In space astronomy, it’s what’s under the hood that matters.
And for Webb, who is about to complete the final stages of commissioning its 17 science instrument modes, a device designed specifically for capturing images & spectra of various types of cosmic objects has the potential to go beyond detecting where alien world may lie.
The Canadian-built scienctific instrument, called Near Infrared Imager & Slitless Spectrograph (NIRISS), could detect signals from Earth 2.0 simply by looking at a viable candidate’s host star.
Canada’s contribution to JSWT
Crucially, the NIRISS instrument will capably probe universal near-infrared phenomena “at wavelengths down to 5.0 microns,” said Nathalie Ourellette of the Université de Montréal in a blog post on NASA’s website. “The NIRISS team has developed 4 instrument modes to collect different types of data suitable for different scientific goals and objectives.
NIRISS’ SOSS mode will allow the James Webb Space Telescope (JWST) to collect high-precision spectra “one bright object at a time,” Ourellette added in the post. “This mode is optimized for time-series observations, which are ideal for studying a phenomenon that changes during an observation that typically lasts an hour, such as exoplanet transiting in front of its host star.”
“Using a technique called transit spectroscopy, the NIRISS instrument can collect a spectrum of an exoplanet’s atmosphere containing various makers that allow astronomers to determine its composition, temperature, potential habitability signatures, and other important features,” Ourellette explained in the blog post. .
Then there’s the WFSS mode, which allows NIRISS to help Webb gather information from 1000s of objects, “like galaxies, simultaneously across the detector’s entire field of view,” which Ourellette says is 4.84 square arc minutes. The spectra of thousands of galaxies will make it possible to measure their distances, ages and other physical parameters to track how galaxies evolve over the life-time of the Universe.
And there’s more. NIRISS is able to collect information from many spectra simultaneously in WFSS mode, which means that discrete spectra can overlap (if the light sources are too close together from our point of view). “So there are 2 orthogonal grisms, GR150C & GR150R, that can generate horizontal & vertical spectra, respectively, that helps unravel combined spectra from different galaxies,” Ourellette said.
Webb NIRISS could reveal new alien worlds with habitable conditions
In addition, NIRISS’ AMI mode will allow Webb to study cosmic objects that are very close (from our point of view, of course). This is done using a special technique known as interferometry. A mask inside the instrument only allows light to pass from certain parts of the primary mirror,” Ourellette explained. “Astronomers can increase the resolution of the telescope by a factor of almost 2.5 by looking closely at the patterns created as carefully chosen beams-of-light interfere with each other.
By using this method, two objects that appear very close apparent proximity can appear as 2 distinct points of light rather than a meaningless blur. However, since the mask blocks a lot of light, the observed cosmic objects have to be quite bright for them to be detected. But given enough brightness, the NIRISS instrument’s AMI mode will allow the JWST to observe brown dwarfs, protoplanetary disks and even exoplanets. It’s the first time we’ve used such a method to-set our eyes on extraterrestrial worlds, and it’s just a small part of the wealth of scientific knowledge that awaits you when Webb embarks its scientific missions in earnest this summer.