At a distance of about 280,000 light-years, on the border of the Milky Way, a strange object caught the attention of astronomers.
This object has a glow of low intensity, even distant for super telescopes, but it surrounds us as the Moon does with the Earth.
It is a dwarf galaxy named Virgo I, which can alter everything we know about how dark matter holds objects together in galaxies.
As far as we know, galaxies such as the Milky Way are produced by a combination of dark matter, which creates dark orbits, and gas formations and stars that are affected by gravity.
So, if this theory is correct, we should have hundreds of small galaxies and satellites orbiting our galaxy. However, so far, only about 50 have been detected. The numbers do not fit, and this is the “dwarf galaxies problem”.
It means, that either the theory about how galaxies form with cold dark matter is wrong or we just cannot detect all the satellite galaxies that should and could be orbiting the Milky Way.
This finding, by the Japanese student Daisuke Homme of Tohoku University, suggests that this second option is possible, that is, with the help of the Subaru telescope, it was possible to detect Virgo I, which has an absolute magnitude of -0.8.
Absolute magnitude, is the measure of the brightness of celestial bodies and to date, it has not yet been possible to detect galaxies with a brightness lower than -8.
This 8.2m telescope has a large aperture, which allows to absorb more light than others, which allowed the discovery of this dwarf galaxy, near the constellation Virgo. Hence the name of Virgo I.
“We carefully examined the Subaru data and discovered an excessive density of stars in Virgo that show a characteristic pattern of an ancestral stellar system”, said Masashi Chiba, a professor in charge of this study.
“Surprisingly it’s one of the weakest satellite galaxies, but it’s still a galaxy.”
This is due to the fact that it extends for a ray of 124 light-years, “systematically greater than a globular group with comparable luminosity,” he added.
The study was published recently in the Astrophysical Journal and is important because we now know that it is possible to detect galaxies with extremely low brightness, which will help solve the problem of dwarf galaxies and better understand dark matter.
“This discovery implies that there are hundreds of dwarf galaxies waiting to be discovered in the orbit of the Milky Way”, said Masashi Chiba. He also added that, determining how many more dwarf galaxies exist will provide us with important data and clues for upcoming investigations of new galaxies.