James Webb Space Telescope, year 1: an already busy schedule

First galaxies, distant stars, exoplanets... the program for the first year of observation has been determined in advance by a committee of experts, and has been for more than a year now.

Anyone can, in theory, use this telescope for their research -- as long as they know what to observe, and have their proposal selected.

Among the lucky winners, Olivia Lim, a doctoral student at the University of Montreal, is only 25 years old.

"I have the chance to use this telescope when I was not even born when people started talking about it," she told AFP.

Its goal: to observe planets revolving around a star named Trappist-1.

The system has seven planets in all, similar in size to Earth.

They are so close to each other that from the surface of one, you could see the others appearing clearly in the sky.

The system "Trappist-1 is unique", explains the young woman.

"All, or almost all, of the conditions there are favorable for the search for life outside our solar system."

Planets outside our solar system Jonathan WALTER AFP

They are indeed rocky (and not gaseous) planets.

In addition, three are in the so-called "habitable" zone, that is to say neither too close nor too far from their star, offering adequate temperatures for liquid water to exist on their surface.

Other advantages: they are located "only" 39 light years away.

And above all, we can see them pass in front of their star from our point of view (we say that they "transit" their star).

This is what makes it possible to study them, by observing the drop in luminosity that their passage in front of the star produces.

Several of these transits should be observed as early as this month.

It's not yet known if these planets have an atmosphere, but that's what Olivia Lim is looking to find out.

If so, the light passing through the atmosphere will be "filtered" by the molecules it contains.

The jackpot would be to detect the presence of water vapor, CO2 or ozone, specifically sought.

Trappist-1 is such a prime target that several other science teams have also been granted time to observe them.

Finding traces of life there, if they exist, will still take time, according to Olivia Lim.

But "everything we are doing this year are really important steps to reach this ultimate goal", underlines the researcher.

Childhood of the Universe

Besides exoplanets, one of James Webb's other great promises is the exploration of the early ages of the Universe.

How?

Because the farther one looks, the longer one sees.

Sunlight, for example, takes eight minutes to reach us, so we see it as it was eight minutes ago.

Thus, by looking as far as possible, one can perceive the light as emitted billions of years ago.

The most distant star ever detected could be observed by the Hubble telescope thanks to a phenomenon called gravitational lensing, as shown in this image from the European Space Agency (ESA) - NASA/ESA/AFP

Astronomers have so far managed to go back 97% of the time to the Big Bang, which occurred 13.8 billion years ago.

But the most distant galaxies appeared for the moment only in the form of "tiny red spots", explained to AFP Dan Coe, astronomer at the Space Telescope Science Institute, in charge of James Webb's operations in Baltimore, near from Washington.

The researcher has two upcoming observation programs: the first targeting one of the most distant galaxies known, MACS0647-JD, discovered in 2013, and the second focusing on Earendel, the most distant star ever detected, since this year. only.

“With James Webb, we are finally going to be able to see inside these galaxies, to see what they are made of, both in images and by spectroscopy, it is going to be incredible”, he assured.

Spectroscopy makes it possible, via the analysis of the light captured, to determine the chemical properties of a distant object.

If recent galaxies can be elliptical or spiral, the oldest were more "irregular", notes Dan Coe.

The Big Bang: the origins of the Universe Jonathan WALTER AFP

And we don't yet know what the very first stars look like, which probably began to form about a hundred million years after the Big Bang.

According to the theory, these early so-called population III stars were much more massive than our Sun, and made entirely of hydrogen and helium.

Their supernova explosion then contributed to enrich the interstellar medium, until the formation of the planets and stars of today.

Some doubt that it is possible to see these stars.

But that won't stop astronomers from continuing to try.

© 2022 AFP