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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

Scientists spot massive ice deposits on Mars

Recent observations by MRO's ground-penetrating Shallow Radar instrument revealed a buried ice layer that covers more ground than the state of New Mexico.

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Scientists found layers of ice on the surface of Mars. Wikimedia Commons
  • Recently, scientists have found layers of ice on the Martian land.
  • Scientists think this ice might be a useful source of water for future humans.
  • The researchers had researched 8 locations on the surface of Mars.

Scientists have unearthed thick and massive deposits of ice in some regions on Mars.

The images taken by the High-Resolution Imaging Science Experiment (HiRISE) camera aboard NASA’s Mars Reconnaissance Orbiter (MRO) showed the three-dimensional structure of massive ice deposits on Mars.

The ice sheets extend from just below the surface to a depth of 100 meters or more and appear to contain distinct layers.

It extending downward from depths as shallow as 1 to 2 meters below the surface, which could preserve a record of Mars’ past climate, the researchers noted in the journal Science.

This ice which was found can help scientists understand the climate history of Mars. IANS
This ice which was found can help scientists understand the climate history of Mars. IANS

“We expect the vertical structure of Martian ice-rich deposits to preserve a record of ice deposition and past climate,” said Colin M. Dundas, from the US Geological Survey.

“They might even be a useful source of water for future human exploration of the red planet,” Dundas added.

The researchers investigated eight locations on Mars and found thick deposits cover broad regions of the Martian mid-latitudes with a smooth mantle.

However, erosion in these regions creates scarps that expose the internal structure of the mantle.

The scarps are actively retreating because of sublimation of the exposed water ice.

The layers of ice can be used as water source by future humans on Mars, VOA
The layers of ice can be used as water source by future humans on Mars, VOA

The ice deposits likely originated as snowfall during Mars’ high-obliquity periods and have now compacted into massive, fractured, and layered ice.

Previous researchers have revealed that the Red Planet harbours subsurface water ice.

Recent observations by MRO’s ground-penetrating Shallow Radar instrument revealed a buried ice layer that covers more ground than the state of New Mexico.

NASA’s Phoenix lander had also dug up some ice near the Martian north pole in 2008, however, it is not clear if that is part of the big sheet. IANS