Yesterday NASA’s James Webb Space Telescope was successfully launched into space from French Guiana, using the European Space Agency’s Ariane 5 rocket. If all goes well, within the next year we will be seeing images of when the universe was in its infancy.
Here is a quick overview of the telescope.
The launch is just the first stage of a very complex journey in which engineers have said that there are many delicate steps that need to go right and the failure of any one could ruin the mission.The telescope is a truly extraordinary piece of engineering design.
The James Webb – named after a former Nasa administrator – will spend a month on its journey and will then need a further five months to get ready. First, its enormous gold-plated 6.5 metre mirror and its huge, tennis-court-sized sunshield need to unfurl; they were folded origami-style to fit into the nose cone of the Ariane 5. Then its instruments will have to be carefully calibrated. In all, hundreds of release mechanisms need to work perfectly in order for the telescope to succeed.
This animation shows all the steps that go into unfolding the massive instrument.
Here is more about the design.
On its way, the telescope will slowly unfurl five silvery winglike layered sheets of Kapton foil, about as large as a tennis court. These sheets, each thinner than notebook paper, will function as a gigantic parasol, protecting the body of the telescope from the light and the heat of the sun, moon, and Earth. In this way, the J.W.S.T. will be kept nearly as dark and as cold as outer space, to insure that distant signals aren’t washed out. Then eighteen hexagons of gold-coated beryllium mirror will open out, like an enormous, night-blooming flower. The mirrors will form a reflecting surface as tall and as wide as a house, and they will capture light that has been travelling for more than thirteen billion years.
The telescope’s home will be one of the Lagrange points in space of the Earth-Sun combination.
Joseph-Louis Lagrange was an 18th century mathematician who found the solution to what is called the “three-body problem.” That is, is there any stable configuration, in which three bodies could orbit each other, yet stay in the same position relative to each other? As it turns out, there are five solutions to this problem – and they are called the five Lagrange points, after their discoverer. At Lagrange points, the gravitational pull of two large masses precisely equals the centripetal force required for a small object to move with them. The L1, L2, and L3 points are all in line with each other – and L4 and L5 are at the points of equilateral triangles.
Webb will not be stationary at the second Lagrange point L2, 1.5 million km away, but will instead orbit it.
The James Webb Space Telescope will not be in orbit around the Earth, like the Hubble Space Telescope is – it will actually orbit the Sun, 1.5 million kilometers (1 million miles) away from the Earth at what is called the second Lagrange point or L2. What is special about this orbit is that it lets the telescope stay in line with the Earth as it moves around the Sun. This allows the satellite’s large sunshield to protect the telescope from the light and heat of the Sun and Earth (and Moon).
This location was chosen to keep the telescope cold. Why does it need to be kept so cold? Because the telescope is designed to detect ‘light’ from the very earliest stars that were created about 13.5 billion years ago, just a a couple of hundred thousand years after the Big Bang. Because of the expansion of the universe, the light emitted by those stars has stretched out immensely (this is called the cosmological red shift), well out of the visible light range and into the infra-red region. Our atmosphere blocks out this range of frequencies but Webb will be able to detect it.
Here is an animation of the telescope’s orbit (not to scale).
There has been some controversy over the name of this telescope. Usually these things are named after significant contributors to science such as Galileo, Hubble, Spitzer, and Chandrasekhar. Webb was an administrator with NASA, a Washington insider, a consummate bureaucrat, and very effective at getting NASAS established and funded. There were protests about this choice.
Earlier this year, over 1,200 people, mostly astronomers or astronomy enthusiasts – including scholars who want to use the new telescope for their own research – signed a petition urging NASA to rename the telescope, saying that Webb seems to have been complicit in the purge of homosexual people from government jobs during his time in public service, including when he served in a high-level position in the U.S. State Department.
They cite evidence such as the interrogation of NASA employee Clifford Norton, who was fired in 1963 while Webb was directing the agency. “The historical record is already clear: under Webb’s leadership, queer people were persecuted,” the letter says.
“At best, Webb’s record is complicated,” says Chanda Prescod-Weinstein, a cosmologist at the University of New Hampshire who co-authored an article calling for the telescope to be renamed. “And at worst, we’re basically just sending this incredible instrument into the sky with the name of a homophobe on it, in my opinion.”
She notes that Norton was arrested for gay activity, interrogated by the police, and then picked up by NASA’s head of security and questioned at the agency.
“I haven’t seen evidence that Webb knew about this incident,” she says. “But I think we have two options here: Either he was a wildly incompetent administrator and didn’t know that his head of security was interrogating employees in NASA facilities, or he knew exactly what was going on and he was in some sense party to overseeing the interrogation of someone for being gay.”
NASA has said that they will not change the name.