Archive for October, 2011

WSF Live Forum: Fabric of the Cosmos

Friday, October 28th, 2011

Source -World Science Festival.

Join a live conversation with Brian Greene, exploring how scientists are piecing together the most complete picture yet of space, time, and the Universe.

Held at at Columbia University’s Miller Theatre, the event begins at 9 PM with the premiere broadcast of the first episode of NOVA’s The Fabric of the Cosmos, followed immediately by a live Q&A hosted by Greene, with special guests including renowned theoretical physicist Leonard Susskind and Saul Perlmutter, winner of the 2011 Nobel Prize in Physics.

The Q&A will also be streamed live as an interactive webcast at 10PM ET/9PM CT at www.worldsciencefestival.com:

•Get the conversation going now and ask your questions via Twitter (using hashtag #WSFforum), or submit questions on the World Science Festival Facebook wall

•Tune in to the live webcast at worldsciencefestival.com on Nov. 2 at 10pm ET and submit your questions live during the webcast »

PBS / NOVA: The Fabric of the Cosmos

Friday, October 28th, 2011

Source -PBS / NOVA.

The Fabric of the Cosmos
Acclaimed physicist Brian Greene reveals a mind-boggling reality beneath the surface of our everyday world. Airing 11/2, 11/9, 11/16 and 11/23, at 9pm on PBS

Program Description
“The Fabric of the Cosmos,” a four-hour series based on the book by renowned physicist and author Brian Greene, takes us to the frontiers of physics to see how scientists are piecing together the most complete picture yet of space, time, and the universe. With each step, audiences will discover that just beneath the surface of our everyday experience lies a world we’d hardly recognize—a startling world far stranger and more wondrous than anyone expected.

Brian Greene is going to let you in on a secret: We’ve all been deceived. Our perceptions of time and space have led us astray. Much of what we thought we knew about our universe—that the past has already happened and the future is yet to be, that space is just an empty void, that our universe is the only universe that exists—just might be wrong.

Interweaving provocative theories, experiments, and stories with crystal-clear explanations and imaginative metaphors like those that defined the groundbreaking and highly acclaimed series “The Elegant Universe,” “The Fabric of the Cosmos” aims to be the most compelling, visual, and comprehensive picture of modern physics ever seen on television.

Falling German satellite ROSAT X-ray astronomy observatory

Friday, October 21st, 2011

Source -Spaceflight Now.

Less than a month after NASA’s falling UARS satellite grabbed the headlines, the German space agency says one of its abandoned satellites will dive back to Earth later this month, but no one knows where it will land.

The ROSAT X-ray astronomy observatory is smaller and less massive than NASA’s Upper Atmospheric Research Satellite, or UARS, which fell back to Earth on Sept. 24. But officials predict it will spread three times more debris and pose a greater threat to people than UARS.

That’s because ROSAT is made of heat-resistant components, especially its primary mirror, which officials say will probably be the largest single fragment that will reach Earth.

The satellite will streak into the atmosphere at 17,000 mph, and temperatures up to 3,000 degrees Fahrenheit will burn up much of the spacecraft.

“All these forces exerted on the satellite cause it to disintegrate, which in turn means that it eventually lands in the form of a long debris trail,” said Heiner Klinkrad, head of the European Space Agency’s space debris office. “The lightweight objects fall to Earth first, similar to leaves from a tree. The really heavy objects land later, because they ultimately have to drill their way through the atmosphere.”

But engineers expect the bulk of ROSAT to survive re-entry, littering its impact point with up to 30 pieces of debris.

The 5,348-pound satellite launched from Florida on a Delta 2 rocket in 1990. ROSAT does not have an engine or propulsion system because it used reaction wheels to point its telescope toward scientific targets in the cosmos.

Up to 3,750 pounds of the satellite could reach Earth’s surface. NASA said they expected 1,200 pounds of UARS to survive re-entry.

There is a 1-in-2,000 chance someone will be struck by fragments of ROSAT on its way down, according to Germany. That equates to odds of about 1-in-14 trillion that any individual person will be hit.

The threat from UARS wasn’t as high. An analysis from NASA showed there was a 1-in-3,200 chance of a collision between a human and a piece of UARS.

The remnants of UARS fell in the remote Pacific Ocean, and ROSAT will likely also end up in the sea, but its impossible to tell where it will crash until hours before.

ROSAT launched in June 1990 on a Delta 2 rocket.

ROSAT, which stands for Roentgen Satellite, was turned off in 1999, and its altitude has gradually dropped since then from an operational orbit more than 350 miles high. The German Aerospace Center, also known as DLR by its German acronym, says the spacecraft should re-enter the atmosphere between Oct. 20 and Oct. 25.

But the margin of error in the re-entry forecast is three days, and officials likely won’t know where the satellite will come down until after it falls. Even one day before re-entry, the time of ROSAT’s demise will only be known with a precision of plus-or-minus five hours, putting entire oceans and continents in the satellite’s flight path.

“All areas under the orbit of ROSAT, which extends to 53 degrees northern and southern latitude could be affected by its re-entry,” said a posting on DLR’s website. “The bulk of the debris will impact near the ground track of the satellite.”

“It will not be possible to make any kind of reliable forecast about where the satellite will actually come down until about one or two hours before the fact,” Klinkrad said. “It will, however, be possible to predict, about one day in advance, which geographical regions will definitely not be affected.”

ROSAT’s orbit was at an average altitude of 149 miles Wednesday.

“This slow descent is due to the friction encountered by the satellite as it enters the outer fringes of Earth atmosphere, which increases the more ROSAT penetrates into our atmosphere,” Klinkrad said.

Klinkrad said the major factor affecting a satellite’s fall from orbit is solar activity. Energy unleashed from the sun causes Earth’s atmosphere to heat up and expand, generating more drag for satellites in low orbits.

Fluctuations in solar activity can quicken or slow a satellite’s re-entry. Experts initially expected ROSAT’s plunge to occur last year, but solar activity turned out to be less than predicted, delaying the re-entry until this month.

Weekend Meteor Shower Oct. 20, 2011:

Friday, October 21st, 2011

Source – NASA Science News:

A map of the morning sky on Saturday, Oct. 22nd at 5:30 a.m. local time, viewed facing southeast.
A map of the morning sky on Saturday, Oct. 22nd at 5:30 a.m. local time, viewed facing southeast.

Weekend Meteor Shower Oct. 20, 2011: Earth is about to pass through a stream of debris from Halley’s comet, source of the annual Orionid meteor shower. Forecasters expect more than 15 meteors per hour to fly across the sky on Saturday morning, Oct. 22nd, when the shower peaks.

Orionids are most easily seen during the dark hours before sunrise. Twilight Orionids, however, are the most beautiful of all. “Although this isn’t the biggest meteor shower of the year, it’s definitely worth waking up for,” says Bill Cooke of the NASA Meteoroid Environment Office. “The setting is dynamite.”

Orionids are framed by some of the brightest and most beautiful constellations in the night sky. The meteors emerge from mighty Orion, the shower’s glittering namesake. From there they streak through Taurus the Bull, the twins of Gemini, Leo the Lion, and Canis Major–home to Sirius, the most brilliant star of all.

This year, the Moon and Mars are part of the show. They’ll form two vertices of a celestial triangle in the eastern sky on Saturday morning while the shower is most active; Regulus is the third vertex. Blue Regulus and red Mars are both approximately of 1st magnitude, so they are easy to see alongside the 35% crescent Moon. Many Orionids will be diving through the triangle in the hours before dawn.

Cooke’s team at the Meteoroid Environment Office will be watching for Orionids that actually hit the Moon.

Cometary debris streams like Halley’s are so wide, the whole Earth-Moon system fits inside. So when there is a meteor shower on Earth, there’s usually one on the Moon, too. Unlike Earth, however, the Moon has no atmosphere to intercept meteoroids. Pieces of debris fall all the way to the surface and explode where they hit. Flashes of light caused by thermal heating of lunar rocks and moondust are so bright, they can sometimes be seen through backyard-class telescopes.

“Since we began our monitoring program in 2005, our group has detected more than 250 lunar meteors,” says Cooke. “Some explode with energies exceeding hundreds of pounds of TNT.”

So far, they’ve seen 15 Orionids hitting the Moon–“two in 2007, four in 2008, and nine in 2009,” recalls Cooke. This year they hope to add to the haul. About 25% of the Moon’s dark terrain will be exposed to Halley’s debris stream, giving the team millions of square miles to scan for explosions.

Watching meteoroids hit the Moon is a good way to learn about the structure of comet debris streams and the energy of the particles therein. It also allows Cooke and colleagues to calculate risk factors for astronauts who, someday, will walk on the lunar surface again.

“Going outside to watch the Orionids might not be a good idea for a moonwalker,” says Cooke.

But it is a good idea for the rest of us. Set your alarm for a few hours before dawn on Saturday morning and enjoy the show.

Author: Dr. Tony Phillips | Credit: Science@NASA

The comet and the coronal mass ejection

Saturday, October 8th, 2011

Source – Phil Blatt at BadAstronomy.com:

NASA \ JPL What’s Up for October 2011?

Wednesday, October 5th, 2011

Source – NASA /JPL Solar System Exploration:

Look for moons and meteors this month!