In one of Douglas Adams’s Hitchhiker’s Guide to the Galaxy stories, Zaphod Beeblebrox is sentenced to the Total Perspective Vortex. This imaginary machine is the ultimate sanction in the galaxy. It destroys your mind by giving you perspective; by showing you just how insignificant you are compared to the enormity of the Universe. You can hear more about this from the little audio clip below, taken from the original BBC radio broadcasts of the second series of H2G2.
The picture used in the background to this audio is quite famous and appears elsewhere on my blog.
It was an email from Gus that put all of this whimsy in my mind. He sent me an animated GIF of the relative sizes of the Earth, the Sun and various other stars. Many of you will have seen it before because it has been around for a while, but it is still worth watching and is quite startling. (Click to watch…)
I thought I would put a few numbers to this. You will notice there are some differences between the order in the animation and my table. Several stars have maximum and minimum values as they expand and contract over time. Also data is being revised all the time so this is as accurate a list as I could manage for today.
You can go outside and see Betelgeuse and Aldebaran most evenings. Next time it is a clear winter’s evening look up into the sky and find Orion’s Belt – which is pretty easy to spot, low in the sky early evening. You can clearly see Betelgeuse glowing red in the top left corner of the Orion pattern.
Follow the belt up and to the right, and you will see another bright red star in the Taurus constellation. This is Aldebaran, an orange giant that has expanded to a vast size having used up all its hydrogen fuel but not yet become hot enough to start fusing helium (the next stage in stellar evolution). It is 68 light years away so the light entering your eyes has taken 68 years to reach us (at about 300,000,000 m/s). Betelgeuse is around 600 light years away and is coming towards the end of its life. It has run out of smaller elements to fuse and so is creating heavier and heavier elements within its core. This cannot go on indefinitely (iron is the limit) and so soon it will explode in a supernova, briefly becoming an object in the night sky as bright as the moon. Sadly ‘soon’ means ‘within the next million years’ so there is a high chance that you will not be around to witness it.
Questions…
- What are the chemical symbols for hydrogen, helium, carbon & iron?
- What is the approximate diameter of Jupiter in km?
- On average, how far away is the Sun from the Earth?
- Consider the picture used in the BBC Radio clip. Where do you think the photo may have been taken from and what is the small blue dot highlighted with a circle?
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