Researchers have found a hidden dwarf galaxy revolving around our own Milky Way, and it could revolutionize our understanding of how dark matter grips galaxies together. The reason this galaxy has stayed hidden is that it is extremely faint, actually, it's the faintest satellite galaxy we have discovered to date. And the discovery recommends that there might be many more of these dark galaxies waiting out in deep space. Discovering out more about our galaxy's satellites could be the main key to lastly understanding how galaxies form, and the starring role mysterious dark matter plays in grasping everything together.
There are by this time around 50 galaxies that we have identified that are revolving around our own galaxy, and almost 40 of them are faint, which sets them in the group of so-called dwarf spheroidal galaxies. Fifty satellite galaxies might seem like a lot, but the difficulty is that our present understanding of dark matter and how it supports galaxies form put forward that we should have more than 50 satellites galaxies revolving around our own galaxy. This is what's known as the unknown satellite problem, and until now, astrophysicists have not been able to give details about what's going on, whichever our understanding of dark matter is mistaken, or all of these satellites galaxies are hiding in plain sight.
Now new study proposes the latter might be possible.
Till now, we have not had the ability to identify any galaxies much fainter than a complete magnitude of –8. Complete magnitude is the brightness of a cosmic body as it would be observed at a distance of 10 parsecs far away, that's 32.6 light-years. For comparison, the complete magnitude in the ocular waveband, the waveband we can see, for the Andromeda galaxy is –21.77, and the Enormous Magellanic Cloud is –18.35. So while –8 is too much faint, this recently discovered satellite is an entire order of magnitude darker than that, with a complete magnitude of –0.8, marking it the faintest satellite galaxy yet discovered by human beings. The recently discovered satellite galaxy has been named Virgo I because it lies in the course of the Virgo constellation in our night sky.
Tohoku University
Virgo I was discovered by using the 8.2-meter Subaru Telescope in Hawaii, and because of its huge aperture, it can take in a whole lot extra light than any other telescopes. The Subaru telescope was capable of scanning a huge section of the night sky with the help an instrument called the Hyper Suprime-Cam (HSC) and observed for any areas with an above-density of stars. It was then able to inspect those regions more thoroughly to look for proof of very faint galaxies. According to this data, it was able to separate the incredibly faint dwarf galaxy Virgo I, which is almost 248 light-years across, and it is situated approximately 280,000 light-years from our Sun.
One of the scientists Daisuke Homma, from Tohoku Universityin Japan said, "We have wisely inspected the first data of the Subaru Strategic Survey with HSC and discovered an obvious over-density of stars in Virgo with very great statistical importance, viewing a characteristic design of an antique cosmological system in the color-magnitude diagram. Astonishingly, this is one of the faintest satellite galayies, with a complete magnitude of –0.8 in the ocular waveband. This is actually a galaxy because it is spatially stretched with a radius of 124 light years, systematically bigger than a globular cluster with similar luminosity."
The thrilling thing is, now that we know how to discover these ultra-faint galaxies, we might be on the edge of finding a whole lot more of them. And that could express that our knowledge of the dark matter and galaxy evolution and development is right finally.
Lead scientist Masashi Chiba said, "This finding suggests hundreds of faint dwarf satellites waiting to be exposed in the circle of light of the Milky Way. How many satellites galaxies are actually there and what kind of properties and characteristics they have, will give us a significant clue to understanding how our own galaxy formed and how dark matter funded to it."
This one finding isn't enough to say for sure what's happening, but the team of scientists is now going to use the Subaru telescope to search more of these faint satellites galaxies. Either way, we are hopeful to finding out further more about what's waiting out there in the dark, revolving around our own galaxy.
The research has been printed in the Astrophysical Journal, and you can read the full research on arXiv.org.
