Page 47 - All About Space 68 - 2017 UK
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Sun's twin
In July 2017 astronomers
announced evidence that all
Alpha Centauri stars may form as pairs
Proxima Centauri
How long it would
take to orbit
Nemesis was predicted to
take about 26 to 30 million
years to orbit, in line with
the supposed periodic
extinctions on Earth
“ I should not have used the name Nemesis
for the Sun's old companion. It drifted away
long ago, and was not related at all to the
How it would disrupt
the Solar System extinction of the dinosaurs” Dr Steven Stahler
The Oort cloud is thought
to extend about one
light year from the Sun, Don't get too excited just yet, though. This star was Solar System. And astronomers are busy searching
meaning Nemesis would almost certainly not the Nemesis we've been talking for an even bigger object right now, the hypothesised
pass close enough to send about here, being much too far away and unlikely Planet Nine, the existence of which has been hinted
comets our way. ever to return. In fact, it was not actually found, its at by the strange warped orbits of objects in the
existence was instead inferred from other evidence. Kuiper Belt and Oort cloud.
The astronomers looked at a cloud of dust and gas And that’s not all. In late 2016, astronomers
in the Perseus constellation that is a typical region announced they had found a star that was heading
that forms stars. In this region, all stars were found straight towards us. Namely Gliese 710, which is
to seemingly be forming in pairs, leading them to currently about 64 light years from Earth, but in
suggest that this rule should hold everywhere. about 1.35 million years, it’s predicted to come as
This true companion, similar in mass to our Sun, close as 0.2 light years to our Sun. That, as you
would have orbited dozens of times 4.6 billion years may have already calculated, is well inside the
ago when the Sun was born. After about a million Oort cloud. In their paper, published in Astronomy
years, it would have been flung away – billions of and Astrophysics, the authors Filip Berski and
years before the dinosaurs arrived – never to return.
If our true companion did exist, which seems much
more likely than the existence of Nemesis, it's
probably now thousands of light years away, and we
are unlikely to ever find it.
“In retrospect, I should not have used the name
The closest point
to our Sun Nemesis for the Sun's old companion,” Stahler tells
At its closest point in All About Space. “It drifted away long ago, and was
its orbit, Nemesis was not related at all to the extinction of the dinosaurs.
predicted to come I don't think there was a star responsible for the
within half a light-year dinosaur extinction. This star should have been
of our Solar System. found if it existed.”
That is not to say objects do not go without
detection. Consider that dwarf planets, objects ©NASA, ESA and J. Muzerolle, STScI, ©ESA/NASA/SOHO
smaller than a planet but larger than an asteroid, are
still being discovered today. One of these, Eris, was
found back in 2005. Another, 2014 UZ224, was only
announced in 2016. It’s thought there could be many, Our Sun may have once had a companion,
even hundreds, more of dwarf planets in the outer but it has long since disappeared from view
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