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Is the $10 billion James Webb Space Telescope worth the price tag?
Performs better than expected, which is just as well – as it's going to be pelted with space rocks
Is the $10 billion price tag for the world's most expensive telescope worth it?
The first set of images captured by the James Webb Space Telescope published this week revealed the birth and death of stars and merging galaxies in stunning full color.
Direct comparisons of the same objects taken by the aging Hubble Space Telescope show just how much better the James Webb Space Telescope, or JWST, is at infrared wavelengths, with countless more dazzling stars and galaxies popping up into view.
The goal of the James Webb effort was to build an observatory that could receive light from the deepest voids of space so scientists could peer back to a time when the first galaxies began to form. But the 'scope went through multiple redesigns since work began on it in 1990s, and it suffered numerous delays with valuable time spent fixing tears in its tennis court-sized sunshield and patching up hundreds of other points of potential failure.
Work also had to be temporarily halted when space agencies ordered employees to stay at home during the onset of the coronavirus pandemic. And don't forget the JWST also repeatedly missed its initial launch date due to vibrational issues and a faulty data cable. All the while costs for the telescope continued piling up.
It finally blasted off from Earth at the end of December, arrived at its home a million miles away a month later, and detected its first photons in February. Now it's beamed back photos of, among other things, galaxies as old as 13 billion years.
And so, after a quarter of a century, or thereabouts, of work and a hefty $10 billion bill, what does the entire effort have to show?
Not only is the JWST providing humanity with the widest, deepest, and clearest view of the universe yet, it is operating at a level that has exceeded expectations. The telescope's scientific performance is better than scientists hoped, according to a 60-page report from NASA, ESA, and the Canadian Space Agency.
"The optics are better aligned, the point spread function is sharper with higher encircled energy, and the optical performance is more time-stable than requirements," scientists, who helped conduct a sixth-month review, gushed. "The fine guidance system points the observatory several times more accurately and precisely than required. The mirrors are cleaner than requirements, which translates into lower-than-expected levels of near-infrared stray light, meaning that the sky background will be darker for JWST than expected. The science instruments have generally higher total system throughput than pre-launch expectations."
These improvements mean the JWST has a wide-range of capabilities, including the potential to peer at different types of objects, from nebulae, galaxies with quasars, the hubbub of stars toward the center of the Milky Way, our own Solar System, and near-Earth asteroids. Scientists have already directed the telescope to take infrared images of Jupiter and its moon, and have collected spectra from eight space rocks so far.
Enhanced optics capabilities have in turn boosted the overall performance of its instruments, too. The JWST has four main instruments packaged in the Integrated Science Instrument Module (ISIM) that sits behind its primary gold-plated hexagonal mirror, including the Near-Infrared Camera, the Near-Infrared Spectrograph, the Mid-Infrared Instrument, and the Fine Guidance Sensor.
"A key result of science instrument commissioning is that overall, the JWST science instruments have substantially better sensitivity than was predicted pre-launch. This result is due to higher science instrument throughput, sharper point spread functions, cleaner mirrors, and lower levels of near-infrared stray light background compared to pre-launch expectations," the report said.
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The instruments have to be cooled to keep noise levels low. Sunlight is reflected off its sunshield and heat is carried away through radiators, the Mid-Infrared Instrument also has its own cryocooler that recycles helium. Scientists say that although JWST was loaded up with enough propellant to last at least 10.5 years, it could be stretched to 20 years, giving them more observation time.
The best time to gaze at the universe using the telescope, however, is sooner rather than later. The Solar System is filled with tiny, floating bits of rocky debris broken up from larger particles formed billions of years ago. These micrometeoroids can strike the telescope and damage its components. Six of these pesky flecks have hit the JWST so far, one particularly energetic event in May 2022 caused "significant uncorrectable change" in the overall structure of one of the primary mirror's segments.
Fortunately, the imaging powers of the telescope weren't impacted too much after mission control made two small adjustments to the mirror alignment. Scientists estimate that the JWST will be pelted by micrometeoroids about once a month, meaning its mirrors will degrade over time. The actual rate of deterioration, however, is unknown.
"It is not yet clear whether the May 2022 hit was a rare event (ie, an unlucky early strike by a high kinetic energy micrometeoroid that statistically might occur only once in several years), or whether the telescope may be more susceptible to damage by micrometeoroids than pre-launch modeling predicted," the boffins noted.
The JWST team said it was looking at ways to mitigate impact risks and will continue to model how the space prangs might affect its beryllium mirrors. Official science observations have begun, and astronomers will have a long while yet to keep studying the universe at depths they have never been able to before.
"Already we have stood on the shoulders of giants like the Hubble and Spitzer space telescopes, and seen farther," John Mather, a senior project scientist for the JWST at NASA's Goddard Space Flight Center, said in a statement. "We have seen distant galaxies, as they were when the universe was less than a billion years old, and we're just beginning the search. We have seen galaxies colliding and merging, revealing their chemical secrets."
"We have seen one black hole close up, in the nucleus of a nearby galaxy, and measured the material escaping from it. We've seen the debris when a star exploded, liberating the chemical elements that will build the next generations of stars and planets. We have started a search for Earth 2.0, by watching a planet transiting in front of its star, and measuring the molecules in its atmosphere.
"We know the Webb images will rewrite our textbooks, and we hope for a new discovery, something so important that our view of the universe will be overturned once again." ®