Planet Found in Habitable Zone Around Nearest Star
Pale Red Dot campaign reveals Earth-mass world in orbit around Proxima Centauri
Astronomers using ESO telescopes and other facilities have found clear evidence of a planet orbiting the closest star to Earth, Proxima Centauri. The long-sought world, designated Proxima b, orbits its cool red parent star every 11 days and has a temperature suitable for liquid water to exist on its surface. This rocky world is a little more massive than the Earth and is the closest exoplanet to us — and it may also be the closest possible abode for life outside the Solar System.
Just over four light-years from the Solar System lies a red dwarf star that has been named Proxima Centauri as it is the closest star to Earth apart from the Sun. This cool star in the constellation of Centaurus is too faint to be seen with the unaided eye and lies near to the much brighter pair of stars known as Alpha Centauri AB.
At times Proxima Centauri is approaching Earth at about 5 kilometres per hour — normal human walking pace — and at times receding at the same speed. This regular pattern of changing radial velocities repeats with a period of 11.2 days. Careful analysis of the resulting tiny showed that they indicated the presence of a planet with a mass at least 1.3 times that of the Earth, orbiting about 7 million kilometres from Proxima Centauri — only 5% of the Earth-Sun distance.
At times Proxima Centauri is approaching Earth at about 5 kilometres per hour — normal human walking pace — and at times receding at the same speed. This regular pattern of changing radial velocities repeats with a period of 11.2 days. Careful analysis of the resulting tiny Doppler shifts showed that they indicated the presence of a planet with a mass at least 1.3 times that of the Earth, orbiting about 7 million kilometres from Proxima Centauri — only 5% of the Earth-Sun distance.
Although Proxima b orbits much closer to its star than Mercury does to the Sun in the Solar System, the star itself is far fainter than the Sun. As a result Proxima b lies well within the habitable zone around the star and has an estimated surface temperature that would allow the presence of liquid water. Despite the temperate orbit of Proxima b, the conditions on the surface may be strongly affected by the ultraviolet and X-ray flares from the star — far more intense than the Earth experiences from the Sun.
This discovery will be the beginning of extensive further observations, both with current instruments and with the next generation of giant telescopes such as the European Extremely Large Telescope (E-ELT). Proxima b will be a prime target for the hunt for evidence of life elsewhere in the Universe. Indeed, the Alpha Centauri system is also the target of humankind’s first attempt to travel to another star system, the StarShot project.
How Science Can Learn More About ‘Proxima b’ And All Earth-Like Worlds
“This planet is almost definitely tidally locked to its star, meaning that the same hemisphere always faces the star and the opposite hemisphere always faces away, just like the Moon does to Earth. The star itself is active and flares frequently, meaning that catastrophic radiation impacts the Sun-facing side quite regularly, but never touches the dark side. And the “seasons” are determined by the ellipticity of its orbit, rather than its axial tilt. But there’s still so much left to learn, and we have a number of different technological avenues to explore – including potentially all of them – if we want to learn more about it.”
Now that we’ve learned the nearest star to our Sun, Proxima Centauri, has a rocky planet at the right distance for liquid water, it’s time to consider how we might learn the answers to our burning questions about it and all nearby Earth-like exoplanets. What’s the atmosphere like, and what does it consist of? What does the surface of the world look like, and what’s on it? And is there life, or intelligent life, present at all? There are three ways to conduct these searches, and they’re all complementary. We can use giant ground-based telescopes, including arrays of telescopes, for high-resolution spectroscopic images of these worlds. We can use space-based telescopes with coronagraphs or starshades to image these worlds directly over time. Or we could undertake a journey across space, and visit the system directly to obtain in situ measurements we could never get from afar.