M 3 and its variable stars


M 3 is a globular cluster which is in the constellations Canes Venatici (The Hunting Dogs). It is one of the largest and the brightest globular star clusters. It contains, like M 13, about half a million stars but what sets it apart is the high number of variable stars it contains. There are currently 274 and, of these, there are 170 which are of the RR Lyrae type. Variable stars of this type have burnt all their hydrogen. They are in the phase of thermonuclear fusion of helium and their outer envelope begins to pulsate. Their magnitude (brightness) varies rapidly over a period of between a few hours and two days.

I took a photo of M 3 on two different nights, on March 19 and 25, 2017. I superimposed the photos and made an animation of them, highlighting some of the variable stars with a red circle. They can be seen as flashing stars, due to their difference in brightness. You can probably spot more if you look closely.

Technical details:

Telescope: Celestron Edge HD14 and 0,7x focal reducer
Mount: Celestron CGE Pro
Camera: Canon EOS T3
Exposure: 30 x 2 minutes on March 19 and 30 x 2 minutes on March 25, 2017
Place: Backyard observatory in Sainte-Sophie, Qc