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Hubble to narrow hunt for alien life
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Hubble to narrow hunt for alien life THE search for alien life is taking a shortcut. The Hubble Space Telescope is set to spend hundreds of hours over the next year running reconnaissance on a shortlist of worlds to identify those we should scour for life first. This latest effort aims to take advantage of Hubble’s successor, the James Webb Space Telescope. Set to launch in 2018, JWST will have unprecedented power to detect the atmospheres of faraway planets for biosignature gases that would suggest they host living, breathing organisms. But competition for JWST time will be fierce. And there may not be time for much of a learning curve. The $8 billion telescope is supposed to last at least five years, but if something breaks, it can’t be fixed. That’s why it’s important that Hubble narrows the field for JWST now. Here’s an early look at Hubble’s itinerary. The exo-Venus
Hubble has already started studying GJ 1132b, a planet 40 light years away that was first spotted in May 2015. It’s very close to its star and so probably too toasty to host life, but we can use it to practise measuring the atmosphere of a rocky world. Many of the first planets JWST will study are orbiting small, cool M dwarf stars, whose outbursts might erode planets’ atmospheres (see “Look to the stars”, right). Observations by Zach BertaThompson at the University of Colorado at Boulder last year hinted that GJ 1132b was surrounded by a cloud of neutral hydrogen – a sign it was losing its gas to space, which may render it uninhabitable. More in-depth observations may confirm the 10 | NewScientist | 26 November 2016
rate at which its atmosphere is leaking, and may identify specific molecules. The super-Earths
Either K2-18b or K2-3d, two planets discovered in the second phase of the Kepler mission, might have the whole package. Both orbit bright nearby stars that could reveal their atmospheres, and are at the right distances for both to host liquid water. The only obviously weird thing about these planets is their size. Both are super-Earths, wider than our planet. K2-3d is 1.6 times larger than Earth and likely rocky; K2-18b is 2.3 times larger and may have a thick, puffy atmosphere. Hubble will spend about five days over the next year studying these planets. Both might have hydrogen-rich atmospheres, or be completely blanketed by clouds, says Björn Benneke at the California Institute of Technology. But if the molecular signature of water, methane or ammonia shows up on either planet, it would mean we have a real chance to look for biosignatures. “If we found any signal, then we would hit this pair extremely hard with James Webb,” Benneke says. “There’s no doubt about that.”
nasa
Joshua Sokol
–Scouting for life– The TRIPLETS
One ultra-cool dwarf star, TRAPPIST-1, offers a discount rate: three planet siblings, all within about 20 per cent Earth’s size. Of those three planets, announced in May 2016, one or two might be water-friendly. Later this year, the team that discovered the triplets used Hubble to find that two of the planets lack big, puffy atmospheres, which suggests they are rocky. This December and January, they will use Hubble
Look to the stars A good world is hard to find – but that’s only half the battle. “Context is everything in many aspects of life,” says Evgenya Shkolnik at Arizona State University. “In the case of exoplanets, that context is the star.” Shkolnik is leading an effort to spend about a week using Hubble to observe small, cool M dwarf stars to understand effects that could hide life on their planets, or give a signal that looks like life but isn’t.
Habitable-zone planets around M dwarfs are subject to erratic bursts of ultraviolet radiation, which would destroy biosignature molecules in an atmosphere. UV radiation can also break up water, which could increase the concentration of oxygen even with no living organisms responsible. Ultraviolet radiation is harmful to life on its own, too. So the star’s temperament will play a key part in deciding whether to study a planet.
again to measure how thick the atmospheres are, says Julien de Wit at the Massachusetts Institute of Technology. Their findings will help them plan a proposal to study the triplets during JWST’s first year. The next-door neighbour
You couldn’t find a closer potentially habitable planet than Proxima b – an Earth-sized world around the next star over – if you tried. But Proxima b has a downside: it never transits in front of its star, making it far harder to study. All is not lost. We could look for the planet’s phases: minute changes in the system as the planet orbits its star and points different faces at Earth. If JWST saw heat speeding from one side of the planet to the other, it would show that the planet has an atmosphere in the first place, says Laura Kreidberg at Harvard University. Or with a few months of solid staring by JWST we might be able to detect ozone, a possible biosignature, in its atmosphere. n
Hubble to narrow hunt for alien life THE search for alien life is taking a shortcut. The Hubble Space Telescope is set to spend hundreds of hours over the next year running reconnaissance on a shortlist of worlds to identify those we should scour for life first. This latest effort aims to take advantage of Hubble’s successor, the James Webb Space Telescope. Set to launch in 2018, JWST will have unprecedented power to detect the atmospheres of faraway planets for biosignature gases that would suggest they host living, breathing organisms. But competition for JWST time will be fierce. And there may not be time for much of a learning curve. The $8 billion telescope is supposed to last at least five years, but if something breaks, it can’t be fixed. That’s why it’s important that Hubble narrows the field for JWST now. Here’s an early look at Hubble’s itinerary. The exo-Venus
Hubble has already started studying GJ 1132b, a planet 40 light years away that was first spotted in May 2015. It’s very close to its star and so probably too toasty to host life, but we can use it to practise measuring the atmosphere of a rocky world. Many of the first planets JWST will study are orbiting small, cool M dwarf stars, whose outbursts might erode planets’ atmospheres (see “Look to the stars”, right). Observations by Zach BertaThompson at the University of Colorado at Boulder last year hinted that GJ 1132b was surrounded by a cloud of neutral hydrogen – a sign it was losing its gas to space, which may render it uninhabitable. More in-depth observations may confirm the 10 | NewScientist | 26 November 2016
rate at which its atmosphere is leaking, and may identify specific molecules. The super-Earths
Either K2-18b or K2-3d, two planets discovered in the second phase of the Kepler mission, might have the whole package. Both orbit bright nearby stars that could reveal their atmospheres, and are at the right distances for both to host liquid water. The only obviously weird thing about these planets is their size. Both are super-Earths, wider than our planet. K2-3d is 1.6 times larger than Earth and likely rocky; K2-18b is 2.3 times larger and may have a thick, puffy atmosphere. Hubble will spend about five days over the next year studying these planets. Both might have hydrogen-rich atmospheres, or be completely blanketed by clouds, says Björn Benneke at the California Institute of Technology. But if the molecular signature of water, methane or ammonia shows up on either planet, it would mean we have a real chance to look for biosignatures. “If we found any signal, then we would hit this pair extremely hard with James Webb,” Benneke says. “There’s no doubt about that.”
nasa
Joshua Sokol
–Scouting for life– The TRIPLETS
One ultra-cool dwarf star, TRAPPIST-1, offers a discount rate: three planet siblings, all within about 20 per cent Earth’s size. Of those three planets, announced in May 2016, one or two might be water-friendly. Later this year, the team that discovered the triplets used Hubble to find that two of the planets lack big, puffy atmospheres, which suggests they are rocky. This December and January, they will use Hubble
Look to the stars A good world is hard to find – but that’s only half the battle. “Context is everything in many aspects of life,” says Evgenya Shkolnik at Arizona State University. “In the case of exoplanets, that context is the star.” Shkolnik is leading an effort to spend about a week using Hubble to observe small, cool M dwarf stars to understand effects that could hide life on their planets, or give a signal that looks like life but isn’t.
Habitable-zone planets around M dwarfs are subject to erratic bursts of ultraviolet radiation, which would destroy biosignature molecules in an atmosphere. UV radiation can also break up water, which could increase the concentration of oxygen even with no living organisms responsible. Ultraviolet radiation is harmful to life on its own, too. So the star’s temperament will play a key part in deciding whether to study a planet.
again to measure how thick the atmospheres are, says Julien de Wit at the Massachusetts Institute of Technology. Their findings will help them plan a proposal to study the triplets during JWST’s first year. The next-door neighbour
You couldn’t find a closer potentially habitable planet than Proxima b – an Earth-sized world around the next star over – if you tried. But Proxima b has a downside: it never transits in front of its star, making it far harder to study. All is not lost. We could look for the planet’s phases: minute changes in the system as the planet orbits its star and points different faces at Earth. If JWST saw heat speeding from one side of the planet to the other, it would show that the planet has an atmosphere in the first place, says Laura Kreidberg at Harvard University. Or with a few months of solid staring by JWST we might be able to detect ozone, a possible biosignature, in its atmosphere. n