In the last few decades, we have risen from zero known exoplanets to more than 4,000. Scientists have even found a few that orbit the stars closest to our own. A project called Near Earths in the Alpha Center Region (NEAR) has just noticed seductive signals that could point to a planet in the Alpha Centauri habitable zone, which is only 4.37 light-years away. It’s astronomical next door.
Our solar system is fairly simple – one star and a whole litter of planets orbiting it. Centauri is a bit different and consists of three stars. To begin with, there is Proxima Centauri, a red dwarf that sits a fraction of a light year closer to Earth. Proxima orbits Alpha Centauri A and B, which are larger, warmer stars like the sun. We know of at least two exoplanets orbiting Proxima Centauri, but a world around the sunny members of the system will be even more interesting, and there may be one.
The NEAR team used the Very Southern Telescope (VLT) of the European Southern Observatory (VLT) in Chile to look at our heavenly neighbors. The project called for an upgrade of the VLT, which includes a tool called a thermal chronograph. This allows astronomers to block the light of a star to more easily detect faint thermal signals. After more than 100 hours of cumulative observations, the researchers determined a thermal signal in the habitable zone of Alpha Centauri A. No one is willing to say that it definitely a planet, but it can be.
The possible exoplanet is marked here as C1.
The exoplanet, if it exists, is in the habitable zone of the star. This means that it can have liquid water, and therefore the possibility of life. Early analysis suggests that the exoplanet is slightly smaller than Neptune. This could mean that it is a small gas giant or possibly a very large rocky planet. If it’s a host giant, life as we know it is off the table. However, there may be moons orbiting the world that have liquid water and a solid surface on which life can develop.
There is still more work to be done before we can add another exoplanet to the list. The team notes that the thermal signal may have other explanations, such as an area of unusually hot cosmic dust or a warmer, distant object in the background. We will need more sophisticated tools to know for sure. Fortunately, the James Webb Space Telescope can finally launch later this year. Its infrared instruments must be able to determine if the thermal signature around Alpha Centauri A is a planet or just background noise.
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