Credit: J. Pinfield for the RoPACS network at the University of Hertfordshire, 2012
Tau Ceti in the early evening sky in constellation of Cetus on Wednesday 19th December from Hatfield, UK
An international team of astronomers using the W. M. Keck Observatory
and other telescopes, has discovered that Tau Ceti, one of the closest
and most Sun-like stars, may host five planets – with one in the elusive
‘Goldilocks Zone’. Credit: Stellarium software
At a distance of twelve light years and visible with the naked eye in
the December evening sky, Tau Ceti is the closest single star that has
the same spectral classification as our Sun. Its five planets are
estimated to have masses between two and six times the mass of the Earth
– making it the lowest-mass planetary system yet detected. One of the
planets lies in the star’s habitable zone – the so-called Goldilocks
Zone with it’s ‘just right’ temperatures for supporting liquid water –
and has a mass around five times that of Earth, making it the smallest
planet found to be orbiting in the habitable zone of any Sun-like star.
The international team of astronomers, from the UK, Chile, the USA,
and Australia, combined more than 6,000 observations from three
different instruments, including HIRES on the Keck I telescope. Using
new techniques, the team has found a method to detect signals half the
size previously thought possible. This greatly improves the sensitivity
of searches for small planets and suggests that Tau Ceti is not a lone
star but has a planetary system.
“We pioneered new data modeling techniques by adding artificial
signals to the data and testing our recovery of the signals with a
variety of different approaches,” said Mikko Tuomi from the University
of Hertfordshire and the first author of the paper. “This significantly
improved our noise modeling techniques and increased our ability to find
low mass planets.”
“We chose Tau Ceti for this noise modeling study because we had
thought it contained no signals,” said Hugh Jones from the University of
Hertfordshire. “And as it is so bright and similar to our Sun, it is an
ideal benchmark system to test out our methods for the detection of
small planets.”
“Tau Ceti is one of our nearest cosmic neighbors and so bright that
we may be able to study the atmospheres of these planets in the not too
distant future,” said James Jenkins, Universidad de Chile and Visiting
Fellow at the University of Hertfordshire. “Planetary systems found
around nearby stars close to our Sun indicate that these systems are
common in our Milky Way galaxy.”
More than 800 planets have been discovered orbiting other worlds, but
planets in orbit around the nearest Sun-like stars are particularly
interesting. “This discovery is in keeping with our emerging view that
virtually every star has planets, and that the galaxy must have many
such potentially habitable Earth-sized planets,” said Steve Vogt from
University of California Santa Cruz. “They are everywhere, even right
next door! We are now beginning to understand that nature seems to
overwhelmingly prefer systems that have multiple planets with orbits of
less than one hundred days. This is quite unlike our own solar system
where there is nothing with an orbit inside that of Mercury. So our
solar system is, in some sense, a bit of a freak and not the most
typical kind of system that nature cooks up.”
“As we stare at the night sky, it is worth contemplating that there
may well be more planets out there than there are stars – some fraction
of which may well be habitable,” said Chris Tinney from the University
of New South Wales.
The W. M. Keck Observatory operates Earth’s two biggest and most
scientifically productive telescopes on the summit of Mauna Kea, Island
of Hawaii. The twin, 10-meter telescopes feature a suite of advanced
instruments including imagers, multi-object spectrographs,
high-resolution spectrographs, integral-field spectroscopy and a
world-leading laser guide star adaptive optics system. The Observatory
is a private 501(c) 3 non-profit organization and a scientific
partnership of the California Institute of Technology, the University of
California and NASA.
Media Contact:
Steve Jefferson
Communications Officer, Advancement
W.M. Keck Observatory
sjefferson@keck.hawaii.edu
(808)881-3827
Science Contact:
Mikko Tuomi
University of Hertfordshire
miptuom@utu.fi
Hugh Jones
University of Hertfordshire
h.r.a.jones@herts.ac.uk
