May 03 – Discovery of Messier 3 (1764)

Messier 3, a globular cluster in the constellation Canes Venatici (the hunting dogs) was discovered by Charles Messier on May 3rd, 1764, but was not actually resolved into a collection of stars for another 20 years (by William Herschel).

Messier 3. Image credit: Hewholooks (Hunter Wilson).
Messier 3. Image credit: Hewholooks (Hunter Wilson).

As one of the brightest clusters (apparent magnitude 6.2) it is a popular target for amateur observers. Messier 3 contains about 500,000 stars, and is approximately 33,900 light years from Earth. Over 270 of those stars are variables, a much higher number than the average cluster; and of those, 133 are RR Lyrae variables: old, small-mass stars (about half the size of the Sun) which can be used to measure astronomical distances using the inverse square law.

1888  –  Main belt asteroid 277 Elvira was discovered by Auguste Charlois on May 3rd, 1888. It is approximately 27 km in diameter (not that I’m suggesting we are talking about a perfect sphere here) and is a member of the Koronis family. The origin of the name Elvira is not certain, but might have been inspired by a character in the Méditations poétiques of Alphonse de Lamartime, written in 1820.
The Koronis family comprises at least 300 members, mostly under 20 km wide, all following each other around in a similar orbit, and thought to exist as a result of some massive collision over two billion years ago.