Thu. May 26th, 2022

The James Webb Space Telescope is able to look closely at exoplanets one at a time and study their atmospheres with unprecedented accuracy. But perhaps the most exciting planetary targets will be a star system that is strangely analogous to our own: the TRAPPIST-1 system.

The James Webb Space Telescope is able to study exoplanets, giving us a clearer (still blurred) picture of what planets outside our own solar system look like, and critical details about their composition – including whether they may be able to support life. In its first year, Webb will look at about 70 exoplanets, but NASA exoplanet expert Knicole Colòn explains that TRAPPIST-1 is particularly remarkable for several important reasons.

“The TRAPPIST-1 system is at the top of everyone’s list,” she says.

What is TRAPPIST-1?

TRAPPIST-1 is a star that was first discovered in 1999 and then christened 2MASS J23062928-0502285. It is an ultra-cool red dwarf star, which means that it is among the coolest of dwarf stars – and it is only 4,400 degrees Fahrenheit or 2,430 degrees Celsius (the Sun is almost 10,000 degrees Fahrenheit on the surface, for comparison). TRAPPIST-1 is only nine percent as massive as the Sun.

TRAPPIST-1 is about 40 light-years from Earth – out of reach of any man-made vessel imaginable, but on the scale of the galaxy, TRAPPIST-1 is the crazy but nice neighbor who lives across the street and invites you to to grill every summer.

TRAPPIST-1 got its current name after scientists discovered three exoplanets orbiting the star in May 2016 using the transit method, whereby diving in the star’s light betrayed the planets’ existence to astronomers. The finding came from observations made by the Transiting Planets and Planetesimals Small Telescope (TRAPPIST, get it!), Which is a ground-based observatory in Chile.

And behold, 2MASS J23062928-0502285 became TRAPPIST-1 and its planets were called TRAPPIST-1b, TRAPPIST-1c and TRAPPIST-1d.

TRAPPIST-1 system, explained

Just a few months after their discovery was announced in July 2016, Hubble data revealed that TRAPPIST-1b and TRAPPIST-1c both did not appear to have thick gas atmospheres – suggesting that they may be rocky planets like Earth. Both TRAPPIST-1b and TRAPPIST-1c are also small planets – about the same size as Earth.

“The lack of a suffocating hydrogen-helium envelope increases the chances of habitability on these planets,” said Nikole Lewis, then of the Space Telescope Science Institute (STScI) in Baltimore, according to a statement to NASA at the time.

“If they had a significant hydrogen-helium sheath, there is no chance that any of them could potentially support life because the dense atmosphere would act as a greenhouse,” she explains.

Since then, scientists have discovered four more planets orbiting TRAPPIST-1. This is interesting because our own solar system has eight planets orbiting a single star, so it is a similar number of planets, but the two systems look very different from each other.

“This is a really small star that has seven planets, all of which are [similar to the] The size of the earth, ”explains Colòn. “A few of these planets are in the Golden Lock Zone.”

Goldilocks Zone, for clarification, is the name given to the area close enough and far enough from a star where a planet could maintain liquid water at the surface – a key ingredient for habitability.

NASA’s Spitzer Space Telescope and ground-based telescopes later helped confirm two of the planets found in 2016 and discovered all the other planets in orbit using the transit method. The Spitzer mission ended in January 2020, but at the time it was doing science, it observed the system for more than 1,000 hours. Kepler, also now retired, also studied the system. Now it will be up to the James Webb Space Telescope to continue this work.

“Every single one of the seven planets will be observed by Webb in some way,” Colòn confirms.

TRAPPIST-1 vs. The solar system

TRAPPIST-1 vs The Solar System.NASA

TRAPPIST-1 has seven planets in orbit, almost as many as our own star. But the TRAPPIST planets are quite different from the spheres we know best.

All the TRAPPIST planets orbit very close to their star – in fact, they are so close to their star that their orbits would all fit inside Mercury’s orbit, which is the closest planet to the Sun. TRAPPIST-1b orbits the star in just 1.5 days, but it has the same size and mass as Earth.

This is where things get interesting: All the TRAPPIST planets are all the same size as each other, and all appear to be rocky planets. In fact, the TRAPPIST planets all look suspiciously Earth-like.

“Some of them are not habitable at all – they are too hot or too cold,” says Colòn. “Webb will still be able to give us a big comparative project where we can say: Do these planets have something similar or in common? Because they are so similar in size and they formed around the same star.”

By combining direct observations with computer models, scientists believe that the TRAPPIST planets have a density equivalent to that of rocky planets, but it is difficult to read their properties from such measurements, as if they are more like the Moon – barren and gray – rather. than the Earth – wet and green.

“Densities, though important traces of planetary composition, say nothing about habitability,” Brice-Olivier Demory said in a statement to NASA in 2018. Demory is co-author of a study describing planetary features and a professor at the University of Bern. For example, even though the planets are not swollen gas giants, they may still turn out to have conditions more similar to Mars or Venus than Earth.

Some of the TRAPPIST planets also appear to contain significant amounts of water, although it is unknown whether this water can exist as a liquid on any of the planets’ surfaces in the same way as it does here on Earth. Some of the TRAPPIST planets may look more like ocean worlds, while those further out from their stars may be much drier or icy.

How Webb will study TRAPPIST-1

However, these differences and commonalities with our own planet and solar system are what make the TRAPPIST system so exciting for Webb to study, says Colòn.

“It’s one of the first real opportunities we have to study literally seven planets around the same star,” says Colòn. At stake is to answer a question that is both scientific and philosophical: Why are we here?

“Every single planet, even Jupiter-sized, really helps our understanding of how our own solar system was formed,” says Colòn.

“There are a lot of other planets that exist out there that are, and just so many are different from our own. That raises a question: How did our solar system originate exactly as needed? And is our solar system architecture something that is necessary for that life can be formed? “

“If Earth is the only habitable planet we know of,” she continues, “then we need to know, because if this is the only planet, then we must save our planet, right?”

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