This image shows the initial ejecta that resulted when NASA's Deep Impact probe collided with Comet Tempel 1 on July 3 at 10:50 PM (MST) Image and caption credit: NASA/JPL/Caltech/UMD

For a star chart to find Comet Tempel go to Flandrau's Skywatcher's Guide for July.

For information about the talk by Deep Impact team member H. Jay Melosh on July 9 see UA News.org or scroll to the bottom of this page.

On Sunday night July 3 at 10:50 PM, NASA's Deep Impact space probe collided a 815lb solid copper projectile (the 'impactor') with a faint periodic comet named Comet Tempel 1 (9P). Comet Tempel 1, moving at the Deep Impact spacecraft at 23,000 miles per hour, collided with the impactor probe as successfully planned. The impactor smashed into the brightest portions of the comet visible to it, throwing up a debris (ejecta) blanket as the image above from the parent (flyby) spacecraft shows. Although the comet has not yet (as of July 6) brightened several magnitudes, it did brighten visually about one magnitude as reported by ground based visual observers in Arizona, with a stellar core reported as becoming visible by most observers starting around 25 minutes after impact.


Facts about Comet Tempel 1 (9P) and Deep Impact
Comet Tempel 1 has been specifically named and designated by astronomers as Comet Tempel 1 (9P). The '9P' means it's the ninth 'periodic' comet with an orbit less than 200 years, and that has been identified in its orbit around the Sun more than once. The brightest such 'short' periodic comet is also the most famous: Halley's Comet. Unlike Halley's Comet, which takes 76 years to orbit the Sun, Comet Tempel 1 has a much shorter orbit, one that lies between Mars and Jupiter and takes 5.5 years to go once around the Sun. Comet Tempel 1 is a much less active comet than Halley's as well, meaning it throws out much less dust and gas into space. Comet Tempel 1 was discovered in France in 1867 by Ernst Wilhelm Leberecht Tempel, who discovered several comets in his lifetime, some of which are associated with meteor showers. The actual physical dimension of Comet Tempel's icy-rock nucleus is 9 km long and 3 wide (about half the size of Manhattan Island in New York City). The name of the Deep Impact space probe is also the name of a movie about a comet hitting the Earth. But neither the scientists involved in the real Deep Impact mission, or the creators of the Deep Impact movie were aware of what the other was doing, so the names are mere coincidence.


Current reports on Comet Tempel after impact
By July 4th the comet was reported by some observers as running about 8th magnitude in brighness, and so brightened at most two magnitudes (from magnitude 10), or about six times brighter than it was before the impact. However as of July 6, after impact, Comet Tempel 1 is still too faint to find visually in large amateur telescopes from light polluted city locations (imaging systems are currently needed to identify it from light polluted locations). The comet is now at 9th magnitude in brightness (as of July 6), but is now not expected to become much brighter, at say 5th or 6th magnitude. As of July 6 the comet is not expected to become visible in good quality binoculars from dark sky locations or for observers using large telescopes in light polluted locations. The comet is currently visible to astronomers using very large amateur telescopes of 14 inches and greater diameter in dark sky locations and appears as a smudge of very faint light.

How bright will the comet become? How much Comet Tempel 1 will brighten in the days to come is not yet known. Astronomers, both amateur and professional, will just have to observe the comet to find out. As stated previously it is very unlikely the comet will become a naked eye object, that is one visible from light polluted locations. Sky and Telescope magazine states that the amount of brightening "will depend on how much dust was excavated in the first place, the rate at which the dust cloud expands, how long it stays concentrated and highly reflective, and whether the impact created an active region on the comet from which more material can spew out." The comet as viewed from Earth may not brighten more than it has, or it could brighten 5 magnitudes or more, making it easily visible in binoculars from dark sky locations. University of Arizona astronomer Jim Scotti, who regularly finds asteroids and comets with the Spacewatch program at Kitt Peak National Observatory, has said that what this comet will do after it gets hit by the probe "is a guess...everyone is guessing". With some comets he has said you could "sneeze at the comet and it could fall apart". And world famous comet hunter and Flandrau Adjunct Scientist Dr. David Levy is fond of saying: "Comets are like cats. They have tails and they do exactly what they want."

To allow public viewing of any resulting changes in this faint comet's brightness Flandrau Science Center will have its observatory specially open Sunday, Monday and Tuesday nights July 3, 4 & 5 for real time video screen views of Comet Tempel (direct viewing is unlikely). Due to the faintness of Comet Tempel 1, and its low altitude in the Arizona sky on Sunday night at 11PM (when the probe will impact), the comet, even brightened, may continue to be impossible to find visually in amateur telescopes from light polluted city locations. Also, the comet did not brighten fast enough after impact to be visible Sunday night in Flandrau's 16-inch observatory telescope, though it was able to be imaged by the observatory for video screen display. The best nights to view the comet should be the Monday, Tuesday and Wednesday following impact. For stargazers who want to try, the Flandrau telescope will be open from 7:30 - midnight Sunday July 3, and from 7:30-10PM Monday-Saturday. Flandrau's 16-inch observatory telescope is the only free public telescope open on a regular basis in the state of Arizona, and is normally open from 7-10 PM Monday through Wed. weather permitting.

Lastly, the University of Arizona is offering a special lecture by the University of Arizona's H. Jay Melosh of the Lunar and Planetary Lab (LPL). A member of the Deep Impact science team, Dr. Melosh has been working at the NASA Jet Propulsion Lab in Pasadena, Calif., during and after the probe-comet collision mission. Melosh will talk on "First Results from the Deep Impact Mission" in Tucson on Saturday, July 9 at 6:15 p.m. on the UA campus in the Kuiper Space Sciences Building, 1629 E. University Blvd., Tucson. Kuiper Space Sciences is directly adjacent to Flandrau Science Center. The lecture, which is part of a program sponsored by UA's Lunar and Planetary Laboratory Public Outreach Program, is free and open to the public. For more information see the news story UA News.org.