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Why is the Hercules Dwarf Galaxy so flat?Why is the Hercules Dwarf Galaxy so flat?
First accepted refereed publication based on observations with the new Large Binocular Telescope
| Quote: | Through some of the very first scientific observations with the brand-new Large Binocular Telescope (LBT) in Arizona, an international team of astronomers has found that a recently discovered tiny companion galaxy to our Milky Way, named the Hercules Dwarf Galaxy, has truly exceptional properties: while basically all of its known peers in the realm of these tiny dwarf galaxies are rather round, this galaxy at a distance of 430,000 Light Years appears highly flattened, either the shape of a disk or of a cigar.
The stars in many large galaxies are arranged in a disk-like configuration, as in our own Milky Way. Yet in smaller galaxies like the Hercules Dwarf, which despite its name has only a 10-millionth as many stars as the Milky Way, a disk-like configuration has never been observed before. Among the millions of well-studied galaxies none has ever been observed to have a cigar-like shape.
An explanation for the galaxy’s unusual shape is that it is being disrupted by the gravitational forces of the Milky Way. This effect is definitely seen in another of the Milky Way's satellites, the Sagittarius Dwarf. Yet, this object is 10 times closer to the Milky Way’s centre than the Hercules Dwarf Galaxy, and hence more highly affected by the destructive "tidal forces" of our Galaxy. The Hercules Dwarf Galaxy can only have experienced a similar fate if its orbit would have brought it exceptionally close to the inner parts of the Milky Way. So, "The Hercules Dwarf Galaxy is either unlike any of the millions of galaxies studied so far, or circles our Galaxy on an extremely plunging orbit: an exceptional, unparalleled object at any rate", says Matthew Coleman of the Max Planck Institute for Astronomy in Germany, who headed this study. |
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