An Australian astronomer says it is “incredibly exciting” a possibly habitable Earth-sized planet has been found.
It is orbiting a nearby star, and astronomers believe there could be many more planets like it.
The planet – discovered by astronomers at the University of California, Santa Cruz, and the Carnegie Institution of Washington – is orbiting in the middle of the “habitable zone” of the red dwarf star Gliese 581, which means it could have water on its surface.
Liquid water and an atmosphere are necessary for a planet to possibly sustain life, even it it might not be a great place to live, the scientists said.
The discovery of the planet was significant as it was the “first planet that we found that’s definitely in the Goldilocks zone”, Australian Astronomical Observatory’s research astronomer Simon O’Toole said.
The Goldilocks zone is a zone in which a planet is at just the right distance from its star. This means it is not too hot nor not too cold, and has the ideal temperatures for habitation.
“This is significant because we’ve always wanted to know, ‘Are we alone? Is there life out there?’ ” Dr O’Toole said.
“In our galaxy, we’ve looked at a couple of thousand stars, not all of them with a sensitivity like this.
“There are a hundred billion stars in our galaxy. So to find another habitable planet within a thousand stars – a sample size like that – that suggests there must be a lot of these kinds of planets.”
Dr O’Toole said the astronomers’ discovery was a “remarkable piece of work” as planets the size of Earth were difficult to find.
“Planets like Jupiter are relatively easy to find because they are massive and leave a large signal.
“It’s incredibly exciting. It’s something that we have been inching our way towards for the past 15 years.
“Fifteen years ago next week was the discovery of the first extrasolar planet around a star like our sun and here we are, almost 15 years to the day and we are finding a planet that could sustain life.
“This is fantastic.”
You could ‘walk upright’ on the planet
The scientists determined that the planet, which they have called Gliese 581g, has a mass three to four times that of Earth and an orbital period of just under 37 days.
Its mass indicates it is probably a rocky planet and has enough gravity to hold on to an atmosphere, said Steven Vogt, professor of astronomy and astrophysics at the University of California, Santa Cruz, and one of the leaders of the team that discovered the planet.
If Gliese 581g has a rocky composition similar to Earth’s, its diameter would be about 1.2 to 1.4 times that of the Earth, the researchers said.
The surface gravity would be about the same or slightly higher than Earth’s, so that a person could easily walk upright on the planet, Professor Vogt said.
Gliese 581g was discovered by scientists working on the Lick-Carnegie Exoplanet Survey, during 11 years of observing the Gliese 581, which is 20 light years from Earth.
For astronomers, 11 years of observation is considered a short time and 20 light years, which is roughly 190 trillion kilometres, rather close. The sun is about 8
