Concepts Explained: Astronomy

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/ əˈstrɒnəmi / [noun]
__ the branch of science which deals with celestial objects, space, and the physical universe as a whole.

Astronomy (from Greek: αστρονομία) is a natural science that studies celestial objects and phenomena. It applies mathematics, physics, and chemistry, in an effort to explain the origin of those objects and phenomena and their evolution. Objects of interest include planets, moons, stars, galaxies, and comets; while the phenomena include supernovae explosions, gamma ray bursts, and cosmic microwave background radiation.

Have you ever wondered where the Universe came from? Or more importantly, where it is going to? This set of short animations examines different scientific concepts from the big bang to relativity, from black holes to dark matter. A transcript is below each of the videos.

Sections

  1. The Big Bang  Just how big was the Big Bang? Discover how scientists have calculated the exact volume of the noise created at the birth of the Universe.
  2. Supernovae  What happens when a star explodes? Learn how all the elements in the Universe were formed, and where exactly your favourite silver necklace comes from.
  3. Exoplanets  We cannot see exoplanets, but we know they’re there. This episode explores how scientists have studied distant stars to learn more about the invisible planets that orbit them.
  4. A Day on Mercury  No-one on Mercury could claim there’s not enough hours in the day. Find out how you’d pass the time on a planet where a single day lasts two years.
  5. The Rotating Moon  The Moon is like a loyal servant to a Queen, and never turns its back on the Earth. Discover how the Moon’s orbit means we always see it is best side.
  6. Life on Mars  Discover how asteroids and microbes flying through space could hold the secret to life on Earth and Mars.
  7. Event Horizons  Just what is the point of no return? German physicist, Karl Schwarzchild calculated the event horizon of black holes. And it can tell us more about the eventual fate of all the galaxies.
  8. Dark Matter  Fritz Zwicky was a Swiss astronomer who discovered Dark Matter in the Universe. But what’s the matter with dark matter?
  9. Special Relativity  Who had more fun in life, Albert Einstein or Richard Feynman? Whichever one of them was travelling faster.
  10. Large Hadron Collider  Some thought it would create another Universe, while others thought it would suck us all into a black hole. But the Large Hadron Collider is not as dangerous as we thought.
  11. Dark Energy  Who’d have thought Albert Einstein could make a mistake? Dark Energy explores how Einstein was right all along about the expanding Universe. We never should have doubted him.
  12. Black Holes  Is it possible to make your own black hole?
  13. Taking a Galactic Census  How do you take a census in space? Find out how it is possible to produce a 3D map of the galaxy, with a little help from the new Gaia Spacecraft and a whole heap of measuring.
  14. Gaia and the Killer Asteroids  How do you avoid killer asteroids? With the unpredictable threat of killer asteroids attacking the Earth, it is Gaia to rescue!

^ 1. The Big Bang


Source: Open University (2012). 60 Second Adventures in Astronomy.  Duration: 01:15

Just how big was the Big Bang? The idea that the universe is expanding as the result of a single explosion wasn’t always universally popular. In fact, the term ‘Big Bang’ was coined in 1949 by astronomer Fred Hoyle as a way of sarcastically dismissing it. But thanks to Edwin Hubble we now know our observable universe is expanding, and extrapolating backwards we can tell that 13.7 billion years ago it was all compacted into one super-dense ball. And this ‘singularity’ expanded and cooled to become everything in the universe that we see around us. So though the Big Bang involved everything in existence – its beginnings were really quite small. And after measuring the background radiation in the universe, astronomers have worked out that the Big Bang was only around 120 decibels – about the volume of an average rock concert. So, while the Big Bang still has a lot to teach us about the universe, we do know, at least to start with, it wasn’t particularly big. And it wasn’t much of a bang either.

^ 2. Supernovae


Source: Open University (2012). 60 Second Adventures in Astronomy.  Duration: 01:15

One of the most mind-blowing events in the universe is the explosion of a star. In 1054 CE Chinese astronomers spotted one so bright they could see it in daylight. Today you can still see a cloud of gas and dust from the same explosion – And because a drawing of it looked like a crab, it was called the Crab Nebula. Much like a supercharged lighthouse, the centre of the star, now a neutron star, spins thirty times a second and sends out a beam of radiation. Several thousand of these have been discovered, each about twenty kilometres across, but with a mass similar to the Sun. If we could imagine a cupful of neutron star matter it would weigh a hundred billion tonnes. But supernovae are more than just impressive bangs. Life forming elements like carbon and oxygen were created inside stars. And the explosion of the star creates even more elements like gold and platinum, to create generations of stars and planets. And a variety of attractive ornaments.

^ 3. Exoplanets


Source: Open University (2012). 60 Second Adventures in Astronomy.  Duration: 01:15

Like fussy holiday makers looking for a home from home, astronomers are fascinated by finding planets similar to Earth beyond our solar system. But planets outside our solar system, known as ‘Exoplanets’ are difficult to spot because they get lost in the glare from the star they orbit. Like a mosquito flying around a streetlamp. So how do you see something that’s effectively invisible? Observing the changing appearance of some stars, astronomers found that an exoplanet could be detected by measuring the effect of its gravitational pull on the star it orbits. Some can also be detected if they pass in front of their star, causing its light to dim slightly. Like a wink. You can even work out the planet’s mass and size from the amount of the stars wobble and the depth of its wink. Which gives us a pretty good idea of what it is made of. Some exoplanets may even contain water because they orbit their stars in the Goldilocks Zone. Any further away they’d be too cold, any closer, too hot. And although hundreds of exoplanets have been discovered, astronomers haven’t yet found one that’s just like the Earth. Who needs a second home anyway?

^ 4. A Day on Mercury


Source: Open University (2012). 60 Second Adventures in Astronomy.  Duration: 01:15

No two planets act exactly the same. Whether it is Jupiter spinning in only ten hours, Venus spinning backwards or Uranus tilting to one side. But Mercury is particularly strange. It takes nearly fifty-nine Earth days to rotate. Which might make for a pretty long day, but at least you’d have time to get things done. But while the days are long on Mercury, the years are relatively short. It travels round the Sun in just eighty-eight Earth days. Now, until 1965 we thought Mercury span exactly once per orbit – which would mean that one side of it was always facing the Sun. If it span twice every orbit, its day would be the same length as its year, which would at least make calendars nice and simple. But it actually spins three times for every two orbits. Which means each Mercury day lasts for two Mercury years. So, while you might get a bit bored waiting for the evening, at least you’d be able to celebrate your birthday twice a day. Even if you had to share it with everyone else.

^ 5. The Rotating Moon


Source: Open University (2012). 60 Second Adventures in Astronomy.  Duration: 01:15

Look at the Moon from Earth, it always looks similar. Different parts are illuminated at different times – but oddly we always see the same features. The Moon never turns its back on us, much like the rules of etiquette when you visit the Queen. So, does this mean the Moon does not rotate? Well no. Because then, as it orbited us we would see first its front, then its left side and then its rear. What actually happens is that the Moon rotates exactly once every orbit, which takes a bit less than a month – so, though you’d see it spinning from an outside perspective, from the Earth we always see the same side. In fact, we didn’t get a proper view of the far side of the Moon until 1959, thanks to a Soviet space probe. The Moon used to spin a lot faster. But over millions of years, the gravitational pull, or tidal force, from the Earth has slowed the Moon down. The same thing has happened to most moons of large planets. But it does not work both ways, because while the Moon is spinning once every orbit, the Earth is rotating about thirty times faster. So from a vantage point on the Moon, you’d get to see us from all sides… if you stuck around long enough.

^ 6. Life on Mars


Source: Open University (2012). 60 Second Adventures in Astronomy.  Duration: 01:15

For centuries writers, astronomers and David Bowie have been asking ‘Is there life on Mars?’ The idea that we are alone in the universe seems incredible… so people have dreamed up all types of alien. We know there aren’t any ‘bug-eyed monsters’ on Mars. But it does have a lot of places where microbes could live. This may inspire a low budget movie, but crucially, if life on Mars started independently from life on Earth, then it is much more likely that it could also start in other places in the Universe. (But) over billions of years spent with asteroids crashing into them, Earth and Mars have exchanged more pieces of rock than geologists at Christmas. And those rocks could carry microbes from one to the other. Meaning any life on Mars could have come from Earth in the first place. So it would tell us nothing about the likelihood of life originating on the planets of other stars. Though it would pose another question; did life on Mars come from Earth, or did life on Earth originally come from Mars? In which case, martians could be a lot closer to home than we thought.

^ 7. Event Horizons


Source: Open University (2012). 60 Second Adventures in Astronomy.  Duration: 01:15

Just what is ‘the point of no return’? Karl Schwarzschild was a German physicist who not only served in the First World War, but at the same time managed to work out the exact distance from the centre of a black hole – to the point where gravity becomes so strong that even light cannot escape. This is the point of no return, also known as the Event Horizon – because, much like the normal horizon, beyond it nothing can be seen. But it is not just black holes that have event horizons. The expansion of the Universe is accelerating – meaning the space between distant galaxies and us is expanding so quickly that their light cannot travel fast enough, ever to reach us. So the whole universe is a bit like an inside out black hole – and as it carries on expanding, fewer and fewer galaxies will be observable to us as they pass to the other side of the event horizon. And when they’re lost from view, that’s it. They’re not coming back. That’s the point of the point of no return. And the whole Universe will eventually just…

^ 8. Dark Matter


Source: Open University (2012). 60 Second Adventures in Astronomy.  Duration: 01:15

What’s the matter with Dark Matter? Fritz Zwicky was a Swiss astronomer who could probably get you 81 points on a triple word score in Scrabble. In the 1930s he noticed that galaxies within clusters were zooming around far quicker than their mass would logically dictate. So he figured that there must be some extra mass in there… some sort of dark, invisible matter, slurping round the universe. He imaginatively called this dark matter ‘Dark Matter.’ But the problem is trying to prove it. Because unlike other ‘dark’ things, you can see right through this stuff. And this gave Zwicky another idea – according to Einstein’s theory of General Relativity – the more mass something has the more it magnifies and distorts objects that you can see through it. So by studying the distortion of distant galaxies, we can calculate that there must be some extra mass between us and them. But because we cannot see it, touch it or weigh it – it is not surprising that we cannot figure outexactly what it is. And that’s what the matter with dark matter is – it makes up most of the mass in the Universe – but when it comes to knowing the details, we’re still in the dark.

^ 9. Special Relativity


Source: Open University (2012). 60 Second Adventures in Astronomy.  Duration: 01:15

Does time fly when you’re having fun? In 1905 Albert Einstein introduced the theory of Special Relativity, which said that – if the speed of light is constant – then people must experience time differently. Which may sound impossible – but Richard Feynman later showed that you can prove it with just lights and mirrors. If you set up two mirrors, one of which had a flashbulb and a detector on it, you could build a clock which ticked every time the flash was reflected back to its original source. It would keep time perfectly – though would make a slightly annoying alarm clock. But if you make this ‘clock’ go past you very quickly – the light has further to travel. And since light always travels at the same speed – the moving clock runs slower than when it was at rest. So, though time might not fly when you’re having fun – a moving clock does tick more slowly than the observer’s stationary clock. Which may have changed the way we see the universe – but does not always make for a good excuse.

^ 10. Large Hadron Collider


Source: Open University (2012). 60 Second Adventures in Astronomy.  Duration: 01:15

The Large Hadron Collider is a high-energy particle accelerator which is being used to help us understand the origins of the Universe. Some people complained that by trying to reacreate the Big Bang the collider could accidently create another Universe – which could make things a bit cramped. Or worse still create a black hole into which we all disappear. But luckily the collider isn’t trying to recreate the Big Bang itself – just what happened shortly afterwards – by staging collisions that are continually produced all over the Universe quite naturally. Some of these collisions have amazingly confirmed the presence of the mysterious Higgs Boson particle. So is it safe? Well if you stuck your head in it, the needle-thin beam would easily kill any living tissue it passed through. And in 1978 Russian scientist Anatoli Bugorski accidentally got shot through the head by a proton beam and even though he luckily survived – it wasn’t good for him. So it is probably best not to stick your head into a Hadron collider of any size – because at the very least you’d have to live with the fact that you’ll forever be known as ‘that guy who stuck his head in the Large Hadron Collider’.

^ 11. Dark Energy


Source: Open University (2012). 60 Second Adventures in Astronomy.  Duration: 01:15

Why is the Universe expanding? Albert Einstein was absolutely certain the universe was stable but he couldn’t work out why his snazzy new relativity equations suggested that it was contracting. So, Einstein figured space must have an in-built tendency to fling itself apart – which would balance out the pull from gravity. This flingy-out-ness got called the ‘Cosmological Constant’ – and meant the Universe could be kept static. Which was great – until it was proved by Edwin Hubble that the Universe is in fact expanding! – and that cosmological constant became what Einstein described as “the biggest blunder of my career”. Then, in 1998, scientists discovered that the Universe was not only expanding, but that expansion was actually getting faster. So either space does have a tendency to fling itself apart, or there must be some other hidden weird stuff in the Universe causing it. Referred to as ‘Dark Energy’. Astronomers are looking for it right now by measuring tiny kinks in space. And in its simplest form, this Dark Energy is pretty much a Cosmological Constant – so Einstein was right all along. Apart from the time he said he’d blundered.

^ 12. Black Holes


Source: Open University (2012). 60 Second Adventures in Astronomy.  Duration: 01:15

A black hole occurs when something has so much mass in such a small space, that nothing can escape its gravitational pull – not even light. In 1931 Subrahmanyan Chandrasekhar calculated that, if a star is big enough, when its fuel runs out there is nothing to stop gravity from making it is core collapse to create a black hole. Unfortunately for Chandrasekhar, his contemporaries like Sir Arthur Eddington, just didn’t believe him. But it turns out he was right and in 1983, he eventually won a Nobel Prize for it. So if a star is big enough to begin with when it collapses it becomes so dense that its gravitational pull won’t let objects or light escape. In fact you would make a black hole if you crushed any object until it was small and dense enough. But you don’t always have to crush something to make a Black Hole – the bigger one is, the less dense it needs to be. So you could make one out of tap water – though the required amount will fill the space between the Sun and Jupiter… and sadly there’s not enough water in the galaxy for that. So for you DIY enthusiasts you’ll probably have to order it in specially.

^ 13. Galactic Census


Source: Open University (2012). 60 Second Adventures in Astronomy.  Duration: 01:15

How do you take a census in space? Keeping track of millions stars is quite a tricky job – especially as they are constantly moving. Luckily the new Gaia spacecraft is coming to the rescue – from a position of about one and a half million kilometers from the earth – ready to do a whole lot of measuring. With its two optical telescopes, Gaia will be able to map over a billion stars by measuring minute changes of position against the background of other stars – this is known as parallax. And, as well as measuring how old and bright they are – by measuring their Doppler shifts – it can tell us whether those stars are moving towards us or away from us. And if that’s not impressive enough – by measuring the bending of starlight by the sun’s gravitational field – it will be able to test Einstein’s theory of General Relativity. In the end Gaia will deliver us a map of the Galaxy. And not just any map – it will be in 3D, show us how everything is moving, and help us get a better understanding of how the whole thing began and where it is heading.So, taking a census in space will be a much more realistic proposition.

^ 14. Gaia and The Killer Asteroids


Source: Open University (2012). 60 Second Adventures in Astronomy.  Duration: 01:15

If Hollywood has taught us one thing it is that an asteroid crashing into the Earth is not exactly something to look forward to. The asteroids most likely to attack us are the Aten and Apollo asteroids – the ones with an orbit closest to our own. Talk about annoying neighbours. And unfortunately these asteroids are pretty difficult to keep track of – because, to see them from the Earth you’d have to look directly towards the Sun. Fortunately the Gaia spacecraft is going to be positioned 1.5 million kilometres beyond the Earth at a point where gravity will keep it in a fixed orbit. This is the second Lagrangian point – or L2 to its friends. From this vantage point Gaia can look back towards the Sun to spot any potentially dangerous asteroids that we may otherwise have missed. Like a lookout in the crows nest – or Kevin Costner in The Bodyguard. But while it is obviously good to know if a killer asteroid is, indeed, on the way – the next challenge will be what we’re going to do about it if Gaia spots one.

 

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