The telescope's infrared observations of the exoplanet, HIP 65426 b, were revealed Thursday (Sept. 1) in a paper posted to the preprint database arXiv (opens in new tab). The paper has not yet gone through peer review, but was discussed in a blog post on NASA’s website (opens in new tab).
The young planet is a "super-Jupiter," meaning it's a gas giant that's more massive than Jupiter — about six to eight times more massive, in fact. It orbits an A-type star about twice the size of the sun and around 349 light-years from Earth in the constellation Centaurus.
"This is a significant moment for a variety of reasons," Aarynn Carter, lead author and a postdoctoral researcher at the University of California, Santa Cruz, told Live Science. "Firstly, this is the first time we've ever imaged a planet beyond 5 microns” in wavelength.
Microns or micrometers is how scientists measure wavelengths of light in the electromagnetic spectrum. Infrared light has wavelengths longer than those of visible light and gains at begins at 0.75 microns. Unlike nay other space telescope, JWST can cover the 0.6 to 28 micrometer range. By comparison, the Hubble Space Telescope covers the infrared red only up to 2.5 microns while ground-based telescopes max-out at 2.2 microns. So JWST is giving astronomers a much wider view of objects than has previously been possible.
"We can cover the full luminous wavelength ranges of these objects and obtain tight constraints on their luminosity, and, in turn, other properties, such as mass, temperature and radius,” Carter said. That kind of detailed analysis will be published in the future, he said.
Astronomers observed HIP 65426 b using seven filters, each of which allows a specific wavelength of infrared light to pass through. The telescope's precision surprised them.
"The telescope is more sensitive than we expected, but it is also very stable,” Carter said. Carter's work showed that JWST is powerful enough to detect smaller exoplanets than have ever been visualized before.
"Previously we've been limited to detections of super-Jupiters, but now we have the potential to image objects similar to Uranus and Neptune for the right targets," Carter said.
Direct imaging of exoplanets is difficult because planets are easily lost in a star's glare. JWST blocks that glare using a disc called a coronagraph on both its Near-Infrared Camera and Mid-Infrared Instrument. HIP 65426 b was originally detected in July 2017 (opens in new tab) in short infrared wavelengths of light by scientists using the European Southern Observatory's Very Large Telescope (VLT) in Chile and was selected to test JWST's precision and to figure out how to best do direct imaging of exoplanets in mid-infrared light.
"We picked this star as we knew it had a well-established planet that would be ripe for direct imaging and would therefore be an outstanding first target to test the JWST coronagraphs," Sasha Hinkley, an associate professor in the Department of Physics & Astronomy at the University of Exeter and principal investigator for one of the 13 JWST Early Release Science Programs, told Live Science. JWST Early Release Science Programs in the first five months of JWST’s science operations are designed to give scientists immediate access to early data from specific science observations.
HIP 65426 b is easier to pick out from its host starlight because it is 100 times farther from its host star than Earth is from the sun, but it's still over 10,000 times fainter than its host star (opens in new tab) in the near-infrared.
"This is a particularly exciting beginning to this new era capturing photons directly from exoplanet atmospheres at totally new wavelengths that should last for the next 20 years or so," Hinkley said.
Originally published on Live Science.