HUBBLE EYEBALLS A STAR CITY THAT NEVER SLEEPS
Photo Credit: NASA/ESA Hubble Space Telescope. CLICK photo for full 17mb version and see below for links, info and 6 other posts I’ve made on globular clusters this year..
Some of my favorite night-sky objects to observe are globular clusters; they hang there in the eyepiece, their mass apparent even through the distances of space. Though you can’t view or capture images like this through an amateur telescope give them a look through binoculars or a telescope, maybe attempt some shots of them and I promise you will be hooked. Not only are they beautiful, they’re also mysterious and full of surprises. This particular object is no different and though Hubble gives us a fantastic shot, let’s break down what we’re looking at in finer detail.
Messier 15 (M15) was discovered by Jean-Dominique Maraldi in 1746. It was also included in Charles Messiers catalog of non-comets and it’s one of about 160 globular star clusters in our Milky Way galaxy. It lies at a distance of about 35,000 light years in the constellation of Pegasus. It’s believed that globular clusters like M15 here formed with the galaxy itself or even just before, making them extremely old. In globulars, normal star evolution takes place as stars still live their lives, die in various ways, get recycled into new stars etc.
One thing that makes them different is that they are so close to one another that they gravitationally interact which creates mass segregation or core collapse. This is a process where gravitational interactions move the more massive stars to the core of the cluster while the outskirts are populated by smaller, less massive stars (generally of course). Over time, these massive, live fast die young stars explode creating stellar mass black holes. After billions of years, those black holes evolve as well as they interact and consume each other creating intermediate mass black holes. These are black holes that are much larger than stellar mass black holes but pale in comparison to supermassive black holes that reside in the cores of galaxies. I refrain from calling them the goldilocks of black holes as I’m not sure ANY black holes are just right. For a pinch of perspective; depending where in this cluster you placed the Sun and the Alpha Centauri system (Our next closest stars) you could fit thousands of stars between the two. So you can see just how powerful these stellar interactions are. Currently inconclusive, it’s believed that Hubble has detected an intermediate mass black hole with the mass of about 2000 Suns in the core of M15.
Just to the left of the core region of M15 you see the large fuzzy blue star; Pease 1. Discovered in 1928 by Francis Gladheim Pease, it’s the first planetary nebula to be discovered in a globular cluster. Planetaries are pretty rare in globular clusters because most globulars have evolved past the stage of being able to create such objects. Sense that discovery only three other planetary nebulae have been discovered in other globulars. For astronomy purposes, Pease 1 is at an apparent magnitude of 15 so it’s very dim to observe.
M15 is also home to approximately 112 variable stars as well as 8 pulsars, 2 X-ray sources and at least one double neutron star system.
So you can see from this example that globular clusters are not only beautiful and awe striking; they hold to themselves some unique features in our galaxy…..
NAME: Messier 15, M15, NGC 7078.
WHAT IS IT?: Globular Star Cluster.
HOW FAR AWAY IS IT?: Approximately 35,000 light years away.
HOW BIG IS IT?: Approximately 200 light years across with approximately 100,000 stars. On the night sky it’s 18’ arcminutes.
HOW OLD IS IT?: Approximately 12 billion years old.
APPARENT MAGNITUDE?: Just at a naked eye visibility of 6.2.
WHERE IS IT? (General): Constellation Pegasus “The Winged Horse”.
WHERE IS IT? (Exact RA/DEC J2000): RA 21h 29m 58.3s / DEC +12° 10′ 01.2″.
ESA Hubble page for this photo:
ESA Hubble page with this photo and story:
SIMBAD M15 data:
WHERE IS M13: A great 3 dimensional atlas of our Milky Way Galaxy:
Atlas of the Universe: Globular Cluster List:
Students for the Exploration and Development of Space (SEDS) Globular Cluster List:
Here are some of my older posts in the last year regarding globular clusters: Enjoy!