The Milky Way galaxy does not exist in isolation in a small corner of the universe.
Small and faint, dwarf galaxies are composed of around a thousand stars, many of which move in long, graceful orbits around our universe. About 60 What I’ve discovered so far.
Astronomers recently identified two more smaller companion stars, but this news doesn’t solve the problem as much as you might think: it looks like there are just too many companions.
That’s because the two new moons, named Virgo III and Sextans II, have been discovered in a region of space that’s already packed with more dwarf galaxies than models of dark matter predict.
“Including the four known satellites, there are a total of nine satellites in the HSC-SSP’s observation range.” Write about the team led by Daisuke Homma National Astronomical Observatory.
“This rate of ultrafaint dwarf discovery is much higher than predicted by recent models of the expected number of satellites in the Milky Way within the framework of the cold dark matter model, suggesting that we are facing a ‘too many satellites’ problem.”
Dark matter is an invisible, unknown substance in the universe that exerts an extra gravitational force that normal matter does not. Galaxies, including the Milky Way, are filled with and surrounded by this mysterious substance, which causes the galaxy to rotate faster and exert a stronger gravitational force that attracts, holds, and eventually engulfs its satellite galaxies.
Based on models of the Milky Way’s dark matter, astronomers predict that the galaxy must have many more dwarf moons than we’ve discovered so far. But that doesn’t mean they don’t exist, and scientists are using all the tools in the universe to find them in the darkness.
Dark matter-based models also give us fairly detailed predictions of how many satellite galaxies we can find in a particular location, but Virgo III and Sextant II pose a problem in this regard.
Homma and his colleagues looked at data from the Subaru Telescope’s High-Speed Camera (HSC) Strategic Program (SSP) to study a part of the universe looking for satellite galaxies of the Milky Way. According to dark matter models, that part of the sky should be home to about four dwarf satellites.
These two new galaxies bring the total number of galaxies in the region to 9. Even before these galaxies were discovered, the number of moons was already inexplicably high.
Moving things around – for example, excluding the classical dwarf galaxy Sextant Galaxy, or employing a different model to predict how many moons we should see – does not solve the problem.
The best current models predict that there are about 220 dwarf galaxies orbiting the Milky Way. If we extrapolate the distribution found in the HSC-SSP footprint to the rest of the space surrounding our galaxy, the total is actually closer to 500.
However, it’s possible that the HSC-SSP footprint contains a higher concentration of moons than the average part of the universe, and the only way to determine if this is the case is to continue observing other parts of the sky and count the dwarf galaxies we find there.
“The next step is to use more powerful telescopes that capture a wider area of the sky.” Astronomer Masashi Chiba says: Tohoku University Vera C. Rubin Observatory The Chilean moon will be used to achieve this goal, and we hope to discover many new moon galaxies.”
This study Publications of the Astronomical Society of Japan.