In the last few decades, we’ve gone from zero known exoplanets to more than 4,000. Scientists have even found a few orbiting the closest stars to our own. A project called Near Earths in the Alpha Center Region (NEAR) has just spotted tantalizing signals that could point to a planet in the habitable zone of Alpha Centauri, which is a mere 4.37 light years away. That’s right next door in astronomical terms.
Our solar system is pretty simple — one star, and a whole mess of planets orbiting it. Centauri is a bit different and consists of three stars. For starters, there’s Proxima Centauri, which is 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 sun-like members of the system would be even more interesting, and there might be one.
The NEAR team used the European Southern Observatory’s Very Large Telescope (VLT) in Chile to check out our celestial neighbors. The project pushed for an upgrade to the VLT that included an instrument called a thermal chronograph. This allows astronomers to block out the light from a star to make faint thermal signals easier to detect. After more than 100 hours of cumulative observations, the researchers pinned down what appears to be a thermal signal in the habitable zone of Alpha Centauri A. No one is willing to say this is definitely a planet, but it could be.
The exoplanet, if it exists, is in the habitable zone of the star. That means it could have liquid water, and therefore, the possibility of life. Early analysis suggests the exoplanet is a bit smaller than Neptune. That could mean it’s a small gas giant or possibly a very large rocky planet. If it’s a gas giant, life as we know it is off the table. However, there could be moons orbiting the world that have both liquid water and a solid surface on which life could evolve.
There’s still more work to do before we can add another exoplanet to the list. The team notes the thermal signal could have other explanations, like a region of unusually hot cosmic dust or a warmer, distant object in the background. We’ll need more sophisticated instruments to know for sure. Luckily, the James Webb Space Telescope might finally launch later this year. Its infrared instruments should be able to determine if the thermal signature around Alpha Centauri A is a planet or just background noise.
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