June 20, 2005
DEEP IMPACT - 3rd of July Comet Crash
NASA has scheduled a special fireworks event for the 3rd of July. A projectile launched from the spacecraft called "Deep Impact" will strike the comet 9P/Tempel 1 at near midnight.
Predictions are that the comet should brighten suddenly, going from 10th magnitude to around 5th magnitude (Each magnitude is 2.5 times as bright as the next. 5 magnitudes is 100 times as bright.) How long the brightening will last is unknown. The comet may not brighten at all, or it could flare, pop, or sparkle.
The impact will occur at 11pm Arizona time (12 midnight Navajo Nation time) Arizonans are in a particularly good location to view the event. Look for comet Tempel 1 by looking in the southwestern sky in the constellation Virgo, a little northeast of the star Spica. This will be about mid-way between the horizon and the highest point in the sky.
The comet will be faintly visible if you have full-sized binoculars or a telescope. The tail will stream to the left, or eastward.
Wilhelm Tempel was an astronomer who discovered many comets in the late 1800's. He discovered Tempel 1 in 1867 (not his first). Tempel 1 was lost for 18 orbits, a record, starting in 1881, after a close encounter with Jupiter. It was rediscovered in 1967, hence the extra part of its name. It orbital period is about 5.5 years, and it is a little less than 4 km long and a little less than 3 km wide. It spins one revolution every 25 hours. The orbit of 9P/Tempel 1 is relatively circular for a comet, with the furthest point from the sun still inside Jupiter's orbit, and the nearest point outside Mar's orbit. It will be right at the nearest point to the sun on July 5th.
The Deep Impact Mission launched about 6 months ago. It will launch the "Impactor" 24 hours before impact, and then make a deflection maneuver to avoid hitting 9P/Tempel 1. Scientists want to make this strike on the comet to learn about the material comets are made of, how consolidated or "clumped together" they are, and how the tails are generated.
For a whole lot more about the Deep Impact mission, go to http://deepimpact.jpl.nasa.gov or http://www.planetarysociety.org/deepimpact/.