Webb Telescope just proved it can detect signs of life in alien atmospheres

(ORDO NEWS) — The ingredients for life are scattered throughout the universe. Although the Earth is the only known place in the Universe where life exists, the discovery of life beyond the Earth is the main goal of modern astronomy and planetary science.

We are two scientists who study exoplanets and astrobiology. Thanks in large part to next-generation telescopes like James Webb, researchers like us will soon be able to measure the chemical composition of planetary atmospheres around other stars.

Hopefully one or more of these planets will have the chemical signature of life.

Habitable exoplanets

Life can exist in the solar system where there is liquid water, such as underground aquifers on Mars or in the oceans of Jupiter’s moon. Europe. However, the search for life in these places is incredibly difficult, as they are difficult to reach, and discovering life would require sending a probe to obtain physical samples.

Many astronomers believe that there is a strong possibility that life exists on Earth. planets orbiting other stars, and perhaps that is where life will be discovered for the first time.

Theoretical calculations show that only in the Milky Way galaxy there are about 300 million potentially habitable planets, and within just a few habitable Earth-sized planets 30 light-years from Earth, in fact, humanity’s galactic neighbors.

To date, astronomers have discovered more than 5,000 exoplanets, including hundreds potentially habitable, using indirect methods that measure how a planet affects its closest star. These measurements can give astronomers information about the exoplanet’s mass and size, but not much else.

Search for biosignatures

To detect life on a distant planet, astrobiologists will study starlight that interacts with the planet’s surface or atmosphere. If the atmosphere or surface has been transformed by life, the light may carry a clue called a “biosignature”.

During the first half of its existence, Earth had an atmosphere without oxygen, although simple, single-celled life existed on it. During this early era, the Earth’s biosignature was very weak. The situation changed dramatically 2.4 billion years ago, when a new family of algae appeared.

Algae used the process of photosynthesis, which produced free oxygen – oxygen that is not chemically bound to any other element. Since then, Earth’s oxygenated atmosphere has left a strong and easily detectable biosignature of light passing through it.

When light reflects off a material surface or travels through a gas, certain wavelengths of light are more likely to remain trapped in the gas or material surface than others. Selective capture of wavelengths of light explains why objects have different colors.

The leaves are green because chlorophyll is particularly good at absorbing light in red and blue wavelengths. When light hits a leaf, the red and blue waves are absorbed, leaving mostly green light that reflects back into your eyes.

The light transmission pattern is determined by the specific composition of the material with which the light interacts. . Thanks to this, astronomers can learn something about the composition of the atmosphere or the surface of an exoplanet, in essence, by measuring a certain color of light coming from the planet.

This method can be used to recognize the presence of certain atmospheric gases associated with life, such as oxygen or methane, because these gases leave very specific traces in light. It can also be used to detect specific colors on a planet’s surface.

For example, on Earth, chlorophyll and other pigments used by plants and algae for photosynthesis trap specific wavelengths of light.

These pigments create characteristic colors that can be detected with a sensitive infrared camera. If you were to see this color reflecting off the surface of a distant planet, it would potentially mean the presence of chlorophyll.

Telescopes in space and on Earth

It takes an incredibly powerful telescope to detect these subtle changes in the light coming from a potentially habitable exoplanet. So far, the only telescope capable of such a feat is the new James Webb Space Telescope.

Starting scientific work in July 2022, James Webb measured the spectrum of the gas giant exoplanet WASP-96b. The spectrum showed the presence of water and clouds, but a planet as large and hot as WASP-96b is unlikely to be home to life.

However, these early data show that James Webb is capable of detecting weak chemical signatures. in light from exoplanets.

In the coming months, Webb will point its mirrors at TRAPPIST-1e, a potentially habitable Earth-sized planet just 39 light-years from Earth.

Webb can look for biosignatures by studying planets as they pass in front of their stars and by capturing starlight as it passes through the planet’s atmosphere. But Webb was not designed to search for life, so the telescope is only able to carefully study a few nearby potentially habitable worlds.

It can also only detect changes in the levels of carbon dioxide, methane, and water vapor in the atmosphere. Although certain combinations of these gases may indicate the presence of life, Webb cannot detect the presence of free oxygen, which is the strongest signal of life.

Leading concepts for future, even more powerful space telescopes include plans to block out the bright light of the planet’s host star to show starlight reflected off the planet. This idea is like using your hand to block out sunlight so you can see things better from a distance.

Future space telescopes could use small internal masks or large, umbrella-like external spacecraft to do this. Once the starlight is blocked, it becomes much easier to study the light bouncing off the planet.

In addition, three huge ground-based telescopes are currently under construction that will be able to search for biosignatures: the Giant Magellan Telescope, the Thirty Meter Telescope and the European Extra Large Telescope.

Each of them is much more powerful than the existing telescopes on Earth, and despite the fact that the Earth’s atmosphere distorts starlight, these telescopes can explore the atmosphere. worlds closest to oxygen.

Is it biology or geology?

Even using the most powerful telescopes of the coming decades, astrobiologists will only be able to detect the strong biosignatures produced by worlds that have been completely transformed by life.

Unfortunately, most of the gases given off by terrestrial life can also be produced by non-biological processes cows and volcanoes give off methane. Photosynthesis produces oxygen, but so does sunlight when it splits water molecules into oxygen and hydrogen.

There is a strong possibility that astronomers will find some false positives when searching for distant life. To rule out false positives, astronomers need to study the planet of interest well enough to understand whether its geological or atmospheric processes can mimic the biosignature.

The next generation of exoplanet research could exceed all expectations. bar of extraordinary evidence needed to prove the existence of life. The first release of data from the James Webb Space Telescope gives us a glimpse of the exciting progress that is about to happen.


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