Since its launch in 2021, the James Webb Space Telescope (JWST) has destroyed any target created by NASA for it. It is fully deployed, fully aligned and patrols the Sun-Earth L2 at 6K. Now NASA has released the first beautiful, crystal clear images from Webb. They compare what the Spitzer and Webb space telescopes see when they look at the same place in the sky. And the difference is amazing. Web’s clarity of vision makes Spitzer look like a VHS tape.
At a press conference on Monday, scientists from the Webb project broke down the main stages of the telescope’s mission so far. And all the news is good! The brilliant new telescope is in its final phase of commissioning, calibrating and testing its instruments before it starts working. Last week, Webb began testing his delicate five-layer sun shield with a series of careful pirouettes. Now is the time to bring the four scientific instruments of the telescope into collective harmony. In the first place is MIRI, Webb’s middle infrared eye.
MIRI, a joint venture between NASA and ESA, is Webb’s “coldest tool.” The telescope must be so cold, precisely because it sees in the infrared. If it was warmer than about fifty Kelvin (-369 Fahrenheit), his own infrared radiation would blind him. But there is another reason for its thermal threshold.
Webb has to keep his tools cold enough to suppress something called a “dark current.” Dark current, NASA explains, is the electric current created by the vibration of atoms in the detectors themselves. Too much ambient energy in the detector can mimic the ping of a real photon. MIRI is extremely sensitive, so it is vulnerable to false positives from dark currents.
First photos from the Web camera
These first images from the Webb show our neighboring galaxy, the Large Magellanic Cloud. Set to 8.0 microns, the images show a gentle IR glow from clouds of polycyclic aromatic hydrocarbons (PAHs). These organic molecules are sometimes called the “building blocks of life.”
Webb is designed and built to capture the faintest glow of residual heat from things like planets, stars and gas clouds. As he searches for such long wavelengths of light, he can peek directly through darkening streaks of cold dust and debris.
JWST is often mentioned in the same breath as Hubble and Spitzer, two of NASA’s four major observatories. These powerful space telescopes are designed to rise above the light pollution, interference and atmospheric blur that oppose Earth’s observatories. Web, like Spitzer, sees mostly in the infrared, where Hubble can capture the visible spectrum and some close to UV.
But the James Webb Space Telescope has absolutely blown Spitzer away when it comes to image quality. Webb focuses its giant, flawless mirror using nanometer-precision servomotors. That is why he creates images with such elegant clarity.
In a limited system of three bodies, such as the Sun, Earth, and the Space Telescope, there are five points of orbital equilibrium, which we call Lagrange points. NASA loves Lagrange points. Of all the gin johnni in all cities around the world, Webb is in L2 orbit and the reasons for it are related to orbital dynamics.
JWST is located at the point Earth-Sun L2. This means that the Earth is always directly between the telescope and the sun. Therefore, the telescope enjoys a constant midnight in the deepest part of the cold shadow of the Earth.
But there is another reason why the Web is where L2 is. L4 and L5 are shallow gravitational wells that accumulate orbital debris. In contrast, L2 clears itself; discards matter at the slightest disturbance. That’s why the Web is in orbit around L2, instead of just orbiting L2 itself. That way, you don’t have to deal with a constant torrent of debris.
But don’t let that make you think that L4 and L5 are places you should avoid. Beyond JWST, NASA uses the other points of Lagrange Earth-Sun to do all kinds of research. For example, the SOHO orbiter monitors the solar wind from L1. And scientific generosity does not stop at Earth’s orbit. All other planets in the solar system have their points L1-L5 relative to the Sun. Because the same rules of gravity apply there, it’s easy to use Lagrange points as a “gravitational slingshot” for deep space probes. NASA’s current mission Lucy has sent a probe to Trojan asteroids that live in of Jupiter L4 and L5.
Images: NASA / JPL-Caltech (Spitzer), NASA / ESA / CSA / STScI (Webb).