So there is an article posted on Space.com, a favorite of mine, on 12 May 2019 that talks about the origins of a star in the constellation the Big Dipper. It’s not one of the prominent stars like Mizar and Alcor, the binary star system in the handle of the Big Dipper, but it is an important star. According to the article the chemical composition of the star does not match any stars around it or any known stars in the Milky Way Galaxy. The prevailing theory is that the star itself formed in a dwarf galaxy that orbits the Milky Way and during a galactic collision between the dwarf galaxy and the Milky Way, when our home galaxy swallowed another smaller galaxy, it was left behind from a time before the collision. This is the prevailing theory because the chemical composition is similar to stars in other dwarf galaxies that are currently orbiting the Milky Way. The article also mentions the bulge in our galactic center as evidence of these past collisions. This also fits in with another article that mapped the location and age of stars in our galaxy and found that many of the stars in our galaxy are roughly the same age as our own, about 4-5 billion years old. This was interesting because there appears to be a gap in the age of the stars that were studied where these older stars were dying out and new stars weren’t forming due to a lack of hydrogen gas. As luck might have it out galaxy swallowed another, likely smaller galaxy, that hadn’t used up most of its hydrogen gas. This infusion of fuel for stars is what lead to the birth of these new younger stars.
I find these studies fascinating because it gives light to where our star comes from and how we formed. Based on these articles it is very possible that our star was among those formed by this influx of hydrogen and that had this dwarf galaxy not collided with the Milky Way we might not even exist today. This is part of the life cycle of galaxies. the forming of stars orbiting together the collapse and death of stars into blackholes and the combining of those blackholes into super-massive blackholes that we see at the center of large galaxies like our own and Andromeda. As stars form and use the hydrogen available and stars die spreading the enriched elements into the galaxy to form dust clouds from which our own planets formed they use up all the fuel available to them. Current estimates are that a star is born in our galaxy at a rate of 3 stars per year.
I wonder how long this has been going on. If it has been going on for a very long time, which is what my assumption would be, I wonder why we don’t see new stars in our night sky every year. I suppose it could be because there are just so many stars that we can observe that seeing one that is completely new would be difficult to identify. I guess that would be like trying to find newest drop of water in an ocean. Either way this is a fascinating observation of a star that didn’t form in our own galaxy. I wonder what the next galactic collision will bring to our neck of the universe.