Spaceflight Now Home

Spaceflight Now +

Premium video content for our Spaceflight Now Plus subscribers.

STS-41B: Human satellite
One of the iconic moments of the early space shuttle program was astronaut Bruce McCandless floating above the brilliantly blue Earth completely disconnected from his spacecraft. He was testing the Manned Maneuvering Unit, a jet-powered backpack that would enable spacewalkers to travel away from the space shuttle to service satellites. In this post-flight presentation, the crew of Challenger's STS-41B mission of February 1984 narrate the film highlights from their mission that also included the first shuttle landing at Kennedy Space Center.

 Small | Medium | Large

Shuttle launch delay
Space Shuttle Program Manager Wayne Hale announces his decision to replace suspect fuel-level sensors inside the liquid hydrogen portion of Discovery's external tank. The three-week job means Discovery will miss its May launch window, delaying the second post-Columbia test flight to the next daylight period opening July 1. Hale made the announcement during a news conference from Johnson Space Center on March 14.

 Dial-up video:
   Part 1 | Part 2

 Broadband video:
   Part 1 | Part 2

Stardust science
NASA's Stardust spacecraft returned to Earth in January with the first samples ever retrieved from a comet. This briefing with mission scientists held March 13 from the Johnson Space Center offers an update on the initial research into the comet bits.

 Dial-up video:
   Part 1 | Part 2

 Broadband video:
   Part 1 | Part 2

Exploring Enceladus
The Cassini spacecraft orbiting the planet Saturn has found evidence indicating pockets of liquid water may exist near the surface on the icy moon Enceladus, raising the question of whether the small world could support life. This movie includes stunning images of Enceladus taken by Cassini and animation of geysers seen erupting from the moon.

 Play video

MRO's orbit insertion explained
The make-or-break engine firing by the Mars Reconnaissance Orbiter to enter orbit around Mars and the subsequent aerobraking to reach the low-altitude perch for science observations are explained by project manager Jim Graf in this narrated animation package.

 Play video

Become a subscriber
More video

Chandra finds evidence for quasar ignition
Posted: March 23, 2006

New data from NASA's Chandra X-ray Observatory may provide clues to how quasars "turn on." Since the discovery of quasars over 40 years ago, astronomers have been trying to understand the conditions surrounding the birth of these immensely powerful objects.

An artist's illustration depicts a quasar in the center of a galaxy that has turned on and is expelling gas at high speeds in a galactic superwind. Clouds of hot, X-ray producing gas detected by Chandra around the quasars 4C37.43 (shown in the inset) and 3C249.1, provide strong evidence for such superwinds. Credit: Illustration: NASA/CXC/M.Weiss; X-ray inset: NASA/CXC/U.Hawaii/A.Stockton et al.
Hot, X-ray producing regions around two distant quasars observed by Chandra are thought to have formed during their activation. These features are located tens of thousands of light years from the central supermassive black holes thought to power the quasars.

"The X-ray features are likely shock waves that could be a direct result of the turning on of the quasar about 4 billion years ago," said Alan Stockton of the University of Hawaii in Honolulu, and lead author of a report on this work published recently in The Astrophysical Journal.

The quasars, 4C37.43 and 3C249.1, showed no evidence for the existence of a much larger envelope of hot gas around the features, nor were the observed X-ray regions associated with radio waves from the quasars. These factors rule out possible explanations or the X-ray emitting clouds, such as the cooling of hot intergalactic gas, or heating by high-energy jets from the quasars.

"The best explanation for our observations is that a burst of star formation, or the activation of the quasar itself, is driving an enormous amount of gas away from the quasar's host galaxy at extremely high speeds," said Hai Fu, a coauthor of the study who is also from the University of Hawaii.

Computer simulations of the formation of stars and the growth of black holes during a collision between two galaxies are consistent with this picture. The simulations, performed by Tiziana Di Matteo of Carnegie-Mellon University in Pittsburgh, Pennsylvania, and colleagues, show that the merger of galaxies drives gas toward the central regions where it triggers a burst of star formation and provides fuel for the growth of a central black hole.

The inflow of gas into the black hole releases a tremendous amount of energy, and a quasar is born. The power output of the quasar dwarfs that of the surrounding galaxy and expels gas from the galaxy in what has been termed a galactic superwind. The Chandra data provide the best evidence yet for a quasar-produced superwind.

Over a period of about 100 million years, the superwind will drive all the gas away from the central regions of the galaxy, quenching both star formation and further black hole growth. The quasar phase will end and the galaxy will settle down to a relatively quiet life. The tranquility of the galaxy will be interrupted from time to time as a small satellite galaxy is captured and provides food for the otherwise dormant supermassive black hole.

Other members of the research team were J. Patrick Henry, also of the University of Hawaii, and Gabriela Canalizo of the University of California, Riverside. NASA's Marshall Space Flight Center, Huntsville, Ala., manages the Chandra program for the agency's Science Mission Directorate. The Smithsonian Astrophysical Observatory provides science support and controls flight operations from the Chandra X-ray Center in Cambridge, Mass.



© 2014 Spaceflight Now Inc.