 2,600 confirmed exoplanets, most of them orbiting faint stars 300 to 3,000 light-years away. IANS