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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?

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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?

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Another Space Telescope Shuts Down: NASA

Launched by space shuttles in the 1990s, Hubble and Chandra are part of NASA's Great Observatories series.

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NASA's Chandra Observatory back in action. Pixabay

Another NASA space telescope has shut down and halted science observations.

Less than a week after the Hubble Space Telescope went offline, the Chandra X-ray Observatory did the same thing. NASA said Friday that Chandra automatically went into so-called safe mode Wednesday, possibly because of a gyroscope problem.

Hubble went into hibernation last Friday because of a gyroscope failure.

NASA
This illustration made available by NASA shows the Chandra X-ray Observatory. On Oct. 12, 2018, the space agency said that the telescope automatically went into so-called safe mode on Oct. 10, possibly because of a gyroscope problem. VOA

Both orbiting observatories are old and in well-extended missions: Hubble is 28, while Chandra is 19. Flight controllers are working to resume operations with both.

NASA said it’s coincidental both went “asleep” within a week of one another. An astronomer who works on Chandra, Jonathan McDowell of the Harvard-Smithsonian Center for Astrophysics, tweeted Friday that “Chandra decided that if Hubble could have a little vacation, it wanted one, too.”

Also Read: Astronomers Capture 15,000 Galaxies Using Hubble Telescope

Launched by space shuttles in the 1990s, Hubble and Chandra are part of NASA’s Great Observatories series. The others are the Compton Gamma Ray Observatory, which was also launched in the 1990s but eventually failed and was destroyed, and the Spitzer Space Telescope, launched in 2003 and still working. Each was intended to observe the cosmos in different wavelengths. (VOA)