Once in a while I lose my mind and image something everyone else does. Actually I have an excuse. In organizing my hard drive a few months ago I noticed that somehow I'd not managed to image M3 with the 14" scope. That had to be corrected. This is the result. Seeing was better than average but not what I really want for globulars. They seem to need excellent seeing.
M3 is a globular star cluster in Canes Venatici. It is considered one of the showpiece globular star clusters. At about 34 thousand light years it is a rather distant one to be so famous. It contains a large number of variable (mostly RR Lyrae) stars. The cluster is quite blue due to the large number of blue star that it contains. It is thought that most globular clusters formed at about the same time as our galaxy, 10 billion years ago, and that its stars all formed at that time. Yet these appear to be young stars as stars of their color would live very short lives compared to the 10 billion year age of the cluster. There are several explanations of how these come to be. One is the merger of two or more stars, another is one star stripping gas from another raising its mass enough to turn it blue, still another says the outer shell of a helium burning star has been stripped away exposing the super hot blue core. Another says these are very old stars that are blue giants rather than red because of their low "metal" content. Maybe all are involved. In any case this is one of the bluest globulars.
In the full image a few distant galaxies are seen. The biggest and brightest is near the bottom center of the image. It is 2MASX J13421552+2813218 ID indicating an IR bright galaxy. It is some 740 million light years away light travel time. Only a couple others have red shift data. That shows them to be up to twice this distance.
That's quite a dense looking thing. Any chance of planets surviving in there?
Maybe. We do know there's something resembling a planet orbiting a pulsar in M4. But that's about it that I'm aware of.
Asimov wrote a classic short story "Nightfall" later a novel about what might happen to a civilization on a planet within a globular cluster which had several suns. The result was that for thousands of years the civilization grew never knowing darkness as one sun or more was always in the sky. Then for a time every few tens of thousands of years all three stars were below the horizon and their first night fell. Seeing the sky full of a million stars caused their civilization to go mad. It then regrew only to be driven mad again and again each "nightfall."
Anyway the orbits of stars in globular clusters are normally highly elliptical. They spend a lot of time way out on the outskirts then speed in to the core for a fast trip around the groups center of gravity then back out to the outskirts. All would be fine until that dive to the core. There things are so dense you'd expect any planetary system to be so tidally disrupted the planets could easily be ejected and picked up by another star or dive into their sun or some other nearby sun. Since the stars in such clusters are nearly all 10 billion years old they've made a lot of trips into the core.
Another problem is these are population II stars. They have a very low content of "metals". This means any planet would likely be a gas planet as there just isn't much heavier than helium and a trace of lithium to build a solid planet. These aren't first generation stars so they do contain some metals but likely not enough for solid earth-like planets even before the likely tidal disruption such a system would have to somehow survive.
Several decades ago a message was beamed to M13 as a publicity stunt for a SETI project. I always thought their pick of a target rather poor as a globular seemed almost certainly devoid of life.