A new study in which scientists present a new way to track down habitable planets cautiously suggests yes!
A few years ago, the nearest star system – Alpha Centauri – discovered a planet. It circles around one of the three stars of Alpha Centauri: Proxima Centauri. It seems likely that the other two stars in the system – Alpha Centauri A and B – also have (habitable) planets, but hard evidence for this is lacking.
Hint
However, that may soon change. Scientists have a new technique developed to directly observe potentially habitable planets around nearby stars. And an application of that technique results in the cautious indication that in the habitable zone around Alpha Centauri A there is a planet that is somewhere between Neptune and Saturn in size.
“We’re not so sure yet to say we’ve discovered a planet around Alpha Centauri,” emphasizes researcher Kevin Wagner. “But there is a signal that – after verification – could be a planet.” That signal is referred to by the researchers as C1.
Direct observations
The signal has surfaced during direct observations. And that is quite special. Only a few dozen exoplanets have been directly observed to date. And in most cases these are large exoplanets (larger than Jupiter) at a great distance from their (very young) parent star. The latter is easy to explain; smaller planets close to the parent star are masked by the bright light of the parent star. “Compare it to portraying a firefly next to a lighthouse,” astronomer Frans Snik explained earlier Scientias.nl from. “And then mapping an exoplanet close to the parent star is a factor 1000 more difficult.”
New method
And yet, researchers have now succeeded in developing a method that makes it possible to observe smaller planets in the habitable zone (i.e. fairly close to the parent star). First of all, they focused on slightly different infrared wavelengths, Wagner explains. Most directly observed exoplanets have been spotted on images in near infrared (infrared light with a wavelength of up to 10 micrometers). Only seldom was the medium infrared wavelengths searched for. “There is a good reason for this, because the Earth itself shines very brightly at those wavelengths. Infrared radiation from the air, the camera and the telescope itself, in fact, drown out the signals sought. Still, there is good reason to focus on these wavelengths. Because at these wavelengths, Earth-like planets in the habitable zone around sun-like stars are the brightest. ”
The researchers used the Very Large Telescope to observe Alpha Centauri. They used a second, so-called adaptive telescope mirror. This corrects the disturbances that light undergoes as it travels through the Earth’s atmosphere, thus improving image quality. In addition, a coronagraph optimized for the middle infrared light spectrum was used. This instrument blocks the starlight, revealing any nearby objects that would otherwise completely merge with that sunlight. Finally, the researchers developed another technique that made it possible to study the environment of Alpha Centauri A and B alternately. In turn – every tenth of a second – the light from one star and then another is blocked. “That allows us to study each star for half the time and – more importantly – it allows us to extract one frame from the next and so everything that is really just noise from the camera and camera. the telescope. ” And with the unwanted starlight and noise gone, the much fainter signals from potential candidate planets in the habitable zone can become visible.
C1
The researchers observed Alpha Centauri A and B like this for nearly 100 hours. It results in more than 5 million images and 7 terabytes of data. And so the light source C1, which could later turn out to be a planet. “There is one light source that resembles a planet that we cannot explain with our systematic error corrections.”
Whether C1 really is a planet will have to become clear in the future. The researchers want to take a closer look at the system in a few years anyway. They hope to find the exoplanet again – albeit at a different location in the star system. Follow-up observations using other methods to detect exoplanets may also provide more clarity about the alleged planet’s existence in the near future.
In the coming years, researchers also expect to be able to observe many more (potentially habitable) planets directly. The next generation of telescopes – such as the Extremely Large Telescope and the Giant Magellan Telescope – is very suitable for that. For example, the planets can focus on Sirius – the brightest star in the night sky. Or Tau Ceti, the closest single star, which has five never-before-seen planets.
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