NASA’s high-orbit telescope will study the origin of stars and galaxies
With so many institutions failing us, it is a surprise to find a part of the federal government that more-or-less works: NASA’s space exploration program. In February, the agency’s Perseverance rover and Ingenuity helicopter returned spectacular footage from the Jezero Crater on Mars. Of the upcoming space missions, the James Webb Space Telescope has generated the most excitement.
After years of delay, it is scheduled to launch on December 18 from Kourou in French Guiana. Its 6.5-meter (21 foot) mirror will make Webb far more precise than the Hubble Space Telescope, which has a 2.4-meter mirror. The mirror is composed of 18 hexagonal segments that will fold up like origami to fit on an Ariane 5 rocket.
The $10 billion project is twenty times over budget and fifteen years behind schedule. What’s the problem? Northrop Grumman, the principal contractor, refuses to cooperate with investigators.
Webb will be too far away for a repair mission of the kind that rescued Hubble. Those working on the project understand that something of this magnitude may not be attempted again in our lifetimes. With so much riding on a single launch, every stage of development has required extreme caution and extensive testing.
Webb is the child of Daniel Goldin, NASA administrator in the 1990s. He advocated speeding up projects and using more off-the-shelf technology. This can-do approach was blamed for both the failed Pathfinder mission to Mars in 1997 and the failed Lunar Prospector mission in 1998.
The pendulum has swung back to caution and bureaucratic groupthink. The proposed size of Webb’s primary mirror was scaled back from 8 m to 6.5 m. As the number of proposed instruments increased, costs ballooned. To defray costs, NASA sought partnerships with the European and Canadian space agencies, making the project even more complex.
This is not to say that Webb is a bad deal. Hubble cost $4 billion, or $5 billion in today's dollars. Webb is seven times larger, cryogenic, and will operate much further away from Earth.
While Hubble records visible and ultraviolet light, Webb’s three cameras together span wavelengths from 0.6 to 28.8 microns. This is essentially the infrared spectrum, as well as the color red.
Ultraviolet is electromagnetic radiation with a wavelength shorter than violet while infrared has a wavelength longer than red. Both are invisible to our eyes, which see only colors with wavelengths between violet and red. The Spitzer Space Telescope, our current infrared eye in the sky, has a 0.8-m mirror.
Seen in infrared, the Earth is a bright light. To get a clear picture of the rest of the universe, Webb will be placed in orbit around the L2 Lagrange point. Lagrange points are places where the gravity of two large masses balance, in this case, the Earth and the Sun. Hubble is 570 kilometers above the Earth, the moon is 384,000 km away, and L2 is 1.5 million km away.
L2 is always in Earth’s shadow, protecting it from solar radiation. The telescope will have a 21 by 14 m sun shield, which ripped in 2018, delaying the project.
Why infrared? It allows us to investigate the earliest stars and galaxies. Other galaxies are moving away from us as the universe expands. Those that are further away are traveling faster. The Doppler effect elongates the wavelength of the light coming from these galaxies. This is called redshifting. (A galaxy moving toward us would be “blue-shifted,” although not many are.) The amount of redshift reflects how fast an object is receding. The Hubble constant gives us the relationship between a galaxy’s redshift and its distance from us.
Since it takes time for light to travel from a distant galaxy, a high redshift galaxy emitted its light long ago. Finding the oldest objects in the universe requires us to examine electromagnetic radiation with long wavelengths.
The telescope will spend most of its time doing spectrometer readings. A spectrometer divides up the spectrum of incoming light somewhat like a prism divides sunlight into a rainbow of colors. The result is used to determine the chemical composition of the star or galaxy observed.
One of the mission’s goals is to study the “end of the dark ages” 13.5 billion years ago when the first stars appeared. It will also study the assembly of the first galaxies. Webb will be able to detect individual stars in the early universe. Infrared passes through dust clouds, so Webb will get a clear picture of the star and planet formation that goes on inside these clouds. One of Webb’s first assignments is to spend 20 hours of telescope time looking for planets around the nearby star Alpha Centauri A.
With Webb straining NASA’s resources and capabilities, one wonders how realistic the far more ambitious Artemis project is—a painfully woke mission to “land the first woman and first person of color on the Moon,” according to NASA’s web page. It will be the first manned mission to the moon since Apollo missions of 1968-1972. After sending a manned mission to the lunar south pole by 2024 and setting up a base there, NASA will then be ready to send a manned mission to Mars.
Peter Kauffner lives in Sequim, Washington.
Image: The James Webb Space Telescope. Public domain.
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