SAN FRANCISCO — NASA’s next-generation space telescope could confirm the existence of the oldest galaxy yet seen and peer back even further in time, according to researchers.
Astronomers using NASA’s Hubble Space Telescope announced Jan. 26 that they spotted a galaxy that formed less than 500 million years after the Big Bang, making it the oldest and farthest galaxy ever seen. While the scientists are confident in their discovery, a new instrument likely will be required to confirm the galaxy’s age and existence definitively, researchers said.
That instrument is the infrared James Webb Space Telescope (JWST), NASA’s powerful successor to Hubble. JWST, which could launch in the fall of 2015, also will look back even further in time, to just a few hundred million years after the universe’s birth, researchers said.
“We’re really pushing Hubble to its limits here,” study co-author Garth Illingworth of the University of California, Santa Cruz (UCSC), told reporters during a press conference on the oldest galaxy. “We’re looking excitedly to the future, to using the James Webb Space Telescope to really unearth the earlier times that Hubble in fact won’t be able to see.”
Confirming the Find
The researchers, led by Rychard Bouwens of UCSC and Leiden University in the Netherlands, performed a number of tests after the initial discovery. They are confident that the ancient galaxy — named UDFj-39546284 — exists, and that it dates to about 480 million years after the Big Bang that scientists think began the universe, which is about 13.7 billion years old.
“It’s not 100 percent. There’s no way we can guarantee that,” Illingworth said. “But we think it’s very likely.”
To officially confirm finds such as galaxy UDFj-39546284, astronomers usually measure spectra of the objects so they can study their light in detail. Typically, scientists use ground-based instruments for such follow-up work.
However, at about 13.2 billion light-years away, UDFj-39546284 is so faint and distant that no ground-based telescope can do the job, Illingworth said.
“Ultimately, to get the same level of confidence, we’ll need the James Webb Space Telescope,” he said. “This is incredibly faint. We can’t do anything with our current ground-based telescopes on this.”
James Webb also will be able to peer back further in time, researchers said. Hubble’s capabilities max out at about 480 million years after the universe’s birth, but JWST should be able to see objects that formed just 200 million or 300 million years after the Big Bang.
That difference may not seem like much, but it is a big deal, Illingworth said. Astronomers could gain key insights about the earliest epochs of star and galaxy formation.
“The first stars may well have come together at about 200 million years,” Illingworth said. “James Webb should take us back into a very important timeframe, when galaxies were really coming together.”
Launch Date Uncertainty
Though its promise is huge, researchers will have to wait a few years to put the telescope to use.
JWST, long afflicted by budget overruns and delays, still has no estimated launch date, officials said in January at the American Astronomical Society’s winter meeting in Seattle.
Last November, an independent review panel concluded that the telescope, once slated for launch in June 2014, could lift off no sooner than September 2015. But at a town hall-style talk in January, a NASA official stressed that that window is not binding.
“There are a lot of steps that have to happen before the agency commits to a launch date,” said Eric Smith, JWST program scientist at NASA headquarters in Washington. “There is no such thing as a launch date for JWST. We’re working on it.”
The JWST mission, led by NASA’s Goddard Space Flight Center in Greenbelt, Md., is billed as Hubble’s successor. The telescope has huge light-collecting power: Its primary mirror is 6.5 meters wide, or more than twice as big as Hubble’s.
While orbiting about 1.6 million kilometers from Earth, JWST will scan the universe in infrared light, helping astronomers study the early days of the universe, the formation of alien star systems and much more, NASA officials have said. Unlike the Hubble Space Telescope, JWST will not observe the universe in the visible light range of the light spectrum.
NASA had estimated that JWST would launch in June 2014 and cost about $5 billion over its lifetime. But delays and cost overruns have long afflicted the spacecraft, which currently consumes 40 percent of NASA’s astrophysics budget.
The independent review panel, convened at the request of U.S. Sen. Barbara Mikulski (D-Md.) to look into the cause of JWST’s problems, concluded in November that the telescope would cost about $6.5 billion, and that it could launch no earlier than September 2015.
The panel found no fault with the telescope’s scientific progress, instead citing longstanding budgeting and management issues. Indeed, JWST continues to move forward with its assembly and testing, officials said.
Five of the telescope’s 18 gold-coated flight mirrors are completely finished and tested, for example, and the other 13 should be done by the end of this summer, according to Mark Clampin, JWST observatory project scientist at Goddard.
“The bottom line is, we made really good progress in 2010,” Clampin said.
The review panel, led by John Casani of NASA’s Jet Propulsion Laboratory in Pasadena, Calif., made a number of recommendations to help get JWST back on track, and NASA is already incorporating many of them, Smith said.
For example, the agency has reorganized the program’s management structure, elevating it to a new organizational entity at NASA headquarters.
“We now have the direct attention of the NASA administrator for this program,” Smith said.
Officials also are coming up with a new baseline cost for the JWST project, one that will be accurate with an 80 percent confidence level — another panel recommendation.
Smith stressed that JWST officials know the program is being scrutinized more closely now, and that the new Congress — composed more heavily of Republicans, many of whom have pledged to cut federal spending — will likely be unforgiving of further budget problems.
“We know that, when we rebaseline this program, we’ve got to get it right,” Smith said.
The new estimates of project costs and schedules also will be evaluated by at least two independent organizations, Smith added.
But much remains to be done before NASA can commit to a launch date, Smith said. For one thing, NASA and other federal entities — such as the White House Office of Science and Technology Policy, and the Office of Management and Budget — will have to agree that the new JWST plan is satisfactory.
After that happens, the project will undergo a formal NASA review, Smith said. Another variable is the uncertainty surrounding funding, since Congress has yet to enact a budget for the remainder of 2011 and President Barack Obama’s 2012 budget request will not be released until the week of Feb. 14.
In light of all that needs to be done, and all of the uncertainty, JWST officials do not think it would be wise to commit to a launch date or to make any predictions.
“A lot of people get themselves in hot water by giving a quick and dirty answer,” Smith said. “We recognize that if we give you a quick answer, it’ll probably be a bad answer.”