“We think the Sun's companion drifted away
billions of years ago, within a million years after
the Sun and its companion formed” StevenStahler
Evidence
for Nemesis'
existence
Although yet to
be proven, there
are signs pointing
towardsa twinstarCompanion stars do exist
We know that many stars have
a companion, but in 2017 it was
suggested that pretty much every
star like the Sun had one. Indeed,
Sarah Sadavoy and Steven Stahler
argued the case for our Sun's
companion, but said the partner
separatedshortlyafterformation.Other binaries
have similar effects
In 2006, debris discs around
two nearby stars were seen by
researchers at the University of
California, Berkeley, to resemble
the Kuiper Belt with a sharp outer
edge. It was proposed that a
companionstarcausesthiseffect.ThepresenceofSedna
Atrans-Neptunianobjectcalled
Sednahasanunusualelliptical
orbitaroundtheSun,andsome
saythisisduetotheinfluenceofa
potentialbinarycompanion.Sedna,
withanorbitof12,000years,has
beenheraldedasstrongproofofa
companionstarfortheSun.Itisjusttoofaraway
It'snotevidenceperse,butthe
Sun'scompanionstar– atleast
followingSadavoyandStahler's
model– couldnowbethousands
oflightyearsaway,whichaccounts
forwhyithasneverbeenseen.when Lucie Jílková of Leiden Observatory in the
Netherlands suggested a passing star f lung it into
interstellar space when the Sun was very young.
Yet today Brown tells us that he's not too certain
about such theories. “Sedna's orbit is most likely
caused by Planet Nine,” he says, referencing a
hypothetical planet in the outer region of the Solar
System. In that sense, he believes there simply is
noNemesis.
“Very sensitive searches have failed to discover
it,”he affirms. “And, more importantly, the idea
thatthere was periodic extinction appears to have
been a misinterpretation of the data. So I think
there is both no Nemesis and no need to explain
the data! I'm also pretty sure that Nemesis
hasn't been a viable hypothesis for more than
a decade.”
Even so, the case remains open because
the hypothesis of a companion star has
actually moved on in recent years. While the
original theory of Nemesis is perhaps not as
strong today as it previously has been, thereremains a firm belief in some quarters that the Sun
was not born alone.
In 2017, Sarah Sadavoy and Steven Stahler carried
out a study called ‘Embedded Binaries and their
Dense Cores’. Sadavoy, then a radio astronomer
from the Max Planck Institute for Astronomy and
Stahler, a theoretical physicist from the University
of California, Berkeley, discussed how radio surveys
of a giant molecular cloud filled with recently
formed stars in the constellation Perseus led them
to theorise that all Sun-like stars are likely to have
been born with companions.
“I do believe this,” Stahler tells All About Space.
“The fact was already known for massive stars,
and in 2017 Sarah Sadavoy and I provided strong
evidence that low-mass stars like the Sun also tend
to form with a companion.” In the case of the Sun,
this happened 4.5 billion years ago and meant
it was born along the same lines as our nearest
neighbour, Alpha Centauri, which is a triplet system.
“I believe there was probably a Nemesis a long
time ago,” he says, explaining that the mathematical© NASA/JPL-CaltechIllustration © Tobais RoetschMYSTERIES
UNIVER SE
OF
THE