How many stars are there in our home galaxy?
How many stars: There are undeniably an unfathomable number of stars in the milky way. But how many precisely?
On a beautiful and clear night, a human being can only count up to three thousand stars in the night sky, provided one is located in a non light-polluted area under moonless and pristine conditions. However this only accounts for a handful in the scale of the whole galaxy, which spans over 100,000 light years in diameter. It really is like a needle in a haystack! Indeed the vast majority of the stars that strew it are not visible to us because most are too small, faint or far away. Some can also be hidden behind thick clouds of dust like nebulae.
Actually we now know that most of the stars that constitute our home galaxy are crammed and smuggled inside the milky trail that crosses the firmament. Nebulae are absolutely beautiful to look at, as they are the remains of previously exploded stars. However they also pose a major hurdle in the way of astronomers who attempt to map our galaxy. Fortunately for us, scientists have found a way to counter this ordeal. Instead of utilizing imagers or optical gear that see in the visible spectrum of electromagnetic radiations only, they have developed other able to use other frequencies like UVs, X-rays and infrareds. Infrared light, which is emitted by stars as they heat up- can penetrate through thick clouds of dust and gas, unlike visible light. By switching a telescope into ‘infrared vision’, we are now able to reveal what was before invisible, and it was unfathomably bigger than we had anticipated!
Between 100 and 400 billion times the mass of our Sun
To individually count the stars of the milky way is thus impossible, even if we can penetrate through dense nebulae. It is pretty much the same for all the galaxies that we have and are still discovering at the present time. Instead, astronomers use the mass of the whole galaxy, which can easily and quite accurately be estimated. However it is not as simple as it sounds since a galaxy doesn’t only consists of stars.
First scientists need to subtract the dark matter that is ordinarily scattered throughout the milky way. It comprises dark nebulae, black holes (which are absolutely massive), the brown dwarves, planets, planetoids, asteroids, comets, etc… and exotic black matter, which nature yet remains unraveled.
Thus after all these complicated calculations have been done, we estimate that our home galaxy contains a minimum of 100 billion of solar masses and a maximum of 400 billions. Nonetheless all the stars are not completely identical to our own Sun (a yellow dwarf). If we compare the galaxy to a huge forest, there exists a large diversity of species such as trees, shrubs and bushes of all sizes and ages. In the milky way, the most numerous stars are brown and red dwarves. The bigger stars like the red giant Antares are much rarer.
This huge number is still very hard to imagine at the scale of our planet, because that is just for one galaxy. We know there are billions and billions of galaxies in our universe. Consequently that will give you some time to contemplate the vastness of it during your next astro-sortie!
- Make sure to check Adriens page for more stunning pictures and video footage
- NASA top 5 images of deep space