We Earthlings have observed some pretty incredible images during the past 6 weeks using the James Webb Space Telescope (JWST). JWST has gotten pictures of early galaxies, sparkling nebulas as well as distant exoplanets since its first image was exposed to the general public in July 2022.
These images are not your normal point-and-shoot camera; instead, they’re the product of a complicated blend of instruments and technologies which are so tuned to create breathtaking cosmic views.
How the James Webb Space Telescope works
The process begins when light from a distant object hits the telescope’s 21-foot wide gold plated mirror, made up of eighteen hexagonal segments. Dividing them in this manner made it simpler for NASA researchers to release JWST to space, though they had to be calibrated with incredible precision to serve as one great mirror and keep clear focus.
The calibration is attained via “wavefront sensing,” a realignment process engineers have to repeat every few months to make sure the portions do not shift by even a few tenths of a nanometer.
In the words of Lee Feinberg, optical telescope component supervisor at the NASA Goddard Space Flight Center, “each mirror is aimed to 1/10,000th the thickness of a human hair.”
Webb doesn’t see exactly the same light as us, as opposed to its famous predecessor, the Hubble Space Telescope. Being an infrared telescope, it is able to observe wavelengths more compared to visible light, which makes it perfect for watching galaxies in the distance. Simply because the universe is continuously growing, and as galaxies move away from us, their light grows redder, ultimately becoming indistinguishable to Hubble and humans. That blind spot is precisely where JWST flourishes.
The Hubble profound Fields, a group of exposures made during the past two years, have penetrated the cosmos farther than any telescope has ever seen before, revealing the incredible abundance of Deep space.
“It demonstrated that there were a lot of galaxies a long way away and that Hubble couldn’t see the most distant ones,” said Marcia Rieke, an astronomy professor at the University of Arizona. Nonetheless, Webb has made its very own deep field picture and has captured even fainter galaxies compared to its predecessor.
JWST detects a range of wavelengths
Rieke is also a member of the NASA team that created JWST. She’s, particularly, the chief investigator for the Near Infrared Camera or NIRCam, one of the four scientific devices aboard the telescope. It’s utilized in combination with another digital camera, the Mid-Infrared Instrument, or MIRI. The 2 can detect a broad range of wavelengths, enabling astronomers to look at everything from comets to protoplanetary disks in addition to new stars.
Each camera includes a set of filters, 10 for MIRI, 29 for NIRCam, which are made for certain areas of the infrared spectrum. The majority of the pictures are composites of a number of filters. Additionally they usually involve several exposures, in a procedure known as dithering, where the frame of the telescope is somewhat shifted following every exposure to stop the corrupting impact of cosmic ray hits along with other problems.
This way, Rieke states, “if there is a bad pixel, it gets filled with info out of good pixels.” Subsequently the various pictures could be aligned as well as combined into a single picture.
The telescope features any given fixed field of view, so to be able to cover a significant region, it needs to discuss just a tiny area at the same time. Over dozens of frames, Rieke will utilize 9 air filters, each for 9 exposures, for one survey of the skies. That is eighty one exposures for one frame, and more or less 7,000 for the whole composite. Once again, not your typical point-and-shoot.
Exposure Time
Additionally, astronomers must decide just how long to expose their images. A fast look at the sky displays huge variations in brightness between planets, stars, galaxies and other objects, so Webb must be versatile enough to account for them all. For example, NIRCam’s time of exposure ranges from a few thousandths of a second to approximately twenty three minutes. The space Telescope Science Institute even offers an exposure calculator which users are able to use to figure out what’ll provide the very best results.
One particular challenge is to look at dark objects near brighter objects, like an exoplanet in the neighborhood of a brilliant star. NIRCam also comes with a coronagraph, and that is basically a glass plate with a dark dot to conceal the unwanted illumination for all those scenarios.
“By getting rid of the glare out of the star itself, you can study its close surroundings better,” Rieke said. “It’s like putting your thumb up and blocking the sun,” he explained.
Another benefit of infrared imaging is usually that longer wavelengths of light shine through the fine dust that is sweeping countless galaxies, giving a deeper view of space. A few of the most breathtaking pictures taken by JWST so far however take the dust as their subject. A dreamlike image of the Carina Nebula’s cosmic cliffs shows previously indistinguishable stellar nurseries – wisps and pillars of fine particles, contracting to form new stars.
A few Webb photographs show what appears to be distorted star arcs, as with the ones in typical astrophotography. These have nothing to do with how MIRI and NIRCam work, actually. They are a result of gravitational lensing: Whenever the weight of a galaxy is strong enough, it can warp and magnify light from distant objects behind it, projecting them around its periphery to ensure that they come within view.
Because the human eye can not see infrared light, the JWST images do not display the cosmos as we would see it firsthand. The production team at NASA needed to make modifications to convert the wavelength statistics into visible colors. That said, it does not make them phony, and it is the only way we can gain access to these otherwise hidden corners of the universe.
“The representations that everyone oohs as well as aahs over tend to be what we might call bogus color images,” says Rieke. “They are fakes in that sense, but the shapes as well as things are extremely real,” she said.
