Scientists have recently discovered planet, which they have named Proxima d. The exoplanet Proxima d orbits a star called Proxima Centauri. The discovery is significant because it is ‘one of the smallest exoplanets ever detected, and the smallest detected by observing the exoplanet’s gravitational effect on its star.’
In the search for habitable planets, scientists have become particularly interested in Proxima Centauri is a small red dwarf star which is the closest star to the Sun.
Michelle Starr writing for sciencealert.com states the discovery of Proxima d ‘marks the third exoplanet found orbiting Proxima Centauri‘
Why finding new planets on Proxima Centauri the star closest to our son is significant
Planets that orbit around other stars are called exoplanets.
From observing the fate of other exoplanets, our scientists know that one day our planet may not be habitable anymore.
It’s not likely with the technology available at this time that humans will reach planets orbiting Proxima Centauri anytime soon. Proxima Centauri is about 4.2 light-years away. Mars is 0.000024155306893301653 light-years away, or about 12.7 light minutes on average away from the sun.
To put the travel distance in some context, it takes six months to send a Rover vehicle by rocket from earth to Mars, which is only 12.7 light minutes away from our sun. There is no practical way for humanity to reach planets over four light with current technology years out anytime soon!
Is Proxima d habitable?
Proxima d orbits Proxima Centauri every 5.12 days, at a distance of about four million kilometres. By comparison Mercury’s orbit is 63.795 million kilometres from the Sun.
On Mercury, temperatures are extreme. ‘During the day, temperatures on the surface can reach 800 degrees Fahrenheit (430 degrees Celsius). Because the planet has no atmosphere to retain that heat, nighttime temperatures on the surface can drop to minus 290 degrees Fahrenheit (minus 180 degrees Celsius).’
Given that Proxima d is about a tenth of the distance from its own star, compared to Mercury and our sun, ‘That sadly means that it is too close to the star to be hospitable to life as we know it; even a cool red dwarf would give off too much heat to support liquid water on the surface of an exoplanet so close.’
Even if it was later discovered that atmospheric conditions of a red dwarf star such as Proxima Centauri later became cooler (in a billion years, it might not be so hot), the exoplanet Proxima d is about a quarter of the size of planet earth, so not necessarily the best candidate to migrate the Earth’s population to.
What else is near Proxima Centauri?
Another planet orbiting Proxima Centauri is called Proxima c, which is approximately six times the mass of Earth, and on a 5.2-year orbit; too cold to be habitable.
Proxima b which also orbits Proxima Centauri is the best bet for habitability, ‘Proxima b is a 1.3 Earth mass planet orbiting its star at about 1/20th of the Sun-Earth distance, which places it well within the so-called Habitable (Goldilocks) Zone. It receives an amount of energy from its central star that is about 2/3 of that received by the Earth from the Sun.’ However the exoplanet Proxima b is currently considered to have ’60 times more high-energy radiation than the Earth’ and is speculated what may happen with liquid in the planet’s atmosphere.
How was Proxima d discovered?
When scientists were observing Proxima Centauri and discovered Proxima b in 2020 using radial velocity methods, ‘there seemed to be something orbiting the star on a five-day period. The signal was so faint, however, that more observations were required to try to work out if it was an external influence or if the fluctuations in light were emanating from internal processes in the star itself.’
This year the team studying Proxima b determined an other exoplanet which they named Proxima d, was causing the Proxima Centauri to move back and forth at just 40 centimeters (16 inches) per second.
Radial velocity technique may reveal thousands of other exoplanets
The scientists who discovered Proxima d using a unique radial velocity technique say, “It shows that the radial velocity technique has the potential to unveil a population of light planets, like our own, that are expected to be the most abundant in our galaxy and that can potentially host life as we know it.”
Michelle Starr writes, ‘Just 36 exoplanets of the 32,073 recorded on the Exoplanet Archive are less massive than Earth.’ The recent discovery of Proxima d using radial velocity technique may suggest that the lack of smaller exoplanets on the record so far ‘could simply be a result of our existing inability to reliably detect them – and that finding them is simply going to be a matter of time and technology.’
Proxima Centauri by ESO/M. Kornmesser under CC BY 4.0
