Cienciaes.com: Radio signals from Próxima Centauri. We speak with Miguel Pérez Torres.

2021-01-26 15:49:54

Those who observe the firmament from the Southern Hemisphere can see, very close to the Southern Cross, the constellation Centaurus, whose brightest star, Alpha Centauri, is actually a triple set containing the stars closest to the Sun. The two The first, alpha Centauri A and B, are the brightest and revolve around each other at distances ranging between those separating the Sun from Saturn and Pluto. The third, known as Alpha Centauri C or Proxima Centauri, is much further away from the other two, but it is the closest to us.

In 2016 it was discovered that a planet with a similar size to Earth orbits around Proxima Centauri, identified as Proxima Centauri bo “Proxima b”. Despite its closeness to the star, the radius of its orbit is one tenth of the distance between Mercury and the Sun, since Proxima is a red dwarf, much smaller and cooler than the Sun, the planet wanders through the region which is known as the “habitable zone”, that is to say, a zone in which, at least in theory, liquid water could exist on the surface, if the conditions were suitable. And we already know that liquid water is an essential ingredient for life.

But Proxima Centauri is a star that suffers from great magnetic activity, with spectacular increases in brightness, changes that are not very favorable for the development and maintenance of life in it. However, the powerful magnetic fields interact with the planet and, as a result of this interaction, a radio signal is generated that has been detected from Earth by the team led by our guest, Miguel Pérez-Torres, a researcher at the Institute of Astrophysics of Andalusia.

The generation of radio waves due to the magnetic interaction between two bodies had already been detected a couple of decades ago in the Solar System. Jupiter has a very strong magnetic field that interacts with its satellite Io and generates a radio emission similar to that produced during terrestrial auroras. These observations made think Miguel A. Perez Torres and the rest of the researchers participating in the study that perhaps the radio signal generated by the interaction between Proxima Centauri and the planet Proxima b could be detected.

Determined to study that possibility, the team used the Australia Telescope Compact Array (ATCA) to observe Proxima Centaruri between April 12 and 29, 2017 at frequencies that according to theoretical calculations should be generated during star-planet interaction.

Proxima b revolves around the star in such a way that it makes one complete revolution every 11.2 days, that is the duration of its particular “year”. Thus, the researchers were observing the set for a period equivalent to a year and a half in the chronology of the planet.

The campaign was successful because it allowed the detection of radio emissions in the low-frequency band of 1.6 GHz that shows a variation that coincides with the orbital period of the planet Proxima b around the star Proxima Centauri. This emission is of greater intensity when the planet is close to the squares, that is to say, when, seen from Earth, the planet is forming a right angle with our direction of observation, as it happens with Venus when we see it in the positions farthest from the Sun at sunrise or sunset.

The researchers also observed two flares lasting a few minutes and one long-lasting explosion (about three days) whose peaks occurred near the quadratures.

This type of observation opens a new path for the investigation of planetary systems around magnetically active stars, which adds to existing methods. Since the detection of the first extrasolar planet around a solar-type star, in 1995, thousands of planets have already been discovered in our galaxy, an investigation that will bear new fruit thanks to radio observations such as the one carried out by Miguel A. Perez Torres and his colleagues.

I invite you to listen to Miguel A. Perez Torresresearcher in the Department of Radio Astronomy and Galactic Structure of the Institute of Astrophysics of Andalusia (IAA–CSICGranada, Spain) of the CSIC (Superior Council of Scientific Investigations).

REFERENCE
M. Pérez-Torres, JF Gómez et al. Monitoring the radio emission of Proxima Centauri. Astronomy & Astrophysics. Volume 645 (January 2021)