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Skywatch: Venus and Jupiter continue to accentuate the night heavens

February 28, 2015 / / 0 Comments


Venus (right) & Jupiter


Excerpt from washingtonpost.com
By Blaine Friedlander Jr. 
In winter’s waning weeks, Venus and Jupiter continue to accentuate the night heavens, we change our clocks forward and we grab spring with no intention of letting go.

Check the west-southwestern heavens at dusk to spy the vivacious Venus and the dim Mars. In late February, the two planets met for a sweet cosmic waltz, but in March, they appear to separate. Venus approaches negative fourth magnitude (very bright) while Mars makes do at magnitude 1.3 (dim, hard to find in urban light pollution). With a clear sky, Mars looks like a red pinpoint. 

A young, waxing crescent moon visits Mars on the evening of March 21, and on the next evening the crescent flirts with Venus.
Robust Jupiter ascends the evening’s eastern sky. Find this gas giant at a -2.5 magnitude, very bright, in the constellation Cancer. The lion in the constellation Leo appears to stare at the planet. By the Ides of March, find it south around 10:30 p.m. 

The waxing gibbous moon drops by the dazzling Jupiter on March 2, days before the moon itself becomes full on March 5. 

Catch the ringed Saturn rising after midnight in the east-southeast now, hanging out near a gang of constellations, Scorpius, Ophiuchus and Libra. It’s a zero magnitude object, bright enough that it can be seen under urban skies. The waning moon loiters near Saturn before dawn on March 12. On that morning, the reddish star below them is Antares.
We adjust our clocks to Daylight Saving Time at 2 a.m. March 8. Spring forward, moving the clock ahead one hour. 

Winter is almost over. Spring is weeks away. The vernal equinox brings spring’s official arrival on March 20 at 6:45 p.m. 

Also on March 20 — the day a new moon — the North Atlantic and the Arctic waters get a short total eclipse. We won’t see it here, but Slooh.com will carry it live. Totality will start seconds after 5:44 a.m. and end at 5:47 a.m., according to Geoff Chester of the U.S. Naval Observatory. 

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What Would It Be Like to Live on Mercury?

February 24, 2015 / / 0 Comments


Mercury With Subtle Colors
Mercury's extreme temperatures and lack of an atmosphere would make it very difficult, if not impossible, for people to live on the planet. Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington


Excerpt from  space.com
By Joseph Castro, Space.com Contributor


Have you ever wondered what it might be like to homestead on Mars or walk on the moons of Saturn? So did we. This is the first in Space.com's 12-part series on what it might be like to live on or near planets in our solar system, and beyond. Check back each week for the next space destination.
With its extreme temperature fluctuations, Mercury is not likely a planet that humans would ever want to colonize. But if we had the technology to survive on the planet closest to the sun, what would it be like to live there?

To date, only two spacecraft have visited Mercury. The first, Mariner 10, conducted a series of Mercury flybys in 1974, but the spacecraft only saw the lit half of the planet. NASA's MESSENGER spacecraft, on the other hand, conducted flybys and then entered Mercury's orbit — in March of 2013, images from the spacecraft allowed scientists to completely map the planet for the first time.



MESSENGER photos of Mercury show that the planet has water ice at its poles, which sit in permanent darkness. Mining this ice would be a good way to live off the land, but setting up bases at the poles might not be a good idea, said David Blewett, a participating scientist with the Messenger program.

"The polar regions would give you some respite from the strength of the sun on Mercury," Blewett told Space.com. "But, of course, it's really cold in those permanently shadowed areas where the ice is, and that presents its own challenge."

A better option, he said, would probably be to set up a home base not far from one of the ice caps, perhaps on a crater rim, and have a water mining operation at the pole.

Still, dealing with extreme temperatures on Mercury would likely be unavoidable: Daytime temperatures on the planet can reach 800 degrees Fahrenheit (430 degrees Celsius), while nighttime temperatures can drop down to minus 290 degrees Fahrenheit (minus 180 degrees Celsius).

Scientists once believed Mercury was tidally locked with the sun, meaning that one side of the planet always faces the sun because it takes the same amount of time to rotate around its axis as it does to revolve around the star. But we now know that Mercury's day lasts almost 59 Earth days and its year stretches for about 88 Earth days.

Interestingly, the sun has an odd path through the planet's sky over the course of Mercury's long day, because of the interaction between Mercury's spin rate and its highly elliptical orbit around the sun.

"It [the sun] rises in the east and moves across the sky, and then it pauses and moves backwards just a tad. It then resumes its motion towards the west and sunset," said Blewett, adding that the sun appears 2.5 times larger in Mercury's sky than it does in Earth's sky.

And during the day, Mercury's sky would appear black, not blue, because the planet has virtually no atmosphere to scatter the sun's light. "Here on Earth at sea level, the molecules of air are colliding billions of times per second," Blewett said. "But on Mercury, the atmosphere, or 'exosphere,' is so very rarefied that the atoms essentially never collide with other exosphere atoms." This lack of atmosphere also means that the stars wouldn't twinkle at night.



Without an atmosphere, Mercury doesn't have any weather; so while living on the planet, you wouldn't have to worry about devastating storms. And since the planet has no bodies of liquid water or active volcanoes, you'd be safe from tsunamis and eruptions.

But Mercury isn't devoid of natural disasters. "The surface is exposed to impacts of all sizes," Blewett said. It also may suffer from earthquakes due to compressive forces that are shrinking the planet (unlike Earth, Mercury doesn't have tectonic activity).

Mercury is about two-fifths the size of Earth, with a similar gravity to Mars, or about 38 percent of Earth's gravity. This means that you could jump three times as high on Mercury, and heavy objects would be easier to pick up, Blewett said. However, everything would still have the same mass and inertia, so you could be knocked over if someone threw a heavy object at you, he added.

Finally, you can forget about a smooth Skype call home: It takes at least 5 minutes for signals from Mercury to reach Earth, and vice versa.

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Earth’s Moon May Not Be Critical to Life Afterall

February 19, 2015 / / 0 Comments




Excerpt from space.com

 The moon has long been viewed as a crucial component in creating an environment suitable for the evolution of complex life on Earth, but a number of scientific results in recent years have shown that perhaps our planet doesn't need the moon as much as we have thought.

In 1993, French astronomer Jacques Laskar ran a series of calculations indicating that the gravity of the moon is vital to stabilizing the tilt of our planet. Earth's obliquity, as this tilt is technically known as, has huge repercussions for climate. Laskar argued that should Earth's obliquity wander over hundreds of thousands of years, it would cause environmental chaos by creating a climate too variable for complex life to develop in relative peace.
So his argument goes, we should feel remarkably lucky to have such a large moon on our doorstep, as no other terrestrial planet in our solar system has such a moon. Mars' two satellites, Phobos and Deimos, are tiny, captured asteroids that have little known effect on the Red Planet. Consequently, Mars' tilt wobbles chaotically over timescales of millions of years, with evidence for swings in its rotational axis at least as large as 45 degrees. 


The stroke of good fortune that led to Earth possessing an unlikely moon, specifically the collision 4.5 billion years ago between Earth and a Mars-sized proto-planet that produced the debris from which our Moon formed, has become one of the central tenets of the 'Rare Earth' hypothesis. Famously promoted by Peter Ward and Don Brownlee, it argues that planets where everything is just right for complex life are exceedingly rare.

New findings, however, are tearing up the old rule book. In 2011, a trio of scientists — Jack Lissauer of NASA Ames Research Center, Jason Barnes of the University of Idaho and John Chambers of the Carnegie Institution for Science — published results from new simulations describing what Earth's obliquity would be like without the moon. What they found was surprising.

"We were looking into how obliquity might vary for all sorts of planetary systems," says Lissauer. "To test our code we began with integrations following the obliquity of Mars and found similar results to other people. But when we did the obliquity of Earth we found the variations were much smaller than expected — nowhere near as extreme as previous calculations suggested they would be."
Lissauer's team found that without the moon, Earth's rotational axis would only wobble by 10 degrees more than its present day angle of 23.5 degrees. The reason for such vastly different results to those attained by Jacques Laskar is pure computing power. Today's computers are much faster and capable of more accurate modeling with far more data than computers of the 1990s.

Lissauer and his colleagues also found that if Earth were spinning fast, with one day lasting less than 10 hours, or rotating retrograde (i.e. backwards so that the sun rose in the West and set in the East), then Earth stabilized itself thanks to the gravitational resonances with other planets, most notably giant Jupiter. There would be no need for a large moon. 

Earth's rotation has not always been as leisurely as the current 24 hour spin-rate. Following the impact that formed the moon, Earth was spinning once every four or five hours, but it has since gradually slowed by the moon's presence. As for the length of Earth's day prior to the moon-forming impact, nobody really knows, but some models of the impact developed by Robin Canup of the Southwest Research Institute, in Boulder, Colorado, suggest that Earth could have been rotating fast, or even retrograde, prior to the collision.

Tilted Orbits
Planets with inclined orbits could find that their increased obliquity is beneficial to their long-term climate – as long as they do not have a large moon.


"Collisions in the epoch during which Earth was formed determined its initial rotation," says Lissauer. "For rocky planets, some of the models say most of them will be prograde, but others say comparable numbers of planets will be prograde and retrograde. Certainly, retrograde worlds are not expected to be rare."

The upshot of Lissauer's findings is that the presence of a moon is not the be all and end all as once thought, and a terrestrial planet can exist without a large moon and still retain its habitability. Indeed, it is possible to imagine some circumstances where having a large moon would actually be pretty bad for life.

Rory Barnes, of the University of Washington, has also tackled the problem of obliquity, but from a different perspective. Planets on the edge of habitable zones exist in a precarious position, far enough away from their star that, without a thick, insulating atmosphere, they freeze over, just like Mars. Barnes and his colleagues including John Armstrong of Weber State University, realized that torques from other nearby worlds could cause a planet's inclination to the ecliptic plane to vary. This in turn would result in a change of obliquity; the greater the inclination, the greater the obliquity to the Sun. Barnes and Armstrong saw that this could be a good thing for planets on the edges of habitable zones, allowing heat to be distributed evenly over geological timescales and preventing "Snowball Earth" scenarios. They called these worlds "tilt-a-worlds," but the presence of a large moon would counteract this beneficial obliquity change.

"I think one of the most important points from our tilt-a-world paper is that at the outer edge of the habitable zone, having a large moon is bad, there's no other way to look at it," says Barnes. "If you have a large moon that stabilizes the obliquity then you have a tendency to completely freeze over."

Barnes is impressed with the work of Lissauer's team.
"I think it is a well done study," he says. "It suggests that Earth does not need the moon to have a relatively stable climate. I don't think there would be any dire consequences to not having a moon."

Mars' Changing Tilt
The effects of changing obliquity on Mars’ climate. Mars’ current 25-degree tilt is seen at top left. At top right is a Mars that has a high obliquity, leading to ice gather at its equator while the poles point sunwards. At bottom is Mars with low obliquity, which sees its polar caps grow in size.


Of course, the moon does have a hand in other factors important to life besides planetary obliquity. Tidal pools may have been the point of origin of life on Earth. Although the moon produces the largest tides, the sun also influences tides, so the lack of a large moon is not necessarily a stumbling block. Some animals have also evolved a life cycle based on the cycle of the moon, but that's more happenstance than an essential component for life.

"Those are just minor things," says Lissauer.

Without the absolute need for a moon, astrobiologists seeking life and habitable worlds elsewhere face new opportunities. Maybe Earth, with its giant moon, is actually the oddball amongst habitable planets. Rory Barnes certainly doesn't think we need it.
"It will be a step forward to see the myth that a habitable planet needs a large moon dispelled," he says, to which Lissauer agrees.
Earth without its moon might therefore remain habitable, but we should still cherish its friendly presence. After all, would Beethoven have written the Moonlight Sonata without it?

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Scientists find oddly behaving ‘inner-inner core’ at Earth’s center

February 11, 2015 / / 0 Comments

Excerpt from cnet.com Though the seismic waves from earthquakes are best known for their destructive abilities, in the hands of geologists, they can be powerful tools of discovery. A research team at the University of Illinois (UI) has just used th...

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How Would the World Change If We Found Alien Life?

February 8, 2015 / / 0 Comments







Excerpt from space.com
By by Elizabeth Howell

 In 1938, Orson Welles narrated a radio broadcast of "War of the Worlds" as a series of simulated radio bulletins of what was happening in real time as Martians arrived on our home planet. The broadcast is widely remembered for creating public panic, although to what extent is hotly debated today.

Still, the incident serves as an illustration of what could happen when the first life beyond Earth is discovered. While scientists might be excited by the prospect, introducing the public, politicians and interest groups to the idea could take some time.

How extraterrestrial life would change our world view is a research interest of Steven Dick, who just completed a term as the Baruch S. Blumberg NASA/Library of Congress Chair of Astrobiology. The chair is jointly sponsored by the NASA Astrobiology Program and the John W. Kluge Center, at the Library of Congress. 


Dick is a former astronomer and historian at the United States Naval Observatory, a past chief historian for NASA, and has published several books concerning the discovery of life beyond Earth. To Dick, even the discovery of microbes would be a profound shift for science.

"If we found microbes, it would have an effect on science, especially biology, by universalizing biology," he said. "We only have one case of biology on Earth. It's all related. It's all DNA-based. If we found an independent example on Mars or Europa, we have a chance of forming a universal biology."

Dick points out that even the possibilities of extraterrestrial fossils could change our viewpoints, such as the ongoing discussion of ALH84001, a Martian meteorite found in Antarctica that erupted into public consciousness in 1996 after a Science article said structures inside of it could be linked to biological activity. The conclusion, which is still debated today, led to congressional hearings.

"I've done a book about discovery in astronomy, and it's an extended process," Dick pointed out. "It's not like you point your telescope and say, 'Oh, I made a discovery.' It's always an extended process: You have to detect something, you have to interpret it, and it takes a long time to understand it. As for extraterrestrial life, the Mars rock showed it could take an extended period of years to understand it."


ALH84001 Meteorite
The ALH84001 meteorite, which in a 1996 Science publication was speculated to be host to what could be ancient Martian fossils. That finding is still under dispute today.

Mayan decipherments

In his year at the Library of Congress, Dick spent time searching for historical examples (as well as historical analogies) of how humanity might deal with first contact with an extraterrestrial civilization. History shows that contact with new cultures can go in vastly different directions.

Hernan Cortes' treatment of the Aztecs is often cited as an example of how wrong first contact can go. But there were other efforts that were a little more mutually beneficial, although the outcomes were never perfect. Fur traders in Canada in the 1800s worked closely with Native Americans, for example, and the Chinese treasure fleet of the 15th Century successfully brought its home culture far beyond its borders, perhaps even to East Africa.

Even when both sides were trying hard to make communication work, there were barriers, noted Dick.

"The Jesuits had contact with Native Americans," he pointed out. "Certain concepts were difficult, like when they tried to get across the ideas of the soul and immortality."



A second look by the Mars Global Surveyor at the so-called Viking “Face on Mars” in Cydonia revealed a more ordinary-looking hill, showing that science is an extended process of discovery.


Indirect contact by way of radio communications through the Search for Extraterrestrial Intelligence (SETI), also illustrates the challenges of transmitting information across cultures. There is historical precedence for this, such as when Greek knowledge passed west through Arab translators in the 12th Century. This shows that it is possible for ideas to be revived, even from dead cultures, he said.

It's also quite possible that the language we receive across these indirect communications would be foreign to us. Even though mathematics is often cited as a universal language, Dick said there are actually two schools of thought. One theory is that there is, indeed, one kind of mathematics that is based on a Platonic idea, and the other theory is that mathematics is a construction of the culture that you are in. 

"There will be a decipherment process. It might be more like the Mayan decipherments," Dick said.


The ethics of contact

As Dick came to a greater understanding about the potential c impact of extraterrestrial intelligence, he invited other scholars to present their findings along with him. Dick chaired a two-day NASA/Library of Congress Astrobiology Symposium called "Preparing for Discovery," which was intended to address the impact of finding any kind of life beyond Earth, whether microbial or some kind of intelligent, multicellular life form.

The symposium participants discussed how to move beyond human-centered views of defining life, how to understand the philosophical and theological problems a discovery would bring, and how to help the public understand the implications of a discovery.

"There is also the question of what I call astro-ethics," Dick said. "How do you treat alien life? How do you treat it differently, ranging from microbes to intelligence? So we had a philosopher at our symposium talking about the moral status of non-human organisms, talking in relation to animals on Earth and what their status is in relation to us."

Dick plans to collect the lectures in a book for publication next year, but he also spent his time at the library gathering materials for a second book about how discovering life beyond Earth will revolutionize our thinking.

"It's very farsighted for NASA to fund a position like this," Dick added. "They have all their programs in astrobiology, they fund the scientists, but here they fund somebody to think about what the implications might be. It's a good idea to do this, to foresee what might happen before it occurs."

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Jupiter Wins the Starring Role in February’s Planet Parade

February 6, 2015 / / 0 Comments

Excerpt from nbc.com Planets are on parade in February's night sky. Giant Jupiter will dazzle all nig...

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Jupiter at its biggest, brightest for two weeks

February 3, 2015 / / 0 Comments

Excerpt from pressofatlanticcity.comBy FRED SCHAAF  ...

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The Mystery of the Ghost Ship Lunatic

January 27, 2015 / / 0 Comments

The Lunatic Piran found abandoned Jure Stwerk at the Helm           ...

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4 Sky Events This Week: Inner Planets Dance While Saturn Dazzles

January 12, 2015 / / 0 Comments


Illustration of moon pairing with star in the Virgo constellation
The moon pairs with the brightest star in the constellation Virgo on Tuesday.
Illustration by A.Fazekas, SkySafari


Excerpt from news.nationalgeographic.com

An eclipse of a volcanic moon by the king of planets, Jupiter, will thrill stargazers this week, as Earth's moon rides above the ringed world, Saturn.

Moon meets Maiden. On Tuesday, January 13, early birds will enjoy a particularly close encounter with the last quarter moon of the month and with the bright star Spica. All the action takes place in the constellation Virgo, the Maiden, halfway up the southern sky at dawn.

The 250-light-year-distant star appears only 2 degrees below the moon, a distance equal to about the width of your thumb held at arm's length.

It's amazing to realize that the light from Spica left on its journey to Earth back in 1765. That's the year that Great Britain passed the Stamp Act, the first direct tax levied on the American colonies and a prelude of the parliamentary oversteps that led to the American Revolution.

Mercury at its best. Look for faint Mercury about a half-hour after sunset on Wednesday, January 14, just above the southwestern horizon.

The innermost planet will appear at its farthest point away from the sun, a moment called the greatest elongation. Sitting 19 degrees east of the sun, it would be challenging to track down its faint point of light if it weren't for the nearby, superbright Venus.

The planetary duo will appear only 1.3 degrees apart, making the pair particularly impressive when viewed through binoculars or a small telescope. Look carefully and you may notice that Mercury appears to be a miniature version of the half-lit moon...

Illustration of Venus and Mercury in close conjunction in the southwest sky
This skychart shows Venus and Mercury in close conjunction in the southwest sky after sunset on Wednesday.
Illustration by A.Fazekas, SkySafari

Volcanic moon eclipse. Sky-watchers armed with telescopes will witness a distant eclipse of Jupiter's moon Io in the early morning hours of Friday, January 16.

At 12:27 a.m. EST, the gas giant's own shadow will glide across the tiny disk of the volcanic moon, which will be visible to the west of the planet.

Also early on Thursday night at 10:56 p.m. EST, Jupiter's massive storm, the Great Red Spot, crosses the middle of the planet's disk. Appearing as an orange-pink oval structure, this hurricane circles the planet every 12 hours or so and is three times larger than the Earth. 

Illustration of Jupiter in the late night southwest sky
This wide-angle skychart shows the location of Jupiter in the southeast sky on Thursday evening and early morning Friday. The insert telescope view shows Jupiter and location of its moon Io just before it enters the planet’s shadow.
Illustration by A.Fazekas, SkySafari
Luna and Saturn. Later on, near dawn on Friday, January 16, the waning crescent moon will appear to park itself just 2 degrees north of Lord of the Rings.

The ringed world can't be missed with the naked eye since it is the brightest object visible in the southeastern predawn sky. Its proximity to the moon will make it that much easier to identify.
Train a telescope on this yellow-tinged point of light, and it will readily reveal its stunning rings, tilted a full 25 degrees toward Earth. Currently Saturn sits nearly 994,000 miles (1.6 billion kilometers) away from Earth, which means that the reflected sunlight off its cloud tops takes 87.4 minutes to reach our eyes.
Happy hunting!

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CIA: All Those 1950s UFO Sightings? ‘It Was Us’

January 4, 2015 / / 0 Comments

Excerpt from usatoday.comMaybe it was a bird. Maybe it was a plane.But it was probably not a UFO.The Central Intelligence Agency had some fun Monday tweeting out its most popular stories of the year.No. 1? "Reports of unusual activity in the skies in t...

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First Weekend of the New Year Brings Quadrantid Meteor Shower

January 3, 2015 / / 0 Comments







Excerpt from savingadvice.com


For those who want to save money, one of the best free resources available to everyone are nature’s displays. The first weekend of the New Year will begin with a bang, although this bang will be of interstellar origins. This weekend (Jan. 3), the first meteor display of 2015 will reach its peak on Saturday night in a display of lights known as the Quadrantid meteor shower. According to science reporter Geoff Gaherty, “Meteor shows are usually named after the constellation in the sky where their radiant is located: the point in the sky from which they appear to radiate. Thus, the Perseids [showers] are named for Perseus and the Geminids [showers] are named for Gemini.”

Interestingly, Gaherty informs the reader that “there is no constellation named Quadrans” whence scientists derived the name Quadrantid. Instead, there was once the Quadrans Muralis constellation, which became a part of the constellation Bootes in 1922. The name of the meteor, however, was retained.

Quadrantids are also known to be a January meteor shower, as opposed to the more famous Perseids observed in August or the Geminids seen in December. Additionally, quadrantid meteors are less frequently observed than the other two meteor showers given that its peak intensity lasts only hours. Still, Gaherty writes that the Quadrantid shower “can produce as many bright meteors during its peak as the more famous Perseids.” Thus, in order to view this spectacular display, “timing is everything.”

Using past observations, researchers predict that the peak of 2015′s Quadrantid meteor shower will occur at 9 p.m. EST on Jan. 3. “During this time, the radiant will be close to the northern horizon and there is a good chance of seeing…meteors coming in close to the horizon to the east and west.”

The radiant, however, is expected to rise higher in the northeastern sky, until more meteors become visible in the east. According to Gaherty, the best time to then observe the Quadrantids will be between midnight and 2 a.m. (some reports say dawn) in the Northern Hemisphere.

Unfortunately, the shooting stars may be hard to view because of an almost-full moon on Saturday, which will radiate its own impressive brightness. Still, NASA predicts that at the peak of the Quadrantid shower, approximately 80 meteors an hour will be released, which should be remarkable in its own right.

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THE SONS OF GOD ~ A Lecture by Biblical Scholar Michael Heiser

January 3, 2015 / / 0 Comments

Mike Heiser is a scholar in the fields of biblical studies and the ancient Near East. He is the Academic Editor of Logos Bible Software. Mike earned the M.A. and Ph.D. in Hebrew Bible and Semitic Languages at the University of Wisconsin-Madison in 2...

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Must-See Geminid Meteor Shower Peaks This Weekend: An Observer’s Guide

December 16, 2014 / / 0 Comments



2014 Geminid Meteor Shower Sky Map


Excerpt from
space.com

 The spectacular Geminid Meteor shower hits peak activity this weekend. Though competing with some unfortunate moonlight, the shower still should make for a must-see astronomical event.

While moonlight will somewhat hinder this year's Geminid meteor shower, intrepid observers with good weather and low light pollution should still be able to catch a good meteor show Saturday (Dec. 13) night.

"If you have not seen a mighty Geminid fireball arcing gracefully across an expanse of sky, then you have not seen a meteor," note astronomers David Levy and Stephen Edberg. 


Even if you can't see the meteor display from your part of the world, you can watch them online. The online Slooh Community Observatory will host a live webacst of the Geminid meteor display on Saturday night beginning at 8 p.m. EST (0100 Dec. 14 GMT).You can also watch the Slooh webcast directly:http://live.slooh.com/. NASA meteor expert Bill Cooke will also host a live Geminids webchat on Saturday night from 11 p.m. to 3 a.m. EST (0400 to 0800 GMT), as well as a live webcast.
You can watch the webcasts of the Geminid shower live on Space.com, starting at 8 p.m. EST, courtesy of Slooh and NASA. The Italy-based Virtual Telescope Project will also host a Geminds webcast, beginning at 9 p.m. EST (0200 GMT).

Although the bright moon will be high in the sky by 11:30 p.m. local time Saturday (Dec. 13) (during the shower's peak), skywatchers can still catch a potentially incredible show before the moon creeps above the horizon, washing out the sky. Stargazers might be able to see an average of one or two Geminid meteors per minute Saturday before the moon rises.

By around 9 p.m., the constellation Gemini — the part of the sky where the meteors seem to emanate from — will have climbed more than one-third of the way up from the horizon. Meteor sightings should begin to really increase noticeably thereafter. By around 2 a.m., the last-quarter moon will be low in the east-southeast, but Gemini will stand high overhead. So you might still see a good number of meteors in spite of the moon's presence.

A brilliant shower

The Geminids are, for those willing to brave the chill of a December night, a very fine winter shower, and usually the most satisfying of all the annual showers. They can even surpass the brilliant August Perseid meteor shower.

Studies of past displays show that the Geminid shower is rich both in slow, bright, graceful meteors and fireballs, as well as in faint meteors, with relatively fewer objects of medium brightness. Many Geminids appear yellowish in hue; some even appear to form jagged or divided paths.     

These meteors travel at a medium speed and appear to emanate, specifically, from near the bright star Castor, in the constellation of Gemini, the Twins, hence the name "Geminid." In apparent size, that's less than half the width of the moon. As such, this is a rather sharply defined radiant as most meteor showers go. It suggests the stream is "young," perhaps only several thousand years old.

Generally speaking, depending on your location, Castor begins to come up above the east-northeast horizon right around the time evening twilight comes to an end. As the Gemini constellation begins to climb the eastern sky just after darkness falls, there is a fair chance of perhaps catching sight of some "Earth-grazing" meteors. Earthgrazers are long, bright shooting stars that streak overhead from a point near to even just below the horizon. Such meteors are so distinctive because they follow long paths nearly parallel to the Earth's atmosphere. 

Because Geminid meteoroids are several times denser than the comet dust that supply most meteor showers and because of the relatively slow speed with which the Geminids encounter Earth (22 miles or 35 kilometers per second), these meteors appear to linger a bit longer in view than most. As compared to an Orionid or Leonid meteor that can whiz across your line of sight in less than a second, a Geminid meteor moves only about half as fast. Personally, their movement reminds me of field mice scooting from one part of the sky to another.

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