-
- When the end of the world comes, we'll know what to blame.
Scientists have found compelling evidence that the Sun has a baby brother,
a dark star whose eccentric orbit is responsible for periodically showering
the Earth with comets and meteorites.
-
- The dark star - named Nemesis by astronomers - is thought
to be a "brown dwarf" that spins round the Sun in an orbit so
large it is measured in light years, the distance light travels in a year,
equivalent to about 6,000 billion miles.
-
- The research suggests that, every 26m years, the star's
eccentric orbit brings it within one light year of the solar system. There
it causes havoc in the Oort Cloud, a huge region surrounding the solar
system that contains billions of bits of cosmic rubble left over from the
formation of planets.
-
- Of the millions of rocks it throws out of orbit at each
visit, some hurtle Earthwards - and have several times nearly wiped out
life on Earth.
-
-
- Astronomers have long wondered if the Sun has a smaller
partner. Recently, two independent groups of researchers have found evidence
of one.
-
- One group, led by John Matese, professor of physics at
the University of Louisiana at Lafayette, confirms the notion that it is
most likely to be a brown dwarf, a star that never accumulated enough mass
to ignite and which has simply sat in space smouldering for billions of
years.
-
- Matese studied 82 comets from the Oort Cloud and found
common elements in the shape of their orbits that could only be explained
if they had been influenced by the gravitational pull of an object several
times the size of Jupiter and existing about 25,000 times farther from
the Sun than the Earth.
-
- Matese said: "A companion to the Sun orbiting at
these distances would have little effect on the planets. But it would play
a big role in the way comets 'made their way' from their birth places in
the planetary disc out to the Oort Cloud and on how they can return to
the inner solar system."
-
- Further research was published last week by Richard Muller,
professor of physics at the University of California, Berkeley, following
analyses of moon rock samples brought back to Earth by Apollo 14.
-
- The absence of a protective atmosphere means the moon
has been subjected to intense bombardment in its 4.5 billion- year existence.
-
- Muller's breakthrough was to find a way to date how long
ago any particle was melted - meaning he could build up a picture of whether
the moon gets a constant barrage or suffers spells of intense bombardment.
-
- He said: "The evidence clearly shows that the moon
has gone through spells of relatively frequent impacts and others of reduced
intensity. I believe it is likely that this is because the Oort Cloud is
being disturbed by a massive body that is throwing comets out of stable
orbits, a small fraction of which could reach the Earth."
-
- Muller and others believe that the dark star probably
takes about 26m years to complete an orbit around the sun.
-
- Other scientists have already noted that mass extinctions
of life on Earth seem to occur in a pattern with gaps equivalent to multiples
of 26m, suggesting some regular event is causing the comets to come Earth's
way.
-
- The best-known such event was the one that wiped out
the dinosaurs 65m years ago, but that was not the worst; the planet has
suffered several such large mass extinctions.
-
- Astronomers have found the first Earth-sized planet orbiting
another star. The discovery raises the chances of finding planets that
could support life as we know it.
-
- SIGHTINGS HOMEPAGE
- This
Site Served by TheHostPros
|