How is the James Webb Space Telescope different than the Hubble Space Telescope? What will JWST be looking for when it begins operating? In this short video, NASA astrophysicist Dr. Amber Straughn answers questions, and offers facts and images to explain what the Webb Space Telescope will tell us about the cosmos.
JWST Sunscreen Offers SPF 1,000,000
The James Webb Space Telescope will have a sunshield that is about the size of a tennis court, and mission managers say it will offer the best “SPF” (Sun Protection Factor) in the Universe.
“Each of the five layers of the shield is less than half the thickness of a piece of paper,” said John Durning, Deputy Project Manager for JWST. “The five work together to create an effective SPF of 1,000,000.”
This sunshield protects the observatory from unwanted light, keeping it cool and allowing it to detect heat from faraway objects in the universe. So, how do you get something that large into orbit?
Continue reading “JWST Sunscreen Offers SPF 1,000,000”
JWST Built with ‘Unobtainium’
[/caption]
The James Webb Space Telescope (JWST) is the much anticipated, long awaited “next generation” telescope, which we hope will look further back in time, and deeper within dusty star forming regions, using longer wavelengths and more sensitivity than any previous space telescope. In order to take us to this next level, you’d kinda figure that new technologies would have to be developed in order for this ground-breaking, super-huge telescope to be built. You’d be right.
In fact, engineers had to use a little unobtainium to build the one-of-a-kind chassis, the backbone that will hold the spacecraft together.
Unobtainium isn’t just the name of the material mined in James Cameron’s movie “Avatar.” It is a word used in engineering — and sometimes fiction – to describe any extremely rare, costly, or physically impossible material or device needed to fulfill a given design for a given application.
The chassis for JWST – called the the Integrated Science Instrument Module ISIM – is made of a never-before-manufactured composite material which had to withstand the super-cold temperatures it will encounter when the observatory reaches its orbit 1.5-million kilometers (930,000 miles) from Earth.
The ISIM just passed an extremely important test, surviving temperatures that plunged as low as 27 Kelvin (-411 degrees Fahrenheit), colder than the surface of Pluto during a cycle of testing in Goddard’s Space Environment Simulator — a three-story thermal-vacuum chamber that simulates the temperature and vacuum conditions found in space.
The team at Goddard Space Flight Center who were charged with building the chassis needed a material that would assure the various instruments on JWST would maintain a precise cryogenic alignment and stability, yet survive the extreme gravitational forces experienced during launch.
The test was done to find out whether the car-sized structure contracted and distorted as predicted when it cooled from room temperature to the frigid — very important since the science instruments must maintain a specific location on the structure to receive light gathered by the telescope’s 6.5-meter (21.3-feet) primary mirror. If the structure shrunk or distorted in an unpredictable way due to the cold, the instruments no longer would be in position to gather data about everything from the first luminous glows following the Big Bang to the formation of star systems capable of supporting life.
When they first began, there was nothing out there that remotely fit the description of what was needed. So, that left one alternative: developing their own as-yet-to-be manufactured material, which team members jokingly referred to as “unobtainium.” Through mathematical modeling, the team discovered that by combining two composite materials, it could create a carbon fiber/cyanate-ester resin system that would be ideal for fabricating the structure’s square tubes that measure 75-mm (3-inch) in diameter.
During the recent 26-day test, and with repeated cycles of testing, the truss-like assembly designed by Goddard engineers did not crack. The structure shrunk as predicted by only 170 microns — the width of a needle —when it reached 27 Kelvin (-411 degrees Fahrenheit), far exceeding the design requirement of about 500 microns. “We certainly wouldn’t have been able to realign the instruments on orbit if the structure moved too much,” said ISIM Structure Project Manager Eric Johnson. “That’s why we needed to make sure we had designed the right structure.”
This type of structure could serve NASA in the future for the next-generation beyond JWST, and could also be a “spinoff” that manufacturers could find useful in designing structures that demand a high tolerance in conditions.
Source: NASA Goddard
Extrasolar Volcanoes May Soon be Detectable
[/caption]
We’ve all seen pictures of erupting terrestrial volcanoes from space, and even eruptions on Jupiter’s moon Io in the outer solar system, but would it be possible to detect an erupting volcano on an exoplanet? Astronomers say the answer is yes! (with a few caveats)
It’s going to be decades before telescopes will be able to resolve even the crudest surface features of rocky extrasolar planets, so don’t hold your breath for stunning photos of alien volcanoes outside our solar system. But astronomers have already been able to use spectroscopy to detect the composition of exoplanet atmospheres, and a group of theorists at the Harvard-Smithsonian Center for Astrophysics think a similar technique could detect the atmospheric signature of exo-eruptions.
By collecting spectra right before and right after the planet goes behind its star, astronomers can subtract out the star’s spectrum and isolate the signal from the planet’s atmosphere. Once this is done, they can look for evidence of molecules common in volcanic eruptions. Models suggest that sulfur dioxide is the best candidate for detection because volcanoes produce it in huge quantities and it lasts in a planet’s atmosphere for a long time.
Still, it won’t be easy.
“You would need something truly earthshaking, an eruption that dumped a lot of gases into the atmosphere,” said Smithsonian astronomer Lisa Kaltenegger. “Using the James Webb Space Telescope, we could spot an eruption 10 to 100 times the size of Pinatubo for the closest stars,” she added.
In 1991 Mount Pinatubo in the Philippines belched 17 million tons of sulfur dioxide into the stratosphere. Volcanic eruptions are ranked using the Volcanic Explosivity Index (VEI). Pinatubo ranked ‘colossal’ (VEI of 6) and the largest eruption in recorded history was the ‘super-colossal’ Tambora event in 1815. With a VEI of 7 it was about 10 times as large as Pinatubo. Even larger eruptions (more than 100 times larger than Pinatubo) on Earth are not unheard of: geologic evidence suggests that there have been 47 such eruptions in the past 36 million years, including the eruption of the Yellowstone caldera about 600,000 years ago.
The best candidates for detecting extrasolar volcanoes are super-earths orbiting nearby, dim stars, but the Kaltenegger and her colleagues found that volcanic gases on any earth-like planet up to 30 light years away might be detectable. Now they just have to wait until the James Webb Space Telescope is launched 2014 to test their prediction.