Astronomers have discovered a previously unknown pair of potential satellite galaxies orbiting the Milky Way. The location of these dwarf galaxies suggests that there could be hundreds of other unknown mini-galaxies lurking around us – which could challenge our understanding of the galactic edges.
A satellite galaxy is a cluster of stars, either in a circular blob or halo, that orbit the Milky Way independently of the rest of the galaxy. The largest known satellite of our galaxy is The Large Magellanic Cloud, which contains around 30 billion stars and can be observed with the naked eye. Other known satellites contain only a few hundred thousand or a few million stars.
AND 2020 census of known satellite galaxies suggests that scientists have found a maximum of around 60 satellite galaxies orbiting the Milky Way. However, there is some uncertainty about the actual number of satellite galaxies, mainly because scientists disagree on how large these star clusters should be and how far they should lie from the galactic center to be considered true satellites. NASA.
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But most astronomers agree that there should be many more, currently unknown, satellite galaxies. Based on our current understanding dark matter — which does not react with light, but gravitationally interacts with visible matter and it makes up about 27% of the mass of the universe — researchers have long assumed that the Milky Way should have around 220 satellite galaxies. Our inability to detect many more of them is often referred to as the “missing satellites problem.”
In a new study published June 8 in the journal Publications of the Astronomical Society of Japan, researchers discovered two new potential satellite galaxies, Sextans II and Virgo III. Located approximately 411,000 and 492,000 light-years from Earth, the satellites are likely to be ultra-compact dwarf galaxies (UCDs) – collections of old stars clustered close together, making them brighter than other satellite galaxies.
However, the discoveries do not help solve the problem of missing satellites. Instead, the location and orientation of these potential satellites suggests that there are even more satellite galaxies than scientists originally realized. This raises a new problem that the researchers have dubbed the “too many satellites problem.”
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Scientists discovered the UCD using the Hyper Suprime-Cam (HSC) attached to Japan’s Subaru Telescope at the Mauna Kea Observatories in Hawaii. The instrument has spent the past few years scanning a region of space about 33 light-years across. Based on the estimated 220 satellite galaxies postulated by the missing satellite problem, a region of this size should have an average of around four satellite galaxies, This was recently reported by Universe Today.
However, the latest discoveries bring the total number of satellites found by HSC in the region to nine. If this concentration of satellites is consistent around the Milky Way, it would mean that there could be at least 500 satellite galaxies around the Milky Way, the researchers wrote declaration.
In the past, scientists have proposed several solutions to the problem of missing satellites, including that some satellite galaxies are hiding behind larger satellites and that others are so diffused as to be almost undetectable with current technology. However, these factors are unlikely to explain the overabundance of stars, so scientists have no real way to explain the new results.
“The next step is to use a more powerful telescope to capture a wider view of the sky,” study co-author Masahi Chiba, an astronomer at Tohoku University in Japan, said in a statement. This should help clarify how common satellite galaxies really are, he added.
One such telescope is on the way Vera C. Rubin Observatory — state-of-the-art equipment equipped the largest digital camera in the world, which is expected to go online in 2025, Chiba said. “I hope many new satellite galaxies will be discovered.”