CDer:000024255 楼主: jadiyd

[视图资料] Astronomy Picture of the Day-2009-每日天文一图第三季(updating)

 楼主| 发表于 2009-05-05 13:01 | 显示全部楼层
2009 May 5

Titan Beyond the Rings
Credit: Cassini Imaging Team, ISS, JPL, ESA, NASA
Explanation: When orbiting Saturn, be sure to watch for breathtaking superpositions of moons and rings. One such picturesque vista was visible recently to the robot Cassini spacecraft now orbiting Saturn. In 2006 April, Cassini captured Saturn's A and F rings stretching in front of cloud-shrouded Titan. Near the rings and appearing just above Titan was Epimetheus, a moon which orbits just outside the F ring. The dark space in the A ring is called the Encke Gap, although several thin knotted ringlets and even the small moon Pan orbit there. Cassini and curious Earthlings await the coming Saturnian equinox this summer when the ring plane will point directly at the Sun. Mysterious spokes and telling shadows are expected to become visible that might give away more clues about the nature of Saturn's ring particles.
 楼主| 发表于 2009-05-06 19:46 | 显示全部楼层
2009 May 6

A Spring Sky Over Hirsau Abbey
Credit & Copyright: Till Credner, AlltheSky.com
Explanation: What's in the sky tonight? When strolling outside just after sunset, even if just going out to your car, a casual glance upwards can reveal a beautiful night sky also seen by many people across the Earth. To see your local version of the above image, start by facing south, and then tilt your head back. Visible nearly above you, during springtime at sunset in much of the northern hemisphere, will be the Big Dipper, part of the constellation of the Big Bear. The cup end of the Big Dipper will point to the North Star Polaris, the star around which the whole sky would seem to spin, if you could watch for hours. Polaris is at the tip of the Little Dipper, otherwise known as the constellation of the Little Bear. Depending on the time of night, other visible constellations would include Bootes, Leo, Gemini, and Auriga. The above fisheye image was taken from Germany last week. Visible around the entire image edge is the courtyard of Hirsau Abbey, once a Benedictine Monastery founded in the year 830. Moving your cursor over the image will bring up an annotated version of the above image, including the location of the planet Saturn.
影像提供及版权:Till Credner, AlltheSky.com
 楼主| 发表于 2009-05-09 12:04 | 显示全部楼层
2009 May 8

Galaxies of the Perseus Cluster
Credit & Copyright: R. Jay Gabany
Explanation: This colorful telescopic skyscape is filled with galaxies that lie nearly 250 million light-years away, the galaxies of the Perseus cluster. Their extended and sometimes surprising shapes are seen beyond a veil of foreground stars in our own Milky Way. Ultimately consisting of over a thousand galaxies, the cluster is filled with yellowish elliptical and lenticular galaxies, like those scattered throughout this view of the cluster's central region. Notably, the large galaxy at the left is the massive and bizarre-looking NGC 1275. A prodigious source of high-energy emission, active galaxy NGC 1275 dominates the Perseus cluster, accreting matter as entire galaxies fall into it and feed the supermassive black hole at the galaxy's core. Of course, spiral galaxies also inhabit the Perseus cluster, including the small, face-on spiral NGC 1268, right of picture center. The bluish spot on the outskirts of NGC 1268 is supernova SN 2008fg. At the estimated distance of the Perseus galaxy cluster, this field spans about 1.5 million light-years.
影像提供及版权R. Jay Gabany
 楼主| 发表于 2009-05-10 15:38 | 显示全部楼层
2009 May 10

M31: The Andromeda Galaxy
Credit & Copyright: Robert Gendler (robgendlerastropics.com)
Explanation: Andromeda is the nearest major galaxy to our own Milky Way Galaxy. Our Galaxy is thought to look much like Andromeda. Together these two galaxies dominate the Local Group of galaxies. The diffuse light from Andromeda is caused by the hundreds of billions of stars that compose it. The several distinct stars that surround Andromeda's image are actually stars in our Galaxy that are well in front of the background object. Andromeda is frequently referred to as M31 since it is the 31st object on Messier's list of diffuse sky objects. M31 is so distant it takes about two million years for light to reach us from there. Although visible without aid, the above image of M31 is a digital mosaic of 20 frames taken with a small telescope. Much about M31 remains unknown, including how it acquired its unusual double-peaked center.
 楼主| 发表于 2009-05-11 16:22 | 显示全部楼层
2009 May 11

Forty Thousand Meteor Origins Across the Sky
Credit & Copyright: SonotaCo Network, Japan
Explanation: Where do meteors come from? Visible meteors are typically sand-sized grains of ice and rock that once fragmented from comets. Many a meteor shower has been associated with a known comet, although some intriguing orphan showers do remain. Recently, a group of meteor enthusiasts created a network of over 100 video cameras placed at 25 well-separated locations across Japan. This unprecedented network recorded not only 240,000 optically bright meteors over two years, but almost 40,000 meteors seen by more than one station. These multiple-station events were particularly interesting because they enabled the observers to extrapolate meteor trajectories back into the Solar System. The resulting radiant map is shown above, with many well known meteor showers labelled by the first three letters of the home constellation. Besides known meteor showers, eleven new showers were identified by new radiants on the sky from which meteors appear to flow. The meteor sky is ever changing, and it may be possible that new shower radiants will appear in the future. Research like this could also potentially identify previously unknown comets or asteroids that might one day pass close to the Earth.
 楼主| 发表于 2009-05-12 14:38 | 显示全部楼层
本帖最后由 jadiyd 于 2009-5-13 12:19 编辑

Astronomy Picture of the Day2009 May 12

An Iridescent Cloud Over Ohio

Explanation: Why would a cloud appear to be different colors? A relatively rare phenomenon known as iridescent clouds can show unusual colors vividly or a whole spectrum of colors simultaneously. These clouds are formed of small water droplets of nearly uniform size. When the Sun is in the right position or mostly hidden by thick clouds, these thinner clouds significantly diffract sunlight in a nearly coherent manner, with different colors being deflected by different amounts. Therefore, different colors will come to the observer from slightly different directions. Many clouds start with uniform regions that could show iridescence but quickly become too thick, too mixed, or too far from the Sun to exhibit striking colors. This iridescent cloud was photographed through a polarized lens above Dublin, Ohio last week.
 楼主| 发表于 2009-05-13 12:18 | 显示全部楼层
2009 May 13

A Space Shuttle Before Dawn
Credit & Copyright: Charles Danforth (CASA, U. Colorado)
Explanation: This shuttle has launched to space. Pictured above, the Space Shuttle Atlantis sat on Launch Pad 39A before dawn last month as it was prepared for the launch. The shuttle itself is visible on the image right, attached to a brown liquid fuel tank and two white solid rocket boosters. In the image center is the Fixed Service Structure which stands just over 100 meters tall, including the white lightning rod at the top. Starting on Sunday, the space shuttle embarked on one of its most ambitious missions ever: its fourth mission to fix and upgrade the ageing Hubble Space Telescope. Hubble's replacement, the James Webb Space Telescope, is currently scheduled for launch in 2014.
 楼主| 发表于 2009-05-14 12:22 | 显示全部楼层
2009 May 14

Elusive Jellyfish Nebula
Credit & Copyright: Gerhard Bachmayer
Explanation: Normally faint and elusive, the Jellyfish Nebula is caught in this alluring wide-field telescopic view. Flanked by two yellow-tinted stars, Mu and Eta Geminorum, at the foot of a celestial twin, the Jellyfish Nebula is the brighter arcing ridge of emission with dangling tentacles right of center. In fact, the cosmic jellyfish is seen to be part of bubble-shaped supernova remnant IC 443, the expanding debris cloud from a massive star that exploded. Light from the explosion first reached planet Earth over 30,000 years ago. Like its cousin in astrophysical waters the Crab Nebula supernova remnant, IC 443 is known to harbor a neutron star, the remnant of the collapsed stellar core. Emission nebula Sharpless 249 fills the field at the upper left. The Jellyfish Nebula is about 5,000 light-years away. At that distance, this image would be almost 200 light-years across.
 楼主| 发表于 2009-05-15 12:37 | 显示全部楼层
本帖最后由 jadiyd 于 2009-5-16 16:32 编辑

2009 May 15

M97: The Owl Nebula
Credit & Copyright: Keith Quattrocchi
Explanation: The Owl Nebula is perched in the sky about 2,600 light-years away toward the bottom of the Big Dipper's bowl. Also cataloged as M97, the 97th object in Messier's well-known list, its round shape along with the placement of two large, dark "eyes" do suggest the face of a staring owl. One of the fainter objects in Messier's catalog, the Owl Nebula is a planetary nebula, the glowing gaseous envelope shed by a dying sun-like star as it runs out of nuclear fuel. In fact, the Owl Nebula offers an example of the fate of our Sun as it runs out of fuel in another 5 billion years. As we see it, the nebula spans over 2 light-years making it roughly 2,000 times the size of Solar System. Beautiful to look at, this color image shows impressive details within the cosmic owl. The composite includes images made through narrow-band filters for a total of 24 hours of exposure time.
影像提供及版权Keith Quattrocchi
 楼主| 发表于 2009-05-16 16:32 | 显示全部楼层
2009 May 16

Atlantis and Hubble Side by Side
Credit & Copyright: Thierry Legault
Explanation: On Wednesday, May 13, two, tiny, fast moving spots crossed an otherwise featureless solar disk. Not sunspots though, the dark blemishes were silhouettes of the shuttle orbiter Atlantis and the Hubble Space Telescope side by side. To record this sharp picture of the orbiting pair against the face of the Sun, astronomer Thierry Legault carefully set up his camera and telescope near the center of a 5 kilometer wide path of visibility about 100 kilometers south of Kennedy Space Center in Florida. He opened the shutter for 1/8,000 second at 12:17 EDT, catching Atlantis and Hubble at a range of 600 kilometers while they were moving at 7 kilometers/second. The total duration of the transit (Sun crossing) was 0.8 seconds. Enlarged in the inset view, Atlantis (top) is approaching Hubble prior to capturing the space telescope. Thursday, astronauts began a series of spacewalks to perform the maintenance as part of the final mission to Hubble.
发表于 2009-05-16 21:55 | 显示全部楼层
 楼主| 发表于 2009-05-20 15:21 | 显示全部楼层
2009 年 05 月 19 日

影像提供及版权:Robert Gendler (robgendlerastropics.com)
 楼主| 发表于 2009-05-20 15:23 | 显示全部楼层
本帖最后由 jadiyd 于 2009-5-21 15:25 编辑

2009 May 20

Above Earth, Fixing Hubble
Credit: STS-125 Crew, NASA
Explanation: What is that astronaut doing? Fixing the Hubble Space Telescope. During the fourth servicing mission to upgrade and fix Hubble, astronaut Michael Good can be seen attached to the shuttle's robotic arm, working in an open panel of Hubble. Far below, the terminator between day and night can be seen across planet Earth. Since Hubble was captured by the space shuttle Atlantis last Wednesday, five long space-walks have been used to fix and upgrade the aging telescope. One of the more ambitious orbital missions yet taken, the toiling astronauts have upgraded the Wide Field Camera, fixed the Advanced Camera for Surveys, repaired the Space Telescope Imaging Spectrograph, and replaced COSTAR with the Cosmic Origins Spectrograph. Numerous other general repairs included replacing batteries, gyroscopic sensors, and insulation panels. Hubble will now undergo testing as Atlantis prepares to return to Earth later this week.
影像提供:STS-125 Crew, NASA
说明:宇航员正在做什么?安装哈勃太空望远镜。宇航员Michael Good第四次维护使命中,对哈勃望远镜进行升级和装配,可以看到宇航员被固定在航天飞机的机械手臂上,正在一块打开的面板上操作。更下侧可以看到地球的明暗交界线。从上周三亚特兰蒂斯号航天飞机与哈勃对接之后,将有5次长时间的太空行走,对望远镜进行安装及升级。此次雄心勃勃的轨道使命之一还包括宇航员升级广角相机,安装先进的巡天相机,修复太空望远镜的成像摄谱仪,以及用宇宙起源摄谱仪替换光学改正系统。还有众多需要大修的地方,包括更换电池,回转仪以及绝缘板。在本周末,当亚特兰蒂斯号准备返回地球时,哈勃将经历测试阶段。
 楼主| 发表于 2009-05-21 15:26 | 显示全部楼层
2009 May 21

IC 4592: A Blue Horsehead
Credit & Copyright: Rogelio Bernal Andreo
Explanation: This complex of beautiful, dusty reflection nebulae lies in the constellation Scorpius along the plane of our Milky Way Galaxy. Its overall outline suggests a horsehead in profile, though it covers a much larger region than the better known Horsehead Nebula of Orion. The star near the eye of the horse and the center of the 5 degree wide field, is embedded in blue reflection nebula IC 4592 over 400 light-years away. At that distance, the view spans nearly 40 light-years. The horse's gaze seems fixed on Beta Scorpii, also named Graffias, the bright star at the lower left. Toward the top right, near the horse's ear, is another striking bluish reflection nebula, IC 4601. The characteristic blue hue of reflection nebulae is caused by the tendency of interstellar dust to more strongly scatter blue starlight.
 楼主| 发表于 2009-05-23 12:38 | 显示全部楼层
2009 年 05 月 22 日


影像提供及版权[email=ybialets%20at%20eso%20dot%20org]Yuri Beletsky[/email] (ESO)

 楼主| 发表于 2009-05-23 12:39 | 显示全部楼层
2009 May 23

Apollo 12 and Surveyor 3 Stereo View
Credit Apollo 12, NASA; Stereo Image by Patrick Vantuyne
Explanation: Put on your red/blue glasses and gaze into this dramatic stereo view from the surface of the Moon. The 3D scene features Apollo 12 astronaut Pete Conrad visiting the Surveyor 3 spacecraft in November of 1969. The image was carefully created from two separate pictures (AS12-48-7133, AS12-48-7134) taken on the lunar surface. They depict the scene from only slightly different viewpoints, approximating the separation between human eyes. Combining images, one tinted red and the other blue-green, with the correct offset, produces the stereo effect when viewed using red/blue glasses, the red filter covering the left eye. The color filters guide each eye to see only the picture with the correct corresponding viewpoint. The particular pair of images chosen also required a slight tilt to optimize the stereo effect. While you've got those glasses on, web sources of astronomy and space science stereo images include the Mars Path Finder archive, a 3D Tour of the Solar System, and stereo experimenter Patrick Vantyune's own set of stereo images from the Apollo missions to the Moon.
 楼主| 发表于 2009-05-24 12:38 | 显示全部楼层
2009 May 24

Carina Nebula Panorama from Hubble
Credit: NASA, ESA, N. Smith (U. California, Berkeley) et al., and The Hubble Heritage Team (STScI/AURA)
Explanation: In one of the brightest parts of Milky Way lies a nebula where some of the oddest things occur. NGC 3372, known as the Great Nebula in Carina, is home to massive stars and changing nebula. Eta Carinae, the most energetic star in the nebula, was one of the brightest stars in the sky in the 1830s, but then faded dramatically. The Keyhole Nebula, visible left the center, houses several of the most massive stars known and has also changed its appearance. The entire Carina Nebula spans over 300 light years and lies about 7,500 light-years away in the constellation of Carina. Pictured above is the most detailed image of the Carina Nebula ever taken. The controlled color image is a composite of 48 high-resolution frames taken by the Hubble Space Telescope two years ago. Wide-field annotated and zoomable image versions are also available.
 楼主| 发表于 2009-05-25 16:23 | 显示全部楼层
2009 May 25

Hubble Floats Free
Credit: STS-125 Crew, NASA
Explanation: Why put observatories in space? Most telescopes are on the ground. On the ground, you can deploy a heavier telescope and fix it more easily. The trouble is that Earth-bound telescopes must look through the Earth's atmosphere. First, the Earth's atmosphere blocks out a broad range of the electromagnetic spectrum, allowing a narrow band of visible light to reach the surface. Telescopes which explore the Universe using light beyond the visible spectrum, such as those onboard the Chandra X-ray Observatory, and the Fermi Gamma Ray Space Telescope need to be carried above the absorbing atmosphere. Second, the Earth's atmosphere blurs the light it lets through. The blurring is caused by varying density and continual motion of air. By orbiting above the Earth's atmosphere, the Hubble Space Telescope, pictured above last week after being captured, refurbished, and released, can get clearer images. In fact, even though HST has a mirror 15 times smaller than large Earth-bound telescopes, it can still resolve finer details. A future large telescope for space, the James Webb Space Telescope is currently planned for launch in
 楼主| 发表于 2009-05-26 13:20 | 显示全部楼层
2009 May 26

Whirlpool Galaxy Deep Field
Credit & Copyright: Jon Christensen
Explanation: Follow the handle of the Big Dipper away from the dipper's bowl, until you get to the handle's last bright star. Then, just slide your telescope a little south and west and you might find this stunning pair of interacting galaxies, the 51st entry in Charles Messier's famous catalog. Perhaps the original spiral nebula, the large galaxy with well defined spiral structure is also cataloged as NGC 5194. Its spiral arms and dust lanes clearly sweep in front of its companion galaxy (left), NGC 5195. The pair are about 31 million light-years distant and officially lie within the angular boundaries of the small constellation Canes Venatici. Though M51 looks faint and fuzzy to the human eye, the above long-exposure, deep-field image taken last month shows much of the faint complexity that actually surrounds the smaller galaxy.
 楼主| 发表于 2009-05-27 19:09 | 显示全部楼层
2009 May 27

Volcanic Terrain on Mercury
Explanation: Why are many large craters on Mercury relatively smooth inside? Recent images from the robotic MESSENGER spacecraft that flew by Mercury last October show previously uncharted regions of Mercury that have large craters with an internal smoothness similar to the maria on Earth's own Moon. Therefore, like our Moon's maria, these craters on Mercury are thought to have been flooded by lava floes that are old but not as old as the surrounding more highly cratered surface. The above image mosaic of the western limb of Mercury was created by MESSENGER as it approached the Solar System's innermost planet last October. Old and heavily textured terrain runs across much of the image bottom, while across the middle left lies comparatively smooth impact basins where small craters may appear similar at first to protruding hills. MESSENGER will buzz past Mercury again next year before entering orbit in 2011.
说明: 在水星上为什么会有这么多大型的陨石坑具有如此相对平滑的内部?去年10月飞越水星的信使号飞船传回了最新影像,在未曾记录的水星表面有很多大型的火山口,且火山口内部十分平滑,如同月球上的月海(maria)一般。这些水星上的火山口被认为跟月海成因相似,表面受到陨石撞击后,由内部熔岩溢流而成,因此内部平滑区域比附近高地年轻。上面这张水星西部边缘影像,是去年10月信使号飞船通过太阳系这颗最内部行星时所拍摄。古老而具有粗糙纹理的地表贯穿影像底部,而在中间偏左的地方,具有相对平滑的撞击表面,那里可能产生过相似的撞击,从而产生高地。在2011年信使号飞船进入水星轨道前,明年还会再次掠过水星
 楼主| 发表于 2009-05-28 13:25 | 显示全部楼层
2009 May 28

Moon in the Mullica
Credit & Copyright: Jerry Lodriguss (Catching the Light)
Explanation: Still waters mimic a predawn sky along the eastern horizon in this peaceful scene. The picture was recorded on May 22nd from the banks of the Mullica River, in a forested region known as the Pine Barrens of southern New Jersey on the US east coast. Near the horizon at the left is an old Moon with its narrow, sunlit crescent. Mars is near picture center and brilliant Venus shines farther right. Like the terrestrial lights along the riverbank, the bright celestial beacons are all reflected in the watery foreground. Of course, most of the Moon is illuminated by Earthshine, light reflected from the sunlit side of planet Earth itself, revealing features on the darkened lunar surface.
 楼主| 发表于 2009-05-29 23:58 | 显示全部楼层
2009 May 29

Messier 106
Credit & Copyright: Ken Crawford (Rancho Del Sol Observatory)
Explanation: Close to the Great Bear (Ursa Major) and surrounded by the stars of the Hunting Dogs (Canes Venatici), this celestial wonder was discovered in 1781 by the metric French astronomer Pierre Mechain. Later, it was added to the catalog of his friend and colleague Charles Messier as M106. Modern deep telescopic views reveal it to be an island universe -- a spiral galaxy around 30 thousand light-years across located only about 21 million light-years beyond the stars of the Milky Way. Along with a bright central core, this colorful composite image highlights youthful blue star clusters and reddish stellar nurseries tracing the galaxy's spiral arms. It also shows remarkable reddish jets of glowing hydrogen gas. In addition to small companion galaxy NGC 4248 near the picture's right edge, background galaxies can be found scattered throughout the frame. M106 (aka NGC 4258) is a nearby example of the Seyfert class of active galaxies, seen across the spectrum from radio to x-rays. Active galaxies are believed to be powered by matter falling into a massive central black hole.
 楼主| 发表于 2009-05-30 15:17 | 显示全部楼层
2009 May 30

A Beautiful Trifid
Credit & Copyright: Ed Henry
Explanation: The beautiful Trifid Nebula is a colorful study in cosmic contrasts. Also known as M20, it lies about 5,000 light-years away toward the nebula rich constellation Sagittarius. A star forming region in the plane of our galaxy, the Trifid illustrates three different types of astronomical nebulae; red emission nebulae dominated by light emitted by hydrogen atoms, blue reflection nebulae produced by dust reflecting starlight, and dark nebulae where dense dust clouds appear in silhouette. The bright red emission region, roughly separated into three parts by obscuring, dark dust lanes, lends the Trifid its popular name. In this gorgeous wide view, the red emission is also juxtaposed with the telltale blue haze of reflection nebulae. Pillars and jets sculpted by newborn stars, left of the emission nebula's center, appear in Hubble Space Telescope close-up images of the region. The Trifid Nebula is about 40 light-years across.
 楼主| 发表于 2009-05-31 16:40 | 显示全部楼层
2009 May 31

A Solar Prominence from SOHO
Credit: SOHO-EIT Consortium, ESA, NASA
Explanation: How can gas float above the Sun? Twisted magnetic fields arching from the solar surface can trap ionized gas, suspending it in huge looping structures. These majestic plasma arches are seen as prominences above the solar limb. In 1999 September, this dramatic and detailed image was recorded by the EIT experiment on board the space-based SOHO observatory in the light emitted by ionized Helium. It shows hot plasma escaping into space as a fiery prominence breaks free from magnetic confinement a hundred thousand kilometers above the Sun. These awesome events bear watching as they can affect communications and power systems over 100 million kilometers away on Planet Earth. Recently, our Sun has been unusually quiet.
 楼主| 发表于 2009-06-01 12:16 | 显示全部楼层
2009 June 1

Spirit Encounters Soft Ground on Mars
Credit: Mars Exploration Rover Mission, JPL, NASA
Explanation: Will Spirit be able to free itself from soft ground on Mars? The robotic Spirit rover currently rolling across Mars ran into unexpectedly soft ground last month while exploring the red planet. A worry is that the ground is so soft that Spirit won't be able to free itself, will have to stay put and thereafter study what it can from its current position near an unusual martian land feature named Home Plate. Pictured above, the front left wheel appears to be primarily digging itself in when spun, while on the other side, the front right wheel no longer spins and is dragged by the five year old mechanical explorer. In the distance, rocks and rusty dirt fill the alien landscape in front of the distant Husband Hill. NASA continues to study the situation, and engineers and scientists have not yet run out of ideas of how to use Spirit's six wheels. Far across Mars, Spirit's twin Opportunity continues on its two year trek toward Endeavour crater.
 楼主| 发表于 2009-06-02 12:22 | 显示全部楼层
本帖最后由 jadiyd 于 2009-6-3 12:19 编辑

2009 June 2

Spokes Reappear on Saturn's Rings
Credit: Cassini Imaging Team, ISS, JPL, ESA, NASA
Explanation: What causes the mysterious spokes in Saturn's rings? Visible in the above image as light ghostlike impressions, spokes were first discovered by the Voyager spacecraft that buzzed by Saturn in the early 1980s. Their existence was unexpected. Oddly, the spokes more commonly observed when Saturn's rings are more nearly edge on to the Sun, and so were conspicuously absent from initial images sent back by the robot Cassini spacecraft now orbiting Saturn. Analyses of archived Voyager images have led to the conclusions that the transient spokes, which may form and dissipate over a few hours, are composed of electrically charged sheets of small dust-sized particles. Hypotheses for spoke creation include small meteors impacting the rings and electron beams from Saturnian atmospheric lightning spraying the rings. As Saturn approaches equinox, spoke sightings like that pictured above are becoming increasingly common, giving planetary scientists fresh images and data with which to test origin hypotheses.
 楼主| 发表于 2009-06-03 12:19 | 显示全部楼层
本帖最后由 jadiyd 于 2009-6-4 12:24 编辑

2009 June 3

VB 10: A Large Planet Orbiting a Small Star
Illustration Credit: JPL-Caltech, NASA
Explanation: Can a planet be as large as the star that it orbits? Recent observations have discovered that nearby Van Biesbroeck's star might have just such a large planet. Although VB 10 lies only about 20 light years away, it is a small red dwarf star so dim, at 17th magnitude, that a telescope is needed to see it. Van Biesbroeck's star was previously known for its rapid proper motion across the sky -- it moves so fast it could cross a full moon in only about 1,000 years. By noting a wiggle in VB 10's sky trajectory, astronomers were able to infer the existence of a planet several times the mass of Jupiter. Although the star VB 10 is perhaps 10 times more massive than the discovered planet VB 10b, the star is likely more highly compressed and so the two might be closely matched in size. Such a system is envisioned above with an artist's illustration. Since faint M-type stars like VB 10 are so common, planetary systems surrounding them, including planets larger than their parent star, might be more common than planetary systems like our own Solar System.
说明:行星能与它绕行的恒星一样大吗?最近观测发现,附近的Van Biesbroeck恒星可能就有这样一颗大型行星。尽管VB10距离仅仅20光年远,它是一颗小红矮星,非常昏暗,亮度只有17,需要望远镜才能看到它。Van Biesbroeck恒星最初以其在天空中快速的自行而闻名,它移动很快,仅仅大约1,000光年就能通过一个满月的距离。通过记录VB10在天空中运行轨迹的大小天文学家就能推测出那里有一颗质量是木星数倍的行星。尽管恒星VB10的质量可能是已发现行星VB10b10倍多,但是恒星可能更紧密,因此两颗天体在大小上很相像。这样的系统可以被想象成上面艺术家的插图一样。因为类似VB10这样的昏暗M-型恒星很普遍,它们周围有行星系统环绕可能比我们太阳系内的行星系统更为普遍,其中还包括行星比母恒星更大的情况。
 楼主| 发表于 2009-06-04 12:24 | 显示全部楼层
2009 June 4

Sunspots on a Cloudy Day
Credit & Copyright: Stefan Seip (TWAN)
Explanation: On June 2nd, clouds over Stuttgart, Germany parted to reveal what has become a relatively rare sight, spots on the Sun. In fact, the roughly 11-year solar activity cycle is still in a surprisingly deep minimum and the years 2008 and 2009 have had the lowest sunspot counts since the 1950s. Even the latest prediction is that the new cycle, Solar Cycle 24, will reach a maximum in May 2013 with a below-average sunspot count. The Solar Cycle 24 sunspots recorded here are in active region AR 1019. Previously, only two cycle 24 active regions with sunspots, AR 1018 and AR 1017, were seen in May. Free Lecture: An APOD editor will review great space images this Friday in Kalamazoo, >Michigan.
 楼主| 发表于 2009-06-05 16:15 | 显示全部楼层
2009 June 5

Stars and Dust Across Corona Australis
Credit & Copyright: [email=oreshko at lgn dot ru]Andrey Oreshko[/email]
Explanation: Cosmic dust clouds sprawl across a rich field of stars in this sweeping telescopic vista near the northern boundary of Corona Australis, the Southern Crown. Probably less than 500 light-years away and effectively blocking light from more distant, background stars in the Milky Way, the densest part of the dust cloud is about 8 light-years long. At its tip (upper right) is a group of lovely reflection nebulae cataloged as NGC 6726, 6727, 6729, and IC 4812. A characteristic blue color is produced as light from hot stars is reflected by the cosmic dust. The smaller yellowish nebula (NGC 6729) surrounds young variable star R Coronae Australis. Magnificent globular star cluster NGC 6723 is at the upper right corner of the view. While NGC 6723 appears to be part of the group, it actually lies nearly 30,000 light-years away, far beyond the Corona Australis dust clouds.
说明:这张在南冕座北部边界拍摄到的广阔望远镜影像中,宇宙尘埃云弥漫在恒星富集的区域内。尘埃云的致密部分大约有8光年长,距离我们不到500光年远,并且有效地阻挡了我们银河系遥远背景恒星发出的星光。在它的顶部(右上方)是一组可爱的反射星云,分别被编录为NGC6726,6727,6729以及IC4812。象征性的蓝色辉光是炽热恒星发出,经由宇宙尘埃反射。较小的泛黄色星云(NGC6729)围绕着年轻的变星R Coronae Australis周围。华丽的球状星团NGC 6723位于影像的右上角。而NGC6723看上去好像是星团的一部分,但实际距离我们近3光年远,距离南冕座尘埃云较远。
 楼主| 发表于 2009-06-06 17:57 | 显示全部楼层
2009 June 6

One-Armed Spiral Galaxy NGC 4725
Credit & Copyright: Mike Siniscalchi
Explanation: While most spiral galaxies, including our own Milky Way, have two or more spiral arms, NGC 4725 seems to have only one. In this sharp color image, the solo spira mirabilis is tightly wound, traced by bluish, newborn star clusters. The odd galaxy also sports obscuring dust lanes, a prominent ring, and a yellowish central bar structure composed of an older population of stars. NGC 4725 is over 100 thousand light-years across and lies 41 million light-years away in the well-groomed constellation Coma Berenices. Computer simulations of the formation of single spiral arms suggest that they can be either leading or trailing arms with respect to a galaxy's overall rotation.
 楼主| 发表于 2009-06-08 16:28 | 显示全部楼层
2009 June 8

Possible Jet Blown Shells Near Microquasar Cygnus X-1
Credit & Copyright: [email= steve at lightbuckets dot com]Steve Cullen[/email] (lightbuckets.com)
Explanation: What happens to matter that falls toward an energetic black hole? In the case of Cygnus X-1, perhaps little of that matter actually makes it in. Infalling gas may first collide not only with itself but with an accretion disk of swirling material surrounding the black hole. The result may be a microquasar that glows across the electromagnetic spectrum and produces powerful jets that expel much of the infalling matter back into the cosmos at near light speed before it can even approach the black hole's event horizon. Confirmation that black hole jets may create expanding shells has come recently from the discovery of shells surrounding Cygnus X-1. Pictured above on the upper right is one such shell quite possibly created by the jet of microquasar and black hole candidate Cygnus X-1. Rolling your cursor over the image will bring up an annotated version. The physical processes that create the black hole jets is a topic that continues to be researched.
 楼主| 发表于 2009-06-09 19:48 | 显示全部楼层
2009 June 9

Markarian's Chain of Galaxies
Credit & Copyright: [email= piotr_sadowski at wr.home.pl]Piotrek Sadowski[/email]
Explanation: Across the heart of the Virgo Cluster of Galaxies lies a striking string of galaxies known as Markarian's Chain. The chain, pictured above, is highlighted on the upper right with two large but featureless lenticular galaxies, M84 and M86. Prominent to their lower left is a pair of interacting galaxies known as The Eyes. The home Virgo Cluster is the nearest cluster of galaxies, contains over 2000 galaxies, and has a noticeable gravitational pull on the galaxies of the Local Group of Galaxies surrounding our Milky Way Galaxy. The center of the Virgo Cluster is located about 70 million light years away toward the constellation of Virgo. At least seven galaxies in the chain appear to move coherently, although others appear to be superposed by chance.
说明:穿过室女座星系团的中心,那里有一条被称为马卡林之链的壮观星系队列。如上面影像所示,链条突出了右上角的两个巨大而又普通的透镜状星系M84M86。而位于它们左下方的是一对被称为The Eyes相互吸引的星系。室女座星系团是距离我们最近的星系团,其中含有超过2,000个星系,对银河系周围本地星系群内的星系有明显的引力牵拉作用。室女座星系团的中心位于室女座方向上,距离我们大约7,000光年。在这条星系链上至少有7个星系结合在一起,尽管其它也有几个星系看上去碰巧也叠加在这条星系链上。
 楼主| 发表于 2009-06-10 12:43 | 显示全部楼层
本帖最后由 jadiyd 于 2009-6-11 13:38 编辑

2009 June 10

A Dusty Iris Nebula

Credit &
[email= alvin at lightbuckts dot com]Alvin Jeng[/email]
These clouds of interstellar dust and gas have blossomed 1,300 light-years away in the fertile star fields of theconstellation Cepheus. Sometimes called the Iris Nebula and dutifully cataloged asNGC 7023, this is not the only nebula in the sky to evoke the imageryof flowers. Surrounding it, obscuring clouds of dust and cold molecular gas are also present and can suggest otherconvolutedandfantasticshapes. Within the Iris, dusty nebular material surrounds a hot, young star. The dominant color of the brighter reflection nebula is blue,characteristic of dustgrains reflecting starlight. Central filaments of the cosmic dust glow with a faint reddish photoluminesence as some dust grainseffectively convertthe star's invisibleultravioletradiation to visible red light. Infraredobservationsindicate that this nebula may contain complex carbon molecules known asPAHs. At the estimated distance of the Iris Nebulathis remarkable wide field view is over 30light-years across.
 楼主| 发表于 2009-06-11 13:37 | 显示全部楼层
本帖最后由 jadiyd 于 2009-6-12 21:29 编辑

2009 June 11

Pyrenees Paraselene
Credit & Copyright: Patrick Lécureuil
Explanation: A sea of clouds laps at rugged moutain peaks of the French Pyrenees in this serene view from Pic du Midi Observatory. The time exposure was recorded on June 4, with the constellations Sagittarius and Scorpius shining in the starry night. At the top right lies a faint, but colorful moondog or paraselene. Analogous to a sundog or parhelion, the paraselene is produced by moonlight shining through thin, hexagonal-shaped ice crystals in high cirrus clouds. As determined by the ice crystal geometry, a bright gibbous Moon illuminates the scene from beyond the picture's right edge, 22 degrees from the lovely paraselene.
 楼主| 发表于 2009-06-12 21:29 | 显示全部楼层
2009 June 12

SNR 0104: An Unusual Suspect
Credit: X-ray: NASA / CXC / Penn State / S.Park & J.Lee; Infrared: NASA / JPL-Caltech
Explanation: SNR 0104 is a supernova remnant with an unusual shape. Found 190,000 light-years away in our neighboring galaxy the Small Magellanic Cloud, SNR 0104 is suspected of being the expanding debris cloud from a Type 1a supernova - the catastrophic thermonuclear explosion of a white dwarf star. For example, like Type 1a supernova remnants within our galaxy, investigations show that it contains large amounts of iron. But unlike other Type 1a remnants, including the well-studied Tycho, Kepler, and SN 1006, SNR 0104 is definitely not spherical. In fact, the remnant's shape suggests this supernova explosion was very asymmetric and produced strong jets. This intriguing composite image combines Chandra Observatory x-ray data of the remnant, shown in purple hues, with Spitzer Space Telescope infrared data covering the wider region, mapped to red and green colors. It indicates that the supernova explosion took place in the complicated and dense environment of a star-forming region. So, an alternative explanation is that the expanding debris cloud is sweeping up clumpy interstellar material, accounting for the odd shape of SNR 0104. The broad, multiwavelength view spans about 1,800 light-years at the estimated distance of SNR 0104.
 楼主| 发表于 2009-06-13 17:33 | 显示全部楼层
2009 June 13

The Milky Road
Credit & Copyright: Larry Landolfi
Explanation: Inspired by the night skies of planet Earth in the International Year of Astronomy, photographer Larry Landolfi created this tantalizing fantasy view. The composited image suggests a luminous Milky Way is the heavenly extension of a country road. Of course, the name for our galaxy, the Milky Way (in Latin, Via Lactea), does refer to its appearance as a milky band or path in the sky. In fact, the word galaxy itself derives from the Greek for milk. Visible on moonless nights from dark sky areas, though not so bright or colorful as in this image, the glowing celestial band is due to the collective light of myriad stars along the plane of our galaxy, too faint to be distinguished individually. The diffuse starlight is cut by dark swaths of obscuring galactic dust clouds. Four hundred years ago, Galileo turned his telescope on the Milky Way and announced it to be "... a congeries of innumerable stars ..."
 楼主| 发表于 2009-06-14 13:01 | 显示全部楼层
2009 June 14

Stars at the Galactic Center
Credit: Susan Stolovy (SSC/Caltech) et al., JPL-Caltech, NASA
Explanation: The center of our Milky Way Galaxy is hidden from the prying eyes of optical telescopes by clouds of obscuring dust and gas. But in this stunning vista, the Spitzer Space Telescope's infrared cameras, penetrate much of the dust revealing the stars of the crowded galactic center region. A mosaic of many smaller snapshots, the detailed, false-color image shows older, cool stars in bluish hues. Reddish glowing dust clouds are associated with young, hot stars in stellar nurseries. The very center of the Milky Way was only recently found capable of forming newborn stars. The galactic center lies some 26,000 light-years away, toward the constellation Sagittarius. At that distance, this picture spans about 900 light-years.
发表于 2009-06-15 19:30 | 显示全部楼层
发表于 2009-06-16 10:46 | 显示全部楼层
发表于 2009-06-16 12:27 | 显示全部楼层
127# jadiyd

太壮观了  漂亮
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