This Satellite Galaxy May Be The Faintest Ever Found
published during a waning crescent moon.
11/22/2016
Satellite Galaxy

An artist’s impression of Virgo I compared to other, nearby galaxies. Credit: Mitaka: 4D2U Project, NAO

In a paper published in the Astrophysical Journal, researchers announced that they had found a new satellite galaxy of the Milky Way. Named Virgo I after it’s location (near the constellation Virgo) the newly discovered galaxy may be the faintest galaxy ever seen.

Satellite galaxies are galaxies that orbit a larger galaxy, like the moon orbits the Earth. Many of these galaxies are dwarf galaxies, consisting of only a few thousand stars, instead of the 100 billion stars contained in the Milky Way.

Satellite Galaxy

The position of Virgo I in the constellation of Virgo (left). The right panel shows a density map of Virgo I’s member stars in a 0.1 deg x 0.1 deg area, based on the stars located inside the green zone in the color-magnitude diagram of Virgo I shown in Figure 4. The color range from blue -> white -> yellow -> red indicates increasing density. Credit: Tohoku University/National Astronomical Observation of Japan

As telescopes get larger and more precise, more and more of these faint galaxies can be detected. Three dwarf galaxies were located just last year. There are about 50 satellite galaxies orbiting the Milky Way, and 40 of them are dwarf galaxies. This new finding means that researchers have hope of locating many more.

“This discovery implies hundreds of faint dwarf satellites waiting to be discovered in the halo of the Milky Way,” Masashi Chiba, an author of the paper said. “How many satellites are indeed there and what properties they have, will give us an important clue to understanding how the Milky Way formed and how dark matter contributed to it.”

These satellite galaxies are thought to be remnants of the early formation of the Milky Way, but until now, researchers haven’t seen nearly as many as they expected. That’s important because one of the current theories about the formation of our galaxy involves the presence of satellites of dark matter in corresponding numbers to the numbers of satellite galaxies. Now, it might be the case that the galaxies are there, they’re just too faint for us to see.