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A solar system like ours
Astronomers have discovered more than 4,000 exoplanets, worlds orbiting distant stars in our Milky Way galaxy. Many reside in planetary systems very different from ours. But, on August 5, 2021, astronomers said they had found a distant planetary system that has intriguing similarities to our sun’s inner solar system. One of the planets has about half the mass of Venus, Earth’s neighboring planet. Another might have oceans. And there could be yet another rocky world within the habitable zone of this system.
These astronomers used the European Southern Observatory’s very large telescope to make their observations. Researchers have published a new article detailing their findings in the peer-reviewed journal Astronomy & Astrophysics August 3.
It has 4 or 5 rocky planets
The host star, L 98-59, is only 35 light years away. He has at least four confirmed rocky planets and possibly a fifth. It is similar to the rocky worlds of our solar system (Mercury, Venus, Earth, Mars). However, in the L 98-59 system, the distance scales are different. And, by the way, all known planets from L 98-59 are classified as super-Earths. This means that they are rocky worlds larger than Earth, but smaller than Neptune.
A planet is half the mass of Venus
The innermost planet, L 98-59b, has only about half the mass of Venus. It is the lightest exoplanet found to date using the radial velocity method. This technique measures the tiny “oscillation” of a star caused by the gravitational tug of invisible orbiting planets. L 98-59b is probably quite dry. But it could contain small amounts of water, the researchers say. Its mass is only 1.01 times that of the Earth, so very, very similar. It orbits its star in just 2.3 days!
The second planet is labeled L 98-59c. Its mass is 2.42 times that of the Earth and it orbits in 2.7 days.
An oceanic world?
The third planet is where things get really interesting. It is labeled L 98-59d. Researchers have calculated that up to 30% of the mass of this world is probably water. If so, it’s an ocean world. It is not yet clear how similar L 98-59d might be to Earth in terms of its oceans. But it tickles the mind. Is the water of this world on the surface? Or is it mostly underground? This planet has a mass 2.31 times that of Earth. It orbits its star in 7.5 days.
The most recent planet known in this system is the fourth planet, L 98-59th. It has a mass 3.06 times that of the Earth and orbits its star in 12.796 days.
So you can see that all of these four worlds are really accelerating around their star!
A rocky world in a habitable zone?
But there is more. There is new evidence for a fifth planet, labeled L 98-59f. Although still unconfirmed, this fifth planet is estimated to be 2.56 times the mass of Earth. It orbits in 23.15 days. What a slowpoke, right? The point is, like all the other worlds in this star system, L 98-59f is still quite close to its star. But here’s something we haven’t told you yet. The star L 98-59 is a small, cold red dwarf star, one of the most common kinds of stars in our Milky Way galaxy. And that means that the orbits of its fifth planet are in the middle of the star’s habitable zone. The living area – sometimes referred to as the Goldilocks area – is neither too hot nor too cool. It is the region around a star where temperatures are ideal for liquid water to exist on the surface of rocky planets.
The lead author of this study, astronomer Olivier Demangeon from the University of Porto in Portugal, commented:
We have indications of the presence of a terrestrial planet in the habitable zone of this system.
Co-author María Rosa Zapatero Osorio added:
The planet in the habitable zone may have an atmosphere that could protect and support life.
The role of ESPRESSO
How did astronomers make these observations? They used the ESPRESSO instrument (Echelle SPectrograph for Rocky Exoplanets and Stable Spectroscopic Observations) on the VLT to study L 98-59. ESPRESSO was essential, as Zapatero Osorio explains:
Without the precision and stability provided by ESPRESSO, this measurement would not have been possible. It is a step forward in our ability to measure the masses of the smallest planets beyond the solar system.
NASA’s Transiting Exoplanet Survey (TESS) satellite found the first three planets in the system in 2019. It found them using the proven transit method, where a planet is detected as it passes in front of its star as seen from Earth . But ESPRESSO was able to find one or two other planets a little further from the star. It also allowed scientists to measure the masses and radii of the first three planets for the first time. Demangeon said:
If we want to know what a planet is made of, the minimum we need is its mass and radius.
So what’s the next step?
NASA’s upcoming James Webb Space Telescope and ESO’s next Extremely Large Telescope will both be ideal for studying planets in the L 98-59 system. According to Zapatero Osorio:
The Extremely Large Telescope’s HIRES instrument may have the power to study the atmosphere of some of the planets in the L 98-59 system, complementing the James Webb Space Telescope from the ground.
As Demangeon also noted:
This system announces what is to come. We as a society have been hunting terrestrial planets since the birth of astronomy and now we are finally getting closer and closer to the detection of a terrestrial planet in the habitable zone of its star … [when we find one,] we could study the atmosphere.
Conclusion: A team of astronomers using the Very Large Telescope has made new observations of a fascinating neighboring planetary system. One planet is half the mass of Venus, another can be an ocean world, and another possible planet resides in the habitable zone.
Source: Hot terrestrial planet with half the mass of Venus passing through a nearby star
Via ESO
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