NASA’s James Webb Space Telescope has delivered the deepest and sharpest infrared image of the distant universe so far. Webb’s First Deep Field is galaxy cluster SMACS 0723, and it is teeming with thousands of galaxies – including the faintest objects ever observed in the infrared.
Webb’s image is approximately the size of a grain of sand held at arm’s length, a tiny sliver of the vast universe. The combined mass of this galaxy cluster acts as a gravitational lens, magnifying more distant galaxies, including some seen when the universe was less than a billion years old. This deep field, taken by Webb’s Near-Infrared Camera (NIRCam), is a composite made from images at different wavelengths, totaling 12.5 hours – achieving depths at infrared wavelengths beyond the Hubble Space Telescope’s deepest fields, which took weeks. And this is only the beginning. Researchers will continue to use Webb to take longer exposures, revealing more of our vast universe.
This image shows the galaxy cluster SMACS 0723 as it appeared 4.6 billion years ago, with many more galaxies in front of and behind the cluster. Much more about this cluster will be revealed as researchers begin digging into Webb’s data. This field was also imaged by Webb’s Mid-Infrared Instrument (MIRI), which observes mid-infrared light.
Webb’s NIRCam has brought distant galaxies into sharp focus – they have tiny, faint structures that have never been seen before, including star clusters and diffuse features.
Light from these galaxies took billions of years to reach us. We are looking back in time to within a billion years after the big bang when viewing the youngest galaxies in this field. The light was stretched by the expansion of the universe to infrared wavelengths that Webb was designed to observe. Researchers will soon begin to learn more about the galaxies’ masses, ages, histories, and compositions.
Other features include the prominent arcs in this field. The powerful gravitational field of a galaxy cluster can bend the light rays from more distant galaxies behind it, just as a magnifying glass bends and warps images. Stars are also captured with prominent diffraction spikes, as they appear brighter at shorter wavelengths.
Webb’s MIRI image offers a kaleidoscope of colors and highlights where the dust is – a major ingredient for star formation, and ultimately life itself. Blue galaxies contain stars, but very little dust. The red objects in this field are enshrouded in thick layers of dust. Green galaxies are populated with hydrocarbons and other chemical compounds. Researchers will be able to use data like these to understand how galaxies form, grow, and merge with each other, and in some cases why they stop forming stars altogether.
In addition to taking images, two of Webb’s instruments also obtained spectra – data that reveal objects’ physical and chemical properties that will help researchers identify many more details about distant galaxies in this field. Webb’s Near Infrared Spectrograph (NIRSpec) microshutter array observed 48 individual galaxies at the same time – a new technology used for the first time in space – returning a full suite of details about each. The data revealed light from one galaxy that traveled for 13.1 billion years before Webb’s mirrors captured it. NIRSpec data also demonstrate how detailed galaxy spectra will be with Webb observations.
Finally, Webb’s Near-Infrared Imager and Slitless Spectrograph (NIRISS) used Wide-Field Slitless Spectroscopy to capture spectra of all the objects in the entire field of view at once. Among the results, it proves that one of the galaxies has a mirror image.
SMACS 0723 can be viewed near the constellation Volans in the southern sky.
Beautiful spiral galaxy Messier 74 (also known as NGC 628) lies some 32 million light-years away toward the constellation Pisces. An island universe of about 100 billion stars with two prominent spiral arms, M74 has long been admired by astronomers as a perfect example of a grand-design spiral galaxy. M74’s central region is brought into a stunning, sharp focus in this recently processed image using publicly available data from the James Webb Space Telescope. The colorized combination of image data sets is from two of Webb’s instruments NIRcam and MIRI, operating at near- and mid-infrared wavelengths. It reveals cooler stars and dusty structures in the grand-design spiral galaxy only hinted at in previous space-based views.
Why does Jupiter have rings? Jupiter’s main ring was discovered in 1979 by NASA’s passing Voyager 1 spacecraft, but its origin was then a mystery. Data from NASA’s Galileo spacecraft that orbited Jupiter from 1995 to 2003, however, confirmed the hypothesis that this ring was created by meteoroid impacts on small nearby moons. As a small meteoroid strikes tiny Metis, for example, it will bore into the moon, vaporize, and explode dirt and dust off into a Jovian orbit. The featured image of Jupiter in infrared light by the James Webb Space Telescope shows not only Jupiter and its clouds, but this ring as well. Also visible is Jupiter’s Great Red Spot (GRS) — in comparatively light color on the right, Jupiter’s large moon Europa — in the center of diffraction spikes on the left, and Europa’s shadow — next to the GRS. Several features in the image are not yet well understood, including the seemingly separated cloud layer on Jupiter’s right limb.
OK, but why can’t you combine images from Webb and Hubble? You can, and today’s featured image shows one impressive result. Although the recently launched James Webb Space Telescope (Webb) has a larger mirror than Hubble, it specializes in infrared light and can’t see blue — only up to about orange. Conversely, the Hubble Space Telescope (Hubble) has a smaller mirror than Webb and can’t see as far into the infrared as Webb, but can image not only blue light but even ultraviolet. Therefore, Webb and Hubble data can be combined to create images across a wider variety of colors. The featured image of four galaxies from Stephan’s Quintet shows Webb images as red and also includes images taken by Japan’s ground-based Subaru telescope in Hawaii. Because image data for Webb, Hubble, and Subaru are made freely available, anyone around the world can process it themselves, and even create intriguing and scientifically useful multi-observatory montages.
The James Webb Space Telescope (JWST) is a space telescope designed primarily to conduct infrared astronomy. As the largest optical telescope in space, its high infrared resolution and sensitivity allow it to view objects too early, distant, or faint for the Hubble Space Telescope. This is expected to enable a broad range of investigations across the fields of astronomy and cosmology, such as observation of the first stars and the formation of the first galaxies, and detailed atmospheric characterization of potentially habitable exoplanets.
The U.S. National Aeronautics and Space Administration (NASA) led JWST’s development, and collaborated with the European Space Agency (ESA) and the Canadian Space Agency (CSA). The NASA Goddard Space Flight Center (GSFC) in Maryland managed telescope development, the Space Telescope Science Institute in Baltimore on the Homewood Campus of Johns Hopkins University operates JWST, and the prime contractor was Northrop Grumman. The telescope is named after James E. Webb, who was the administrator of NASA from 1961 to 1968 during the Mercury, Gemini, and Apollo programs.
The James Webb Space Telescope was launched on 25 December 2021 on an Ariane 5 rocket from Kourou, French Guiana, and arrived at the Sun–Earth L2 Lagrange point in January 2022. The first image from JWST was released to the public via a press conference on 11 July 2022. The telescope is the successor of the Hubble as NASA’s flagship mission in astrophysics.
JWST’s primary mirror consists of 18 hexagonal mirror segments made of gold-plated beryllium, which combined create a 6.5-meter-diameter (21 ft) mirror, compared with Hubble’s 2.4 m (7 ft 10 in). This gives JWST a light-collecting area of about 25 square meters, about six times that of Hubble. Unlike Hubble, which observes in the near ultraviolet and visible (0.1 to 0.8 μm), and near infrared (0.8–2.5 μm) spectra, JWST observes in a lower frequency range, from long-wavelength visible light (red) through mid-infrared (0.6–28.3 μm). The telescope must be kept extremely cold, below 50 K (−223 °C; −370 °F), such that the infrared light emitted by the telescope itself does not interfere with the collected light. It is deployed in a solar orbit near the Sun–Earth L2 Lagrange point, about 1.5 million kilometers (930,000 mi) from Earth, where its five-layer sunshield protects it from warming by the Sun, Earth, and Moon.
Initial designs for the telescope, then named the Next Generation Space Telescope, began in 1996. Two concept studies were commissioned in 1999, for a potential launch in 2007 and a US$1 billion budget. The program was plagued with enormous cost overruns and delays; a major redesign in 2005 led to the current approach, with construction completed in 2016 at a total cost of US$10 billion. The high-stakes nature of the launch and the telescope’s complexity were remarked upon by the media, scientists, and engineers.
US$10 billion つまり 1兆数千億円を使って宇宙望遠鏡を打ち上げて軌道に乗せ、大量のデータを日々送り続けさせる。すごいというか、なんというか。
日本はこのプロジェクトに参加せず、独自の道を歩んでいる。スイスやフランスの学者たちが JWST からのデータを自由に使って論文を書いているのを見ると、なんだか残念な気がする。
何十億年も前に遠い宇宙で発生した波が、何十億年かかって地球に届く。そこで 今 発生した波は、今から何十億年か後に地球に届く。でもその時には、地球は存在していないかもしれない。
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