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
Research shows that the magnetic fields in the asteroid parent bodies of two meteorites lasted hundreds of millions of years after our solar system’s formation.
Today, active magnetic fields surround Earth, Mercury, all the outer planets, and Jupiter’s moon Ganymede. But a new study in last week’s Nature shows that during the first tens of millions of years in the solar system’s life, numerous small bodies also possessed magnetic fields. Like miniature Earths, these objects had dynamos (the circulation of conducting fluid) in their cores to power their magnetic fields.
Both are pallasites, which come from the core-mantle boundary of a once-molten asteroid. Research shows that they acted as “recording devices” for the magnetic fields that once coursed through their parent bodies.How To Read A Meteorite
When the molten conducting fluid inside one of those parent bodies solidified, it locked in an imprint of the magnetic field that existed at that time. Using nanoscale imaging, an international team of researchers led by James Bryson (University of Cambridge) was able to measure these meteorites’ cooling and solidification rates and their magnetic activity. To measure these characteristics, the researchers looked at the physical structure of tetrataenite, an iron-nickel alloy, in each meteorite.
The team’s observations show that “asteroid magnetic fields probably were generated a lot like that of the Earth: by motion of iron metallic fluid in a core that is undergoing crystallization to form a solid core,” said planetary scientist Ben Weiss (MIT), who was not involved in the study. Previous paleomagnetic measurements were used to argue for the existence of such cores in small planetary bodies, but “beyond this fundamental inference, we don’t know much about ancient core convection within asteroids,” wrote Bryson on the project’s blog.
Analogous to the way tree rings chronicle droughts and times of plenty, the matrices of tetrataenite within Imilac and Esquel record changes of strength and direction of the magnetic field produced by their parent bodies over time — and the eventual shutoff of the field once theirs respective asteroid's core solidified. These are some of the first observations of how an asteroid’s magnetic field changes in time, notes Weiss.
Pallasite meteorites solidified slowly, at 2 to 9 Kelvin per million years, which allows for the tetrataenite “islands” to form snapshots of magnetic activity. The researchers saw that these islands exsolved and hardened over time as they cooled, so their sizes serve as rulers to measure the rate of cooling in the parent bodies, and thus the devolving of the magnetic fields.Magnetic Fields Extend Longer Than Previously Thought
While the exact size of Imilac’s and Esquel’s parent bodies are unknown, the researchers modeled the cooling of a 400-km-wide body — a size consistent with small rocky objects existing in the early solar system.
Previous research assumed that convection in these bodies was thermally driven (like a boiling pot of water, which transfers heat with physical motion from the pot’s bottom to the top). However, the data imprinted within the two meteorites shows magnetic activity lasting well beyond what thermally-driven convection could have sustained. The extra heat would have come from the gradual solidification of the molten metallic core.
Both the technique used for measuring these fossil fields and the results themselves have implications for planetary science. As Weiss explains, the research shows magnetic fields can be recorded “not just as magnetization (what gives a refrigerator magnet its pull), as is traditionally understood but also in the [physical] structures of minerals themselves.”
Further, since the team has showed that solidification-driven magnetic fields existed in the early solar system, we now have evidence that “a widespread, intense, and long-lived epoch of magnetic activity likely existed among many small bodies,” Bryson notes in the project’s blog. This activity lasted tens to hundreds of millions of years after the solar system’s formation, a timescale that’s an order of magnitude greater than previous theories had assumed.
James F. J. Bryson et al. “Long-lived magnetism from solidification-driven convection on the pallasite parent body.” Nature, Published online 21 January 2015.
Sky & Telescope's year-at-a-glance guide to celestial happenings is a symphony of detailed calculations and clear, elegant design.
If you're an active backyard observer — or just celestially curious — you're always looking for quick, reliable information about "what's up" in the nighttime sky. When is the next new Moon? Can I see Saturn tonight? When will twilight end?
The editors at Sky & Telescope are no different. And while we have scores of detailed references to draw from, one of the handiest is the "Skygazer's Almanac" found in every January issue of the magazine. This single sheet represents a fruitful melding of detailed computations and graphic representation that has been perfected over the years.
A graphical sky almanac has accompanied every January issue of Sky & Telescope since 1942 — that's more than 70 years! The main purpose of this chart is to let you see, at a glance, which planets and constellations are visible, and what the Moon's phase is, on any given date and time of night throughout the year.
There have been three "epochs" of this chart since its inception. From 1942 to 1980, each January issue featured the "Graphic Timetable of the Heavens," prepared annually by the Maryland Academy of Sciences. Then for two years it was called the "Graphic Ephemeris," computed and drafted by Michael Jay Jones (who had done this work for the Maryland Academy before then).
These charts had the same basic content. They showed the hours of night increasing from left to right, while the dates of the year ran from top (January 1st) to bottom (December 31st). Smooth curves provided the times of sunrise and sunset, as well as the end of evening twilight and start of morning twilight. Additional curves give the rise, transit, and set times of bright planets and stars. Moon symbols appeared at the times of its rising or setting each night, while other symbols indicated planetary conjunctions and oppositions.SGA: The Next Generation
As good as they were, both of those charts suffered from the limitations of black-and-white printing. So in 1983 Sky & Telescope introduced its own computer-generated chart, the "Skygazer's Almanac." We introduced some big changes then, as well as other enhancements and improvements over the years:
Two key upgrades have really improved the chart's overall utility. First, we omitted the daylight portions of what had been a rectangular graph. This gave the chart a pleasing hourglass shape and, conveniently, freed up space to list key evening and predawn events down the left and right sides, respectively.
Second, we made versions for different latitudes. The original was plotted for those living at latitude 40° north, for use throughout North America and much of Europe. But beginning in 1998, additional charts were created for latitude 50° north (handy for northern Europeans) and 30° south (for use in Australia and the southern parts of Africa and South America).
These charts aren't just used by backyard astronomers. If you visit any major observatory, don't be surprised if there's a "Skygazer's Almanac" hanging on the wall. In fact, some years ago we concluded that the two-page chart that's bound into each January issue could be made much more readable in a poster-size version — so now a 30-by-22-inch full-color wall chart is available as well.
We pack a lot of information into each chart, and each is accompanied by a sheet of instructions that tell you what the symbols represent and how to "read" the events of a given night.
Take a look at the section above, which is shown at roughly the full size of the wall chart. You can see how the times of sunset and the end of twilight come later and later throughout January and February. Moon symbols indicate that it's full on the evening of January 4th and again on February 3rd. An orange curve shows that Mercury made a brief evening appearance in mid-January, and the light blue one shows Venus lingering a bit higher up after sunset each week. Mars sets around 8 p.m. each night; Jupiter rises at that time on January 1st but comes up two hours earlier, around 6 p.m., by the 27th.
Other curves show when Sirius rises, the Pleiades and Orion Nebula transit the north-south meridian, and when Polaris culminates directly over the North Celestial Pole. Clearly, January and February are busy months, celestially speaking!
The more you refer to this chart, the sooner you'll get a feel for the march of planets and constellations — not just during a single night but from week to week during the year. In fact, if you compare this year's chart with those from past years, you'll discover more and more about the clockwork of the heavens. For example, on charts eight years apart, the curves for Venus match almost perfectly — a celestial cycle known to the ancient Maya. On charts 19 years apart, the Moon makes its own encore performance.
Working up the "Skygazer's Almanac" takes a lot of effort — but it's one of the most rewarding projects I do all year. If you've got one, please add a comment below to let us know how you use it and what improvements we might make.
Astrobiologists discuss the search for life beyond Earth — join the conversation!
Courtesy of The Kavli Foundation, Sky & Telescope is featuring an in-depth Q&A with two astrobiologists on the search for extraterrestrial life.
Within 10 years, scientists at NASA and elsewhere are aiming to send life-seeking robots to Mars and to Saturn’s icy moon Enceladus. But first they must decide where to look, what evidence of life to look for and how to detect it.
To answer those questions, they’ve turned to “extremophiles,” microorganisms that inhabit the Earth’s most hostile environments. By stretching the limits of life on this planet, these organisms are improving the odds that faraway places thought to be uninhabitable may harbor it, too.
DiRuggiero and McKay discussed the next missions to search for life in our solar system in The Kavli Foundation roundtable discussion Microbiome and Astrobiology: How to Search for Life on Other Worlds. Now, join the conversation with two prominent astrobiologists who study life at the extremes and how to hunt for it on other worlds.
JOCELYNE DIRUGGIERO, PhD is Associate Research Professor in the Department of Biology at Johns Hopkins University in Baltimore and a member of the University’s Institute for Planets and Life. She studies how microorganisms adapt to extreme environments and what that can teach us about searching for life on other planets.
CHRISTOPHER McKAY, PhD is a senior scientist in the Space Science and Astrobiology Division at NASA Ames Research Center who studies life in Mars-like environments on Earth and plans missions to search for evidence of it.
LINDSAY BORTHWICK (moderator) has been working as a science journalist for more than a decade and holds a Master’s degree in neuroscience.
Has Comet Q2 Lovejoy stoked you to see more of these celestial travelers? We look into the crystal ball to see what's coming in 2015.
How fortunate we are to begin 2015 with a naked eye comet. Many of you have undoubtedly seen Terry Lovejoy's most recent discovery, C/2014 Q2 Lovejoy, either in the flesh or in photos across the Web. Topping out around magnitude +3.8 earlier this month, this icy blue gem still hovers around +4.5 as January draws to a close. Who knows — Q2 may turn out to be the best comet of the year.
Looking back, 2014 was a generous one for bright comets. Bright could mean "visible with the naked eye," but since naked-eye comets are so scarce, we'll choose a slightly different definition which (I hope) comet aficionados will find acceptable. How about anything visible in an ordinary pair of 7 x 50 binoculars from a reasonably dark sky? That would set our limiting magnitude at about +8.
Using this criterion, 2014 presented skywatchers with six bright comets — C/2013 R1 Lovejoy (6th magnitude in January); C/2014 E2 Jacques (7 in August); C/2013 V5 Oukaimeden (+6.5 in September), C/2012 K1 PanSTARRS (+7.5 in October), 15P/Finlay (briefly at +8.7 during an unexpected outburst in December), and of course Q2 Lovejoy (+5.0 in December).
2015 began with a bang with Lovejoy and a second surge from from 15P/Finlay to magnitude +7.5 in mid-January, but we'll soon enter the doldrums as Q2 Lovejoy fades below 6th magnitude sometime next month.
Barring the discovery of a bright newcomer, the new year offers up three bright entries: 88P/Howell, C/2014 Q1 PanSTARRS, and C/2013 US10 Catalina. Let's look at each in turn.
* 88P/Howell — Discovered with the 0.46-m Schmidt telescope at Palomar Observatory on 1981. It reaches perihelion on April 6th, when it could become as bright as 8th magnitude. Northerners need not apply — this comet will be only be visible from the southern hemisphere during the fall season (April, May). More on 88P.
* C/2014 Q1 PanSTARRS — Not only is Hawaii the surfing capital of the world, but it's lately become a hotbed of comet discovery thanks to the Panoramic Survey Telescope & Rapid Response System (PanSTARRS) survey atop Mt. Haleakala, a favorite tourist destination. Created to discover and characterize Earth-approaching asteroids and comets, the automated survey has bagged more than 80 new comets since full-time science operations began in 2010.
Discovered in August 2014, Q1 PanSTARRS will reach perihelion on July 6, 2015, after passing just 0.3 a.u. from the Sun. Expectations are high for it to grow a long, bright tail and possibly crest to magnitude +3 at nightfall during July and early August in the middle of southern winter.
* C/2013 US10 Catalina — Finally, northern folk get their due! US10 was discovered by the Catalina Sky Survey on Halloween 2013. For much of the year, the comet remains the province of southern hemisphere skywatchers. In late July and early August, it reaches magnitude +7 and becomes a south circumpolar object. By late September the comet achieves naked eye visibility (6th magnitude). After perihelion on November 15th perihelion, it surges into view for northern hemisphere skywatchers and peaks at around magnitude +3. As 2015 gives way to 2016, US10 remains bright as it buzzes Arcturus on New Year's night.
One last comet that must be mentioned, even if it's not expected to surpass 10th magnitude, is 67P/Churyumov-Gerasimenko. Thanks to the Rosetta mission, 67P has become the most intensely interesting comet in recent years. After months of close-up photos of the comet's nucleus, amateur astronomers are eager to see "Chury" for themselves. We'll have our chance in late August when it returns to the morning sky in Gemini-Cancer following perihelion on the 13th.
While comets seem sparse this year, there's no telling when a new one will blow out of nowhere and surprise us all. Old, familiar ones sometimes experience bright outbursts as well. Their unpredictability just keeps us coming back for more.
Once the Rosetta spacecraft arrived at Comet 67P/Churyumov-Gerasimenko last August, European scientists used an array of instruments to assess every nook and cranny of the remarkable two-lobed nucleus.
It took the comet-chasing Rosetta spacecraft 10½ years to reach its objective. That's a long time to wait to find out if all the systems and instruments are going to work as planned.
Fortunately, vindication for the European Space Agency and for scores of mission scientists came soon after the spacecraft reached Comet 67P/Churyumov-Gerasimenko last August 6th. In fact, even before the hitchhiking Philae lander made the first-ever soft landing on a comet on November 12th, the mother ship's 11 experiments had scrutinized the stark, two-lobed nucleus from tip to tip — occasionally from as close as 6 miles (10 km). The first two months' observations are summarized in a set of seven articles published last week in Science.
In my view, the most far-reaching discovery by Rosetta to date was actually announced some weeks ago, ahead of the magazine's print edition: Comet 67P's water molecules have a deuterium-to-hydrogen ratio far higher than that in Earth's oceans. Particularly because this is a Jupiter-family comet (JFC), the type that are most likely to have collided with Earth over the eons, this argues that comets contributed very little of our planet's water.
Meanwhile, the spacecraft's basic measurements of this object are interesting in themselves. Far from being an idealized orb of ice and rock, the comet's nucleus has a two-lobed shape that invites wild speculation as to its origin.
In an article describing results from the OSIRIS camera, Holger Sierks (Max Planck Institute) and his team note that the larger lobe is 2.5 miles (4.1 km) long, while the smaller one spans 1.6 miles (2.6 km). They're joined by a narrow waist, which intriguingly has been the source of most of the comet's escaping gas and dust to date. It's not clear whether the comet assembled as two large masses or that its midsection was once much plumper but has gradually eroded away.
Four other details about the nucleus are intriguing. First, it's very dark overall, with an average reflectivity of just 6% — nearly black, much like charcoal. This jibes with the albedos found at Comet 9P/Tempel 1 nearly a decade ago at Comet 103P/Hartley 2 in 2010 by NASA's Deep Impact spacecraft. Ditto for the nucleus of 1P/Halley. There's an unmistakable trend here: when you think "comet," think black.
What has likely happened is that rapidly escaping gas has carried off bits of dust that are not moving as fast, so they eventually settle back onto the surface. The comet's low gravity (less than 1⁄100,000 that on Earth), combined with its 12.4-hour spin, distribute these particles all around to create an even veneer.
Second, based on how strongly it attracts Rosetta, the nucleus must have a mass of about 10 billion metric tons. That's certainly hefty — it's about 25 million times the mass of the International Space Station, for example. But Sierks and his team report that the comet's overall density is just 0.47 g/cm3 — similar to wood. It's not made of wood, of course, but the ice-and-rock interior must be very "fluffy," with a porosity of 70% to 80%.
Third, scans by Rosetta's VIRTIS instrument (short for Visible, Infrared and Thermal Imaging Spectrometer) hasn't found any ice on the surface of 67P. Instead, a team led by Fabrizio Capaccioni (INAF, Italy) reports that the dark exterior is covered with complex, carbon-rich organic molecules. "VIRTIS clearly observed a comet that is different from the other JFCs encountered so far," the groups notes, because other such comets do have exposures of water ice on their surfaces. (The original leader of the VIRTIS team, Angioletta Coradini, never got to see these results; she died of cancer in 2011.)
The VIRTIS data suggest the organic molecules have lots of carbon-hydrogen bonds but few involving nitrogen. The team doesn't speculate as to what these are — but I will! It's possible that compounds are polycyclic aromatic hydrocarbons (PAHs) — much like the stuff coating the dark half of Saturn's moon Iapetus (not to mention what results when you grill a steak too long).
Finally, the surface is Comet 67P/Churyumov-Gerasimenko is a wonderland of weird landforms. The OSIRIS team has subdivided Comet 67P into 19 regions, all named for ancient Egyptian deities, that correspond to five distinct terrain types: smooth, brittle with pits and circular structures, large depressions, dust covered, and consolidated ("rock-like"). For example, Hapi (the god who makes the Nile River flood each year) is the smooth terrain in the neck that, thus far, has dominated the comet's outgassing. Looming above Hapi is a striking cliff face. Gas-spewing pits dot the region called Seth (a violent god associated with storms and disorder), and elsewhere the camera recorded enigmatic mounds, about 10 feet (3 m ) across, that the OSIRIS team calls "goosebumps."
Not a bad scientific haul for two months' work, and many other results (such as water-escape rates and solar-wind interactions) are detailed in the Science papers. And yet the most exciting events are still months away. Comet 67P/Churyumov-Gerasimenko is moving inward toward its August 13th pass through perihelion, by which time the nucleus should be jetting much more vigorously.
Read all about the Rosetta mission in Sky & Telescope's August 2014 issue.
27 Hubble, Irvine, CA 92618
Meade Instruments unveils its new Series 5000 Mega Wide Angle eyepieces (starting at $199.95). These wide-field oculars feature an expansive 100° apparent field of view with comfortable eye-relief of 13 to 20 millimeters that can accommodate observers wearing eyeglasses. Both of the 5- and 10-mm models fit 1¼-inch focusers, while the 15- and 21-mm versions are 2-inch format only. Each Mega Wide Angle eyepiece incorporates blackened lens edges to enhance contrast, and their parfocal design requires little or no focus change when switching between eyepieces within the series.
SkyandTelescope.com's New Product Showcase is a reader service featuring innovative equipment and software of interest to amateur astronomers. The descriptions are based largely on information supplied by the manufacturers or distributors. Sky & Telescope assumes no responsibility for the accuracy of vendors statements. For further information contact the manufacturer or distributor. Announcements should be sent to nps@SkyandTelescope.com. Not all announcements will be listed.
The post Asteroid Discovery–passing through M48, precursor to 2004 BL86 appeared first on Sky & Telescope.
Copyright © 1999-2010 Falak Online. All rights reserved. Powered by Drupal.
Penafian: Falak Online tidak bertanggungjawab terhadap sebarang kehilangan atau kerosakan yang dialami kerana maklumat dalam laman web ini.