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| Nearby planet is a target for life | Nearby planet is a target for life |
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| Astronomers have found an Earth-sized planet with mild temperatures that's also relatively close to our Solar System. | Astronomers have found an Earth-sized planet with mild temperatures that's also relatively close to our Solar System. |
| The properties of this newly discovered planet - called Ross 128 b - make it a target in the search for life elsewhere in the cosmos. | The properties of this newly discovered planet - called Ross 128 b - make it a target in the search for life elsewhere in the cosmos. |
| At just 11 light-years away, it's the second closest exoplanet of its kind to Earth. | At just 11 light-years away, it's the second closest exoplanet of its kind to Earth. |
| The closest one, known as Proxima b, may be less hospitable for life. | The closest one, known as Proxima b, may be less hospitable for life. |
| The new world was discovered by a team using the High Accuracy Radial velocity Planet Searcher (Harps) instrument at the La Silla Observatory in Chile. The work will be published in the journal Astronomy & Astrophysics. | |
| Where should we look for alien life? | Where should we look for alien life? |
| Ross 128 b orbits 20 times closer to its star than the Earth orbits the Sun. But because its parent star - a red dwarf - is much smaller and dimmer than our yellow sun, it receives only a little more solar radiation than our own planet. | Ross 128 b orbits 20 times closer to its star than the Earth orbits the Sun. But because its parent star - a red dwarf - is much smaller and dimmer than our yellow sun, it receives only a little more solar radiation than our own planet. |
| Consequently, it is expected to have a surface temperature close to that on Earth. | Consequently, it is expected to have a surface temperature close to that on Earth. |
| Co-discoverer Nicola Astudillo-Defru from the Geneva Observatory in Switzerland said the find was the result of more than a decade of intensive monitoring using the Harps instrument. | Co-discoverer Nicola Astudillo-Defru from the Geneva Observatory in Switzerland said the find was the result of more than a decade of intensive monitoring using the Harps instrument. |
| In the search for habitable worlds beyond our Solar System, astronomers generally look for low-mass, rocky and temperate planets much like our own. | In the search for habitable worlds beyond our Solar System, astronomers generally look for low-mass, rocky and temperate planets much like our own. |
| But these are comparatively difficult to detect; most of the 3,500 known exoplanets are so-called Hot Jupiters - huge gas giants orbiting very close to their parent stars that likely don't have suitable conditions for life. | But these are comparatively difficult to detect; most of the 3,500 known exoplanets are so-called Hot Jupiters - huge gas giants orbiting very close to their parent stars that likely don't have suitable conditions for life. |
| Of the smaller contingent of Earth-sized planets, the vast majority orbit so-called red dwarf stars - the most common type. These stars are dim, which makes it easier to detect low-mass planets when they pass in front, blocking out a portion of their sunlight. | Of the smaller contingent of Earth-sized planets, the vast majority orbit so-called red dwarf stars - the most common type. These stars are dim, which makes it easier to detect low-mass planets when they pass in front, blocking out a portion of their sunlight. |
| But these stars may not create the best conditions for sustaining life on orbiting planets. They are often more active than our own Sun - meaning they periodically produce "superflares" that are associated with powerful eruptions of charged particles, battering any nearby worlds with harmful radiation. | |
| At "just" 4.2 light-years away, Proxima b is the closest exoplanet with a mild temperature. But it orbits a rather active red dwarf and, as a result, receives about 30 times more extreme ultraviolet radiation than Earth. However, Ross 128 b is the "quietest" nearby star to host a temperate exoplanet. | At "just" 4.2 light-years away, Proxima b is the closest exoplanet with a mild temperature. But it orbits a rather active red dwarf and, as a result, receives about 30 times more extreme ultraviolet radiation than Earth. However, Ross 128 b is the "quietest" nearby star to host a temperate exoplanet. |
| Astronomers often talk about a "habitable zone" around a star - it's the range of distances where temperatures allow water to remain liquid on the surface of a planet. Where the habitable zone is depends on the star itself: red dwarfs are dimmer and therefore cooler than the Sun, so their habitable zones are shifted closer in than the equivalent zone around our star. | Astronomers often talk about a "habitable zone" around a star - it's the range of distances where temperatures allow water to remain liquid on the surface of a planet. Where the habitable zone is depends on the star itself: red dwarfs are dimmer and therefore cooler than the Sun, so their habitable zones are shifted closer in than the equivalent zone around our star. |
| There's still uncertainty about whether Ross 128 b is within the habitable zone, but scientists say that with temperatures of between -60 and +20°C, it can be considered temperate. | There's still uncertainty about whether Ross 128 b is within the habitable zone, but scientists say that with temperatures of between -60 and +20°C, it can be considered temperate. |
| Follow Paul on Twitter. | Follow Paul on Twitter. |