The James Webb Space Telescope was developed to allow us to see the cosmos in a new way — with much greater precision, using infrared wavelengths to piece through dust around galaxies, stars and planets, and to look further back into time and space.
In the less than four months since the first Webb images were released, the pioneering telescope has certainly shown us a remarkable range of abilities. And as a result, we’ve been treated to some dazzling new views of the solar system, the galaxy and beyond. This is just the beginning and we thankfully have years to come of new images and the scientific insights that come with them.
Just as the Hubble Space Telescope, with its 32 years of service and counting, ushered in a new era of space imagining and understanding, so too is the Webb telescope revolutionizing how we see and understand our world writ large. Very large.
The differences between the Webb’s image and previous images of Neptune are certainly dramatic, in terms of color, precision and what they tell us about the planet.
Surely most striking in Webb’s new image is the crisp view of the planet’s rings, some of which have not been seen since NASA’s Voyager 2 became the first spacecraft to observe Neptune during its flyby in 1989. In addition to several bright, narrow rings, the Webb image clearly shows Neptune’s fainter, never-seen dust bands as well.
Neptune is an ice giant planet. Unlike Jupiter and Saturn, which consist primarily of hydrogen and helium, Neptune has an interior that is much richer in heavier elements (“heavier is the sense of not hydrogen or helium.) One of the most abundant heavy molecules is methane, which appears blue in Hubble’s visible wavelengths but largely white in the Webb’s near-infrared camera.
Methane so strongly absorbs red and infrared light that the planet would be quite dark at near-infrared wavelengths were it not for its high-altitude clouds, which reflect sunlight. These methane-ice clouds are also prominent in Webb’s image as bright streaks and spots.
More subtly, a thin line of brightness captured by the telescope’s Near Infrared Camera (NIRcam,) Webb’s primary imager, circling the planet’s equator could be a visual signature of global atmospheric circulation that powers Neptune’s winds and storms.
The blue coloring of Neptune as imaged by the Hubble is the result of the absorption of red light by that methane-rich atmosphere, combined with the same Rayleigh-scattering process that makes the Earth’s sky blue. (Rayleigh scattering refers to the bouncing of light off molecules in the air, and can be extended to scattering from particles up to about a tenth of the wavelength of the light.)
While the JWST was initially designed primarily to look deep into space, to the earliest stages of our universe, it was later given the additional task of examining and characterizing the atmospheres of exoplanets. This exoplanet, 385 light-years from Earth, was the first to be imaged by the telescope and its cameras.
Called HIP 65426 b, it is a young gas giant exoplanet. The size of 1.5 Jupiters with the mass of 9 Jupiters, it was discovered in 2017 and it takes 631 years to complete one orbit of its star.
The image, as seen through four different light filters, shows how Webb’s infrared receptors can capture worlds beyond our solar system — very promising for the broad scientific effort to characterize exoplanets.
But taking direct images of exoplanets, as done here, is challenging because stars are so much brighter than planets. The HIP 65426 b planet is more than 10,000 times fainter than its host star in the near-infrared, and a few thousand times fainter in the mid-infrared.
In each filter image, the planet appears as a slightly differently shaped blob of light. That is because of the particulars of Webb’s optical system and how it translates light through the different optics.
“Obtaining this image felt like digging for space treasure,” said Aarynn Carter, a postdoctoral researcher at the University of California, Santa Cruz, who led the analysis of the images.
“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.”
A major goal of the JWST mission is to identify the chemical components of the atmospheres of exoplanets. Being able to characterize distant atmospheres is considered a major step forward in the effort to understand how planets and solar systems form, what planets might be habitable, and eventually perhaps what planets support biology on them.
These spectra from the atmospheres of Mars and WASP 96b are some the items featured in the early science release program of the JWST. The program focuses on well-known planets and is looking for scientific surprises. But the effort, which includes observations by scores of teams, is also designed to explore the capabilities of the telescope and, in that way, help a larger group of scientists to successfully propose future viewing campaigns.
The spectrum of Mars did not reveal anything particularly new — other than the ability of JWST spectrographs to read atmospheric chemical compositions of planets much closer than the distant ones the telescope was designed to characterize.
Mars is one of the brightest objects in the night sky in terms of both visible light (which human eyes can see) and the infrared light that Webb is designed to detect. Webb’s instruments are so sensitive that without special observing techniques, the bright infrared light from Mars is blinding, causing a phenomenon known as “detector saturation.”
But the spectra of WASP- 96b was of greater scientific interest.
While the light curve released confirms properties of the planet that had already been determined from other observations – the existence, size, and orbit of the planet – the Webb transit spectrum revealed previously hidden details of the atmosphere. They include the unambiguous signature of water, indications of haze, and evidence of clouds that were thought not to exist based on prior observations.
WASP-96b is 1,150 light-years away and orbits its Sun-like star every 3.5 Earth days at a distance just one-ninth of the distance between Mercury and the Sun. So this is not a planet being studied for habitability but rather for the chemical makeup of its atmosphere and to learn how best to use the JWST spectrographs.
The chemical compositions are identified via spectrum, which are created when light is split into a rainbow of colors. When Webb observes the light of a star, filtered through the atmosphere of its planet, its spectrographs split up the light into that rainbow. By analyzing that light, scientists can look for the characteristic signatures of specific elements or molecules in the spectrum.
WASP-96b represents a type of gas giant that has no direct analog in our solar system. With a mass less than half that of Jupiter and a diameter 1.2 times greater, WASP-96 b is much puffier than any planet orbiting our Sun. And with a temperature greater than 1000°F, it is significantly hotter.
The observation is the most detailed of its kind to date and demonstrates Webb’s ability to analyze atmospheres in depth hundreds of light-years away — an unprecedented capability.
Stephan’s Quintet is a visual grouping of five galaxies located about 290 million light-years away.
Tight galaxy groups like this that interact constantly may have been more common in the early universe when their superheated, infalling material may have fueled very energetic black holes called quasars. Even today, the topmost galaxy in this group – NGC 7319 – harbors an active galactic nucleus, a supermassive black hole 24 million times the mass of the Sun. It is actively pulling in material and puts out light energy equivalent to 40 billion Suns.
Scientists using the spectrometer capability of Webb’s MIRI insrument studied the active galactic nucleus in great detail with integral field units (IFUs) – a combination of a camera and spectrograph. These IFUs provided the Webb team with a “data cube,” or collection of images of the galactic core’s spectral features.
Using IFUs, scientists can measure spatial structures, determine the velocity of those structures, and get a full range of spectral data. Much like medical magnetic resonance imaging (MRI), the IFUs allow scientists to “slice and dice” the information into many images for detailed study.
When a supermassive black hole feeds, some of the infalling material becomes very hot and is pushed away from the black hole in the form of winds, jets and radiation.
MIRI’s MRS pierced through the shroud of dust near that active galactic nucleus to measure the emission of hot and bright gases created by ionized matter (split into sub-atomic parts.) The instrument saw the gas near the supermassive black hole at a level of detail never seen before, and it was able to determine its composition.
MIRI probed many different regions, including the black hole’s outflowing wind – indicated by the smaller circle – and the area immediately around the black hole itself – indicated by the larger circle. It showed that the black hole is shrouded in silicate dust similar to beach sand, but with much smaller grains.
We’ll finish up — for now — with a lustrous image of a star-forming region and a remarkably crisp view of Jupiter.
A parting description from NASA about how these images go from telescope to you:
Data from telescopes like Webb doesn’t arrive on Earth neatly packaged. Instead, it contains information about the brightness of the light on Webb’s detectors. This information arrives at the Space Telescope Science Institute (STScI), Webb’s mission and science operations center, as raw data. STScI processes the data into calibrated files for scientific analysis and delivers it to the Mikulski Archive for Space Telescopes for dissemination.
Scientists then translate that information into images like these during the course of their research (here’s a podcast about that). While a team at STScI formally processes Webb images for official release, non-professional astronomers known as citizen scientists often dive into the public data archive to retrieve and process images, too.