Tuesday, July 31, 2012
Mission control for the telescope is a small room on the University of California, Berkeley, campus, where about a dozen people with headsets rarely look up from their screens.
Fiona Harrison, a professor of physics and astronomy at the California Institute of Technology, is the principal scientist for the mission. If there's one word that describes her past few weeks, it's "nail-biting," she says.
The beginning of a space telescope's life is particularly stressful. It has to be switched on remotely, including the unfurling of a 33-foot arm that will act like a giant telephoto lens.
Now, the $170 million telescope is just about ready to begin its hunt for black holes.
"We're not actually seeing the black hole," Harrison says. "What you're actually seeing is the stuff that's attracted to it."
Harrison says they're called black holes because not even light can escape their gravity. But black holes aren't passive — they pull in tons of dust and gas. The material swirls around faster and faster, just like a bathtub drain, and gets hotter.
"The material is so hot that it radiates high-energy X-rays," she says, just like the ones doctors use. She says researchers observed them before, but it's like reading a book without your glasses.
"We know there's a story there, we know there's text, but we haven't been able to read the letters," she says.
With NuSTAR, they'll be able to see these X-rays at a higher resolution than ever before.
"It's incredibly exciting because we don't actually know what the text is going to say. And now we're going to be able to read it clearly for the first time," she says.
Harrison hopes the telescope will unlock some of the mysteries around black holes — like how they grow.
Eliot Quataert, an astronomy professor at UC Berkeley who is not on the mission staff, says black holes grow just like we do — by eating.
"They eat dramatically, but rarely," he says.
And at the very center of our galaxy, there's a super massive black hole that has eaten quite a bit. But we're still here.
"The misconception that's out there is that black holes are a vacuum cleaner that will inevitably suck in everything around them," Quataert says. For the most part, black holes are on a forced diet — they've already eaten everything close by.
"But then every once in a while, there will be a lot of gas that gets funneled to the center of a galaxy, and the black hole will grow in a big spurt," he says.
Quataert says seeing this black hole mealtime with the telescope could reveal more about the extreme physics behind it. That could answer questions about how galaxies form. UC Berkeley astronomer Joshua Bloom hopes NuSTAR will find another strange phenomenon: black hole burps.
"You can think about this black hole burping as if you're on a feeding frenzy and you can't fit that many hot dogs in your mouth," Bloom says.
Early last year, Bloom and other astronomers noticed a black hole devouring a star. The black hole spit out a huge jet of material — a burp. That might sound weird, since nothing can escape a black hole, right?
"These are sort of the Las Vegas of the universe. What happens in a black hole stays inside of a black hole. But on the outskirts of them, that is where there's tremendous action," he says.
Bloom says they're hoping to see more of these rare events and others that are still unknown to astronomers. The NuSTAR space telescope's mission is expected to last at least two years.
Tuesday, July 24, 2012
Tuesday, July 3, 2012
Tuesday, June 12, 2012
In an age when the size of the observable universe is known to a few decimal places, today's Transit of Venus offers a good opportunity to reflect on just how far we've come.
(For viewing information, click here.)
Less than 250 years ago, the brightest minds of the Enlightenment were stumped over how far the Earth is from the sun. The transits of the 1760s helped answer that question, providing a virtual yardstick for the universe.
Without an accurate distance between the sun and Earth — known as the Astronomical Unit — astronomers couldn't deduce the exact size of the solar system and had no way of knowing for sure how far away the stars were.
The Astronomical Unit has been "fundamental to figuring out the distances of everything in astronomy," says Michael Strauss, a professor of astrophysics at Princeton University.
Enter Edmond Halley of comet fame. In 1716, he alerted the scientific community to be ready for the 1761 and 1769 transits of Venus. He noted that if Venus was observed from multiple spots as it crossed the disc of the sun, you could use something called the parallax method and some trigonometry to get the much sought sun-Earth distance.
Although Halley, who died in 1742, was long gone by the transits of the 1760s, his historical timing was nonetheless impeccable. "This was the Age of Discovery, and people were finally able to start mounting big expeditions around the world for all kinds of reasons," Strauss says.
So an international effort was organized, with nations dispatching expeditions to far-flung places. Legendary English navigator and explorer Capt. James Cook was among them. He and his team sailed aboard the HMS Endeavour to newly discovered Tahiti in the South Pacific, where observations were set up ahead of the 1769 transit. (Observations in 1761 were largely failures.)
So how did the parallax method work?
"You observe the moment at which Venus touches the disc of the sun, what's called first contact," Strauss says. "What you're measuring is when Venus, the sun and the observer all appear to be in a straight line."
From different locations on Earth, that lining up occurs at slightly different times. It takes about seven hours for the total transit, so the difference between observations might be as much as a few minutes — easily measured by clocks of the day.
"You want to know exactly how long it takes, because that duration gives you a [base]line and that line you can then fit onto the sun," says Owen Gingerich, a professor emeritus of astronomy and the history of science at Harvard University.
The line forms the base of a triangle, and triangles make good yardsticks, says Gingerich, who spoke to NPR from California, where he is preparing to observe today's transit.
By knowing the exact distance between the two earthbound observers and comparing the differences in their observations, you can draw a pair of triangles that will give the distance from the Earth to Venus. Thanks to the work of mathematician Johannes Kepler, 18th century astronomers already knew Venus' orbit is about 70 percent that of Earth's. So if you know the distance between the Earth and Venus, you can easily figure out the value for the Astronomical Unit.
But it wasn't that simple. Because of something called the "black drop effect" having to do with density differences in the sun's outer layers, the observations were a little skewed. That threw the post-1769 figure for the Astronomical Unit off by a few percent from the correct answer. Still not bad, actually.
And how did the transit of Venus give us the distances to the stars?
The parallax method turns out to be good for figuring out how far they are, too. But since the stars are so much more distant than Venus, a much longer baseline was needed. Instead of two different geographic locations, the observations needed to be made during two different points in Earth's orbit, say one in June and another in December. Knowing the length of the Astronomical Unit (and therefore the size of the Earth's orbit) allowed scientists to know just how long the base of that massive triangle would be.
By Elizabeth Shogren | Monday, June 11, 2012
These voyages are years away, but on Monday, astronauts are heading underwater to take part in a simulation that will help them figure out how they might explore one possible new destination: a near-Earth asteroid.
It'll be the space agency's 16th NEEMO expedition — NASA Extreme Environment Mission Operations — commanded by astronaut Dottie Metcalf-Lindenburger. She flew on one of the last space shuttle missions, and even helped prepare Atlantis for its final launch.
"It was a very bittersweet time," says Metcalf-Lindenburger, who wants to go into space again. In the meantime, she's commanding a four-person crew that's putting on scuba gear instead of space suits. She says we all have to move on.
"Like in all things. I just had my daughter finish up her last day of preschool before she goes off to kindergarten. We have to shut chapters and begin new chapters and we had to do that in the space program, too," Metcalf-Lindenburger says.
Her crew will spend two weeks working underwater, which is the best approximation on this planet of what it would be like to operate in the zero gravity of an asteroid.
Their base will be an underwater lab called Aquarius. It's about the size of a school bus and sits 60 feet under the surface a few miles off the coast of Key Largo, Fla.
Metcalf-Lindenburger says floating underwater is a lot like floating in space.
"Water is a nice way to free your body and get to explore a different way of movement," she says. "Since we're so stuck with walking here on Earth, it's nice to float around, flip around — just like in space."
How To Hammer Rocks In Space
Cornell University astronomer Steve Squyres is heading to Aquarius for the second time. His last NEEMO mission was cut short because of a hurricane.
He's thrilled to get another chance to help figure out what kinds of equipment might help people do research on an asteroid someday. Last time, Squyres and his crewmates strapped jet packs to their backs and had a blast zooming through the water.
"They were great for moving around," he says. "You'd see a rock outcrop 30 meters away, and you'd go flying over to it."
But they learned jet packs were terrible if you needed to stay still for any length of time, like say, if you want to take a sample from an asteroid.
"If you just do something as simple as hit a rock with a hammer, you're going to go flying off into space, so we've got to develop a whole new set of tricks and tools for operating on the surface of an asteroid," Squyres says.
This time, they're going to see whether mini submarines might allow them to hover in place.
"Imagine this little submarine with a 6-foot-long beam sticking off the front of it, and an astronaut on the front of that like a hood ornament," Squyres says.
NASA hopes to start sending astronauts and equipment to asteroids after 2025.
What's So Interesting About Asteroids?
You might wonder why anyone would want to go to an asteroid, but Squyres says there are many reasons.
Some asteroids are made of stuff like metals, that some people think could be harvested. Squyres says we need to learn all we can about asteroids to understand more about the origin of the solar system and to protect ourselves.
"Asteroids are a threat. Asteroids have hit the Earth before, we know that," he says. "Asteroids have caused mass extinctions. A small asteroid hitting the Earth wiped out the dinosaurs 65 million years ago — unless we as a species know how to prevent it."
Just sending robots to asteroids isn't enough, he says. That means a lot coming from Squyres, considering he's a robot guy. He's the principal investigator for the Mars Rover project.
"What our state-of-the-art robot on Mars can do in a day, you can do in about 30 seconds," he says.
Metcalf-Lindenburger predicts that as soon as NASA figures out how to get people to an asteroid, people will want to go there.
"Humans are explorers by nature," she says. "We've been doing it for a very, very long time."
When NASA finally does sends people deeper into space, she says, she hopes to be among them.
Tuesday, April 24, 2012