What the James Webb Telescope images mean for space


Jhe NASA scientists behind the James Webb Space Telescope have spent the better part of the past 26 years arguing for three things: patience, time and, to a large extent, money. It was in 1996 that a committee of astronomers working with the space agency first proposed a next-generation space telescope that would be able to peer 13.6 billion light-years away – detecting infrared light which reaches us only 200 million years after the Big Bang. The telescope, they promised, would be ready for launch by 2007 and would only cost $500 million, which is cheap.

It didn’t work that way. That slated 2007 launch didn’t happen until Christmas Day 2021, and as for that $500 million cost? It jumped to $10 billion. But the astronomers’ promise remained the same: the images revealed by the new telescope would be spectacular.

This morning, that promise is kept. During a press conference at the Goddard Space Flight Center in Greenbelt, Maryland, NASA will unveil four new images captured by Webb that, by any measure, will be dazzling: nebulae and galactic clusters, and a giant never seen before. -saw exoplanet. This adds to a stunning image of a galactic cluster known as SMACS 0723 – a swarm of thousands of galaxies, including the most distant ever observed in the infrared spectrum – revealed yesterday at a press conference in the White House by NASA Administrator Bill Nelson, with President Joe Biden and Vice President Kamala Harris in attendance.

“These images will remind the world that America is capable of great things,” Biden said. “There is nothing beyond our possibilities.” The Webb Telescope, he added, “symbolizes the relentless spirit of American ingenuity.”

The image unveiled yesterday and the four other images NASA will reveal today are objects that most people outside the astronomy community have never heard of before, but which will now achieve a new place in history. cosmic. These are, in addition to SMACS 0723:

  • The Carina Nebula, one of the largest and brightest nebulae in the sky, is located 7,600 light-years from Earth.
  • WASP-96b, a gas giant planet orbiting a star 1,150 light-years from Earth.
  • The Southern Ring Nebula, an expanding cloud of gas nearly half a light-year wide surrounding a dying star 2,000 light-years away.
  • Stephan’s Quintet, a group of compact galaxies, located 290 million light-years from Earth, was first roughly photographed in 1787.

It’s in some ways the smallest object photographed by the telescope – exoplanet WASP-96b – that will likely cause the most excitement. Until now, exoplanets, or planets circling other stars, were only detectable in one of two ways: the transit method, in which astronomers discern the faint attenuation of light in a parent star when a planet in orbit passes in front of it; and the radial velocity method – in which they look for the small wobble in the star’s position as the orbiting planet’s gravity pulls it.

What astronomers have never been able to do until now is see the planet itself, because spotting such a small body in the blinding glare of its parent star would be like standing a block away and trying to see a moth hovering next to a lamppost. The smaller body image would just be washed out. So the WASP-96b image alone is historic – and it sets Webb up for perhaps even more sensational discoveries: Now that astronomers can accurately image exoplanets, they can also search them for signs of life. , as light from their home planet passes through their atmosphere, revealing the composition of gases and the possibility of chemical fingerprints from biology.

As Vice President Harris said yesterday, with these photos we are entering a “new phase of scientific discovery”. These images offer a “new window into the history of our universe,” President Biden added.

That Webb works is a triumph in itself, since its engineering and location in space make it unlike any other telescope ever built before. The venerable Hubble Space Telescope, launched in 1990, circles the Earth in a 547 km (340 mi) high orbit, just above our atmosphere, and looks, well, like a telescope – a cylinder made of metal with its integrated optics and a stream of light from one end. Its conventional look is because Hubble operates in a conventional way, seeing primarily in the visible spectrum. This means that his mirrors must be shielded from stray light from the sun, earth and other objects he doesn’t observe – thus storing them inside the telescopic body – allowing them to focus on those that he doesn’t observe. ‘It is.

Instead, the Webb telescope operates in the infrared spectrum, a wavelength of light beyond the visible spectrum that is a measure more of heat than light. Hubble could never see the 13.6 billion light-years away that Webb can, because visible light from so far away is obscured by dust and gas in deep space. Infrared light passes through this interference. To work, Webb must therefore be shielded from stray heat, which would blur its infrared optics just as stray light would blur Hubble’s visible-spectrum mirrors. For this reason, the telescope must be kept ultra cool. This gives an unusual architecture.

The Webb’s main mirror measures 6.5 m (21.6 ft) in diameter and is made up of 18 hexagonal segments, each of which can be adjusted on seven different axes with precision down to a nanometer – or one billionth of a meter – allowing the Focusing mirror assembly for maximum detail and clarity. The mirror remains exposed to space, because placing it in a case like Hubble’s main mirror would retain heat. Nor does it orbit Earth, where the constant day-night cycle of each orbit would cause its own disruptive temperature changes. Instead, it is positioned 1.6 million kilometers (one million miles) from the planet, where it remains stationed in what is called a Lagrange point, a place in space where the gravity of the Earth and the sun cancel each other out, allowing objects around the invisible point as if they were orbiting a solid body like a planet.

Still, there’s the heat of the sun and even the distant Earth and moon to deal with, and because of this, the mirror flies atop a protective sunshade, perched on the shield like a sail on a boat. Roughly shaped like a kite and as tall as a tennis court, the visor is made of five layers of kapton, a sheet-like film no thicker than a human hair. On the outer layer – the side that always faces the sun, keeping the mirror in permanent shade – the temperature is around 110º C (230º F). On the inner layer, closest to the mirror, it is -237º C (-394º F). Excessively cold temperatures like this allow the invisible and extremely faint heat of infrared signals from deep space to register on the telescope mirror and be digitally translated into visible images.

Webb is as much a time machine as an observing machine. The further a telescope can peer into space, the further back in time it travels, because images of distant objects, even traveling at the speed of light, take a very long time to reach us. The picture we see of a galaxy 13.6 billion light-years away is therefore not a picture of how it looked now, but how it looked 13.6 billion years ago, during the childhood of the universe. The Hubble Space Telescope can see a maximum of 13.4 billion light-years away, and while the mere 200 million light-year advantage offered by Webb might not seem like a lot, it’s actually huge. A lot has happened in those particular 200 million years and telescopes have been blind until now.

“The difference between what Hubble and Webb [see] It’s not like comparing someone who’s 70 to someone who’s 71,” Scott Friedman, a Webb team astronomer, said in a conversation with TIME last year. “It’s like comparing a one-day-old baby to a one-year-old baby, and that’s a huge difference.”

But the science that Webb will conduct in the coming years is for later – and already astronomers around the world are calling for proposals to set aside time on the Webb to study objects of interest in the coming years. Today, quite simply, is for dazzling. The universe can stun with its expanse and beauty. Webb, more than any other observatory before him, pulls back the curtain on all of this.

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Write to Jeffrey Kluger at jeffrey.kluger@time.com.


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