Jika anda ternampak muka saya tengah TT (Teh Tarik) ni, bermakna anda telah selamat mengharungi 3 hari bumi tak jadi bergelap, dan tarikh 21hb Dis yang penuh tragis dan huru-hara (kononlah).
Nak ceritanya, Falak Online telah pun berpindah rumah. Bermula sekarang silalah kemaskini link ke WWW.FALAKONLINE.NET , tak perlulah letak apa-apa selepas tu, kerana ia akan redirect ke muka hadapan BARU yang sepatutnya.
Laman lama (yang anda lihat sekarang ni), InsyaAllah akan kekal untuk beberapa bulan mendatang. Ia akan menyenaraikan KESEMUA artikel lama saya di FO, bagi rujukan anda semua. Maka, kalau anda nak masih nak marah-marah kat saya berkenaan artikel "3 hari bergelap tu" , masih boleh berbuat demikian, saya terima dengan hati terbuka! :-)
Apa pun, InsyaAllah 2013 mendatang akan terdapat beberapa pembaharuan yang saya dan rakan-rakan Personaliti Astronomi lain usahakan, demi kemajuan bidang Astronomi di Malaysia.
Jom dan Selamat Datang Ke Tahun Baru 2013.
Jemput masuk ---> WWW.FALAKONLINE.NET
Mission planners have devised an unusual strategy for protecting orbiting spacecraft when Comet Siding Spring passes the Red Planet in October.
As Comet C/2013 A1 Siding Spring hurtles toward Mars, NASA is taking steps to protect its Martian orbiters. The plan? Use the planet itself as a shield between the spacecraft and the comet’s potentially dangerous debris.
As part of its long-term Mars Exploration Program, NASA currently has two spacecraft orbiting the Red Planet, Mars Reconnaissance Orbiter (MRO) and Mars Odyssey, with Mars Atmosphere and Volatile Evolution (MAVEN) set to arrive in late September. Teams of scientists at the University of Maryland, the Planetary Science Institute, and NASA’s Jet Propulsion Lab (JPL) have used data from both Earth-based and space telescopes to model Siding Spring’s journey through the inner solar system, and determined that there is no risk of the comet colliding with Mars.
However, at its closest approach to Mars on October 19, 2014, Siding Spring will come within 82,000 miles of the Red Planet, which is about a third of the distance from Earth to the Moon. The closest comets ever to whiz by Earth have been at least ten times more distant.
Such a close encounter means the dust tail left in Siding Spring’s wake might graze Mars’s upper atmosphere. The smallest particles are only about half a millimeter across, but careening through space at 35 miles per second, even these could severely damage a spacecraft. Scientists predict that the time of greatest danger for the orbiters will occur about 90 minutes after Siding Spring’s closest approach, and will last about 20 minutes.
To avoid the threat of Siding Spring’s debris, NASA engineers will manipulate the orbiters’ trajectories so that all three will end up on the opposite side of the planet during the flyby. The MRO team executed one maneuver at the beginning of July, with another planned for the end of August. The Mars Odyssey team took similar steps on August 5th, and the MAVEN team will perform a precautionary maneuver shortly after the spacecraft enters orbit around Mars.An Exercise in Caution
Scientists point out that it’s also possible that Siding Spring’s dust tail will present no threat at all. In June, the University of Maryland issued a press release stating that Siding Spring poses little danger to the orbiters. In the NASA press release that announced plans to move the orbiters, Rich Zurek, chief scientist for the Mars Exploration Program at JPL, affirmed, “Mars will be right at the edge of the debris cloud, so it might encounter some of the particles—or it might not.”
“Although our best prediction is that the most dangerous time is actually not dangerous at all, putting all the spacecraft in this shielded position at that moment is relatively easy, so it makes sense to play it safe,” says Michael Kelley (University of Maryland).
Indeed, the fuel expended to adjust the orbiters’ positions for the flyby is fairly insignificant. Mars Odyssey’s maneuver used about 0.1 kilogram of fuel, leaving the spacecraft with around 16.5 kilograms, which can support another decade of operation. MRO’s two maneuvers will require a total of 0.15 kilogram of fuel, which is similar to the amount used for monthly maintenance maneuvers. MRO carries 254 kilograms of fuel, enough to run for another 25 years.Seizing a Rare Opportunity
Threat of destructive dust particles aside, Siding Spring’s close flyby is a unique opportunity for close-up study of a dynamically new comet— one that will zoom past the Sun for the first time. Since the planets formed, Siding Spring has been chilling in the Oort Cloud, the spherical collection of comets on the outermost fringes of the solar system. As Siding Spring closes in on Mars, it’s bringing with it some of the most ancient material around the Sun. NASA plans to take full advantage of this event by using its Mars orbiters and rovers to study Siding Spring in the days before and after its flyby.
MRO, whose usual mission is studying the history of water on Mars, will observe the gases in Siding Spring’s coma. The MRO team also hopes to get a detailed-enough view of the comet’s nucleus to determine its rotation rate and distinguish some of its surface features. Mars Odyssey will study Siding Spring’s coma and tail and examine their effects on the atmosphere. MAVEN will study the gases streaming off Siding Spring’s nucleus as the Sun warms the dirty iceball, before beginning its investigation of the Martian climate and atmosphere in early November.
The European Space Agency is taking similar precautions to protect its Mars Express (MEX) orbiter. MEX has a highly elliptical orbit that would leave it exposed to Siding Spring's debris longer than MRO or Odyssey. On June 22nd the MEX team altered the orbiter's track around the planet so that it will be hidden behind Mars for 27 minutes during the comet's closest approach.
According to MEX Spacecraft Operations Engineer Andy Johnstone, if observations closer to the comet's arrival show a high risk of impact, then the MEX orbiter will adopt a special attitude that uses its high-gain antenna as a shield and will shut down as many onboard systems as possible. Otherwise, MEX will study the comet and its interactions with Mars.
The Indian Space Research Organisation also will have its Mars Orbiter Mission (MOM) swinging around the Red Planet starting in September, but the agency has not announced any plans yet for special maneuvers to avoid Comet Siding Spring.
Fascinated by the Red Planet? Check out Sky and Telescope's special issue Mars: Mysteries and Marvels of the Red Planet.
A SKY & TELESCOPE PRESS RELEASE
Alan MacRobert, Senior Editor, Sky & Telescope
617-864-7360 x2151, amacrobert@SkyandTelescope.com
Kelly Beatty, Senior Contributing Editor, Sky & Telescope
If you're willing to rise before dawn on Monday, August 18th, you'll be rewarded with the sight of the closest planet pairing of 2014 — and not just any planets, but the two brightest ones: Venus and Jupiter.
On that morning, these two worlds will form a striking "double star" low in the eastern sky. They will appear only 1⁄3° apart — a bit tighter than that in the eastern U.S. — close enough for both to be easily covered by the tip of your little finger at arm's length.
You can start watching for Venus and Jupiter after they've cleared the east-northeastern horizon, as early as 80 minutes before sunrise, but make sure your view in that direction is wide open and unobstructed by trees or buildings. The best views will probably be from 60 to 30 minutes before sunrise, depending on how clear the air is, when the planets will be not quite so low.
As close as this conjunction is for early risers in North America, the pairing will be even tighter for skywatchers in Europe. From there, Venus and Jupiter will appear just 0.2° apart, about half the width of a pencil held at arm's length.A Gradual Approach
The two planets' tight tango develops over several days. Venus is sinking in the predawn twilight, whereas Jupiter has only recently climbed high enough in the sky to be seen before sunrise. On August 15th, they'll be about 3° apart. Each morning thereafter, Jupiter rises a little higher and Venus sinks a little lower. The distance between them shrinks each day until the morning of the 18th, when they'll appear closest together.
After that, they'll gradually separate. By August 23rd, they'll be 5° apart (with Jupiter now higher), and on that date the planet duo will be joined by a razor-thin waning crescent Moon to their right.
Rarely do planets approach each other this closely. While these conjunctions of Venus and Jupiter occur about once a year on average, they vary considerably in visibility and separation. Some happen in daylight, while others are wide misses. These two planets have not paired this tightly while in good view in 15 years. The next Venus-Jupiter conjunction occurs on June 30, 2015, though their separation will not be quite as close.
Around August 18th, Venus will appear six times brighter than Jupiter, even though its diameter (7,521 miles) is less than 1⁄10 that of Jupiter (86,881 miles). That's because Venus is closer to Earth (150 million miles compared to Jupiter's 580 million miles), and also because Venus is much closer to the Sun than Jupiter is, so its clouds are lit much more intensely.The View Up Close
Binoculars will make it easier to spot the two planets, especially as dawn twilight brightens. If your sky is still dark enough, use the binoculars to look for a loose concentration of faint stars (called the Beehive Cluster) positioned just above the paired planets.
Even the smallest backyard telescope will show a dramatic view. Both planets will fit with room to spare in the same low-power telescopic field of view. Blazing Venus mimics a tiny full Moon; Jupiter, appearing three times wider despite its great distance, is accompanied by its four brightest moons, neatly aligned in a row.
For more skywatching information and other astronomy news, visit SkyandTelescope.com or pick up Sky & Telescope, the essential magazine of astronomy since 1941. Sky Publishing (an F+W company) was founded in 1941 by Charles A. Federer Jr. and Helen Spence Federer, the original editors of Sky & Telescope magazine. In addition to Sky & Telescope and SkyandTelescope.com, the company publishes two annuals (Beautiful Universe and SkyWatch), as well as books, star atlases, posters, prints, globes, and other fine astronomy products.
The post Venus and Jupiter: Superclose Conjunction Before Dawn on August 18th appeared first on Sky & Telescope.
Celebrate the anniversary of a revolutionary discovery by gathering with other astronomers to observe planetary nebulae in August's evening sky.
August 29, 2014 will mark the 150th anniversary of Sir William Huggins’s first observation of the spectrum of a planetary nebula. He was the first to split apart the light coming from these stellar death shrouds, using a newfangled instrument he called a star-spectroscope.
These days we’re familiar with the fact that planetary nebulae are large, dusty clouds thrown off by dying stars. But astronomers didn’t know that when Huggins took his first observations. His first peek through the spectroscope was a watershed moment in the history of astronomy, comparable to Galileo’s use of a spyglass to catch his first glimpse of Jupiter’s moons.
Here’s how the London-based amateur astronomer famously described the event more than thirty years after the fact:
On the evening of the 29th of August, 1864, I directed the telescope for the first time to a planetary nebula in Draco [NGC 6543, popularly known today as the Cat’s Eye]. The reader may now be able to picture to himself to some extent the feeling of excited suspense, mingled with a degree of awe, with which, after a few moments of hesitation, I put my eye to the spectroscope. Was I not about to look into a secret place of creation? I looked into the spectroscope. No spectrum such as I expected! A single bright line only! At first, I suspected some displacement of the prism, and that I was looking at a reflection of the illuminated slit from one of its faces. This thought was scarcely more than momentary; then the true interpretation flashed upon me. The light of the nebula was monochromatic, and so, unlike any other light I had as yet subjected to prismatic examination, could not be extended out to form a complete spectrum. . . . The riddle of the nebulae was solved. The answer, which had come to us in the light itself, read: Not an aggregation of stars, but a luminous gas.
[W. Huggins, “The New Astronomy: A Personal Retrospect,” Nineteenth Century, 41 (1897), pp. 916-17.]
Before Huggins’s startling observations of the Cat’s Eye and several other planetary nebulae that August night in 1864 (see list below), astronomers had disagreed on whether these objects were groups of stars too distant to distinguish or diffuse, glowing matter. His spectroscopic results offered astronomers an entirely new — and previously undreamed of — way to answer that nagging question. Astronomers would never look at these perplexing fuzzy little objects in the same way again.
August 29th falls on a Friday this year, just four days after the new Moon. It’s a convenient time to take a look at the Cat’s Eye yourself and commemorate William Huggins’s historic observations.
Better yet, help a local amateur group or observatory organize a public “nebula” party in your area. Many groups appear in Sky & Telescope’s online listings, or you can search the web for other groups in your area. If you can’t find anything nearby, create your own event! You can use Huggins’s list to plan the evening’s agenda.
To learn more about Huggins’s groundbreaking observation and the pivotal role it played in the early development of astrophysics, see chapter 5 (“The Riddle of the Nebulae”) in my book, Unravelling Starlight: William and Margaret Huggins and the Rise of the New Astronomy (Cambridge University Press, 2011).Planetary Nebulae Observed by William Huggins at his Tulse Hill Observatory on August 29, 1864.NGCOther catalog designations
Barbara Becker received her PhD in history of science from The Johns Hopkins University. Until her recent retirement, she taught history of science at the University of California, Irvine. She is the author of Unravelling Starlight: William and Margaret Huggins and the Rise of the New Astronomy (Cambridge University Press, 2011) and editor of the recently completed Selected Correspondence of William Huggins, 2 vols (Pickering and Chatto, 2014).
Want help finding these planetary nebulae and other celestial objects? Look no further than Sky & Telescope's beloved Pocket Sky Atlas.
Here's your invitation to a spectacular close conjunction of the sky's two brightest planets, Venus and Jupiter, next Monday morning.
Planets pair up plenty often in the sky, but rarely do they dance this closely. During Venus and Jupiter's close conjunction shortly before dawn on Monday, August 18th, they'll be separated by only 1⁄3° or less. It's the very best planet-planet meetup of 2014 — in fact, these two worlds haven't paired so closely since 2000.
And it all happens right next door to Messier 44, the Beehive Cluster, in the constellation Cancer the Crab.
The two planets' tight dance will be brief. Venus is headed toward the eastern horizon and solar conjunction, while Jupiter only recently escaped the glare of the sun. With every morning, Jupiter rises a little higher in the east and Venus a little lower. As the two planets trot off in different directions, we'll see them slowly approach and separate.
On August 14th, they'll be just 4° apart some 10° high in the northeastern sky 30 minutes before sunrise. To spot the duo, find a location with an open view nearly down to the eastern horizon.
You can start watching for the Venus-Jupiter conjunction as early as an hour before sunrise, but the planets will be very low and possibly obscured by clouds or haze. Bring along a pair of binoculars just in case. Not sure when the sun rises? Click here and enter your city.
Each following morning, the distance between them shrinks by 1° (twice the diameter of the full Moon) until the 18th, when they'll be about 20 arcminutes (20′) apart, depending where you are in North America. You'll be able to cover both planets with the eraser of a pencil held at arm's length. That's what I call snug!
While conjunctions of Venus and Jupiter occur about once a year on average, they vary considerably in visibility and separation. Some happen in daylight, while others are wide misses.
Proximity makes for exciting conjunctions, and this event is the closest for North America since a similar morning pairing on April 23, 1998, almost an eternity ago. And there's more: The next Jupiter-Venus tango occurs less than a year from now, on June 30th, when they'll be just 20′ apart and conveniently placed in the western evening sky during twilight.The View Through a Telescope
If you own a telescope, tote it out for a closer look. Both planets will fit with room to spare in the same field of view, a sight not to be missed. Blazing Venus mimics a tiny full moon just 10″ across; Jupiter's three times as wide. Will you be able to spot Jove's two 'tire track' equatorial belts and four moons?
With twilight well underway, binoculars should help you track down the Beehive Cluster. I suspect you'll still see its brightest stars — look just to the left of Venus.
As close as this conjunction is for observers in North America, the planets will be even cozier for central European sky watchers. Closest approach of 13′ (0.2°) happens around 5h Universal Time as dawn's first light touches the rugged Alps.
Track Jupiter and its moons in the sky using Sky & Telescope's handy JupiterMoons app.
Even on Io, a world known for spouting off, the titanic volcanic eruption seen on August 29, 2013, was among the most powerful ever recorded there — or anywhere else in the solar system.
This time last year, a trio of volcanoes erupted so violently and powerfully that they would have been "breaking news" had they occurred anywhere on Earth. Fortunately, the towering fountains of fire were more than a half billion miles away, on Jupiter's moon Io.
Imke de Pater (University of California, Berkeley) discovered the first two outbursts on August 15, 2013, using one of the 10-meter telescopes at Keck Observatory in Hawaii. The brighter one, at a previously known eruption site named Rarog Patera, was calculated to have covered 50 square miles with a lava flow 30 feet thick. The other, at Heno Patera, spewed molten rock over roughly 120 square miles. Both had abated by the time de Pater checked again five days later.
But the real fireworks were yet to come. A third, even brighter eruption flared to life on August 29th and was captured simultaneously with the nearby Gemini North telescope and NASA's Infrared Telescope Facility on Mauna Kea. The outburst was so intense and hot — even by Io's standards — that it probably involved a cluster of towering lava fountains spread over an estimated 32 square miles. The eruption's location, within a few degrees of 223° west, 29° north, is not associated with any previously recognized volcanic site.
According to Katherine de Kleer, a UC Berkeley graduate student, the August 29th event unleashed an estimated 20 terawatts of energy, making it at least 10,000 times more powerful than the lava fountains spewed during the 2010 eruptions of Eyjafjallajökull in Iceland.
These near-infrared observations kicked off a year-long scrutiny of Io by de Kleer, de Pater, and two collaborators. Two analyses of the August 2013 eruptions, one led by de Pater and the other by de Kleer, were just published online in the planetary-science journal Icarus.
The Voyager 1 spacecraft first discovered volcanoes on Io during its 1979 flyby. Since then observations with spacecraft and ground-based telescopes have shown that this moon erupts nearly constantly, making it the most volcanic body in the solar system. About 150 sites are active now, and the total count is roughly 400. Researchers believe Io's eruptions mimic the kinds of volcanic activity that shaped the inner planets, including Earth, in the early solar system.
Track Jupiter and Io in the sky using Sky & Telescope's handy JupiterMoons app.
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