Proxima Centauri is the closest star to our own Sun, and for the last 4 years there have been several hints pointing to an exoplanet orbiting it. Not just any planet, an Earth like planet. Most notably observations made with the HARPS (High Accuracy Radial Velocity Planet Searcher) instrument. A specialized planet hunter mounted to a 3.6m telescope in Chile.
The instrument has found hundreds of exoplanets over its 17 year lifespan, but only a handful of them being earth like ones. This is because larger Jupiter-like planets have a much stronger gravitational effect on their host star than smaller and lighter earth like planets. In fact, this planet was only found due to its proximity to Earth.
However, the data was only good enough to suggest that Proxima b existed, but it might as well have been noise or a bad fit to the data. A follow up was needed. This is where the ESPRESSO (Echelle SPectrograph for Rocky Exoplanets and Stable Spectroscopic Observations) instrument comes in. Mounted on world’s biggest telescope, this instrument uses very high resolution spectra to measure radial velocities down to a precision of 26cm/s.
The team behind it, led by Alejandro Suarez Mascareño, observed the planet 63 individual times during 2019. From the data they could independently verify the planet and constrain its mass and orbital period to 1.17 the mass of the earth and 11.2 days respectively.
The precision at which this was done is unheard of and made possible due to the proximity of the target and the state of the art instrumentation. The article also mentions a 2nd smaller signal that could potentially be a 2nd planet in the system. Orbiting at a 5.15 days and with a minimum mass of 0.29 earth masses. This planet is in no way confirmed and will need a follow-up of its own. If it gets confirmed, it will be one of the smallest planets found to date.
Proxima b conditions
Proxima b receives about as much sunlight as the Earth due to its host star being much less bright. This means that this planet could potentially harbor life. The only downside to this is that the star has regular X-ray bursts where it emits more than 400 times the radiation that our planet receives. This means that without a thick atmosphere the planet will most likely be sterile.
Whether or not this is the case remains an open questions, one that will hopefully be answered by the next generation of instrumentation that is already under development.
For those who would like to visit Proxima b, unfortunately it is still 4.2 light-years away from us, which would take thousands of years to get to with our current technology.