Bad astronomy | The first JWST images have appeared

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They are here! After over 25 years of design, planning, building, launching, deploying and testing, the first scientific images from JWST have been released that reveal the full promise and impressive nature of what this mighty observatory can achieve.*.

JWST is an infrared telescope, meaning it is designed to observe light with wavelengths longer than our eyes can perceive. This is important for astronomy: for example, warm objects emit infrared light, including things like dust scattered between stars, planets, brown dwarfs, etc., so we’ll see them better than ever before. Distant galaxies at the edge of the observable universe are swept away from us by the expansion of the universe, their light is redshifted into the infrared, so this means JWST will see them clearly and give us the best data we have. ever been on them.

The huge 6.5m mirror, made up of 18 hexagonal smaller gold-plated mirrors, collects a huge amount of light and provides a clear image of the cosmos, so the images come out clean and high resolution, and a battery of filters allows us to convert them into color images to delight our eyes and inform our brain.

And hey, your eyes and brain are waiting. Let’s go to!

NGC 3132, South Rim Nebula

NGC 3132 is planetary nebula, gas and dust ejected from a star that was once very similar to the Sun, but then ran out of fuel in its core and died. The central star expanded into a red giant, blowing away thick layers of material, then exposing its hot core, which then blew less dense, but hotter, faster gas into the previously ejected matter. This carved a huge expanding bubble in him.

The outer material, composed of cold molecular gas and dust, can be seen in the NIRCAM (near infrared camera) image in orange, thick and highly structured as the material expands. A hotter ionized gas called plasma, showing the filling of the cavity in blue. The MIRI (Mid-Infrared Instrument) camera shows longer wavelengths, and the biggest discovery is that the star in the center is actually two stars, binary system. The second star is covered in so much material that it cannot be seen in shorter wavelengths.

The twin motion may be what formed this nebula, their orbits around each other shaping how the gas was ejected. These JWST images will help astronomers understand the circumstances under which stars like the Sun die – they eject octillion tons of material back into the galaxy, which can then be incorporated into newly forming stars. Here we see the death of a star, but it also shows how it helps the next generation of stars to be born.

Stephen’s Quintet

300 million light-years from Earth is Stefan’s Quintet, a small cluster of interacting galaxies… well, four of them. The fifth, NGC 7320 (left), is actually a foreground galaxy randomly aligned with the more distant group.

The NIRCAM image shows the cold gas and dust in the group, including several ejected NGC 7318 a and b (center), two galaxies in the process of colliding. The gravity of two galaxies can emit streams of material called tidal tailswhich then cools and forms stars.

The MIRI image reveals something more: The center of NGC 7139 (above) is very bright, meaning we’re seeing huge light from a supermassive black hole greedily consuming gas and dust at the galaxy’s core. This material heats up and glows intensely when dropped. Images like these (and spectra) can tell astronomers a lot about this process, such as how massive a black hole is, how much material it eats, what happens to that stuff as it falls. in, and how some of it is ejected as long thin beams or jets that can fly away from the black hole at a decent fraction of the speed of light!


About 1100 light-years from Earth, there is a sun-like star, but an exoplanet orbiting it is very unlike the solar system. This is the planet WASP-96b, a hot Jupiter about the same size as our own Jupiter, but half the mass, and it orbits the star every 3.4 days at a distance of only about 7 million kilometers!

The upper atmosphere of WASP-96b is scalding, around 1000°C (1800°F). The planet passes in front of the star once per orbit as seen from Earth, an event called a transit. Here’s the fun part: Light from a star travels through the planet’s upper atmosphere on its way to Earth. The atoms and molecules in the planet’s air absorb very specific wavelengths of this light. So if we take the spectrum of this light, breaking it down into hundreds or thousands of colors, we can see those narrow dips in brightness caused by the planet’s atmospheric constituents that reveal its composition.

WASP-96b was chosen precisely because it has no clouds, allowing us to look deeper into its atmosphere. JWST did just that, and the resulting spectrum shows the presence of water vapor in the planet’s atmosphere! Dips in the spectrum are places where hot water – steam – absorbs infrared light. It tells us not only what it is, but also how much of it is there. Moreover, the dips do not quite correspond to the models of a cloudless atmosphere; are some clouds in the sky of WASP-96b, as well as haze, tiny particles suspended in the atmosphere.

We’ve seen the spectra of passing hot exoplanets before, but none of them compare to this level of detail in the infrared. Further spectra of other planets will reveal more information, such as the presence or absence of things like silicates (rocky material), methane, and more. This process should also work with smaller planets, although this is more difficult. Future observations could reveal what happens in the atmospheres of planets more similar to the one we live on, but orbiting stars trillions or quadrillions of kilometers away.

Carina Nebula

In the southern constellation of Carina is a ridiculously huge sprawling cloud of gas and dust called the Carina Nebula. It is approximately 7,000 light-years from Earth and one of the Milky Way’s most active star-forming factories.

In this JWST NIRCAM image, you can see a handful of very massive bright stars at the top. They emit radiation and winds of subatomic particles that corrode gas and dust, vaporizing them. This leaves behind a wall of material – this bright jagged horizontal line – with dense material at the bottom and less dense, hotter material at the top. It looks almost like a mountain range or, accordingly, a bank of clouds.

In the MIRI image, we can see the consequences of this: dozens of stars are being born there, some are ejecting their parent gas, others are still deeply enveloped in the material that formed them.

We understand a lot about star birth, but the devil is in the details. High-resolution images like these will help us see the bulk process better, and the infrared spectra of individual stars will give a wealth of information about how stars first turn on, what happens to the matter around them when they do, and how some of that stuff is. will form planets.

SMAX 0723

The first JWST Deep Field image shows SMACSJ0723.3-7327: a cluster of galaxies, a collection of hundreds of galaxies orbiting a common center of gravity. It is located approximately 4.5 billion light years from Earth.

Mind you, this image is a little confusing. All sharp objects with diffraction bursts are stars in our own Milky Way galaxy, probably hundreds or thousands of light-years away. But every fuzzy thing you see? These are entire galaxies., probably billions of light-years away. And there are thousands of them in this image.


Here’s the fun part: only a few of them are part of the SMACSJ0723.3-7327 cluster! Whitish, roughly round blobs are part of the cluster. But you can also see dozens of elongated galaxies, curved into arcs or smeared into slug-like structures. These are much more distant galaxies, far beyond the cluster as seen from Earth.

The combined mass of galaxies in a cluster distorts the light coming from objects behind it, making them larger and brighter in a process called gravitational lensing. This can pull them out like toffees, making them look like arcs. But individual galaxies in the cluster bend and distort shapes even more, which is why some of them are even more strangely shaped.

The beauty of this is that these more distant galaxies can be too faint to see without the lens effect, so many of these galaxies are much further away than we would normally be able to see. And on top of that, unconnected background galaxies scattered like diamonds on velvet, each containing billions of stars.

I will add that while this is similar to many similar Hubble images, the big difference is that it is an infrared image; what you see in blue is actually about 1 micron wavelength, near infrared green is 2-2.8 microns, orange is 3.56 microns, and red is 4.44 microns; this longest wavelength is about 7 times longer than what our eyes can see. In addition, the total Hubble Deep Field exposure time was many days. JWST’s large mirror made this image possible in just 12 hours.

While the arcs, strokes, and the like are beautiful and eye-catching, the galaxies that interest me the most are the tiny red dots. These are the most distant ones we saw when the universe was a baby. Their spectra would be critical to understanding what the Universe was doing at the time and would be one of the JWST’s biggest contributions to astronomy.

How far are those red drops? JWST has taken the spectra of some of them, splitting their light into individual infrared colors, and we can study the features of this spectrum to find out the distance to this galaxy, what elements it contains, and many other characteristics.

This spectrum shows that the light has left it. 13.1 billion years agowhen the universe was only 700 million years old. Despite this youth, we also see the presence of neon and oxygen: they are created in stars and then ejected into the galaxy when they die, so even at this young age the galaxy has gone through at least one generation of stars born and dying. .

I could write a thousand words on this stunning image: galaxies relatively close and far away; the curvature of spacetime itself, revealing the mass and structure of SMACS 0723; images of stars forming against a distorted background of galaxies; other “field” galaxies turned red from dust and distance; and even the beauty of the diffraction images of stars in our own galaxy scattered across the foreground.

But instead, I’ll leave you with a simple thought, so simple yet so profound that it’s both easy and very difficult to understand:

The size of this image is 2.4 arc minutes. This is an angular measure, and for comparison, the full moon in the sky has a diameter of 30 arc minutes, which is almost 15 times wider than this entire image.

How big is 2.4 arc minutes then? This is the same angle formed by a half-millimeter-wide grain of sand at your fingertip that you hold at arm’s length. Hold this speck of dust on the pad of your index finger and extend your hand in front of you. This tiny grain of sand would block all those thousands and thousands of galaxies.

Now think about how big the sky is compared to this grain of sand. All this heaven can hold something like 25 million such images in it. This image is a tiny part of the universe, but it shows a thousand wonders and delights.

What will we see when JWST looks at one point in the sky for as long as tens of thousands of distant galaxies open up? How many more hundreds of billions are waiting for our investigation?

Once you understand this, you will understand why astronomers do what they do.

This is a huge universe, and we want to understand it all. With JWST, we have taken a big step forward in this.

*Note. Due to controversy over the name of this observatory, I will simply refer to it as JWST. I really hope NASA rethinks the name, but until that happens, initialism will suffice.

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