The ‘Second Earth’ orbiting our nearest star

Deep red sky: An optimistic artist’s impression of the surface of Proxima b. © ESO

Meet Proxima b, a newly discovered exoplanet just four light years from Earth. Scientists say it could be rocky, watery, and habitable. Should we be optimistic about finding alien life there?

Twenty-five years ago scientists were unsure that they would ever find planets in other solar systems. In 1992 two came along at once. Since then they have found over 3,000 — and they now think that there could be tens of billions more scattered throughout the universe.

But this week, a group of scientists announced ‘the most important exoplanet discovery there will ever be’: a world which could sustain life right next door.

Well, almost. Proxima Centauri is a red dwarf star 25 trillion miles away, but it is our sun’s closest star neighbour. Its small size means it gives out far less energy, but the new planet, Proxima b, is right in its ‘Goldilocks zone’. That means its orbit is not too hot and not too cold for water to exist on the surface. And where there is water there could also be life.

That is far from a guarantee. Scientists detected the planet by measuring the ‘wobbles’ in gravity as it orbited its star. They have no idea what it looks like, only that its mass is at least 1.3 times as large Earth’s. That could mean a surface rocky and watery — but alternatively as dry as Mars, or as inhospitable as Venus.

Then there is the question of an atmosphere. If one exists, it could help warm the planet’s temperature up from a chilly -40°C. But Proxima Centauri is a volatile star, giving off flares of radiation which could strip away the planet’s surrounding gases.

Scientists also think it could be in a tidal lock, meaning one of its faces always points towards the star — half in day, half in night, forever.

Despite these caveats, scientists are incredibly excited by the discovery. They do not have the technology to reach the planet yet — but just knowing it is there could be the motivation they need to invent it. Could it one day lead them to intelligent life?

PB phone home

Some scientists are hopeful about finding other civilisations out there. They point to the ‘Drake equation’, a calculation which estimates the likelihood based on the number of planets, the chance of life evolving on each, and so on. Finding a habitable planet just one star over is good news; even if it does not host life, it suggests that there are billions more which might. With so many planets to explore, how could we be alone?

Others are sceptical. Consider another thought experiment, known as ‘Fermi’s Paradox’, summarised in just three words: where is everybody? If alien civilisations really did exist, surely we would have found them by now — or vice versa? Scientists have been searching for centuries; but no matter how advanced their technology gets, they never find anyone. We must admit that the universe is a lonely place, and be grateful for our amazing home in it.

You Decide

  1. Will scientists ever find intelligent civilisations on other planets?
  2. If they do, what message would you want to send about Earth?

Activities

  1. The image at the top of this story features the surface of Proxima b glowing in the pale red light of the dwarf star Proxima Centauri; the twin stars Alpha Centauri A and B are in the distance. Imagine this is your view from a spaceship which has landed on the planet for the first time. Write a diary entry explaining your feelings.
  2. Draw and label a diagram which compares Proxima b to Earth.

Some People Say...

“Humans should save their own planet before they go looking for others.”

What do you think?

Q & A

So when will we know more about this mysterious planet?
First, astronomers are just hoping to see it: you can expect quite a few telescopes to be trained its way over the coming years. Unfortunately, Proxima Centauri is so weak that there are virtually no telescopes strong enough to spot the planet unless it crosses in front of the star from a helpful angle. The more likely solution is waiting a few years for better instruments.
Could we visit it one day?
Perhaps, although it would take tens of thousands of years if we used our current rocket technology. But don’t fear: the billionaire Yuri Milner has launched a project called ‘Breakthrough Starshot’ which aims to create spacecrafts which travel at one-fifth the speed of light — if he is successful, the journey will take around 20 years.

Word Watch

1992
The first two exoplanets were discovered orbiting a ‘pulsar’, a star which died in a supernova. They are part of the Virgo constellation. Three years later, ‘51 Pegasi b’ became first exoplanet to be found orbiting a star like our own. Since 2009, over 1,000 have been found by NASA’s Kepler telescope.
Exoplanet
Short for ‘extra-solar planets’, or planets which orbit stars outside our own solar system.
Orbit
Proxima b’s orbit lasts 11.2 Earth days.
Mars
Although liquid water might have been discovered on the surface of Mars last year, it is extremely rare — not like the oceans which cover Earth.
Venus
Although Venus is roughly the same size as Earth, it is far more volatile: its thick atmosphere mostly contains carbon dioxide, its temperatures reach over 400°C, and its clouds do not contain water — they are made from corrosive sulphuric acid.
Tidal lock
This happens when an orbiting world is close to the object it is orbiting. The most obvious example is the moon, which is locked to Earth.

Subjects

PDF Download

Please click on "Print view" at the top of the page to see a print friendly version of the article.