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.
