OK, it's time to get wibbly-wobbly and timey-wimey with spacetime, because something really awesome has been discovered that will change the way we look at things. We'll start with this:
The universe is expanding. We think. Well, we have some evidence that points to it. Maybe.
The tricky thing about astronomy is that because the universe is so dang big, we can't make observations about things beyond a certain point. And we reach that point pretty quickly. Our galaxy is HUGE compared to our planet. We are not even a speck of dust, relatively. And when we consider the fact that our galaxy, then, is a speck compared to even just our own local group of galaxies, thinking about the size of the universe is...well, almost scary. We know so little about the universe because we simply can't detect/observe/measure anything in the vast majority of it. Everything we have every known or seen takes up an infinitesimally small piece of it.
We can, however get glimpses of things that can help us, and one of those things was found recently by a international Swedish-led team of astronomers using the Hubble Space Telescope.
They discovered a distant type 1a supernova that is about 4.3 billion light years away, outside of our galaxy. A type 1a supernova is classified as such because the star that exploded was a white dwarf star, but that's not the cool thing about them. Type 1a supernovae always have the same intrinsic brightness, or the brightness it would be without any light being absorbed by dust and other space stuff. This means that scientists can measure how far the supernova is from us by measuring how bright it is. This quality is what makes type 1a supernova known as a "standard candle." We can use it as a way to measure other things, such as distances across the universe, and we've also used them as tools to measure the accelerated expansion of the universe and to infer the existence of dark energy. So these supernovae are pretty cool in their own right.
But there is something special about this new one, supernova iPTF16geu (which I will be referring to as John from now on--all those letters and numbers mean very specific things, but they don't mean them to YOU, and so I think it's easier to talk and learn about it using a more common name). Or rather, something special about its discovery.
When astronomers used the Hubble Space Telescope to take images of John, they saw that the light from the supernova was bent and magnified by what's called gravitational lensing, so that it formed four distinct images in the sky. One supernova, four images. How does this work?
Well, gravitational lensing is something that was predicted in part by classical physics but was made more clear (and now we can see, accurate) by Einstein's general theory of relativity. Gravitational lensing happens when there is a distribution of matter between a source of light and the observer of that light. When great distances and mass are involved, the gravitational effect of that matter on the light becomes visible to the observer. Kind of like how the sun draws comets and planets toward it with gravity, matter in the universe also bends light toward it (and I'm trying to simplify this as much as possible without going in to the wave-particle duality of light, etc...one could write books on the subject--and people have!). When light travels around a massive object, the light is bent. So gravity has the same type of effect on the light as a regular glass lens does. ESA (European Space Agency)/Hubble has a video to show how this works in the case of our supernova, John, whose light was lensed around a galaxy that lay between it and us on Earth:
Just like with a telescope lens, this gravitational lensing allows for Earth scientists to see things that otherwise would be too faint to see in the sky. It's a pretty cool trick that occurs naturally, which helps us see things we never would be able to see as well otherwise. How often to we get to see things happening in other galaxies?
So what about this particular case of gravitational lensing makes John so cool? Well, first of all, these cases of lensing are few and far between, it's very difficult to find them. Scientists are lucky to have found this, and now we can use the information gleaned from this supernova to learn about many other things, such as testing theories about the warping of spacetime. The four images we see of John are all within a radius of about 3000 light-years, which makes it one of the smallest extragalactic (or, out of this galaxy) gravitational lenses discovered. This means scientists can study the theories of warping spacetime on a smaller scale than ever before. Because the supernova also happens to be a 1a type, the standard candle, it also means that measurements can be made with more certainty than ever, relying on constants and known numbers rather than prior assumptions. The importance of this is that astronomers and physicists can now measure how long it took the light from each of the four images of the supernova to reach us on Earth. Then they can use the differences in the arrival times to calculate Hubble's constant (the rate of expansion of the universe) with possibly the most precision we ever have before.
This is very exciting news for astronomers. With these calculations, we'll be able to take steps towards learning new things about our universe, and take steps to answer questions we've only been able to guess at before. And, with the installation of new telescopes with the best observational capabilities we've seen yet, as well as the cooperation of scientists from countries around the world, the good news is that the best is yet to come!
For those interested, Hubblecast 70 was about gravitational lensing, and can also help shed some light on the subject for those who want a deeper look:
Melanie R. Meadors is an author of fantasy where heroes don't always carry swords and knights in shining armor often lose to nerds who study their weaknesses. A wearer of many hats, she is a blogger at The Once and Future Podcast, a professional author publicist, and a dabbling musician and artist. She studied both physics and astronomy at Northern Arizona University. You can find her at her website, melaniermeadors.com, on Facebook, and Twitter, @melaniermeadors.