50 Fun Facts About James Webb Space Telescope

In which part of the spectrum does Webb mainly observe?

Its range runs from long-wavelength visible red through the mid-infrared, 0.6 to 28.5 micrometres.

On what date was Webb launched?

It lifted off on an Ariane 5 from Kourou, French Guiana, in a launch Space.com called "flawless".

Which rocket carried Webb into space?

The European launcher was part of ESA's contribution to the partnership.

Where does Webb orbit?

L2 is about 1.5 million km from Earth; Hubble, by contrast, circles just 550 km up.

Roughly how far from Earth is the L2 point where Webb sits?

That is about four times farther out than the Moon.

How many hexagonal segments make up Webb's primary mirror?

Together they form a 6.5-metre mirror, against Hubble's single 2.4-metre disc.

What metal are Webb's mirror segments made of?

Beryllium is light, very stiff and holds its shape at cryogenic temperatures; the gold coat reflects infrared.

What is the diameter of Webb's primary mirror?

It collects about six times as much light as Hubble.

Below what temperature must Webb be kept so its own heat does not blind it?

Otherwise the telescope's own heat glow would swamp the faint light it is collecting.

How many layers does Webb's sunshield have?

Each is Kapton E film about 0.1 mm thick, coated with aluminium on both sides.

What sun protection factor does the sunshield effectively have?

Suntan lotion manages 8 to 50.

How many times was the sunshield folded to fit inside the rocket fairing?

Fully open it measures about 14 by 21 metres, roughly a tennis court.

How much of the sky can Webb see from any one position?

Over six months, as it moves around the Sun, it can reach the whole sky.

How many small actuator motors position and adjust Webb's optics?

They can place the mirror segments to an accuracy of 10 nanometres.

Why do bright stars in Webb images show six diffraction spikes?

Two fainter spikes appear too; Hubble's four-spike pattern comes from its support struts.

What kind of optical design does Webb use?

Curved secondary and tertiary mirrors give aberration-free images across a wide field.

Which Webb instrument also serves as the wavefront sensor that aligns the mirror?

It was built by a team led by the University of Arizona under Marcia Rieke.

Who built the NIRSpec spectrograph?

Its microshutter array lets it take spectra of hundreds of objects at once.

Which instrument must be kept below 6 K by a helium cryocooler?

The Mid-Infrared Instrument covers 5 to 27 micrometres and is led by George Rieke and Gillian Wright.

Which country's space agency supplied the Fine Guidance Sensor and NIRISS?

NIRISS was led by René Doyon at the Université de Montréal.

Which company was Webb's prime contractor?

It inherited the contract when it bought TRW in a hostile bid in 2003; Ball built the telescope optics.

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

STScI in Baltimore also runs Hubble and sits on Johns Hopkins' Homewood campus.

James E. Webb ran NASA during which years?

He oversaw Mercury, Gemini and most of Apollo; the telescope took his name in 2002.

What was the project called before it was renamed in 2002?

NASA administrator Sean O'Keefe made the change to honour his Apollo-era predecessor.

What was the original budget estimate for Webb in 1999?

The final bill came to about US$10 billion, and the planned 2007 launch slipped 14 years.

Which NASA administrator coined "faster, better, cheaper" and pushed segmented mirrors?

Breaking the single-mirror barrier meant learning to live with moving parts.

Who was Webb's project scientist at Goddard during development?

Mather shared the 2006 Nobel Prize in Physics for COBE's measurements of the cosmic microwave background.

What happened in a 2018 practice deployment that delayed the launch by two years?

An independent review then counted 344 single-point failures that all had to go right.

How many potential single-point failures did the review identify in Webb's launch and deployment?

Each was a step with no backup; every one had to succeed for the telescope to work.

In which year did a House committee move to cancel the Webb project?

Congress reversed course in November and capped the remaining budget at US$8 billion.

A 2010 Nature article described Webb as what?

Scientists worried its budget was starving other space science programmes.

Which Webb director was credited with lifting on-time task completion from 50% to 95%?

His boss Thomas Zurbuchen called him "the most effective leader of a mission I have ever seen in the history of NASA".

How did Webb travel from California to its launch site?

It left on 26 September 2021 and reached French Guiana on 12 October.

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

The sunshield must stay between the telescope and the Sun, so overshooting would have been unrecoverable.

How long might Webb's fuel last thanks to the precise launch, instead of the planned decade?

Ariane 5's accuracy and a lean first course correction saved a large share of the propellant.

On what date did Webb arrive at L2?

A third and final course correction inserted it into its halo orbit a month after launch.

Which star was used to align the 18 mirror segments?

The 7th-magnitude star in Ursa Major first appeared as 18 separate blurry images.

To what accuracy must each mirror segment be positioned?

NASA's analogy: segments the size of Texas lined up to within about 1.5 inches.

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

The image of galaxy cluster SMACS J0723.3-7327 shows background galaxies lensed from 13.1 billion years ago.

Which galaxy cluster is the subject of Webb's First Deep Field?

Three ancient galaxies from shortly after the Big Bang were later spotted in the frame.

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

The star-forming region NGC 3324 lies about 8,500 light-years away.

Webb's first release included evidence of water in the atmosphere of which exoplanet?

The gas giant orbits a star 1,120 light-years from Earth.

Stephan's Quintet, in the first images, is a group of how many galaxies?

Four of them sit about 290 million light-years away, colliding and sparking new stars.

Which galaxy, found in May 2024, was the most distant known at the time?

Its redshift of 14.32 and surprising brightness challenge models of early galaxy formation.

Which mirror segment took a notable micrometeoroid hit in May 2022?

Strikes happen once or twice a month; engineers now steer clear of "avoidance zones" in the orbit.

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

Nombas ScriptEase 5.00e scripts are interpreted by flight software written in C++.

How large is Webb's solid-state drive for storing science data?

Radiation and wear are expected to shrink it to about 60 GB by the end of the ten-year mission.

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

It launched with 159 litres of hydrazine and 79.5 litres of dinitrogen tetroxide oxidiser.

Which two agencies partnered with NASA on Webb?

ESA supplied NIRSpec, part of MIRI and the Ariane launch; Canada the guidance sensor and NIRISS.

Roughly how many proposals competed for Webb's Cycle 4 observing time?

They asked for 78,000 hours, nine times what was available.