The first stunning images from NASA’s James Webb Space Telescope were unveiled this week, but the journey of space discovery has only just begun. Here’s a look at two early projects that will use the orbiting observatory’s powerful instruments.
One of the telescope’s great promises is its ability to study the early phase of cosmic history, shortly after the Big Bang 13.8 billion years ago. The farther away objects are from us, the longer it takes for their light to reach us, and thus, peering into the distant universe means peering into the distant past.
While today’s galaxies are spiral or elliptical in shape, the earliest building blocks were “lumpy and irregular,” and Webb should detect older red stars, similar to our Sun, that were invisible to the Hubble Space Telescope.
Space Telescope Science Institute astronomer Dan Coe, who specializes in the early universe, has two Webb projects: observations of one of the most distant known galaxies, MACS0647-JD, which he discovered in 2013, and Earendel, the most distant star ever detected, which was discovered in March of this year.
While the public has been enthralled by Webb’s stunning infrared images, because light from deep space has been stretched to these wavelengths as the universe expands, scientists are equally enthralled by spectroscopy. Analyzing an object’s light spectrum reveals its properties, including temperature, mass, and chemical composition—essentially forensics for astronomy. Science does not yet know what the earliest stars, which probably began to form 100 million years after the Big Bang, will look like.
“We might see things that are very different,” said Coe—so-called “Population III” stars that are theorized to have been much more massive than our own Sun, and “pristine,” meaning they were made up solely of hydrogen and helium. These eventually exploded in supernovae, contributing to the cosmic chemical enrichment that created the stars and planets we see today. Some are doubtful these pristine Population III stars will ever be found—but that won’t stop the astronomical community from trying.
Astronomers won time on the Webb based on a competitive selection process open to anyone, regardless of how advanced they are in their careers. Olivia Lim, a doctoral student at the University of Montreal, is only 25 years old. “I was not even born when people started talking about this telescope,” she told. Her goal: to observe rocky planets about the size of Earth orbiting the star of the Trappist-1 system. They are located so close to each other that from the surface of one of them you could clearly see how others appear in the sky. “The Trappist-1 system is unique,” explains Lim. “Almost all of the conditions there are favorable for the search for life outside our solar system.”
Additionally, three of Trappist-1’s seven planets are in Goldilocks’ “habitable zone,” neither too close nor too far from their star, allowing them to maintain the right temperature for 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 drop in luminosity caused by the crossing of the star and to use spectroscopy to determine the properties of the planets. It is not yet known whether these planets have atmospheres, but Lim wants to find out. If so, light passing through these atmospheres would be “filtered” through the molecules they contain, leaving trails for the Webb. The jackpot would be detecting the presence of water vapor, carbon dioxide and ozone.
Trappist-1 is such an important target that several other scientific groups have also been given time to observe them. Finding traces of life there, if they exist, will still take time, Lim said. But “everything we’re doing this year are really important steps to get to that ultimate goal.”
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