Last year, before the launch of the James Webb Space Telescope, I wrote: “The largest space telescope in history is about to blow our minds.”
Consider this stunned. NASA has finally revealed its first images from the space observatory. These pictures have been decades in the making and come after years of delays and budget busts. But they do not disappoint. Consider this first image released by the space agency on Monday:
What makes this painting so stunning is how small it is and how large it is at the same time.
It is small in the sense that this image represents only a small part of the night sky. Imagine holding a grain of sand within your reach. The area of the sky covered by the grain — that’s the size of the area captured in the image above.
But it is huge in the sense that almost every object in this image is a galaxy (except for the bright spiky starbursts, which are the stars in the foreground). Think about it: there are thousands and thousands of galaxies in every patch of sky, at least.
And while it seems like a flat image to us, this image reveals the depths of the universe and is a window through time. The faintest, tiniest flashes of light in these photos are images of galaxies as they existed more than 13 billion years ago, near the very beginning of time (that light has been traveling through space ever since). And not only can Webb take pictures of galaxies this old; a space telescope can make measurements of what elements those early galaxies are made of.
This image is similar to a sedimentary rock core sample. It shows the evolution of the universe over time in its many layers.
And it represents a huge improvement over the capabilities of the Hubble Space Telescope, which until Webb’s launch was the largest observatory in space. Hubble’s mirror is an impressive 7.8 feet in diameter. Webb’s beautiful gold-colored mirrors combine for a 21.3-foot diameter. Altogether, that’s more than six times the light-gathering surface area, and when it comes to telescopes, more light-gathering means more detail.
You can already see the improvements Webb brings over Hubble. The Hubble Space Telescope previously made similar observations of the same cluster of galaxies that Webb photographed above.
In the lower image slider, the Hubble view is on the left. On the right, Webb’s view is more detailed. More faint galaxies in the background are more easily distinguished. You can also more easily see how some galaxies are more clearly distorted, the result of their light passing through the gravitational lensing of the closer foreground galaxies. (Note: these images are not perfectly aligned, but you’ll still be able to see a big difference in detail.)
Webb’s other advantage over Hubble is the type of light it collects.
Light comes in many different varieties. The human eye can only see a narrow band known as visible light, but the universe contains lots and lots of light beyond this range, including higher frequency, higher energy forms: ultraviolet light and gamma rays. Then there is low-energy light with longer wavelengths: infrared, microwave, radio.
The Hubble Space Telescope collects visible light, ultraviolet and a little infrared. Webb is primarily an infrared telescope, so it sees light that is at a longer wavelength than our eyes can see. This seems geeky and technical, but it’s actually what allows the Web to look further back in time than Hubble.
Infrared light is often very old light, due to a phenomenon called redshift. As the light source moves away from the observer, it stretches, turns into longer and longer wavelengths, becomes redder. This is similar to what happens to the sound of a siren going by: the pitch increases as the siren approaches and then decreases as it moves away. Because space is constantly expanding, the most distant things in the universe move away from us, their light getting redder and redder before eventually falling into the infrared spectrum. Infrared is invisible to the human eye, but the Web can capture it in stellar detail.
On Tuesday, NASA released even more images of Webb, showing off its impressive capabilities. Check out the Carina Nebula, a star-forming region, here. Infrared light is less obscured by cosmic dust, so the Webb telescope can detect more stars in this region than Hubble could. “Webb is discovering new stellar nurseries and individual stars that are completely hidden in visible light images,” explains NASA.
Here, the Web spots a quintet of galaxies. “Webb shows never-before-seen detail in this group of galaxies,” reports NASA. “Glittering clusters of millions of young stars and starburst regions of new star birth adorn the image.”
In another stunning image, Webb observes the remains of a dying star in the Southern Ring Nebula. On the left below, the nebula is captured in near-infrared, and on the right, in mid-infrared, each revealing different details in this cataclysm. The nebulous star at the center “sends rings of gas and dust for thousands of years in all directions,” NASA writes.
This is just the beginning of Webb’s scientific mission. In the future, scientists hope to use it to see the first galaxies, which housed the first stars, and understand the period of time called the “cosmic dawn,” when the universe first became transparent to starlight.
Before the cosmic dawn, the universe was shrouded in a “dense, obscuring haze of primordial gas,” as the National Science Foundation explains. There is no light reaching our telescopes from this time, which is called the cosmic dark ages. (There is some background radiation from the Big Bang called the cosmic microwave background, a faint glow that shines on us before the dark ages. But mostly, the dark ages are a blank spot in our universe timeline.)
Astronomers hope the Web will help them understand the end of the dark ages and understand what caused this fog to lift, ushering in the cosmic dawn.
Scientists are also excited to use Webb’s infrared capabilities to study exoplanets, planets that orbit stars other than our own. Webb is unlikely to see an exoplanet directly, but what it can do is observe the stars it orbits. When a planet orbits in front of a star, the star’s light passes through the planet’s atmosphere like a filter. Scientists can study the quality of light coming from that filter and determine the composition of the planet’s atmosphere based on it. And a team of scientists working on the Web has already done that. NASA announced Tuesday that Webb had discovered water in the atmosphere of a gas giant planet orbiting a sun-like star.
Advances like the James Webb Space Telescope make me think about how we, humanity, are a part of the universe that looks back on itself. The Big Bang, the birth of stars, the formation of galaxies… we are as much a consequence of the physics and evolution of the universe as anything else that exists. So when we peer back through the cosmos with a telescope like Webb, we complete the loop. We are building a tool to make the universe, perhaps, a little more self-aware.
Webb, in its most basic function, allows us to see more of the universe and further into the past. This is just the beginning. There is much more to see.