Home   Sun & Moon   Comets   All about Comet ISON (C/2012 S1)

All about Comet ISON (C/2012 S1)

Update: This event has passed

Comet ISON, known as C/2012 S1 among scientific circles, is the most anticipated comet of the year. At the time of its discovery in 2012, many astronomers and media outlets called it the "comet of the century".

Illustration image

NASA's Hubble Space Telescope captures ISON.

NASA/ESA/STScI/AURA

It was though that the comet would glow as bright as the Moon after its closest approach to the Sun (perihelion) on November 28, which is Thanksgiving Day in the United States.

What are comets?

The initial enthusiasm over the comet has recently waned in recent months since it hasn't become as bright as it was expected to. Despite this, the comet is expected to be visible to the naked eyes to observers in the Northern Hemisphere throughout the month of December.

3 comets to grace the winter skies in 2013

Discovery of comet ISON

Comet ISON, a sun-grazing comet, was discovered on September 21, 2012 by astronomers Vitali Nevski and Artyom Novichonok, using the International Scientific Optical Network (ISON) located in Russia.

Sun-grazing comet

ISON falls in a special category of comets also known as sun-grazing comets. These comets pass very close to the Sun at their perihelion - usually a few thousand kilometers from the Sun's surface.

The close solar approach of such comets means that sometimes smaller comets tend to evaporate when they come close to the Sun, while larger comets may disintegrate when facing strong tidal forces from the Sun. Sometimes though larger, sun-grazing comets can survive their perihelion approach.

Astronomers believe that there is a possibility that ISON may disintegrate when it makes its closest approach to the Sun on November 28. If it does not disintegrate, the comet will be visible to the naked eye in December even though it is not expected to be as bright as it was initially thought to be.

Where and when to view ISON

Observers from the Northern Hemisphere are best located to view ISON in the early mornings before and after it passes its perihelion. Prior to November 28, the comet can be seen using a pair of binoculars.

Astronomers expect the comet to be visible to the naked eye after sunset and before sunrise throughout the month of December.

On December 26, Boxing Day in many parts of the world, the comet will make its closest approach to Earth. At this time, the comet will be in the constellation Draco and will be visible in the northwestern sky after sunset and in the eastern sky before sunrise.

Those in the Southern Hemisphere may be able to view the comet with binoculars low in the east at dawn until November 28. It may be possible to view the comet close to the Sun a few days before and after its perihelion. Please be very careful, it is not recommended to look at the Sun directly!

Topics: Astronomy, Comets, December

In This Article

Advertising

Comets

  1. What Are Comets?
  2. Dec 2018: Comet 46P/Wirtanen
  3. Nov 2013: Comet Encke (2P/Encke)
  4. Nov 2013: Comet ISON (C/2012 S1)
  5. Nov 2013: Comet Lovejoy (C/2013 R1)

More about comets


You might also like

Look Up for Shooting Stars!

Look Up for Shooting Stars!

Shooting stars from the Geminid Meteor Shower can be seen nearly all over the world. The peak is around December 14 with up to 120 meteors an hour! more

Watch Comet 46P/Wirtanen!

Watch Comet 46P/Wirtanen!

All of December, this comet will be bright enough to spot with the naked eye. Find the comet on our Interactive Night Sky Map and see when and where you can watch it. more

Calendar of Cosmic Events

2018-2019 Cosmic Calendar

Astronomical events and highlights of 2018-2019 including supermoons, solar and lunar eclipses, meteor showers, solstices, and equinoxes. more

Screenshot of the Night Sky Map showing Comet Wirtanen's path.

Brightest Comet of 2018

Comet 46P/Wirtanen will grace the night sky in December 2018. Find when, how, and where to see the brightest comet of the year with your naked eyes. more