The Milky Way may be surrounded by 'too many' mini galaxies, new discoveries reveal

By Harry Baker published 12 hours ago

Astronomers have just discovered two dwarf galaxy candidates orbiting our galaxy. The orientation of these entities suggests there could be up to 500 similar stellar clusters circling the Milky Way, which is more than double previous estimates.



A photo of the Subaru Telescope against the night sky with the Milky Way clearly visible
The potential dwarf galaxies, Sextans II and Virgo III, were spotted by the Hyper Suprime-Cam (HSC) attached to Japan's Subaru Telescope. (Image credit: Hideaki Fujiwara, Credit:NAOJ)

Astronomers have discovered a previously unknown pair of potential satellite galaxies orbiting the Milky Way. The location of these dwarf galaxies suggests that hundreds of other unknown mini-galaxies could be hiding around us — potentially challenging our understanding of the galaxy's edges.

A satellite galaxy is a clump of stars, either in a circular blob or a halo-like shape, that orbit the Milky Way independently from the rest of the galaxy. Our galaxy's largest-known satellite is the Large Magellanic Cloud, which holds around 30 billion stars and can be viewed with the naked eye. Other known satellites only contain a few hundred thousand or a couple of million stars.

A 2020 census of known satellite galaxies suggests scientists have found a maximum of around 60 satellite galaxies orbiting the Milky Way. However, there is some uncertainty about the true number of satellite galaxies, largely because scientists disagree over how large these star clusters should be and how far they should lie from the galactic center to be counted as true satellites, according to NASA.

But most astronomers agree that there should be many more, currently unknown, satellite galaxies out there. Based on our current understanding of dark matter — which doesn't react with light but interacts gravitationally with visible matter and makes up around 27% of the universe's mass — researchers have long assumed that the Milky Way should have around 220 satellite galaxies. Our inability to spot many more of these is often referred to as the "missing satellites problem."

More:
https://www.livescience.com/space/astronomy/the-milky-way-may-be-surrounded-by-too-many-mini-galaxies-new-discoveries-reveal