There are a lot of galaxies in the universe — billions and billions of them, in fact. And many of them are in the process of collision: some collided long ago, some are merging right now, and some will slam together in the distant future. When they collide, the supermassive black holes in their cores can collide and merge too — and that's a pretty extreme event. Studying how fast these mergers take place is changing astronomers’ models of galaxy formation and evolution.
A very special live event from YorNight 2018, the University of York's celebration of research at beautiful King's Manor. We talked about exoplanets — that is, planets around other stars — and Emily shared her top three exoplanets of all time. Chris finished by strapping on a guitar and going all Chris Hadfield with The Exoplanet Song. A wonderful, enthusiastic audience of young and old (many in astro-themed fancy dress for the occasion!) packed out the theatre, asked brilliant questions and cheered along.
We've been so comfortable throwing around facts like "the Sun is 8 light seconds away" and "the nearest star is 4 light years away", it's easy to forget that measuring cosmic distances isn't as simple as pulling out a tape measure. So how *do* you measure how far it is to the moon, or the next star, or a distant galaxy? Emily gives us her top five rungs on the Cosmic Distance Ladder.
Mercury: closest planet to the Sun, a small, uninteresting lump of rock ... or, an enigma, with a strange tidally-locked orbit, a core that's way too big, and a mysterious origin story that astronomers are slowly piecing together. Which is why it's Emily's favourite planet, and why ESA and JAXA are sending the fabulously-named BepiColombo spacecraft to take a closer look.
At the centre of the Milky Way Galaxy lies a super-massive black hole. We know it's there, we can detect its effects on the galaxy and see nearby stars whipping around it at high speed. Last year, a worldwide collaboration of astronomers decided to try to take the first direct image of the black hole, merging telescopes spread across the planet into the equivalent of one giant radio dish. Did they succeed? We're still waiting on that image ...
The Kepler mission found loads of exoplanets, and now astronomers are digging deeper into the data in the search for exo*moons* around those planets. All of which sends Chris and Emily on a deep dive into the detail of definitions: what's a moon, anyway? Do we know what a planet is? Or a star? Do astronomers actually understand anything at all?!
Summer holidays are over, though Emily is still running around overseas enjoying the astronomer lifestyle. So Chris shares a story that tickled him this week, about a bunch of physicists and astronomers who showed that if quantum theory is just a cosmic magic trick played on researchers, that trick had to have been set up before the earth was even formed.
There’s a monster deep in the heart of the Milky Way Galaxy. Even though we can’t see it, we know it’s there ... because it has to be.
Over two decades, astronomers have pointed very large telescopes, including The Very Large Telescope, toward the galactic centre. They’ve been tracking the motions of a bunch of stars right at the core — ordinary stars doing something extraordinary. They’re moving fast, very very fast, in orbit around something very massive. But when astronomers look to find what’s at the centre of these stars’ orbits ... there’s nothing there.
The only real possibility is that they are orbiting a super-massive black hole.
At their fastest, some of the stars are moving at a few percent of the speed of light, which is fast enough to put Einstein’s theory of relativity to the test.
Stop me if you've heard this one before: astronomers announced in July that they'd found water on Mars.
No, seriously. I know they've said something that sounds like that before, but this is different — this is *liquid* water. Probably.
See, previously they'd found solid ice, and then found evidence for liquid water billions of years in the past, and then signs that sometimes a little bit of water runs across the surface in the Martian summer before evaporating away. But *this* time, astronomers reckon they've spotted a lake of briny water down under the surface. Which is exciting — so, could it mean life?! Hmmmm.