The coolest cameras in the solar system are about to launch into space


It’s the largest, best, and most expensive space observatory ever built, but when the James Webb (Webb) Space Telescope soars into the sky later this week, it will carry an array of cameras into deep space. which is by far the coolest in the solar system.

In the works for 25 years, Webb was originally scheduled to launch in 2007 and cost $ 500 million. It ultimately cost $ 10 billion. However, if he successfully reaches space and begins operations as planned in 2022, Webb has the potential to change astronomy as we know it.

It is scheduled to launch on Christmas Eve from the European spaceport in French Guiana on top of an Ariane-5 rocket at 7.20 am EST / 12:20 GMT / 10:20 pm AEST on Friday, December 24, 2021. It will be screened. live on NASA TV on YouTube.

Artist’s impression of the James Webb Space Telescope, folded into the Ariane 5 rocket during launch from the European spaceport in French Guiana. (Image credit: ESA / D. Ducros)

The next Hubble?

Some people call Webb “the next Hubble”, but that’s not correct. While the original Space Telescope – which was launched in 1990 – continues to return incredible images from its visible light cameras, Webb will have six times the light-gathering power of Hubble, but more importantly it will add a whole new dimension to Hubble astronomy. observations by observing almost exclusively in the infrared.

Webb’s cameras will collect infrared light from far corners of the cosmos and capture what the 13.77 billion-year-old Universe looked like just after the Big Bang. To do this, its giant mirror will have to be pointed at faint galaxies for hundreds of hours in order to collect enough light.

Hubble has gone back in time as far as it can. Using its 2.4-meter mirror and a combination of visible-light and near-infrared cameras, the Hubble Space Telescope was able to take a multitude of incredible images of the early universe. His greatest achievements are arguably the Hubble Deep Fields, composite photographs that include small, redshift galaxies that existed when the Universe was only 800 million years old.

Webb will go much further in time using his mirror and 6.5-meter camera to image red galaxies some 250 million years after the Big Bang. It is hoped that scientists can use the data to probe the structures and origins of the early Universe and understand how the complex galaxies they now see actually evolved.

Webb and exoplanets

Although Webb is getting closer to the Big Bang, another more recent task for his astronomers will be to use his cameras to study exoplanets, defined as a planet that orbits a star outside the solar system. While not building on the 4,000+ exoplanets already discovered, Webb will be able to study the atmospheres of those believed to be Earth-like. As they pass through a star and are briefly backlit, Webb will study the light in their atmospheres for traces of methane, water, and carbon dioxide. To do this, its NIRCam and MIRI cameras have starlight blocking coronographs to block light from the bright host star of an exoplanet.

The mid-infrared (or MIRI) instrument of the James Webb Space Telescope. (Image credit: NASA / Chris Gunn)

Webb’s cameras

This is no ordinary camera array. Webb is uniquely designed to detect infrared light – a form of thermal radiation – emitted by distant stars, planets, and the clouds of gas and dust in which they are born. He will see the light of the first stars, considered to be about 300 times more massive than the Sun, as well as of the first galaxies. Infrared skill is important because there are parts of the Universe that are filled with dust and gas, where visible light cannot pass. Hubble has not been able to study these regions; Webb will show us the Universe so far invisible by any other telescope.

Thus, the four cameras of the Webb – housed in its integrated scientific instrument module (ISIM) behind the mirror – were designed to emerge as far as possible from the hidden cosmos:

While NIRCam and NIRSpec do a lot of the cutting edge science, it’s the MIRI camera that will likely give us some amazing wide-field astrophotography images, better than Hubble’s.

The James Webb Space Telescope has a 6.5 primary mirror that looks like a sunflower. (Image credit: NASA / Chris Gunn)

How and why Webb will keep his cameras cold

While Hubble orbit the Earth, Webb will fly a million miles away. Infrared light is basically thermal radiation, which is also emitted by us and our electronics. Webb’s cameras must therefore observe the Universe far from Earth where it is very, very cold. About four times the distance from Earth to the Moon, Webb will operate at Lagrange Point 2, where the gravity of the Earth and the Sun combine to create a stable location.

To make it as cold as possible, Webb will operate at a shivering temperature of -233 ºC / -388 ºF, or approximately 40 Kelvin. However, the detectors inside the MIRI instrument will operate at an even lower temperature of -266 ºC / -448 ºF, or 7 Kelvin. This is essential because it cannot glow brighter than the weak heat signals it is there to detect. If so, his images will be marred by what astronomers call noise. A five-layered kapton sun shade will act as an umbrella and separate Webb into a sunny side and a cool side. The void between the layers will behave like an insulator.

Webb’s perilous journey to L2 will take around 50 days, but during that trip – and for 27 days afterward – the sunshade will keep the sun from shining on the cameras, allowing them to cool down. There’s also a cryocooler on board that will take 19 days to cool the cameras to their operating temperature (using enough helium to fill nine party balloons). It’s a cutting edge thing. “It’s relatively easy to cool something to this temperature on Earth, but these Earth systems are very large and energy efficient,” said Konstantin Penanen, a cryogenic cooler specialist at NASA’s Jet Propulsion Laboratory in Southern California, which manages the MIRI instrument for Nasa. “For a space observatory, we need a cooler that is physically compact, very energy efficient, and it has to be very reliable because we can’t go out and fix it. ”

This is essential because Webb is self-contained after launch. If something is wrong with its incredibly detailed deployment sequence, or at any time during his mission, then Webb almost certainly cannot be fixed. It’s going to be too far (but never underestimate NASA!). It’s different from Hubble, which has had its cameras upgraded several times by visiting NASA astronauts hitchhiking in a space shuttle (before they were grounded in 2011).

In terms of risk versus value for your money, Webb is as big as the bang. The coolest cameras in the solar system now just need a home in space from which they can change astronomy as we know it.

Further reading:
The best telescopes for astrophotography

The best lenses for astrophotography

Astrophotography tips: how-to guides and videos

The best camera for astrophotography


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