h2g2 The Hitchhiker's Guide to the Galaxy: Earth Edition

does this story

http://www.bbc.co.uk/news/science-environment-13416431

change the calculations of the amount of matter in the universe???

Not really, because they already knew how much matter there is in the galaxies, and not by counting the stars. The figure for the mass of a galaxy is got from watching how it interacts with other galaxies.

Counting the stars and multiplying by the average mass per star gave a much smaller figure for the whole galaxy than the figure got by observing the galaxy's behaviour. There was always a discrepancy there with no explanation. They invented a hypothetical "dark matter" to try and explain the difference.

Perhaps these isolated planets are part of the dark matter.

but if these planets are part of the dark matter, but are normal matter, then the amount of real dark matter must be a bit less than originally calculated??

Yes. But "real dark matter" is a bit of a contradiction, because dark matter is something that they don't know exists. It is just a missing bit in an equation.

so if we have all these rouge planets in space, why can't there be enormous asteroid fields in interstella space accounting for more of this unacounted for matter

I think current thinking is that interstellar gas doesn't form into small lumps, it forms into big lumps, which become stars, so these "rogue" planets must have formed in solar systems and been thrown out into interstellar space by close encounters of the gravitational kind. A small number of people think they might have formed themselves in situ.

Would it necessarily have to be a gravitational interaction with another star?

Could it, for example be due to a Neptune orbit planet having 'wandered off' after the main star went through the red giant phase and, having lost so much of it's mass, no longer having the gravitational pull to keep it? Or would that affect the outer planets to the extent that they'd have most (or all) of their gas blown away?

Why do the BBC *never* link to the real paper and just to the website of the journal it's published in.

Wouldn't a great science fiction story involve life on a planet without a star. They could get all their fuel from nuclear reaction or something..

*plots*

Anyway clicking around on the nature website has led me to lots of interesting information, they've got high quality textbooks as free e books...

>so if we have all these rouge planets in space<

Is that to go with all the bleu, and blanche planets in the galaxy?

<>

http://www.youtube.com/watch?v=ezzsTnZX5Jg

http://www.youtube.com/watch?v=vaDLf2wJ9Jg

http://en.wikipedia.org/wiki/A_Pail_of_Air

What a bleak storyline. Very good though.