The James Webb Space Telescope (JWST) was a dream come true when an Ariane 5 rocket launched from French Guiana on December 25, 2021. Those hopes belonged to astrophysicists who wanted to go back in time to when the earliest galaxies originated, to gaze through dust clouds to watch stars being born, and to examine the atmospheres of exoplanets to discover if they could host life. After orbiting the Earth for almost a year, JWST is finally making those hopes a reality.
There are many benefits to using the latest space telescope above any earlier mission. First and foremost is its massive size: JWST’s mirror is made up of 18 hexagonal segments coated in gold and is 6.5 meters in diameter. This massive telescope has a mirror that is 3.6 meters in diameter, making it able to record light from distant objects at a rate six times faster than the Hubble Space Telescope’s 2.4-meter mirror.
The infrared sensitivity of JWST, however, is what will truly change the game. From the red end of the visible spectrum to the mid-infrared, the space telescope can see light at wavelengths of 0.6 to 28.5 micrometers. Most of Hubble’s sensitivity is concentrated on visible light, but the telescope’s optics are tailored to record radiation from 0.09 micrometer (in the ultraviolet) to 2.5 micrometer (in the near-infrared). Surprisingly, JWST won’t be able to resolve finer details in the infrared domain than Hubble does in visible light. Resolution improves with larger mirrors, but decreases with increasing wavelength.
Infrared observations reveal galaxies that existed shortly after the Big Bang, fewer than a billion years after the event. Due to the expansion of the universe, the ultraviolet and visible light emitted by these objects is now primarily at infrared wavelengths. These young galaxies can only be seen from Earth if one looks into the infrared. This is also true for young stars. Dust surrounding newborn stars scatters visible light, concealing their contents from our view, but allows most infrared radiation to pass through.
Infrared light is invisible to the human eye. Therefore, JWST photos do not have accurate color representations. To simulate how the human retina processes light, scientists often assign redder colors to longer infrared wavelengths and bluer colors to shorter infrared wavelengths. On the other hand, this pattern can be manipulated to highlight certain aspects.
Although JWST was launched in the latter half of 2021, it took the space observatory 29 days to arrive to its orbital home around the L2 Lagrange point, which is located about 930,000 miles (1.5 million kilometers) from Earth, and another five months for scientists and engineers to get the telescope ready for its debut. Early-release science initiatives and proposals from the first cycle of science operations (Cycle 1) have yielded the majority of the results thus far. Here you may learn about some of the most fascinating discoveries made by the telescope thus far.
Close to home
JWST is a general purpose observatory despite its emphasis on faraway galaxies and star formation. The infrared vision of this telescope allows it to see details in solar system objects that are invisible to the naked eye. Among the earliest studies were those of cloud bands on the gas and ice giant planets, the monitoring of cloud patterns on Saturn’s largest moon Titan, the investigation of Pluto’s climate, and the investigation of many of the smaller asteroids and trans-Neptunian objects that inhabit the outer solar system.
In fact, JWST watched NASA’s Double Asteroid Redirection Test (DART) collide with asteroid moonlet Dimorphos back in September. As a result of the collision, the object’s orbit around Didymos was significantly altered, providing valuable data that will be used to evaluate the space agency’s ability to deflect potentially dangerous asteroids that may otherwise cross Earth’s path.
Consider the space telescope as a cosmic weather satellite, and you won’t be too far off base. Before the Cassini probe plummeted into Saturn in September 2017, we got our last up-close look at the ringed planet. Since Voyager 2 passed by Uranus and Neptune in the 1980s, neither planet has been visited by a spacecraft. JWST, however, can see the storm systems on these planets in stunning detail.
In July of 2016, Neptune was observed by the telescope for the first time. Because methane gas in its atmosphere absorbs near-infrared light, most of the ice giant’s visible surface appears dark. However, a few brilliant clouds of methane ice may be seen, and a faint line following the equator provides evidence of the planet’s global circulation. Neptune’s superfast, ferocious winds and raging storms are powered by this planet’s unique circulation. The images of Neptune’s rings provided by JWST are the clearest we’ve seen since Voyager 2’s 1989 flyby.
Other Worlds
Despite the efforts of planetary scientists, not much is known about the more than 5,000 exoplanets we know exist in the Milky Way. Even though Hubble and other Earth-based telescopes have allowed us to determine their orbits and, in many cases, their sizes and masses, much more information remains out of our grasp. However, JWST has already begun to alter the established order.
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| Thousands of stars pepper the central regions of the Eagle Nebula (M16) when seen in infrared light. Compare this JWST image with Hubble’s visible-light view, where the nebula’s dusty pillars block the vast majority of embedded suns. (Credit: JWST: NASA/ESA/CSA/STScI/J. DePasquale, A. Koekemoer, A. Pagan (STScI)) |
To what extent do exoplanets play a role in JWST’s research? During Cycle 1, roughly a quarter of their observing time was devoted to investigating these planets and the ingredients that go into making them.
The exoplanet JWST has confirmed orbits the red dwarf star LHS 475, which is 41 light-years from Earth and is located in the constellation Octans. The new space telescope confirmed the tiny dimming of the star’s light caused by the planet transiting in front of the star’s disk, which had been suggested by NASA’s Transiting Exoplanet Survey Satellite (TESS). The planet has a rocky appearance and a diameter only 1% smaller than Earth’s, but that’s about it in terms of similarities to our home planet. It takes only two days for the planet to complete one circle around its sun, and its surface is several hundred degrees hotter than Earth’s.
The ability to study the atmospheres of exoplanets is where JWST really shines. This can be done by using the telescope’s powerful spectrographs to observe transits. When a planet’s atmosphere comes between Earth and its host star, certain colors of light from the star are blocked off. Astronomers can learn about the composition of these worlds by analyzing their spectra, as each atom and molecule leaves a unique mark on light.
The infrared region of the spectrum is home to the vast majority of the compounds of interest to extraterrestrial scientists. Hubble’s observations might have whet scientists’ appetites, but JWST will fulfill them.
WASP-39 b, a hot gas giant planet 700 light-years away in the constellation Virgo, was the first exoplanet the observatory focused on. Superb resolution from JWST confirmed the presence of water, sulfur dioxide, carbon monoxide, sodium, potassium, and carbon dioxide for the first time in any exoplanet. The planet’s dazzling brightness is not the result of a runaway greenhouse effect, but rather its proximity to the star, which puts it on an orbit 4.52 million miles (7.27 million km) from the center of the galaxy. Mercury, by contrast, orbits the Sun at a distance of roughly 36 million miles (57.9 million km).
Peering Inside Stellar Nurseries
Nebulae are gas and dust-rich stellar nurseries where planets and their host stars are born. However lovely they may be, these clouds obscure, at least visually, the crucial processes taking place below. JWST’s infrared vision has begun to unlock these hitherto inaccessible realms.
The Eagle Nebula (M16) in the constellation Serpens was one of its initial targets after being made famous by the Hubble Space Telescope in 1995. TIME magazine included the striking “Pillars of Creation” image in its collection of the 100 most significant photographs of all time. This famous star-forming zone, about 6,500 light-years from Earth, was also seen by JWST, and the results are just as breathtaking.
Many stars were already emerging from their birth cocoons when JWST was launched, but Hubble only detected opaque dust and frigid gas. Images captured with reflecting telescopes like JWST reveal the majority of these newborn stars to be located outside the dark pillars and to be distinguished by their diffraction spikes.
These young stars have been around long enough for nuclear fusion to begin at their centers, transforming them into mature stars. However, protostars even younger than those seen by JWST were also discovered by the space telescope. These juveniles emit radiation when jets of material they occasionally expel collide with the dense matter all around them. Bright red glows can be seen at the bases of the two lower pillars, where the nicest examples can be found. The protostars are thought to be no older than a few hundred thousand years, according to astronomers.
Beyond the Milky Way
Naturally, star formation occurs in many different places in the cosmos, and JWST researchers have been eager to learn more about these places. Here in the Local Group, we have two crucial locations. Both the Large and Small Magellanic Clouds, the two largest satellite galaxies of the Milky Way, contribute significantly to our understanding of the cosmos.
That’s because the two galaxies only have approximately half as much metal as the Milky Way does. Metals are elements heavier than helium and are created in the furnaces of huge stars. When galaxies were producing stars at their peak rate, perhaps 2 or 3 billion years ago, conditions like this prevailed. The explosions that occurred at this “cosmic noon” altered the galaxies at the time, and their effects can still be seen in modern galaxies.
The Tarantula Nebula (NGC 2070) is the only structure in the Magellanic Clouds that adequately represents the current state of affairs. To learn more about the Tarantula Nebula, check out “Untangling the Tarantula Nebula” in the September 2021 edition. The Tarantula is the most prolific star-forming zone in the nearby cosmos. There are enough hydrogen and helium in the nebula to produce hundreds of thousands more stars, adding to the 820,000 already catalogued. At its heart is a dazzling star cluster known as R136, which is home to dozens of stars that are at least 100 solar masses in mass.
The Tarantula is seen in unparalleled detail in JWST’s first observations. A big bubble in the center of the nebula has been cleared out by the powerful radiation and stellar winds from the giant stars in R136. Only the densest of the surrounding areas hold out, which means they must be home to their own newborn stars. Due of its proximity to Earth (160,000 light-years; a cosmic stone’s toss), the Tarantula nebula provides astronomers with a glimpse of the circumstances they will face when they go deeper into the cosmic midday.
To The Edge
Often, scientists are able to better understand more distant objects by observing nearby ones. Like how studying star formation in the Magellanic Clouds can teach us about the development of stars elsewhere in the universe, so too can studying planets in our solar system enlighten research into exoworlds. Similarly, learning about the complex interactions between galaxies is essential to unraveling the mysteries of the universe’s infancy.
Astronomers have enjoyed putting JWST’s ability to directly study ancient galaxies formed at the start of the cosmos to the test. While local locations can often serve as analogies for older, more distant environments.
A deep-field photograph of the galaxy cluster SMACS 0723 in the southern constellation Volans was the first image released by JWST. The exposure time of 12.5 hours captures galaxies even fainter and farther away than Hubble could view, compared to the weeks required for Hubble’s multiple deep fields.
SMACS 0723 is depicted here as it appeared “only” 4.6 b.y. ago. To observe galaxies that were around a billion years after the Big Bang, we need the cluster’s enormous bulk to act as a gravitational lens and magnify and distort anything behind it. The field’s smallest galaxies are, as could be expected, the most distant ones. Interesting, they don’t resemble the more developed spiral and elliptical galaxies that are closer to Earth.
The two most distant galaxies ever spotted, however, may be the most important findings to date. Scientists discovered two other universes that existed only 450 million and 350 million years after the Big Bang (13.8 billion years ago) by using the huge galaxy cluster Abell 2744 in Sculptor as a gravitational lens. These galaxies are very luminous, suggesting that they began to form less than a billion years after the Big Bang. Scientists are unsure if the galaxies are home to a vast majority of very dim stars or a small number of extremely bright Population III stars, which are fictitious huge giants made up entirely of hydrogen and helium and thought to be the first stars in the galaxy.
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| JWST’s first deep-field photo captured the galaxy cluster SMACS 0723. The cluster members lie about 4.6 billion light-years from Earth and appear as white elliptical glows. Their mass creates a gravitational lens that magnifies and warps more remote galaxies, some of which existed less than a billion years after the Big Bang. (Credit: NASA/ESA/CSA/STScI) |
After a successful launch on an Ariane 5 rocket, NASA has determined that JWST has enough fuel to run for at least 20 years. That means the scientific exploration, new findings, and stunning imagery are just getting started.
