A new age of discovery began around the 21st century.
Astronomers used the latest telescopes on land and in space to find planets outside our solar system. Over 4,480 exoplanets have been confirmed in the Milky Way. Some are rocky. Many are part of a class of planets called "super-Earths," which are larger than our blue world. Jupiter is a gas giant.
There could be hundreds of billions of planets in our universe. We don't know much about them.
The recently launched James Webb Space Telescope has only been able to barely scratch the surface.
We've only been able to scratch the surface.
The telescope will be used to take unprecedented images of the deepest part of the universe. The powerful space instrument will devote a full quarter of its first year to peering at exoplanets in the Milky Way.
We will be able to understand these far-off worlds with specialized equipment that is called spectrometers. We will discover if the atmospheres of these planets contain the stuff that allows life to flourish: essential ingredients like water, carbon dioxide, and methane. The instruments are not expected to deliver any amazing exoplanet photos, but they will give us a wealth of information about worlds we can still only imagine.
An artist's concepton of a star. The SETI Institute and JPL-Caltech are credited.
The unseeable.
Super-Earths are some of the most common exoplanets. The exoplanet is larger than Earth and is in a region where liquid water can exist. K2-131b, which is so close to its star that it can "vaporize metal", is considered a merciless place by planetary scientists. Over 1,500 diverse super-Earths have been found by the astronomer. They are still mysterious.
Is Earth remotely like any of them? We don't know if they have atmospheres.
Webb will allow us to make these detections. We will see if any of these planets have the same amount of carbon dioxide and water as Earth. He said it was huge.
Using precious telescope time to find new exoplanets is not something that will be used by Webb. The most discoveries were made by the planet-hunting telescope, which stared at stars in small windows of space for nearly a decade, looking for dips in their brightness. The dips were caused by planets passing in front of their stars. The distant super-Earths will appear as dots even for the mighty JWST. The telescope can learn a lot about the atmospheres of these worlds.
Astronomers will use a tactic to see the unseeable. They will wait for planets to travel in front of their stars. This starlight goes through the atmosphere of an exoplanet, then through space, and finally into instruments called spectrographs aboard the JWST. The light is separated into a rainbow of colors. The big trick is that certain molecules in the atmosphere absorb certain types of light. Each molecule has a diet. If that color doesn't show up in the spectrum of colors observed by a telescope, that means it got absorbed by the exoplanet's atmosphere. That element is present in that planet's skies. The spectrograph produces lines, not pretty pictures, but it's a wealth of information.
A spectrum of light from the testing of NIRCam. Néstor Espinoza is a credit.
An artist's conception of an exoplanet. Astronomers use transit spectroscopy. Credit: Hubble, NASA, and the European Space Agency.
Mercedes Lpez-Morales is an exoplanet researcher and astronomer at the Center for Astrophysics-Harvard and the Harvard College. Lpez-Morales is on a team that is researching exoplanet atmospheres. She explained that the spectrometers will gather information about atmospheres in other ways, but transit spectroscopy is the primary method.
Direct images of larger planets, like Neptune or larger, will be taken by Webb. Smaller planets emit less light than larger planets. The human eye can't see this light, but it can be seen by the computer, which can decipher it from trillions of miles away.
An artist's illustration of a telescope. The NASA GSFC is credited to Adriana Manrique Gutierrez.
Is there anything left to live for?
We will be told if our solar system is normal or strange. It could tell us whether or not there is a normal.
There are many questions. What are the most popular solar systems? Is a planet like Earth rare, a place filled with water and hospitable to life? Do our gas giants have the same atmospheres as other giants?
Lpez-Morales said that webb will allow us to put our solar system in context.
It won't tell us if a planet has life. A world with all the right ingredients can't identify life even with the most powerful space telescope ever built. Is it alive or not? That's a very complex question.
A lot of ingredients factor into habitability. Venus' atmosphere was very thick and heavy, which made it impossible for surface life. A world that is flush with water is dominated by ice ages, leaving few chances for organisms to flourish. This is all knowledge. Lpez-Morales said that it takes a lot of information to claim a planet.
The observations of Webb will point the right way for exoplanet scientists. Lpez-Morales said it takes us to the next level. A planet with elements and conditions similar to Earth is scientific gold. She said that the world would become a high priority candidate for further investigation.
An artist's conception of an exoplanet's surface, with its star in the background. T. Pyle is credited with NASA / JPL-Caltech.
An artist's illustration of a planet. Its surface is covered in lava. Credit: NASA.
Future telescopes that are designed to better probe Earth-like exoplanets could then pursue the promising leads of the previous one.
As we seek the potential for life in exoplanets located in warm regions of solar systems, we may ignore other places where life could blossom. Scientists in our home solar system are excited about the possibility of life on Jupiter's distant moon Europa. The moon Enceladus may have an ocean under a shell of ice. "These places where we think life could exist are all outside the habitable zone," said an assistant professor of physics at the University of Nevada, Las Vegas, who researches exoplanets. We could be blinders if we focused on regions where a world like Earth might exist.
"We might learn things we didn't think about."
JWST will give us an unprecedented picture of what's out there in the universe. We don't know what we'll find.
Lpez-Morales said that they might learn things they never thought about.
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