Tuesday, October 23, 2007

Old Galaxy Finds Fountain of Youth


In a galaxy far, far away, a theft of cosmic proportions is taking place in an effort to claim the fountain of youth.

A massive galaxy is stealing a billion suns worth of gas from a smaller galactic neighbor. In space, gas is a hot commodity. Really hot. In this case, about 1,340 degrees Fahrenheit (730 degrees Celsius). And it's great for making new stars.

"We may be viewing the larger galaxy in a rare, brief stage of its reincarnation from an old galaxy to a youthful one studded with brilliant stars," said Patrick Ogle of NASA's Spitzer Science Center at the California Institute of Technology.

The robber, called 3C 326 North, is about the mass of our Milky Way galaxy, and its victim, 3C 326 South, is about half its mass. They are close enough to perturb each other gravitationally and might eventually collide. Such galaxy mergers are common in the universe: Gas and stars in two nearby galaxies become tangled until they become one larger galaxy. The case of 3C 326 is the clearest example yet of large quantities of gas being heated and siphoned from one galaxy to another.

"This could be an important phase in galaxy mergers that we are just now witnessing," Ogle said.

The scene was imaged by NASA's Spitzer Space Telescope and are reported in the Oct. 20 issue of the Astrophysical Journal.

The scene of the crime is about a billion light-years away. So in reality, the theft took place a billion years ago, but the light revealing it has only just arrived.

Successful Ariane 5 Upper Stage Engine Re-Ignition Experiment


A successful re-ignition of the Ariane 5 upper stage engine performed during the most recent mission has consolidated Ariane 5's readiness for the launch of the Jules Verne Automated Transfer Vehicle. The launch of ESA's Automated Transfer Vehicle (ATV), which carries supplies to the International Space Station, will require multiple firings of the Ariane 5 ES upper stage engine. In this context, hundreds of re-ignition tests under various thermal conditions have been undertaken at the DLR Test Centre in Lampoldshausen to qualify the Aestus engine for several re-ignitions.

In order to consolidate this on ground qualification a re-ignition experiment was performed during the last Ariane-5 launch - on the evening of 5 October - when an Ariane 5 GS launcher lifted off from Europe's Spaceport in French Guiana carrying two commercial telecommunications satellites into geostationary transfer orbit.

Once the commercial payloads were safely on their way, a successful experimental re-ignition of the Aestus engine took place - 54 minutes after the release of the second payload. The experiment was done to validate operational conditions (mainly temperatures and pressures) and procedures (propellant settling in tanks) of the launcher upper stage, which will be applied during the ATV orbital injection mission. It also verified the behaviour of the composite during the re-ignition phase.

Analysis of the many temperature and pressure parameters is ongoing and confirms a nominal behaviour very close to expectations. "We are extremely satisfied with the results of the Aestus re-ignition experiment, which confirms the on ground qualification of the re-ignition capability and adds to our confidence of mission success for the launch of ATV Jules Verne in the early part of next year" said ESA's Ariane Programme Manager, Toni Tolker-Nielsen.

Launch to geostationary transfer orbit
A communications satellite launch requires the engine on the Ariane 5 upper stage to fire only once. A few seconds after the Ariane 5 main stage separates, the upper stage engine ignites to continue propelling the upper stage and payloads towards geostationary transfer orbit. The engine is shut down once the correct orbit for the injection of the payloads into their transfer orbits has been reached.

The standard geostationary transfer orbits for communications satellites are elliptical, with a perigee of 250 km and an apogee of 36 000 km. Once injected into this transfer orbit, the satellites use an apogee boost motor to raise the orbit perigee to 36 000 km by firing the motor when the satellites are at the apogee of the transfer orbit. This staged approach is the optimum from an energetic point of view and allows the placing of the highest mass into a circular geostationary orbit at an altitude of 36 000 km.

Automated Transfer Vehicle launch
Launching the ATV will be more complex because the target orbit is circular, rather than elliptical.

After main stage separation over the Atlantic Ocean, the Aestus engine of the upper stage will perform a first boost lasting 8 minutes to reach an elliptical orbit (136 km x 260 km). Then, after a coasting phase to the apogee of the elliptical orbit lasting 48 minutes, a second boost with a duration of 30 seconds serves to reach the ATV circular injection orbit at an altitude of 260 km.

This second firing of the Aestus engine will take place over southeast Australia, just over an hour into the flight. Four minutes later, the ATV will separate over the Pacific, ready to fly to the International Space Station using its own navigation and propulsion systems.

One orbit later, now over Western Australia, the Aestus engine will re-ignite briefly, for a third time, causing the launcher's upper stage to de-orbit safely and burn up during a precise destructive re-entry over of the South Pacific Ocean.

China plans to launch first moon orbiter on Wednesday


China, which plans one day to send a human to the moon, said it expected to launch its first lunar orbiter on Wednesday, state media reported, quoting the country's space agency.

The launch of the Chang'e I rocket and orbiter will likely take place on Wednesday at 6:00 pm (1000 GMT) from the Xichang Satellite Launch Centre in southwestern Sichuan province, the official Xinhua news agency reported.

The launch of the moon orbiter is part of a three-step lunar exploration programme China hopes will eventually see moon samples brought back to Earth.

The probe will be followed by robotic missions and, eventually, a lunar base to allow astronauts to live longer on the moon and utilise its resources.

China successfully launched astronaut Yang Liwei into orbit in 2003, becoming the third country after the former Soviet Union and the United States to put a man in space.

China has offered 2,000 tickets to the public to view the launch.