Dubai: The James Webb Space Telescope has just arrived at its observation post after covering 1.6 million kilometres over a month. It is one of the most expensive scientific platforms ever built, comparable to the Large Hadron Collider at CERN, and its predecessor telescope, Hubble, and is designed to give the world an unprecedented glimpse of infant galaxies in the early stages of the universe.
Here’s a look at what else we know about the new space telescope.
What is special about the James Webb Space Telescope?
The James Webb Space Telescope is the world’s biggest, most powerful space telescope. The $10 billion observatory was launched from French Guiana on December 25. Ten days later a sunshield as big as a tennis court stretched open on the telescope. The instrument’s gold-coated primary mirror - 21 feet (6.5 metres) across - unfolded a few days later. The primary mirror has 18 hexagonal segments, each the size of a coffee table, that will have to be aligned so that they see as one - a task that will take three months.
With a final five-minute, course-correcting thrust of its onboard rocket, Webb has reached its destination at a position of gravitational equilibrium.
What will the telescope do?
The telescope will enable astronomers to peer back further in time than ever before, all the way back to when the first stars and galaxies were forming 13.7 billion years ago. That’s 100 million years from the Big Bang, when the universe was created. Besides making stellar observations, Webb will scan the atmospheres of alien worlds for possible signs of life.
Its mission also includes the study of distant planets, known as exoplanets, to determine their origin, evolution and habitability.
The main reason astronomers build larger telescopes is to increase light-gathering power so that they can see deeper into the universe.
The word ‘telescope’ comes from the Italian word telescopio which appeared in the early 1600s. The English form ‘telescope’ appeared in 1650.
How will it stay in place?
The Webb is positioned at the so-called second Lagrange point, or L2, where it will have access to nearly half the sky at any given moment. At L2, it will stay in line with the Earth as it moves around the Sun, allowing Webb’s sunshield to protect its sensitive equipment from heat and light.
For the giant parasol to offer effective protection, it needs the Sun, Earth and Moon to all be in the same direction, with the cold side operating at -225 Celsius.
What is the Legrange point?
The Lagrange point is an area of space where the gravitational pull from the Sun and Earth will be balanced by the centrifugal force of the rotating system.
The Earth-sun orbital relationship produces five Lagrange points, which scientists number L1 through L5. Placing the telescope at L2 - perpetually in Earth’s shadow, shielded from the sun’s radiation and glare - will allow it to look farther, while also keeping its sensitive instruments at the super-cold temperatures they need to operate.
In the 18th century, Italian French mathematician Joseph-Louis Lagrange determined that celestial bodies’ overlapping gravity wells would produce areas where the pull of gravity and the push of centrifugal force would offset. A small object at such a point would not fall toward the sun or Earth, but would remain more or less stable. These are the Lagrange points.
Ordinarily, an object orbiting closer to the sun’s gravity well would have a faster orbit. An object orbiting farther away from the sun would have a slower orbit.
In addition to the sun’s gravity, though, Earth’s gravity also pulls on objects at these points, slowing the orbit of objects at L1 and speeding up objects at L2. Objects at these points orbit the sun at “Earth speed” as they balance between the gravity wells.
The James Webb Space Telescope will orbit L2.
This particular Lagrange point is not completely stable: The interweaving pulls of gravity between Earth, the moon, the sun and other forces will require the James Webb Space Telescope to make occasional, minor adjustments to maintain its orbit around L2. The spacecraft is designed to carry enough propellant to make these adjustments for at least 10 years. However, NASA reports that a smoother-than-anticipated journey to the Lagrange point will leave the James Webb telescope with additional fuel, extending its useful life span.
Previous missions to L2 include the European Space Agency’s Herschel and Planck observatories, and NASA’s Wilkinson Microwave Anisotropy Probe. Webb’s position will also allow continuous communications with Earth via the Deep Space Network - three large antennas in Australia, Spain and California.
Galileo Galilei revolutionised astronomy when he applied the telescope to the study of extraterrestrial bodies in the early 17th century.
What happens next?
The mirrors on the observatory must be meticulously aligned, the infrared detectors sufficiently chilled and the scientific instruments calibrated before observations can begin in June or July.
How long will the telescope survive?
Although the planned minimum life for Webb is five years, managers are confident it will be active for at least two decades.
What came before the James Webb Space Telescope?
Way back in the 1970s, the European Space Agency, the National Aeronautics and Space Administration worked together to design and build the Hubble Space Telescope.
On April 25, 1990, five astronauts aboard the space shuttle Discovery deployed the telescope in an orbit 600 km above the Earth’s surface.
The unprecedented images procured by Hubble Space Telescope finally saw the dawn of a new era in space exploration.
And that resulted in the realization of a 50-year dream and more than two decades of dedicated collaboration between scientists, engineers and institutions from all over the world.
Hubble’s important mission will come to an end soon. But the telescope’s ultimate retirement will not signal the end of our unrivaled view of the universe.
Video: Comparison of Webb and Hubble
Mirror size comparison of Webb and Hubble. Note the human reference at the bottom for scale. Credit: GSFC
Quick facts about Hubble Space Telescope
Hubble Space Telescope is named after the trailblazing astronomer Edwin Hubble.
Hubble’s capabilities have grown immensely in its over 30 years of operation.
Hubble has made more than 1.5 million observations over the course of its lifetime.
Over 19,000 peer-reviewed science papers have been published on its discoveries.
The telescope has tracked interstellar objects as they soared through our solar system, watched a comet collide with Jupiter, and discovered moons around Pluto.
It has found dusty disks and stellar nurseries throughout the Milky Way.
Hubble has peered back into our universe’s distant past, to locations more than 13.4 billion light-years from Earth, capturing galaxies merging, probing the supermassive black holes that lurk in their depths, and helping us better understand the history of the expanding universe.
