Piú viste - The Universe in Super Definition |
Proxima_Centauri_B_-_4.jpgNightside of Proxima Centauri "b" (Imagination)115 visitenessun commentoMareKromium
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IC-348-PIA12210.jpgCreation...104 visiteThis artist's conception shows a lump of material in a swirling, planet- forming disk. Astronomers using NASA's Spitzer Space Telescope found evidence that a companion to a star -- either another star or a planet -- could be pushing planetary material together, as illustrated here.
Planets are born out of spinning disks of gas and dust. They can carve out lanes or gaps in the disks as they grow bigger and bigger. Scientists used Spitzer's infrared vision to study the disk around a star called LRLL 31, located about 1000 LY away in the IC 348 Region of the constellation Perseus. Spitzer's new infrared observations reveal that the disk has both an inner and outer gap.
What's more, the data show that infrared light from the disk is changing over as little time as one week -- a very unusual occurrence. In particular, light of different wavelengths seesawed back and forth, with short-wavelength light going up when long-wavelength light went down, and vice versa.
According to astronomers, this change could be caused by a companion to the star (illustrated as a planet in this picture). As the companion spins around, its gravity would cause the wall of the inner disk to squeeze into a lump. This lump would also spin around the star, shadowing part of the outer disk. When the bright side of the lump is on the far side of the star, and facing Earth, more infrared light at shorter wavelengths should be observed (hotter material closer to the star emits shorter wavelengths of infrared light). In addition, the shadow of the lump should cause longer-wavelength infrared light from the outer disk to decrease. The opposite would be true when the lump is in front of the star and its bright side is hidden (shorter-wavelength light would go down, and longer- wavelength light up). This is precisely what Spitzer observed.
The size of the lump and the planet have been exaggerated to better illustrate the dynamics of the system.MareKromium
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NGC-2237_and_NGC-2244-SST.jpgThe "O" Stars inside the Rosette Nebula103 visiteIn this sub-frame are highlighted 5 dangerous hot stars that can be found inside the Rosette Nebula; these stars are classified as "O" Stars (meaning stars with a surface temperatures of 25.000 Kelvins - such as 24.726,85° Celsius - or higher).
Astronomers calculate that cool stars wandering within about 1,6 Light-Years of the Rosette's "O" Stars are in danger of having their planet forming disks destroyed.
MareKromium
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Red_Sun-PIA13994.jpgRed Sun101 visiteCaption NASA:"This artist's concept illustrates a young, Red Dwarf Star surrounded by three planets. Such stars are dimmer and smaller than yellow stars like our Sun, which makes them ideal targets for astronomers wishing to take images of planets (called "Exoplanets") outside our Solar System. NASA's Galaxy Evolution Explorer is helping to identify young, Red Dwarf Stars that are close to us by detecting their UltraViolet Light (stars give off a lot of UV Light in their youth). Astronomers will use telescopes to try to image giant planets that orbit farther out from these stars, such as the one depicted here at lower left".MareKromium
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M 64.jpgM 64 (NGC 4826) - Great Spiral Galaxy100 visiteThe "Sleeping Beauty Galaxy" may appear peaceful at first sight but it is actually tossing and turning. In an unexpected twist, recent observations have shown that the gas in the outer regions of this spiral is rotating in the opposite direction from all of the stars! Collisions between gas in the inner and outer regions are creating many hot blue stars and pink emission nebulae. The above image was taken by the Hubble Space Telescope in 2001. The fascinating internal motions of M 64 (also known as NGC 4826), are thought to be the result of a collision between a small galaxy and a large galaxy where the resultant mix has not yet settled down.
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NGC-2683.jpgNGC 2683 - Spiral Edge-On Galaxy100 visitenessun commentoMareKromium
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Proxima_Centauri_B_-_5.jpgOverview of Proxima and its Parent Star92 visiteOverview and comparison of the orbital distance of the habitable zones of Proxima Centauri compared to the Solar System.MareKromium
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NGC-4696.jpgNGC 469687 visiteIn many cosmic environments, when material falls toward a Black Hole energy is produced as some of the matter is blasted back out in jets. In fact, such Black Hole "Engines" appear to be the most efficient in the Universe, at least on a galactic scale. This composite image illustrates one example of an elliptical galaxy with an efficient Black Hole Engine, NGC 4696. The large galaxy is the brightest member of the Centaurus galaxy cluster, some 150 MLY away. Exploring NGC 4696 in X-Rays (red) astronomers can measure the rate at which infalling matter fuels the supermassive Black Hole and compare it to the energy output in the jets to produce giant radio emitting bubbles. The bubbles, shown here in blue, are about 10.000 LY across. The results confirm that the process is much more efficient than producing energy through nuclear reactions - not to mention using fossil fuels. Astronomers also suggest that as the Black Hole pumps out energy and heats the surrounding gas, star formation is ultimately shut off, limiting the size of large galaxies like NGC 4696.
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M-002-PIA04926.jpgM 2 - Globular Star Cluster in Aquarius67 visiteCaption NASA originale:"This image of the Globular Cluster Messier 2 (M2) was taken by Galaxy Evolution Explorer on August 20, 2003. This image is a small section of a single All Sky Imaging Survey exposure of only 129 seconds in the constellation Aquarius. This picture is a combination of Galaxy Evolution Explorer images taken with the far ultraviolet (colored blue) and near ultraviolet detectors (colored red). Globular clusters are gravitationally bound systems of hundreds of thousands of stars that orbit in the halos of galaxies. The globular clusters in out Milky Way galaxy contain some of the oldest stars known. M2 lies 33.000 LY from our Sun with stars distributed in a spherical system with a radius of approximately 100 LY".
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YoungStar-PIA09266.jpgThe "O"-Star65 visite"The further on the edge, the hotter the intensity," sings Kenny Loggins in "Danger Zone," a song made famous by the movie "Top Gun." The same words ring true for young, cooler stars like our sun that live in the danger zones around scorching hot stars, called O-stars. The closer a young, maverick star happens to be to a super hot O-star, the more likely its burgeoning planets will be blasted into space.
This artist's animation illustrates how this process works. The movie begins by showing an O-star in a murky star-forming region. It then pans out to show a young, cooler star and its swirling disk of planet-forming material. Disks like this one, called protoplanetary disks, are where planets are born. Gas and dust in a disk clumps together into tiny balls that sweep through the material, growing in size to eventually become full-grown planets.
The young star happens to lie within the "danger zone" around the O-star, which means that it is too close to the hot star to keep its disk. Radiation and winds from the O-star boil and blow away the material, respectively. This process, called photoevaporation, is sped up here but takes anywhere from 100,000 to about 1,000,000 years. Without a disk, the young star will not be able to produce planets.
Our own sun and its suite of planets might have grown up on the edge of an O-star's danger zone before migrating to its current, spacious home. However, we know that our young sun didn't linger for too long in any hazardous territory, or our planets, and life, wouldn't be here today.
NASA's Spitzer Space Telescope surveyed the danger zones around five O-stars in the Rosette nebula. It was able to determine that the zones are spheres with a radius of approximately 1.6 light-years, or 10 trillion miles.
MareKromium
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W-5_Star_Forming_Region-PIA11726.jpgIn the Cosmic Hurricane...65 visiteThis image from NASA's Spitzer Space Telescope shows the nasty effects of living near a group of massive stars: radiation and winds from the massive stars (white spot in center) are blasting planet-making material away from stars like our sun. The planetary material can be seen as comet-like tails behind three stars near the center of the picture. The tails are pointing away from the massive stellar furnaces that are blowing them outward. The picture is the best example yet of multiple sun-like stars being stripped of their planet-making dust by massive stars.
The sun-like stars are about 2 three 3 million years old, an age when planets are thought to be growing out of surrounding disks of dust and gas. Astronomers say the dust being blown from the stars is from their outer disks. This means that any Earth-like planets forming around the sun-like stars would be safe, while outer planets like Uranus might be nothing more than dust in the wind.
This image shows a portion of the W5 star-forming region, located 6,500 light-years away in the constellation Cassiopeia. It is a composite of infrared data from Spitzer's infrared array camera and multiband imaging photometer. Light with a wavelength of 3.5 microns is blue, while light from the dust of 24 microns is orange-red.MareKromium
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Blue_Star-PIA12174.jpgSpace "Cube"65 visiteThis drawing illustrates the extent to which astronomers have been underestimating the proportion of small to big stars in certain galaxies. Data from NASA's Galaxy Evolution Explorer Spacecraft and the Cerro Tololo Inter-American Observatory in Chile have shown that, in some cases, there can be as many as four times more small stars compared to large ones.
In the drawing, a massive blue star is shown next to a stack of lighter, yellow stars. These big blue stars are 3 to 20 times more massive than our Sun, while the smaller stars are typically about the same mass as the Sun or smaller.
Before the Galaxy Evolution Explorer study, astronomers assumed there were 500 small stars for every massive one (lower stack on right). The new observations reveal that, in certain galaxies, this estimation is off by a factor of four; for every massive star, there could be as many as 2000 small counterparts (such as the entire stack - the "Cube" - on the right).MareKromium
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