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{tab= Comet Holmes brightened}
Comet Holmes brightened...
Comet Holmes (17P) has suddenly brightened million-fold and reached a magnitude of about 2.5. Brightening of the comet may be due to exposed interiors of the core of the comet. Core has a diameter of about 3.4 km. Comet is now at a distance of 365 million km from Sun and 245 million km from Earth. This tailless comet can be spotted even in moonlight. It appears as yellowish star to naked eyes. Hazy nature of its coma can be easiliy discerned with binoculars. Diameter of the coma is about 1.5 arc minutes. (Present position of the comet is shown in the map under 'Comet Watch'.)
Discovery: November 6, 1892 by Edwin Holmes (England) in Androemeda constellation
Orbital period of the comet: 6.88 years
Last perihelion date: May 4, 2007
Semi-major axis: 3.62 AU
Perihelion distance: 2.05 AU
Eccentricity: 0.4324
Inclination: 19.11º
(Source: MPC 51822)
(Credit: Khagol Mandal)
{tab= Return of the Comet}
Return of the Comet!
Periodic reappearane of the same comet is not a novelty to astronomers. Since Edmond Halley's days, nearly 190 comets have been identified as periodic. But for Solar and Heliospheric Observatory (SOHO), the discovery of a periodic comet has proved to be historic. SOHO is keeping continuous watch on Sun from the space since 1995. While watching activity on the solar surface, it is keeping track of various comets coming close to Sun. At present, it has discovery of more than 1350 comets to its credit. But So far, none of these comets were known to be periodic. This want is now fulfilled.
SOHO's discovery
(Credit: NASA)
Peridic nature of one of the comets, discovered by SOHO, was noticed by German Ph.D. student Sebastian Hönig. He realized that comets spotted by SOHO in September 1999 and September 2003 are the same. He predicted that this comet will again return in September 2007. And it did so! This comet is now officially known as P/2007 R5 (SOHO). It is a small comet with a diameter of about 100 to 200 meters. It brightened by about million times when it passed within 7.9 million km of Sun. (This is about one-seventh of Mercury-Sun distance.) Astronomers are expecting the comet again to be seen in September 2011.
{tab= Chinese Magic}
Chinese Magic...
Chinese astronomers of the ancient and medieval times were known for their exceptional skills in observational astronomy. Modern Chinese astronomers are also ready to take a giant leap in the field of observational astronomy. This will be accomplished through a state-of-the-art 4 meter spectroscopic telescope being installed at Xinglong Observation Station situated in the mountains of Yanshan, 180 km North of Beijing. This 'Large Sky Area Multi-Object Fiber Spectroscopic Telescope' (LAMOST) has a focal length of 20 meters and an angular field of view of 5 degrees. This telescope will take spectra of celestial objects with a magnitude upto 20.5. It will be able to view more than ten million celestial objects spectroscopically, almost doubling the existing achievable figure.
But most noteworthy fact is that this Chinese instrument will acquire spectra of 4000 objects simultaneously. With its capability of covering several thousand objects spectroscopically in a single night, this equipment is going to be the fastest of its kind in the world. LAMOST is expected to be fully operational by August 2008.
{tab= Neptunian mystery solved}
Neptunian mystery solved?
Whether it be summer or winter, temperatures on polar regions of our mother planet will always be subnormal. Interestingly, that is not the case with distant planets. Recently published temperature maps of Neptune show that its south pole is hotter at least by 10 degrees Celsius than rest of the planet. Reason for this is very very long summer that Neptune experiences. Length of Neptunian year is 164 years, as it is the time that Neptune takes to complete one revolution around Sun. Consequently, summer on Neptune is decades and decades long! With an axial tilt of 28 degrees, each hemisphere of Neptune remains tilted towards Sun for about 82 years. This almost a century-long leaning of the pole towards the Sun is sufficient to render the pole warmer than the rest of the planet.
But there is another important aspect to this observation! Analysis of these thermal profiles have probably solved a longstanding mystery regarding methane on Neptune. Average temperature of the upper atmosphere of Neptune is as low as -200 degrees Celsius. Why does then methane show its presence in the upper atmosphere of Neptune, which otherwise should have remained cold-trapped in the lower atmosphere? (In fact, it is well known that methane is responsible for the blue tinge in the atmosphere of Neptune.) Obviously, it is the warmth of the south pole that allows methane to escape to upper atmosphere. White spots seen on the surface of Neptune appear to be the outlets for this upwelling methane. This prolific thermal mapping was carried out by Glenn Orton of Jet Propulsion Laboratory (USA) and his colleagues using mid-infra red spectrometer on 8.2 meter Very Large Telescope of European Southern Observatory located in Northern Chile.
{tab= Magellanic trespassers}
Magellanic trespassers...
Our Milky Way galaxy has two neighbouring galaxies. These southern neighbours can be easily spotted even by unaided eye. These are named after sixteenth century Portuguese explorer, Ferdinand Magellan, who recorded them as clouds during the first voyage 'around the world'. While larger of these two galaxies (Large Magellanic Cloud) is situated at 160,000 light years from us, smaller one (Small Magellanic Cloud) is 200,000 light years away. These two galaxies were supposed to be satellite galaxies, gravitationally bound to our Milky Way galaxy. However, it seems that these galaxies are mere trespassers.
Magellanic Clouds
Gurtina Besla of Harvard-Smithsonian Center for Astrophysics (USA) and his colleagues have measured velocities of these galaxies in three dimensions with very high accuracy. Results of these studies show that these galaxies are not orbiting our Milky Way galaxy but are following a parabolic path. Nature of the path indicates that these galaxies are visiting our Galaxy first time. They have arrived in the vicinity of our Galaxy one to three billion years ago. Besla further thinks that it is not the interaction between our Galaxy and these clouds that has set off star formation in the later as thought earlier. It is the interaction between the Large Magellanic Cloud and Small Magellanic Cloud itself that has triggered this star formation.
{tab= Remembering Sputnik 1}
Remembering Sputnik 1...
Five decades are over! It was on October 4, 1957 that first artificial satellite - Sputnik 1- started orbiting Earth. It was completing its revolution in about 96 minutes with minimum and maximum distance from Earth surface of 215 km and 939 km, respectively. This Russian-built satellite was a spherical object with a diameter of 58 cm and weighed 84 kg. Signals transmitted by this 'moon' could be heard on household radios for about three weeks. After staying for 3 months in Earth's orbit, it reentered Earth's atmosphere.
Fiftieth anniversary of this launch was commemorated in Russia and in other nations. President Vladimir Putin described the launch as "a truly historic event, which started a space age". Michael Griffin, who heads NASA, admitted that launch of Sputnik 1 was responsible for the creation of the American space programme. With the launch of Sputnik 1, dream of yesteryears, evinced by visionaries like Jules Verne, Robert Goddard, Arthur C. Clarke had turned into reality.
{tab= Rovers resume their duty}
Rovers resume their duty...
NASA's Mars Exploration Rovers, Opportunity and Spirit, have not only survived last month's intense Martian dust storm but have resumed their duty also. Opportunity has started climbing down the steep walls of 70 meters deep Victoria Crater. The steepness that Opportunity has to negotiate is as high as 25 degrees. Opportunity will analyse rock samples at different levels and decipher the secrets of formation of this 800 meter wide distinctive crater. This will throw light on geological aspects of Mars. At the same time, Spirit, is investigating a plateau known as "Home Plate" around Columbia Hills for its volcanic connection in the past.
(Credit: NASA)
{tab= Major suspect}
Major suspect...
Sixty-five million years ago, our mother planet had suffered a severe blow from a giant meteor. The aftermath of the impact was a complete change in the global climate, leading to extinction of dinosaurs. Scientists had been puzzled by the history of this meteor which was supposed to have a diameter as large as 15 km. Now the puzzle seems to be solved. This chunk had its origin in an asteroid Baptista. Some 160 million years ago, Baptista had a collision with some other minor planet. Collsion resulted in shattering of Baptista into several fragments of varied size. (This has reduced the diameter of Baptista from 170 km to today's 40 km.)
While some of the fragments slowly stabilised forming their own orbits, others kept on moving haphzardly in our Solar system. According U.S. and Czech scientists, who are working jointly on this topic, it was one of these roaming fragments that had an encouneter with Earth. According to William Bottke of Southwest Research Institute, one-fifth of the today's near-earth meteors are leftovers of the same collision. Even 85 km wide Tycho crater on Moon has been a result of an impact from one of such fragments.
{tab= Earth-sized telescope}
Earth-sized telescope!
Larger the diameter of the objective of telescope, better is the resolution. Hence, increase in the size of telescope leads to high-quality images. This can be achieved by linking distant telescopes, instead of constructing a single telescope. Scientists have done this successfully with radio telescope facilities existing in Australia, China and Europe. Effective diameter of this telescope is more than 12,000 km, i.e. comparable to the diameter of the Earth. While the radio telescope in Australia is situated at Coonabarabran in New South Wales, Chinese radiotelescope facility is in Shanghai. European facilities are dispersed over five different sites.
{tab= Stars do smoke}
Stars do smoke...
Smoking is injurious to heath! But stars are not aware of this warning. Scientists had a doubt that some of the stars do smoke. And finally, one of such stars had been caught smoking red-handed. RY Sagitarii, a supergiant star 6000 l.y. away from us, is shown to release clouds of carbonaceous dust intermittently. Star then gets slowly shrouded in this dust and loses its brightness. Consequently, magnitude of the star alters from 6 to 14, i.e. lowering of brightnes is nearly 1500 times. Slowly the 'smoke' disperses and the star regains its brightness.
Dust clouds around RY Sagitarii
[Credit: ESO]
This behaviour is common to R Coronae Borealis type variable stars which have a period ranging from several months to a year. This smoking habit of RY Sagitarii was discovered by a team led by de Laverny using European Southern Observatory's Very Large Telescope Interferometer.
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