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
On Sunday afternoon, April 10th, you'll see the waxing crescent Moon hanging high in a sunny blue sky if the weather is as good as we hope it'll be. Look with a telescope from nearly anywhere in North America, and you can find something else too. Somewhere in the Moon's vicinity will be 1st-magnitude Aldebaran: a tiny yellow-orange spark shimmering in the blue. And if you're watching at the right moment, you can see Aldebaran snap out of view in the blink of an eye as the Moon's dark limb (invisible in the daylight!) covers it up.
The farther east you are, the later in the afternoon the occultation will happen, so the lower the Sun will be and the more readily you should be able to sweep up Aldebaran.
The event happens a little after sunset in much of the Canadian Maritimes. Along the East Coast from Maine to Miami, the Sun will still be about 3° to 12° above the western horizon. Farther west the Sun will be higher and the sky brighter, so the clarity of your air will matter more. Only northern Canada and Alaska miss the occultation completely.
Aldebaran will reappear from out from behind the Moon's bright limb up to an hour or more later, when the Sun will be lower and even, for the East Coast, may have recently set. But Aldebaran will be harder to see as it buds out from the sunlit moonscape, so you'd still need the telescope.
The Moon will be a thinnish, 17%-illuminated crescent. You’ll find it about 50° to the Sun's celestial east.
Some predicted times of the star's disappearance and reappearance, at cities from east to west:
Halifax: disappearance 8:00 p.m., reappearance 8:56 p.m. ADT.
Montreal, d. 6:47, r. 7:48 p.m. EDT.
Boston, d. 6:51, r. 7:56 p.m. EDT.
Toronto, d. 6:39, r. 7:46 p.m. EDT.
Washington, DC, d. 6:43, r. 7:55 p.m. EDT.
Atlanta, d. 6:34, r. 7:49 p.m. EDT.
Miami, d. 6:57, r. 7:50 p.m. EDT.
Chicago, d. 5:25, r. 6:39 p.m. CDT.
Kansas City, d. 5:11 , r. 6:31 p.m. CDT.
Austin, d. 5:07, r. 6:22 p.m. CDT.
Winnipeg, d. 5:17, r. 6:13 p.m. CDT.
Denver, d. 3:51, r. 5:11 p.m. MDT.
Edmonton, d. 4:12, r. 4:36 p.m. MDT.
Vancouver, d. 2:48, r. 3:28 p.m. PDT.
Berkeley, d. 2:21, r. 3:37 p.m. PDT,
Los Angeles, d. 2:21, r. 3:42 p.m. PDT
Honolulu, d. 10:29, r. 11:28 a.m. HST.
Detailed timetables for 570 cities and towns, including in Mexico and the Caribbean, are on the massive website of the International Occultation Timing Association (IOTA). In the timetables are the altitudes of the Sun and Moon at the time of the event for each location.
That link brings up three tables: for Aldebaran's disappearance, reappearance, and the locations of the cities. The three are stacked without very obvious demarcations between them, so watch for the breaks as you scroll. The two capital letters designate the country; remember CA means Canada, not California.
Can you get good pix of this event? Post 'em in our Gallery!
Modern security threats have brought back an old method — celestial navigation — to help U.S. Navy sailors navigate the high seas.
It's a scene straight out of a Tom Clancy novel. An adversary, seeking to gain the upper hand, manages to blind GPS satellites in a first strike. As alert levels rise and military leaders attempt to assess the situation, ships at sea must somehow get an accurate fix of their position . . . without the use of modern technology.
The United States Navy recently recognized modern vulnerabilities by bringing back an old method for navigating at sea: the Naval Academy in Annapolis, Maryland, has just resumed training officers in the lost art of celestial navigation. Although this training used to be standard in the U.S. Navy, the advent of GPS technology so simplified and improved the ability to find a ship's position at sea that the Navy ROTC ended celestial navigation training in 2000, and the U.S. Naval Academy phased it out as well in 2006.
But the U.S. Navy and the Department of Defense are taking cyber threats to technological infrastructure seriously. Commercial GPS jammers are now readily available on the internet. And while the U.S., China, the European Union, Russia, and India are all moving to assure they have their own exclusive GPS network in orbit, a deliberate attack may not even be necessary. A space debris chain reaction known as an ablation cascade could knock out our GPS capability, or a strong Earth-directed solar storm such as the 1859 Carrington super-flare event could do the job just as well.
"There is an effort throughout the Navy for midshipmen, officers, and sailors to become more familiar and comfortable with celestial navigation," says Lt. Daniel Stayton, an instructor of the U.S. Naval Academy CELNAV course. "We are currently in the first steps of reintroduction back into the fleet."
The U.S. Naval Academy brought back celestial navigation theory for its 2015 summer session, and the graduating class of 2017 will be the first in more than a decade with basic instruction in celestial navigation theory.Losing Our Way — and Finding It Again
This sort of "back to basics" approach echoes a growing refrain: our over-reliance on GPS has made navigational skills all but vanish. My wife and I are the first to admit, it's both amazing and a little scary just how reliant we've become on Google Maps as we travel in Europe. Then again, I also remember that same GPS technology used to lead would-be visitors to our Florida home down a nearby dead-end street.
Although the U.S. military pioneered the development of GPS technology in the 1970s, widespread civilian use only came after May 2000, when President Clinton directed the removal of intentional inaccuracy (known as selective availability, a precaution to assure an enemy wouldn't utilize GPS) that had been built in to early commercially available systems. The U.S. Navy now typically uses the Voyage Management System developed by Northrop Grumman for navigation at sea.
But for centuries sailors had found their way using the stars.Celestial Navigation: The Basics
In the Northern Hemisphere, it's pretty straightforward to find latitude by noting the elevation of the star Polaris, which marks the celestial north pole. Navigators can also measure the Sun's elevation at noon. Discerning longitude, however, is trickier and requires accurate timekeeping.
From the surface of the Earth, the imaginary sphere of the sky along the celestial equator appears to rotate 15 degrees per hour. In fact, we mark off right ascension in the sky — analogous to longitude of the surface of the Earth — in hours, minutes, and seconds. A land-based observatory will therefore see a celestial object rise, transit the local meridian bisecting the sky from north to south, and set at a different time than a ship at sea.
A navigator would note stars' positions using a sextant to measure the angle between each star and the horizon. Then the navigator would compare the measurement to an almanac published for a particular location. With this painstaking method, a seasoned celestial navigator could reckon a ship's position down to about two kilometers.
Getting an accurate fix on longitude, however, had to wait for accurate timekeeping. Early efforts relied on complex lunar tables. By the mid-19th century, such methods improved and longitude measurements became increasingly accurate. Some clever methods were devised as well: Christopher Columbus and Captain Cook both made use of lunar eclipses to gain one-time measurements of their positions at sea. Astronomers of the day also proposed using the transits of Jupiter's moons in a similar fashion, though observing such events from the deck of a pitching ship at sea proved problematic.
Apollo astronauts even practiced celestial navigation on their missions to the Moon, in the event that a loss of communication meant they had to find their own way home.
"Redundancy improves readiness," notes Stayton. "If the Navy is able to add an additional layer of redundancy . . . by merely teaching a skill, then an opportunity exists to improve readiness throughout the fleet."
It's great to see an old method brought back to guide the modern tech-savvy military. Perhaps we should all take a cue from the U.S. Navy and keep those paper maps handy the next time we head out on our next GPS-guided adventure . . . just in case.
In 2002, high-school student Jennifer Barlow had a simple idea: let's take some time to appreciate the beauty of the cosmos and consider ways to reduce the spread of light pollution. Here's how you can join the celebration!
Have you ever stepped outside to take in a view of the starry sky overhead — only to have your celestial panorama ruined by the ugly glow of light pollution? Maybe it's coming from a neighbor's security light or the combined glow over your whole town. Either way, light pollution prevents virtually all of us from viewing a pristinely beautiful night sky.
Back in 2002, a Virginia high-school student named Jennifer Barlow decided to do something about this, at least in her hometown of Midlothian, Virginia. First, she encouraged her friends and neighbors just to enjoy the beauty of a star-filled night sky — then she urged them to take some modest, common-sense steps to reduce the light pollution that outdoor lighting creates.
Barlow is all grown up now (she's a visiting professor at Wake Forest University), but her simple idea has blossomed into an annual event called International Dark-Sky Week. It's always celebrated in April, which is also Global Astronomy Month. This year celebrations begin Monday, April 4th, and run through Sunday, April 10th.
Now, as then, IDSW's goals are simple:
These days, IDSW is coordinated by the International Dark-Sky Association, whose members campaign year-round for better outdoor lighting. The goal is not to simply turn off all lights at night. Like it or not, we've become a 24/7 society — and, like it or not, nighttime activity requires some illumination to help us find our way along streets and sidewalks.
But there's a huge difference between the harsh, glary lights pictured at right and lighting that's well designed to illuminate the ground so that glare and light pollution are minimized. Too many fixtures send light streaming up into the sky, or provide far more light than is necessary, or are simply left on when they're not needed.You Can Make a Difference
So, you might be thinking, "How can I reduce light pollution?" Easy! The first steps can be as simple as holding a neighborhood stargazing session sometime this week, or installing a motion detector on your outdoor security lights.
If you're a regular visitor to SkyandTelescope.com, you know my views on light pollution. I'm especially eager to see more support and involvement from amateur and professional astronomers — the very individuals who stand to gain the most from reducing light pollution.
So please take a few minutes to learn more about IDSW and the many ways, big and small, that you can participate. Meanwhile, here's a list of public events planned for this week, and here's more information about Global Astronomy Month.
Friday, April 1
• Spring is here! Which means Arcturus shines brightly in the east, though still not high. The Big Dipper, high in the northeast, points its curving handle to the lower right down toward it. Jupiter shines very high far to Arcturus's upper right.
Arcturus forms the pointy end of a long, narrow kite pattern formed by the brightest stars of Bootes, the Cowherd. The kite is currently lying on its side to Arcturus's left. The head of the kite, at the far left, is bent slightly upward. The kite is 23° long, about two fist-widths at arm's length.
• This evening, telescope users along a narrow path from the Seattle/Vancouver area to Arkansas can watch for a 9.5-magnitude star (located 10° northwest of the Pleiades) to disappear for up to 9 seconds behind the invisibly faint asteroid 2892 Filipenko. Track map and finder charts for the shadow path across the US, the star to be occulted, and times.
Saturday, April 2
• This is the time of year when Arcturus shines just as high in the east as Sirius, the brighter Winter Star, shines in the southwest (as seen from mid-northern latitudes).
Sunday, April 3
• Draw a line from Castor through Pollux and follow it farther out by a big 26° (about 2½ fist-widths at arm's length). You're at the dim head of Hydra, the Sea Serpent. In a dark sky it's a subtle but distinctive asterism about the size of your thumb at arm's length. Through light pollution, binoculars show it easily.
Monday, April 4
• Double shadow on Jupiter late tonight, for telescope users in central and western North America. From 2:37 to 3:19 a.m. Tuesday morning Pacific Daylight Time, both Io and Europa cast their little shadows onto the planet.
Tuesday, April 5
• The huge, bright Winter Hexagon is still in good view at nightfall, filling the sky to the southwest and west. Start with brilliant Sirius in the southwest, the Hexagon's lower left corner. High above Sirius is Procyon. From there look even higher for Pollux and Castor, lower right from Castor to Menkalinen and bright Capella, lower left to Aldebaran, lower left to Rigel at the bottom of Orion, and back to Sirius.
Wednesday, April 6
• Io crosses the face of Jupiter tonight from 9:52 p.m. to 12:07 a.m. EDT, followed by its more visible black shadow from 10:32 p.m. to 12:47 a.m. EDT.
Meanwhile, Europa disappears behind Jupiter's preceding (celestial western) limb at 10:48 p.m. EDT.
Thursday, April 7
• Io emerges from eclipse by Jupiter's shadow, just beyond Jupiter's following limb, at 10:04 p.m. EDT.
• New Moon (exact at 7:24 a.m. EDT).
Friday, April 8
• Looking west in twilight, use the thin crescent Moon as your guidepost to Mercury, as shown at right.
• Jupiter this evening is just 0.1° north of 5th-magnitude Chi Leonis. Binoculars show the star looking like an out-of-place moon of Jupiter. A 6-inch telescope may show that, compared to this star, Jupiter's moons are not quite pinpoints.
Saturday, April 9
• The crescent Moon shines in the west in twilight. Look for Mercury far down to its lower right, as shown here. Then as the stars come out, spot Aldebaran to the Moon's upper left and the Pleiades to its upper right.
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.
Once you get a telescope, to put it to good use you'll need a detailed, large-scale sky atlas (set of charts). The basic standard is the Pocket Sky Atlas (in either the original or new Jumbo Edition), which shows stars to magnitude 7.6.
Next up is the larger and deeper Sky Atlas 2000.0, plotting stars to magnitude 8.5, nearly three times as many. The next up, once you know your way around, is 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, or the bigger Night Sky Observer's Guide by Kepple and Sanner.
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 (meaning heavy and expensive). And 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 (bright at magnitude –1.5 to –1.0) emerges into evening view this week. Look for it low in the west-southwest in bright twilight. Binoculars will help. By late in the week it will be easy naked-eye. Mercury is coming into its best evening apparition of the year.
Venus is deep in the glow of sunrise. Can you still make it out at all? Bring binoculars, and look barely above the horizon due east as dawn grows very bright. This the end of the long morning apparition of Venus that began last summer.
Mars (about magnitude –0.5, at the head of Scorpius), rises around midnight daylight-saving time. Before dawn it blazes yellow-orange in the south, to the right of dimmer Saturn. In a telescope Mars is about 12 arcseconds in diameter — quite big enough now to show surface features in a good 3-inch scope at high power during good seeing.
By the time of its opposition and closest approach in late May, Mars will quadruple in brightness and grow to 18.6 arcseconds wide. See our telescopic guide to Mars in the April Sky & Telescope, page 48.
Jupiter (magnitude –2.4, near the hind foot of Leo) shines high in the southeast after dusk and highest in the south by 11 or midnight. It sets in the west before sunrise. See our telescopic guide to Jupiter in the March Sky & Telescope, page 48.
Saturn (magnitude +0.4, in the legs of Ophiuchus) rises around midnight or a bit later, 10° lower left of Mars. By early dawn they stand in the south — Saturn on the left, bright Mars on the right — with fainter, Mars-colored Antares below them making it a triangle.
Uranus and Neptune are hidden in the glare of the Sun.
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.
“This adventure is made possible by generations of searchers strictly adhering to a simple set of rules. Test ideas by experiments and observations. Build on those ideas that pass the test. Reject the ones that fail. Follow the evidence wherever it leads, and question everything. Accept these terms, and the cosmos is yours.”
— Neil deGrasse Tyson
In breaking news today, astronomers have discovered Pi in the sky, proposed a revolutionary search for extraterrestrial environmentalism . . . and oh yes, April Fools’!
And this particular April 1st is no different — read on to see what the astro-tomfoolery is all about.Pi in the Sky
Astronomers have spent years mapping the afterglow of the Big Bang (known as the cosmic microwave background, or CMB) to extremely high precision. The maps they’ve created, which happen to look a bit like Jackson Pollock paintings, show the incremental differences in temperature incurred by random density fluctuations in the early universe.
Among those random fluctuations, astronomers have found a few so-called anomalies: pieces of the CMB sky that aren’t quite as random as they ought to be. They’ve found a “cold spot”, an apparent lopsidedness dubbed the “axis of evil”, and even the initials of Stephen Hawking.
Now, Ali Frolop and Douglas Scott (University of British Columbia, Canada) have joined forces to show similar non-random “anomalies” in the digits of Pi, such as a “hot spot” to mirror the CMB’s cold spot. As the authors point out, one must put aside “the unreasonable possibility that these are just the sort of flukes that appear when one looks hard enough.”
The paper’s brilliance (especially the lucidity found in its footnotes) is difficult to summarize, so we encourage you to read it on the arXiv’s astrophysics preprint server. The reading will transform your understanding of the CMB anomalies and of Pi. By the end, not only will you learn how to write poetry in "Pilish" or search for your own name in the transposed digits of Pi, you’ll also discover the true importance of the digits Pi and e — together, they spell “Pie.”SET-E: The Search for Extraterrestrial Environmentalism
In this remarkable study, astronomers Ben Montet (Caltech) and Ryan Loomis (Harvard-Smithsonian Center for Astrophysics) undertake the feasibility of the search for extraterrestrials minding their own environment.
As we all know, aliens may well be malevolent and we may not want to attract undue attention from such beings. So, the authors suggest, perhaps one way of detecting a benevolent society would be to look for one that creates and then gets rid of an ozone hole. After all, if they care about their own planet, they might decide not to invade ours . . . we hope.
Read more about the authors’ findings on the arXiv.Russia Sending Chimp to International Space Station
Speaking of extraterrestrial life, chimpanzees don't want to be left out of the space game. An article published online today reveals that Russia plans to send chimpanzee Yurya as a replacement for its current cosmonaut at the International Space Station. Russia is beginning this program in light of budget cuts (and perhaps due to jealousy over all the attention NASA gets), but it comes with an unexpected side benefit: the potential to renew children's interest in the STEM fields.
Read more about Russia's new chimponaut program here.New Abstract/Dating Service for Astronomers
The NASA Astrophysical Data System has roled out a new service dubbed Enhanced®. Among its many features: Make sure your papers are boosted to the top of search results, add tweets and Facebook likes to your citation count, and try out ADS Dating, where you can rank potential mates . . . by citation!Solar System Tourism
At Sky & Telescope, we enjoy planning tours for future astronomical events. So when we heard about the tantalizing possibility of eating extreme shrimp underneath the salty, subsurface sea on Europa, naturally we started thinking ahead. Unfortunately, it looks like that restaurant hasn’t opened just yet, but we’ll keep our wanderlust satisfied in the meantime with visions of the future.A New Day, a New Cosmology
SDSS is reporting a groundbreaking result that w, the equation of state for dark energy, is equal to -1.3. For those not well-versed in the mathematics of cosmology, that means our universe is in for a Big Rip, a far future when everything, even atoms, will rip apart.
Here's the sequence of events, as revealed by tweets:
— Sloan Digital Sky (@sdssurveys) April 1, 2016
— Sloan Digital Sky (@sdssurveys) April 1, 2016
— Sloan Digital Sky (@sdssurveys) April 1, 2016
We forgot to divide by h. pic.twitter.com/eRBoYkEkM8
— Sloan Digital Sky (@sdssurveys) April 1, 2016
Oh well, I guess w is still equal to -1, and the universe will keep on keeping on.Another Signal from LIGO?
And last, but definitely not least, S&T Senior Editor Alan MacRobert has heard a rumor that the LIGO collaboration has detected another gravitational wave signal: this one showing the signature expected of the Star Trek Enterprise going into warp drive. Surely Trekkies out there have already conducted the simulations of what such a signal would look like?
We’ll have to wait and see if that rumor pans out. In the meantime, happy April Fools’!
This month's astronomy podcast takes you on a guided tour of the night sky. You'll find Mars and Saturn near each other before dawn, while Jupiter and Mercury join the fading constellations of winter in the evening sky after sunset.
April is one of the better months for stargazing. Spring evenings are generally pleasant, and the bugs haven’t taken control — yet! Even with daylight time in effect, evening twilight comes fairly early. You’ll find that the Sun sets between 7:30 and 8:00 p.m. during most of this month, and by 9 p.m. it’s good and dark.
Get up before dawn, and you'll be rewarded with a bright triangle of beacons in the south that's roughly the size of your clenched fist held at arm’s length. The red-supergiant star Antares, marking the heart of Scorpius, is at the bottom of the triangle. To its upper right is Mars, and to its upper left is Saturn.
In the evening sky, you’ll be able to spot Mercury low in the west about 45 minutes after sunset. This fast-moving planet has its farthest angular separation from the Sun, what astronomers call greatest elongation, on April 18th. So if you’re never seen Mercury before, this is a good month to look for it. You’ll have a little help on April 8th, when a thin crescent Moon is in the same general area. Mercury is a little less than a fist from the Moon, to its right and a bit lower.
Meanwhile, Jupiter is high in the southeast at nightfall and unmistakably bright. The King of Planets is tangled up in the legs of Leo, the Lion. To Jupiter's upper right is Regulus, the Lion’s brightest star.
To get a personally guided tour of these night-sky sights and others overhead during April, download our 6½-minute-long astronomy podcast below.
There's no better guide to what's going on in nighttime sky than SkyWatch 2016, a yearlong guide prepared by the editors of Sky & Telescope magazine.
Volcanic wasteland or exotic, two-faced atmosphere? A new thermal map of this super-Earth exoplanet is puzzling astronomers.
Super-Earths may rule the galaxy, but boy are they weird. And 55 Cancri e, recently renamed Janssen, tops the charts in weirdness. At eight times Earth’s mass and twice its radius, this mostly rocky planet straddles the line between Earths and Neptunes. It zips around its Sun-like star in less than a day, a proximity that leaves its surface roughly 30 times hotter than Earth’s.
From the beginning, 55 Cancri e has had scientists proposing all kinds of bizarre theories: a planet-wide ocean, diamonds in its interior, and even active volcanoes riddling the surface. Now research published March 30th in the journal Nature adds another piece to the puzzle.55 Cancri e’s Sweltering Days and Nights
Brice-Olivier Demory (Cavendish Laboratory, UK) and colleagues basically used the Spitzer Space Telescope as night vision goggles, taking thermal images of the planet as it spun around its host star. The team collected 75 hours’ worth of observations in the span of a month in the summer of 2013.
55 Cancri e is tidally locked, which means the same side is always facing the stellar fire. And the first thing that jumps out of the data is that while 55 Cancri e’s nightside is hot (2000°F, or 1400K), its dayside is even hotter: 4400°F (2700K).
Never mind that the temperatures themselves would melt lead. (In fact, the dayside would even melt sapphires — but not diamonds.) It’s the difference between the two hemispheres that’s boggling astronomers’ minds. What it means is that either this planet has no atmosphere at all (after all, the Moon’s windless sphere has a 500°F difference between its day and night sides), or its atmosphere is curiously bad at recirculating heat.
Add to this conundrum the team’s second discovery: the hottest point on the planet is not directly in the middle of the star-facing side; it’s shifted a full 40 or so degrees east. That’s a big shift for a non-circulating atmosphere. If winds aren’t pushing the hot spot over, the authors propose that we may instead be seeing an eastward magma flow on the planet’s surface.Magma Flows or a Two-Faced Atmosphere?
That’s not as crazy as it sounds— magma isn’t a new concept for this planet. Last year, Demory and colleagues published a report that showed the planet’s dayside temperatures almost quadrupled over the span of a year. Unlike the thermal map they’re publishing today, those observations only occurred during transits and occultations, when the planet passed in front of and behind its host star. At the time, the authors suggested planet-spanning volcanic activity could have caused the change.
“The danger in science is that you start to become convinced by an explanation and then you forget everything else,” cautions Demory. “We try to be really as inclusive as possible and try to think about all possible explanations.”
And in the spirit of inclusivity, Demory and team suggest an alternative explanation for their new thermal map: a two-faced atmosphere. If there’s some chemical component that vaporizes on the dayside and rains out on the nightside, then it could still shift heat on the dayside but it won’t be available for the job on the opposite hemisphere, leaving the nightside notably cooler. In fact, theorists have already tried out such models using silicate-based clouds.
Blind Men Approaching the Elephant
But here’s another wrench to throw into the works. Just a couple weeks ago, I reported on a paper that Angelos Tsiaras (University of College, London) posted on the arXiv preprint server, now accepted for publication in Astrophysical Journal.
Tsiaras and colleagues pointed the Hubble Space Telescope at 55 Cancri e to measure its transmission spectrum, the wavelengths absorbed from the host star’s light as it passed through the planet’s outer atmosphere. Which wavelengths the atmosphere absorbs depends on its composition. This technique measures the atmosphere at the planet’s terminator, right at the border between day and night.
And, contrary to the implications of Demory’s paper, Tsiaras’s team found an atmosphere dominated by light elements such as hydrogen — an element that would have no problem moving heat from one side to another. But, Tsiaras notes, the team also found hints of other chemical components. These compounds, such as hydrogen cyanide, could affect how heat circulates.
Moreover, the transmission spectrum only samples the border between the hemispheres, and only the topmost parts of the atmosphere at that. So it’s not yet clear if we’re looking at contradictory observations or if this is just a case of blind men trying to understand the elephant.
Long story short: there are three different data sets tasting different parts of 55 Cancri e’s atmosphere, and none of them show exactly the same picture. There’s no single scenario yet that simultaneously explains the extreme changes on the planet’s dayside, the hydrogen-rich atmosphere at the terminator, and the wildly different day and night hemispheres reported in Nature today.
Suffice it to say, this story isn’t over yet!
Hidden within the subtle hues of the stars are the keys to their temperatures and compositions. Get acquainted with the classic OBAFGKM spectral sequence through real stars you can see on a spring night.
Color has always been a source of wonder for me. I recall the shimmery, refractive colors of my grandmother's rhinestone jewelry when I was a child. To this day, cut glass catching the sun still makes me ooh and aah. At night, stars substitute for rhinestones. Their colors may be more subtle, but they flare with the same clarity and fire.
When it comes to stars, color contains valuable information about temperature and composition. English chemist William Wollaston passed the Sun's light through a prism in 1802 and discovered it was crossed by fine, dark lines. He assumed they were natural boundaries between the colors. German optician Joseph Fraunhofer measured and cataloged 574 such lines in the early 1800s still known to this day as "Fraunhofer lines".
Not until the early 1860s, when English astronomer William Huggins matched some of the dark "absorption" lines in the Sun's spectrum with those in terrestrial substances, did astronomers come to understand that stars are composed of familiar materials, not some exotic fifth element, or quintessence, as Aristotle had thought.
Hot, dense objects like the tungsten filament in a light bulb or an electric stove burner give off every color of light and emit a line-free, continuous spectrum that looks like a rainbow. A star is likewise hot and dense and produces a continuous spectrum. But before that light reaches your eyes, it must pass through cooler, less dense gas in the star's outer layers. There, atoms in the gas absorb specific colors of light, leaving narrow gaps or lines in the spectrum.
Atoms and molecules in a star's outer envelope reveal their identity by the patterns of lines they produce. Every single element and compound produces its own unique set. Since nearly every star displays absorption lines, astronomers could use the patterns they saw in solar and stellar spectra as "fingerprints" to probe their composition.
Different stars show different spectra. Some have only faint lines, while others are missing chunks of color. By the late 19th century, astronomers were developing schemes to classify spectra The most prolific classifier, Annie Jump Cannon, worked as an assistant to Harvard College Observatory director, Edward C. Pickering, and created a catalog of 325,300 stellar spectra by the early 1920s. Simplifying earlier, more complicated schemes, Cannon divided stars into seven categories, each of which was assigned a letter.
Although not fully understood at the time, her prescient ordering classified stars according to their surface temperature, from the hottest blue-white supergiants to the coolest red dwarfs using this letter sequence: O B A F G K M.
To help us remember the order of this unpronounceable acronym, someone, possibly Cannon herself, proposed the mnemonic "Oh, be a fine girl, kiss me!", which has since morphed into the more egalitarian "Oh, be a fine girl/guy, kiss me!" If that doesn't suit you, consider these others found while trolling the Web:
Only bad astronomers feel good knowing mnemonics
Only boys accepting feminism get kissed meaningfully
Oh boy, another Ferengi getting Klingon money
Odysseus begged Athena for guidance killing many lusty Trojans (this one includes the new L and T dwarf classifications)
One brutal astronomer fought gnarly karate monsters
I could go on but ...
Another way to remember and appreciate the colors of the spectral classes is to get acquainted with the real stars behind the letters. The early spring sky offers up naked-eye stars of all seven spectral types. I've included two maps to help you find them. One shows all seven within the bounds of a single constellation, Orion. The other highlights only the brightest representatives across many constellations.
Temperatures across the classes range from 50,000K (90,000°F) for massive O stars like Alnitak in Orion's Belt to 5,780K (10,000°F) for the sun and down to 2,500K (4,000°F) for the coolest supergiants. As far as staying chill, Betelgeuse, with a surface temperature of around 3,200K (5,300°F), is the coolest, easily-visible star on early April evenings.
Each class is subdivided into 10 subclasses, numbered from 0 to 9 (our Sun is a G2 star with characteristics part-way between G and F). Further, temperature defines which atoms and molecules show up in a star's spectrum. In blazing O stars, searing heat ionizes helium, a very tough thing to do, since the gas holds its electrons tightly and is loathe to part with them. Spectra of cooler M stars are blanketed by familiar atomic absorption lines of "metals" (elements other than hydrogen and helium) and molecular lines from titanium oxide, carbon molecules, and even water.
All this you can see with your own eyes using a visual spectroscope. I have a Rainbow Optics model that does a great job showing the classic hydrogen Balmer line absorptions in Sirius and Vega (A-stars) and the lush banding in Betelgeuse. When you realize you're seeing the internal workings of atoms hundreds of light years away, it almost feels like touching a star.
Rhinestones. The wonder of color goes deeper than we ever imagined.
The post Comet C/2013 US10 (Catalina) in the open cluster NGC 1545 appeared first on Sky & Telescope.
Two amateur videos shot early on March 17th show a brief but bright flash on the edge of Jupiter's disk. Did the King of Planets get whacked again?
Right now amateur and professional planet watchers around the world are trying to pin down the specifics of an apparent impact on Jupiter back on March 17th. Only within the past few days have two videos emerged showing a brief flash of light right on the edge of Jupiter's disk, near the boundary of the planet's bright Equatorial Zone and its tawny North Equatorial Belt.
Gerrit Kernbauer of Mödling, Austria, posted the first video of the event. "I was observing and filming Jupiter with my Skywatcher Newton 200/1000 Telescope [an 8-inch f/5 reflector]," he recalls. "The seeing was not the best, so I hesitated to process the videos. Nevertheless, 10 days later I looked through the videos and I found this strange light spot that appeared for less than one second on the edge of the planetary disc."
Two days later, Irish observer John McKeon posted his own record of the flash. McKeon was using an 11-inch Schmidt-Cassegrain telescope and ASI120MM camera in Swords, a Dublin suburb. Crucially, he also used a near-infrared filter to reduce the planet's brightness. He was making a 3½-hour-long time-lapse video of Jupiter and its moons, "with a happy coincidence of the impact in the second-to-last capture of the night."
Now planetary imaging specialist Marc Delcroix has obtained the raw videos, processed them to bring out extra detail, and refined the circumstances of the flash. He finds that the brightening lasted just over 1 second. But the timing is off a bit: in Kernbauer's video the flash began at 00:18:35 UT, whereas in McKeon's the onset is 9 seconds later.
Despite the time mismatch, the event appears to be real. Apparently the impacting object, be it an asteroid or comet, was rather small. "Nobody sees any debris field associated with that part of the atmosphere," notes Glenn Orton (Jet Propulsion Laboratory). Apparently mission managers decided against slewing the Hubble Space Telescope around to take a quick look.
But March 17th's impact, if the evidence for it holds up, becomes the fifth such event in the past decade. The largest of these occurred July 19, 2009, and it left a distinctly dark "powder burn" in Jupiter's upper atmosphere first spotted by Australian astro-imager Anthony Wesley.
That was followed by three lesser strikes on June 3, 2010 (recorded independently by Wesley and Christopher Go); on August 10, 2010 (independently seen by Masayuki Tachikawa and Kazuo Aoki); and on September 10, 2012 (seen visually by Dan Petersen and independently recorded by George Hall).
Counting the historic multiple-hit crash of Comet Shoemaker-Levy 9 in July 1994, that's a grand total of six impacts on Jupiter in the past 22 year — with five of those in the past decade! And yet, a statistical analysis of these strikes suggests that they happen pretty much all the time. Ricardo Hueso (University of the Basque Country, Spain) and colleagues estimate that objects with diameters 5 to 20 meters across, as these impactors likely were, should collide with Jupiter anywhere from once to five times per month.
At first, there was some speculation that the March 17th flash was somehow linked to Jupiter's close-in moon Amalthea, which was positioned close to where the flash occurred. But that notion has since been ruled out.
For one thing, Delcroix's analysis puts the flash location at a latitude of +12.4°, well north of where Amalthea would have been (and clearly within the NEB). Moreover, "The flash was very like previous impacts into the atmosphere of Jupiter," notes John Rogers, who head the Jupiter observing section of the British Astronomical Association, "and as Jupiter is a much bigger target than Amalthea, it is much more likely to have been on Jupiter."
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