Path of Comet ISON (C/2012 S1)

Comet ISON

Tracking Comet ISON through the Constellations

Comet ISON's orbit, as calculated by JPL/NASA, appears alongside the orbtial path of Comet ISON through the constellations from the perspective of someone living in Sydney, Australia. Click on icon in lower right corner to enter full screen mode.

Credit: Adapted from NASA/JPL and Stellarium

The old adage "a picture is worth a thousand words" definitely applies to the path of Comet ISON (C/2012 S1). Even better than a picture, the movie to the left shows the path of Comet ISON through the constellations days after day.

 

If you simply love the written word or have an irrational fear of watching Flash movies, what follows is an attempt to verbally explain the orbit of Comet ISON (C/2012 S1) as seen from Earth's perspective.

 

Comet ISON spends most of it life in the Oort Cloud. From Earth's perspective this means ISON lies unseen between the constellations of Gemini and Lynx.

 

As Comet ISON's enters the inner solar system, it begins to move through the constellations. It will eventually become visible to the naked eye between Virgo and Leo around November 4, 2013. Mars will also be in the area, rising along with ISON in the east before sunrise.

 

On November 28, 2013 Comet ISON was within 800,000 miles (1.2 million km) of the Sun's surface. This was the closest the comet came to the Sun. This position is known as its perihelion. From Earth's perspective, a tight grouping of Saturn and Mercury was be in the vicinity (see movie).

 

Comet ISON passed within the Roche Limit, which meant that the Sun's gravity and/ortemperature could cause Comet ISON to disintegrate. If ISON could survive, it would shed an enormous amount of material and become the most spectacular of all comets in 2013. Some astronomers believed it even had a chance to become the "Comet of the Century"—rivaling Ikeya-Seki, which was the brightest comet in the 20th century. All Comet ISON (C/2012 S1) had to do was survive perihelion on November 28, 2013. Unfortunately it did not. The vast majority of the comet's nucleus evaporated in the Sun's corona.

 

If it did survive, Comet ISON would have reemerged on the eastern horizon before sunrise. It would have traveled south of Hercules on December 21 and through Draco on December 29 before stalling for several days near Camelopardalis where it would fade from naked-eye visibility.

 

 

Comet ISON's orbital path

 

Comet ISON's path through the constellations

Credit: NASA

 

Comet trajectories, including that of Comet ISON, are unlike anything else in the sky as you can easily see in the movie and grapic above.

 

When viewed from outside the solar system, the movement of a Comet ISON and most other comets is ellipitical and easily understandable (as you can see in the image below). It is the movement of Earth around the Sun that causes a comet, and planets, to appear to move erratically through the constellations compared to stars in the night star which spin around the pole stars.

 

 

The Orbit of Comet Ison - JPL

 

(on left) Orbit of Comet ISON (C/2012 S1) from POV above solar system

(on right) Orbit of Comet ISON (C/2012 S1) from POV outside the solar system, along the ecliptic

Credit: Osamu Ajiki (AstroArts) modified by Ron Baalke (JPL)

 

 

On January 17, 2014, Earth will cross through Comet ISON's inbound path, "Maybe, just maybe, there will be a nice little meteor shower somewhere in the middle of January 2014, from the particles left behind when ISON flew through before," said Tony Darnel - the creator of Deep Astronomy.

 

 

 

 

 

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