![]() While Hubble, the largest optical space telescope, measures 2.4 meters across, the widest optical scope on the ground-the Gran Telescopio Canarias on the Canary Island of La Palma-spans 10.4 meters. Telescopes on the ground can grow as big as humans dare to build them. “The benefit of ground-based is you can try out new things.” “On the ground, you can make things really big, for cheaper and faster, and you can constantly upgrade,” George says. It’s phenomenally expensive to put a telescope in orbit, and most are impossible to repair or update once they’ve escaped the atmosphere. “The electromagnetic spectrum is so diverse … we need many different types of telescopes in order to really fully understand the whole universe,” says Regina Caputo, an astrophysicist at NASA’s Goddard Space Flight Center. Each of these wavelength ranges probe vastly different physical phenomena. Visible light and radio waves get through fine, but gamma rays, X-rays, most ultraviolet light and some infrared wavelengths don’t make it. “Earth is incredibly noisy, it turns out,” George says.Įarth’s atmosphere also blocks many types of light from reaching the ground. With minimal temperature swings and no mechanical stress from gravity, the precision of a telescope in space outperforms anything on the ground. Space offers an incredibly stable environment. ![]() Telescopes on Earth must peer through shifting parcels of air that blur images and make stars twinkle. “In space, there's no atmosphere, that's really the benefit,” George says. The choice of whether to erect a telescope on land or lob one into orbit is the result of balancing several factors. This holds true whether a telescope sits on the ground or lives in space, whether it focuses on visible light or expands beyond our human senses to collect radio waves or X-rays. And for a given wavelength of light, a wide mirror or lens creates a sharper image, letting researchers see those faint things in better detail. In the same way that a large bucket collects more rain than a small pail, a telescope with a larger mirror or lens ensnares more photons, allowing astronomers to see fainter things. ![]() A telescope’s job is straightforward: collect more photons than our eyes alone can see. Light, in its many guises, is often the only intel we have from far-off locales. Photons, tiny packets of light, are the main currency in astronomy. “I would describe it as a photon bucket,” says Elizabeth George, a telescope detector engineer at the European Southern Observatory. But over the four centuries that have elapsed since Galileo pointed a handheld spyglass skyward, the telescope’s job has remained the same. Each have their place in the exploration of the cosmos. But from its stable perch beyond Earth’s atmosphere, JWST’s infrared eyes will glimpse light from the first stars, peek into the atmospheres of worlds beyond the solar system and lift the veil on dust-enshrouded stellar nurseries. It won’t be as big as the ELT its 6.5-meter-wide mirror is middling compared to ground-based telescopes. Meanwhile, NASA is preparing to launch what it dubs Hubble’s successor: the James Webb Space Telescope. With a nearly 40-meter-wide mirror-roughly four times as wide as the current record holder-it will search for Earth-like planets, seek out the first generation of galaxies and produce images up to 16 times sharper than the Hubble Space Telescope (depending on the wavelength). When completed in the late 2020s, the aptly named Extremely Large Telescope will be the largest optical telescope on the planet. The most complex, nail–biting sequence was unfolding a giant sun shield designed to block radiation from the sun, moon and Earth that would overwhelm the telescope's super sensitive instruments.On a mountaintop in the Atacama Desert of Chile, a gargantuan new eye on the cosmos is taking shape. In fact, the launch was so precise, the telescope will have extra manoeuvring fuel leftover to operate beyond its expected 10–year lifetime. Since it was launched on Christmas Day 2021, that sequence of events has so far proceeded as planned. Once in space, the unfolding sequence involved 50 major deployments with 344 of what the scientists call "single-point failure" items involving latches, hinges, motors, bearings, gears, cables and pulleys. This giant, super-sensitive instrument had to be made as lightweight as possible, yet strong enough to withstand the vibrations and G-forces of a rocket launch. There is no room for mistakes and no possibility of repair by astronauts if something goes wrong. This picture from a NASA TV broadcast shows the James Webb Space Telescope shortly after separating from the Ariane 5 rocket after launching from French Guiana, on December 25, 2021.
0 Comments
Leave a Reply. |