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Astronaut Hall of Fame

Veteran space shuttle fliers Mike Coats, Steve Hawley and Jeff Hoffman are inducted into the Astronaut Hall of Fame at Kennedy Space Center during this ceremony held May 5.

 Part 1 | Part 2

Traveling on Freedom 7

Fly with Alan Shepard during his historic journey into space with this documentary that takes the viewer along as an invisible companion to America's first astronaut.

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Encounter with Jupiter

The Pluto-bound New Horizons spacecraft recently flew past the Jovian system for a gravity sling-shot toward the outer solar system. New images of Jupiter and its moons are revealed in this briefing.

 Presentation | Q&A

"The Time of Apollo"

This stirring 1970s documentary narrated by Burgess Meredith pays tribute to the grand accomplishments of Apollo as men left Earth to explore the Moon and fulfill President Kennedy's challenge to the nation.

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1958: America in space

This is a video report on the United States' space exploration efforts during 1958. These historic pioneering days included the launch of Explorer 1, the first American satellite to orbit Earth.

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The Flight of Faith 7

The final and longest manned flight of Project Mercury was carried out by astronaut Gordon Cooper in May 1963. This film shows the voyage of Faith 7.

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Pegasus launches AIM

An air-launched Pegasus rocket lofts NASA's AIM satellite into orbit to study mysterious clouds at the edge of space.

 Full coverage

The Sun in 3-D

NASA's twin STEREO spacecraft have made the first three-dimensional images of the Sun. Scientists unveil the images in this news conference held April 23.

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Has SOHO ended a 30-year quest for solar ripples?
EUROPEAN SPACE AGENCY NEWS RELEASE
Posted: May 6, 2007

The ESA-NASA Solar and Heliospheric Observatory (SOHO) may have glimpsed long-sought oscillations on the Sun's surface. The data will reveal details about the core of our star and it contains clues on how the Sun formed.

 
An artist's impression of SOHO. Credit: SMM (IAC)
 
The subtle variations reveal themselves as a miniscule ripple in the overall movement of the solar surface. Astronomers have been searching for ripples of this kind since the 1970s, when they first detected that the solar surface was oscillating in and out.

The so-called 'g-modes' are driven by gravity and provide information about the deep interior of the Sun. They are thought to occur when gas churning below the solar surface plunges even deeper into our star and collides with denser material, sending ripples propagating through the Sun's interior and up to the surface. It is the equivalent of dropping a stone in a pond.

Unfortunately for observers, these waves are badly degraded during their passage to the solar surface. By the time g-modes reach the exterior, they are little more than ripples a few metres high.

To make matters more difficult, the g-modes take between two and seven hours to oscillate just once. So, astronomers are faced with having to detect a swell on the surface that rises a metre or two over several hours.

Now, however, astronomers using the Global Oscillation at Low Frequency (GOLF) instrument on SOHO think they may have caught glimpses of this behaviour. Instead of looking for an individual oscillation, they looked for the signature of the cumulative effect of a large number of these oscillations.

As an analogy, imagine that the Sun was an enormous piano playing all the notes simultaneously. Instead of looking for a particular note (middle C for instance) it would be easier to search for all the 'C's, from all the octaves together.

In the piano their frequencies are related to each other just as on the Sun, one class of g modes are separated by about 24 minutes.

"So that's what we looked for, the cumulative effect of several g modes," says Rafael A. Garcia, DSM/DAPNIA/Service d'Astrophysique, France. They combined ten years of data from GOLF and then searched for any hint of the signal at 24 minutes. They found it.

"We must be cautious but if this detection is confirmed, it will open a brand new way to study the Sun's core," says Garcia.

Until now, the rotation rate of the solar core was uncertain. If the GOLF detection is confirmed, it will show that the solar core is definitely rotating faster than the surface.

The rotation speed of the solar core is an important constraint for investigating how the entire Solar System formed, because it represents the hub of rotation for the interstellar cloud that eventually formed the Sun and all the bodies around it.

The next step for the team is to refine the data to increase their confidence in the detection. To do this, they plan to incorporate data from other instruments, both on SOHO and at ground-based observatories.

"By combining data from space (VIRGO and MDI, on SOHO) and ground (GONG and BiSON) instruments, we hope to improve this detection and open up a new branch of solar science," says Garcia.