August 10 – Discovery of M110 (1773)

They say that the date on the earliest known drawing of this . . .

Messier 110 (image: D. Geisler/NASA/ESA/STScI)

. . . says August 10th, 1773, so we have to assume that Charles Messier did indeed discover the dwarf elliptical galaxy M110 on that date.

It was also, though, discovered independently by prolific comet hunter Caroline Herschel, ten years later, and there seems to have been a reluctance to add it to the Messier catalogue, as it has only been in there since 1967 (it is the last of the 110 items on the list).

M110 has a massive neighbour. It sits alongside the Andromeda Galaxy (M31), which may account for Messier not listing it, and it isn’t even M31’s only satellite. Andromeda has a family of more than a dozen dwarf galaxies, including M32, on the opposite side, which is brighter than M110, despite being only half the size, so it might not be so strange that M110 took so long to enter the Premier League (sorry Charles – “Ligue Un“) of deep sky objects.

M110 is located about 2.6 x 106 light years away from us, and is also known as NGC 205. It measures approximately 8,500 light years across, and may be as massive as 15 X 109 solar masses, though opinions vary on this subject. Unusually for a dwarf galaxy, it contains dust clouds, evidence of “recent” star formation.

If anyone can tell me why people online are calling M110 the “Edward Young Star”, I’d be grateful, because that name isn’t in any of my astronomy books.

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