Comet LINEAR (1999 S4) was discovered by the Lincoln Near Earth Asteroid Research project on September 27, 1999. At that time, it was bright enough that predictions suggested that it might become a naked eye comet when it was near perihelion.
Shortly thereafter, its orbit was determined well enough to discover that it was a dynamically new comet, which was making its first trip into the inner solar system after being "stored" in the Oort cloud for billions of years. Unfortunately, new comets are notorious for brightening rapidly at large distances (around Jupiter's distance at 5 AU) and then leveling out for awhile before continuing to brighten again around 3 AU. Sure enough, LINEAR followed this pattern, which means it never reached naked eye brightness. It still provided a great show though.
Throughtout June and July 2000, LINEAR was observed to experience frequent outbursts, in which it released more gas and dust than normal, causing it to brighten for a day or two. In early July, an outburst occurred while the Hubble Space telescope was observing the comet. From HST images two days later, a fragment could be seen moving down the tail.
Favorable geometric conditions meant that LINEAR passed its closest point to the Earth (0.36 AU) only three days before it reached perihelion (its closest point to the sun at 0.77 AU) on July 26, 2000. By an amazing coincidence, when LINEAR was closest to Earth, it was also observed to have undergone a complete disruption of its nucleus. The bright central condensation disappeared, and then the coma became elongated and over time simply spread out, dissipated down the tail and faded away.
Because of the fortuitous timing, many astronomers were observing
the comet around the time it disintegrated, and so a lot of
information was obtained about the breakup. These observations, along
with measurements from before the breakup allow us to get a good
picture of what this comet was like.
Go to the LINEAR 1999 S4 Photometry Results Page.
Return to the LINEAR 1999 S4 Home Page.