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The Comet of the Century: Burning Bright or Burning Out? Interesting Update

Updated on March 14, 2015
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In Cape Canaveral, Florida, astronomers were slated to meet to discuss observing plans for Comet Ison.

There has been much hoopla surrounding Comet Ison. Comet Ison has been slated to have the potential of becoming the Comet of the Century.

Why do they say this? What exactly does this mean?

Many of you may already have heard some of the details. Astronomers are reporting that Comet Ison has the potential of being as bright as the full moon, or even visible in daylight. Comet Ison is a sungrazer comet, which means it will pass very close to the sun.

They estimate Comet Ison's nucleus to be between .6 and 6 miles. Amateur astronomers Vitalyi Nevsky and Artyom Novichonok discovered the comet in photographs taken with the ISON telescope (for which it is named) in September 2012. When it was discovered, it was 625 million miles from Earth in the constellation of Cancer. At the time of discovery, it's magnitude was about 18.8 (lower numbers represent a greater brightness).

It is expected to pass within 800,000 miles of the sun's surface on November 28, 2013. It seems to be following a similar course to the Great Comet of 1680. Right now, it has a tail of over 40,000 miles long.

Source

Structure of a Comet

Structure of a Comet (Click on picture to enlarge)
Structure of a Comet (Click on picture to enlarge) | Source

What Is A Comet?

Comets have often been referred to as "dirty snowballs". They are start out as small, irregularly shaped balls of frozen gas, ice, and rocks, bits of leftover stardust and planets. As the comet nears the sun, solar radiation causes the materials in the comet carrying dust away with them. The stream of gas and dust form a huge atmosphere around the comet called a coma and the force exerted on the coma by the radiation pressure and solar wind cause an enormous tail to form, which always points away from the sun. Comets always follow an elliptical path.

Interestingly enough, the word comet originated from a greek word that meant literally "Stars with hair."

Short-period comets originate in the Kuiper Belt or its associated scattered disc beyond the orbit of Neptune, while long-period comets originate in an area of space outside the orbit of Pluto called the Oort cloud, named after the Dutch Astronomer Jan Oort who first proposed its existence in 1950.

The Oort cloud is an immense spherical cloud surrounding our solar system; its vast distance is considered to be the furthest edge of the Sun's gravitational effect. Millions of Comets usually live peacefully in this Oort cloud, orbiting around the Sun, billions of miles deep into Space. But every now and again one of them may get disturbed in its orbit and begin to fall in towards the Sun.

As it passes the outer planets on its journey towards the Sun it begins to warm up, and as it warms up it starts to evaporate and the internal gases start to escape. In the low pressure conditions of space, water sublimes, that is, it goes directly from solid to gas -- just like dry ice does on Earth. Water probably makes up 75-80% of the volatile material in most comets. Other common ices are carbon monoxide (CO), carbon dioxide (CO2), methane (CH4), ammonia (NH3), and formaldehyde (H2CO).

Comet Swift-Tuttle (1992)
Comet Swift-Tuttle (1992)
Comet Shoemaker-Levy 9 (1994) breaking up before it collides with Jupiter's surface
Comet Shoemaker-Levy 9 (1994) breaking up before it collides with Jupiter's surface
COmet Hyakutake (1996)
COmet Hyakutake (1996) | Source
Comet Hale Bop (1997)
Comet Hale Bop (1997) | Source

What Are Some Famous Comets We Have Seen In The Last Decades?

Halley's Comet is a well known and well observed comet. I, myself, remember well observing it on a school field trip, no less, in 1986. We had just finished listening to a lecture by an astronomy professor and then we went out onto the roof where the observatory was located. They had many telescopes, binoculars, and monitors set up, so that everyone could enjoy the show. And enjoy, we did.

Comet Swift Tuttle made an appearance in 1992. This comet made a stir because of a miscalculation of the orbit being 17 days off. An astronomer theorized that if they were 17 days off again, its return in 2126 would place it right in the path of the Earth. However, a closer view and researching of the older orbits found that it is indeed very predictable, and no poses no danger in the next milleniums.

It is the parent body of the Perseid Meteor shower.

I also remember well observing Hale Bop. This was probably one of the most observed comets of the 20th century. It was visible for an amazing 18 months. This comet passed perihelion on April 1, 1997.

Comet Shoemaker-Levy 9 made headline news when in July of 1994 it collided with Jupiter's surface. The largest of collisions occurred on July 18, 1994, causing a dark spot 9,000 miles wide in diameter. This was the first direct observation of a collision between two space bodies.

Comet Hyakutake first became visible to the naked eye in March of 1996. By the end of March, the comet was the brightest night sky object, taking on a bluish green color because of diatomic carbon emissions. Comet Hyakutake was moving so fast that you could literally see it move against the backdrop of the stars. It moved at a rate of about the diameter of the full moon's width every half hour.

For a list of the brightest comets since 1935, listed by magnitude (brightness), see this article, International Comet Quarterly.

Impact Sites on Jupiter After Comet Shoemaker-Levy 9 Collision

Public domain courtesy of Nasa.gov
Public domain courtesy of Nasa.gov | Source

Shoemaker-Levy 9 Impacts Jupiter

Comet Ison's Path-Stay up to date here at Sky & Telescope
Comet Ison's Path-Stay up to date here at Sky & Telescope | Source

The Problem With Comets

With all this talk of comets, it sounds like we have something spectacular to look forward to in late November 2013, right?

Well, maybe, maybe not. You see, the problem with comets is that they are notoriously unpredictable. Many of them break apart long before they have a chance to putting on a dazzling light show.

What about Comet Ison? Will Comet Ison Dazzle or Fizzle?


The latest news is not so encouraging. While many had hoped that it would be The Comet of the Century, latest findings is that it, too, may be a dud.

"The future of comet ISON does not look bright," astronomer Ignacio Ferrin, with the University of Antioquia in Colombia, was quoted as saying in a statement on Monday, July 29, 2013.

His calculations show the comet has not brightened since mid-January. This may mean that the ice particles making up its body have already melted as the comet moves closer to the sun, which is responsible for creating the long, bright tail.

Another theory is that the comet is covered in a layer of silicate dust that snuffs out water vapor and other gases that brighten the comet.

The bottom line is that Comet Ison has been at a standstill for more than 132 days at a magnitude of 16, which has puzzled some astronomers. This could remain the case until it escapes the glare of the sun on September 16.

If it survives and passes as close as predicted from the sun on November 28, the comet would reach temperatures of about 4,900 degrees Fahrenheit (2,700 degrees Celsius), which is hot enough to melt lead. It may also be pulled apart by the sun's gravity.

To find out what Comet Ison will really look like, we will just have to wait and see.

Will you be there? I know I will!


References:


Spectacular Must See Video of Comet Seen From Space

Aurora (Northern Lights) As Seen From Space

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