As reports Forbes in "Peering Back At The Universe's Past," space telescopes are really acting as time machines. They can watch objects which are so far from us that light has taken billions of years before reaching their mirrors. The Hubble telescope is able to look at events that took place 13.3 billion light-years ago. But the James E. Webb space telescope, currently under construction, and scheduled to be launched in 2011, will be able to see even further and catch phenomena which happened 13.5 billion light-years ago. The astronomers think the Webb telescope might even be able to see up to 13.7 billion light-years ago, when our universe was just 200 or 300 million years old. We are used to see fantastic images from Hubble, without paying too much attention to the characteristics of the telescope itself. So here is a thorough comparison between the two space telescopes.
Before starting this comparison, here are the opening paragraphs of the Forbes article.
Even the universe was young once. Someday soon, astronomers hope to snap a few of its baby pictures. The tool they'll use to do it is the James E. Webb Space Telescope, set to launch into space atop a European Space Agency rocket in 2011. Once it's up and running -- it is now being built by Northrup Grumman for NASA, the European Space Agency and the Canadian Space Agency--astronomers hope to peer back in time to when the universe was a toddler, a mere 200 million years after its birth in the "Big Bang" that took place 13.7 billion years ago.
Space telescopes act like time machines because the objects they look at are so far away that the light has taken billions of years just to get to the telescope, even though that light has been traveling at the speed of, well, light. And while scientists have a good understanding of what happened during the first 100 million years or so of the universe's life, there's a big blank spot in its timeline from that point to about a billion years after the Big Bang. Their hope is to see examples of the earliest stars and galaxies and study their evolution and the production of elements, which in turn leads to better understanding of the origins of life.
What are the hopes of the astronomers who will use the future telescope?
"We have lots of stories that say there should have been a first generation of stars," says John Mather, NASA's senior astrophysicist working on the Webb telescope. These primordial stars -- known as "population 3" stars, would have formed early in the history of the universe out of pure hydrogen and helium, burned for a short three million years or so and then exploded.
"We don't have any direct evidence that these stars existed, but we can see traces of them in the cosmic background radiation," Mather says. That background radiation is a form of electromagnetic radiation that is seen in every direction in the universe, and considered the best available evidence for the Big Bang theory, which holds that the universe came into being in an unbelievably massive explosion more than 13 billion years ago.
Please read the full article for more details and technical explanations.
Below is a table comparing the two space telescopes.
|Time to say Good Bye
|Position in Space
||375 miles above our heads
||1 million miles away from Earth|
|Costs to build
|Vision of our past
||13.3 billion light-years
||13.5 billion light-years|
||44 feet long, 14 feet in diameter
||Primary mirror will be about 20 feet in diameter, but will be protected by a sunshade as large as a tennis court|
|Weight on Earth
||24,000 pounds (almost 11 tons)
||13,400 pounds (only 6 tons)|
||This is a reflector with two mirrors, the main mirror having a diameter of about 2.4 meters
||Its primary mirror is a 6.5 meter beryllium reflector|
Besides answering questions about the nature and the origin of our known universe, these programs also have direct effect on our lives. Eric Smith, program scientist on the Webb telescope project, points out that the improvements of digital imaging already led to new ways to detect breast cancer.
The Forbes article ends with this.
No one yet knows what surprises the Webb telescope may yield.
And for your viewing pleasure, you can take a look at one of my preferred images captured by Hubble, as reported in this previous story, "Hubble Catches Some Cosmic Fireworks."
Sources: Arik Hesseldahl, Forbes, May 6, 2004; Wikipedia website