Planet in star system nearest our Sun 'may have oceans'

October 6, 2016
An artist's impression of the planet Proxima b, orbiting the red dwarf star Proxima Centauri, released by the European Southern Observatory on August 24, 2016

A rocky planet discovered in the "habitable" zone of the star nearest our Sun may be covered with oceans, researchers at France's CNRS research institute said Thursday.

A team including CNRS astrophysicists have calculated the size and surface properties of the planet dubbed Proxima b, and concluded it may be an "ocean planet" similar to Earth.

Scientists announced Proxima b's discovery in August, and said it may be the first exoplanet—planet outside our Solar System—to one day be visited by robots from Earth.

The planet orbits within a "temperate" zone from its host star Proxima Centauri, some four light years from us.

It is estimated to have a mass about 1.3 times that of Earth, and orbits about 7.5 million kilometres (4.6 million miles) from its star—about a tenth the distance of innermost planet Mercury from the Sun.

"Contrary to what one might expect, such proximity does not necessarily mean that Proxima b's surface is too hot" for water to exist in liquid form, said a CNRS statement.

Proxima Centauri is smaller and 1,000 times weaker than our Sun, which means Proxima b is at exactly the right distance for conditions to be potentially habitable.

"The planet may very well host liquid water on its surface, and therefore also some forms of life," the statement said.

Discovery of an exoplanet near Earth

The size of exoplanets are generally calculated by measuring how much light they block out, from Earth's perspective, when they pass in front of their .

But no such transit of Proxima b has yet been observed, so the team had to rely on simulations to estimate the planet's composition and radius.

They calculated the radius was between 0.94 and 1.4 times that of Earth, which is 6,371 kilometres on average.

Assuming a minimum radius of 5,990 km, the planet would be very dense, with a metallic core making up two-thirds of the entire planet's mass, surrounded by a rocky mantle.

If there is surface water, it would not contribute more than 0.05 percent to the planet's total mass, the team said—similar to Earth, where it is about 0.02 percent.

In the larger planet scenario, with a radius of 8,920 km, Proxima b's mass would be split 50-50 between a rocky centre and surrounding water.

"In this case, Proxima b would be covered by a single, liquid ocean 200 km deep," said the CNRS.

"In both cases, a thin, gassy atmosphere could surround the planet, like on Earth, rendering Proxima b potentially habitable," it concluded.

Explore further: Proxima b could be a life-friendly planet, says one of the co-discoverers

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18 comments

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Osiris1
3.5 / 5 (2) Oct 06, 2016
Here the race to the stars begins. Earth II may exist and exist nearby. No one will be able to stop the coming space race.
Shootist
2 / 5 (3) Oct 06, 2016
Here the race to the stars begins. Earth II may exist and exist nearby. No one will be able to stop the coming space race.


As much as finding a planet with liquid water on its surface would be a scientific boon, it is quite unlikely an "Earth Two" will be found to be a tidally locked planet orbiting a mere 7.5 Mk from its primary.
Spirckle
5 / 5 (5) Oct 06, 2016
a tidally locked planet

While this is likely, one should note that there are other possible configurations that would make a planet livable so close to its star.

1. It could have a largish moon (a la Titan) in a tight orbit around the main planet. The moon could have water, an atmosphere and due to its orbit, experience more typical day/night cycles.

2. It could be a double planet of two Mars sized planets orbiting a common barycenter. This also would provide more reasonable day/night cycles.

In all, I think it would be worth investigating, to at least know what we have so close to home.
TrollBane
5 / 5 (3) Oct 06, 2016
Large moons and double planets are long shots, especially that close to a star. It could also spin like Mercury, slowly but in a 3:2 ratio instead of 1:1. Depending on the day length, that might be less habitable than a full tidal lock.

One thing this article avoids mentioning is that the 1.3 Earth masses is the lower limit, and the real deal could be considerably more massive. It depends on how the plane of the system is angled from our point of view.
entrance
1 / 5 (8) Oct 07, 2016
@Osiris1

Aliens could stop us. I think, the probability is rather high, that other species don´t want us to conquer foreign planets with intelligent being. We would bring illness and wars to them.

Maybe they have already destroyed two of our solar system´s planets: Mars and a planet, which is nowadays known as Asteroid Belt. Maybe there already existed highly intelligent beings.

As long as we are not able to solve our problems on Earth, aliens certainly won't accept us. With problems i mean overpopulation, water and air pollution, global warming, wars, financial unbalances, certain political systems, and so on ...

We should really try to solve these problems. I am ready to help.
Mark Thomas
3.3 / 5 (3) Oct 07, 2016
TrollBane, good comment. I read the range of masses for Proxima b is from 1.27 (within error bars) to just under 3 earth masses in 90% of the scenarios, so it stands to reason there could be a correspondingly wide variety of atmospheric and surface conditions. One hopeful fact is the sunlight there as compared to Earth's is only 65%, so a thinker atmosphere that a more massive planet might have could be offset by less sunlight to keep conditions closer to being Earth-like. For comparison, the sunlight at Mars is about 48% of Earth's.
torbjorn_b_g_larsson
5 / 5 (2) Oct 07, 2016
The 0.02 % per mass for Earth is the oceans, but the consensus water content is 0.05 % based on "one water below for one above" of geological estimates for the crustal water content. So the upper limit for Proxima b is an exact match.

@Shootist: The consensus is swaying to that tidal locked planets can easily be habitable, since a habitable (i.e. rather thick) atmosphere can transport heat. The Proxima b papers covers that.

And mind that M dwarf planet in the habitable zone doesn't need to be tidal locked. C..f. how our own Mercury is in a 3:2 resonance instead. It had a 30 % chance to end up that way, so it isn't an unexpected outcome.
jonesdave
5 / 5 (1) Oct 08, 2016
As much as finding a planet with liquid water on its surface would be a scientific boon, it is quite unlikely an "Earth Two" will be found to be a tidally locked planet orbiting a mere 7.5 Mk from its primary.


Around a flare star, to boot.
However, it gives me a chance to plug one of my favourite authors: try getting hold of 'Proxima', by Stephen Baxter.
carbon_unit
3 / 5 (2) Oct 08, 2016
Proxima is probably my next book to get. In turn, I recommend 'Seeker' by Jack McDevitt. Both Baxter and McDevitt are good hard SF authors.
TheGhostofOtto1923
3 / 5 (2) Oct 09, 2016
Maybe they have already destroyed two of our solar system´s planets: Mars and a planet, which is nowadays known as Asteroid Belt. Maybe there already existed highly intelligent beings
I like that idea but I suspect that it's not original. Where did you read it?

As this is a science site we like to share knowledge properly. Knowing the source helps us to learn as much as we can.
jonesdave
5 / 5 (1) Oct 09, 2016
Maybe they have already destroyed two of our solar system´s planets: Mars and a planet, which is nowadays known as Asteroid Belt. Maybe there already existed highly intelligent beings
I like that idea but I suspect that it's not original. Where did you read it?

As this is a science site we like to share knowledge properly. Knowing the source helps us to learn as much as we can.


I actually thought this guy was having a laugh - surely he wasn't serious? There is nowhere near enough material in the asteroid belt to make a decent sized planet. Please tell me he wasn't being serious. Maybe he could join Solon in the 'Sun is invisible in visible wavelengths from space' thread.
All fruit loops unite!
yaridanjo
1 / 5 (1) Oct 09, 2016
I find it very interesting that the scientific community just hits the 'off switch' when it comes to the possibility of space mobile ET aliens visiting Earth. There seems to be an attitude that implies if we can't travel between the stars, no one can. More embarrassing is that we are not the only sentient beings on planet Earth, and the other one has a larger brain than we do, but it is not technological.

There is a reasonable possibility. Proxima Centauri b is already inhabited by a space mobile sentient species. We humans are not the most intelligent species in the galaxy. More likely, we are one of the least intelligent. The Cenos ET aliens have been known to inhabit this water world since August 2012. One was even caught visiting Taiwan in December 2012. They are a tall, amphibian species. Here is a report on these beings who have been visiting Earth for the past 4300 years.

http://yaridanjo..../PS.html
HANDS
UNIQUE DESCRIPTIONS OF TWO ET ALIEN CULTURE
yaridanjo
1 / 5 (1) Oct 09, 2016
These Cenos aliens gave we humans technical information that we are just beginning to use. They gave the ancient Akkadians the mass of our Jovian planets relative to the Sun 4300 years ago. Also the mass of planet Nine (or ten) was revealed then.

http://www.barry....d.html#2
VULCAN IN ANCIENT DATA

Humans started catching up with their technology circa 1680 AD when Newton came up with the concept of mass. BTW, the other sentient species here are the the CETACEANS who,may also be telepathic.
jsdarkdestruction
5 / 5 (2) Oct 09, 2016
"Telepathic contact between human and extra-terrestrial technological and non- technological alien civilizations appears to be a practical means to acquire verifiable information concerning their existence"

The first sentence of your link.....are you kidding me? Telepathy?
Edenlegaia
5 / 5 (1) Oct 10, 2016
We humans are not the most intelligent species in the galaxy. More likely, we are one of the least intelligent.


Well, the most intelligent species in the galaxy are certainly NOT polite enough to say hello then. And THAT, above the number of sentient beings on Earth, is really embarrassing. How difficult is it to simply use a galactic phone? They need to build a galactic network or something for that?
Rude!
jonesdave
5 / 5 (1) Oct 10, 2016
Never mind intelligent aliens, I sometimes despair about the intelligence of some members of our own species.
yaridanjo
1 / 5 (6) Oct 10, 2016
"The first sentence of your link.....are you kidding me? Telepathy?"

It's hard for humans to imagine that there are sentient species more advanced than they are. We are a 'warrior' sentient species and 'being telepathic' is not very compatible with the expression of the 'Warrior' lifestyle. Nevertheless, there are a few humans that are telepathic and they have been used by the military in the 'Alien Interview' program.

Humans may not like this, but it is just the way the universe works. Telepathy may be a way the cetaceans communicate and we humans just just close our mind to this possibility. While the whales and dolphins are not technological, they may be very aware of ETs and be much more knowledgeable about the universe than we give them credit for. We humans still harpoon these sentient beings bearing witness to us being the more primitively beings.
TheGhostofOtto1923
3.7 / 5 (3) Oct 15, 2016
I actually thought this guy was having a laugh - surely he wasn't serious? There is nowhere near enough material in the asteroid belt to make a decent sized planet
If anybodys still here...

Google tells us this was a common idea.
https://en.wikipe..._planet)

-and we can also find out that indeed there is enough matter to make a planet (or a bigger planet)

"The only thing preventing Ceres being considered a planet is the fact that its orbit is so crowded with other asteroids (it is already large enough for gravity to have made it spherical, which is the other key part of the definition of a planet). Therefore, you don't actually need to combine the asteroids together, just get rid of all the rest of them and Ceres will be a planet.

"You could combine them with Ceres to make a slightly larger planet, but it would still be too small to hold an atmosphere."

-etc.

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