Comet tail

tailcomet's tailtailscometary tailtail of a cometcomet gas tailscometary plasmasion gas tail and to the lower right is the dust tail.sodium tail
A comet tail—and coma—are features visible in comets when they are illuminated by the Sun and may become visible from Earth when a comet passes through the inner Solar System.wikipedia
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Comet

cometslong-period cometJupiter-family comet
A comet tail—and coma—are features visible in comets when they are illuminated by the Sun and may become visible from Earth when a comet passes through the inner Solar System.
This produces a visible atmosphere or coma, and sometimes also a tail.

Coma (cometary)

comacomaecometary activity
A comet tail—and coma—are features visible in comets when they are illuminated by the Sun and may become visible from Earth when a comet passes through the inner Solar System. The streams of dust and gas thus released form a huge, extremely tenuous atmosphere around the comet called the coma, and the force exerted on the coma by the Sun's radiation pressure and solar wind cause an enormous tail to form, which points away from the Sun.
Larger dust particles are left along the comet's orbital path while smaller particles are pushed away from the Sun into the comet's tail by light pressure.

Antitail

dust trail
The tail of dust is left behind in the comet's orbit in such a manner that it often forms a curved tail called the antitail, only when it seems that it is directed towards the Sun.
An antitail is a spike projecting from a comet's coma which seems to go towards the Sun, and thus geometrically opposite to the other tails: the ion tail and the dust tail.

Radiation pressure

solar radiation pressurelight pressurepressure of light
The streams of dust and gas thus released form a huge, extremely tenuous atmosphere around the comet called the coma, and the force exerted on the coma by the Sun's radiation pressure and solar wind cause an enormous tail to form, which points away from the Sun.
Solar radiation pressure strongly affects comet tails.

C/2009 R1

A disconnection event was also seen with C/2009 R1 (McNaught) on May 26, 2010.
The comet is notable for its "impressive green coma and long ion tail", which spanned 5 degrees as of June 6, 2010, and its appearance has been likened to an "apple on a stick."

Earth

Earth's surfaceterrestrialworld
A comet tail—and coma—are features visible in comets when they are illuminated by the Sun and may become visible from Earth when a comet passes through the inner Solar System.

Solar System

outer Solar Systeminner Solar Systemouter planets
A comet tail—and coma—are features visible in comets when they are illuminated by the Sun and may become visible from Earth when a comet passes through the inner Solar System.

Solar irradiance

solar radiationinsolationsolar insolation
As a comet approaches the inner Solar System, solar radiation causes the volatile materials within the comet to vaporize and stream out of the nucleus, carrying dust away with them.

Ion

cationanionions
Separate tails are formed of dust and gases, becoming visible through different phenomena; the dust reflects sunlight directly and the gases glow from ionisation.

Telescope

telescopestelescopicspyglass
Most comets are too faint to be visible without the aid of a telescope, but a few each decade become bright enough to be visible to the naked eye.

Naked eye

naked-eyeunaided eyenaked human eye
Most comets are too faint to be visible without the aid of a telescope, but a few each decade become bright enough to be visible to the naked eye.

Kuiper belt

Kuiper belt objectKuiper belt objectsKuiper cliff
Statistical detections of inactive comet nuclei in the Kuiper belt have been reported from the Hubble Space Telescope observations, but these detections have been questioned, and have not yet been independently confirmed.

Hubble Space Telescope

HubbleHSTHubble Telescope
Statistical detections of inactive comet nuclei in the Kuiper belt have been reported from the Hubble Space Telescope observations, but these detections have been questioned, and have not yet been independently confirmed.

Cosmic dust

interstellar dustdustspace dust
The streams of dust and gas thus released form a huge, extremely tenuous atmosphere around the comet called the coma, and the force exerted on the coma by the Sun's radiation pressure and solar wind cause an enormous tail to form, which points away from the Sun.

Solar wind

solar windslosessolar
The streams of dust and gas thus released form a huge, extremely tenuous atmosphere around the comet called the coma, and the force exerted on the coma by the Sun's radiation pressure and solar wind cause an enormous tail to form, which points away from the Sun.

Parallax

trigonometric parallaxsolar parallaxmotion parallax
Parallax viewing from the Earth may sometimes mean the tails appear to point in opposite directions.

Ulysses (spacecraft)

UlyssesUlysses'' spacecraftUlysses probe
The Ulysses spacecraft made an unexpected pass through the tail of the comet C/2006 P1 (Comet McNaught), on February 3, 2007.

C/2006 P1 (McNaught)

C/2006 P1Comet McNaughtC2006P1
The Ulysses spacecraft made an unexpected pass through the tail of the comet C/2006 P1 (Comet McNaught), on February 3, 2007.

The Astrophysical Journal

Astrophysical JournalAstrophysical Journal LettersThe Astrophysical Journal Letters
Evidence of the encounter was published in the October 1, 2007, issue of The Astrophysical Journal.

Ultraviolet

UVultraviolet lightultraviolet radiation
The ion tail is the result of ultraviolet radiation ejecting electrons off particles in the coma.

Magnetosphere

magnetotailmagnetosphericEarth's magnetosphere
Once the particles have been ionised, they form a plasma which in turn induces a magnetosphere around the comet.

Bow shock

shockbow shocksbow shock hyperbola
The comet is supersonic relative to the solar wind, so a bow shock is formed upstream of the comet (i.e. facing the Sun), in the flow direction of the solar wind.

Plasma (physics)

plasmaplasma physicsplasmas
In this bow shock, large concentrations of cometary ions (called "pick-up ions") congregate and act to "load" the solar magnetic field with plasma.

Magnetic reconnection

reconnectionintense magnetic fieldmagnetic field line reconnection
If the ion tail loading is sufficient, then the magnetic field lines are squeezed together to the point where, at some distance along the ion tail, magnetic reconnection occurs.

Comet Encke

Encke's Comet2P/EnckeEncke
April 2007 when the ion tail of comet Encke was completely severed as the comet passed through a coronal mass ejection.