The possibility of finding a rocky planet where water-based life may
exist took a giant leap forward after five Earth-sized planets were
identified around a distant star in the Milky Way galaxy.
all five planets are too close to their sun and too hot to harbour life,
scientists said the fact that they were formed many billions of years
ago when the galaxy was still young suggests that rocky, Earth-sized
planets could be more ubiquitous than previously thought.
The planets in the distant solar system range in sizes between
Mercury and Venus and were discovered by analysing data gathered by
Nasa’s Kepler space telescope.
Kepler has so far identified more than 4000 planetary “candidates”, of which 1013 have been confirmed as true planets.
star around which the five exoplanets orbit is known as Kepler-444,
located 117 light years away in the constellation Cygnus and Lyra.
star, which is 25 per cent smaller than the Sun, formed 11.2 billion
years ago, less than 20 per cent of the age of the galaxy and long
before the formation of the Sun.
This means that this ancient
solar system is the oldest known group of terrestrial-sized planets in
the Milky Way, about two-and-a-half times older than Earth, scientists
said in a study published in the Astrophysical Journal.
are far-reaching implications for this discovery. We now know that
Earth-sized planets have formed throughout most of the Universe’s 13.8
billion-year history, which could provide scope of the existence of
ancient life,” said Tiago Campante of the University of Birmingham.
the time the Earth formed, the planets in this system were already
older than our planet today. This discovery may now help to pinpoint the
beginning of what we might call the era of planet formation.”
scientists made their discovery by monitoring the tiny fluctuations in
light from the Kepler-444 star as each planet passed in between the star
and the telescope.
The size and age of the planets were
estimated from analysing the resonating sounds trapped within the star,
in a technique known as asteroseismology.
Professor Bill Chaplin
of Birmingham University said finding terrestrial-sized planets in such
an ancient solar system demonstrates that planets similar in size to the
Earth were formed many billions of years before the birth of our Solar
“It’s a very old star so we are looking back a long way
into the history of the galaxy. It tells us that small planets were
formed in this early epoch of the galaxy,” Professor Chaplin said.
demonstrates that small rocky planets were being formed in the early
universe, which would have been true for many, many other stars in the
galaxy,” he said.
“It raises the potentially interesting
possibility that if rocky planets formed so early, then some would be in
the habitable zone around their stars which opens the possibility of
early rocky planets where life would have developed,” he added.
five planets have orbits around their parent star of less than 10 days,
which is equivalent to less than a tenth of the distance between the
Earth and the Sun, and within the orbit of Mercury, where surface
temperatures can reach 420C.
The Kepler telescope has found
several distant solar systems, including a system with five planets,
called Kepler-62, which included two “super-Earth”-sized planets in the
habitable zone where liquid water could exist.
believe that liquid water and a rocky surface are probably both
necessary for the origin and evolution of life, which is why Kepler’s
efforts are concentrating on Earth-sized rocky planets orbiting within
the habitable zone where it is not too hot nor too cold for water to
exist in liquid form.