Star Defender

Space-based telescope will look for Earth-like planets Mar 22, 2000 The Microlensing Planet Search (MPS) collaboration has discovered the smallest known planet orbiting another star (Astrophysical Journal April 2000). The planet has a mass between that of the Earth and Neptune, which is 17 times more massive than the Earth, and was detected using a microlensing technique. "Microlensing is the only way low-mass planets can be detected from the ground," says Sun Hong Rhie from the University of Notre Dame and a member of MPS team. Rhie and his colleague David Bennett have proposed a space-based observatory called GEST that would use microlensing techniques to search for other low-mass planets. GEST would monitor over 200 million stars which, the team hopes, would allow them to observe over 100 Earth-mass planets during its two-and-a-half year lifetime (astro-ph/0003102). The microlensing technique only works with planetary systems that are in the foreground of the Galactic bulge or the inner Galactic disk. A planetary system in this area acts as a gravitational lens that bends and amplifies the light from the objects behind it. As planets orbit their star, they will slightly perturb the gravitational lens and hence cause a brief variation in the light seen from the Earth. These variations provide the mass of the planet and the distance between the planet and its star. The GEST observatory would have a 1.5 metre mirror and a CDD camera containing 1.3 billion pixels. Rhie and Bennett are cautiously organising support for the telescope, which they hope will be launched in 2005. "GEST sounds like a great idea to me," says John Bahcall from Institute for Advanced Studies in Princeton University, "but I don't know what its funding chances are." Will Sutherland from Oxford University is slightly more optimistic: "Clearly exoplanets are a big growth area, so there must be a reasonable chance of getting funding," he says. Λοιπον. Το Microlensing Planet Search ως τοτε(μεχρι το 2000) ηταν ενα τηλεσκοπιο Ground-Based το οποιο χρησημοποιουσε τεχνικες Microlensing και ειχε ανακαλυψει εναν πλανητη 17 φορες η γη σε μαζα. Τωρα (το 2000) ερχετε το τηλεσκοποια Space-Based Galactic Exoplanet Survey Telescope(ΓΕΣΤ) να εξερευνησει περισσοτερους απο 200 εκατ. αστερες για να βρε πλανητες σαν τη γη. Κυρια χαρακτηριστικα * ο 1.5 μετρα καθρευτης * η CCD καμερα των 1.3 δυςεκ. πιξελ Ξερει κανεις, τι εχει γινει με αυτο?? http://physicsworld.com/cws/article/news/2869 ΕΝΔΙΑΦΕΡΟΝ ειναι επισης http://bustard.phys.nd.edu/GEST/GEST_spie_2002.ppt Μην περιμενετε εξηγησει... Δεν καταλαβαινω χριστο απο το παραπανω Powerpoint ....

Ναι ΧαΧαΧα Γελάσαμε ΠωΠω, και λιγος χαβαλες δεν βλαπτει STAY CALM

Χμμμ... οκ τοτε. Απλος, οταν ημουν μικρος, νομιζα οτι θα μπορω να ανακαλυψω αντικειμενα , και να δω αλλους πλανητες, κτλ κτλ, που στην πραγματικοτητα, δεν γινετε....

Οκ. Αμα θελεις, μην απαντησεις Λες και ρωτησα τπτ το εξωφρενικο. Λεω την αποψη μου, στο κατω κατω. Και αμα θελεις, πουλα και τον εξοπλισμο σου, εγω δεν σου πα να κανεις κατι τετοιο Και σιγα, μην κατσω εγω, να πλακωθω με ολο το φορουμ. Ευχαριστω για την ευγενια

Η αναζήτηση για διελεύσεις επιπλέον-ηλιακων(Πως να ρο μεταφρασω??) πλανήτων κατά τη Planetary Science Institute (PSI) επιδιώκουν τον εντοπισμό νέων πλανητών(as they transit their parent stars). Για να βρουμε διέλευμενους πλανητες, εμείς ερευνησαμε, χρησιμοποιώντας υψηλής ακρίβειας CCD φωτομετρίας, έναν μεγάλος αριθμός αστέρων επανειλημμένα για πολλές νύχτες. Αναλύουμε στη συνέχεια, το αποτέλεσμα των καμπυλων του φωτος για τις διελευσεις των (distinctive signatures) πλανητων Το 2000, PSI συμμετείχε σε μια κοινοπραξία ινστιτουτων υπεύθυνο για ανακαίνιση του 1,3 m (50-inch) RCT τηλεσκόπιο του Kitt Peak για να χρησιμοποιήθειι ως πλήρως ρομποτικό αστεροσκοπείο. Ο κύριος στόχος αυτού του τηλεσκοπίου για δύο από τους εταίρους, Δυτικο Kentucky University και PSI, θα πρέπει να προβεί σε εμπεριστατωμένη έρευνα για επιπλέον-ηλιακων πλανήτων. Πρωτοτυπο The search for extra-solar planet transits at the Planetary Science Institute (PSI) seeks to detect new planets as they transit their parent stars. To find transiting planets, we survey, using high-precision differential CCD photometry, a large number of stars repeatedly for many nights. We then analyze the resulting light curves for the distinctive signatures of planetary transits. In 2000, PSI joined a consortium of insititutions responsible for refurbishing the 1.3-m (50-inch) RCT telescope on Kitt Peak to use as a fully robotic observatory. A major goal of this telescope for two of the partners, Western Kentucky University and PSI, will be to undertake a detailed search for extra-solar planets. Working with observations made at national facility telescopes and collaborations with the Kepler project, the RCT extra-solar planet search program will provide a very large database of ultra-precise photometric information on many types of stellar variability, stellar populations, and extra-solar planetary system candidates. Since the discovery of the first planet around 51 Pegasi, there has been an increased interest in the search for extra-solar planets. The links below will give you a brief overview of other, commonly used search methods, details of our method of choice (the transit method), as well as additional project background. Each of these sections will give you a little more information on the science behind the project, in terms that are easy to understand. * Basics of Planetary Transits http://www.psi.edu/esp/process.html * High Photometric Precision http://www.psi.edu/esp/precision.html * Resultshttp://www.psi.edu/esp/results.html * The RCT Telescope http://www.psi.edu/esp/rct.html * Other Search Methods http://www.psi.edu/esp/method.html You can click on an individual topic above, or can view the set in order by beginning with "Other Search Methods" and following the links at the end of each page. http://www.psi.edu/esp/ Λοιπη η μεταφραση, το ξερω Μολις, την τελειωσω θα την βαλω

Ναι.... Εγω, ελεγα οτι μου αρεσει η αστρονομια, γιατι θα μπορω να βλεπω ωραιες φωτογραφιες. Και εκει ειναι που προβλιματιζουμε. Μπορω??? Ελπιζω ναι. Μολις παρω την πρωτη εμπειρια, θα το διαπιστωσω

1) ..... Ο.Κ. Τελευταια φορα, πρεπει να το συνηθισω 2) Δεν εχω προβλημα να κανω μεταφραση. Εσεις θα εχετε XoXo 3) Εκει ειναι η τεχνη. Βαζω κατι που δεν καταλαβαινετε , για να το διαβασετε, ΧιΧι (Πλακα κανω)

Γεια. Χθες, σκεφτηκα οτι περισσοτερη σημασια οφειλει να δωσει καποιος στην αστροφυσικη, παρα στην αστρονομια. Το λεω αυτο γιατι, οταν καποιος εχει ερασιτεχνικο εξοπλισμο, δεν μπορει να κερδισει παρα πολλα παρατηρωντας τα αστρα, καθως εκτος μερικων φαινομαινων( διπλων αστερων, σμηνο γαλαξιων κτλ) δεν μπορει να δει καμια διαφορα , καθως δεν υπαρχει μεγαλη μεγενθυση, ή χρωμα.Αρα η ενημερωση των γεγονωτων και ιη παρακολουθηση των φωτογραφιών, ειναι επαρκης. Υγ Το λεω αυτο, χωρις να εχω κανει ποτε μου αστρο- πλανητο- παρατηρηση

The James Webb Space Telescope (JWST) will be a large infrared telescope with a 6.5-meter primary mirror. Launch is planned for 2014. JWST will be the premier observatory of the next decade, serving thousands of astronomers worldwide. It will study every phase in the history of our Universe, ranging from the first luminous glows after the Big Bang, to the formation of solar systems capable of supporting life on planets like Earth, to the evolution of our own Solar System. JWST was formerly known as the "Next Generation Space Telescope" (NGST). JWST was renamed in Sept. 2002 after a former NASA administrator, James Webb. JWST JWST is an international collaboration between NASA, the European Space Agency (ESA), and the Canadian Space Agency (CSA). The NASA Goddard Space Flight Center is managing the development effort. The prime contractor is Northrop Grumman; the Space Telescope Science Institute will operate JWST after launch. Several innovative technologies have been developed for JWST. These include a folding, segmented primary mirror, adjusted to shape after launch; ultra-lightweight beryllium optics; detectors able to record extremely weak signals, microshutters that enable programmable object selection for the spectrograph; and a cryocooler for cooling the mid-IR detectors to 7K. The long-lead items, such as the beryllium mirror segments and science instruments, are under construction. All mission enabling technologies were demonstrated by January 2007. In July 2008 NASA confirmed the JWST project to proceed into its implementation phase, and the project is currently on track to conduct its next major mission review in March 2010. There will be four science instruments on JWST: a near-infrared (IR) camera, a near-IR multi-object spectrograph, a mid-IR instrument, and a tunable filter imager. JWST's instruments will be designed to work primarily in the infrared range of the electromagnetic spectrum, with some capability in the visible range. It will be sensitive to light from 0.6 to 27 micrometers in wavelength. JWST has four main science themes: The End of the Dark Ages: First Light and Reionization, The Assembly of Galaxies, The Birth of Stars and Protoplanetary Systems, and Planetary Systems and the Origins of Life.

APPPP, δεν μπορεις να με κατηγορισεις για αυτο. Εγω εγραφα αποψεις - αποριες Και μου ηρθε μνμ, πως καλυτερα να διαβαζω γτ δεν ξερω ακομη πολλα Αλλα αφου θελετε να γραφω και εγω οκ Θα δειτε στην συνεχεια αν θα εξακολουθειτε να τ οπιστευετε αυτο Εμ, ναι, αλλα δεν ξερω εχω μπλεχτε. Στην αρχη νομιζα οτι το Cygnusx-3ηταν αστερι το οποιο ειχε κανει συστεμ με ενα αστερι νετρονιου ή μια μαυρη τρυπα Αλλα τωρα βλεπω οτι περιεχει Γαμμα Τα χω χαμενα

http://www.astronomynow.com/news/n0911/27mquasar/ NASA’s Fermi Gamma-ray Space Telescope has made the first clear detection of high-energy gamma-rays from the enigmatic binary system Cygnus X-3. The system pairs a hot, massive star with a compact object, thought either to be a neutron star or a black hole, that blasts twin radio-emitting jets of matter into space at more than half the speed of light. This system, known as a microquasar, has characteristic strong emission across a broad range of wavelengths, rapid brightness changes, and radio jets. It resembles miniature versions of distant quasars and blazars whose emissions are thought to be powered by enormous black holes. “Cygnus X-3 is a genuine microquasar and it’s the first for which we can prove high-energy gamma-ray emission,” says Stephane Corbel of Paris Diderot University in France. A Wolf-Rayet star 17 times hotter than our Sun lies at the centre of Cygnus X-3. It is so hot that its mass wastes into space in a strong stellar wind. “In just 100,000 years, this fast, dense wind removes as much mass from the Wolf-Rayet star as our Sun contains,” says Robin Corbet of the University of Maryland. This star has a compact companion embedded in a disc of hot gas that spins around its sibling every 4.8 hours. “This object is most likely a black hole, but we can’t yet rule out a neutron star,” says Corbet. The new observations were made with the Large Area Telescope (LAT) aboard Fermi, which detected changes in Cygnus X-3’s gamma-ray output that relate to the companion’s 4.8-hour orbital motion, with the brightest gamma-ray emission occurring when the disc is on the far side of its orbit. “This suggests that the gamma rays arise from interactions between rapidly moving electrons above and below the disc and the star’s ultraviolet light,” says Corbel. When ultraviolet photons strike particles moving at an appreciable fraction of the speed of light, the photons gain energy and become gamma rays. “The process works best when an energetic electron already heading toward Earth suffers a head-on collision with an ultraviolet photon,” explains Guillaume Dubus from the Laboratory for Astrophysics in Grenoble, France. “And this occurs most often when the disc is on the far side of its orbit.” Through processes not fully understood, some of the gas falling toward Cygnus X-3’s compact object instead rushes outward in a pair of narrow, oppositely directed jets – radio observations found the gas within these jets to be moving at more than half the speed of light. Between 11 October and 20 December 2008, and between 8 June and 2 August 2009, Cygnus X-3 was found to be unusually active, and the outbursts in the gamma-ray emission was found to precede flaring in the radio jet by roughly five days, strongly suggesting a relationship between the two. The findings, published today in the online edition of Science, will provide new insight into how high-energy particles become accelerated and how they move through the jets.

Astronomers today announced a significant advance in solving the long mystery of Epsilon Aurigae, an enigmatic star that, every 27.1 years, loses half its light for almost two years. The star has mystified astronomers for nearly two centuries despite the fact that it’s easily visible to the naked eye and has been intensively observed by professional and amateur astronomers for decades. Epsilon Aurigae model In this artist's concept, Epsilon Aurigae (the supergiant star at right) is starting to be eclipsed by the dust disk circling a single, much dimmer B star. A new model explains the decades-old paradoxes of this system by assuming that its stars are relatively old, not young. At the American Astronomical Society meeting in Washington, DC, Donald Hoard of Caltech described recent infrared observations from NASA’s Spitzer Space Telescope and a new model that apparently, for the first time, fully ties together the mountains of available data. “What our result has provided is a big-picture solution,” said Hoard. But he was quick to add, “There are still a lot of details that need to be worked out.” Prior to the most recent dimming, which began in August 2009, astronomers had built up a picture of the system in which the visible star, a type-F supergiant, is much more massive than the Sun. That's what its extreme luminosity (130,000 times the Sun's brightness) would suggest. Every 27.1 years, a huge dusty disk seen almost edge-on slides across the face of the star, producing the long-lasting partial eclipse. But big questions remained about the nature of the bright star, the eclipsing disk, and especially the unseen massive object or objects that must occupy the disk's center (Sky & Telescope, May 2009, page 58). The Spitzer observations, combined with many observations at visible and ultraviolet wavelengths, provide a more complete picture of the system. The Spitzer work conclusively reveals the presence of a disk about 8 astronomical units in diameter, as expected, and also shows that it consists of relatively large particles mostly the size of sand grains, not the usual microscopically fine space dust. Far-ultraviolet observations also indicate the presence of a smaller, very hot star at the center of the disk, probably spectral type B (about three times hotter than the Sun). The problem with this model has been that the disk's central object seems to have about the same mass as the F supergiant, and if it's a normal star with such a high mass, it should shine about equally bright. But we hardly see it at all — even though the center of the disk seems to be clear. Epsilon Aurigae is at the center of the sky area in this moonlit Himalayan scene by Babak A. Tafreshi. The peak of Mount Everest is just to the lower right of bright Capella. Babak A. Tafreshi Hoard and his colleagues have proposed a model they say fits all the observations. The key part is that the bright F supergiant is much less massive than previously thought. It could still shine so powerfully if it is very far evolved and nearing the end of its life. In this scenario it started off with around 10 solar masses (as opposed to the 15 or 20 usually assumed for it) and has since blown off much of even that. The companion B star is then allowed to have only about 6 solar masses, and therefore shines much dimmer. In this scenario, the dark disk is not the sign of a newborn star still gathering material. The disk instead is made of material that the B star gravitationally captured from the dying primary star's wind. The disk currently contains much less than an Earth mass, but it probably began with much more. Its original gas and microscopic dust grains have been blown out of the system, leaving only the larger grains behind. The system itself is probably about 10 million years old. Over the next thousands of years, the dying F star will puff off most of its remaining mass to form a planetary nebula. “All of these intertwined parameters just sort of work out,” says Hoard, who adds that he previously favored another model. “I’m a convert to this model, but I am very comfortable with it.” Arne Henden, director of the American Association of Variable Star Observers, emphasizes that the mystery of Epsilon Aurigae has not yet been solved. “We’re nearing the middle of the eclipse, and lots of interesting things will happen over the next year. There are still things about this system we don’t understand.” Hoard and Henden both point out that the AAVSO has organized a global network of “citizen scientists” to monitor Espilon Aurigae’s changing brightness and spectrum. The massive amount of information from high-quality amateur observations (photometry and spectroscopy), as well as continued professional observations, should finally solve the mystery of Epsilon Aurigae. “If there is any time we will understand this system, it’s with this current round of observations,” says Henden. PHGHhttp://www.skyandtelescope.com/

Mαλλον λιγο δυσκολο.... Ask an Astrophysicist The Question (Submitted May 21, 1998) Is there a possibility that a nearby star could go supernova and destroy the earth? Or have other bad effects on us? The Answer To destroy the Earth itself, the Sun will have to go supernova (which it never will). If you are talking about the life on Earth, then there is a detailed calculation of the risks due to a nearby supernova on the web: http://stupendous.rit.edu/richmond/answers/snrisks.txt The author concludes that a supernova has to be within 10 parsecs (30 light years) or so to be dangerous to life on Earth. This is because the atmosphere shields us from most dangerous radiations. Astronauts in orbit may be in danger if a supernova is within 1000 parsecs or so. No stars currently within 20 parsecs will go supernova within the next few million years. There are some indirect effects, though, which are harder to evaluate: the possible effects on the Earth ozone layer is listed in the article above. Additionally, according to one calculation, the neutrino flux from a nearby supernova might heat up the Sun. Best wishes, Koji Mukai & Eric Christian for Ask an Astrophysicist http://imagine.gsfc.nasa.gov/docs/ask_astro/answers/980521a.html

??? Ma to exo ksanapei auti einai i pigi mou , mono auto to sait vlepo tha to grafo kathe fora Ante lipon na to ksanagrapso http://www.astronomynow.com/ Den me noiazi na diaforeoioume kai siga tin diaforopoiisi Telospanton Kalinixta , Kai xronia sou polla , oti epithimis kiolas Yy Terastio tileskopio ,mpravo sou Yy* Den exo diavasei kanones Afou se ola ta forum ta idia lene

An exoplanet only four times the mass of Earth – the second smallest planet in the exoplanet inventory – has been discovered by astronomers using the Keck Observatory in Hawaii. “This is quite a remarkable discovery,” says astronomer Andrew Howard of the University of California at Berkeley. “It shows that we can push down and find smaller and smaller planets.” The announcement was made at the American Astronomical Society meeting held this week in Washington DC. The planet, known to astronomers as HD156668b, speeds around its parent star in just over four days, and was detected using the radial velocity technique. This relies on Keck’s High Resolution Echelle Spectrograph on the ten-metre telescope, which records the star's spectrum such that as the planet heads away from us towards the star its spectrum shifts towards redder wavelengths; when it moves towards the Earth the spectrum shifts to bluer wavelengths. By looking at the colour shifts in the spectrum astronomers can determine characteristics of the planet, like its mass – just four times the mass of Earth in the case of HD156668b. Many of the 400 exoplanets discovered to date are Jupiter-mass planets. “It’s been astronomers long-standing goal to find low mass planets, but they are really hard to detect,” says Howard. “There are important pieces, we don’t have yet. We need to understand how low mass planets, like super-Earths, form and migrate.” The discovery will contribute to studies of how planets and planetary systems form and evolve. HD156668b is located approximately 80 light years from Earth in the direction of the constellation Hercules. The discovery was made as part of the Eta-Earth Survey for Low Mass Planets, which has so far uncovered two near-Earth planets.

Το εχω ειδη πει στο Sn2007bi Και εχω πει απο που ενημερωνομαι ΧιΧιΧιΧιΧι Ειδου η αποδειξη http://www.astrovox.gr/forum/viewtopic.php?t=11306

Δεν δινω τις πηγες μου

NASA's infrared sky-mapping telescope has snapped its first image of the cosmos three weeks after launch, confirming the spacecraft's sensitive detectors are ready to create an atlas of the Universe. "I think the most important event in the life of a telescope is the first light," said William Irace, the Wide-field Infrared Survey Explorer project manager at the Jet Propulsion Laboratory. WISE launched from a California military base Dec. 14 and jettisoned the telescope's dust cover two weeks later. The image released by NASA on Wednesday shows a region in the constellation Carina containing about 3,000 stars, including a relatively bright swelling red giant star, according to David Leisawitz, WISE mission scientist at the Goddard Space Flight Center. WISE glimpsed cool interstellar dust glowing in infared light on the left side of the picture, proving the $320 million mission can accomplish what it set out to do -- map the infrared Universe and detect countless new galaxies, stars and asteroids. "Our sky is filled with such stuff, and WISE will see that in plentiful amounts," Leisawitz said. The first light image was taken in an 8.8-second exposure, part of an engineering test to verify the 16-inch telescope and four detectors work properly. "We are definitely in focus," Irace said. WISE will repeat the process 7,500 times each day during its primary mission. "This is a snapshot of the sky taken with WISE," Leisawitz said. "Over the course of its mission, it will take literally millions of these snapshots to complete a survey of the entire sky. Each one of those little snapshots is about three times the size, in area, of the moon." The satellite will take pictures every 11 seconds, scanning the entire sky at least one-and-a-half times by October, when the craft's reservoir of super-cold solid hydrogen is expected to run out. WISE needs the hydrogen to cool its detectors enough to permit the telescope to see some of the coldest objects in the Universe. The survey phase of the mission will begin in a couple of weeks. Officials are now working to match the motions of the spacecraft and the scan mirror to create "freeze-frame" images. "WISE is now poised to deliver on its promise to measure hundreds of millions of stars, hundreds of millions of galaxies, and hundreds of thousands of solar system objects, such as asteroids," Leisawitz said. The mission's final results won't be available to the public until March 2012, but scientists will unveil selected images beginning next month.

Dusty debris found around planetary embryos in a 500 light year distant system by astronomers using the Gemini South telescope bears no resemblance to the planetary building blocks of our own Solar System. The dusty debris around the star HD 131488 is thought to have formed from colliding planetary embryos. “Until now, warm dust found around other stars has been very similar in composition to asteroidal or cometary material in our Solar System,” says lead researcher Carl Melis, who presented the results at the American Astronomical Society meeting in Washington yesterday. “This newly discovered dusty star is a compelling exception.” Warm dust is present close to the star out to a distance comparable to the Earth-Sun separation (a region known as the terrestrial planet zone), while cold dust resides out to about 45 times that distance, analogous to the Kuiper Belt in our Solar System. The type of dust, however, is currently unknown. “Typically, dust debris around other stars, or our own Sun, is of the olivine, pyroxene, or silica variety, minerals commonly found on Earth,” says Melis. “The material orbiting HD 131488 is not one of these dust types. We have yet to identify what species it is – it really appears to be a completely alien type of dust.” The quantity of warm dust is unusually large, say the astronomers, who propose that the most likely explanation is a recent collision of two rocky bodies. This would also provide a source for the dust particles. The distal cold dust, on the other hand, is most probably left over from planet formation that took place further away from the sun. “Although dusty telltales of planetary formation processes in the outer regions surrounding young stars have often been seen with infrared-sensitive space telescopes, for some reason stars that have large amounts of orbiting warm dust do not also show evidence for the presence of cold dust,” says Benjamin Zuckerman. “HD 131488 dramatically breaks this pattern.” The star joins five other systems bearing suns a few times more massive than our Sun that also show evidence of dust in their terrestrial planet zone. But this is five out of thousands of intermediate mass stars – why are these warm dust rings apparently rare? The astronomers note that all five of these stars have ages in the range of 10-30 million years, suggesting that catastrophic collisions – like the one that resulted in the formation of the Moon in our own Solar System – occurred in this narrow age range for stars of this mass. Further study of HD 131488 and of other similar systems is planned by the team. The infrared imaging and spectroscopic observations in this study were conducted using the T-ReCS instrument on the Gemini South telescope located in Chile. Other observations were made using the Infrared Astronomical Satellite (IRAS) space-based infrared observatory, the NASA Infrared Telescope Facility (IRTF), and the Keck II telescope and optical observations from the Keck I telescope, the Siding Spring Observatory (SSO) 2.3-metre telescope, and the Tycho space-based imager/astrometer that flew aboard the ESA Hipparcos mission.

Δεν καταλβαινω. Ενας αστερισμος μπορει να ειναι ορατος απο μια αποσταση Χ αλλα ενας αλλος μπορει να μην ειναι απο την ιδια αποσταση. Αφου παιζει ρολο και το ποσο φωτιζουν τα αστρα. Ή Λεω μπουρδες?

An unprecedented haul of 17 cosmic whirling dervishes – pulsars that spin thousands of times per second – is providing a boost for research into these extraordinary objects, and may even be the key to detecting something even more extraordinary: gravitational waves. The 17 millisecond pulsars have been found courtesy of NASA’s Fermi Space Telescope, which observes gamma-ray radiation from particles that have been accelerated in the powerful magnetic fields belonging to the pulsars. Fermi identifies them as unknown high energy sources, which are then followed up on by radio telescopes on Earth. The first millisecond pulsar was discovered in 1982, and between then and Fermi’s latest findings, only 60 had been discovered in the Milky Way. Locations of the new millisecond pulsars. “Locating them with all-sky radio surveys requires immense time an effort, and we’ve only found a total of about 60 in the disc of our galaxy since then,” says Paul Ray of the Naval Research Lab in Washington, DC. “Fermi points us to specific targets. It is like having a treasure map.” Pulsars are spinning neutron stars, which are the remains of a massive star that has exploded as a supernova. As they spin, beams of radio waves emanating flash in our direction, causing them to appear to pulse, hence their name. Neutron stars are born spinning, but over time they slow down. However, those located in a binary system with another star can find themselves rejuvenated. In these circumstances, the gravity of the extremely dense neutron star can strip gas from its companion, and this process sees the pulsar spun up, a bit like a spinning top, to the point that it spins thousands of times per second (for more on millisecond pulsars see our recent news story here)**. This helping hand from the companion star is not always reciprocated. Four of the 17 new pulsars are known as black widow pulsars, because their radiation is eating away at the very companion star that span them up in the first place, to the point that the companions have been whittled down to just a few dozen times the mass of the planet Jupiter. For us on Earth, they may provide surprising benefits. Pulsars ‘pulse’ with incredible regularity – they are the most precise time-keepers in the Universe. Suppose an elusive gravitational wave, perhaps created by a black hole or neutron star merger, passed this way; any disruption in the pulsing signals from a group of precisely measured millisecond pulsars caused by the gravitational wave would be a dead giveaway. *ΤΟ ΣΑΙΤ ΕΧΕΙ ΚΑΙ ΕΝΑ ΛΙΝΚ ΓΙΑ ΕΝΑ ΒΙΝΤΕΑΚΙ ΤΙΣ ΝΑΣΑ(Μπορειτε να το βρειτε εδω, κατω κατω:http://www.astronomynow.com/news/n1001/06pulsars/) **Ο υπερσυνδεσαμος οδηγει σε αυτο το κειμενο http://www.astronomynow.com/090522Millisecondpulsarmysterysolved.html Astronomers have watched a pulsar be spun up in real time by its companion star, turning it into an incredibly fast millisecond pulsar rotating at a breakneck 592 times per second. This is the first time we have ever seen the process by which millisecond pulsars are created, confirming our suspicions that a river of matter from the companion star onto the pulsar is to blame. An artist's impression of a pulsar being spun up by an accretion disc. Image: NASA/Dana Berry. Pulsars are spinning neutron stars, the remnants of massive stars that have exploded as supernovae. They’re born spinning a few tens of times a second, firing out beams of radio and X-rays that flash, or pulse, in our direction every rotation. As time goes by they slow down, but the existence of older pulsars that are spinning faster than any others has always been a puzzle. The new observations made over the course of a decade have put an end to the mystery. The pulsar was discovered in 2007 by the Green Bank Telescope in West Virginia, USA, but upon closer inspection it was realised that the same star system had been imaged on several occasions previously, first in 1998 by the Very Large Array and then as what appeared to be a Sun-like star by the Sloan Digital Sky Survey in 1999. A year later, it was seen sporting an accretion disc – a spiralling disc of gas torn from the body of a star, but when astronomers went back two years later, the disc had vanished. Now it appears to be a millisecond pulsar. What was going on? The theory was that millisecond pulsars are spun up by gas wrapping around it from a companion star, like a spinning top. During the process of accreting the gas radio waves cannot be seen coming from the pulsar, but once the gas disappears the radio waves from the beams emerge. The fastest millisecond pulsar ever seen spins 1,112 times per second. One of the intermediary steps before becoming a millisecond pulsar is that of a low-mass X-ray binary, which are systems usual involving a neutron star and some other small star. The companion of J1023 – the pulsar in question – is only half the mass of the Sun. “Low mass X-ray binaries… don’t emit radio waves,” says Anne Archibald, of the McGill University in Montreal, Canada. “We’ve thought that low mass X-ray binaries probably are in the process of getting spun up, and will later emit radio waves as a pulsar.” “It appears this thing has flipped from looking like a low mass X-ray binary to looking like a pulsar,” adds Scott Ransom of the National Radio Astronomy Observatory in the United States. This is the first time an accretion disc has ever been seen involved with a millisecond pulsar, and the sheer rapidity of the process explains why we’ve always missed it before. It is now hoped that J1023 will become a kind of Rosetta Stone for millisecond pulsars. The research is published in the 21 May edition of the journal Science. ΑΝ ΜΠΟΡΟΥΣΕ ΚΑΠΟΙΟΣ ΝΑ ΜΟΥ ΠΕΙ ΤΙ ΛΕΕΙ ΘΑ ΤΟΥ ΗΜΟΥΝ ΕΥΓΝΟΜΩΝ

κΑΛΗΣΠΕΡΑ Απο εδω ενημερωνομαι http://www.astronomynow.com/ Και εδω ειναι το αρθρο http://www.astronomynow.com/news/n0912/04sn/

A white dwarf star that will one day explode in a giant thermonuclear explosion has been discovered to be alarmingly close to our Solar System. Fortunately it’s not due to explode for another million years, but if it did it would fry every living thing on Earth, and eradicate the ozone layer. An artist’s impression of a binary system with a white dwarf harvesting gas from a companion star, which forms a disc around the white dwarf. Image: ESO/L Calçada. The white dwarf is found in the binary system T Pyxidis, in the Southern Hemisphere constellation of Pyxis, along with a fairly normal Sun-like companion star. The white dwarf – the burnt out remains of an ancient star – is leeching off its partner, stealing gas from it that consequently builds up on the surface of the white dwarf. Roughly every twenty years, this build up of gas becomes a little too dense and part of the surface explodes in what we call a nova. T Pyxidis was seen going nova in 1890, 1902, 1920, 1944 and 1967, but there has been nothing since, and nobody knows why we are overdue. However, new analysis of spectral observations of the white dwarf made with the now-defunct International Ultraviolet Explorer (IUE) have revealed that it is approaching the time when it will upgrade from a nova to a full blown supernova. This happens when the white dwarf accumulates so much gas that it crosses the Chandrasekhar limit, which is 1.4 times the mass of our Sun, and matter becomes so dense within the star that a thermonuclear explosion engulfs the star, utterly destroying it. The IUE data implies that it is close to this limit, and is continuing to collect more gas from its companion at a rate of 200 trillion kilograms per second. Furthermore, the observations answer a long-standing puzzle; do the recurrent nova rid the white dwarf of all its extra mass, meaning it has to start over again after each eruption, or does it have some left over after each nova? The observations conclusively show that the white dwarf doesn’t shed all its extra mass with each eruption, so over time it is gaining mass, thus explaining how it can build up to the Chandrasekhar limit. There is a caveat to all this. The new analysis of the data also places this doomsday star within 1,000 parsecs (3,260 light years) of Earth. White dwarf supernovae are among the most powerful supernovae in the Universe, and at this range the radiation from the explosion would fry everything on our planet, subjecting the surface to 100,000 ergs per square centimetre, and eradicating our protective ozone layer. (In contrast Betelgeuse, the red supergiant star in Orion due to blow up as a type II supernova, will be less powerful and no risk to life on Earth, even though it is only 640 light years away) Fortunately, we have about a million years before we have to worry about that; let’s hope that our motion through the Galaxy has moved us out of firing range by then.

An extraordinarily bright and long-lasting supernova represents one of the first examples of the population of stars that first sprung into life in the early Universe Known as SN2007bi, this supernova occurred in a nearby dwarf galaxy and was discovered by the international Nearby Supernova Factory (SNfactory) based at the U.S. Department of Energy’s Lawrence Berkeley National Laboratory. The supernova's unusual spectrum caught the astronomers' attention and over the last year and a half they have attained even more data as the supernova slowly faded away. ''ΜΤΦΡ(Ελπιζω να ειναι καλη)'' Μια εξαιρετικά φωτεινή και μακράς διαρκείας σουπερνόβα αντιπροσωπεύει ενα από τα πρώτα παραδείγματα του πληθυσμού των αστεριών που πρώτα αναπηδήσαν στη ζωή (?) Γνωστο ως ΣΝ2007Bi αυτη η σουπερνοβα εμφανιζστηκε σε εναν κοντινο''νανο''γαλαξια και ανακαλυφθηκε απο την διεθνη SNFactory βασιζομενη στην U.S. Department of Energy’s Lawrence Berkeley National Laboratory. Το ασυνηθιστο φασμα της σουπερνοβα, προσελκισε την προσοχη των αστρονομων και κατα την διαρκεια του τελευταιου χρονου και μισο πετυχε να βρει περισσοτερα στοιχεια της σουπερνοβα που εξασθενησε αργα μακρια Και αλλα In this schematic illustration of the material ejected from SN 2007bi, the radioactive nickel core (white) decays to cobalt, emitting gamma rays and positrons that excite surrounding layers (textured yellow) rich in heavy elements like iron. The outer layers (dark shadow) are lighter elements such as oxygen and carbon, where any helium must reside, which remain unilluminated and do not contribute to the visible spectrum. The analysis indicated that the supernova’s progenitor star could only have been a massive star weighing at least 200 times the mass of our Sun and initially containing few elements besides hydrogen and helium, very much like the first stellar inhabitants of the Universe. “Because the core alone was some 100 solar masses, the long-hypothesized phenomenon called pair instability must have occurred,” says astrophysicist Peter Nugent. “In the extreme heat of the star’s interior, energetic gamma rays created pairs of electrons and positrons, which bled off the pressure that sustained the core against collapse.” Instead of turning into a black hole like many other heavyweight stars, its core went through a nuclear runaway that blew it to shreds. This type of behavior has been predicted, but this is the first convincing observation of the process in action. The SNfactory has already discovered nearly a thousand Type Ia supernovae – the 'standard candles' used to study the expansion history of the Universe – but SN 2007bi was at least ten times as bright, and is thought to represent the first confirmed observation of a pair-instability supernova. “The thermonuclear runaway experienced by the core of SN 2007bi is reminiscent of that seen in the explosions of white dwarfs as Type Ia supernovae,” says Alex Filippenko, “but on a much larger scale and with a far greater amount of power.” Follow up observations were made with the Keck telescope and the Very Large Telescope (VLT) in Chile as SN 2007bi slowly faded over the course of 555 days. “The Keck and VLT spectra clearly indicated that an extremely large amount of material was ejected by the explosion, including a record amount of radioactive nickel, which caused the expanding gases to glow very brightly,” says Paolo Mazzali from the Max Planck Institute for Astrophysics in Garching, Germany. Computer simulations were composed to try and replicate the properties observed in this supernova explosion. Rollin Thomas of Berkeley's Computational Research Division aided the early analysis, using the Franklin supercomputer at the National Energy Research Scientific Computing Center (NERSC). “The code uses hundreds of cores to systematically test a large number of simplified model supernovae, searching through the candidates by adjusting parameters until it finds a good fit,” he says. “This kind of data-driven approach is key to helping us understand new types of transients for which no reliable theoretical predictions yet exist.” The model fit was unambiguous: SN 2007bi was a pair-instability supernova. “The central part of the huge star had fused to oxygen near the end of its life, and was very hot,” Filippenko explains. “Then the most energetic photons of light turned into electron-positron pairs, robbing the core of pressure and causing it to collapse. This led to a nuclear runaway explosion that created a large amount of radioactive nickel, whose decay energized the ejected gas and kept the supernova visible for a long time.” The team say that it is significant to have found the first unambiguous example of a pair-instability supernova in a dwarf galaxy because they are so faint and contain few elements heavier than hydrogen and helium, but this makes them ideal "fossil laboratories" to study the early Universe. “In the future, we might end up detecting the very first generation of stars, early in the history of the Universe, through explosions such as that of SN 2007bi – long before we have the capability of directly seeing the pre-explosion stars,” adds Filippenko. The researchers discuss their results in the 3 December 2009 issue of Nature. [/i]

Γιατι βρε παιδια ειναι ακριβο\ 200 Ευρω ενα τηλεσκοπιο χαρτεσ προγραμματα, ολα τσαμπα τι τρεχει?? αν γινετε επειδη ειμαι νεος ασ μου εξηγησει καποιος