New Webb images reveal the space telescope’s first exoplanet, first brown dwarf, and a stellar nursery teeming with activity.
Over the past week, the James Webb Space Telescope has captured both its first exoplanet and its first brown dwarf as well as photographed the firestorm of star formation in the Tarantula Nebula. Though all three celestial objects have been studied before, Webb provides details astronomers can’t get anywhere else.
Late last week, the Webb team released its first image of an exoplanet, a gas giant known as HIP 6542 b. It’s nothing like the giants in our solar system, with a mass between 6 and 12 times that of Jupiter and a distance from its host star that’s 10 times farther out.
Stars shine less brilliantly at infrared wavelengths, but even so this planet was still 10,000 times fainter than its star. Webb’s cameras have coronagraphs that help out by blocking the star’s brilliance. It also helps that the system is young, only 15 to 20 million years old, so the planet itself is still glowing from the heat of its formation.
“Obtaining this image felt like digging for space treasure,” says Aarynn Carter (University of California, Santa Cruz), who led the image analysis. “At first all I could see was light from the star, but with careful image processing I was able to remove that light and uncover the planet.”
Carter and his colleagues are now preparing a publication on their analysis for submission to a peer-reviewed journal.
The Brown Dwarf
In another first announced this week, Webb has observed its first brown dwarf, designated VHS 1256-1257 b, 72 light-years away in the constellation Corvus. This in-betweener is between 14 and 24 times Jupiter’s mass, so it’s a bit too big to be a planet but not massive enough to ignite longlasting fusion in its core. Like the exoplanet above, this system is also young at 200 million years old.
Webb took a spectrum of this world, revealing the chemical elements that make up what was previously seen to be a reddish atmosphere. The infrared spectrum, which spans 1 to 20 microns, shows evidence for methane, sodium, potassium, water, and carbon dioxide, as well as a thick layers of silicate clouds.
Brittany Miles (University of California, Santa Cruz) and colleagues have posted their study on the arXiv preprint server, but it has not yet undergone peer review.
The Tarantula Nebula, also known as 30 Doradus, hosts the fiercest star formation in the Local Group of galaxies around the Milky Way. But it’s also fundamentally different from other nearby stellar nurseries, because its chemical composition shows a relative lack of “pollution” from the heavier elements that stars forge in their cores. In other words, this star-formation region acts like one in a far younger universe, and it has long captured astronomers’ attention for that reason.
The new and forming stars burn 161,000 light-years away in the Large Magellanic Cloud, the largest satellite galaxy of the Milky Way, and received its name from the spider-leg clouds seen in visible observations. But infrared images reveal something different.
Massive young stars, shining like sapphires in the center, blow out a cavity in the surrounding dust-and-gas cloud that gave them birth. Denser parts of this cloud have resisted the young stars’ push and were shaped instead into pillars pointing toward the center. At infrared wavelengths, Webb reveals the protostars hidden within these pillars. For now, they are biding their time, gaining mass. Once these infant stars “turn on,” igniting nuclear fusion in their cores, their shine will push out the surrounding gas, changing the nebula’s shape.