Three cheers for the James Webb Space Telescope

Two days ago, on July 12th, NASA released the first science images taken by the James Webb Space Telescope (JWST). Finally, after over a decade of design, construction, tests, and even a last-minute launch delay, we are able to look at the universe with a new pair of eyes. And what special eyes they are.

A lot of people have criticized NASA for the delays in the construction of the JWST. However, these were all necessary to ensure that everything worked properly. During its deployment, there were over 300 possible single-point failures, any one of which could have doomed the telescope. This complex deployment process was necessary because of the sheer size of the JWST, with a primary mirror 21 feet (6.5 m) in diameter, and a sunshield the size of a tennis court. If you want to learn more about JWST’s launch and deployment, you can actually watch the livestream I did about it.

For its observations, it uses four primary instruments. Its main cameras are the Near InfraRed Camera (NIRCam) and the Mid-InfraRed Instrument (MIRI). It also has two spectrometers, a Near InfraRed Spectrograph (NIRSpec) and Near Infrared Imager and Slitless Spectrograph (NIRISS). Some of the first test images released were taken by the JWST’s Fine Guidance Sensor (FGS), used for steering the telescope.

Webb’s first image is of the SMACS 0723 galaxy cluster. In this image we can observe hundreds of galaxies. Many of these are so far away that their light has been greatly redshifted by cosmic expansion. One of the JWST’s goals is to study these early galaxies.

The second data release is this spectrum of the atmospheric composition of the exoplanet WASP-96 b. As an exoplanet passes in front of its parent star, the star’s spectrum will subtly shift. The change can be used to determine what the spectrum of the planet’s atmosphere is, as it filters the light. This, in turn, allows us to work out what the composition of the planet’s atmosphere is. Preliminary analysis of this spectrum has already indicated the presence of water vapor. (By the way, this planet is a hot gas giant, which is also extremely close to its star, so life is extremely unlikely).

This image shows the Southern Ring Nebula, a planetary nebula in the constellation Vela. The result of the death of a sunlike star, this nebula is a huge bubble of expanding gas, pushed outwards by the star in its dying years. The left side of this image is an image taken by the NIRCam (near-infrared), while the right is one taken by MIRI (mid-infrared). These different bands of light help show us different things. Near-infrared is close to visible, so objects like stars (which give off visible light) are very apparent in the image on the left. Mid-infrared, on the other hand, is more suitable for picking up warm things, like dust. As a result, the stars are much less pronounced, but we can see the white dwarf at the center of the nebula more clearly. The bright star in the image on the left is actually a foreground star. The white dwarf is visible, but it is partially hidden by the diffraction spike. It’s much easier to see in the MIRI image, as the red dot to the left of the foreground star.

Pictures taken by NIRCam and MIRI can be combined into single, multi-wavelength images, like this one of Stephan’s Quintet. Here we can see four interacting galaxies, plus a fifth foreground galaxy (the large one on the left). As these galaxies move through each other and combine, the gas and dust which fills them piles up, creating large shockwaves which can lead to massive amounts of star formation. This group is actually quite large on the sky. It is as big as one-fifth of the moon’s diameter. As a result, almost 1,000 pictures had to be combined to make this 150 million pixel image.  Besides being fun to look at, this group is also famous for starring in the 1946 Christmas movie It’s a Wonderful Life.

And finally, we come to the Carina Nebula. Or, more specifically, a small region within the nebula called the “Cosmic Cliffs”. This is a region of active star birth, where massive, young stars (above the top) push away the surrounding gas and dust. High-resolution images like this are only possible because of the incredible capabilities of the JWST.

With these images, I think it’s safe to say that the JWST is living up to its designers expectations. Some people have complained that the project has been over budget. But if you look at the percentages, the JWST cost less than a penny per $100 of tax money spent by the US Government. And these five images are just the start of its scientific mission. Over the coming decade, the insights the JWST will provide us may forever change our understanding of our universe. The Hubble Space Telescope provided us with incredible views of the cosmos, making discoveries we never could have dreamed of. Hubble cost about $5 billion more than JWST, but researchers are still making new discoveries with data taken by Hubble, even archival images taken decades ago.

At this juncture, it’s important to note that the JWST is not the successor to Hubble. The HST used primarily visible light, with some near-infrared (NIR) and near-UV (NUV) capabilities. The JWST, on the other hand, is devoted solely to the infrared part of the spectrum. The real successor to Hubble is the Nancy Grace Roman Space Telescope (formerly known as the Wide-Field Infrared Survey Telescope, or WFIRST). Like Hubble, the Roman will carry both Visible and NIR cameras. However, Roman’s field of view will be 100 times larger than that of Hubble’s.

In summary, these fantastic images represent just the tip of the iceberg of what the James Webb Space Telescope will show us. I, for one, will be waiting with bated breath for the discoveries we will make with it.

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