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aamukherjee A Slice of Entropie -
alchymista Alchymista -
crownedrose Fading Like A Dead Star -
expose-the-light Quarks to Quasars -
kenobi-wan-obi CWL -
abluegirl A Blue Girl -
perscientiamlibertas A Matter of the Most Pleasant Fraternal Confidence
Comet Hale-Bopp by hshdude
“The great comet of 1997 through a 50mm lens. Check out the white dust and blue plasma tails!”
kenobi-wan-obi
A cosmic grain of sand left the long and colorful trail across this all-sky view. Its grazing impact with planet Earth’s atmosphere began at 71 kilometers per second.
Image Credit & Copyright: Stéphane Vetter (Nuits sacrees)
With the Milky Way stretching from horizon to horizon, the scene was captured on the night of November 17 from the astronomically popular high plateau at Champ du Feu in Alsace, France. Of course, the earthgrazer meteor belongs to this month’s Leonid meteor shower, produced as our fair planet annually sweeps through dust from the tail of periodic Comet Tempel-Tuttle.
The shower’s radiant point in the constellation Leo is very close to the eastern horizon, near the start of the trail at the lower left. Bright planet Jupiter is also easy to spot, immersed in a faint band of Zodiacal light just below and right of center. The image is part of a dramatic time-lapse video (vimeo here) that began only 7 minutes before the long leonid crossed the sky.
“Once in a Civilization” Comet to Zip past Earth Next Year
As it flares out of the distant Oort Cloud, the newly discovered comet C/2012 S1 (ISON) appears to be heading on a trajectory that could make for one of the most spectacular night-sky events in living memory. Why is this comet expected to be so unique? Two reasons:
Astronomers predict that the comet will pass just 1.16 million miles from the Sun as it swings around its perihelion, or closest approach. (This may seem like a lot, but remember—the Sun is big. If we were to scale the Sun down to the size of Earth, the comet would pass well within the orbits of dozens of satellites.) The close approach will melt enormous amounts of the comet’s ice, releasing dust and gas and forming what should be a magnificent tail.After it loops around the Sun and forms this tail, the comet should then pass relatively close to Earth—not near enough to cause any worry, but close enough to put on a great show. Viewers in the Northern Hemisphere will get the best view as the comet blooms in the weeks approaching Christmas 2013.
The comet could grow as bright as the full moon.
Read More here
As a follow-up to my previous post about watching golfballs hit the moon at 100,000 miles an hour, here’s a guide to the Perseids and how to enjoy them.
- What are the Perseids? They are particles shed by Comet 109P/Swift-Tuttle, a periodic comet that last passed near Earth in 1992. Composed of mostly silicate minerals, the typical meteor particle, or meteoroid, is about the size of a grain of sand. The motion of the Earth through its orbit carries us toward “streams” of these particles left behind in the comet’s wake; our relative motion toward them makes the particles encounter the Earth at a relative velocity of tens to hundreds of thousands of miles per hour. They meet the upper atmosphere and vaporize as they reach temperatures of thousands of degrees for a few brief seconds; we see their remnants as bright streaks of light commonly known as “shooting stars”. The Perseid shower is one of the year’s more notable events, leading sometimes to hundreds of meteors per hour being seen.
(Comet Swift-Tuttle in 1992. Credit & copyright: Chris Cook, 2002)
- How often do they happen? The Perseids are an annual event each August, and has been happening at least since antiquity. Last seen exactly 150 years ago during the Civil War, Swift-Tuttle was somewhat considered “lost” because its observations in 1862 were not sufficiently precise to nail down its orbit. The comet “announced” its coming return to the inner solar system during the 1991 Perseid shower with a huge burst of activity during the early morning hours over East Asia. Speculation as to whether this feature represented material recently shed by the comet was well founded; the comet re-appeared in Earth’s skies about a year later. Each time the comet returns, a new stream of particles is shed and the shower is replenished.
- Why are meteors important? There’s a lot of science involved. So many comets have come and gone over the history of the solar system that the inner part is chock full of dust particles. These particles constantly rain down on the Earth and other terrestrial planets, bringing many tons of cosmic material per year; early in the solar system’s history, this may have included the essential components needed in the chemistry of life. The particles are thought to be relatively pristine, in the sense that they avoided the thermal shocks and chemical mixing that occurred in the solar nebula. So a meteor seen streaking across our skies is a glowing messenger from the earliest times of our planetary system, telling us what conditions were like then.
- Do I need a telescope to observe the Perseids? Nope! Meteor showers are a phenomenon requiring no special equipment at all; in fact, binoculars and telescopes allow views of such relatively small parts of the sky that they’re mostly ineffective for meteor observing. Rather, showers like the Perseids contain many larger particles, which make for brighter meteors, and the best instruments to observe them are unaided human eyeballs. Our eyes are pretty sensitive once dark adaptation has occurred, and we can see a very large area of sky at a time with them, increasing the chances of seeing meteors.
- When should I look for Perseid meteors? The shower peaks in intensity around August 11-13, so it’s going on right now — even during daylight hours. However, for nighttime observing, the hours between midnight and dawn are best, because of the relative speed difference between the meteors and the Earth. Before midnight, we’re facing away from the direction the Earth moves in its orbit around the Sun, so to be seen the meteors have to “catch up” to us. After midnight, we’re facing the direction of motion and the relative speeds are highest. Speed correlates with meteor brightness (for a given particle size), so you’re likely after midnight to see fainter meteors as a result.
- What part of the sky should I look toward? The Perseids can be seen in any part of the sky, but they appear to “radiate” from a point in the constellation Perseus. In August, that constellation is rising in the northeastern sky toward midnight in the Northern Hemisphere. So facing northeast aligns the observer with the direction from which the meteors appear to originate and increases the chances they’ll be seen before burning out. Also, choice of seating is important, and a reclining lawn or lounge chair is highly recommended. Staring upwards for hours at a time is otherwise rough on the neck muscles!
(Image credit: accuweather.com)
- What can I expect to see? In an average year, observers can typically expect about one meteor per minute during the shower’s peak. The rate is somewhat variable, and at times several will be seen per minute. The Perseid shower is known for lots of bright, slow-moving fireballs, some of which explode at the end of their travel in a “terminal burst”. At times these fireballs are bright enough to cast shadows on the ground. There is rarely obvious color in meteors, but the Perseids tend toward a pale yellow, possibly due to emission of light from ionized sodium atoms. The Perseids, one of the most reliable meteor showers of the year, rarely fail to impress!
- Will the Moon be a problem? Yes and no. This year’s shower peaks a few days after the Moon is at last quarter, meaning two things: (1) The early part of the night will be Moon-free, and (2) After the Moon rises, it will present some interference. Moonlight adds to the sky background, making the faintest Perseids difficult to see. But don’t worry — the brightest meteors will easily outshine this light. The main tip here is to not look in the direction of the Moon, to keep its light from ruining one’s dark adaptation. One of the best tricks is to keep the Moon behind some obstruction, like a building or a tree, while maintaining a clear view to the northeast. Remaining in shadow will minimize the interference.
- Are my observations useful? Yes! Meteor watching is a great citizen-science opportunity. Meteor science still relies on boots-on-the-ground observations from people, many of whom are amateur astronomers and other interested skywatchers. Ways to participate can be found here, here and here. Having multiple people at one observing site helps in collecting observations, since several individuals can cover more of the sky at once than one person. But one person can still see a lot of sky, and solo observations are quite useful.
- Finally, stay warm, as the predawn hours in August can be cold in many parts of the Northern Hemisphere. My meteor watching inevitably involves a thermos of hot coffee to help ward of the chill and drowsiness.
Good luck! And let us know what you see!Additional resources:
- Sky and Telescope: “Here Come The Perseids!”
- The International Meteor Organization (IMO) Perseid page
- The North American Meteor Network (NAMN) star charts for recording meteor observations
- MeteorObs: An internet forum for meteor observers of all levels
- StarDate: “Perseid Meteors Pierce The August Sky”
(via project-argus)
Lovejoy & Galaxies
Comet Lovejoy (C/2011 W3) is photographed in the morning sky above Andes, near Santiago de Chile.
March 30, 240 B.C.: Comet Cometh to Cathay
Photo: Halley’s Comet passes in front of the Milky Way near its 1986 perihelion. Image: Kuiper Airborne Observatory/NASA
240 B.C. Chinese astronomers observe a new broom-shaped “star” in the sky. It’s the first confirmed sighting of Halley’s Comet.
Some have made the case that a sighting in the third millennium B.C. is responsible for the alignment of the Sphinx and the pyramids of Giza. Interesting. Even a supposed Chinese sighting in 613 B.C. would be seven years later than the calculated 620 B.C. for a Halley’s passage. Was that a record-keeping error or a different comet?
The 240 B.C. observation coincides with Halley’s computed orbit, but its exact date is a matter of some imprecision. The existing Chinese record is the Records of the Grand Historian, or Shiji (or Shi Chi), written more than a century later around 100 B.C. What the Chinese called a “broom star,” because of its bristly tail, appeared first in the east and then later in the north.
crownedrose
The comet Lulin
The Comet Lulin, otherwise known as C/2007 N3, is seen here as it approached Earth in February 2009. It’s named for the Lulin Observatory in Taiwan, where astronomers first spotted the comet in 2008. Here it is observed by NASA’s Swift satellite. Astronomers believe that many comets come from the Oort Cloud, “a vast, extremely distant, spherical shell of icy bodies surrounding the solar system.” The Oort Cloud is a sort of borderlands in space, where our sun is too distant to invoke a strong gravitational pull on the objects. The Oort Cloud is believed to contain 0.1 to 2 trillion icy bodies in solar orbit, according to NASA. It is believed that tidal interactions from a passing star or the Milky Way itself can shift the contents of the Oort Cloud and in turn throw comets off their usual paths.
(via expose-the-light)
expose-the-light
Hale-Bopp & Dancing Aurora
by David Malin
The Great Comet of 1997, Hale-Bopp, appears besides dancing aurora over forest landscape in Canada.
Garradd in Motion
Comet Garradd passing along (August 2nd) through the Bar Galaxy PGC67040. Two other smaller galaxies (mid tail area) are also shown in this region.
by Efrain Morales
West Was The Best
by Doug Zubenel
The Great Comet of 1976, discovered by Richard West of the European Southern Observatory, blazed in the pre-dawn skies of early March, 1976. Here it is seen rising over the farmlands of northwestern Ohio near the town of Delphos.
