How Hubble Successor James Webb Telescope Can Greatly Expand Our Understanding Of The Universe

Update (2): Webb lifted off on 25 December 2021.

Update (1): Webb will launch at 7:20 am Eastern Standard Time (5:50 pm Indian Standard Time) on Friday, 24 December.

Planet Earth is set to get a new pair of advanced eyes in space that will be able to peer far — really far — out into the universe in search of answers to fundamental questions.

Called the James Webb Telescope, this next great space science observatory — walking in the footsteps of the Hubble Space Telescope and Herschel Space Observatory — is just days away from being shot up to its very particular destination in space.

Webb is set for launch on 22 December 2021 from Europe's Spaceport in French Guiana on board a rocket made for the job, the French Ariane 5 launch vehicle.

The telescope, the product of a collaboration between the National Aeronautics and Space Administration (NASA), European Space Agency (ESA), and Canadian Space Agency, will be the biggest one ever launched into space.

Its destination is the Lagrange point 2 or L2, which is situated 15 lakh kilometres (km) from Earth.

Named after the Italian-born mathematician and astronomer Joseph-Louis Lagrange, the Lagrange point is a spot in space where gravity from the Sun and Earth balance the orbital motion of a satellite. A spacecraft at this point stays in a fixed position relative to the Sun and Earth.

There are five Lagrange points in all, and L2, where Webb will settle down for its life of science, is one of them.

L2 is not a fixed point, but follows Earth around the Sun. Webb, for its purposes, will not occupy the prized L2 spot, but rather orbit it facing away from the Sun. The journey to L2 will take Webb roughly a month.

From here, the infrared telescope will be kept cold to cryogenic temperatures — because infrared is associated with heat radiation and interference from the Earth and Sun’s heat would spoil the party — with the help of both smart telescope positioning and the sunshield on board (which is the size of a tennis court), and be able to see the most dim yet cosmically significant objects located unfathomably far from us.

In her online public lecture for the Royal Astronomical Society (RAS), Dr Olivia Jones, an STFC Webb Fellow, based at the UK Astronomy Centre at the Royal Observatory Edinburgh, explained why Webb was necessary for new astronomy discoveries. “To win at astronomy, you need two things. You want to be building bigger and bigger telescopes to make new discoveries and you want to look potentially with these big telescopes in new wavelength space,” she said.

Dr Jones, who has been involved in the project for a decade or so, describes Webb’s size as equivalent to a tennis court with a house attached. In comparison, the telescope’s predecessors, the NASA/ESA Hubble Space Telescope and Spitzer Space Observatory, are about the size of a double decker bus and a sports car respectively.

Webb’s mirror, 6.5 metres across and made up of 18 hexagonal, gold-coated mirror segments, is itself nearly double the size of the Herschel Space Observatory. Further, Webb’s sensitivity is 100 times greater than that of the Hubble telescope.

Additionally, while Hubble has been operating primarily in the visible light spectrum, Webb will use infrared vision. Therefore, working together with Hubble, this next-generation telescope promises to uncover new details about the universe that will transform our understanding.

According to ESA, Webb will allow scientists to directly observe the first stars and galaxies forming in the early universe from more than 13.5 billion years ago. This is not long after the Big Bang.

When the light from these objects falls upon Webb, the observatory will capture this information that was coded all those many years ago. It will give the effect of looking far back in time, acting, therefore, like a time machine.

Data taken from Webb will shed light on the workings of black holes in the early universe — especially their formation and evolution and how, if at all, they contributed to the making of the universe over time.

Additionally, questions of the lifecycle of stars, galaxies, formation and evolution of planetary systems (including our solar system), and exoplanets as well as of possible life-producing ingredients that may be found, say, in the atmospheres of exoplanets, will be explored.

“Webb will search for atmospheres similar to Earth’s, and for the signatures of key substances such as methane, water, oxygen, carbon dioxide and complex organic molecules, in the exciting hope of finding the building blocks of life,” ESA says.

Webb will begin collecting scientific data six months after launch. Four piggyback instruments will help with this task — near-infrared spectrograph (NIRSpec), mid-infrared instrument (MIRI), near-infrared camera (NIRCam), and near-infrared imager and slitless spectrograph (NIRISS) with the fine guidance sensor (FGS).

NIRSpec, set to be the first multi-object spectrograph in space, will provide low, medium, and high-resolution spectroscopic observations in the near-infrared range (0.6 to 5.0 microns).

With the help of NIRSpec, scientists will be able to study cosmic objects hidden away by gas and dust, so as to learn about galaxies, and rummage the atmospheres of exoplanets to determine if there is water. The instrument is provided by ESA.

MIRI will cover the mid-infrared wavelength range from 5 to 28.3 microns. It will be able to look at the first generation of galaxies being formed after the Big Bang, in addition to sites of new planet formation, make-up of the interstellar medium, and exoplanets.

MIRI will be cooled down to close to -266 degrees Celsius, which will make it over 30 degrees cooler than the rest of Webb.

“The universe is relatively unexplored at mid-infrared wavelengths,” George Rieke, professor of astronomy at the University of Arizona, and Gillian Wright, director of the UK Astronomy Centre, told NASA. MIRI will see the universe in this "unexplored" band.

A 50 per cent share of MIRI has come from ESA.

NIRCam is Webb's primary imager. It was developed by the University of Arizona and Lockheed Martin. The camera will operate in the infrared wavelength range of 0.6 to 5 microns.

NIRISS will provide direction to Webb — by helping point the telescope — so that it can snap high-quality images. It has a wavelength range of 0.8 to 5.0 microns. The instrument is supplied by the Canadian Space Agency.

At Europe’s Spaceport in French Guiana, Webb was fuelled on 6 December and transferred to the final assembly building the next day, on 7 December. The Ariane 5 rocket has been stationed in this building since the end of November.

Next, the telescope will be integrated on Ariane 5’s upper stage and encapsulated within the fairing. And then, it will be set for launch on 22 December. Thereafter, it will be six months before the first science images come through.

Webb, which has been more than 30 years in the making and carrying a price tag of $10 billion, is sure to run for at least five years. The limiting factor is the fuel, which is going to be necessary for course corrections. The fuel will, after all, be used to move the telescope around.

“Ideally, you want a 10-year mission. That’s the goal. For instance, other telescopes had similar missions and have been lasting much longer. I hope the same will happen for Webb as well,” Dr Jones said in her RAS online public lecture.

Hubble too had an expected lifespan of 15 years when it was launched. Thanks to astronaut servicing missions, which will unfortunately not be available to Webb, it has remained busy.

And not just busy — operating since 1990, and expected to work until the late 2020s if not beyond that, Hubble has revolutionised astronomy and forever changed how we see the universe.

From Webb, one can expect nothing less.