Exposed (6/22/23)

Good afternoon, and happy Thursday. For those of us in the northern hemisphere, yesterday marked the summer solstice and longest day of the year. It’s all downhill from here, so I hope you’re soaking up those late summer days while you’ve got ’em.

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The Search for Habitable Worlds Continues

A planet in a relatively nearby solar system that had sparked astronomers’ hopes of finding potentially habitable worlds has turned out not to have much of an atmosphere (if any) after all.

In a study published Monday in Nature, researchers pointed their shiny new space telescope (i.e., JWST) toward TRAPPIST-1c, the third planet from its star, and ruled out the possibility of a thick carbon dioxide-rich atmosphere. If the exoplanet has an atmosphere at all, it’s extremely thin, the researchers found.

High expectations: The TRAPPIST-1 system, sitting about 40 light-years away from Earth, has long been a beloved observational target for astronomers searching for habitable planets elsewhere in the universe.

The system has a red M-class star at its center—smaller and dimmer than the Sun—and is orbited by no fewer than seven rocky, roughly Earth-sized planets.

• Three of these planets, TRAPPIST-1e, f, and g, sit within the star’s habitable zone.

• Habitable zone = the region around a star where temperatures are in the right range for liquid water to exist.

Since the system’s initial discovery in 1999, astronomers have been uncovering details about this star and its seven exoplanets, and to date, we know more about the TRAPPIST-1 system than we do about any other solar system in the universe (besides our own). Astronomers have conducted extensive observations using the Hubble and Spitzer space telescopes, among others, and it was time for the more powerful JWST to get its turn.

What we know: This is the second member of the TRAPPIST-1 system for which JWST has ruled out the presence of an atmosphere. (The first was TRAPPIST-1b, in findings published in March.)

The thing about M-class stars like the one at the center of this system is that they emit a large amount of UV radiation, which could prevent nearby bodies from maintaining atmospheres. For this reason, astronomers didn’t really expect TRAPPIST-1b to have an atmosphere, and it would have been surprising if TRAPPIST-1c had one either, despite its slightly further distance from the star.

• The new findings put the exoplanet’s surface temperature at ~380K (~225°F).

• While that’s the coolest of any rocky exoplanet we’ve found yet, it’s still too hot to maintain a thick, carbon dioxide-rich atmosphere.

What we don’t: Two down, five to go. JWST will continue to study the TRAPPIST-1 system and suss out details about the remaining exoplanets, searching specifically for that elusive carbon dioxide-rich atmosphere that would hint further at habitability.

Other News from the Cosmos

• Europa may have evolved more slowly than previously thought, creating its metallic core billions of years after its initial accretion, an ASU study suggests.

• Distances between galaxies can be measured more accurately via a new method of analyzing the luminosity and frequency of a specific type of pulsating star.

• Tryptophan, an amino acid essential for life as we know it on Earth, was spotted in Spitzer telescope observations of interstellar space.

• Black holes in the early universe may have been significantly more massive than expected, according to new modeling from CU Boulder.

• Sagittarius A*, the supermassive black hole at the center of the Milky Way, ended a long dormant period about 200 years ago, hints an echo found in X-ray data.

• Astronomers identified a white dwarf pulsar system, in which a rapidly-spinning white dwarf star interacts with a nearby red dwarf to produce regular flares of energy.

• NASA is funding five experiments to take advantage of next year’s total solar eclipse.

The View from Space

At the fringes of the Milky Way, astronomers spotted a star, unfortunately named LAMOST J101051.9+235850.2, that carries a chemical signature unlike anything else we’ve seen in the modern universe. Its footprint matches up with predictions of what the early universe’s supermassive stars might have looked like.