Brazilians discover two planets: a super-Neptune and a super-Earth
Scientists have discovered two new planets around a star very similar to the Sun. The super-Neptune and super-Earth, orbiting the star HIP 68468, are among the first planets discovered by teams led by Brazilian astronomers after the discovery of a Jupiter-like planet announced in 2015.
According to astronomer Jorge Melendez, professor of the Institute of Astronomy, Geophysics and Atmospheric Sciences of the University of Sao Paulo and leader of the research, one of the main goals of the study was to compare our Solar System with other planetary systems. The discovery was published by the journal Astronomy & Astrophysics.
What they found around the HIP 68468 star was a planetary system quite different from ours. This is because, although the masses of the newly discovered planets are comparable to those of Earth and Neptune, they orbit at a very close distance from their star, which suggests that the planets might have migrated from an external region to the innermost part of this planetary system.
The super-Neptune, called HIP 68468c, has a mass 50 percent larger than that of planet Neptune. But while our Neptune is far from the Sun (30 times the Earth-Sun distance), the orbit of the new planet equals only 70% of the Earth-Sun distance.
The super-Earth, called HIP 68468b, has a mass equivalent to three times that of the Earth, and its orbit equals only 3% of the Earth-Sun distance.
The star HIP 68468, which is 6 billion years old, is 300 light-years away from Earth.
Planets might be swallowed
In addition to finding that these planets may have migrated from outer regions to inner regions of the system, there's also evidence that HIP 68468 star may have "swallowed" a planet. One of the signs is the excess of lithium found in the star. Lithium is the most abundant element in the planets, but such a quantity is very rare in stars.
And the newly discovered planets are not immune to their star's "appetite." "Especially the planet that is nearer [the super-Earth] can be easily swallowed," says Melendez. "Even if its orbit is stable, the planet is so close to its star that it will be destroyed anyway. As stars evolve, they keep increasing in size. If this star increases its size just a bit, it's enough to destroy it. "
Comparing with the Solar System
According to Melendez, observing a planetary system in which there is a migration of the planets to the innermost area helps understanding the dynamics of our Solar System.
"If the planets migrated in the Solar System, our planet would be destabilized, with a chaotic orbit and a risk of colliding with another planet and being ejected from the Solar System or towards the Sun," says the astronomer.
One of the scientists' hypothesis to explain why this does not happen is that Jupiter would act as a barrier that would not allow the giant planets of the Solar System to migrate to the innermost regions. In the planetary system discovered, there is no planet equivalent to Jupiter.
"This reinforces the important role that Jupiter plays in maintaining the planetary architecture of the Solar System, with rocky planets inside and giant on the outside," Melendez concludes.
European Southern Observatory
The discovery of the two new planets occurred thanks to observations made in a sophisticated instrument coupled with the telescope of the European Southern Observatory (ESO), which lies in the Atacama Desert in Chile.
Melendez explains that it is not possible to make a direct observation of the planets. Instead, the spectrograph is able to detect the stars' very subtle movements when a planet rotates around it due to gravity. Just as the star pulls the planets toward it, the planets also have similar effect on their star, causing it to make small movements. It is from these movements that the existence of new planets is inferred.
These observations were made during 43 nights between 2012 and 2016.
"The long-term project is to look for an Earth-like planet. This will be possible very soon because there is an instrument at ESO that will have enough technology to be able to detect this type of planet. Currently we're only able to detect planets with a mass of 2 or 3 times that of the Earth," says the astronomer.
Melendez points out that Brazil's accession to ESO, which is the largest consortium of astronomical research in the world, has been pending since 2010, when the agreement was signed by the then Brazilian Minister of Science and Technology, Sergio Rezende.
By joining ESO, Brazil grant the opportunity for Brazilian scientists to use telescopes and state-of-the-art observation instruments installed in northern Chile. The consortium is responsible for the E-ELT megatelescope project (Acronym for "European Extremely Large Telescope"), which should be the largest telescope in the world, with a mirror 39 meters in diameter.
The team that discovered the planets also has researchers from the National Laboratory of Astrophysics (LNA), Federal University of Rio Grande do Sul (UFRGS), University of Chicago, University of Texas at Austin, National University of Australia, University of Göttingen, China's Academy of Science, Max Planck Astronomy Institute and Space Telescope Science Institute.
Original article published in Portuguese in G1.
