Page 48 - All About Space 68 - 2017 UK

Sun's twin

Piotr Dybczyński said this could be the “strongest
disrupting encounter in the future and history of the
Solar System.” Owing to its huge distance from us at
the moment, however, Gliese 710 is almost certain
not to be the fabled Nemesis.
These are interesting quirks, but while they
perhaps hint at hidden objects we cannot see, they
are a better representation of what we can see.
Astronomers have found gravitational evidence
for a planet orbiting within the outer Solar System,
and they can see a star dozens of light years away
heading in our direction. If there was a star in orbit
around our Sun, just a few light years away, we would
almost certainly know about it.
Muller, of that original 1984 paper, has his own
take on why this might be so. In a short comment to
All About Space, he said that WISE had not looked
absolutely everywhere. Specifically, it could not see
beyond the middle of the Milky Way, the galactic
plane, where the stars are most dense. “If Nemesis
NASA's WISE telescope, now
exists, it lies close to the galactic plane,” he said. “This known as NEOWISE, has looked
is the region that is most difficult to survey. If the
for Nemesis, but has currently
WISE survey is complete in this part of the sky, I’d be found no sign that it exists
very interested! Last time I looked it wasn’t.”
We asked a couple of astronomers for their
thoughts on whether Nemesis could be hiding here.
Luhman, who conducted that research in 2013, said “ There's a very
it was pretty unlikely. “If the companion happened
to be near a bright star (in the galactic plane or small chance that a
elsewhere) when observed by WISE, it could have
gone unnoticed,” he said. “So there's a very small companion in the
chance that a companion in the mass range proposed
for Nemesis does exist. But that chance decreases mass range proposed
every time that a new survey is performed and
doesn't find such an object.” David Morrison, the for Nemesis does
Senior Scientist of the new Solar System Exploration
Research Virtual Institute (SSERVI) at NASA, exist" Dr Kevin Luhman
responded with a more simple answer: “No.”
If you’re still not convinced, we’ve got one final
nail in the coffin. In 2011, Coryn Bailer-Jones from
the Max Planck Institute for Astronomy (MPIA)
published a paper in the Monthly Notices of the
Royal Astronomical Society, refuting the initial idea
of extinctions every 26 to 30 million years. He found
that the supposed periodical patterns in extinctions
were nothing more than statistical artifacts, meaning
that Earth was just as likely to suffer a major impact
now as it was in the past. Looking at the craters on
Earth, he found absolutely no pattern to the number
of impacts. If anything, he found that there was a
slight increase in impacts in the last 250 million
years, but certainly nothing that would point towards
a regular disruption of the Solar System. “From the
crater record there is no evidence for Nemesis,” he
said in a statement at the time.
So, where does that leave us? Well, there’s certainly
a lot of evidence for dim objects being discovered
in the outer Solar System, and we’re also getting
much better at locating other stellar mass objects
in our vicinity. However, the idea of a star in orbit
around our Sun regularly causing mass extinctions
seems exceedingly unlikely. We’ve found no
observational evidence for such a star, and even the
initial theory seems to be falling apart. Nemesis, like We're continuing to find
other doomsday theories, will almost certainly just previously undetected objects ©NASA, NASA/JPL-Caltech
be consigned to history as an interesting thought like the dwarf planet Eris
experiment – and nothing more.

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