More about Comet SWAN Crashing into the SUN

Mar 16, 2012; 4:05 AM ET

This blog is written by AccuWeather Facebook page’s astronomy expert Daniel Vogler.

The other day, we witnessed something spectacular in my opinion, although the event is considered by most mainstream scientists a “coincidence.” I happen to believe there are no coincidences, we just have yet to figure out the reasoning behind them.

The event I am referring to is the Comet SWAN making it to its final destination that is the Sun and what happened after that. To see the comet again, click here.

A Coronal Mass Ejection was present nearly an hour or two later after the comet disappeared into the corona.

For a comet to have an effect on the Sun, it would require immense magnetic field strength. The comet itself does not have its own magnetic field, but it CAN get one as it gets closer to the sun. An induced magnetic field works like this: A comet’s most abundant ice species is the H2O water ice. As the comet gets closer to the sun, the ice sublimates, producing gas that trails behind it along with dust. It’s this setup that allows the mass ionization around the tail known as the ion tail. When you have ions, you then can have a magnetic field generating from the incoming solar wind from the sun. Once the particles have been ionized, they attain a net positive electrical charge. As the comet, now with its induced magnetic field, travels, a bow shock is formed. In this bow shock, large concentrations of cometary ions (called “pick-up ions”) congregate and act to “load” the solar magnetic field with plasma, such that the field lines “drape” around the comet forming the ion tail. (Carroll, B. W.; Ostlie, D. A. (1996). An Introduction to Modern Astrophysics. Addison-Wesley. pp. 864-874)

The addition of heavy cometary ions to the solar wind flow alters the dynamics due to the mass addition itself and also because the pick-up ions have a large pressure. The net effect is to slow down the solar wind. This slow-down process takes place continuously until a critical mass flux is reached, at which point a shock forms. (Galeev, A. A., Plasma processes in the outer coma, in Comets in the Post-Halley Era, vol. 2, eds. R. L.Newburn, Jr. et al., p. 1145, Kluwer Acad., Norwell, MA, 1991.)

Why am I being so technical with the vocabulary? If you haven’t figured out yet, the Sun’s own magnetic field is the main reason behind CMEs. And what would happen if something like a comet with an induced magnetic field that gets stronger, collecting plasma, as it gets closer to the Sun? My idea goes along the lines of the strength of the bow shock once it gets at the sun’s chromosphere, it generates enough magnetic force to shove each other and one will have to give, and since the sun is a gas star (albeit way bigger than the comet), the reaction comes from the other side (CME). Imagine trying to push two really big, like-sided magnets together.

I really hope this makes better sense as to how a comet gets a magnetic field and how this induced field is actually the culprit of the CME. Keep in mind, this is just a theory running around in my head with a few works cited on how the magnetic field is made. I have yet to see a real peer-reviewed study of this “coincidence.” If you have something to add to the theory that I may have not thought of, please like and comment on AccuWeather Astronomy on facebook for discussion.

via AccuWeather.com – Astronomy | More about Comet SWAN Crashing into the SUN.

Advertisements

How to see Comet Garradd in November 2011

By Bruce McClure

Comet Garradd and the Coathanger in early September 2011


If you have binoculars, start searching for Comet Garradd in November 2011. This post tells you how to find the comet in front of the constellation Hercules.

Feel like chasing a comet? Grab your binoculars and head for a clear dark sky to see Comet C/2009 P1 Garradd. It’s the sky’s most conspicuous comet now, approaching sixth-magnitude in brightness. It’s visible through binoculars, even though the comet is quite faint. The last time I looked, Comet Garradd looked like a ghost of a fuzzball in my 10×50 binoculars, with no hint of a tail. All the same, it’s a great thrill to catch this creature of the wild roaming in the wilderness of the solar system.

This comet is predicted to remain at about the same brightness until March 2012. The magnitude isn’t expected to change greatly over the next several months, though Comet Garradd will probably peak in brightness in February 2012.

And there’s more good news. Until now, Comet Garradd has been traveling relatively rapidly across our sky, passing many constellations along the way, making it a hard target to track for casual viewers. Now, though, the comet has settled into a region of the sky near a noticeable star pattern, or asterism – the famous Keystone asterism of the constellation Hercules. Comet Garradd will be in front of Hercules from now until February 2012. So finding Hercules – and its Keystone star pattern – is your ticket to seeing Comet Garradd.

Ready? Let’s chase a comet!

How to find the Keystone in Hercules

At mid-northern latitudes throughout November, the constellation Hercules and its Keystone asterism appear in the western sky at nightfall. Hercules falls downward throughout the evening hours and sinks behind the northwestern horizon by around mid-evening. So find an unobstructed western horizon, and do your comet-hunting at nightfall and early evening.

Vega is your guide star to the constellation Hercules.

To locate Hercules and the Keystone, you need to know two reference stars. One is noticeable for being part of a large triangular pattern in the sky – The Summer Triangle – which is much bigger than the Keystone! The other star is noticeable because … well, it’s just in a noticeable spot now, low in the west at nightfall. The two guide stars shine on opposite sides of the Keystone, so look for the Keystone between these stars. They are Vega and Gemma (otherwise known as Alphecca).

The bright star Vega pops out quite high in the western sky at dusk and nightfall. Many are familiar with Vega because it’s the brightest star of the Summer Triangle asterism. The first-magnitude star Vega serves as your premier signpost to Comet Garradd.

Vega is your guide star to the constellation Hercules.

The second-magnitude star Gemma (Alphecca), the brightest in the C-shaped constellation Corona Borealis, lurks low in the west to northwest sky at nightfall and early evening. If it’s dark enough, you’ll easily recognize Gemma (Alphecca) as the brightest star in the graceful semi-circle of stars known as Corona Borealis.

The Keystone of Hercules is found by using the two guide stars, Vega and Gemma (Alphecca). On a dark night, the Keystone sticks out like a sore thumb roughly midway between Vega and Gemma. It’s a squarish pattern, with four modestly bright stars marking the corners of the square. Remember, the Keystone is famous! You can see it, if you let your eyes look for patterns among the stars. As evening deepens into late night, Gemma sets first at early evening, the Keystone sets an hour or two thereafter, and Vega sets last around midnight.

Look left of the Keystone asterism in the constellation Hercules for the guide stars Rasalhague and Rasalgethi and Comet Garradd.

Once you know the Keystone, try to branch out from there to fill out the stick figure of Hercules. A good familiarity with Hercules will enable you to star-hop to Comet Garradd.

Rasalhague, second-magnitude reference star

As shown on the above sky chart, look about 20 degrees to the left of the Keystone to find the second-magnitude star Rasalhague. Your fist at arm’s length spans about 10 degrees of sky, so look for this star about two fist-widths to the left of the Keystone. It’s the brightest star in this realm of sky, not far from the somewhat fainter star Rasalgethi in Hercules.

Omicron Herculis, the fourth-magnitude star to the upper left of the Keystone and the lower left of Vega, is rather faint but easily visible to the unaided eye on a dark night. You can find Omicron Herculis pretty much in line with Vega and Rasalhague. If you can see this star with the naked eye, that’s a good sign, as it’s more likely that you’ll also catch Comet Garradd with binoculars.

Throughout November 2011, Comet Garradd is found between the star Omicron Herculis on one side and Rasalhague and Rasalgethi on the other. Search for this comet about one-third of the way from Rasalhague (or Rasalgethi) to Omicron Herculis. Click on the image to the lower right for a more detailed sky chart showing the path of Comet Garradd in front of Hercules.

Star-hopping with binoculars to find the comet

Before looking for any comet, it’s best to practice star-hopping to deep-sky objects with binoculars. Since you’ll probably be using the Keystone to star-hop to Comet Garradd, how about star-hopping to the Hercules globular star cluster (Messier 13) right off the bat? Through binoculars, the Hercules cluster looks like a dim and possibly fuzzy star. With a good telescope, you can begin to appreciate the Hercules cluster for what it really is – a globe-shaped stellar city teeming with hundreds of thousands of stars.


To see an enlarged PDF version of this chart, click here.

The Hercules cluster (Messier 13) is only somewhat brighter than sixth magnitude, which means it’s just barely bright enough to perceive with the unaided eye. You need a clear, dark night and eagle-eyed vision to see this sixth-magnitude object as a faint speck of light. More than likely, you’ll need binoculars to spot the Hercules cluster.

It’ll be good practice to observe this cluster with binoculars time and time again before searching for a comet that may or may not reach sixth magnitude in brightness. Once you’ve become accustomed to finding the Hercules cluster (Messier 13), try finding Hercules’ fainter globular star cluster, Messier 92. At 6.5 magnitude (the higher the magnitude, the dimmer the object) Messier 92 is somewhere around 1.5 to 2 times dimmer than Messier 13.

Comet Garradd will pair up with Messier 92 on February 3, 2012. So think photo opportunity! If you’re able to locate Messier 92, you can then use this star cluster to find Comet Garradd.

Sky chart of the constellation Hercules, including M13 and M92

Use the bright star Vega to find the Keystone of Hercules, and then use the Keystone to locate M13, the great Hercules cluster.


Sky chart: Wikimedia Commons

Tracking down and spotting Comet Garradd with binoculars won’t come easily. I first saw it as a small, faint fuzzball in my 10×50 binoculars on the evening of October 23.

You’ll need a good familiarity with the constellation Hercules and a detailed sky chart to find this comet. (Click here for another sky chart.) Plus, you’ll need a dark, moonless night and perhaps 10 to 20 minutes in the dark to give your eyes time to adapt. EarthSky reader Willow Lepanto sums it up most eloquently: “love chasing something untouchable … and uncatchable.”

But if you’re up for the challenge, Comet Garradd may be yours to behold on dark, moonless nights in the autumn of 2011 and winter of 2012!

via How to see Comet Garradd in November 2011 | Astronomy Essentials | EarthSky.

Debris of ‘Doomsday’ Comet Elenin to Pass by Earth Sunday

By Mike Wall, SPACE.com Senior Writer

Fri, Oct 14, 2011

The moment long feared by conspiracy theorists is nearly upon us: The "doomsday comet" Elenin will make its closest approach to Earth Sunday (Oct. 16). Or what’s left of it will, anyway.

Comet Elenin started breaking up in August after being blasted by a huge solar storm, and a close pass by the sun on Sept. 10 apparently finished it off, astronomers say. So what will cruise within 22 million miles (35.4 million kilometers) of our planet Sunday is likely to be a stream of debris rather than a completely intact comet.

And the leftovers of Elenin won’t return for 12,000 years, astronomers say.

"Folks are having trouble finding it, so I think it’s probably dead and gone," said astronomer Don Yeomans of the Near-Earth Object Program Office at NASA’s Jet Propulsion Laboratory in Pasadena, Calif.

That means it probably won’t present much of a skywatching show Sunday, scientists have said.

The doomsday comet

Elenin’s apparent demise may come as a relief to some folks, since apocalyptic rumors circulating on the Internet portrayed the comet as a major threat to Earth.

One theory claimed Elenin would set off havoc on Earth after aligning with other heavenly bodies, spurring massive earthquakes and tsunamis. Another held that Elenin was not a comet at all, but in fact a rogue planet called Nibiru that would bring about the end times on Earth. After all, the comet’s name could be taken as a spooky acronym: “Extinction-Level Event: Nibiru Is Nigh.”

Those ideas were pure nonsense, Yeomans said.

“Elenin was a second-rate, wimpy little comet that never should have been noted for anything, really,” he told SPACE.com. “It was not even a bright one.”

Elenin’s remains will not be the only objects about to make their closest pass of Earth. One day after the Elenin flyby, the small asteroid 2009 TM8 will zip close by. Like Elenin, it poses no risk of striking our home planet.

Asteroid 2009 TM8 is about 21 feet (6.4 meters) wide and the size of a schoolbus. It will come within 212,000 miles of Earth – just inside the orbit of the moon – when it zips by on Monday morning (Oct. 17).

Say goodbye to Elenin

Elenin was named after its discoverer, Russian amateur astronomer Leonid Elenin, who spotted it in December 2010. Before the icy wanderer broke up, its nucleus was likely 2 to 3 miles (3 to 5 km) in diameter, scientists say.

Elenin never posed any threat to life on Earth, Yeomans said. It was far too small to exert any appreciable influence on our planet unless it managed to hit us.

“Just driving to work every day in my subcompact car is going to have far more of a gravitational effect on Earth than this comet ever will,” Yeomans said.

Elenin’s supposed connection to earthquakes was just a correlation, and a weak one at that, he added. Relatively strong earthquakes occur every day somewhere on Earth, so it’s easy — but not statistically valid — to blame some of them on the comet’s changing position.

Yeomans views the frenzy over Elenin as a product of the Internet age, which allows loud and often uninformed voices to drown out the rather more prosaic results that scientists publish in peer-reviewed journals.

“It’s a snowball effect on the Web,” Yeomans said. “You get one or two folks who make an outrageous claim, and a bunch of others pile on. Some folks are actually making a living this way.”

Elenin’s crumbs will soon leave Earth in the rear-view mirror, speeding out on a long journey to the outer solar system. But Yeomans doesn’t think the departure will keep the conspiracy theorists down for long.

“It’s time to move on to the next armageddon,” he said.

You can follow SPACE.com senior writer Mike Wall on Twitter: @michaeldwall. Follow SPACE.com for the latest in space science and exploration news on Twitter @Spacedotcom and on Facebook.

via Debris of ‘Doomsday’ Comet Elenin to Pass by Earth Sunday – Yahoo! News.