On August 11, the website of the American "Atlantic" monthly magazine published an article entitled "Distant Planets Are No Longer So Far", written by Marina Coren, and the full text is excerpted as follows:
As with many things in the 1990s, one of the most exciting discoveries in astronomy began with a fax.
In the summer of 1994, Didier Queiroz, an astronomer at the University of Geneva, collated data obtained through new telescope techniques that measured the subtle motion of stars. Scientists believe that such movement may indicate that there are planets outside the solar system orbiting their own sun. A distant planet's gravitational pull could drag its star along, causing it to wobble slightly. No one had previously discovered a so-called exoplanet in this way, so when Queiroz finally spotted a rocking star, he thought it might be an instrumental error. But the mysterious trembling did not disappear. So Queiroz faxed his adviser Michelle Mayor, who was on leave in Hawaii: "I think I've found a planet. ”
This shaking reveals a world about half the mass of Jupiter orbiting a sun-like star about 50 light-years away. Queiroz and his team named it "51 Pegasus" based on the stars it orbited. The existence of the planet itself is surprising, but it also suggests something extraordinary: there must be more such planets.
Exoplanets come in all shapes and sizes
There is indeed more – very, very much more. Since then, astronomers have confirmed that there are more than 4,400 exoplanets in the Milky Way. They found cold and hot planets, lava-strewn planets and rain-dropping planets, marshmallow-dense planets, and, quite literally, planets that are evaporating into space. But today, the astronomical community is less concerned about a discovery than before. "For the first 20 years, the exoplanet field was really in that philatelic phase," said Jessie Christiansen, an astrophysicist at NASA who studies exoplanets. ”
Now, there are enough planets to really study what they look like. Researchers are pushing the limits of existing technology and imagining more powerful tools to complement the details and apply the attractive prefix exo to other fields: extraschedulary topography, extra-departmental geology, extra-departmental ecology, and extra-satellites. In the tiny flicker of distant starlight, astronomers are no longer limited to just detecting new planets, but are studying these distant worlds with unprecedented precision.
While scientists discovered 51 Pegasus through the motion of a single star, most exoplanets since then have been discovered through the light of stars. When a distant planet orbits in front of its star, it blocks a trace of starlight, causing us to temporarily darken the star from Earth. When astronomers observe a star long enough and record data on its dimming, they can confirm not only the existence of a planet, but also how long it takes for that planet to orbit its star, the composition of its atmosphere, and the temperature of its surface.
These are the basics of exoplanets that are usually easy to distinguish. But the light of other stars contains more information that we're just beginning to understand. For example, an astronomer studied the amount of stellar light reflected by exoplanets to analyze what might make up their surfaces, such as ice being more reflective than water and water being more reflective than dust. One of the most interesting methods I've come across recently has taken a turn for the traditional method of finding exoplanets by stellar light. Moia McTiel, an astrophysicist who studies exoplanets, explains: "We know that rocky planets will have some bumpy features that, if such planets turn in front of the star, will appear from time to time, thus blocking more of the star's light. "These tiny changes could indicate the presence of mountains, volcanoes and other towering terrain on the planet."
The signs of life are confusing
Astronomers are also increasingly aware of the skies of exoplanets, using telescopes to observe the characteristics of distant atmospheres as much as possible. Planets with atmospheres absorb part of their star's light, leaving an imprint on the light that eventually reaches Earth. Scientists studied these imprints to find evidence of various molecular signatures in the atmospheres of extrasolar planets: oxygen, hydrogen, sodium, iron and even water vapor. Some of this matter is fairly common in the universe, so astronomers are now expanding their search to include some of the more unusual biological features — that is, those produced by organisms rather than chemical processes — and to study how they can spot this unique imprint in the light of stars.
Only recently have researchers begun looking for more advanced signs of life on exoplanets, known as radio signals from busy societies. Recently, Breakthrough Listening, a project dedicated to finding radio signals from intelligent civilizations, has collaborated with NASA's Transiting Exoplanet Survey Satellite, which has discovered 144 proven exoplanets hidden in the light of other stars. Earth's radio emissions have been drifting into space for decades, relaying information about our existence. The same may be true for other planets.
Ultimately, the impetus for exoplanet research is not so much the search for new types of worlds as it is about finding a specific one: Can we find another Earth? Most of the planets astronomers have discovered so far, including 51 Pegasus (the protagonist of the astronomy-changing fax), are uninhabitable. We're still looking for what NASA astrophysicist Christiansen calls the "holy grail of exoplanets": a rocky planet about the size of Earth that orbits in the habitable orbit of its star, where water doesn't freeze or evaporate all the time, but rather distributes on its surface. In such a place — and indeed the only place — we can confidently say that life may arise.
Of the thousands of known exoplanets, only 165 are rocky planets the size of Earth, which are harder to detect than giant planets made of gas. Still, astronomers have statistics to support it. Scientists estimate that every star in the Milky Way has at least one planet, and they believe that planets located within the star's habitable zone are common. As author Joe Marchante writes in her book The Human Universe: "Even if life were unlikely to occur on a particular planet, we know that there are billions of opportunities for life in our galaxy alone." ”
It's too far away to visit
But, as often happens in exoplanet research, technology is still catching up with the theory. For example, to try McTil's extrascienceal topography approach, the astronomical community needs more powerful instruments than are currently in operation. Astronomers can only fantasize about seeing something as wonderful as someone else's city lights twinkling or as striking as an explosion-proof barrier built to ward off deadly supernovae. Despite all these new studies, we are still many years away from photographing small rocky planets with resolutions greater than a single pixel.
The study of exoplanets reminds me of the Apollo moon landings, the only other worlds humans have actually been to. When Armstrong, Aldrin and Collins returned from that trip, they filled out a customs form calling the "moon" their place of departure and declaring lunar rock and lunar soil samples as carry-on items. That little piece of paper turned the moon into a place where people could really reach and walk. Humans may visit the moon again, and maybe one day mars will become a place of visit.
We can certainly try to make exoplanets somewhere in some way — with great illustrations, as Yale anthropologist Lisa Messeri puts it, writing about how scientists can help the public see scientific goals like exoplanets as the real world. Perhaps this gives some of us— non-scientists who don't spend a lot of time analyzing starlight— a vague feeling. "Being able to determine similarities — even if we can't get there — is like somehow shrinking the universe and making us feel more connected," Messery said. ”
However, for the foreseeable future, exoplanets will remain very distant and abstract. Even at one-tenth of the speed of light, it will take decades to reach an Earth-sized planet around our nearest star. The study of extrasolar planets always returns to a sad but immutable truth: a large part of astronomy is trying to understand everything outside on Earth, and there is always a limit to where we can reach.
Source: Reference News Network