Astronomers have used JWST's interferometric mode to analyze the extrasolar system PDS 70. (Image credit: Blakely et al., 2024, CC BY 4.0)
Planets form in spiral disks of gas and dust surrounding young stars. Astronomers are keenly interested in the process of planet formation, and understanding it is one of the key scientific goals of the James Webb Space Telescope (JWST). PDS 70 is a nearby star in whose disk two infant planets are forming, some of the few exoplanets that astronomers have been able to directly observe.
Researchers have developed a new, innovative method for observing PDS 70 with JWST and have revealed additional details about the system, including the possible presence of a third planet.
PDS 70 is an orange dwarf star located approximately 370 light years from Earth that has two young developing planets: PDS 70b and PDS 70c. The European Southern Observatory's Very Large Telescope (VLT) was able to directly image both planets, with PDS 70b being unique in that it is the first protoplanet to be captured in an image. The VLT achieved this feat in 2018 using its groundbreaking SPHERE instrument.
SPHERE observations, combined with other studies, have allowed astronomers to obtain more detailed information about the planets' atmospheres, masses, and temperatures.
Now, JWST has once again observed the pair of young planets. The results are published in a new paper in The Astronomical Journal. It’s called “James Webb Interferometer: Cosmic Interferometric Discoveries of PDS 70 b and c at 4.8 µm,” and the lead author is Dori Blakely. Blakely is a PhD student in physics and astronomy at the University of Victoria, British Columbia, Canada.
JWST's Near Infrared Imager and Slitless Spectrograph (NIRISS) has a feature known as aperture masked interferometry (AMI), which allows it to act as an interferometer. It uses a special mask with tiny holes over the telescope's primary mirror. The interferogram produced by this method has a much higher resolution because the effective size of the telescope is much larger.
“In this paper, we present James Webb Interferometer observations of PDS 70 with the NIRISS F480M filter, which are the first space-based interferometric observations of this system,” the authors report. They found evidence of material around PDS 70 b and c, supporting the theory that the planets are still in the process of formation.
“It's like looking at a family photograph of our solar system in its early days. It's amazing how much we can learn from one system,” lead study author Blakely said in a press release.
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