Het astronomie topic #2

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Op vrijdag 16 maart 2007 08:41 schreef Frutsel het volgende:
Huge Frozen Lake on Southpole of Mars

Mars is unlikely to sport beachfront property any time soon, but the planet has enough water ice at its south pole to blanket the entire planet in more than 30 feet of water if everything thawed out.

With a radar technique, astronomers have penetrated for the first time about 2.5 miles (nearly four kilometers) beneath the south pole's frozen surface.

[afbeelding]
_{The south polar layered ice deposits of Mars, with purple thinnest and red thickest. The black circle was not surveyed.}

The data showed that nearly pure water ice lies beneath.

Discovered in the early 1970s, layered deposits of ice and dust cap the north and south poles of Mars. Until now, the deposits have been difficult to study closely with existing telescopes and satellites.

The current advance comes from a probe of the deposits using an instrument aboard the Mars Express orbiter.

"This is the first time that a ground-penetrating system has ever been used on Mars," said the new radar study's lead author, Jeffrey Plaut of NASA's Jet Propulsion Laboratory. "All the other instruments used to study the surface of Mars in the past really have only been sensitive to what occurs at the very surface."

(NASA's Mars Odyssey spacecraft also carries instruments designed, among other things, to probe beneath icy polar surfaces.)

Deep probe

Plaut and his colleagues probed the deposits with radar echo sounding, typically used on Earth to study the interiors of glaciers.

The instrument, called the Mars Advanced Radar for Subsurface and Ionospheric Sounding, or MARSIS, beams radio waves which penetrate the planet's surface and bounce off features having different electrical properties.

The reflected beams revealed that 90 percent or more of the frozen polar material is pure water ice, sprinkled with dust particles.

The scientists calculated that the water would form a 36-foot-deep ocean of sorts if spread over the Martian globe.

"It's the best evidence that's been obtained to date for that thickness," said Ken Herkenhoff, a planetary geologist at the U.S. Geological Survey in Flagstaff, Ariz., who studies the Martian polar regions. He was not involved in the current study.

Scientists have long known that Mars' north polar cap is a massive storehouse of water ice, and the current research team says they will use their radar technique to refine past estimates of its thickness and make-up.

Missing water

"These polar ice deposits are by far the largest reservoir of water or water ice that we know of on Mars," Plaut said.

That's a lot of water, but not enough to account for the flowing streams thought to meander along Mars' surface in the past.

"There's evidence that about 10 times or maybe even 100 times that much water has flowed across the surface of Mars to carve the various channels, the outflow valleys and other features we see in the images and topography data," Plaut told SPACE.com.

So where's the rest of the water?

One idea is that a subterranean plumbing system once ferried loads of water beneath the Martian surface.

Plaut said his team also will search for underground pools with the radar technique.

quote:

Op vrijdag 30 maart 2007 12:45 schreef Frutsel het volgende:
Many planets may have double suns

The dual suns that rise and set over Luke Skywalker's homeworld in the film Star Wars may be more than just fantasy, according to data from Nasa.
In a classic scene from the 1977 movie, the hero gazes into the distance as two yellow suns set on the horizon.

Nasa's Spitzer Space Telescope has found that planetary systems are as common around double stars as they are around single stars, like our own Sun.

Details of the research have been published in the Astrophysical Journal.

the study, a team of researchers used an infrared camera on the Spitzer telescope to search for so-called dusty discs around binary, or double, stars.

Dusty discs are made from the leftover debris of planet formation.


"We knew the stars would be there, the question was whether there was a planet to be the place where you could stand and see these sunsets," said Karl Stapelfeldt, a scientist at Nasa's Jet Propulsion Laboratory (JPL) in Pasadena, California.

"The inference is getting stronger now that there must be such planets based on what Spitzer has found."

The presence of planets in dusty discs is thought likely, but is by no means certain.

In our Solar System, asteroids collide with each other and produce showers of dust and that is, we assume, what we're seeing in these other discs - the dust produced by the collision of two bigger bodies," lead author David Trilling, from the University of Arizona, told BBC News.

"We can infer that there are bigger bodies like asteroids. The next logical leap is that if there are processes that formed these bigger bodies like asteroids, those same processes may also have formed planets." (BBC)

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Volledige artikel ---> http://news.bbc.co.uk/1/hi/sci/tech/6506081.stm

quote:

Op vrijdag 30 maart 2007 18:52 schreef ExperimentalFrentalMental het volgende:

[..]

29-03-2007

Ook veel dubbelsterren kunnen planeten hebben

[afbeelding]
Op sommige planeten zijn dubbele zonsondergangen te zien.

Sterrenkundigen hebben met behulp van de infraroodsatelliet Spitzer vastgesteld dat in dubbelstersystemen net zo vaak stofschijven voorkomen als rond enkelvoudige sterren. Dat maakt het waarschijnlijk dat ook veel dubbelsterren planeten hebben en, omgekeerd, dat er veel planeten zijn waar twee (of zelfs meer) zonnen aan de hemel staan.

Lange tijd is gedacht dat planeetvorming alleen mogelijk zou zijn in dubbelstersystemen waarin de beide componenten minstens duizend astronomische eenheden (150 miljard kilometer) uit elkaar stonden. Maar het onderzoek met Spitzer laat juist zien dat in zeer nauwe dubbelstersystemen méér stofschijven gevonden worden dan in wijde. In die gevallen blijken de dicht om elkaar draaiende sterren zelfs door één stofschijf omringd te zijn.

Het minst ‘planeetvriendelijk’ zijn dubbelsterren waarbij de twee sterren drie tot vijftig astronomische eenheden van elkaar verwijderd zijn.

(allesoversterrenkunde)