Het Astronomie Topic #5

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Op vrijdag 3 juni 2011 09:14 schreef ExperimentalFrentalMental het volgende:
02-06-2011

Europese reuzentelescoop ontdekt raadselachtige ster

In een naburig sterrenstelsel is een buitengewoon heldere ster ontdekt, die drie miljoen keer zo veel licht uitstraalt als onze zon. Dat heeft de Europese Zuidelijke Sterrenwacht ESO bekendgemaakt. Alle eerder ontdekte "supersterren" van dit kaliber maken deel uit van sterrenhopen, maar dit heldere lichtbaken is in zijn eentje. De oorsprong van deze ster is een raadsel.

Een internationaal team van astronomen heeft met de VLT-telescoop van de ESO in Chili nauwkeurig gekeken naar de ster VFTS 682 in de Grote Magelhaense Wolk, een klein buurstelsel van ons Melkwegstelsel. Uit analyse van het sterlicht blijkt dat de massa van de ster ongeveer 150 keer zo groot is als die van de zon.

VFTS 682 is niet alleen erg helder, maar ook erg heet: de oppervlaktetemperatuur bedraagt rond de 50.000 graden Celsius.
Dergelijke zware sterren zijn tot nog toe uitsluitend waargenomen in de drukke centrumgebieden van sterrenhopen, maar VFTS 682 is eenzaam.

Toch bevindt de ster zich in de buurt van de zeer rijke sterrenhoop RMC 136 die meerdere dergelijke "supersterren" omvat. Mogelijk is VFTS 682 uitgestoten door die sterrenhoop. Het is immers ook een dubbelganger van één van de helderste supersterren in het hart van RMC 136.

Maar andere bekende "wegloopsterren" zijn allemaal veel kleiner en het is onduidelijk hoe zo'n zware ster door zwaartekrachtsinteracties uit de sterrenhoop weggeslingerd kan raken, zegt de ESO. Het laat zich echter ook niet makkelijk te begrijpen hoe het ding in zijn eentje is kunnen ontstaan, aldus co-teamleider Jorick Vink. (belga/gb)

(HLN)

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June 9, 2011: NASA's Voyager probes are truly going where no one has gone before. Gliding silently toward the stars, 9 billion miles from Earth, they are beaming back news from the most distant, unexplored reaches of the solar system.

Mission scientists say the probes have just sent back some very big news indeed.

It's bubbly out there.

"The Voyager probes appear to have entered a strange realm of frothy magnetic bubbles," says astronomer Merav Opher of Boston University. "This is very surprising."

According to computer models, the bubbles are large, about 100 million miles wide, so it would take the speedy probes weeks to cross just one of them. Voyager 1 entered the "foam-zone" around 2007, and Voyager 2 followed about a year later. At first researchers didn't understand what the Voyagers were sensing--but now they have a good idea.

"The sun's magnetic field extends all the way to the edge of the solar system," explains Opher. "Because the sun spins, its magnetic field becomes twisted and wrinkled, a bit like a ballerina's skirt. Far, far away from the sun, where the Voyagers are now, the folds of the skirt bunch up."

When a magnetic field gets severely folded like this, interesting things can happen. Lines of magnetic force criss-cross and "reconnect". (Magnetic reconnection is the same energetic process underlying solar flares.) The crowded folds of the skirt reorganize themselves, sometimes explosively, into foamy magnetic bubbles.

"We never expected to find such a foam at the edge of the solar system, but there it is!" says Opher's colleague, University of Maryland physicist Jim Drake.

Theories dating back to the 1950s had predicted a very different scenario: The distant magnetic field of the sun was supposed to curve around in relatively graceful arcs, eventually folding back to rejoin the sun. The actual bubbles appear to be self-contained and substantially disconnected from the broader solar magnetic field.

Energetic particle sensor readings suggest that the Voyagers are occasionally dipping in and out of the foam—so there might be regions where the old ideas still hold. But there is no question that old models alone cannot explain what the Voyagers have found.

Says Drake: "We are still trying to wrap our minds around the implications of these findings."

The structure of the sun's distant magnetic field—foam vs. no-foam—is of acute scientific importance because it defines how we interact with the rest of the galaxy. Researchers call the region where the Voyagers are now "the heliosheath." It is essentially the border crossing between the Solar System and the rest of the Milky Way. Lots of things try to get across—interstellar clouds, knots of galactic magnetism, cosmic rays and so on. Will these intruders encounter a riot of bubbly magnetism (the new view) or graceful lines of magnetic force leading back to the sun (the old view)?

The case of cosmic rays is illustrative. Galactic cosmic rays are subatomic particles accelerated to near-light speed by distant black holes and supernova explosions. When these microscopic cannonballs try to enter the solar system, they have to fight through the sun's magnetic field to reach the inner planets.

"The magnetic bubbles could be our first line of defense against cosmic rays," points out Opher. "We haven't figured out yet if this is a good thing or not."

On one hand, the bubbles would seem to be a very porous shield, allowing many cosmic rays through the gaps. On the other hand, cosmic rays could get trapped inside the bubbles, which would make the froth a very good shield indeed.

"We'll probably discover which is correct as the Voyagers proceed deeper into the froth and learn more about its organization1," says Opher. "This is just the beginning, and I predict more surprises ahead."

Author: Dr. Tony Phillips | Credit: Science@NASA

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Op donderdag 9 juni 2011 22:15 schreef -CRASH- het volgende:
A Big Surprise from the Edge of the Solar System

[..]

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Op donderdag 16 juni 2011 08:48 schreef ExperimentalFrentalMental het volgende:
Het resultaat mag er zijn: indrukwekkend! (hlnsydney/jv)

"Plains Milky Way" | dakotalapse

(HLN)

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Op donderdag 16 juni 2011 18:01 schreef pinine het volgende:
animaties van sterren, sterrenstelsels, planeten, zwarte gaten, quasars etc.. met relax muziek

Liquid Mind (2011) - Dream Ten (Black Holes and Quasars)

Liquid Mind - Thought Museum (Star Clouds)

Liquid Mind - In The Spirit (Planetary System)

Liquid Mind - Awakening (Cosmic Sea)

Liquid Mind - In The Stillness (Exoplanets)

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NASA's Dawn mission to the doughnut-shaped asteroid belt between Mars and Jupiter, which launched in September 2007, is now approaching Vesta, a protoplanet that is currently some 143 million miles from Earth. Many surprises are likely awaiting the spacecraft.



"We often refer to Vesta as the smallest terrestrial planet," said Christopher T. Russell, a UCLA professor of geophysics and space physics in the Department of Earth and Space Sciences, and the mission's principal investigator. "It has planetary features and basically the same structure as Mercury, Venus, Earth and Mars. But because it is so small, it does not have enough gravity to retain an atmosphere, or at least not to retain an atmosphere for very long.

"There are many mysteries about Vesta," Russell said. "One of them is why Vesta is so bright. The Earth reflects a lot of sunlight - about 40 percent - because it has clouds and snow on the surface, while the moon reflects only about 10 percent of the light from the sun back. Vesta is more like the Earth. Why? What on its surface is causing all that sunlight to be reflected? We'll find out."

Dawn will map Vesta's surface, which Russell says may be similar to the moon's. He says he expects that the body's interior is layered, with a crust, a mantle and an iron core. He is eager to learn about this interior and how large the iron core is.

Named for the ancient Roman goddess of the hearth, Vesta has been bombarded by meteorites for 4.5 billion years.

"We expect to see a lot of craters," Russell said. "We know there is an enormous crater at the south pole that we can see with the Hubble Space Telescope. That crater, some 280 miles across, has released material into the asteroid belt. Small bits of Vesta are floating around and make their way all the way to the orbit of the Earth and fall in our atmosphere. About one in every 20 meteorites that falls on the surface of the Earth comes from Vesta. That has enabled us to learn a lot about Vesta before we even get there."

Dawn will arrive at Vesta in July. Beginning in September, the spacecraft will orbit Vesta some 400 miles from its surface. It will then move closer, to about 125 miles from the surface, starting in November. By January of 2012, Russell expects high-resolution images and other data about surface composition. Dawn is arriving ahead of schedule and is expected to orbit Vesta for a year.

"It's been a long trip," said Russell, who started planning the journey back in 1992. "Finally, the moment of truth is about to arrive."

Vesta, which orbits the sun every 3.6 terrestrial years, has an oval, pumpkin-like shape and an average diameter of approximately 330 miles. Studies of meteorites found on Earth that are believed to have come from Vesta suggest that Vesta formed from galactic dust during the solar system's first 3 million to 10 million years.

Dawn's cameras should be able to see individual lava flows and craters tens of feet across on Vesta's surface.

"We will scurry around when the data come in, trying to make maps of the surface and learning its exact shape and size," Russell said.

Dawn has a high-quality camera, along with a back-up; a visible and near-infrared spectrometer that will identify minerals on the surface; and a gamma ray and neutron spectrometer that will reveal the abundance of elements such as iron and hydrogen, possibly from water, in the soil. Dawn will also probe Vesta's gravity with radio signals.

The study of Vesta, however, is only half of Dawn's mission. The spacecraft will also conduct a detailed study of the structure and composition of the "dwarf planet" Ceres. Vesta and Ceres are the most massive objects in the main asteroid belt between Mars and Jupiter. Dawn's goals include determining the shape, size, composition, internal structure, and the tectonic and thermal evolution of both objects, and the mission is expected to reveal the conditions under which each of them formed.

Dawn, only the second scientific mission to be powered by an advanced NASA technology known as ion propulsion, is also the first NASA mission to orbit two major objects.

"Twice the bang for the buck on this mission," said Russell, who added that without ion propulsion, Dawn would have cost three times as much.

Unlike chemical rocket engines, ion engines accelerate their fuel nearly continuously, giving each ion a tremendous burst of speed. The fuel used by an ion engine is xenon, a gas that is also used in photo-flash units and which is more than four times heavier than air. Xenon ions shoot out the back of the engine at a speed of 90,000 miles per hour.

UCLA graduate and postdoctoral students work with Russell on the mission. Now is an excellent opportunity for graduate students to join the project and help analyze the data, said Russell, who teaches planetary science to UCLA undergraduates and solar and space physics to undergraduates and graduate students.

After orbiting Vesta, Dawn will leave for its three-year journey to Ceres, which could harbor substantial water or ice beneath its rock crust - and possibly life. On the way to Ceres, Dawn may visit another object. The spacecraft will rendezvous with Ceres and begin orbiting in 2015, conducting studies and observations for at least five months.

Russell believes that Ceres and Vesta, formed almost 4.6 billion years ago, have preserved their early record, which was frozen into their ancient surfaces.

"We're going back in time to the early solar system," he said.

The Dawn mission is managed by the Jet Propulsion Laboratory (JPL), a division of the California Institute of Technology in Pasadena, Calif., for NASA's Science Mission Directorate. Team members include scientists from JPL, the NASA Goddard Space Flight Center, the Planetary Science Institute, the Massachusetts Institute of Technology and other institutions.

Scientific partners include the Max Planck Institute for Solar System Research in Katlenburg, Germany; the DLR Institute for Planetary Research in Berlin; the Freie Universitaet in Berlin; the Italian National Institute for Astrophysics in Rome; and the Italian Space Agency.

Orbital Sciences Corp. of Dulles, Va., designed and built the Dawn spacecraft.

UCLA is in charge of Dawn's science and public outreach. Russell leads the science team; he and his colleagues make science decisions through the science center at UCLA's Institute of Geophysics and Planetary Physics. His science team has the lead role in analyzing and interpreting the data from Dawn.

Dawn is part of NASA's Discovery Program, managed by NASA's Marshall Space Flight Center in Huntsville, Ala., in which scientists find innovative ways to unlock the mysteries of our solar system by answering some of humanity's oldest questions.