C/1999 S4 (LINEAR) was a

long-period comet A comet is an icy, small Solar System body that, when passing close to the Sun, warms and begins to release gases, a process that is called outgassing. This produces a visible atmosphere or coma, and sometimes also a tail. These phenomena are ...

discovered on September 27, 1999, by

LINEAR Linearity is the property of a mathematical relationship ('' function'') that can be graphically represented as a straight line. Linearity is closely related to '' proportionality''. Examples in physics include rectilinear motion, the linear ...

. The comet made its closest approach to the Earth on July 22, 2000, at a distance of . It came to

perihelion An apsis (; ) is the farthest or nearest point in the orbit of a planetary body about its primary body. For example, the apsides of the Earth are called the aphelion and perihelion. General description There are two apsides in any elli ...

on July 26, 2000, at a distance of 0.765 AU from the Sun. The

comet nucleus The nucleus is the solid, central part of a comet, once termed a ''dirty snowball'' or an ''icy dirtball''. A cometary nucleus is composed of rock, dust, and frozen gases. When heated by the Sun, the gases sublime and produce an atmosphere ...

was estimated to be about 0.9 km in diameter. Before the comet broke up, the (dust and water) nucleus erosion rate was about 1 cm per day. The comet brightened near July 5, 2000, and underwent a minor fragmentation event. The comet brightened again around July 20, 2000, and then disintegrated. The published optical and most radio data support that the main nuclear decay started July 23, 2000. The dust cloud expanded at about while the fragments expanded at around . Other comets are known to have disappeared, but Comet LINEAR is the first one to have been caught in the act. The orbit of a long-period comet is properly obtained when the

osculating orbit In astronomy, and in particular in astrodynamics, the osculating orbit of an object in space at a given moment in time is the gravitational Kepler orbit (i.e. an elliptic or other conic one) that it would have around its central body if pertu ...

is computed at an

epoch In chronology and periodization, an epoch or reference epoch is an instant in time chosen as the origin of a particular calendar era. The "epoch" serves as a reference point from which time is measured. The moment of epoch is usually decided by ...

after leaving the planetary region and is calculated with respect to the center of mass of the solar system. Using

JPL Horizons JPL Horizons On-Line Ephemeris System provides access to key Solar System data and flexible production of highly accurate ephemerides for Solar System objects. Osculating elements at a given epoch (such as produced by the JPL Small-Body Databas ...

, the barycentric orbital elements for epoch 2010-Jan-01 generate a semi-major axis of 700 AU, an aphelion distance of 1400 AU, and a period of approximately 18,700 years.

References

External links

Orbital simulation
from JPL (Java)
Horizons Ephemeris

– Seiichi Yoshida @ aerith.net

– Gary W. Kronk
Hubble Sees Comet Linear Blow its Top STScI-2000-26
(7 July 2000)
Hubble Discovers Missing Pieces of Comet Linear STScI-2000-27
(5 August 2000)
The VLT Observes Comet LINEAR's "Shower"
(6 August 2000)
Comet LINEAR continues to disintegrate and could disappear completely within a few days
(31 July 2000) {{DEFAULTSORT:C 1999 S4 Hyperbolic comets 19990927 Destroyed comets