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2019 is almost over and it has been another really good year for exploring the universe.  I mean, we took the first ever picture of a black hole, landed our first robot on the far side of the Moon, and explored our farthest yet object in the solar system, but some discoveries were even bigger than those.  I mean, maybe not more important, but like, literally bigger, brighter, and just generally more.  

This is our annual superlatives episode, so let's take a look at some of the coolest breakthroughs of 2019.  What better place to start than with the brightest object ever discovered in the early universe, not just in 2019, we're talking ever.  Scientists announced its discovery almost a year ago at the annual meeting of the American Astronomical Society and it's an object that looks 600 trillion times brighter than the Sun.  This thing has a super gnarly name, I'm not gonna say the whole thing.  I'm just gonna call it J04.  It's what astronomers call a quasar, the incredibly bright center of an ancient galaxy, and all that light is created by the supermassive black hole lurking at the galaxy's center.  Well, the black hole itself isn't emitting any light, but its powerful gravity has trapped an enormous disc of material in its orbit.

As all that gas and dust swirls around, bits smash into each other and that generates friction that heats up the disc until it's glowing white hot.  It turns out though that J04 is getting a bit of a helping hand.  This quasar is nearly 13 billion light years away so on its own, astronomers would never be able to see it, but fortunately, there's another galaxy perfectly lined up between us and J04, creating what scientists call a gravitational lens.  Gravity from this lensing galaxy is bending extra light from J04 our way, boosting its brightness by a factor of 50.  It's that magnification that gives the quasar its apparent brightness of 600 trillion suns and enables astronomers to spot it from half a universe away and that's a big deal because even though astronomers have long thought that lensed quasars should be common in the universe, this is the first one they've actually been able to find, and because looking this far away is also looking back in time because it's taken billions of years for that light to travel to us, it could provide critical details about a key phase in history: the period when the first stars and galaxies were being born.

Next, in September, astronomers announced that they'd found another object that while not quite as bright, is just as impressive.  It's about 4600 light years away and it's got another gibberish name so let's call this one J07.  This object is likely the most massive example of a neutron star we've ever seen.  A neutron star is the leftover core of a massive star that died in a supernova explosion.  

During that detonation, the core is crushed under such extreme pressure that the electrons and protons in its atoms are forced into one another, canceling out their opposite charges and leaving only neutrons behind.  The end result is a substance that's ludicrously dense, like one cubic centimeter of neutron star material would weigh a billion metric tons, but even among neutron stars, J07 is an oddball.  It clocks in at 2.14 times the mass of the Sun, which is like, really pushing the theoretical maximum on how big neutron stars can get.  

Although it's still a little unclear, physics suggests the absolute heaviest one of these things can be is around 2.17 solar masses.  Once that limit is crossed, the star should collapse directly into a black hole.  So at 2.14, J07 is right on that edge.  What's more, this star is orbited by a white dwarf.  If they were to collide, it would literally be lights out.  The extra mass would make the combined object so dense that gravity would just like, end.  Just collapse it into a black hole.  

For now, though, J07 will have to settle for being the biggest neutron star on the block, and along the way, it will help scientists learn more about how massive these things can become.

Finally, SpaceX set a new mark for landing rockets this year.  When we filmed this episode in mid-December, the company had landed 15 rockets in 2019.  That's three more than in 2018 and six more landings than any of NASA's space shuttles ever did in a single year, and it's not like they launched all brand new rockets, either.  They've been reusing them.  Like, in November, they launched and landed a single booster for a record 4th time and the rocket, called the Falcon 9 Block 5 is designed to launch at least 10 and up to 100 times before being discarded.

SpaceX also successfully caught and reflew a rocket's nose cone, called the fairing, for the first time this year, and although this is cool for the company and everything, all of these efficiencies are great for the space industry as well, because they could easily add up to tens of millions of dollars in savings on a rocket that's already the cheapest of its kind and that's what's really exciting here, because cheaper rockets could mean more missions and more exploration.

A decade ago, when NASA selected the Maven satellite to orbit Mars, it budgeted almost 500 million dollars for the spacecraft and almost 200 million dollars to launch aboard an Atlas V rocket.  Today, launching a Falcon 9 costs a third of that.  That's $100 million of extra money that we can spend on scientific instruments or entirely new missions.  It's worth remembering that SpaceX isn't the only company making reusable rockets, but thanks to work like this, the industry is moving forward, and a decade from now, maybe we'll have lots of new science to talk about as a result.

So yeah, it's been a great year for astronomy and here's hoping 2020 is even better.

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