“The laws in this city are clearly racist. All laws are racist. The law of gravity is racist.” –Marion Barry
The law of gravity, contrary to what Marion Barry says, is — perhaps — the most indiscriminate of all the laws of nature.
What do I mean? Well, you get a large collection of matter and energy together, like in a galaxy, and what does it do? It pulls — with the entirety of the irresistible force of gravity — on everything. Give the most massive collections of matter enough time, and they’ll pull in everything around them for tens of millions of light years.
And when you do, you’ll end up with huge, gigantic clusters and superclusters of galaxies, containing hundreds, thousands, or even tens of thousands of giant, Milky Way-sized (or larger) galaxies.
This teaches us something wonderful, crazy, and fascinating about the Universe.
But you needed to collect all of them to make the larger, more powerful, and all-around more awesome toy. In 1986, owning all the pieces of Devastator of Voltron made you a total badass.
The Universe is a lot like this. In the early stages, the Universe was filled with an incredibly large number of small galaxies and clusters, where a typical one contained maybe only a few million times the mass of our Sun. In other words, the vast majority of these baby galaxies were less than 0.1% the mass of our Milky Way!
But our Universe today has a huge population of heavyweights. In other words, where have the lions and dump trucks gone? Why are there so few left? And why are there so many Voltrons and Devastators out there?
The simple answer is mergers. Over time, the gravitational forces between neighboring galaxies pulls them towards each other, and galaxies merge to form larger, more massive galaxies. This is in our future, by the way, as in a few billion years we will merge with the other large galaxy in our part of the Universe: Andromeda.
Remember, the Universe is “only” 13.7 billion years old, or about three times as old as the Earth is. We can look at objects that are millions or billions of light years away, and see them not as they are today, but as they were millions or billions of years ago! This is because it takes the light millions or billions of years to reach us!
It takes an amazing piece of technology to image something so faint and far away, but the Hubble Space Telescope is up to the challenge! Take a look at this masterpiece.
There are thousands of galaxies in this image. The closest ones to us have taken only a few hundred million years to send their light to us, but the farthest? In the upper left corner of the image, there’s a galaxy so distant that it merely appears as a dot.
But, after 13.1 billion years, the light has finally reached us! The 600-million-year-old baby galaxy is so distant that the Universe isn’t even 100% transparent to light yet, so it’s really at the limit of what we can see!
But this is what we get as our reward: a glimpse of the most distant galaxy ever detected!
Is it real, you may wonder? Or is this an artifact that will turn out to be some sort of mistake? To find out, we need a follow up observation.
Well, after 16 hours of observing at the Very Large Telescope in Chile, it’s been confirmed! Now, of course we’re only seeing the very brightest objects this far away and this old, but this is the frontier of science right now.
We’re finding the first infant galaxies, and this one likely no longer exists, having probably merged many times since the light that reaches us now was first emitted. For those of you who like redshifts, this record-breaker is at a redshift of 8.6, which beats the old record, held by IOK-1, of only 6.96. Don’t be surprised if it turns out to be atypical: relatively large, active and forming stars. Why? Because that’s what the brightest galaxies do, and the extraordinarily bright ones at this distance are going to be the only ones we can see.
So enjoy this record-setting day for astronomy, where we’re discovering the ancient building blocks of the modern behemoths of the Universe!