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Six galaxies discovered with scarce dark matter

25 September 2019

Under the leadership of Pavel Mancera Piña (University of Groningen and ASTRON), an international team of astronomers has discovered six dim dwarf galaxies that contain hardly any dark matter. This is rare, as it is expected that most of the dim dwarf galaxies are only held together by means of a large amount of dark matter. The researchers will soon publish their findings in The Astrophysical Journal Letters .

The Westerbork Synthese Radio Telescoop. (ASTRON)
The Westerbork Synthese Radio Telescoop. (ASTRON)

For their research, the astronomers used the satellite dishes of the Dutch Westerbork Synthesis Radio Telescope and those of the American Very Large Array. They looked at six dim dwarf galaxies between 240 million and 320 million light years away. Until now, this type of galaxy has not been studied much because it does not emit much light.

The name ‘dwarf galaxies’ refers to the weak light produced by the galaxies, not to their size. They are actually just as big as our own Milky Way, but contain far fewer stars. The prevailing idea is that such large dwarf galaxies can only exist if they are held together by dark matter.

But to the surprise of the researchers, after studying the dwarf galaxies, it appears that the dim dwarf galaxies and their environments don’t contain any dark matter. According to current theories, these six galaxies are therefore unable to exist.

In their scientific publication, the researchers posit a few explanations for the absence of dark matter, but in fact – as they say themselves – they still haven’t come up with a good explanation.

Two galaxies containing little dark matter were previously found by another research group. Far more details are known about the six new galaxies.

Last modified:14 October 2019 2.17 p.m.
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