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Saturday, September 6, 2008

NASA to Explore "Secret Layer" of the Sun

Next April, for a grand total of 8 minutes, NASA astronomers are going to glimpse a secret layer of the sun.

Researchers call it "the transition region." It is a place in the sun's atmosphere, about 5000 km above the stellar surface, where magnetic fields overwhelm the pressure of matter and seize control of the sun's gases. It's where solar flares explode, where coronal mass ejections begin their journey to Earth, where the solar wind is mysteriously accelerated to a million mph.

It is, in short, the birthplace of space weather.

Researchers hope it is about to yield its secrets.

Right: Not far above the surface of the sun lies the "transition region" where magnetic fields seize control of solar gases. Photo credit: NASA/TRACE.

"Early next year, we're going to launch an experimental telescope that can measure vector magnetic fields in the transition region," explains Jonathan Cirtain of the Marshall Space Flight Center (MSFC). Previous studies have measured these fields above and below the transition region—but never inside it. "We hope to be the first."

The name of the telescope is SUMI, short for Solar Ultraviolet Magnetograph Investigation. It was developed by astronomers and engineers at the MSFC and is currently scheduled for launch from White Sands, New Mexico, in April 2009.

SUMI works by means of "Zeeman splitting." Dutch physicist Pieter Zeeman discovered the effect in the 19th century. When a glass tube filled with incandescent gas is dipped into a magnetic field, spectral lines emitted by the gas get split into two slightly different colors—the stronger the field, the bigger the splitting. The same thing happens on the sun. Here, for instance, are some spectral lines from gaseous iron being split by the magnetic field of a sunspot:

see caption

Above: Zeeman splitting of spectral lines from a strongly-magnetized sunspot. [more]

By measuring the gap, astronomers estimate the strength of the sunspot's magnetic field. Furthermore, by measuring the polarization of the split line, astronomers can figure out the direction of the magnetic field. Strength + direction = everything you ever wanted to know about a magnetic field!

This trick has been applied to thousands of sunspots on the solar surface, but never to the transition region just a short distance above.

Why not?

"Just bad luck, really," says Cirtain. "Gas in the transition region doesn't produce many strong spectral lines that we can see at visible wavelengths." It does, however, produce lines at UV wavelengths invisible from Earth's surface.

see caption"That's why we have to leave Earth."

SUMI will blast off inside the nose cone of a Black Brant rocket on a sub-orbital flight that takes it to an altitude of 300 km. "We'll be above more than 99.99% of Earth's atmosphere," says Cirtain. About 68 seconds into the flight, payload doors will open, affording SUMI a crystal-clear view of the UV sun. "From that moment, we've only got 8 minutes to work with. We'll target an active region and start taking data."

Right: A Black Brant sounding rocket of the type that will carry SUMI above Earth's atmosphere.

SUMI's "vector magnetograph" is tuned to study a pair of spectral lines: one from triply-ionized carbon (CIV) at 155 nanometers and a second from singly-ionized magnesium (MgII) at 280 nanometers. "There's nothing special about those ions," notes Cirtain. "They just happen to produce the best and brightest lines at temperatures and densities typical of the transition region."

Cirtain anticipates how it will feel to have his precious instrument hurtling 300 km above Earth at 5,000 mph: "Eight minutes of terror." He'll start breathing again when the payload doors close and SUMI begins its descent back to Earth. Cirtain ticks off the stages: "Reentry into the atmosphere. Open parachutes. Landing back at White Sands. Recovery."

The short flight probably won't lead to immediate breakthroughs. "But it will demonstrate the SUMI concept and show us if it's going to work." A successful flight would lead to more flights and eventually to a SUMI-style magnetograph permanently installed on a space telescope.

"That's the dream," he says. Transition region, prepare to yield...

Closest Look Yet at Milky Way's Black Hole

If it looks like a black hole, and acts like a black hole, it's probably a black hole.

For a while now scientists have thought a dense, massive object lurking at the center of our galaxy is likely a giant black hole, but they haven't been able to prove it. New observations offering the closest view yet of the heart of the Milky Way present strong evidence for the black hole theory, and even hope of finally settling the question soon.

By linking a series of radio telescopes around the world, astronomers created a virtual telescope with the resolving power of a single dish the size of the distance between the various sites (about 2,800 miles, or 4,500 kilometers). This instrument grabbed an intimate image that probed nearly to the Milky Way's black hole's event horizon — the point beyond which nothing, including light, could ever escape.

Blessing and a curse

Since our own galaxy's apparent supermassive black hole is the closest of its kind to us, it offers a unique chance to study how these objects behave and affect galaxies.

"This is the best black hole candidate that we have anywhere in the universe, the best chance we have to observe the kind of signatures we would expect around the immediate vicinity of a black hole," said study leader Sheperd Doeleman of MIT. "One of the problems with looking at this particular source is that we have to look through our galaxy. It's a blessing that it's this close, but it's a curse because it's obscured by gas and dust."

In order to bypass the Milky Way's shroud of gas and dust, the researchers looked at 1.3 mm radio light, which escapes the fog better than longer-wavelength light. They combined observations taken from observatories in Hawaii, Arizona and California in a technique called Very Long Baseline Interferometry (VLBI) to observe the galactic center with some of the highest resolution ever achieved in astronomy —the equivalent of a baseball seen on the surface of the moon, 240,000 miles away.

The researchers observed a bright source of light known as Sagittarius A* ("A-star"), thought to mark a black hole roughly 4 million times the mass of the sun. The mass is determined by looking at the effect of the colossal object on stars that orbit near to the galactic center. The team found that Sagittarius A* has a diameter equal to about one-third the distance between Earth and the sun, or about 30 million miles (50 million km). This small size indicates the mass in the galactic center is even denser than previous measurements found, which supports the idea that the object hidden there must be a black hole, because current theories have no other reasonable explanation for describing so much mass packed into such a small space.

Settling the question

Scientists can't pin down the process responsible for the bright radiation coming from Sagittarius A*, but suggest it could be a powerful jet of particles accelerated by magnetic fields around the black hole, or radiation pouring out of an accretion disk of matter funneling into the black hole.

The researchers hope they'll be able to get to the bottom of the question, and finally prove that Sagittarius A* is a supermassive black hole, through future observations made with the same technique.

"We've been working for over a decade now on the machinery and instrumentation to pull this off," Doeleman told SPACE.com. "The real beauty of this technique is that now we've shown it can be done. We'll get very good data in the next three to five years and I think some of those will tell us if we're seeing some of the signatures we'd expect from a black hole."

To improve on the images they've already made, the astronomers plan to add even more telescopes around the world, as well as more dishes at each individual site to boost the signal. They also plan to look in even smaller wavelength radio light.

"This pioneering paper demonstrates that such observations are feasible," said Harvard astrophysicist Avi Loeb, who did not work on the study. "It also opens up a new window for probing the structure of space and time near a black hole and testing Einstein's theory of gravity."

The study, funded by the National Science Foundation and conducted at the Arizona Radio Observatory's Submillimeter Telescope (ARO-SMT) of the University of Arizona, the Combined Array for Research in Millimeter-wave Astronomy (CARMA) in California, and the James Clerk Maxwell Telescope (JCMT) and the Submillimeter Array (SMA) in Hawaii, is detailed in the Sept. 4 issue of the journal Nature.

Apples and pears at risk due to dramatic decline in the honeybee, experts warn

British apples and pears are under threat because of a dramatic decline in honeybee numbers, experts have warned.

The bee population in Britain has fallen by a third over the past year alone due to bad weather, insecticides and soaring numbers of parasitic mites.

As a result, the honey supply is expected to run dry within three months and stocks of fruit and vegetables pollinated by bees will also be devastated.

Tim Lovett, president of the British Beekeeping Association, said the decline in the bee population looked likely to continue and urged the Government to fund more research into the problem.

Fewer bees would lead to a fall in supply of strawberries and broad beans

Fewer bees would lead to a fall in supply of strawberries and broad beans

He warned that since most of our pear and apple productivity relied on pollination from bees, future supplies were endangered.

Mr Lovett said that without bees to pollinate crops, supplies of oil seed rape, strawberries and broad beans could decrease by around 10 per cent, blackcurrants by 20 per cent, raspberries by 30 per cent, runner beans by 40 per cent and apples and pears by up to 90 per cent.

He added: 'If we lose our bees we lose our honey - that we see straight away. But then what we see is a general decline in production of pollinated fruits. We will begin to reap that whirlwind next year.'

New Concentrated Solar Tech: Simple, Cheap and Efficient

sun

Morgan Solar, a Toronto-based company launched last summer, believes it has the answer to creating simple and cheap solar concentrators.

While other companies are working to make solar cheaper by using mirrors or lenses to magnify sunlight that is directed into solar cells, Morgan Solar takes a different approach. Their system uses a thin sheet of acrylic to concentrate sunlight 750 times. The sunlight is directed to a tiny cell on the edge of the plastic, greatly reducing the amount of material needed.

Though Morgan Solar has competitors in the concentrated solar field, the company claims that their design is more efficient and less likely to break than other systems. And since their product requires so few materials—just aluminum, acrylic, and PV—it will be four times cheaper than other concentrated solar technologies.

Of course, Morgan Solar’s design is sure to draw comparisons to MIT’s announcement in July of a new technology that uses organic dyes to concentrate solar. But Morgan Solar claims that their optics are even more efficient.

We’ll find out whether the companies impressive claims are true in short order— a 1 meter by 1 meter prototype panel is currently being installed at the Earth Rangers Center in Toronto. The panel will begin producing electricity at the end of the month.

If Morgan Solar’s panels work as planned, concentrated solar may become a viable technology for countries that can’t afford the expensive systems available today.