Despite its small size, the faint and tiny galaxy found in our neighbor's back yard has big implications for our understanding of the universe.
All signs point to the fact that the Pegasus V is a satellite companion to the AndromedaGalaxy, a spiral similar to our own. The Local Group is made up of a small group of galaxies that are 2.5 million light years away from us. Even through a smallish telescope, it is possible to see a pair of dwarf elliptical galaxies near the center of Andromeda.
It is much fainter. Giuseppe Donatiello, an amateur astronomer, found it while looking at a huge survey of the northern hemisphere's sky. It looked like a very dim over density of light, so a team of scientists took to the huge telescope to get a better look.
The link to paper is amazing. The Milky Way is over one million light-years across, while the Pegasus V is only a few hundred light-years. The light is only about 26,000 times brighter than the sun. A single massive star can be more bright than that.
The age and distance of individual stars allowed the astronomer to determine their age and location.
The stars are so old that they don't have a lot of heavy elements. Heavy elements like oxygen and iron were created inside stars that exploded at the end of their lives and were incorporated into later generations of stars. By measuring the amount of elements we can see how old the stars are.
The stars we see in it are not all that old because of the different technique. It is important. The Universe was so dense when it was young that it was hard to see, but after the first stars were born, the Universe became transparent. The epoch of reionization was a huge part of the evolution of the universe.
We believe that a blast of UV light would have quenched any star formation. It's possible that stars 12.5 billion years old are a relic of that era. Astronomers want to understand that difficult time in the history of the universe.
The distance of the plane is also interesting. It is about 2.3 million light-years away from Earth. A lot of faint satellite galaxies for Andromeda have been found, some even as faint as Pegasus V, but they are all close to the center of the bigger galaxy. This is the first time this faint has been seen in a survey that wasn't looking for them.
The dwarf galaxy problem may be solved if that's true. There should be hundreds of small, faint galaxies around Andromeda, according to models, but only a few have been found. It's hard to spot the faintest ones, especially far out from Andromeda, so finding Pegasus V shows there are lots more to be found. If true, it means the models of how the early Universe is formed may be better than what we know today.
Sometimes the key to a lot of issues is just being able to find the first example of a faint blob in an image. It will have a lot of people sighing of relief if it is the example of a large but dim population of nearby galaxies.
Donatiello found another faint galaxy a few years ago.
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