An Earth year may be a meaningless measurement of time across the vast cosmic reaches of space, but we still want to say goodbye to 2015, because here on our little ball of rock, it was a pretty cool year. And one way we like to say farewell to the year is to look back at its scientific superlatives, celebrating the biggest, the fastest, the newest, or the brightest that anyone on this planet has ever seen.

So why not start with the brightest galaxy in the universe? Right now it's known as this (WISE J224607.57-O52635.0) and until astronomers at the Jet Propulsion Laboratory first reported it back in May, we didn't even know it existed.

But you might be wondering, if this is the brightest galaxy we've ever seen, how have we not seen it before? It's because all of that energy is coming to us as infrared light, which we just couldn't see all that well until NASA launched the Wide-field Infrared Survey Explorer, or WISE, back in 2009.

So why is this galaxy's enormous energy, the equivalent of three hundred trillion Suns, being emitted as heat, but not light? Because that energy is being unleashed by the galaxy's supermassive black hole. Which is surrounded by a cloud of dust. The dust absorbs visible light, which heats it up until it glows infrared.

Now this galaxy is one of a new class of galaxies discovered by WISE called Extremely Luminous Infrared Galaxies, or ELIRGs. Which, again, terrible name, but what makes ELIRGs exciting is that in order to put out the amount of energy we're seeing, those black holes must be absorbing matter at a faster rate than we even thought possible. 

Light is unleashed from the area surrounding a black hole when stars and clouds of gas are ripped apart. But we thought there was only so much matter a black hole could suck in at a time. And it turns out, we may be totally wrong.

Now our galaxy has a supermassive black hole of its own, known as Sagittarius A*, and it's small and quiet, as supermassive black holes go. Which is great. That's probably one of the reasons we exist. But this year, NASA's Chandra X-Ray Observatory caught the largest X-Ray flare ever observed coming from it. About four hundred times bigger than the black hole's usual eruptions. 

The past few years actually have been very exciting for our friendly neighborhood cosmic terror. Every year since 2012, for just a few hours, the black hole has emitted a super-eruption of X-Rays. The one observed in January of this year was the largest yet. And we don't really know why it's doing it. 

One theory is that Sagittarius A* has captured some nearby asteroids, and is slowly pulling them past the event horizon. If those asteroids were large enough, then the X-Rays unleashed as they were torn apart could account for the flares that we're seeing. 

Another possible explanation is that a nearby enormous could of gas, which astronomers call G2, has become magnetically entangled with the black hole, and the push and pull between the the two is making G2 vibrate like a plucked guitar string. Which could also unleash X-Rays. 

Ok, but maybe the biggest explosion ever at the heart of our galaxy isn't exactly how you want to wrap up 2015, I get that. So one last superlative, because rockets are awesome, and fire is awesome, and NASA-- awesome.

This year, NASA started test firing the biggest rocket booster ever built. This thing out out 3.7 million pounds of thrust, which is about the same as 14 Boeing 747s all taking off at once. Look at this thing! Like, there's so much fire! The new Space Launch System, or SLS, is being designed with the aim of sending missions into deep space. This is the rocket that's gonna carry astronauts to Mars. 

Typical shuttle rockets put out about three million pounds of thrust, so the new SLS rockets are a big step up. And the plan is to strap two of them together. The first actual flight of SLS is scheduled for 2018, to see how well this system handles going into low Earth orbit. And the first mission for a crew is planned for 2021. And Mars, hopefully by 2030. I want to like, doodle pictures of this rocket all over my trapper keeper, and cover it in hearts! That's how much I love this rocket. 

What were your favorite science stories of 2015? Let us know in the comments, and thanks for a wonderful year. Next week, we'll tell you what kind of space news you can look forward to in 2016. And in the meantime, if you want to help us keep making episodes like this, just go to patreon.com/scishow. And don't forget to go to youtube.com/scishowspace and subscribe.