How many stars are in the Universe 2019?

Lost in a Sea of Stars: Seriously, How Many Are Out There? (2019 Edition)

Ever look up at the night sky and just feel… tiny? I do. It’s easy to get lost in the sheer number of stars you can see, but that’s just scratching the surface. The real question, the one that keeps astronomers (and insomniacs like me) up at night, is: how many stars are actually out there in the universe? Back in 2019, the best guess scientists had was around 7 x 10^22. Yeah, that’s seventy billion trillion stars. Let that sink in for a minute.

Now, before you start picturing yourself counting them all (good luck with that!), there are a few things we need to clarify.

First, we’re talking about the observable universe. Think of it like this: the universe is vast, maybe even infinite, but we can only see a certain chunk of it – the part where light has had enough time to reach us since the Big Bang. That cosmic horizon is about 46.5 billion light-years away, making the observable universe roughly 93 billion light-years across. Anything beyond that? It’s a mystery for another day (and probably requiring some serious advancements in telescopes!).

So, how do you even begin to estimate a number that mind-boggling? Well, astronomers use galaxies as their stepping stones. Stars tend to hang out together in these massive groups, so if you can figure out how many galaxies there are and how many stars are in each galaxy, you’re on your way.

In 2016, the Hubble Space Telescope gave us a real shocker: it turns out there are probably around 2 trillion galaxies in the observable universe! That’s way more than the older estimates of 100 to 200 billion. Of course, many of these new galaxies are smaller and fainter than our own Milky Way, which throws another wrench in the works.

Speaking of the Milky Way, we think it has somewhere between 100 and 400 billion stars. That’s a huge range, I know! And here’s the kicker: the Milky Way is actually a pretty big galaxy. Some dwarf galaxies might only have a few million stars, while giant elliptical galaxies can boast trillions. Finding an “average” number of stars per galaxy is like trying to find an average house price across the entire planet – it’s complicated!

Early estimates often used that 100 billion stars per galaxy figure, but with all those newly discovered dwarf galaxies, the real average is probably lower. By carefully measuring the brightness and number of galaxies we can see, astronomers arrived at that 2019 estimate of 7 x 10^22 stars.

But let’s be real, this is still a rough estimate. There are tons of things that make this calculation super tricky:

• Hidden Galaxies: Some galaxies are just too far away or too faint for us to see with current technology. We’re always building better telescopes, though, so who knows what we’ll find next!
• Cosmic Dust Bunnies: Dust clouds inside galaxies can block the light from stars, hiding them from view. Thankfully, telescopes that can see infrared light can pierce through some of that dust.
• The Mystery of Dark Matter: A big chunk of every galaxy is made of dark matter, which doesn’t emit light. This makes it hard to weigh a galaxy and figure out how many stars it should have.
• What Even Is a Star?: Even defining what counts as a “star” can be tricky. What about brown dwarfs – those failed stars that are bigger than planets but never quite ignited? Do they count?

So, yeah, figuring out the number of stars in the universe is a messy business. But even with all the uncertainties, that 70 billion trillion estimate gives you a sense of just how mind-blowingly huge the cosmos really is. And honestly, that’s pretty awesome. As we keep exploring, I’m sure we’ll keep refining that number, and maybe even stumble upon some even bigger surprises along the way. The universe is full of them, after all!