The end of the world is nigh (in 5 billion years)
By John Pospisil
It’s been accepted as conventional scientific wisdom that in about 5 billion years our Sun will start to burn out its Hydrogen fuel and in the process swell out to 200 times its current size scorching the Earth and everyone on it.
Our Sun will swell into a red giant making conditions very uncomfortable on Earth
Now scientists at the University of Warwick have now observed a white dwarf system, called SDSS1228+1040, 450 million light years from Earth that has already suffered this fate.
Located in the constellation Virgo, the star became a white dwarf around 100 million years ago, and is still fairly hot with a surface temperature around 22,000 degrees.
“It’s giving a glimpse of our future,” wrote Tom Marsh, a physicist at the University of Warwick, in an article in Science magazine.
As our Sun starts to run out of fuel it will swell into red giant eight times its current size, before contracting into a white dwarf.
“The Earth would be extremely singed – the oceans will boil dry and we’ll be left with a rather unpleasant rock,” said Professor Marsh.
“If it doesn’t manage to escape the red giant, it would go inside the envelope and be evaporated in the star itself.”
The research team led by Professor Marsh and Dr Boris Gänsicke from the University of Warwick’s Department of Physics also found an unusual gas disc orbiting the white dwarf.
The team observed double-peaked emission lines superimposed on the white dwarf’s starlight caused by iron, magnesium and calcium from material in the vicinity of the star.
This indicated that they were dealing with a disc of metal-gas orbiting close around the star (around 1.2 solar radii or roughly half a million miles). The observations also show that they were looking nearly edge-on to the ring around the white dwarf.
White dwarfs begin as a star similar to our sun (or a star up to 8 times bigger than our sun). Late in the star’s life it swells into a red giant probably destroying any inner planets at orbits such as those of Mercury and Venus and pushing out other planets and asteroids to a more distant orbit than before.
In the evolution of what is today a white dwarf, the progenitor of SDSS1228+1040 will have destroyed all planetary material out to a distance of 1000 solar radii (roughly 500 million miles), but asteroids still exist today at larger distances.
To destabilize an asteroid from an orbit that far out, it needs the gravitational force of a larger object, such as a relatively massive planetesimal, or a genuine planet.
While the presence of asteroids around white dwarf has been hypothesized before, the case of SDSS1228+1040 provides the first clear proof of the debris of a planetary disc around a white dwarf, and provides an example of what our own Solar system may look like in around 5 to 8 billion years.
Given that the human race has a lot of other problems to deal with before our Sun turns into a red giant (5 billion years is a long, long time), I don’t think this is something that we need to worry about too much. Though of course, Professor Strephen Hawking does not agree with this complacent approach.
Related:
Entry was posted
on Friday, December 22nd, 2006 at 4:53 am
under
Read more entries by John Pospisil.
Stumble It!
