ikenbot: Why Don’t We See White Holes In Space? Science fiction fans love the possibility of other universes, even more so contemplating the possibility of being able to travel between them through exotic configurations of spacetime, notably wormholes, which are pretty much just black holes with an opening poking through the singularity. Less well known is the equally exotic (and purely hypothetical) possibility of “white holes:” the opposite of black holes. Whereas matter and light can fall into a black hole and never escape, white holes would emit light and matter but wouldn’t take anything in, for example. But while we see evidence for black holes in space, thus far there hasn’t been any observational evidence of white holes. Now a physicist at the University of Oregon in Eugene thinks he might be able to explain why. Here’s the standard analogy for the formation of a wormhole: Picture a bed sheet stretched taut. Place a large bowling ball in the center of the sheet, and the sheet will bend inward in response, creating a gravitational pull. Now imagine that the bowling ball is being squeezed, so that the same amount of mass must fit into a smaller and smaller space. The ball will become denser and denser as it becomes smaller and smaller. This causes the sheet to dip lower and lower, until finally the ball has been squeezed down to the size of a pinhead. At that point, its density becomes so great and the gravitational force so strong that it pokes a small hole in the center of the sheet. That’s what would happen if a wormhole formed at the center of a black hole. But what lies on the other side? Always a stickler for symmetry in his equations, Einstein hypothesized that a “mirror universe” must exist on the other side: a “white hole.” Read on..
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unknownskywalker: Dione on a Diagonal Saturn and Dione appear askew in this Cassini view with the north poles rotated to the right, as if they were threaded along on the thin diagonal line of the planet’s rings. The image was taken in visible green light with the Cassini spacecraft wide-angle camera on Dec. 12, 2011 from a distance of approximately 57,000 km from Dione.
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future-physicist: The Sun The sun fuses 620 million metric tons of hydrogen per second into 616 million metric tons of helium. About 4 million tons of mass go “missing” every second. Of course it’s not really missing, it all gets converted into energy and every second the sun spews 4 million tons of energy in the form of light and heat across our solar system. Only about 3.6 pounds of this “missing” mass ever reaches Earth. Think about that for a minute. 3.6 pounds of mass powers all the plants, all of the animals, everyone of us on this planet. 3.6 pounds is the difference between night and day, summer and winter, life and death. Out of 4 million tons of mass per second? 3.6 pounds is pocket change. (Image Via)
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unknownskywalker: New super-earth detected within the habitable zone of a nearby star An international team of scientists has discovered a potentially habitable super-Earth orbiting a nearby star. The host star, called GJ 667C, is a M-class dwarf member of a triple-star system and has a different makeup than our Sun, with a much lower abundance of elements heavier than helium, such as iron, carbon, and silicon. The other two stars (GJ 667AB) are a pair of orange K dwarfs, with a concentration of heavy elements only 25% that of our Sun’s. Such elements are the building blocks of terrestrial planets, so it was thought to be less likely for metal-depleted star systems to have an abundance of low-mass planets. The new found planet (GJ 667Cc) has an orbital period of 28.15 days and a minimum mass of 4.5 times that of Earth. It receives 90% of the light that Earth receives. However, because most of its incoming light is in the infrared, a higher percentage of this incoming energy should be absorbed by the planet. When both these effects are taken into account, the planet is expected to absorb about the same amount of energy from its star that the Earth absorbs from the Sun. This planet is the new best candidate to support liquid water and, perhaps, life as we know it. GJ 667C also has a super-Earth (GJ 667Cb) with a period of 7.2 days, previously detected. This planet orbits so close to the star that it would be too hot for liquid water. The system might also contain a gas-giant planet and an additional super-Earth with an orbital period of 75 days. However, further observations are needed to confirm these two possibilities. This was expected to be a rather unlikely star to host planets. Yet there they are, around a very nearby, metal-poor example of the most common type of star in our galaxy. The detection of this planet, this nearby and this soon, implies that our galaxy must be teeming with billions of potentially habitable rocky planets.
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unknownskywalker: Hubble Zooms in on a Magnified Galaxy A team of astronomers aimed Hubble at one of the most striking examples of gravitational lensing, a nearly 90° arc of light in the galaxy cluster RCS2 032727-132623. Hubble’s view of the distant background galaxy, which lies nearly 10 billion light-years away, is significantly more detailed than could ever be achieved without the help of the gravitational lens. The distorted image of the galaxy is repeated several times in the foreground lensing cluster, as is typical of gravitational lenses. The challenge for astronomers was to reconstruct what the galaxy really looked like, were it not distorted by the cluster’s funhouse-mirror effect. Hubble’s sharp vision allowed astronomers to remove the distortions and reconstruct the galaxy image as it would normally look. The reconstruction (shown at lower left) revealed regions of star formation glowing like bright Christmas tree bulbs. These are much brighter than any star-formation region in our Milky Way galaxy. The small rectangle in the center shows the location of the background galaxy if the intervening galaxy cluster were not there. The rounded outlines show distinct, distorted images of the background galaxy resulting from lensing by the mass in the cluster. Through spectroscopy, the spreading out of light into its constituent colors, the team plans to analyze these star-forming regions from the inside out to better understand why they are forming so many stars. This observation provides a unique opportunity to study the physical properties of a galaxy vigorously forming stars when the universe was only one-third its present age.
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unknownskywalker: Dizzyingly fast-spinning stars slow down by flying apart Pulsars are the super-dense, strongly magnetized cores of massive stars left behind after they go supernova. They can bulk up on matter and energy by cannibalizing companion stars, making them give off X-rays and spin extraordinarily fast. Later, after siphoning all the matter, millisecond pulsars gradually slow down and emit radio waves instead. Little was known about what happens during the actual slowdown before these pulsars start blasting radio waves. But now a new study by astrophysicist Thomas Tauris at the University of Bonn in Germany found that millisecond pulsars can hit the brakes dramatically. In the end stages, the dead stars can lose more than half their rotational energy. Computer models suggest that the magnetospheres, or shells of charged particles around millisecond pulsars, grow as their companion stars shrink. This growth exerts a braking torque on the pulsars. In addition, when matter from the companion stars enters these magnetospheres, it can get blasted away instead of glomming onto the pulsars, which also helps slow the pulsar’s spinning. This means that the very same process responsible for spinning up old neutron stars to extraordinary fast spin rates with periods of 1 to 10 milliseconds is actually also causing them to spin down again. This also means that X-ray-emitting millisecond pulsars should spin faster than the millisecond pulsars emitting radio waves.
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galaxyshmalaxy: IC434 (Horsehead Nebula) (by astrorom)
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galaxyshmalaxy: IC434 (Horsehead Nebula) (by astrorom)
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unknownskywalker: Wind Shear Battering Tropical Depression Iggy NASA satellites have watched as wind shear has torn Cyclone Iggy apart over the last day. NASA infrared satellite imagery showed that Iggy’s strongest thunderstorms have been pushed away from the storm’s center and visible imagery shows the storm is being stretched out. Iggy is weakening and heading for a landfall between Geraldton and Perth.
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abcstarstuff: NASA Discovers First Earth-size Planets Beyond Our Solar System NASA’s Kepler mission has discovered the first Earth-size planets orbiting a sun-like star outside our solar system. The planets, called Kepler-20e and Kepler-20f, are too close to their star to be in the so-called habitable zone where liquid water could exist on a planet’s surface, but they are the smallest exoplanets ever confirmed around a star like our sun. The discovery marks the next important milestone in the ultimate search for planets like Earth. The new planets are thought to be rocky. Kepler-20e is slightly smaller than Venus, measuring 0.87 times the radius of Earth. Kepler-20f is slightly larger than Earth, measuring 1.03 times its radius. Both planets reside in a five-planet system called Kepler-20, approximately 1,000 light-years away in the constellation Lyra. Kepler-20e orbits its parent star every 6.1 days and Kepler-20f every 19.6 days. These short orbital periods mean very hot, inhospitable worlds. Kepler-20f, at 800 degrees Fahrenheit, is similar to an average day on the planet Mercury. The surface temperature of Kepler-20e, at more than 1,400 degrees Fahrenheit, would melt glass. “The primary goal of the Kepler mission is to find Earth-sized planets in the habitable zone,” said Francois Fressin of the Harvard-Smithsonian Center for Astrophysics in Cambridge, Mass., lead author of a new study published in the journal Nature. “This discovery demonstrates for the first time that Earth-size planets exist around other stars, and that we are able to detect them.” The Kepler-20 system includes three other planets that are larger than Earth but smaller than Neptune. Kepler-20b, the closest planet, Kepler-20c, the third planet, and Kepler-20d, the fifth planet, orbit their star every 3.7, 10.9 and 77.6 days. All five planets have orbits lying roughly within Mercury’s orbit in our solar system. The host star belongs to the same G-type class as our sun, although it is slightly smaller and cooler. The system has an unexpected arrangement. In our solar system, small, rocky worlds orbit close to the sun and large, gaseous worlds orbit farther out. In comparison, the planets of Kepler-20 are organized in alternating size: large, small, large, small and large. “The Kepler data are showing us some planetary systems have arrangements of planets very different from that seen in our solar system,” said Jack Lissauer, planetary scientist and Kepler science team member at NASA’s Ames Research Center in Moffett Field, Calif. “The analysis of Kepler data continue to reveal new insights about the diversity of planets and planetary systems within our galaxy.” Scientists are not certain how the system evolved but they do not think the planets formed in their existing locations. They theorize the planets formed farther from their star and then migrated inward, likely through interactions with the disk of material from which they originated. This allowed the worlds to maintain their regular spacing despite alternating sizes. The Kepler space telescope detects planets and planet candidates by measuring dips in the brightness of more than 150,000 stars to search for planets crossing in front, or transiting, their stars. The Kepler science team requires at least three transits to verify a signal as a planet. The Kepler science team uses ground-based telescopes and the Spitzer Space Telescope to review observations on planet candidates the spacecraft finds. The star field Kepler observes in the constellations Cygnus and Lyra can be seen only from ground-based observatories in spring through early fall. The data from these other observations help determine which candidates can be validated as planets. To validate Kepler-20e and Kepler-20f, astronomers used a computer program called Blender, which runs simulations to help rule out other astrophysical phenomena masquerading as a planet. On Dec. 5 the team announced the discovery of Kepler-22b in the habitable zone of its parent star. It is likely to be too large to have a rocky surface. While Kepler-20e and Kepler-20f are Earth-size, they are too close to their parent star to have liquid water on the surface. “In the cosmic game of hide and seek, finding planets with just the right size and just the right temperature seems only a matter of time,” said Natalie Batalha, Kepler deputy science team lead and professor of astronomy and physics at San Jose State University. “We are on the edge of our seats knowing that Kepler’s most anticipated discoveries are still to come.”
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