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
Friday, August 22
Altair is the brightest star shining halfway up the southeastern sky after nightfall. Look to its left, by a little more than a fist at arm's length, for the dim but distinctive constellation Delphinus, the Dolphin. He's leaping leftward, just below the Milky Way.
In Saturday's dawn, the thin waning crescent Moon forms an elegant triangle with Jupiter and Venus low in the east, as shown at lower right.
Saturday, August 23
August is prime Milky Way time. After dark, the Milky Way runs from Sagittarius and Scorpius in the south-southwest, up and left across Aquila and through the big Summer Triangle very high in the southeast and east, and on down through Cassiopeia to Perseus rising low in the north-northeast.
Sunday, August 24
Mars and Saturn are closest together this evening and Monday evening, separated by 3.4°. They're the same brightness but not the same color. And, compare Mars's color to that of its rival Antares, not quite as bright, in Scorpius about 20° to the left. (See the last illustration below.) Mars will pass Antares by just 3° in late September.
Monday, August 25
Before moonlight comes back into the evening sky, take the opportunity to explore the dim nebulae, and the somewhat brighter star clusters, around Deneb and the North America Nebula in Cygnus nearly overhead. They're not easy; use Sue French's maps, drawing, photo, and article in the September Sky & Telescope, page 56, to pinpoint what you're looking for.
New Moon (exact at 10:13 a.m. EDT).
Tuesday, August 26
If you're in the Earth's mid-northern latitudes, bright Vega shines near your zenith just as night becomes fully dark. Whenever you see Vega most nearly straight up, you know that Sagittarius, with its deep-sky riches, is highest in the south.
Wednesday, August 27
The wide W pattern of Cassiopeia is tilting up in the northeast after dark. Below the W's last segment to the lower left, by a little farther than the segment's length, look for an enhanced spot of the Milky Way's glow if you have a dark enough sky. Binoculars will show this to be the Perseus Double Cluster — even through a fair amount of light pollution.
Thursday, August 28
The Great Square of Pegasus is now well up in the east as soon as nightfall is complete. It's larger than your fist at arm's length and currently stands on one corner.
Friday, August 29
The Moon is coming back into the evening sky. Look for the waxing crescent low in the southwest in twilight, as shown below. Can you make out Spica twinkling beneath it? Binoculars help. Far to the upper left are Saturn and Mars.
Saturday, August 30
The waxing crescent Moon now shines closer to Saturn and Mars, as shown here. Can you see little Alpha Librae inside the middle of the narrow triangle they make?
Want to become a better astronomer? Learn your way around the constellations. They're the key to locating everything fainter and deeper to hunt with binoculars or a telescope.
This is an outdoor nature hobby; for an easy-to-use constellation guide covering the whole evening sky, use the big monthly map in the center of each issue of Sky & Telescope, the essential guide to astronomy. Or download our free Getting Started in Astronomy booklet (which only has bimonthly maps).
Once you get a telescope, to put it to good use you'll need a detailed, large-scale sky atlas (set of charts). The standards are the little Pocket Sky Atlas, which shows stars to magnitude 7.6; the larger and deeper Sky Atlas 2000.0 (stars to magnitude 8.5); and once you know your way around, the even larger Uranometria 2000.0 (stars to magnitude 9.75). And read how to use sky charts with a telescope.
You'll also want a good deep-sky guidebook, such as Sue French's Deep-Sky Wonders collection (which includes its own charts), Sky Atlas 2000.0 Companion by Strong and Sinnott, the bigger Night Sky Observer's Guide by Kepple and Sanner, or the beloved if dated Burnham's Celestial Handbook.
Can a computerized telescope replace charts? Not for beginners, I don't think, and not on mounts and tripods that are less than top-quality mechanically (able to point with better than 0.2° repeatability, which means fairly heavy and expensive). As Terence Dickinson and Alan Dyer say in their Backyard Astronomer's Guide, "A full appreciation of the universe cannot come without developing the skills to find things in the sky and understanding how the sky works. This knowledge comes only by spending time under the stars with star maps in hand."This Week's Planet Roundup
Mercury is deep in the sunset.
Venus (magnitude –3.9) and Jupiter (a sixth as bright at magnitude –1.8) shine low in the east-northeast during dawn. Jupiter is the upper one. They're drawing farther apart each morning: from 5° apart on August 23rd to 12° by the 30th. Jupiter is moving higher, and Venus is gradually sinking a little lower.
Mars and Saturn, both magnitude +0.6, glow in the southwest at dusk, finally having their conjunction. Mars is the lower one. They'll be just 3½° apart from August 23rd to 26th, then will widen again slowly. Compare their colors!
In a telescope, Mars is just a tiny 7 arcseconds wide. Saturn's dimmer globe is 17 arcseconds wide, and its rings span 38 arcseconds from end to end.
The fainter star just to their right is the wide binocular double Alpha Librae, magnitudes 2.8 and 5.2.
Uranus (magnitude 5.8 in Pisces) and Neptune (magnitude 7.8 in Aquarius) are well placed in the southeast and south after midnight. See our Finder charts for Uranus and Neptune online or in the September Sky & Telescope, page 50.
All descriptions that relate to your horizon — including the words up, down, right, and left — are written for the world's mid-northern latitudes. Descriptions that also depend on longitude (mainly Moon positions) are for North America.
Eastern Daylight Time (EDT) is Universal Time (UT, UTC, or GMT) minus 4 hours.
"The universe is full of magical things patiently waiting for our wits to grow sharper."
— Eden Phillpotts, "A Shadow Passes," 1918
Astronomers might have found a star that was infected by the explosive death of one of the universe’s first stars.
These first stars are called Population III stars, in an expansion of the Population I and II categories created by Walter Baade in the 1940s. Population I stars are generally the youngest, most heavy-element-tainted stars, while Population II stars are older and less tainted; Population III stars came (theoretically) before both.
Pop III stars would have formed from the pristine hydrogen-and-helium mix filling the early universe. They synthesized the first batches of heavy elements — such as carbon, oxygen, and iron — and spewed these into the cosmos when they died, thereby influencing the universe’s early evolution.
Astronomers haven’t found any of these stars still shining today. That, paired with computer simulations of conditions in the cosmos’s earliest eras, suggests that Pop III stars were the massive, live-fast-die-young type. Just how massive remains unclear, but most were probably several tens of Suns, with a few reaching a couple hundred times the mass of our star. (In other words, über-big.)
Such stellar behemoths would have died in spectacular supernovae. The most massive might even have died in a peculiar explosion that theorists call a pair-instability supernova, or PISN.
Stars generally exist in hydrostatic equilibrium, in which the collapse-encouraging force of gravity is balanced by the collapse-averse pressure of gas and radiation. In the lead-up to a PISN, the central temperature of the massive star rises to such a dramatic fever that the photons deep inside convert into electrons and their antimatter partners, positrons. Unfortunately for the star, electrons and positrons don’t do much for the outward, gravity-countering pressure, and so gravity takes over and initiates a runaway collapse. The collapse compresses the star’s innards, triggering runaway fusion of the star’s remaining fuel, which in turn sets off a colossal explosion.
A PISN explosion would taint the surrounding gas with high levels of nickel, calcium, and iron, among other things. But it wouldn’t create elements heavier than iron (such as strontium or barium) because that would require a cache of extra neutrons, and there aren’t a lot of neutrons around to work with. (A PISN doesn’t create a neutron star.)PISN Left a Mark?
Astronomers have seen hints of PISN-like events before, in a supernova seen in 2007 and also in two other superluminous explosions found in archival data of the early universe, reported in 2012.
Now Wako Aoki (National Astronomical Observatory of Japan and the Graduate University for Advanced Studies, Japan) and colleagues have approached PISNs in a different way, by finding a star that bears the chemical fingerprints of one of these explosions.
The star, SDSS J001820.5-093939.2, is one of 150 low-metallicity stars that the team surveyed. It’s a cool, hydrogen-core-fusing star with a mass just under half the Sun’s, shining at an apparent magnitude of 15.8 just south of the celestial equator, in the constellation Cetus.
J0018-0939 has the high levels of nickel, calcium, and iron expected from PISN tainting. It also has low levels of light elements, such as carbon and magnesium, compared with iron — also in keeping with PISNs. Its composition doesn’t fit what would have been created if it had formed from material infected with a regular, core-collapse supernova, with a white dwarf’s Type Ia supernova, or with a combination of the two. Instead, the various chemical markers suggest the best explanation is that the star formed from material seeded by the death of a very massive star (more than 100 solar masses and maybe up to about 250), either in a PISN or in a more run-of-the-mill, core-collapse supernova.
Admittedly, this all sounds like a game of Six Degrees of Separation, where the Pop III star is Kevin Bacon. “The thing is that stellar archaeology is always only circumstantial, even in the most clear-cut cases,” says Volker Bromm (University of Texas at Austin), who is at the forefront of Pop III theoretical work.
Bromm explains that there are two arguments in favor of the Pop-III enrichment scenario. One, the PISN theory naturally explains J0018-0939’s relatively high level of heavy elements: the PISN explosion inserted a whole lot of these metals into the local surrounding gas. Two, the standard explanations simply have more problems than the PISN one.
J0018-0939 is the only star of about 500 in this metallicity range that has this peculiar makeup, the authors note in the August 22nd Science. That parallels theoretical work done by Bromm and others that suggests these massive stars were only a few percent of the total Pop III population.
One interesting implication of the discovery by Aoki’s team: J0018-0939 is “metal poor” in the grand scheme of things (it has less than 1% of the Sun’s level of iron), but compared with the most metal-poor stars (where the iron abundance can be 1/100,000 or less of the solar level) the star is metal rich. Many astronomers assumed Pop III stars wouldn’t be able to contaminate their surroundings with a high level of heavy elements, and so they have focused on extremely metal-poor stars when looking for those formed from material marked by a Pop III supernova. But a PISN can inject a high level of heavy elements into its immediate surroundings, seeding material at a level higher than previously looked for. In other words, astronomers might have been looking in the wrong place for PISN-marked stars. Maybe with this new insight, they’ll be able to find more and learn how common highly massive stars were in the early universe.
Reference: W. Aoki et al. "A chemical signature of first-generation very massive stars." Science. August 22, 2014.
Read about what we know (and don't know) about the first stars in Sky & Telescope's Astronomy's 60 Greatest Mysteries.
Seize the moment and bookend your next clear night with two fine telescopic comets: Jacques at dusk and Oukaimeden at dawn.
Comet Jacques (C/2014 E2) has returned to evening skies! Discovered last March 13th by Cristovao Jacques and the Southern Observatory for Near Earth Asteroids Research (SONEAR) team, this comet hails from that commodious, cometary beer cave called the Oort Cloud, where these icy critters chill for billions of years as much as a light-year away from the Sun.
Earth takes a year to make a turn around the Sun and Pluto a tedious 248, but they’re speed demons compared to Jacques, which barely plods along for most of its 20,000-year orbit. It's been a long wait, but we're glad you're here.
Jacques lingered in the evening sky through spring, slowly brightening until passing perihelion on July 2nd. Pumped up now by solar heating and approaching Earth since that warm encounter, the comet has grown a bulbous head and long, skinny ion tail that bears an uncanny resemblance to the onions I've pulled out of my garden this summer.
Last month and early this, Comet Jacques resided in Taurus and Auriga low in the dawn, but its elongation (angular distance) from the Sun has been rapidly increasing over the past two weeks. In an exquisite example of astronomical timing, the Moon has departed the evening sky at the same time Jacques has returned to it. Sweet!
What's more, the comet is still magnitude +7 and within range of 10×50 binoculars. Don't expect onions though; Jacques will look more like a dab of mist. A 4-inch telescope is sufficient to reveal a bright pseudo-nucleus within a diffuse 7′ or 8′ coma. Large-scope owners will detect the pale green emission from cyanogen (CN) and diatomic carbon (C2) in the coma and possibly a degree or more of its long, faint tail.
Fortunately, as the comet's distance from the Sun continues to increase, its distance from Earth shrinks, causing it to remain steady in apparent brightness. Seiichi Yoshida, who maintains the excellent Weekly Information about Bright Comets, predicts that the comet will hold its current magnitude through early September. Jacques passes closest to our planet on August 28th at a distance of 52.4 million miles.Comet Oukaimeden
Dusting up the other end of the sky is Comet Oukaimeden (C/2013 V5). It's magnitude 8.5 or 9.0 at the moment, but this sleeping beauty is expected to crest to 5.5 by mid-September. Oukaimeden (OO-kay-MEE-den) is named for the observatory in Marrakech, Morocco, where it was discovered last November. As always, take predicted comet magnitudes with a teaspoon of skepticism.
Like Comet Jacques, this comet hails from the Oort Cloud — with an incoming orbital period measured in millions of years. After its orbit is gravitationally tweaked by the planets, particularly Jupiter and Saturn, it will drop by the inner solar system more frequently: about once every 6,000 years.
To see Oukaimeden, get to bed early and set your alarm for two hours before sunrise. You'll find it low in the eastern sky traveling east through dim Monoceros near Canis Minor.
Like a migrating bird, Oukaimeden heads south as fall approaches. Observers at mid-northern latitudes will only be able to track the comet until the start of September before it's lost in twilight. Those in the tropics and southern latitudes will hang onto it longer.
Have at these icy travelers now before they go back into hiding for the rest of our lives.
Read the eloquent tale of famed comet hunter Leslie Peltier in his book Starlight Nights.
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