Messier 15

Our Sun is impressively old — four and a half billion years. That means it’s been around for roughly a third of the lifetime of the universe. But some stars in the galaxy have been around for almost the entire life of the universe. And many of them reside in a star cluster in Pegasus known as Messier 15. It’s one of the oldest clusters in the entire Milky Way — and one of the most tightly packed.
M15 probably was born about 13 billion years ago — roughly a billion years after the Big Bang. Any big, massive stars it contained have long since expired. About all that’s left are stars that are smaller and fainter than the Sun — about half a million of them. The main exceptions are a few stars that have puffed up and gotten brighter at the ends of their long lives.
The cluster spans about 175 light-years. But half of its stars are found in the central 20 light-years. That makes it one of the most densely packed clusters in the galaxy. And it means that if there are any planets in M15’s hear