48 Fun Facts About James Webb Space Telescope

Webb was built to look far enough back in time to see what?

The first galaxies forming. Their light set out over 13 billion years ago and has been stretched into the infrared on the way, which is why Webb was built as an infrared telescope.

Webb finally lifted off on which holiday in 2021?

Christmas Day. Liftoff had been set for Christmas Eve until a poor weather forecast at the launch site pushed it back by 24 hours.

Which rocket carried Webb into space?

Ariane 5. Europe supplied the launch at no charge, and in return its astronomers were guaranteed roughly 15 percent of Webb's observing time.

Where does Webb orbit?

Near the Sun–Earth L2 point. From there the Sun, Earth and Moon always sit in the same part of the sky, so a single sunshield can block the heat of all three at once.

Webb was launched from a spaceport on South American soil belonging to which country?

France. The spaceport is in French Guiana, an overseas region about five degrees from the equator, where Earth's spin gives a departing rocket an extra push.

What metal are Webb's mirror segments made of?

Beryllium. It was chosen for being light, stiff and steady in shape in deep cold, which is why each 1.3-metre segment weighs only about 20 kilograms.

Webb's mirror dwarfs Hubble's; how does Webb's mass compare?

About half. A mirror made like Hubble's and scaled up would have been too heavy to launch, so Webb's had to be about ten times lighter for its size.

Why must Webb's telescope be kept below about −223°C?

Its own glow would blind it. Anything warm shines in the infrared light Webb collects, so it has to be far colder than Hubble, which is kept at about room temperature.

What fills the gaps between Webb's five sunshield layers?

Nothing. The vacuum between the layers is a very good insulator, and each layer runs cooler than the one below as its heat radiates out sideways through the gaps.

What sun protection factor does Webb's sunshield effectively have?

1,000,000. Its five layers cut more than 200 kilowatts of solar energy to a fraction of a watt by the time it reaches the telescope.

Webb's open sunshield is about the size of what?

A tennis court. The ground team unfolded and tightened it by remote command over eight days, finishing ten days after launch.

What limits Webb to about 40 percent of the sky at once?

Its need for shade. Pointing too close to the Sun would let heat reach the cold mirror, but its window drifts as the months pass, so the whole sky comes into view every six months.

In 2022 Webb took the clearest picture of which planet's rings since Voyager 2 flew past in 1989?

Neptune. Some of its faint rings had not been seen at all since that flyby, and the planet famous for its blue colour does not look blue to Webb's infrared camera.

Why do bright stars in Webb's images show a distinctive pattern of long spikes?

Its hexagonal mirror segments. Light bends at the segments' straight edges to draw six big spikes, and the struts holding the small second mirror add two fainter ones.

In 2022 Webb and Hubble both watched NASA deliberately crash which spacecraft into an asteroid?

DART. It was the first time the two telescopes watched the same target at once, and the crash shortened the little moon's orbit by 32 minutes, proof that an asteroid can be nudged.

Webb spotted a watery plume more than 9,600 km long spraying from which moon of Saturn?

Enceladus. It gushes water fast enough to fill an Olympic swimming pool in a couple of hours, and Webb showed the plume feeding a doughnut-shaped cloud of water around Saturn.

What do the 248,000 tiny shutters in Webb's NIRSpec instrument let it do?

Study about 100 objects at once. Each door is only a few hairs wide and opens on command, so one exposure can split the light of 100 chosen galaxies while the rest of the sky stays blocked.

Which part of Webb needs its own helium refrigerator to run far colder than the rest?

The Mid-Infrared Instrument. Longer wavelengths need colder detectors, so while the sunshield alone chills the others to around 40 kelvin, this one is pumped down below 7.

Besides NASA and the European Space Agency, which country is a full partner in Webb?

Canada. It built the sensor that keeps Webb locked on its targets and one of the four science instruments, which earned Canadian astronomers a guaranteed share of observing time.

Which company was Webb's prime contractor?

Northrop Grumman. The contract went to TRW, which Northrop absorbed after a hostile takeover bid in 2002, so the telescope became Northrop's to build.

Which Baltimore organisation runs Webb's day-to-day operations?

Space Telescope Science Institute. The centre that plans Hubble's observations also sent nearly every command that unfolded Webb, and Webb's data is still sent there for processing.

Who was James E. Webb, the man the telescope honours?

NASA's chief in the 1960s. He was an attorney and manager, not a scientist or engineer, yet he ran the agency through the Apollo build-up and insisted it keep funding space science.

What was Webb called before it was renamed in 2002?

Next Generation Space Telescope. The working title marked it as the follow-up to Hubble, whose own planning name had been the Large Space Telescope.

Roughly how much had Webb cost by the time it launched in 2021?

$10 billion. When NASA formally committed to building it the estimate was about $5 billion for a 2014 launch, and under-funding in the early years let the delays snowball.

Webb was conceived under which 1990s NASA motto?

Faster, better, cheaper. Administrator Dan Goldin's motto stood for small, quick missions, yet the telescope planned under it became the reverse: a single giant that took a quarter of a century to launch.

Webb's senior project scientist John Mather shared a Nobel Prize for measuring what?

The Big Bang's afterglow. His COBE satellite showed the faint microwave glow matched what a hot early universe should leave behind, and he then led Webb's science team from 1995 until 2023.

What went wrong with Webb in a 2018 practice deployment, helping to push back its launch?

The sunshield ripped. Its tensioning cables also went slack, and NASA moved a launch planned for 2019 to no earlier than May 2020 to make time for repairs and more tests.

Which famous Hubble image of 1995 did Webb retake in 2022, revealing newborn stars inside the dust?

The Pillars of Creation. In Webb's near-infrared view the famous columns of gas and dust turn semi-transparent, so the newly formed stars inside them can be seen and counted.

In 2011 a US House committee voted to do what to Webb?

Cancel it. Astronomers reacted with dismay, and that November a compromise between the House and the Senate kept the telescope alive.

A 2010 Nature article described Webb as what?

The telescope that ate astronomy. The headline voiced a fear that Webb's swelling budget was swallowing the money for the other space-science missions NASA hoped to fly.

Which system carries Webb's data and commands to and from Earth?

The Deep Space Network. Its dishes in California, Spain and Australia take turns listening as Earth rotates, whereas Hubble, far closer in, talks through relay satellites in Earth orbit.

How did Webb travel from California to its launch site?

By ship through the Panama Canal. The folded telescope spent 16 days at sea, and NASA kept the dates of the voyage secret for security reasons.

Why was Webb launched with slightly too little speed rather than too much?

It could not turn to slow down. Webb's thrusters sit only on its warm, Sun-facing side, so they can push it outward but never back, and every burn is aimed a little low on purpose.

Why might Webb keep working for 20 years instead of the planned 10?

Its launch was so precise. The rocket set Webb on such an accurate path that little fuel was needed for course corrections, leaving far more than planned for the years of small orbit-keeping burns.

Before alignment, Webb saw one star as what?

Scattered dots. Each mirror segment made its own image, so engineers nudged the segments until the 18 blurry dots of HD 84406, a star in the Great Bear, stacked into a single sharp point.

To what accuracy must each of Webb's mirror segments be positioned?

50 nanometres. That is a fraction of a wavelength of the light Webb collects, which lets the separate segments behave as one mirror; a human hair is about 2,000 times thicker.

Who unveiled Webb's First Deep Field on 11 July 2022?

Joe Biden. He showed the picture at a White House event, one day ahead of NASA's own planned release of the telescope's first full-colour images.

Webb's First Deep Field covers a patch of sky about the size of what, held at arm's length?

A grain of sand. In that speck a 12.5-hour exposure caught thousands of galaxies, some of them seen as they were more than 13 billion years ago.

Which star-forming region did NASA dub the "Cosmic Cliffs" in Webb's first image release?

Carina Nebula. The 'cliffs' are the edge of a vast cavity that fierce ultraviolet light and winds from hot young stars, just above the frame, have carved out of the gas.

In its first data release, what did Webb detect in the atmosphere of the giant planet WASP-96 b?

Water vapour. The same spectrum showed signs of clouds and haze on a hot, puffy planet that earlier studies had judged to be cloud-free.

Stephan's Quintet, one of Webb's first targets, plays talking angels at the start of which 1946 film?

It's a Wonderful Life. The film opens on the galaxy group as heavenly voices talk; Webb's picture shows that one of the five is really a foreground galaxy, far closer than the rest.

What surprised astronomers about JADES-GS-z14-0, the record-distant galaxy Webb confirmed in 2024?

How bright and big it was. Seen less than 300 million years after the Big Bang, it already spans over 1,600 light-years, more growth than theories had allowed so early.

In May 2022, what struck one of Webb's mirror segments?

A micrometeoroid. The dust-sized particle left a permanent blemish on one segment, but after the mirror was realigned its sharpness stayed well within design limits.

Webb's on-board operations run on a modified version of which language?

JavaScript. Commands are kept as readable scripts so operators can change them as they learn the instruments, and they run on an engine last updated in 2003 by a company that no longer exists.

Webb fills its 68 GB data drive in about how long?

A day. So Webb has to send its data home about twice daily, in scheduled radio contacts that empty the drive well before it fills.

What does Webb use as rocket fuel for course corrections and station-keeping?

Hydrazine. Besides holding Webb in its orbit, the fuel is spent countering sunlight itself, which presses steadily on the huge sunshield and has to be offset to keep the telescope under control.

The gold on Webb's main mirror weighs about as much as what?

A golf ball. Spread over the whole mirror it makes a microscopically thin coat, and it is there because gold reflects infrared light extremely well.

In Webb's First Deep Field, what smears some distant galaxies into long arcs?

A nearer cluster's gravity. The cluster's mass bends and magnifies light from galaxies far behind it, a natural lens that brings fainter, older galaxies into view.