Kepler-452b (sometimes nicknamed Earth 2.0 or Earth’s cousin) is an exoplanet orbiting the Sun … [+] the star Kepler-452 about 1,400 light-years (430 pc) from Earth in the constellation Swan. It is the first potentially rocky super-Earth planet discovered to orbit within the habitable zone of a star very similar to the Sun.
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This summer marks almost three decades since the discovery of 51 Pegasi b, the first known extrasolar planet orbiting a sun-like star. Today, there are more than 5,000 known planetary systems surrounding sun-like stars, and it is now believed that half of all sun-like stars are home to planets.
The discoveries of exoplanets only over the last decade, largely due to the work of NASA’s now-defunct Kepler space telescope, are enough to disturb the mind. But astronomers are now beginning to really characterize most of these planets. And it is possible that this is where the focus should be on this growing field of exoplanetary science.
Thus, two years after Covid-19 obstructed face-to-face meetings, one of the world’s largest exoplanetary science conferences, Extrasolar Planets IV (Exo4), has just ended in Las Vegas. Last week, I was able to catch up with Exo4 chair Jason Steffen to address some of the major issues in the field.
At the top of my list was simply why after decades of searching with both ground and space telescopes, we still have to find a true exo-earth.
We know of Earth-sized planets near the habitable zone, Steffen, an astrophysicist at the University of Nevada in Las Vegas, told me. But he says that in terms of understanding the properties of their atmospheres; the nature of any liquid water in the atmosphere or on its surfaces, we are still in a generation of telescopes that can offer us such measurements.
When will we start getting ghosts from an exoterrestrial?
2050 is a guess, says Steffen.
Swiss astrophysicist Michel Mayor, 2019 Nobel Prize in Physics and co-discoverer of the first … [+] exoplanet, speaks during an AFP interview at the Spanish Astrobiology Center in Torrejón de Ardoz on October 9, 2019. (Photo by JAVIER SORIANO / AFP) (Photo by JAVIER SORIANO / AFP via Getty Images)
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What does our study of exoplanets tell us about our own solar system?
“That you can have very different solar systems from ours,” Steffen said.
We have relatively good knowledge of how our solar system formed and evolved, but exoplanetary science says that here are all the other things that did not happen in our solar system that produce different types of planets, he says.
What about the synergy between solar system science and exoplanetary science?
Planetary scientists who focus on the bodies of our own solar system have a wealth of wealth, Steffen says. Mars researchers have had the luxury of taking surface samples there and conducting in situ analyzes that may indicate an abundance of dozens of chemical compounds. Solar system scientists also have access to the world’s best terrestrial spectrometers that can identify dozens of chemical species in the bodies of our solar system, from Mercury to Pluto.
But at this point, researchers from extrasolar planets are lucky if they can detect hydrogen in the atmosphere of an exoplanet, says Steffen. However, he points out that there is an area where there is fairer competition. This is in extrasolar dynamic measurements of the movements of a given planet. And how the movements of one planet affect the movements and movements of other planets within the same system.
We can understand the orbital properties of exoplanetary systems and compare them to the orbital properties of the planets in our solar system, says Steffen.
One of the most interesting presentations at the Exo4 conference involved identifying putative planetary material accumulated in the dying stellar remains known as white dwarfs.
White dwarf stars are super-dense, and if you dump something on a white dwarf, it would only remain visible on the surface for a few thousand years before everything sank inside, Steffen says.
So if you notice something that only has a thousand-year-old life in a star that has been there for a billion years, that tells you that it must have been a recent influx to the surface of a white dwarf, ”says Steffen. . That must be leftover planetary stuff, he says. This is the only method I know where the composition of the material that makes up the planet can be measured; that is, the abundance of nickel, iron, and sodium, Steffen says.
Would this material have originated from planets that were destroyed by the stellar end of the system itself?
It is unclear where this material came from; Either from planets that have been destroyed in the red giant phase of the star, or before the planet was swallowed up by the dying red giant, Steffen says.
The other big discussion on Exo4 was the evidence for the existence of a third planet of Earth’s mass around our nearest stellar neighbor, Proxima Centauri. Located just 4.2 light-years away, Proxima Centauri is a faint red dwarf that is literally the next star.
The evidence that there is a third terrestrial planet seems compelling, Steffen says. If it is habitable it seems a bit complicated, but the fact that we observe it around the star closest to us only indicates how common the formation of planets is, he says.
This illustration made available by the European Southern Observatory on Wednesday 15 November 2017 … [+] shows the planet Ross 128 b, in the foreground, orbiting a red dwarf star, 11 light-years from Earth. The exoplanet is the second closest to being detected outside our solar system with surface temperatures potentially similar to ours. (M. Kornmesser / ESO via AP)
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Is it a numbers game? Should we search for most planets or study them in detail?
We haven’t done detailed studies of even 10 percent of the planets that have been discovered by Kepler, Steffen says. While it’s worth finding more planets, it’s also worth understanding the planets we’ve discovered, he says.
Steffen says the Webb Space Telescope and the next generation of extremely large terrestrial telescopes are a way to characterize the atmospheres of many of the planets we have found. Observations spanning a longer period of time also add information about the systems where these planets reside, he says.
But exoplanetary science still doesn’t have the kind of funding it needs to allow for more risk-taking and high-reward initiatives, Steffen says.
“Everything is competitive to the point that the overwhelming majority of proposals are rejected,” Steffen said. “The current funding situation [makes] discipline is too risk-averse. “
A 30 percent success rate for grant proposals would be much healthier than the less than 10 percent success rate we see now, he says.
“Science would advance faster if there was enough room for more studies not to come out,” Steffen said.