Het Astronomie topic #1

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Op donderdag 19 januari 2006 21:01 schreef -CRASH- het volgende:

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THNX
Ze zegggen het
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zal ie ookwel altijd blij zijn
dat heel nederland de vlag uithangt
voor de jarige van vandaag.

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Op donderdag 19 januari 2006 21:28 schreef -CRASH- het volgende:

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er is er ook nog 1 van de oranjes jarig... Prinses Magriet
Dus dan wordt de vlag uit gehangen.


Psssst beetje oftopic bezig
Maar nu verder als astronomie topic

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Strange Setup: Andromeda's Satellite Galaxies All Lined Up



An unusually high number of galaxies are aligned along a single plane running through the center of the giant Andromeda galaxy. Scientists don’t have a theory to explain why.

Galactic cannibalism or dark matter may be responsible, researchers say.

The Andromeda galaxy is located at a distance of 2.5 million light-years away and is the nearest spiral galaxy to the Milky Way. Like our own galaxy, Andromeda is surrounded by numerous dwarf galaxy satellites. Many of these satellites are within 1.3 million light-years or less of the galaxy’s main disk.

Using the Hubble Space Telescope, Eva Grebel and Andrew Koch from the University of Basel in Switzerland found that nine out of Andromeda’s fourteen dwarf galaxy satellites reside in a single plane. The plane is about 52,000 light-years wide and is aligned perpendicular to Andromeda’s own galactic plane, within which the galaxy’s stars orbit about the center.

That nearly 80 percent of Andromeda’s satellite galaxy mass is located within a single plane is highly unusual and can’t be accounted for by traditional theories of galaxy formation, Grebel said.

The finding was announced recently at a meeting of the American Astronomical Society.

The Milky Way was found to contain two similar planes of satellite galaxies in the late 1980s, but with nothing to compare them to, astronomers couldn’t tell if such planes were a general property of galaxy formation or whether they were just a statistical fluke.

"One of the open questions was always ‘Do such planes of satellite galaxies exist around other galaxies?’" Grebel said. "If they do, it might indicate that it’s more than just chance."

The researchers aren’t sure what might be responsible for the strange alignment but they offered two possible scenarios.

Galactic Cannibalism

Perhaps long ago Andromeda swallowed a nearby orbiting galaxy but did a messy job of it; the galactic crumbs from that meal became Andromeda’s satellite dwarf galaxies. Such instances of galactic cannibalism are common and are believed to play a major role in galaxy formation.

"If this scenario were correct, we would expect these satellites to maintain the original orbit from the original galaxy form which they came," Grebel explained. Early results from computer models suggest that such a scenario is physically possible.

But it might be several years before this hypothesis can be confirmed, since accurate orbital measurements for Andromeda’s satellite galaxies are extremely difficult due to their distance, she added.

Dark matter stream

Another intriguing possibility is that the satellite galaxies are actually embedded in a stream of hypothetical dark matter flowing between two massive objects.

The plane containing Andromeda’s satellite galaxies points toward two such objects: M33, a spiral galaxy located 0.7 million light-years away from Andromeda and M81, a cluster of about 30 galaxies that is 11 million light-years away.

It could be that the satellite galaxies are gravitationally attracted to these streams of dark matter and clumping around them, giving the appearance of being aligned along a single, wide plane.

Grebel stressed that at this point, both of these scenarios are just speculation.

"We have no proof whether any of these is actually true," she said.

It may turn out that the alignment is due to chance after all or that another explanation entirely may be responsible.

Michael Turner, a cosmologist at the University of Chicago who was not involved in the study, found the results intriguing.

"It’s getting at this very simple question: how did our backyard get assembled?" Turner said.

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Op maandag 23 januari 2006 22:29 schreef -CRASH- het volgende:

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DAWN gaat niet door.....
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Falcon 1 Maiden Flight Update: Posted January 9, 2006

The new launch time is February 8 at 4:30 p.m. California time with Feb. 9 as a backup day.

Launch Viewing for Media

On launch day, a live feed of this historic launch will be available to the media at SpaceX Headquarters in El Segundo, CA – five minutes south of Los Angeles International Airport. The address is 1310 East Grand Avenue El Segundo, CA 90245.

Media check-in will begin at 3:30 p.m. PST on launch day. The launch time is expected to be 4:30 p.m. Food and beverages will be made available. To attend the launch viewing event, media must contact SpaceX at 310-414-6555 ext 283 or news@spacex.com. Please provide full name, affiliation, citizenship and date of birth.

Media unable to attend may listen and ask questions through a telephone conference line that will be moderated throughout the launch window. Questions from media will be taken at designated intervals.

Check-in for the media phone line will begin at 3:30 p.m. PST with coverage starting at 4:00 p.m. Accredited media can contact SpaceX at 310-414-6555 ext 283 or news@spacex.com for the access information to join the launch media event via phone.

Still photos and video of the launch will be made available on www.spacex.com within hours of the launch.




Falcon 1 on Launch Pad in Kwajalein

SpaceX Launch Overview

On launch day, the Falcon 1 rocket will begin its journey to orbit, accelerating to 17,000 mph (25 times the speed of sound) in less than ten minutes. Designed from the ground up by SpaceX, Falcon 1 is a two stage rocket powered by liquid oxygen and purified, rocket grade kerosene. On launch day, Falcon 1 will launch into the history books for several notable reasons:

* It will be the first privately developed, liquid fueled rocket to reach orbit and the world\\\\\\\\\\\\\\\'s first all new orbital rocket in over a decade.
* The main engine of Falcon 1 (Merlin) will be the first all new American hydrocarbon engine for an orbital booster to be flown in forty years and only the second new American booster engine of any kind in twenty-five years.
* The Falcon 1 is the only rocket flying 21st century avionics, which require a small fraction of the power and mass of other systems.
* It will be the world\\\\\\\\\\\\\\\'s only semi-reusable orbital rocket apart from the Shuttle.
* Most importantly, Falcon 1, priced at $6.7 million, will provide the lowest cost per flight to orbit of any launch vehicle in the world, despite receiving a design reliability rating equivalent to that of the best launch vehicles currently flying in the United States.

The maiden flight will take place from the Kwajalein Atoll of the Marshall Islands. The customer for this mission is DARPA and the Air Force. The payload will be FalconSat-2, part of the Air Force Academy’s satellite program that will measure space plasma phenomena, which can adversely affect space-based communications, including GPS and other civil and military communications. The target orbit is 400 km X 500 km (just above the International Space Station) at an inclination of 39 degrees.

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Falcon 1 Maiden Flight Update:

New Launch Time

As an additional reliability measure, SpaceX will conduct a full test of vehicle systems, including initiating the flight countdown autosequence and briefly firing the main engine on the launch stand. This test will take place Thursday, February 9 (California time). If no flight critical anomalies are detected, launch will take place on Friday, February 10. The launch window on Friday is 12 p.m. - 7 p.m. (California time).

Following the problem on Dec. 19, we flew a whole new first stage to Hawaii via C-5 just in time to catch the barge from there to Kwaj a few days before New Year's Eve. The new stage should arrive at Kwaj in about a week, whereupon we will switch it out with the damaged unit, which will be sent back to California for repair. The repair is not particularly difficult or expensive, but can only be done properly in a factory setting.

What Was the Problem?

As previously reported, we traced the problem to the failure of an electronic component in one of the first stage fuel tank pressurization valves. Although we have triple redundant pressure sensors and dual redundant pressurization valves, when this component shorted, it caused the valve controller board to reboot, effectively eliminating the redundancy.

This is the first time in 3.5 years of hard testing that we have ever seen this happen. Moreover, the component in question has a cycle life and power rating far in excess of the theoretical load that it should see. To address this specific problem, we are replacing the component with one that has a quasi-infinite lifespan and taking a few other steps that will isolate any issue with this component if it goes wrong in the future.

However, as I mentioned in an earlier update, we are not simply going to address this particular point problem and then merrily jump back into a countdown sequence. Throughout January, the SpaceX team will be doing another full review of vehicle systems, including propulsion, structures, avionics, software and ground support systems. We will be conducting additional engine tests, stage separation tests and avionics tests to once again attempt to flush out any issues. Even if we find nothing, the exercise is worthwhile.

Wind Delays Suck (Literally)

It is worth noting that we would have caught the problem without any damage to the vehicle if we had entered the final countdown sequence as planned. The sucked in tank damage only occurred because we partly drained the fuel tank due to the hold for high winds.

High winds are not a limitation of the rocket, which is designed to be essentially "all weather" and handle ground winds in excess of 50 mph (watch out for flying coconuts!). The ground winds limitation is actually due to the need to avoid a collision with the launch stand hold down arms, which grab the rocket at the base of the fuel tank, as the rocket lifts off.

To alleviate this problem, we have redesigned the launch stand so that the hold down arms retract out of the way on liftoff, activated by a breakwire. This gives us something very close to 100% winds availability from Kwaj. The retraction force is low, so even if there were an early activation of the actuator, it would not damage the rocket.

Another bothersome problem is the high rate of liquid oxygen (LOX) boiloff. This is not surprising when LOX is at -300F and there is a stiff wind impinging on the vehicle at 85F. To minimize boiloff, we will wrap the LOX tank in low cost cryo insulation attached with velcro straps that tear away on liftoff.

Lessons Learned on F1 Apply to F9

The challenges to date I think vindicate the strategy of building a small launch vehicle before a large one. If we had started out with an F9 class vehicle, the cost of every mistake would be multiplied by as much as an order of magnitude. As it is, we are able to overcome problems comparatively quickly and cheaply.

With the benefit of lessons learned on F1, it is taking far less time, effort and money to create F9. Despite the distraction of the F1 launch countdowns, I still anticipate a flight F9 first stage firing later this year and a maiden launch in late 2007.

Great Expectations

Those familiar with the launch business will know that countdown scrubs are a way of life. It's often said that the safest time to schedule your vacation is around launch day and that's true more often than not. Even rockets that have launched hundreds of times from launch pads that are in heavy use have multiple scrubs. Not too long ago, there was a Titan launch that had eleven scrubs and Delta launch that had six.

Reasons range from hard to avoid technical glitches, like the Shuttle fuel sensor malfunction on its last launch attempt, to silly false alarms. A Titan countdown was once aborted when someone spotted a "bag of suspicious liquid" on the mobile service tower. It turned out that the latrine had simply been a bridge too far for one of the technicians.

Given that Falcon 1 is an all new rocket and is launching from an all new launch pad on a remote tropical island, countdown scrubs in the first few attempts were very likely. As it is, we have had one abort due to a launch pad issue and one due to the rocket. If this next attempt succeeds in getting to t-zero, SpaceX will be reasonably fortunate in the scheme of things.

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New Horizons on Track for Jupiter

A spacecraft headed for the Solar System’s edge has aimed itself at the planet Jupiter in a long-distance slingshot on toward Pluto.

NASA’s New Horizons probe fired its thrusters in two brief maneuvers – one on Jan. 30 and an earlier event on Jan. 28 – for a total speed change of about 40 miles per hour (or about 18 meters per second). Launched on Jan. 19, New Horizons carries seven primary instruments on a mission to study Pluto, its moons and the icy Kuiper Belt objects beyond the ninth planet.

A third, final trajectory maneuver is set for Feb. 18, but New Horizons launch placed it so close to its flight path that the probe has managed save much more hydrazine propellant for later use than expected, APL spokesperson Mike Buckley told SPACE.com. The probe will swing past Jupiter on Feb. 28, 2007 and use the planet’s gravity as a boost toward Pluto, he added.

“We’re on our way to an exciting Jupiter encounter and a date with destiny at Pluto,” said New Horizons principal investigator Alan Stern, of the Southwest Research Institute in Boulder, Colorado.

Stern will celebrate the centennial anniversary of the birth of astronomer Clyde Tombaugh, who discovered Pluto in 1930, on Feb. 4 with a presentation at the University of Kansas in Lawrence, Kansas.

Tombaugh discovered Pluto on Feb. 18, 1930 at Flagstaff, Arizona’s Lowell Observatory. The University of Kansas’ Clyde Tombaugh Observatory is named after the astronomer, who died in 1997.

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Shining Light on Dark Matter

By Daniel Clery
ScienceNOW Daily News
7 February 2006

Researchers say they have for the first time measured physical properties of dark matter, the invisible stuff that makes up much of the universe. A team led by Gerry Gilmore of the Institute of Astronomy at Cambridge University detected a core of dark matter of uniform size and temperature inside dwarf galaxies. The finding runs counter to current dark matter theories, in part because the temperature measured was warmer than popular theories predict.

Astronomers have known for decades that the visible stars in a galaxy don't have enough gravity to hold it together. Large amounts of dark matter must make up the balance. But scientists have been stumped in their efforts to locate or describe it. The most popular theory suggests that dark matter consists of massive exotic particles that do not interact with normal matter except through gravity. It also holds that the particles are slow and cool. While this model fits most galaxies, it also predicts many more small galaxies than are known.

For the past 3 years, Gilmore and his team have been using giant telescopes to map the positions and velocities of thousands of stars in 10 minigalaxies around the Milky Way. Gilmore hadn't intended to make a big announcement, but on 3 February he appeared with others at a press conference in London to publicize the work of the European Southern Observatory (ESO), one of whose telescopes the team is using. At the press conference, Gilmore said the team had found the same volume of dark matter in each galaxy. The dark matter was about 1000 light-years across and had an even density equivalent to four hydrogen atoms per cubic centimeter.

The new results suggest that dark matter at the center of small galaxies is more spread out and warmer than was thought. The particles appear to have a velocity of 9 kilometers per second, and Gilmore believes that they interact with one another via some unknown force to spread out evenly. The nature of dark matter particles themselves remains one of the biggest mysteries of physics.

Scientists are reacting cautiously until they learn more about Gilmore's find, which he intends to submit to Astrophysical Journal. But the claim alone "will generate a lot of excitement," says cosmologist Robert Nichol of the University of Portsmouth, U.K. Mario Mateo of the University of Michigan, Ann Arbor, who also studies dwarf galaxies, was surprised by the density of dark matter Gilmore found. Still, he says, it's "pretty amazing" that although scientists can't see it or measure it, "we can start talking about constraining the nature of dark matter."