This month will mark a new chapter in the search for extraterrestrial life, where the most powerful space telescope ever built will begin spying on planets orbiting other stars. Astronomers hope that the James Webb Space Telescope will reveal whether some of these planets harbor atmospheres that could support life.
It would be remarkable enough to describe an atmosphere in another solar system. But there’s even a chance – albeit small – that one of these atmospheres presents what’s known as a biosignature: a signal of life itself.
“I think we might find planets that we think are interesting — you know, good prospects for life,” said Megan Mansfield, an astronomer at the University of Arizona. “But we won’t be able to define life right away.”
So far, Earth remains the only planet in the universe known to have life. Scientists have been sending probes to Mars for nearly 60 years and have yet to find the Martians. But life might be lurking beneath the surface of the Red Planet or waiting to be discovered on the moon of Jupiter or Saturn. Some scientists even gave hope VenusDespite its scorching atmosphere of sulfur dioxide clouds, it may be home to Venusians.
Even though Earth is the only planet in our own solar system that harbors life, many other solar systems in the universe have so-called exoplanets.
In 1995, Swiss astronomers detected the first exoplanet orbiting a sun-like star. Known as 51 Pegasi b, the exoplanet has become a puffy gas giant larger than Jupiter and a hopeless home for life resembling 1,800 degrees Fahrenheit.
Since then, scientists have found More than 5,000 other exoplanets. Some are much more similar to Earth – roughly the same size, made of rock rather than gas, and orbiting their star in a “Goldilocks region”, not close enough to be baked but not far enough to freeze.
Unfortunately, the relatively small size of these exoplanets has made them extremely difficult to study until now. The James Webb Space Telescope, launched last Christmas, will change that by acting as a magnifying glass to allow astronomers to take a closer look at these worlds.
Since the telescope was launched from Kourou, French Guiana He travelled A million miles from Earth, it enters its own orbit around the sun. There, a shield protects its 21-foot mirror from the sun or any heat or light from the Earth. In this deep darkness, the telescope can detect faint, distant flashes of light, including those that could reveal new details about distant planets.
Dr. said Mansfield.
NASA engineers began taking pictures of a range of objects with the Webb telescope in mid-June and will release their first images to the public on July 12.
Eric Smith, chief scientist of the program, said that exoplanets will be included in this first set of images. Since the telescope will spend relatively little time observing exoplanets, Dr. Smith described these early images as a “quick and dirty” look at the telescope’s power.
These quick glances will be followed by a series of much longer observations, starting in July, providing a much clearer picture of the exoplanets.
Several teams of astronomers plan to look into this. seven planets It orbits a star called Trappist-1. Earlier observations suggested that three of the planets occupy the habitable zone.
“It’s an ideal place to look for signs of life outside the solar system,” said Olivia Lim, a graduate student at the University of Montreal who will be observing the Trappist-1 planets from July 4th.
Because Trappist-1 is a small, cool star, its habitable zone is closer to it than our own solar system. As a result, potentially habitable planets orbit at close range, and it only takes a few days to circle the star. Every time planets pass in front of Trappist-1, scientists will be able to solve a fundamental but very important question: Does anyone have an atmosphere?
“If it doesn’t have air, it’s not habitable, even if it’s in the habitable zone,” said Nikole Lewis, an astronomer at Cornell University.
Dr. Lewis and other astronomers wouldn’t be surprised to find no atmospheres surrounding the planets of Trappist-1. Even if the planets developed atmospheres when they formed, the star may have blasted them with ultraviolet and X-ray radiation long ago.
“It’s possible that they can pull out all the atmosphere on a planet before it even has a chance to start forming life,” says Dr. said Mansfield. “That’s the first-order question we’re trying to answer here: whether these planets will have atmospheres long enough to develop life.”
A planet passing in front of Trappist-1 will cast a tiny shadow, but the shadow will be too small for the space telescope to capture. Instead, the telescope will detect a slight dimming in the light from the star.
“It’s like looking at a solar eclipse with your eyes closed,” said Jacob Lustig-Yaeger, a postdoctoral researcher at the Johns Hopkins Applied Physics Laboratory. “You may have an idea that the light is out.”
A planet with an atmosphere darkens the star behind it differently than a bare planet. Some of the star’s light will pass directly through the atmosphere, but the gases will absorb light at certain wavelengths. If astronomers looked only at starlight at these wavelengths, it would further dim the planet Trappist-1.
The telescope will send these observations of Trappist-1 back to Earth. “Then you get an email like ‘Hello, your data is available,'” says Dr. said Mansfield.
But the light from Trappist-1 will be so weak that it will take time to realize it. “Your eye is used to dealing with millions of photons per second,” says Dr. said Smith. “But these telescopes collect only a few photons per second.”
Dr. Mansfield or other astronomers will be able to analyze exoplanets passing in front of Trappist-1, first they will need to distinguish it from tiny fluctuations produced by the telescope’s own machinery.
Dr. said Mansfield.
At the end of these efforts, Dr. Mansfield and his colleagues will discover an atmosphere around a Trappist-1 planet. However, this result alone will not reveal the nature of the atmosphere. It can be rich in nitrogen and oxygen as on Earth, or more like the poisonous carbon dioxide and sulfuric acid stew on Venus. Or it could be a mix that scientists have never seen before.
“We have no idea what these atmospheres are made of,” said Alexander Rathcke, an astronomer at the Technical University of Denmark. “We have ideas and simulations and all that stuff but we really have no idea. We have to go look.”
The James Webb Space Telescope, sometimes called the JWST, may be powerful enough to identify certain components of exoplanet atmospheres because each type of molecule absorbs a different range of light wavelengths.
These discoveries, however, will depend on the weather on the outer planets. A bright, reflective cloud cover can block any starlight from entering an exoplanet’s atmosphere and ruin attempts to find alien aura.
“It’s really hard to distinguish between a cloudy or a cloudy atmosphere,” says Dr. said Rathcke.
If weather cooperates, astronomers are particularly eager to see if exoplanets have water in their atmospheres. At least on Earth, water is a basic requirement for biology. “We think this would probably be a good starting point for searching for life,” says Dr. said Mansfield.
But a watery atmosphere does not necessarily mean that an exoplanet is harboring life. To make sure a planet is alive, scientists will have to detect a biosignature, a molecule, or a combination of several molecules that has been prominently made by living things.
Scientists are still debating what would be a reliable biosignature. Earth’s atmosphere is unique in our solar system in that it contains a lot of oxygen, which is largely the product of plants and algae. But oxygen can also be produced without the help of life when water molecules in the air split. Methane can likewise be released by living microbes, but also by volcanoes.
It is possible that there is a certain gas balance that can provide a clear biological signature that cannot be sustained without the aid of life.
“We need extremely favorable scenarios to find these biological signatures,” said Dr. Rathck. “I’m not saying it’s not possible. I just think it’s very far. We have to be extremely lucky.”
Finding such an equilibrium might require the Webb telescope to observe a planet passing repeatedly in front of Trappist-1, said planetary scientist Joshua Krissansen-Totton of the University of California, Santa Cruz.
“If in the next five years someone says, ‘Yes, we came to life with JWST,’ I would be very skeptical of that claim,” says Dr. Krissansen-Totton said
It is possible that the James Webb Space Telescope failed to find the biosignatures. That mission may have to wait for the next generation of space telescopes more than a decade away. They will study exoplanets in the same way that humans look at Mars or Venus in the night sky: instead of observing them as they pass in front of a star, by observing the reflected starlight against the black background of space.
Dr. Rathck guessed. “I would be very surprised if JWST provides biosignature detections, but I hope to get it fixed. So, that’s basically what I’m doing this work for.”
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