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۶ آبان ۱۳۸۶
تصوير دنباله دار هولمز پس از فوران در شب جمعه ۴ آبان. در اين تصوير گازهاي غبار گونه را شاهد هستيم که منبسط شده اند همچنين هسته دنباله دار همچون نقطه اي مي درخشد.(احسان رستمي زاده)
در این روزها منجمان در سراسر دنیا از ظهور دنباله دار هولمز در آسمان شب، شگفت زده شدهاند! این جمله ایست که در روزهای اخیر در بزرگترین سایت های نجومی دنیا شاهد آن هستیم. اما به راستی موضوع چیست؟
کمتر از یک هفته پیش دنباله داری با نام هولمز (17P) در مدار دورهای خود با قدر 17 میان دو سیاره مریخ و مشتری ظاهر شد. از آن پس در روز چهارشنبه 2 آبان بود که ناظران آسمان شاهد درخشش ستارهای تابان در صورت فلکی برساوش و به رنگ نارنجی-زرد در آسمان شب بودند. در این بین روشن شدن و فوران این دنباله دار سبب شد که یک میلیون بار پرنورتر شود و به قدر 2.5 برسد. در حقیقت همین موضوع بود که سبب شد این دنباله دار به جرمی جنجالی تبدیل شود چراکه اکنون به مانند ستارهای پرنور بود که با وجود ماه کامل و آلودگیهای نوری شهرها حتی با چشم غیر مسلح نیز رویت می شد. در خلال روز بعد دنباله دار منبسط شد، حال منجمان میتوانستند با دوربینهای دوچشمی و تلسکوپها، حلقه و هسته ای کوچک را از آن شاهد باشند. اما این جرم به دنباله دارهایی که تا کنون رصد شده بودند شباهت نداشت.
البته لازم به ذکر است که اینگونه فورانهای موحش در دنباله دار سابقه نیز داشته است. 115 سال پیش در نوامبر سال 1892، هنگامی که «ادوین هولمز» به سوی دنباله دار نشانه رفت به قدر 5 رسیده بود.
فوران انفجاری
اولین کسی که دادههای اخیر را برای انجمن بین المللی نجوم (IAU)، ارسال کرد، شخصی با نام «هنریک سانتانا» (Henriquez Santana)، از
جزایر قناری بود، این گزارش اندکی پس از نیمه شب ارسال شد.
دنباله دار هولمز در آلودگي نوري شهرها، زير نورماه کامل و در آسمان نيمه صاف نيز رصد شده است.(سعيد بهرامي نژاد)
در پی آن انجمن بین المللی نجوم بخشنامه 8886 را در روز 2 آبان منتشر کرد. در آن هنگام، بر طبق گزارش دو رصدگر از اسپانیا قدر دنباله دار از 8 به 7.3 رسیده بود.
اکنون بحثها در گروهها٬ وبلاگها و سایتهای اینترنتی شکل گرفته بود. منجمان از همان نخستین لحظات با هم توافق داشتند و بر این عقیده بودند که هولمز دنباله داری شگفت انگیز و دل فریب است.
دیری نگذشت که در شب هنگام خبرها از غرب به شرق کره خاکی کشیده شده بود، در ژاپن، کشوری بزرگ و با آلودگی نوری فراوان. گزارشها از «سچی یوشیدا» (Seiichi Yoshida)، حاکی از آن بود که این منجم توانسته است دنباله دار را در کنار رودی در یوکوهاما، مشاهده کند. زمان ساعت 17:15 به وقت جهانی را نشان میداد و او در گزارشش قدر دنباله دار را 2.8 ثبت کرده بود.
هولمز همواره دارای حلقهای گازی و واضح است، و هسته آن درخشش را حفظ کرده بود. کارشناسان دنباله دارها اینگونه
پیش بینی کرده بودند که درخشندگی دنباله دار هولمز در روزهای آینده پایدار است و همواره در آسمان منبسط خواهد شد، و با سرعت کمی به مغرب صورت فلکی برساوش حرکت میکند. این صورت فلکی همواره برای ساکنان شمال زمین قابل رویت است.
و ... در این روزها منجمان در سراسر دنیا از ظهور دنباله دار هولمز در آسمان شب، شگفت زده شدند!
مشاهدات، ثبتها و پروژههای آماتوری و حرفهای زیادی در این روزها انجام شد، میتوان گفت که برای اغلب منجمان روزهای پرکاری سپری شده است و نتایج آن را می توان در گالری
سایتها، گزارشات و مقالات منتشر شده شاهد بود. لازم به ذکر است که این دنباله دار در ایران و شهر های بزرگ آن رویت شده و ثبتهای زیاد از این پدیده سبب شده تا ایران را از کشورهای فعال در این موضوع خوانده شود.
تصويري از دنباله دار هولمز در نخستين لحظات بعد از انفجار، شما مي توانيد پوشش هيدروژني، بخش کما و هسته دنباله دار را به طور کاملا محسوس مشاهده نماييد.(ايليا تيموري)
توضیح:" وقتی دنباله داری از خورشید دور باشد، تنها از هسته ای تشکیل می شود که معمولا با نام گلوله برفی کثیف توصیف می شود. چنین توصیفی نشان می دهد که دنباله داران حاوی ذرات غبار مانند همراه با یخ و گازهای منجمد هستند. وقتی هسته به فاصله حدود 3AU از خورشید می رسد، بادها تابش های خورشیدی لایه خارجی ماده منجمد آن را تبخیر و ناحیه ای وسیع از گاز را اطراف هسته (Nucleus)، ایجاد می کنند که آن را کما (Coma)، می نامیم. کما ماهیتی رقیق دارد چرا که درخشش ستارگان از میان آن قابل رویت است، گرچه هسته دنباله دار اغلب کوچک است و چندین کیلومتر بیشتر نیست، اما کما معمولا آنقدر بزرگ می شود که به چندین برابر قطر زمین می رسد، و دراین هنگام که دنباله دار به خورشید نزدیک شده دمای آن گاه به چندین هزار درجه نیز می رسد. و زمانی که دنباله دار به خورشید نزدیک می شود پوشش هیدروژنی پیدا می کند که تا ده ها میلیون کیلومتر ادامه دارد. شما می توانید این پوشش را به رنگ سبز در تصویر مشاهده کنید برای ثبت آن به نوردهی بلندتری نیاز دارید."
| 07.26.07 | |
| As of Thursday, July 26, NASA rovers Spirit and Opportunity are both enduring levels of reduced power supply. The rovers can survive at these levels, but NASA continues to sharply restrict their activities. Spirit is under the dustiest sky ever seen at that location. Sunlight at Spirit's location is more obscured than current conditions for Opportunity, though not as severe as what Opportunity faced a week ago.  Image right: This is a view from Mars Reconnaissance Orbiter of the dust storms around Spirit and Opportunity. Image credit: NASA/JPL/MSSS + Full image and caption Mission controllers Thursday received the first status report from Opportunity in three days. This delay had been planned between transmissions to minimize the rover’s energy use. Power output from Opportunity's solar panels has climbed above 200 watt hours per day (enough to run a 100 watt bulb for two hours), compared with daily levels as low as 128 watt hours last week. Light must reach the solar panels for them to provide electricity. Opportunity has resumed measurements of how obscured the sun is. These had been suspended for several days to save power. The new measurement included in Thursday's downlink indicates slight clearing. However, some dust has freshly settled onto the solar panels, lessening the increase in power output. "We are still waiting out the storms, and we don't know how long they will last or how bad they will get," said John Callas, rover project manager at NASA's Jet Propulsion Laboratory, Pasadena, Calif. Each rover has eight radioisotope heater units that supplement electric heaters for keeping batteries and electronics within their operating temperature ranges. The radioisotope heater units use the decay heat from plutonium-238. Each of them provides about one watt of heat. They aid the rovers' survival on very low-power days and through cold nights, though the electric heaters are also necessary. Controllers are keeping Opportunity on an extremely low-power-use plan under which the rover transmits information to Earth only once every three days. A heater switch that has been stuck in the on position since landing day makes Opportunity more vulnerable to low power than Spirit. Spirit has suspended most activities, but is still communicating daily. Previous status report Media contacts: Guy Webster Jet Propulsion Laboratory, Pasadena, Calif. 818-354-6278/5011 | |
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07.19.07 | |
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Scientists have recently discovered that the planet Saturn is turning 60 - not years, but moons. | |
TLP از نگاه خدمه آپولو ۱۳
عكسي از يك TLP که در سال 1953 گرفته شده است. پدیده ای کوچک به صورت نقطه ای روشن در دل تصویر.
باربارا میدل هارست و پاتریک مور، نقشه ای را بر مبنای بررسي ۳۰۰ TLP تهیه کرده اند. TLPهاي سرخ فام با رنگ قرمز و بقيه آن ها با رنگ زرد در تصوير مشخص شده اند.A solar system is a group of heavenly bodies consisting of a star and the planets and other objects orbiting around it. We are most familiar with our own solar system, which includes Earth, seven other major planets, and the sun. Our solar system also includes many smaller objects that revolve around the sun, such as dwarf planets, meteoroids, and comets; and a thin cloud of gas and dust known as the interplanetary medium. More than 100 moons, also called satellites, orbit the planets.
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An orbiting solar telescope known as the Solar and Heliospheric Observatory (SOHO) studies the sun's interior, its atmosphere, and the solar wind, a stream of electrically charged particles that flow from the sun's surface. The European Space Agency launched the telescope in 1995. Image credit: NASA/ESA/Solar & Heliospheric Observatory |
Besides the sun, Earth, and Earth's moon, many objects in our solar system are visible to the unaided eye. These objects include the planets Mercury, Venus, Mars, Jupiter, and Saturn; the brightest asteroids; and occasional comets and meteors. Many more objects in the solar system can be seen with telescopes.
Since the 1990's, astronomers have discovered many planets orbiting distant stars, though the planets cannot be seen directly. By studying the masses and orbits of these planets, astronomers hope to learn more about solar systems in general. For example, our own solar system contains four small, rocky planets near the sun—Mercury, Venus, Earth, and Mars—and four giant, gaseous planets farther out—Jupiter, Saturn, Uranus, and Neptune. Astronomers were surprised to find that other stars have giant, gaseous planets in close orbits. For example, a planet nearly the size of Jupiter orbits the star 51 Pegasi closer than Mercury orbits our own Sun.
Our solar system
The sun is the largest and most important object in our solar system. It contains 99.8 percent of the solar system's mass (quantity of matter). The sun provides most of the heat, light, and other energy that makes life possible.
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The sun is much larger than Earth. From the sun's center to its surface, it is about 109 times the radius of Earth. Some of the streams of gas rising from the solar surface are larger than Earth. Image credit: World Book illustration by Roberta Polfus |
The sun's outer layers are hot and stormy. The hot gases and electrically charged particles in those layers continually stream into space and often burst out in solar eruptions. This flow of gases and particles forms the solar wind, which bathes everything in the solar system.
Planets orbit the sun in oval-shaped paths called ellipses, according to a law of planetary motion discovered by German astronomer Johannes Kepler in the early 1600's. The sun is slightly off to the side of the center of each ellipse at a point called a focus. The focus is actually a point inside the sun—but off its center—called the barycenter of the solar system.
The inner four planets consist chiefly of iron and rock. They are known as the terrestrial (earthlike) planets because they are somewhat similar in size and composition. The four outer planets are giant worlds with thick, gaseous outer layers. Almost all their mass consists of hydrogen and helium, giving them compositions more like that of the sun than that of Earth. Beneath their outer layers, the giant planets have no solid surfaces. The pressure of their thick atmospheres turns their insides liquid, though they may have rocky cores.
Dwarf planets are round objects smaller than planets that also orbit the sun. Unlike a planet, a dwarf planet lacks sufficient gravitational pull to sweep other objects from the region of its orbit. As a result, dwarf planets are found among populations of smaller bodies. The dwarf planet Ceres, for example, orbits in a region of space called the Main Belt between the orbits of Mars and Jupiter. Ceres shares the Main Belt with millions of smaller asteroids.
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Pluto is so far from Earth that even powerful telescopes reveal little detail of its surface. The Hubble Space Telescope gathered the light for the pictures of Pluto shown here. Image credit: NASA |
Other dwarf planets orbit primarily beyond Neptune in a region of space known as the Kuiper Play this Pronunciation. «KY pur» belt. They share this region with many smaller, icy, cometlike bodies.Together, these objects are known as the Kuiper belt objects (KBO’s). Compared to the planets, KBO’s tend to follow irregular, elongated orbits. Dwarf planets of the Kuiper belt include Pluto and a larger body designated 2003 UB313.
Moons orbit all the planets except Mercury and Venus. The inner planets have few moons. Earth has one, and Mars has two tiny satellites. The giant outer planets, however, resemble small solar systems, with many moons orbiting each planet. Jupiter has at least 63 moons. Jupiter's four largest moons are known as the Galilean satellites because the Italian astronomer Galileo discovered them in 1610 with one of the first telescopes. The largest Galilean satellite—and the largest satellite in the solar system—is Ganymede, which is even bigger than Mercury. Saturn has at least 56 moons. The largest of Saturn's moons, Titan, has an atmosphere thicker than Earth's and a diameter larger than that of Mercury. Uranus has at least 27 moons, and Neptune has at least 13. The giant planets probably have more small moons not yet discovered.
Many dwarf planets, asteroids, and other bodies also have smaller moons. Pluto’s moon measures half Pluto’s diameter. 2003 UB313 has a smaller moon around 1⁄8 its diameter.
Rings of dust, rock, and ice chunks encircle all the giant planets. Saturn's rings are the most familiar, but thin rings also surround Jupiter, Uranus, and Neptune.
Comets are snowballs composed mainly of ice and rock. When a comet approaches the sun, some of the ice in its nucleus (center) turns into gas. The gas shoots out of the sunlit side of the comet. The solar wind then carries the gas outward, forming it into a long tail.
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Ganymede, a moon of Jupiter, has craters and cracks on its surface. Asteroids and comets that hit Ganymede made the craters. The cracks are due to expansion and contraction of the surface. Image credit: NASA |
Astronomers divide comets into two main types, long-period comets, which take 200 years or more to orbit the sun, and short-period comets, which complete their orbits in fewer than 200 years. The two types come from two regions at the edges of the solar system. Long-period comets originate in the Oort cloud, a cluster of comets far beyond the orbit of Pluto. The Oort cloud was named after the Dutch astronomer Jan H. Oort, who first suggested its existence. Short-period comets come from the Kuiper belt. Many of the objects in the Oort cloud and the Kuiper belt may be chunks of rock and ice known as planetesimals left over from the formation of the solar system.
Asteroids are minor planets. Some have elliptical orbits that pass inside the orbit of Earth or even that of Mercury. Others travel on a circular path among the outer planets. Most asteroids circle the sun in a region called the asteroid belt, between the orbits of Mars and Jupiter. The belt contains more than 200 asteroids larger than 60 miles (100 kilometers) in diameter. Scientists estimate that there are more than 750,000 asteroids in the belt with diameters larger than 3/5 mile (1 kilometer). There are millions of smaller asteroids. Astronomers have even found several large asteroids with smaller asteroids orbiting them.
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The asteroid Ida is about 35 miles (55 kilometers) long. It is one of thousands of asteroids in the asteroid belt, a region between the orbits of Mars and Jupiter. Image credit: NASA |
Meteoroids are chunks of metal or rock smaller than asteroids. When meteoroids plunge into Earth's atmosphere, they form bright streaks of light called meteors as they disintegrate. Some meteoroids reach the ground, and then they become known as meteorites. Most meteoroids are broken chunks of asteroids that resulted from collisions in the asteroid belt. During the 1990's, astronomers discovered a number of meteoroids that came from Mars and from the moon. Many tiny meteoroids are dust from the tails of comets.
Heliosphere is a vast, teardrop-shaped region of space containing electrically charged particles given off by the sun. Scientists do not know the exact distance to the heliopause, the limit of the heliosphere. Many astronomers think that the heliopause is about 9 billion miles (15 billion kilometers) from the sun at the blunt end of the "teardrop."
Formation of our solar system
Many scientists believe that our solar system formed from a giant, rotating cloud of gas and dust known as the solar nebula. According to this theory, the solar nebula began to collapse because of its own gravity. Some astronomers speculate that a nearby supernova (exploding star) triggered the collapse. As the nebula contracted, it spun faster and flattened into a disk.
The nebular theory indicates that particles within the flattened disk then collided and stuck together to form asteroid-sized objects called planetesimals. Some of these planetesimals combined to become the nine large planets. Other planetesimals formed moons, asteroids, and comets. The planets and asteroids all revolve around the sun in the same direction, and in more or less the same plane, because they originally formed from this flattened disk.
Most of the material in the solar nebula, however, was pulled toward the center and formed the sun. According to the theory, the pressure at the center became great enough to trigger the nuclear reactions that power the sun. Eventually, solar eruptions occurred, producing a solar wind. In the inner solar system, the wind was so powerful that it swept away most of the lighter elements -- hydrogen and helium. In the outer regions of the solar system, however, the solar wind was much weaker. As a result, much more hydrogen and helium remained on the outer planets. This process explains why the inner planets are small, rocky worlds and the outer planets, except for Pluto, are giant balls composed almost entirely of hydrogen and helium.
Other solar systems
Several other stars have disk-shaped clouds around them that seem to be solar systems in formation. In 1983, an infrared telescope in space photographed such a disk around Vega, the brightest star in the constellation Lyra. This discovery represented the first direct evidence of such material around any star except the sun. In 1984, astronomers photographed a similar disk around Beta Pictoris, a star in the southern constellation Pictor.
By the early 2000's, astronomers had discovered that more than 50 stars like our sun have planets orbiting them. In almost all cases, they found only one planet per star. All the planets found are probably gaseous with no solid surface.
Contributor: Jay M. Pasachoff, Ph.D., Field Memorial Professor of Astronomy and Director, Hopkins Observatory of Williams College.
How to cite this article: To cite this article, World Book recommends the following format: Pasachoff, Jay M. "Solar system." World Book Online Reference Center. 2004. World Book, Inc. http://www.worldbookonline.com/wb/Article?id=ar518960.
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درست همان گونه که انحراف و فاصله جزئی بین چشم های انسان، امکان درک عمق تصویر را به انسان می دهد، قرارگیری این دو ماهواره در مدارهای تعیین شده نیز، امکان تهیه تصاویر سه بعدی از خورشید را فراهم می نماید. این نحوه قرارگیری فضاپیماها، هم چنین به آن ها این امکان را می دهد تا نسبت به اندازه گیری سرعت ذرات ساطع شده از سطح خورشید و میدان مغناطیسی اطراف خورشید نیز اقدام نمایند.این دو رصدخانه فضایی، طی ماموریت دوساله شان، اطلاعات ارزشمندی راجع به چگونگی شکل گیری خورشید، سیر تکامل و تغییرات رخ داده در آن و تاثیرات بین سیاره ای ناشی از انفجارهای رخ داده در سطح خورشید و توده های جرم ناشی از آن که از سطح خورشید خارج می شوند – از سهمگین ترین انفجارات موجود در منظومه شمسی – به زمین ارسال خواهند نمود.توانایی پیش بینی نمودن این انفجارها و آتشفشان های سطح خورشید، این امکان را به ماهواره ها و شبکه های انتقال نیرو در سطح زمین می دهد تا زمان کافی برای افزایش و به کارگیری اقدامات ایمنی داشته باشند و هم چنین درک بهتر این پدیده ها، به مهندسان و متخصصان کمک می نماید تا سیستم هایی ایمن تر و کارآتر را طراحی نمایند.. ماموریت "استریو" که در چارچوب طرح "کاوشهای زمینی-خورشیدی" اداره علوم فضایی سازمان ناسا قرار دارد،شامل دو فضاپیما است.هدف از ماموریت "استریو "،بررسی نحوه جریان انرژی و ماده از خورشید به سمت زمین و بدست آوردن ساختار سه بعدی و علت بروز فورانهای عظیم ماده که از لایه بیرونی خورشید،موسوم به تاج coronaبه سمت بیرون پرتاب می شوند است.همچنین دانشمندان به کمک این ماموریت،قادر به دریافت هشدارهای لازم در مورد فورانهای خورشیدی که مستقیما به سمت زمین حرکت می کنند هستند.
تصوير زير يكي از تصاوير تركيبي است كه از دو جهت مختلف تصوير برداري شده است.
سايت استريو : http://stereo.gsfc.nasa.gov |
Comet McNaught (C/2006 P1) has not only become the brightest comet SOHO has ever seen, but even the brightest comet observed in over forty years! The comet swung by the sun on Jan 12th - 15th, and is now emerging into the skies of the southern hemisphere. During its close encounter with our mother star, comet McNaught became a naked-eye object in broad daylight. It was discovered on August 7th, 2006 by the hugely successful comet discoverer Rob McNaught (Siding Spring Survey). At time of discovery, the comet was a very faint object, but the predicted perihelion distance (closest distance to the sun) of just 0.17 AU indicated already that the object had the potential to become very bright.
As you are probably aware, the LASCO instrument on-board SOHO has the ability to watch comets as they get extremely close to the Sun. Fortunately for us, comet McNaught has passed right through the LASCO C3 field of view! We do not know exactly the peak brightness of the comet yet, but it is definitely brighter than -3 mag! It is thus much brighter than comet NEAT or comet 96P/Machholz. In other words, comet McNaught is by far the brightest and most spectacular comet SOHO has ever seen!
Comet McNaught |
 Large JPEG Image / High-Res TIFF Image (4.8 MB) |
 Quicktime Movies: Large / Medium / Small MPEG Movies: Large / Medium / Small |
 False-color image of comet McNaught using a LASCO C3 blue filter image with a short exposure time of 4.8 sec. This image shows the structure of the comet in more detail. The head of the comet, however, was so bright that it still saturated the CCD chip (see below). (High-Res TIFF Image) |
The comet appeared in the field of view of SOHO's coronagraph LASCO C3 at around 02:00 UT (05:00 EDT) on January 12th. It passed its perihelion around 19:00 UT on January 12th, and exited C3's field of view at roughly 03:00UT on January 16th.
Since LASCO was built to observe the faint solar corona, its exposure times are not tuned to handle objects as bright as this extraordinary comet. In fact, comet McNaught is so bright that it saturates the CCD camera so that "bleeding" occurs along pixel rows. There is a bright horizontal streak on either side of the comet's head, because the charge leaks easier along the direction in which the CCD image is read out by the associated electronics.
The lower the magnitude number, the brighter the object. The brightest stars in the sky are categorized as zero or first magnitude. Negative magnitudes are reserved for the most brilliant objects: the brightest star is Sirius (-1.4); the full Moon is -12.7; the Sun is -26.7.
مترجم :آرش فراست
منبع : مجله S & T فوريه 2006
لازم به ذكر است اين نويسنده( Sara Seager) اختر فيزيكدان عضو دانشگاه كارنيج (Carnegie) واشنگتن و متخصص مطالعه بر روي سيارات فراخورشيدي است
