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STS-76: In review

The STS-76 astronauts narrate highlights from the 1996 mission that launched Shannon Lucid to the Russian space station Mir.

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STS-75: In review

The STS-75 astronauts narrate highlights from the 1996 mission that saw the tethered satellite suddenly break free from the shuttle.

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STS-72: In review

The STS-72 astronauts narrate highlights from the 1996 mission that retrieved a Japanese satellite.

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STS-122: In review

The STS-122 crew narrates highlights from its mission that delivered Europe's Columbus module to the space station.

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STS-100: In review

The STS-100 astronauts narrate highlights from the April 2001 mission that installed the space station's Canadian robot arm.

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STS-102: In review

The STS-102 astronauts narrate highlights from the March 2001 mission that conducted the first ISS resident crew exchange.

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STS-123 landing

Shuttle Endeavour returned from space with a night landing March 26 at Kennedy Space Center.

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Solar flares set the Sun quaking, satellite shows
EUROPEAN SPACE AGENCY NEWS RELEASE
Posted: April 18, 2008

Data from the ESA/NASA spacecraft SOHO shows clearly that powerful starquakes ripple around the Sun in the wake of mighty solar flares that explode above its surface. The observations give solar physicists new insight into a long-running solar mystery and may even provide a way of studying other stars.

The outermost quarter of the Sun's interior is a constantly churning maelstrom of hot gas. Turbulence in this region causes ripples that criss-cross the solar surface, making it heave up and down in a patchwork pattern of peaks and troughs.

The joint ESA-NASA Solar and Heliospheric Observatory (SOHO) has proved to be an exceptional spacecraft for studying this phenomenon. Discovering how the ripples move around the Sun has provided valuable information about the Sun's interior conditions. A class of oscillations called the 5-minute oscillations with a frequency of around 3 millihertz have proven particularly useful.

According to conventional thinking, the 5-minute oscillations can be thought of as the sound you would get from a bell sitting in the middle of the desert and constantly being touched by random sand grains, blown on the wind. But what Christoffer Karoff and Hans Kjeldsen, both at the University of Aarhus, Denmark, saw in the data, was very different.  

"The signal we saw was like someone occasionally walking up to the bell and striking it, which told us that there was something missing from our understanding of how the Sun works," Karoff says.

So they began looking for the culprit and discovered an unexpected correlation with solar flares. It seemed that when the number of solar flares went up, so did the strength of the 5-minute oscillations.

"The strength of the correlation was so strong that there can be no doubt about it," says Karoff.

A similar phenomenon is known on Earth in the aftermath of large earthquakes. For example, after the 2004 Sumatra-Andaman Earthquake, the whole Earth rang with seismic waves like a vibrating bell for several weeks.

The correlation is not the end of the story. Now the researchers have to work to understand the mechanism by which the flares cause the oscillations. "We are not completely sure how the solar flares excite the global oscillations," says Karoff.

In a broader context, the correlation suggests that, by looking for similar oscillations within other stars, astronomers can monitor them for flares. Already, Karoff has used high-technology instruments at major ground-based telescopes to look at other Sun-like stars. In several cases, he detected the tell-tale signs of oscillations that might originate from flares.

"Now we need to monitor these stars for hundreds of days," he says. That will require dedicated spacecraft, such as the CNES mission with ESA participation, COROT. The hard work, it seems, is just starting.

John Glenn Mission Patch

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The historic first orbital flight by an American is marked by this commemorative patch for John Glenn and Friendship 7.
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Final Shuttle Mission Patch

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The crew emblem for the final space shuttle mission is available in our store. Get this piece of history!
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Celebrate the shuttle program

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This special commemorative patch marks the retirement of NASA's Space Shuttle Program. Available in our store!
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Anniversary Shuttle Patch

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This embroidered patch commemorates the 30th anniversary of the Space Shuttle Program. The design features the space shuttle Columbia's historic maiden flight of April 12, 1981.
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Mercury anniversary

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Celebrate the 50th anniversary of Alan Shephard's historic Mercury mission with this collectors' item, the official commemorative embroidered patch.
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Fallen Heroes Patch Collection
The official patches from Apollo 1, the shuttle Challenger and Columbia crews are available in the store.
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