Comet ISON
The 'comet of the century' that never was: it fell apart while skimming the Sun in November 2013.
Key facts
- Designation
- C/2012 S1 (ISON)
- Type
- Sungrazing comet from the Oort cloud (destroyed)
- Orbital period
- none: it was on its first visit and did not survive
- Closest to the Sun
- about 1.2 million km from the Sun's centre, under 1 million km above the surface
- Farthest from the Sun
- none: it came from the Oort cloud on its first trip in
- Tilt of orbit
- about 62°
- Nucleus
- probably about 1 km before it broke up
- Discovered
- by Vitali Nevski and Artyom Novichonok on 21 September 2012
- Returns
- destroyed at perihelion on 28 November 2013
Orbit
ISON was a sungrazer on its first journey in from the Oort cloud. Its path took it within about 1 million km of the Sun's surface. It is not a Kreutz comet: its orbit was quite different.
Size and nature
Its nucleus was probably about 1 km across, small for such a close pass. Comets arriving for the first time often look bright far out, as their most easily evaporated ices burn off, and then fail to brighten as fast as predicted. ISON did exactly that. Near perihelion it flared and then faded rapidly. SOHO images showed a fuzzy remnant emerging from behind the Sun, which soon dispersed into dust.
History
Vitali Nevski and Artyom Novichonok found it with a telescope of the International Scientific Optical Network, which gave the comet its name. Because it was found more than a year before it reached the Sun, and on a sungrazing path, some forecasts predicted it might rival the full Moon in brightness. A worldwide campaign of observations followed, including from spacecraft at Mars.
Why it matters
ISON was a lesson in how hard comets are to predict, and in how fragile a small, fresh comet can be. Its death throes were filmed in detail, giving a close look at a comet coming apart.
Space missions
- SOHO A solar observatory that has become the greatest comet discoverer in history.
Key dates
| Date | What happened |
|---|---|
| 21 September 2012 | Vitali Nevski and Artyom Novichonok discovered Comet ISON. |
| 28 November 2013 | Comet ISON broke apart as it skimmed the Sun. |
Did you know?
ISON was the most observed comet in history up to that time.
Its demise happened on American Thanksgiving Day.
Comets on their first visit are often called dynamically new.