by Matthew Cobb
I know that many of you will be just chilling (or, in my case, ‘just’ marking exams), but I thought you might appreciate these two bits of mind-boggling numbers. The video is from The Guardian and explains very simply the kind of distances astronomers have to deal with, and how you can try to get your head round it (Warning: the presenter, Pete Edwards of Durham University, says you can’t do it.)
The information in the final third of the video – dealing with the number of galaxies in the amazing Hubble Deep Field image – is apparently out of date. Edwards says (5:00) that there are about 10,000,000,000,000,000,000,000 (10 to the 19th power – I think I have that right; I counted on my fingers) stars in the visible universe. Which is a lot.
But according to a Daily Galaxy link from the excellent Milky Way Scientists that popped up in my Facebook this morning, data from the Very Large Telescope (amazing imaginations, these astronomers) in Chile suggest that the number could be bigger. MUCH bigger.
For a start, the initial estimate given by the Daily Galaxy is 3,000 times bigger than Edwards:
Here’s how astronomers breakout the visible universe within 14 billion light years:
Superclusters in the visible universe = 10 million
Galaxy groups in the visible universe = 25 billion
Large galaxies in the visible universe = 350 billion
Dwarf galaxies in the visible universe = 7 trillion
Stars in the visible universe = 30 billion trillion (3×10²²)
A new study suggests that 90% of the most distant (and therefore oldest) galaxies in the universe could be unseen, hidden by clouds of dust. That would mean that – assuming the same number of stars in each galaxy, and that older galaxies don’t deviate from this rule – that the number of stars in the visible universe would be 270 billion trillion or 2.7 x 10 to the power of 24).
I’ve probably slipped up somewhere in the maths. But my head hurts (Edwards was right – you can’t do it) and I have to go back to marking essays about the similarities and differences shown by the three classes of the Chelicerata. That at least I can understand.