Posted on Sep 20, 2021 in Astronomy, Science
Determining the age of a star can be one of the trickiest measurements an astronomer can make. Stars don’t obviate their age like humans do — with wrinkles around the eyes, grey hair, or brittle bones. Instead stars give hints at their age through things like their motion, rotation rate, chemistry, and placement in the Galaxy. Finding “extrema” on the age spectrum for stars — the oldest and youngest — is much easier than trying to find middle aged objects like our Sun. In this article, we reveal five fast facts about the youngest stars in the Galaxy.
Jackie Faherty
Fast fact #1: When We Say “Young” We Might Mean Different Things
When we say “young” it can mean a variety of things. For some, “young” might mean an object that is less than one million years old, for others “young” might mean an object that is less than one billion years old. There is not a clear boundary that Astronomers use for youth. What’s more important is to understand the process by which stars are formed. Our best model of star formation begins with a giant molecular cloud of Hydrogen that collapses and fragments into pieces. The cores of those fragments accumulate mass and are called “protostars” before passing through a pre main sequence phase and finally contracting to a stable radius where they enter the stellar main sequence and nuclear fusion can proceed. The length of each of those stages varies depending on the mass of the star. Higher mass stars pass through each stage rapidly (< 1 Myr in some cases) whereas the lowest mass stars take magnitudes longer (< 500,000 years or so).
Fast fact #2: Young Stars Are Found In Groups
As stated above, stars are formed from the collapse of a giant molecular cloud of molecular Hydrogen. Rarely do we think that stars are formed in situ without a collection of family members nearby. When we talk about young stars we are usually referring to a collection of them. There are famous areas across the sky referred to as “star forming regions”. The most famous of all is probably the Orion star forming region which can be seen with the naked eye near the three bright stars in the belt of the constellation. This massive factory of star formation at just over 1300 light years away is the closest of its kind to the solar system. Based on our best diagnostics, the association appears to be