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Our PickThe daring Webb quest

The daring Webb quest

Published: 8th Jan 2022 11:44 pm

By Marcia Rieke

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The world’s largest and most powerful space telescope rocketed away on December 25 on a high-stakes quest to behold light from the first stars and galaxies and scour the universe for hints of life. NASA’s James Webb Space Telescope (JWST) soared from French Guiana on South America’s northeastern coast, riding a European Ariane rocket into the Christmas morning sky. “What an amazing Christmas present,” said Thomas Zurbuchen, NASA’s science mission chief.

The observatory hurtled toward its destination one million miles (1.6 million km) away, or more than four times beyond the moon. It will take a month to get there and another five months before its infrared eyes are ready to start scanning the cosmos.

NASA Administrator Bill Nelson called Webb a time machine that will provide “a better understanding of our universe and our place in it: who we are, what we are, the search that’s eternal.” “We are going to discover incredible things that we never imagined,” Nelson said following liftoff. But he cautioned: “There are still innumerable things that have to work and they have to work perfectly … we know that in great reward, there is great risk.”

The Showpiece

The most daunting part of the mission — unfolding Webb’s mirror and sunshield and locking them into perfect position — was reached when the team fully deployed the spacecraft’s 70-foot sunshield. The sunshield — about the size of a tennis court at full size — was folded to fit inside the payload area of an Arianespace Ariane 5 rocket’s nose cone prior to launch. The Webb team began remotely deploying the sunshield three days after launch.

The showpiece: a gold-plated mirror more than 21 feet across. The wispy, five-layered sunshield, is vital for keeping the light-gathering mirror and heat-sensing infrared detectors at subzero temperatures.

This space science observatory has another 5 1/2 months of setup still to come, including deployment of the secondary mirror and primary mirror wings, alignment of the telescope optics, and calibration of the science instruments. After that, Webb will deliver its first images. NASA partnered with the European and Canadian space agencies to build and launch the new 7-tonne telescope, with thousands of people from 29 countries working on it since the 1990s.

Cosmic History

“Knowing when the first stars were formed, soon after the Big Bang, and understanding how they produced the building blocks of the first galaxies is an important scientific question and one of the primary science goals of JWST. We know that the elements that are needed for life and modern technology, such as carbon, silicone and gold, were ultimately created in early stars – but we don’t currently have a good understanding of how this happened.

The ultimate goal is to find a planet similar to the Earth, but it would require a very lucky combination of circumstances, because they are likely to be rare in the solar neighbourhood and very faint compared to the parent star. Most likely, JWST will study “gas giants” like Jupiter and Saturn or “ice giants” similar to Uranus and Neptune,” writes Martin Barstow, Professor of Astrophysics and Space Science, University of Leicester, in The Conversation.

The JWST will seek out the faint, twinkling light from the first stars and galaxies, providing a glimpse into cosmic creation. Its infrared eyes will also stare down black holes and hunt for alien worlds, scouring the atmospheres of planets for water and other possible hints of life. In short, Webb will reveal new and unexpected discoveries and help humanity understand the origins of the universe and our place in it.

Being Perfect

It will orbit the Earth at a distance of 1.5 million km at a point where the gravitational interaction between the Earth and the Sun is balanced (called the L2 Lagrange point ).

Nelson said he’s more nervous now than when he launched on space shuttle Columbia in 1986. “There are over 300 things, any one of which goes wrong, it is not a good day,” he told the AP. “So the whole thing has got to work perfectly.” In all, hundreds of release mechanisms need to work — perfectly — in order for the telescope to succeed. Such a complex series of actions is unprecedented — “like nothing we’ve done before,” noted NASA programme director Greg Robinson.

“Now it’s our job to start from here and keep going,” said Massimo Stiavelli, an astronomer who heads the Webb mission office at the Space Telescope Science Institute in Baltimore. The institute serves as the control hub for Hubble and, now, Webb.

NASA is shooting for 10 years of operational life from Webb. Engineers deliberately left the fuel tank accessible for a top-off by visiting spacecraft, if and when such technology becomes available.

Named after the man who led NASA during the space-trailblazing 1960s, the James Webb Space Telescope is 100 times more powerful than Hubble. Spacewalking repairs by astronauts transformed Hubble into a beloved marvel that has revolutionised humanity’s understanding of the universe, casting its eyes as far back as 13.4 billion years. It’s now up to Webb to draw even closer to the Big Bang 13.8 billion years ago.

“Hubble is like the perfect story. It starts badly, then the cavalry fixes it, then it’s a major success. It’s almost a Christmas movie in a way,” Stiavelli said following Webb’s liftoff. “It’s a high bar, but hopefully the science contributions of Webb will be up there.”

NASA has never attempted such a complicated series of steps remotely. Many of the mechanisms have no backup, so the failure of any of 344 such parts could doom the mission. (AP)

Young galaxies, alien atmospheres

The Webb telescope has a mirror over 20 feet across, a tennis-court sized sun shade to block solar radiation and four separate camera and sensor systems to collect the data.

It works kind of like a satellite dish. Light from a star or galaxy will enter the mouth of the telescope and bounce off the primary mirror toward the four sensors: NIRCam, which takes images in the near infrared; the Near Infrared Spectrograph, which can split the light from a selection of sources into their constituent colours and measures the strength of each; the Mid-Infrared Instrument, which takes images and measures wavelengths in the middle infrared; and the Near Infrared Imaging Slitless Spectrograph, which splits and measures the light of anything scientists point the satellite at.

This design will allow scientists to study how stars form in the Milky Way and the atmospheres of planets outside the Solar System. It may even be possible to figure out the composition of these atmospheres. Ever since Edwin Hubble proved that distant galaxies are just like the Milky Way, astronomers have asked: How old are the oldest galaxies? How did they first form? And how have they changed over time? The Webb telescope was originally dubbed the “First Light Machine” because it is designed to answer these very questions.

One of the main goals of the telescope is to study distant galaxies close to the edge of observable universe. It takes billions of years for the light from these galaxies to cross the universe and reach Earth. Finding the first aggregations of stars that formed after the Big Bang is a daunting task for a simple reason: These protogalaxies are very far away and so appear to be very faint. Webb’s mirror is made of 18 separate segments and can collect more than six times as much light as the Hubble Space Telescope mirror. Distant objects also appear to be very small, so the telescope must be able to focus the light as tightly as possible.

The telescope also has to cope with another complication: Since the universe is expanding, the galaxies that scientists will study with the Webb telescope are moving away from Earth, and the Doppler effect comes into play. Just like the pitch of an ambulance’s siren shifts down and becomes deeper when it passes and starts moving away from you, the wavelength of light from distant galaxies shifts down from visible light to infrared light.

(The author, Regents Professor of Astronomy, University of Arizona, is an astronomer and the principal investigator for the Near Infrared Camera – or NIRCam for short – aboard the Webb telescope.

Hubble Vs Webb  

“Comparing Hubble and Webb is like asking if you will love your second child as much as your first,” says Susan Mullally, Webb’s deputy project scientist at the Space Telescope Science Institute in Baltimore. “Hubble will always be loved for its awe-inspiring images of our universe and will continue to collect important data for astronomers. Webb gives us new and unique eyes of places that we have never been able to reach.” Nevertheless, here’s the lowdown on Hubble versus Webb:

Rocket Rides

Hubble caught a lift to orbit tucked inside NASA’s space shuttle Discovery in 1990. It quickly ran into trouble: one of the telescope’s solar wings jammed as it was unfurling but commands from Earth freed the panel. Within weeks, Hubble’s blurry vision was detected. Spacewalking astronauts fixed it three years later. Soaring from South America on a European Ariane rocket, Webb won’t be reachable by astronauts as its destination is 1 million miles away.

Let There be Light

Webb is expected to behold light from the universe’s first stars and galaxies, beyond Hubble’s range. This light will reveal how the original stars looked 13.7 billion years ago. Hubble has stared as far back as 13.4 billion years, disclosing a clumpy runt of a galaxy that is currently the oldest and farthest object ever observed. Astronomers are eager to close the 300-million-year gap with Webb and draw ever closer in time to the Big Bang, the moment the universe formed 13.8 billion years ago.

Infrared Vision

Hubble sees what we see — visible light — with a little ultraviolet and infrared thrown in. Webb has infrared vision, allowing it to pierce cosmic clouds of dust. The shorter visible and ultraviolet wavelengths emitted by the first stars and galaxies have been stretched as the universe expands, so Webb will see them in their elongated, heat-emitting infrared form.

Size Matters

To discern the universe’s first, faint stars, Webb requires the largest mirror ever launched for astronomy. The mirror spans more than 21 feet, yet is lighter than Hubble’s, which is 8 feet across. That’s because Webb’s mirror is made of beryllium, a strong but lightweight metal.

Location, Location

Hubble circles 530 km overhead. The altitude was dictated by the capabilities of NASA’s space shuttles, which delivered Hubble to orbit.  Webb is bound for  a more distant spot — 1 million miles. This is where the gravitational forces of the Earth and sun balance, requiring minimal fuel for a spacecraft to stay put. Webb will constantly face the nightside of Earth as the spacecraft and planet swoop around the sun in unison.

Pricey Affair

Hubble was years late and millions over budget when it rocketed into orbit in 1990. Webb too is years late with huge cost overruns. NASA’s tab for Hubble from its 1970s development until now: $16 billion, adjusted for inflation. That doesn’t include all the shuttle flights for launch and repairs. Webb’s price tag is an estimated $10 billion; that includes the first five years of operation.

Hubble and Webb Namesakes

Astronomer Edwin Hubble confirmed a century ago that countless galaxies exist beyond our Milky Way and the universe is constantly expanding. James Webb led NASA from 1961 to 1968, presiding over Projects Mercury and Gemini, and the early phase of Apollo’s moon-landing programme. In 2002, a decade after Webb’s death, NASA chose his name for the new telescope.

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