Webb began searching for the first stars and habitable worlds

The first stunning images from the James Webb Space Telescope were unveiled this week, but its journey of cosmic discovery has only just begun.

Here’s a look at two early projects that will take advantage of the orbiting observatory’s powerful instruments.

The first stars and galaxies

One of the telescope’s great promises is its ability to study the earliest phase of cosmic history, shortly after the Big Bang 13.8 billion years ago.

The more distant objects are from us, the longer it takes their light to reach us, so to look back into the distant universe is to look back into the deep past.

“We’re going to look back to this earliest time to see the first galaxies that formed in the history of the universe,” explained Space Telescope Science Institute astronomer Dan Coe, who specializes in the early universe.

Astronomers have so far gone 97 percent of the way back to the Big Bang, but “we just see these little red blobs when we look at these galaxies that are so far away.” “With Webb, we will finally be able to peer into these galaxies and see what they are made of.” While today’s galaxies are shaped like spirals or ellipticals, the earliest building blocks were “clumsy and irregular,” and Webb should reveal -old redder stars in them, more like our Sun, that were invisible to the Hubble Space Telescope.

Coe has two Webb projects observing one of the most distant galaxies known, MACS0647-JD, which he discovered in 2013, and Earendel, the most distant star ever discovered, discovered in March of this year.

While the public has been drawn to Webb’s stunning pictures, which were taken in the infrared, as light from deep space expanded into these wavelengths as the universe expanded, scientists are just as keen on spectroscopy.

Analysis of an object’s light spectrum reveals its properties, including temperature, mass and chemical composition, effectively forensic astronomy.

Science still doesn’t know what the earliest stars, which probably began to form 100 million years after the Big Bang, will look like.

“We may see things that are very different,” Coe said, so-called “Population III” stars, which are theorized to have been much more massive than our own Sun and “virgin,” meaning they are were composed only of hydrogen and helium.

They eventually exploded in supernovae, contributing to the cosmic chemical enrichment that created the stars and planets we see today.

Some doubt that these pristine Population III stars will ever be found, but that won’t stop the astronomical community from trying.

Anyone out there?

Astronomers earned time on Webb based on a competitive selection process open to all, regardless of how advanced in their careers they are.

Olivia Lim, a PhD student at the University of Montreal, is only 25 years old. “I wasn’t even born when people started talking about this telescope,” she told AFP.

Its goal: to observe rocky planets roughly the size of Earth orbiting a star called Trappist-1. They are so close together that from the surface of one you can see the others appear clearly in the sky.

“The Trappist-1 system is unique,” explains Lim. “Almost all conditions there are favorable for searching for life outside our solar system.” In addition, three of Trappist-1’s seven planets are in Goldilocks’ “habitable zone,” neither too close nor too far from its star, allowing the exact temperatures for the existence of liquid water on their surface.

The system is “only” 39 light years away and we can see the planets pass in front of their star.

This makes it possible to observe the dip in luminosity that occurs when crossing the star and to use spectroscopy to infer planetary properties.

It’s not yet known whether these planets have atmospheres, but that’s what Lim wants to find out. If so, light passing through these atmospheres will be “filtered” through the molecules they contain, leaving signatures for Webb.

The jackpot for her would be to detect the presence of water vapor, carbon dioxide and ozone.

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

Finding traces of life there, if they exist, will still take time, according to Lim. But “everything we’re doing this year is really important steps to get to that ultimate goal.”