Comet ISON Nears Sun for Thanksgiving Encounter in NASA Video

[Buster's Uncle]

Comet ISON Nears Sun for Thanksgiving Encounter in NASA Video
SPACE.com
By Tariq Malik, Managing Editor  5 hours ago



This still from a NASA video by the STEREO-A spacecraft shows Comet ISON, Mercury, Comet Encke and Earth



A NASA spacecraft has captured its best video yet of the icy Comet ISON streaking toward a Thanksgiving Day encounter with a sun, a close shave that the comet might just not survive.

The latest video of Comet ISON comes from NASA's STEREO-A spacecraft, one of several sun-watching space observatories tracking the comet's close encounter with the sun on Thursday (Nov. 28).

"This movie from the spacecraft's Heliospheric Imager shows Comet ISON, Mercury, Comet Encke and Earth over a five-day period from Nov. 20 to Nov. 25, 2013," NASA officials wrote in a video description. "The sun sits right of the field of view of this camera."

Known officially as C/2012 S1 (ISON), Comet ISON is what scientists call a "sungrazer" comet because its orbit brings it extremely close to the sun. It is that extremely close solar shave, less than one diameter of the sun away, that has scientists guessing as to whether ISON will survive the encounter.

In the video, Comet ISON appears as a bright object streaking from left to right as it draws ever closer to the sun. Comet Encke, meanwhile, appears as a dimmer object moving from the upper left to lower right. The planets Mercury and Earth and labeled in the STEREO-A view.

NASA scientists, amateur astronomers and a fleet of spacecraft are tracking Comet ISON's solar passage on Thursday. The comet has drawn wide interest because of its potential to be a spectacular sight in the night sky, with some scientists dubbing the object a possible "comet of the century."

Comet ISON's origins in the distant Oort cloud, a realm of icy objects surrounding the entire solar system, has scientists excited because ISON is a pristine sample of the raw ingredients that formed Earth and other planets in the solar system.

Comet ISON was discovered in September 2012 by Russian amateur astronomers Vitali Nevski and Artyom Novichonok. Since then, it has been meticulously followed by professional and amateur astronomers using ground-based telescopes, as well as space-based observatories. The Hubble Space Telescope and NASA spacecraft orbiting Mars and Mercury have also captured images of the incoming comet.

On Thursday, NASA will hold a Google Hangout from 1 p.m. to 3:30 p.m. EST (1800 to 2030 GMT) to stream live views of the comet during its close sun approach. You will be able to watch the Comet ISON hangout live on SPACE.com here.


http://news.yahoo.com/comet-ison-nears-sun-thanksgiving-encounter-nasa-video-115928783.html

[Buster's Uncle]

Will comet ISON survive its near brush with the Sun?
AFP 
7 hours ago



This NASA Hubble Space Telescope image, captured on April 10, 2013 shows Comet C/2012 S1 (ISON) at a distance of 386 million miles from the Sun



Washington (AFP) - US astrophysicists are split over what will happen when the comet ISON passes near the sun Thursday, but a majority think it will break apart.

Comets are frozen balls of space dust left over from the formation of stars and planets billions of years ago.

So when one of them zips close to a hot star, like the Sun, sometimes the icy core simply melts.

"Many of us think it could break up into pieces, and some people think it won't survive at all" after its brush near the Sun, said comet expert Carey Lisse of the Johns Hopkins Applied Physics Laboratory during a telephone press conference.

But he conceded, there are others who think the icy mass "will actually survive and come back out" on the other side of the sun, albeit somewhat shrunken down from its encounter with the Sun's heat.

ISON will be just 1.17 million kilometers (727,000 miles) from the sun as it passes by where it will be hit by temperatures of around 2,700 degrees Celsius (4,900 Fahrenheit).



Map showing Comet ISON's swing past the sun and its position compared to Earth in late December (AFP Photo/-)


"I think it has a maybe 30 percent chance to make it" past the sun intact, Lisse said.

The comet "is like a loose snow ball," he explained, saying it is "maybe half or a third water and it's rather weak." It's also smaller than most comets, currently measuring around 1.2 kilometers in diameter.

"The average size for a comet is about three kilometers diameter, so this comet is maybe about half the size of the average, typical comet," he said.

Either way it turns out, astronomers are watching keenly.

"We have never seen a comet like this coming from the Oort cloud and going in the sun grazing orbit," said astrophysicist Karl Battams, of the Naval Research Laboratory in Washington.

We "don't really have any past experience we can use to judge or predict what is going to happen to this one," he said, adding it's "a very peculiar object but also a fascinating object."

Scientists say the comet comes from the very origin of the solar system, 4.5 billion years ago -- preserved "in deep freeze in the Oort cloud halfway to the next star for the last four and a half billion years," Lisse said.

If ISON survives its passage near the Sun, it will be visible at night from December through February, crossing nearest Earth -- about 64 million kilometers away) on December 26.

The US space agency is gathering a round table of astronomers on Thursday starting at 1700 GMT to answer questions from the public and from the scientific community as they follow the comet's brush with the Sun.


http://news.yahoo.com/comet-ison-survive-near-brush-sun-052728495.html

[Buster's Uncle]

Comet may be visible from Earth if it survives sun's heat, gravity
Reuters
By Irene Klotz 21 minutes ago



(Reuters) - A comet that left the outer edge of the solar system more than 5.5 million years ago will pass close by the sun on Thursday, becoming visible in Earth's skies in the next week or two - if it survives.

"There are three possibilities when this comet rounds the sun," Donald Yeomans, manager of NASA's Near-Earth Object Program Office at the Jet Propulsion Laboratory in Pasadena, Calif., said in an interview posted on NASA's website.

"It could be tough enough to survive the passage of the sun and be a fairly bright, naked-eye object," he said.

The second possibility is that the sun's gravity could rip the comet apart, creating several big chunks.

"As long as there are pieces there, we'll see something," Carey Lisse, senior research scientist at Johns Hopkins Applied Physics Laboratory in Laurel, Md., told reporters on a conference call on Tuesday.

The third option: If the comet is very weak, it could break up into a cloud of dust and be a complete bust for viewing.

"This comet is giving us quite a ride. It's going to be hard to predict exactly what's going on," Lisse said. "As a betting man, I think it's not going to survive solar passage," he added.

Comet ISON, as the object is known, was due to pass just 730,000 miles (1.2 million km) from the surface of the sun at 1:37 p.m. EST/1837 GMT on Thursday.

At that distance, the comet will reach temperatures approaching 5,000 degrees Fahrenheit (2,760 degrees Celsius) - hot enough to vaporize not just ices in the comet's body, but dust and rock as well.

"While it may seem incredible that anything can survive this inferno, the rate at which ISON will likely lose mass is relatively small compared to the actual size of the comet's nucleus," Lowell Observatory astronomer Matthew Knight said in a NASA interview.

Scientists estimate that ISON needs to be about 219 yards to survive its close encounter with the sun. The most recent measurements indicate the comet is more than twice that size, and perhaps as big as .75 miles.

It helps that ISON will not be staying in the solar furnace for long. When it zips around the sun, it will be moving at about 217 miles per second (349 km per second.)


ISON APPEARS

The comet was discovered last year by two amateur astronomers using Russia's International Scientific Optical Network, or ISON.

It was extraordinarily bright at the time, considering its great distance beyond Jupiter's orbit, raising the prospect of a truly cosmic spectacle as it approached the sun.

Heat from the sun causes ices in a comet's body to vaporize, creating bright distinctive tails and fuzzy looking, glowing bodies. The closer comets come to the sun, the brighter they shine, depending on how much ice they contain.

Comets are believed to be frozen remains left over from the formation of the solar system some 4.5 billion years ago.

The family of comets that ISON is from resides in the Oort Cloud, which is located about 10,000 times farther away from the sun than Earth, halfway to the next star.

Occasionally, an Oort Cloud comet is gravitationally nudged out of the cloud by a passing star and into a flight path that millions of years later brings it into the inner solar system. Computer models show ISON is a first-time visitor.

"You need comets in order to build the planets and this comet has been in deep freeze in the Oort Cloud for the last 4.5 billion years," Lisse said.

"Comet ISON is a relic. It's a dinosaur bone of solar system formation," he said.

Oort Cloud comets have passed by Earth before, and sun-grazing comets are common. Comet ISON, however, is unique.

"We have never seen a comet like this, a comet that is both dynamically new from the Oort Cloud and in a sun-grazing orbit," said astrophysicist Karl Battams, with the Naval Research Laboratory in Washington.

"It has been behaving strangely," Battams said, noting recent flares and changes in brightness that could be signs the comet is fragmenting.

Regardless of what happens, "it's already been a huge victory for science," he said.


http://news.yahoo.com/comet-may-visible-earth-survives-suns-heat-gravity-180448240.html

[Buster's Uncle]

Comet ISON's Thursday Sun Encounter a Thanksgiving Feast for NASA
SPACE.com
By Tariq Malik, Managing Editor  1 hour ago



German amateur astronomer Waldemar Skorupa captured this spectacular photo of Comet ISON from Kahler Asten



The icy Comet ISON from the depths of deep space will either meet its doom or transform into a cosmic spectacle when it whips around the sun Thursday (Nov. 28) in a Thanksgiving Day treat for NASA and scientists around the world.

"It's a wonderful holiday roast for all the scientists," NASA scientist Michelle Thaller said in an interview (Nov. 26) of the comet's timely arrival on the U.S. holiday. "While many people will be roasting their turkeys, the sun will be roasting this comet."

The much-anticipated Comet ISON will give the sun the closest of shaves on Thursday (Nov. 28) at 1:38 p.m. EST (1838 GMT) when it comes within 684,000 miles (1.1 million kilometers) of the solar surface, NASA officials said. But despite more than a year of tracking, the big question remains: Will Comet ISON survive its fiery solar encounter, or will it disintegrate in puff of ice and dust?

"This comet has given us quite a ride," Carey Lisse, a senior research scientist at Johns Hopkins Applied Physics Laboratory, told reporters in a NASA teleconference Tuesday. "It's hard to predict what's going on now."

Comet ISON was first discovered in September 2012 by Russian amateur astronomers Vitali Nevski and Artyom Novichonok. Since then, scientists and stargazers on the ground have tracked the comet's progress to see if ISON would live up predictions that it could become a "comet of the century."

Lisse said his personal view is that ISON has a 40 percent chance of surviving its sun flyby.

"I'd be thrilled to be wrong," he added.



The orbit of Comet C/2012 S1 (ISON), better known as Comet ISON, is seen here in this still image


The major draw of Comet ISON is its history. The comet comes from the Oort cloud, a vast cloud of icy objects that surrounds the solar system. ISON is a remnant from the original ingredients that formed the solar system 4.5 billion years ago. The comet is less than a mile wide and made up of 2 billion tons of ice and dust, Thaller said.

According to Lisse, ISON began its trip into the inner solar system long ago, during the "dawn of man," and it won't be seen again for millions of years, if ever.

"What we know of the orbit right now, it should escape into the Oort cloud and never come back," Thaller told SPACE.com. "This is a once-in-a-lifetime chance to see the comet."

On Thursday, NASA scientists will spend the Thanksgiving holiday tracking ISON with the agency's Solar Dynamics Observatory, STEREO probes and the SOHO observatory operated by NASA and the European Space Agency. NASA will also hold a live Google Hangout from 1 p.m. to 3:30 p.m. EST (1800 to 2030 GMT) to showcase views of the comet during its closest approach to the sun. You will be able to watch the Comet ISON hangout live on SPACE.com here.

Initially, Comet ISON did not grow as bright as its predictions had suggested, but in recent weeks the comet flared up dramatically, making it visible to the naked eye about an hour before dawn in the southeastern sky. Just two days ago, the comet experienced another outburst and then settled down, according to images from sun-watching spacecraft like NASA's twin STEREO probes and the SOHO observatory.

On Thanksgiving, Comet ISON will be too close to the sun to be spotted by the naked eye by the casual observer, but it should by crystal clear in views from space-based observatories.

"This is really a critical time, arguably the most critical time, for Comet ISON," said astrophysicist Karl Battams of the U.S. Naval Research Laboratory in Washington, D.C. "It is experiencing the most intense solar radiation and the most intense gravitational forces."

As the ice and dust boils off from Comet ISON near the sun, scientists will be able to learn more about what the comet is made off. The solar passage also offers a chance to study how the atmosphere of the sun behaves, too, Thaller said.

"The neat thing about catching these comets when they're very close to the sun is that we can actually use them as a probe to see what conditions are like close to the sun itself, the magnetic field, the solar wind," she added.

Even if Comet ISON doesn't survive its close encounter with the sun, it could still transform into a remarkable night sky object. In 2012, the Comet Lovejoy was destroyed during a similar solar flyby, but its tail lived on creating dazzling views for skywatchers on Earth, Lisse said.

If ISON's tail or entire body do survive, they would likely be visible from the Northern Hemisphere about 10 days after the sun flyby.

"Starting in early December, we will actually be able to see it fairly close to dawn in the sky. It's actually very close to the sun," Thaller said. "As December goes on, it will get farther way from the sun, and it will be up in the night sky.  By the time you get to mid to late December, if you look up to about the Big Dipper, it should be right there if it survives the sun."


http://news.yahoo.com/comet-isons-thursday-sun-encounter-thanksgiving-feast-nasa-172325156.html

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