Although we’ve heard a lot in recent years about the discovery of exoplanets with the potential to be habitable or Earth-like, the detection of a perfect analogue of our world hasn’t happened yet. But we are getting closer and closer, as shown by a new study conducted mainly by Brazilian researchers.
The work, whose first author is Yuri Netto, from the IAG-USP (Institute of Astronomy, Geophysics and Atmospheric Sciences of the University of São Paulo), was accepted for publication in the Astronomical Journal. It aimed to test the accuracy level of Espresso, a new spectrograph installed in the VLT, a telescope belonging to the ESO (Southern European Observatory) in Chile. This instrument was designed to search for terrestrial analogues, that is, Earth-mass exoplanets in an Earth-like orbit, orbiting a star like the Sun.
To do this, by the method of measuring radial velocities (the famous detection of the wobble of stars as planets revolve around them and attract them to and fro), one would need to achieve an accuracy of 10 cm/s. (Think about it: measuring a movement of a mere ten centimeters every second of a star located light-years away.)
The Espresso’s predecessor spectrograph, the Harps, installed in La Silla, also in Chile, has an accuracy of 1 m/s. In other words, the ambition is to improve the available measures tenfold. And by then he’s almost there.
The group conducted 24 observations of the HIP 11915 star, spread over 60 nights. The star, located 175 light-years from here in the constellation of Whale, was chosen because it is a solar twin that has a planet analogous to Jupiter, discovered with the Harps, also by Brazilians, in 2015, and is now in a phase of low activity. stellar.
After observations and post-processing (intended to “clean up” the noise, mainly produced by the star’s activity), the researchers obtained reliable measurements of radial velocity averaging 24 cm/s. This therefore established the minimum qualification for Espresso – at worst, accuracy of about 20 cm/s. It may sound frustrating, but it’s a great result.
The expectation is that the more observations made, the greater the accuracy achieved. And 60 nights, as in this initial study, is a very restricted period for the search for exoplanets: after all, to confirm a detection, the planet needs to complete at least one full circle around the star, which in the case of an analogue Perfect Earth would require 360 days.
With more observations and processing improvements, it is quite possible that Espresso will reach the coveted sensitivity range of 10 cm/s. And the HIP 11915 star, researchers remind us, would be a great place to keep looking. After all, as far as we know, the similarity to the Solar System is remarkable. Maybe that’s where we’ll find the first perfect analogue of Earth?
This column is published on Mondays in Folha Corrida.
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