Webb’s First Images
Unveiling the mystery behind the first science quality images from the James Webb Space Telescope (JWST).
On 12 July 2022 the first science images from Webb were released following a preview of the first deep field image released by US President Joe Biden the night before. These images and spectra are a game changer and will allow astronomers and scientists to probe our universe’s deepest and darkest secrets even better. Below, we explore why these images are so great and what promises Webb holds in store for the future of infrared astronomy.
You can also find out more about this revolutionary telescope in our blog about the James Webb Space Telescope.
Carina Nebula – star birth
The Carina Nebula (also known as the Eta Carinae Nebula) is a huge cloud of gas and dust in the constellation of Carina, which is located in the Carina–Sagittarius Arm of the Milky Way galaxy.
This small section captures part of a stellar nursery called NGC 3324 located in the northwest corner of the Carina Nebula. It reveals many more stars that were previously hidden by the thick clouds of dust. Those stars, out of reach from even Hubble’s gaze, take to the stage here thanks to Webb’s longer wavelength infrared observations.
High energy ultraviolet radiation from the newly formed stars sculpt the nebula’s wall acting to erode it away. Resisting the radiation, we see tall pillars above the bright wall of gas. The smoky plumes appearing to rise from the ‘mountain tops’ is actually hot dust and ionised gas – the stellar radiation causing it to stream away from the nebula.
Because Webb observes in the infrared, the data it captures would be invisible to us. Scientists construct false colour images like this by assigning distinct colours to the different wavelengths of light observed. Typically longer wavelength infrared light is depicted with reddish hues and the shorter wavelength infrared light is shown as bluer colours instead.
SMACS 0723 – deepest view of the distant universe
SMACS 0723 is a galaxy cluster – a collection of gravitationally bound galaxies which can be seen as the bright glow at the centre of this image. In the foreground and background are numerous other galaxies caught in this tiny speck of the sky – a point the size of a grain of sand held at arm’s length.
Whilst the image may draw resemblance to the iconic Hubble Deep Field image, the Hubble Space Telescope spent two weeks collecting light to produce its deepest look into the universe. In contrast this first composite image from Webb is the product of light being collected for just 12.5 hours and yet the level of detail is incomparable.
The gravitational pull from the galaxy cluster at the centre is so immense that the light from galaxies beyond it are bent around – their light magnified and seen as arcs. Foreground stars shine bright with an eight-pointed spike pattern – an artefact of the shape of Webb’s hexagonal mirrors and struts holding the secondary mirror in place.
Among the many other points of light are high redshift galaxies – those that are so distant and moving away from us (seen as deep red objects). Their light has been stretched from visible light into longer wavelength, invisible infrared light. But Webb’s infrared capabilities allow us to observe these never-before-seen galaxies that existed at the beginning of our universe.
Southern Ring nebula – star death
Shells of gas and dust are expelled into space in this dying star’s final performance. At the centre is the remnant of the star known as a white dwarf.
And while it appears partially hidden by the diffraction spike of its companion star in the image taken by Webb’s NIRCam (which observes shorter infrared wavelengths), when the nebula is observed in longer mid infrared wavelengths by Webb’s MIRI instrument, it appears brighter, larger, and redder – seen to the lower left. Why? Because the white dwarf is shrouded in thick layers of dust which Webb was able to capture for the first time. At this final stage, the white dwarf should have shed its final layers so researchers will soon begin to pursue explanations for this unexpected case.
As the star became a white dwarf, it periodically ejected mass giving rise to the shells of material seen in the image.
In both images a line appears towards the edge of the nebula towards the top left. Initially thought to be a part of the nebula – it turns out that it’s a distant galaxy being seen edge-on, such that we’re looking along its disc and it therefore appears line-like. And the background also offers further insights too – most of those points are not stars, they are distant galaxies.
Stephan’s Quintet – interacting galaxies
These five galaxies appear in the sky together, however the leftmost is a foreground galaxy some 40 million lightyears from us and astonishingly Webb resolved individual stars and even the galaxy’s bright core. The remaining four form the first compact group of galaxies ever discovered which lie 290 million light years distant. Stephan’s Quintet is one of the most studied of all compact galaxy groups.
The topmost galaxy NGC 7319 has an active galactic nucleus (AGN) driven by a supermassive black hole at the centre, 24 million times the mass of our Sun, accreting surrounding material. Webb’s instruments were able to see through the dust veiling the black hole to reveal the strikingly bright AGN. Webb probed the hot gas near the active black hole and measured the velocity of the bright outflows driven by it at a level of detail greater than ever achieved before.
Scientists will now be able to start understanding how quickly supermassive black holes feed and grow. And it’s rare that scientists are able to see in great detail how interacting galaxies trigger star formation in each other, and how these processes also disturb the gas in these galaxies – Webb is making this a reality.
WASP-96 b – water in an exoplanet’s atmosphere
Earlier in 2022, NASA confirmed the detection of the 5000th exoplanet and more continue to be found. But these planets beyond our solar system, circling distant stars are usually too dim, too small, and so far away that it’s pretty difficult to detect them let alone probe their atmospheres.
Astronomers have been eagerly awaiting Webb’s launch as it has the sensitivity to characterise the compositions of exoplanet atmospheres – something beyond the limits of other current telescopes. As an exoplanet passes in front of its star (known as a transit) starlight travels through its atmosphere before it arrives at Earth and different elements and molecules present within it will absorb certain wavelengths of light – essentially producing a fingerprint or barcode, a technique known as spectroscopy.
Targeting a hot gas giant planet (WASP-96 b) orbiting a Sun-like star, Webb has captured the distinct ‘fingerprint’ of water, and evidence to suggest it has clouds and haze in the atmosphere too. In the search for finding Earth-like exoplanets, Webb’s ability to see what the atmospheres of these distant worlds are made of, will be a huge step in narrowing down some viable suspects.
Jupiter – bonus images
Included in NASA’s commissioning document were these informal and lower resolution images of Jupiter. Taken during a test of the telescope, these 75-second exposure images showcase Webb’s ability to track moving objects like planets using NIRCam which observes short wavelength infrared light.
The image on the left taken using NIRCam shows the bands across the planet and three of its moons: Metis, Thebe, and Europa – the latter whose shadow can be seen to the left of the Great Red Spot (towards the right).
In comparison the long-wavelength image on the right, shows the stark difference in atmospheric conditions that Webb is and will be able to see.
About the author: Dhara Patel is a Space Expert at the National Space Centre.