It is no exaggeration to say that the James Webb Space Telescope (JWST) represents a new era for modern astronomy.
Launched on December 25 of last year and fully operational since July, the telescope offers views of the universe that were previously inaccessible to us. Like the Hubble Space Telescope, the JWST is in space, so it can take pictures in stunning detail without the distortions of Earth’s atmosphere.
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However, while Hubble is orbiting Earth at an altitude of 540 km, JWST is 1.5 million kilometers away, far beyond the Moon. From this position, away from the interference of reflected heat from our planet, it can collect light from across the universe into the infrared part of the electromagnetic spectrum.
This capability, when combined with JWST’s largest mirror, state-of-the-art detectors and many other technological advances, allows astronomers to peer back into the earliest times of the universe.
The star-forming region of Carina imaged by the JWST. NASA
As the universe expands, it stretches the wavelength of light traveling toward us, making more distant objects appear redder. At large enough distances, the light from a galaxy shifts completely out of the visible part of the electromagnetic spectrum into the infrared. The JWST is able to probe these light sources from the earliest times, almost 14 billion years ago.
The Hubble telescope remains a great scientific instrument and can see at optical wavelengths where the JWST cannot. But the Webb telescope can see far beyond the infrared with greater sensitivity and sharpness.
Let’s take a look at ten images that have demonstrated the awesome power of this new window into the universe.
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1. Mirror alignment is complete
Left: The first published alignment image of the JWST. Astronomers pounced on this image to compare it to earlier images of the same part of the sky as the one on the right from the Dark Energy Camera on Earth. NASA/STScI/LegacySurvey/C. Jacobs
Despite years of field testing, an observatory as complex as JWST required extensive setup and testing once deployed in the cold and dark of space.
One of the most important tasks was getting the 18 hexagonal mirror segments to unfold and align to a fraction of the wavelength of light. In March, NASA released the first image (centered on a star) of the fully aligned mirror. Although it was only a calibration image, astronomers immediately compared it to existing images of that patch of sky, with great excitement.
2. Spitzer vs MIRI
This image shows part of the ‘Pillars of Creation’ in infrared (see below); on the left taken with the Spitzer Space Telescope, and JWST on the right. The contrast in depth and resolution is spectacular. NASA/JPL-Caltech (left), NASA/ESA/CSA/STScI (right)
This initial image, taken while all cameras were in focus, clearly demonstrates the step change in data quality that JWST brings to its predecessors.
On the left is an image of the Spitzer Telescope, an infrared observatory in space with an 85 cm mirror; right, the same field from JWST’s MIRI 6.5 m mirror and mid-infrared camera. The resolution and ability to detect much fainter sources is shown here, with hundreds of galaxies visible that were lost in the noise of the Spitzer image. This is what a larger mirror placed in the deepest, coldest darkness can do.
3. The first image of the galaxy cluster
Galaxy cluster SMACS 0723: from Hubble on the left and JWST on the right. Hundreds more galaxies are visible in JWST’s infrared image. NASA/STSci
The galaxy cluster with the prosaic name of SMACS J0723.3–7327 was a good choice for the first color images released to the public from the JWST.
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The field is full of galaxies of all shapes and colors. The combined mass of this huge cluster of galaxies, more than 4 billion light-years away, bends space in such a way that light from distant sources in the background is stretched and magnified, an effect known as lensing gravitational
These distorted background galaxies can clearly be seen as lines and arcs throughout this image. The field is already spectacular in the Hubble images (left), but the JWST near-infrared image (right) reveals a wealth of additional detail, including hundreds of distant galaxies too faint or too red to be detected by its predecessor .
4. Stephan’s Quintet
Hubble (l) and JWST (r) images of the group of galaxies known as ‘Stephan’s Quintet’. The inset shows a zoom in on a distant background galaxy. NASA/STScI
These images depict a spectacular group of galaxies known as Stephan’s Quintet, a group that has long been of interest to astronomers who study the way colliding galaxies interact with each other gravitationally.
On the left we see the Hubble view and on the right the JWST mid-infrared view. The inset shows the power of the new telescope, zoomed in on a small background galaxy. In the Hubble image we see some bright regions of star formation, but only with the JWST is the full structure of this and the surrounding galaxies revealed.
5. The pillars of creation
The “Pillars of Creation,” a star-forming region in our galaxy, captured by Hubble (left) and JWST (right). NASA, ESA, CSA, STScI; Joseph DePasquale (STScI), Anton M. Koekemoer (STScI), Alyssa Pagan (STScI)
The so-called Pillars of Creation is one of the most famous images in all of astronomy, taken by Hubble in 1995. It demonstrated the extraordinary reach of a space telescope.
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It depicts a star-forming region in the Eagle Nebula, where interstellar gas and dust provide the backdrop for a stellar nursery full of new stars. The image on the right, taken with JWST’s Near Infrared Camera (NIRCam), demonstrates another advantage of infrared astronomy: the ability to look through the dust layer and see what’s inside and behind it.
6. The ‘hourglass’ protostar
The “hourglass protostar,” a star still in the process of accreting enough gas to begin fusing hydrogen. Inset: A much lower resolution view from Spitzer. NASA/STScI/JPL-Caltech/A. tobin
This image represents another act of galactic creation within the Milky Way. This hourglass-shaped structure is a cloud of dust and gas surrounding a star in the process of formation: a protostar called L1527.
Only visible in the infrared, an “accretion disk” of infalling material (the black band in the center) will eventually allow the protostar to gather enough mass to begin fusing hydrogen and a new star will be born.
Meanwhile, light from the still-forming star illuminates the gas above and below the disk, giving it an hourglass shape. Our previous view of this came from Spitzer; the amount of detail is once again a huge leap forward.
7. Jupiter in infrared
An infrared view of Jupiter from the JWST. Notice the auroral glow at the poles; this is caused by the interaction of charged particles from the sun with Jupiter’s magnetic field. NASA/STScI
The Webb Telescope mission includes imaging the most distant galaxies since the beginning of the universe, but it may also look a little closer to home.
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Although JWST cannot look at Earth or the inner planets of the Solar System, since it must always look outward from the Sun, it can look out into the most distant parts of our Solar System. This near-infrared image of Jupiter is a beautiful example, as we look deep into the structure of the gas giant’s clouds and storms. The glow of the auroras at both the north and south poles is haunting.
This image was extremely difficult to obtain because of Jupiter’s rapid movement across the sky relative to the stars and its rapid rotation. The success demonstrated the Webb Telescope’s ability to track difficult astronomical targets extremely well.
8. The ghost galaxy
Hubble visible light (l), JWST infrared (r) and combined images (middle) of the ‘Phantom Galaxy’ M74. The ability to combine visible light information about stars with infrared images of gas and dust allows us to probe these galaxies in exquisite detail. ESA/NASA
These images of the so-called Phantom Galaxy, or M74, reveal JWST’s power not only as the latest and greatest in astronomical instruments, but as a valuable complement to other great tools. The center panel here combines Hubble’s visible light with Webb’s infrared, allowing us to see how starlight (via Hubble) and gas and dust (via JWST) shape this remarkable galaxy.
Much of the JWST science is designed to be combined with Hubble’s optical views and other images to take advantage of this principle.
9. A super distant galaxy
A “closer” to a galaxy from one of the earliest epochs in the universe, when the universe was only about 300 million years old (the small red source visible in the center of the right panel). Galaxies at this distance are impossible to detect in visible light because their emitted radiation has been “redshifted” into the infrared. NASA/STScI/C. Jacobs
Although this galaxy, the little red blob in the right image, is not among the most spectacular that our universe has to offer, it is just as interesting scientifically.
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This snapshot is from when the universe was only 350 million years old, making it one of the earliest galaxies to form. Understanding the details of how these galaxies grow and merge to create galaxies like our own Milky Way 13 billion years later is a key question, and with many mysteries remaining, making discoveries like this highly sought after.
It is also a view that only the JWST can achieve. Little did astronomers know…