Telescope that 'ate astronomy' is on track
Dennis Overbye, Nov 29, 2016, NYT
The next great space telescope spread its golden wings this month. Like the petals of a 20-foot sunflower seeking the light, the 18 hexagonal mirrors that make up the heart of NASA’s James Webb Space Telescope were faced towards a glassed-in balcony overlooking a cavernous clean room at the Goddard Space Flight Centre in Greenbelt, Maryland, USA. Now, after 20 years with a budget of $8.7 billion, the Webb telescope is on track and on budget to be launched in October 2018 and sent one million miles from Earth, NASA says.
The telescope, named after NASA Administrator James Webb, who led the space agency in the 1960s, is the long-awaited successor of the Hubble Space Telescope. Seven times larger than the Hubble in light-gathering ability, the Webb was designed to see farther out in space and deeper into the past of the universe. It may solve mysteries about how and when the first stars and galaxies emerged some 13 billion years ago. Equipped with the sort of infrared goggles that give troops and police officers night vision, the Webb would peer into the dust clouds and gas storms of the Milky Way in which stars and planets are being birthed. It would be able to study planets around other stars.
That has been NASA’s dream since 1996 when the idea for the telescope was
conceived with a projected price tag then of $500 million. But as recently as six years ago, the James Webb Space Telescope was, in the words of Nature magazine, “the telescope that ate astronomy,” mismanaged, over budget and behind schedule so that it had crushed everything else out of NASA’s science budget. A House subcommittee once voted to cancel it. Instead, the programme was rebooted with a strict spending cap.
Ambitious project
The scientific capabilities of the telescope emerged unscathed from that period,
astronomers on the project say. The major change, said Jonathan P Gardner, deputy senior project scientist, was to simplify the testing of the telescope. Typically for NASA, the Webb telescope was a technologically ambitious project, requiring 10 new technologies to make it work. Bill Ochs, a veteran Goddard engineer who became project manager in 2010 during what he calls the “replan,” said the key to its success so far was having enough money in the budget to provide a cushion for nasty surprises.
The telescope smiling up at us like a giant Tiffany shaving mirror is 6.5 metres in
diameter, or just over 21 feet, compared with 2.4 metres for the Hubble. The aim is to explore a realm of cosmic history about 150 million to one billion years after time began — known as the reionisation epoch, when bright and violent new stars and the searing radiation from quasars were burning away a gloomy fog of hydrogen gas that prevailed at the end of the Big Bang.
In fact, astronomers don’t know how the spectacle that greets our eyes every night wrenched itself into luminous existence. They theorise that an initial generation of stars made purely of hydrogen and helium burned ferociously and exploded apocalyptically, jump-starting the seeding of the cosmos with progressively more diverse materials. But nobody has ever seen any so-called Population 3 stars, as those first stars are known. They don’t exist in the modern universe. Astronomers have to hunt them in the dim past.
That ambition requires the Webb to be tuned to a different kind of light than our eyes or the Hubble can see. Because the expansion of the cosmos is rushing those earliest stars and galaxies away from us so fast, their light is ‘red-shifted’ to longer wavelengths the way the siren from an ambulance shifts to a lower register as it passes by. So, blue light from an infant galaxy bursting with bright spanking new stars way back then has been stretched to invisible infrared wavelengths, or heat radiation, by the time it reaches us 13 billion years later.
Cosmic postcards
As a result, the Webb telescope will produce cosmic postcards in colours no eye has ever seen. It also turns out that infrared emanations are the best way to study exoplanets, the worlds beyond our own solar system that have been discovered in the thousands since the Webb telescope was first conceived. In order to see those infrared colours, however, the telescope has to be very cold — less than 45 degrees Fahrenheit above absolute zero — so that its own heat does not swamp the heat from outer space. Once in space, the telescope will unfold a giant umbrella the size of a tennis court to keep the sun off it. The telescope, marooned in permanent shade one million miles beyond the moon, will experience an infinite cold soak.
The last time NASA did something this big astronomically, in 1990, things didn’t quite work. Once in orbit, the Hubble couldn’t be focused; it had a misshapen mirror that had never been properly tested. Astronauts eventually fitted it with corrective lenses, and it went on to become the crown jewel of astronomy. Making sure that doesn’t happen this time is the agenda for the next two years. “Our telescope is finished,” said John C Mather, the senior project scientist. “Now we are about to prove it works.”
The telescope, named after NASA Administrator James Webb, who led the space agency in the 1960s, is the long-awaited successor of the Hubble Space Telescope. Seven times larger than the Hubble in light-gathering ability, the Webb was designed to see farther out in space and deeper into the past of the universe. It may solve mysteries about how and when the first stars and galaxies emerged some 13 billion years ago. Equipped with the sort of infrared goggles that give troops and police officers night vision, the Webb would peer into the dust clouds and gas storms of the Milky Way in which stars and planets are being birthed. It would be able to study planets around other stars.
That has been NASA’s dream since 1996 when the idea for the telescope was
conceived with a projected price tag then of $500 million. But as recently as six years ago, the James Webb Space Telescope was, in the words of Nature magazine, “the telescope that ate astronomy,” mismanaged, over budget and behind schedule so that it had crushed everything else out of NASA’s science budget. A House subcommittee once voted to cancel it. Instead, the programme was rebooted with a strict spending cap.
Ambitious project
The scientific capabilities of the telescope emerged unscathed from that period,
astronomers on the project say. The major change, said Jonathan P Gardner, deputy senior project scientist, was to simplify the testing of the telescope. Typically for NASA, the Webb telescope was a technologically ambitious project, requiring 10 new technologies to make it work. Bill Ochs, a veteran Goddard engineer who became project manager in 2010 during what he calls the “replan,” said the key to its success so far was having enough money in the budget to provide a cushion for nasty surprises.
The telescope smiling up at us like a giant Tiffany shaving mirror is 6.5 metres in
diameter, or just over 21 feet, compared with 2.4 metres for the Hubble. The aim is to explore a realm of cosmic history about 150 million to one billion years after time began — known as the reionisation epoch, when bright and violent new stars and the searing radiation from quasars were burning away a gloomy fog of hydrogen gas that prevailed at the end of the Big Bang.
In fact, astronomers don’t know how the spectacle that greets our eyes every night wrenched itself into luminous existence. They theorise that an initial generation of stars made purely of hydrogen and helium burned ferociously and exploded apocalyptically, jump-starting the seeding of the cosmos with progressively more diverse materials. But nobody has ever seen any so-called Population 3 stars, as those first stars are known. They don’t exist in the modern universe. Astronomers have to hunt them in the dim past.
That ambition requires the Webb to be tuned to a different kind of light than our eyes or the Hubble can see. Because the expansion of the cosmos is rushing those earliest stars and galaxies away from us so fast, their light is ‘red-shifted’ to longer wavelengths the way the siren from an ambulance shifts to a lower register as it passes by. So, blue light from an infant galaxy bursting with bright spanking new stars way back then has been stretched to invisible infrared wavelengths, or heat radiation, by the time it reaches us 13 billion years later.
Cosmic postcards
As a result, the Webb telescope will produce cosmic postcards in colours no eye has ever seen. It also turns out that infrared emanations are the best way to study exoplanets, the worlds beyond our own solar system that have been discovered in the thousands since the Webb telescope was first conceived. In order to see those infrared colours, however, the telescope has to be very cold — less than 45 degrees Fahrenheit above absolute zero — so that its own heat does not swamp the heat from outer space. Once in space, the telescope will unfold a giant umbrella the size of a tennis court to keep the sun off it. The telescope, marooned in permanent shade one million miles beyond the moon, will experience an infinite cold soak.
The last time NASA did something this big astronomically, in 1990, things didn’t quite work. Once in orbit, the Hubble couldn’t be focused; it had a misshapen mirror that had never been properly tested. Astronauts eventually fitted it with corrective lenses, and it went on to become the crown jewel of astronomy. Making sure that doesn’t happen this time is the agenda for the next two years. “Our telescope is finished,” said John C Mather, the senior project scientist. “Now we are about to prove it works.”
No comments:
Post a Comment