Where to look for life in the solar system – Skywatching

One of the primary scientific goals of the James Webb Space Telescope Project is to search for life on planets orbiting other stars.

Even with this powerful telescope, these extra-solar planets will reveal themselves either as tiny faint spots located very close to the stars they orbit, or as minute gradations as they pass in front of their stars, blocking out a tiny fraction of the stars. . light.

Given this, how can we conduct a meaningful search for signs of life on these worlds?

The answer to this question can be traced back to Sir Isaac Newton, who discovered that passing light through a prism isolated all of the different color components of light. His discovery evolved into the modern science of spectroscopy. It allows you to look at a distant star and see what it is made of, what its temperature is and if it is approaching or moving away from us.

Matter is made up of atoms. Atoms of different elements are made up of different numbers of protons, neutrons and electrons. This gives them a distinct light signature. Two or more atoms can combine to form molecules. For example, a carbon dioxide molecule consists of one carbon atom and two oxygen atoms. A water molecule is made up of two hydrogen atoms and one oxygen atom.

An oxygen molecule is made up of two oxygen atoms joined together. Molecules also have their own unique light signatures.

Stars are generally too hot for molecules to exist for very long. Planets are colder, so molecules can exist in their atmospheres and on their surfaces. When we observe starlight, we see the signatures of atoms.

When one of a star’s planets passes in front of it, some of the starlight passes through the planet’s atmosphere – if it has one – and in doing so picks up the signatures of molecules in the planet’s atmosphere. the planet. So when this planet moves in front of the star, we see the signatures of molecules, and when the planet moves away, we only see atoms. This gives us a fairly reliable way to find out what the planet’s atmosphere looks like.

The trick to looking for life is to look for signatures of gases and chemical molecules in the planet’s atmosphere that shouldn’t be there. For example, we can search for oxygen molecules.

Oxygen is a very highly reactive material. It would very quickly disappear from a planet’s atmosphere by reacting with iron and other materials in rocks and soils.

The reason there are so many of them in our atmosphere is that living things make them, enough of them to make up for any loss.

Another reactive gas that would be an indicator of life on a world would be chlorine. This gas, deadly for us, would quickly disappear if it were not continuously renewed.

The question is which stars to point the telescope at in our search for life. A start would be stars like the Sun. We know that the star sustains life.

The Sun and the planets of the solar system formed around 4.5 billion years ago. Living creatures appeared about 3.8 billion years ago. If we assume that on average that’s the time it takes for life to appear on a planet and evolve into fairly advanced forms, then stars with shorter lifetimes, which include blue and white ones, won’t be eligible. Perhaps red dwarf stars would be ideal candidates. They might be dim, so their planets should be near them, but they’re so stingy with their fuel consumption that they’re able to glow steadily for tens of billions of years.

The worlds orbiting these stars could have plenty of time to develop life and evolve it, and even restart if the living creatures on these worlds destroy their surroundings, annihilating themselves. Our Sun will start to run out of fuel in about three billion years, so if we’re wrong, there won’t be time for a restart.


• Mars is low in the twilight of dawn.

• After sunset, Venus is near the southwestern horizon, with Saturn to its left and then Jupiter.

• The Moon will reach first quarter on January 9th.

Arline J. Mercier