Supernova ‘echoes’ detected, leaving scientists puzzled

I don’t know about you, but personally I’d want to get as far away as possible if I was in the vicinity of a supernova – a massive cosmic explosion with the energy of millions and billions of nuclear bombs. In fact, in the short period when the supernova is taking place, the same amount of energy is emitted as the Sun produces in its entire lifetime.

Even here on Earth, supernovas millions of light years away can be seen as bright blobs in the sky. When the star Betelgeuse (about 400 light years away) explodes into a supernova, it’ll be so bright you’ll be able to read outside in the middle of the night. Amazingly, Betelgeuse is ready to explode at any moment now – it could even have happened by the time you finish reading this post.

But supernovas are now giving scientists a bit of a headache. They know that there was a supernova around the year 1600, and it should have been really obvious in the sky – around 300 times brighter than a normal supernova. But not a single record exists in any historical documents from any civilization around at the time.

We know that people cared about supernovas hundreds of years ago, because sailors relied heavily upon the stars for navigation. Back around the year 1000 Chinese scholars noted a supernova that we know today as the Crab Nebula. So why was the 1600 supernova undetected? That’s the problem.

But wait a minute, how can we be certain it happened 400 years ago? Basically, there are some dust clouds located 400 light years away from the supernova that have started to be lit up over the past few decades. If the light is only just reaching the dust clouds it must have set off from the supernova 400 years ago – giving a date of 1600.

One thought I had is whether religion played a role – back when the Chinese scholars recorded the AD 1000 supernova, Westerners made no mention of it. It is thought that this was because Christianity was so strong that they didn’t dare contradict its teachings that the heavens remain still and motionless. It’s just an idea… who knows the real reasons… I think this cosmic puzzle will be keeping scientists thinking for a long time yet.

(By the way, I’m not being anti-religious – I myself am a practicing Christian).

The oldest galaxy ever seen: Looking back in time with Hubble

It’s a well-known fact among astronomers that if you look at the Sun, you are looking back in time – fast as light is, it still takes 8 minutes to travel those 93 million miles. Likewise, when you look at the Moon, you are actually seeing it as it was 1.3 seconds ago, not as it is right now. So imagine looking at something so far away that its light took 13 billion years to reach us – that would mean we would be looking back in time 13 billion years, back to just after the dawn of time.

Well, NASA scientists using the Hubble and Spitzer Space telescopes have done just that, imaging one of the first ever galaxies to exist (see image below). Without vital pioneer galaxies like this one, our own Milky Way galaxy would not exist today.

So how is it possible to see so far back in time? It’s all down to a clever trick known as gravitational lensing. Basically, when you have a big object such as a galaxy, Einstein’s theory of relativity says that it will bend everything toward it sightly – light included.

The light from the 13 billion year old galaxy (A1689-zD1) was bent toward a second galaxy that is much closer to us, and this not only distorted the original galaxy’s light, but also made it appear much bigger.

In this image it is only possible to see the main bands of stars in the ancient galaxy. But get this: by 2013, when the James Webb Space Telescope (Hubble’s mega-successor) is launched, we will be able to resolve individual stars in this galaxy, even though it is so far away. And we will be able to see even further back in time, to galaxies even older than this one.

Hyakutake1957 has written a fascinating post with even more detail over on his blog.