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
- Sorry Folks: Signal From Nearest Star Not Alien Civilization, Scientists Sayon January 26, 2021 at 1:32 pm
Breakthrough Listen, a project dedicated to the hunt for signals from extraterrestrial life, announced the discovery of a mysterious radio beam emanating from Proxima Centauri, the star system closest ...
- E.T. signal from Proxima Centauri? A conversation with Breakthrough Initiatives' Pete Wordenon January 25, 2021 at 4:28 am
Space.com recently talked with Breakthrough Initiatives executive director Pete Worden about a signal coming from the vicinity of Proxima Centauri, and about the search for alien life more generally.
- Mysterious Alien Signals Detected From The Closest Solar Systemon January 21, 2021 at 10:01 pm
Scientists recently identified a strange alien signal from the nearby solar system, which can signal a developed civilisation. Read the details here ...
- A $100 Million Message From Aliens In The Star System Next-Door? What We Know About The Mysterious ‘BLC1’ Radio Signalon January 21, 2021 at 7:00 pm
What’s really going on with that signal from Proxima Centauri and how likely it is that there’s a technological civilization on a planet around the star next door.
- Red Dwarf Starlight Used to Grow Photosynthesizing Bacteriaon January 21, 2021 at 8:22 am
Extremophiles grown under a starlight simulator suggest that exoplanets orbiting red dwarf stars may have conditions ripe for photosynthesis, say researchers.
- Did Earth Receive a Radio Transmission From Proxima Centauri?on January 20, 2021 at 12:49 pm
A team of astronomers is working to analyze an unusual radio signal detected early in 2019 with characteristics more typical of an artificial broadcast than a natural source.
- Why The Recent Signal That Appeared to Come From Proxima Centauri Almost Certainly Didn'ton January 18, 2021 at 8:58 am
Astronomers have now calculated the likelihood that the signal came from another advanced civilization — and the numbers don't look good.
- Astronomers Discover Mysterious Radio Signal From Proxima Centaurion January 14, 2021 at 11:01 pm
As part of the Search for Extraterrestrial Intelligence (SETI) program, astronomers working on the Breakthrough Listen project scan for radio signals that could come from some non ...
- Astronomers Are Keeping a Close Watch on the Next Star Overon January 11, 2021 at 9:41 am
Last month, as 2020 drew to a close and we on Earth completed one of our strangest orbits around the sun, news broke that astronomers had picked up a mysterious signal from another star. Astronomers ...
- Astro Bob: Was the Proxima Centauri signal sent by aliens?on January 10, 2021 at 5:48 pm
This is an artist's conception of Proxima Centauri b, a planet slightly bigger than the Earth, orbiting the red dwarf star Proxima Centauri. Proxima and the Alpha Centauri binary are seen in the ...
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