A new phase in the search for life elsewhere is about to begin
“WE’VE been wondering what planet we’re first going to look for life on. Now we know.” Rory Barnes, of the University of Washington, puts it nicely. Proxima Centauri, the star closest to the sun, has a planet. That planet weighs more or less the same as Earth and is therefore presumably rocky. And it orbits within its parent star’s habitable zone—meaning that its surface temperature is likely to be between 0°C and 100°C, the freezing and boiling points of water at sea level on Earth.
A prize discovery, then, for astrobiologists such as Dr Barnes. And the discoverers are a transnational team of astronomers who have been using telescopes at the European Southern Observatory (ESO) in the Atacama desert, in Chile, for planet-hunting. Though they have not seen the new planet directly (they have inferred its existence from its effect on its parent star’s light), their paper in Naturedescribes what they have been able to deduce about it.
Proxima Centauri b, as it is known, probably weighs between 1.3 and three times as much as Earth and orbits its parent star once every 11 days. This puts its distance from Proxima Centauri itself at 7m kilometres, which is less than a twentieth of the distance between Earth and the sun. But because Proxima is a red dwarf, and thus much cooler than the sun, the newly discovered planet will experience a similar temperature to Earth’s. It is not the only Earth-sized extrasolar planet known to orbit in a star’s habitable zone. There are about a dozen others. But it is the closest to Earth—so close, at four light-years, that it is merely outrageous, not utterly absurd, to believe a spaceship (admittedly a tiny one) might actually be sent to visit it. Before this happens, though, it will be subjected to intense scrutiny from Earth itself.
Eyeball to eyeball
That scrutiny will probably be led by ESO. The data which led to Proxima Centauri b’s discovery came from the observatory’s 3.6 metre telescope at La Silla, in Chile. But ESO is also building a much bigger device, the 39-metre European Extremely Large Telescope (E-ELT), at another site in Chile. Since the late 2000s Markus Kasper has led a team at ESO which is designing a specialised planet-spotting instrument, the Exoplanet Imaging Camera and Spectrograph (EPICS), to fit on this telescope. Dr Kasper’s camera has a price tag of €50m, and there have always been questions in the past about whether it is worth the money. But EPICS stands a better chance of producing actual pictures of Proxima Centauri b than any other camera in the world (or off it). Its future can now scarcely be in doubt.
The problem for astronomers trying to catch a glimpse of Proxima Centauri b is that, though close to the Earth by interstellar standards, it is even closer to its parent star by more or less every other standard short of that of walking down the road to the chemist. Seen from Earth, star and planet are 35 thousandths of an arc second apart (an arc second is a 3,600th of a degree). Producing a picture that separates the two objects thus requires a telescope with a resolution good enough to distinguish between the left and right headlights of an oncoming car in Denver from the distance of Berlin.
Things get worse. Dim as it is, Proxima Centauri (pictured above, as seen by the Hubble space telescope) is still more than 10m times brighter than its planet is expected to be. It is as though one of those headlights in Denver was actually the open door to a furnace, while the other was a tea light. This is what makes the E-ELT and EPICS crucial. EPICS contains a coronagraph—a tiny shield that blocks out a star’s light so that adjacent planets can be seen. Unfortunately, a coronagraph reduces a telescope’s resolution, meaning you need an even bigger one to see the target in the first place. To observe Proxima Centauri b using a coronagraph, and looking in the infrared wavelengths that are likely to provide the best information about its atmosphere, you need a telescope at least 20 metres across; 30 metres would be better.
Two other large telescopes besides E-ELT, of 27 metres and 30 metres diameter, are under construction and planned. But some suggest the first of these, the Giant Magellan Telescope, also in Chile, is not well suited to the use of a coronagraph, and the second, the Thirty Metre Telescope, is planned at the moment for Hawaii, which is in the northern hemisphere. Proxima Centauri is in the southern skies, and therefore not so easy to study from north of the equator.
There may, just possibly, be a short cut.
The Latest on: Proxima Centauri
via Google News
The Latest on: Proxima Centauri
- There Might Be a Second Super-Earth Orbiting the Star Closest to Our Sunon January 22, 2020 at 10:39 am
Back in 2016, the world was left starstruck after scientists stumbled upon a super-earth orbiting the Proxima Centauri, the star closest to the sun, only 4.2 light-years away from our Earth. Now, they ...
- Astronomers Announce Proxima Centauri's Second Planet, And It's Perfect For Direct Imagingon January 21, 2020 at 11:36 pm
The closest star to our own doesn't just host one rocky planet, but a second, larger 'super-Earth' much farther out.
- Neighboring Star Proxima Centauri May Host Second Planeton January 20, 2020 at 8:04 am
Scientists detected a possible second planet orbiting red dwarf Proxima Centauri, the closest known star to our galaxy. New observations suggest the presence of what is described as a “low-mass ...
- The nearest star to our sun, Proxima Centauri, may host a second planeton January 19, 2020 at 8:00 am
An artist’s impression of the Proxima Centauri planetary system, with exoplanet Proxima c on the right. Lorenzo Santinelli, CC BY-SA Astronomers have discovered what appears to be a second exoplanet ...
- A second planet may orbit Proxima Centaurion January 17, 2020 at 2:49 pm
The planet orbiting the star closest to the sun may have a neighbor. Proxima Centauri, a dim red star just 4.2 light-years away, is already known to host one potentially habitable planet, Proxima b, ...
- Scientists discovered a new ‘super-Earth,’ and want to know if it could sustain lifeon January 16, 2020 at 8:47 pm
Also, flares from the Proxima Centauri red dwarf that this planet orbits might have already wrecked the planet’s atmosphere. Proxima c is at least 6 times bigger than Earth itself and as such is ...
- Neighboring star Proxima Centauri may be hosting a second planeton January 16, 2020 at 1:01 pm
An exoplanet couldn't get any closer, and now it looks like there could be a pair just around the cosmic corner. The closer scientists look, the more interesting Proxima Centauri gets. It's always ...
- Possible discovery of a new super-Earth orbiting Proxima Centaurion January 16, 2020 at 4:32 am
Astronomers have discovered another candidate exoplanet orbiting our neighbor Proxima Centauri. A paper announcing these results was just published in the journal Science Advances. If confirmed ...
- Proxima C: New Super Earth Likely The Second Alien Planet At Proxima Centaurion January 16, 2020 at 3:31 am
A study by astronomers suggests that changes in the activity of the Proxima Centauri are likely from a second planet that it has – the Proxima c.
- The Curious Case of Proxima Con January 15, 2020 at 5:36 pm
An artist’s speculative, not-to-scale rendering of the Proxima Centauri planetary system. The planetary candidate Proxima c and an accompanying ring system (at right) looms at the inner edge of a ...
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