A light curve from Webb’s Near-Infrared Imager and Slitless Spectrograph (NIRISS) shows the change in brightness of light from the WASP-96 star system over time as the planet transits the star. A transit occurs when an orbiting planet moves between the star and the telescope, blocking some of the light from the star. This observation was made using NIRISS’s Single-Object Slitless Spectroscopy (SOSS) mode, which involves capturing the spectrum of a single bright object, like the star WASP-96, in a field of view.  
 
To capture these data, Webb stared at the WASP-96 star system for 6 hours 23 minutes, beginning about 2½ hours before the transit and ending about 1½ hours after the transit was complete. The transit itself lasted for just under 2½ hours. The curve includes a total of 280 individual brightness measurements – one every 1.4 minutes.
 
Because the observation was made using a spectrograph, which spreads the light out into hundreds of individual wavelengths, each of the 280 points on the graph represents the combined brightness of thousands of wavelengths of infrared light.
 
The actual dimming caused by the planet is extremely small: The difference between the brightest and dimmest points is less than 1.5 percent. NIRISS is ideally suited for this observation because it has the ability to observe relatively bright targets over time, along with the sensitivity needed to measure such small differences in brightness: In this observation, the instrument was able to measure differences in brightness as small as 0.02 percent.
 
Although the presence, size, mass, and orbit of the planet had already been determined based on previous transit observations, this transit light curve can be used to confirm and refine existing measurements, such as the planet’s diameter, the timing of the transit, and the planet’s orbital properties.
 
WASP-96 b is a hot gas giant exoplanet that orbits a Sun-like star roughly 1,150 light years away, in the constellation Phoenix. The planet orbits extremely close to its star (less than 1/20th the distance between Earth and the Sun) and completes one orbit in less than 3½ Earth-days. The planet’s discovery, from ground-based observations, was announced in 2014.
 
The background illustration of WASP-96 b and its Sun-like star is based on current understanding of the planet from both NIRISS spectroscopy and previous ground- and space-based observations. Webb has not captured a direct image of the planet or its atmosphere.

The NASA/ESA/CSA Webb Telescope has yet another discovery machine aboard – the Near-Infrared Spectrograph’s (NIRSpec’s) microshutter array. This instrument has more than 248,000 tiny doors that can be individually opened to gather spectra (light) of up to approximately 150 individual objects simultaneously.
 
Of the thousands of distant galaxies behind galaxy cluster SMACS 0723, NIRSpec observed 48 individually – all at the same time – in a field that is approximately the size of a grain of sand held at arm’s length. Quick analysis made it immediately clear that several of these galaxies were observed as they existed at very early periods in the history of the universe, which is estimated to be 13.8 billion years old.
 
Look for the same feature highlighted in each spectrum. Three lines appear in the same order every time – one hydrogen line followed by two ionized oxygen lines. Where this pattern falls on each spectrum tells researchers the redshift of individual galaxies, revealing how long ago their light was emitted.
 
Light from the farthest galaxy shown traveled 13.1 billion years before Webb’s mirrors captured it. These observations mark the first time these particular emission lines have been seen at such immense distances – and these are only Webb’s initial observations. There may be even more distant galaxies in this image!
 
In these spectra, Webb has also shown us the chemical composition of galaxies in the very early Universe for the first time. This was made possible by the telescope’s position in space – far away from Earth’s atmosphere, which filters out some infrared light – and its specialization in gathering high-resolution near-infrared light.
 
And since similar spectra from galaxies at closer distances have long been studied by other space- and ground-based observatories, astronomers already know a lot about the properties of nearby galaxies. Now, astronomers will be able to study and compare spectra from Webb to determine how galaxies have changed over billions of years, dating back to the early Universe.
 
With Webb’s data, researchers can now measure each galaxy’s distance, temperature, gas density, and chemical composition. We will soon learn an incredible amount about galaxies that existed all across cosmic time!
 
Want to capture your own spectra with Webb’s microshutter array? Learn how scientists use the instrument by “taking” your own observations with this interactive and analyze the spectra it returns.

Want to go on a galactic treasure hunt? Data known as spectra from the NASA/ESA/CSA Webb Telescope make it easy to find – and match up – cosmic prizes!
 
At far left is a near-infrared image of galaxy cluster SMACS 0723. A group of massive galaxies below and to the right of the bright central star have distorted, magnified, and mirrored many galaxies in this field.
 
By quickly examining the image at left by eye, it becomes clearer that one arc may be made up of two similar looking galaxies. Their bright central regions match, despite their stretched appearances. These may be lensed galaxies – one galaxy that is mirrored in a second location. Are they the same? Researchers can’t be sure from the image alone – more data are needed to confirm a match.
 
Scientists do this by gathering spectra, which spread light out so they can fully examine an object’s makeup. Webb’s Near-Infrared Imager and Slitless Spectrograph (NIRISS), which gathers spectra of every object in any field it observes, was pointed at the galaxy cluster to gather more detail. A segment of the NIRISS grism image (an instrument that has a grating, or stair steps, on a prism), at centre, shows how ionized oxygen and atomic hydrogen emission lines are distributed along the arc.
 
Next, the spectra from each of these two galaxies were plotted as graphs, shown at right, to reveal their compositions. The graphs, known as spectra, match, which indicates that these arcs are mirror images of the same galaxy. Webb’s spectra from NIRISS also quickly proved that light from both galaxies was emitted 9.3 billion years ago, further confirming they are one and the same.
 
Using Webb’s NIRISS is like opening a treasure chest overflowing with spectra. For example, this instrument can disperse the spectra along the image vertically and horizontally. Researchers can use both modes to untangle which lines match each source.
 
Every object’s image can be transformed into spectra like the two shown above. So even if researchers aren’t intending to study a particular galaxy in the field, they may make a surprise discovery.

This galaxy emitted its light 13.1 billion years ago.
 
It was captured by Webb’s microshutter array, part of its Near-Infrared Spectrograph (NIRSpec). This instrument is so sensitive that it can observe the light of individual galaxies that existed in the very early Universe. This will prove transformational for research. Webb’s capabilities have allowed scientists to observe spectra of galaxies this far away for the first time.
 
When researchers stretch out the light of an individual galaxy into a spectrum, like the graph shown above, they can learn about the chemical composition, temperature, and density of the galaxy’s ionized gas. For example, this galaxy’s spectrum will reveal the properties of its gas, which will indicate how its stars are forming and how much dust it contains. These data are rich – and have never before been detected from this far away at this quality.
 
As astronomers begin analyzing Webb’s data, we will learn an incredible amount about galaxies that existed all across cosmic time – and how they compare to the beautiful spiral and elliptical galaxies in the nearby Universe.
 
Want to capture your own spectra with Webb’s microshutter array? Learn how scientists use the instrument by “taking” your own observations in this interactive and analyze the spectra it returns.

These side by side views of the Southern Ring Nebula were captured in different wavelengths by the James Webb Space Telescope's Near Infrared Camera (left) and Mid Infrared Instrument (right).
 
The planetary nebula is located 2,500 light-years from Earth.