This cluster is one of the largest and brightest, and is made up of around 500,000 stars. It is estimated to be 11.4 billion years old. It is centered at 32,600
light-years (10.0
kpc) away from
Earth.
[Messier 3 is quite isolated as it is 31.6
kly (9.7
kpc) above the
Galactic plane and roughly 38.8 kly (11.9 kpc) from the center of the
Milky Way. It contains 274 known
variable stars, by far the most found in any globular cluster. These include 133
RR Lyrae variables, of which about a third display the
Blazhko effect of long-period modulation. The overall abundance of elements other than hydrogen and helium, what astronomers term the
metallicity, is in the range of −1.34 to −1.50
dex. This value gives the
logarithm of the abundance relative to the
Sun; the actual proportion is 3.2–4.6% of the solar abundance. Messier 3 is the prototype for the
Oosterhoff type I cluster, which is considered "metal-rich". That is, for a globular cluster, Messier 3 has a relatively high abundance of heavier elements.
Source: Wikipedia
Comments