Gemini Observatory: Exploring the Universe, Sharing its Wonders

Deep Impact Captured by Gemini

July 2, 2005

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The Gemini North telescope on Mauna Kea successfully captured the dramatic fireworks display produced by the collision of NASA's Deep Impact probe with Comet 9P/Tempel 1. Researchers in two control rooms on Hawaii’s Big Island (on Mauna Kea and in Hilo) were able to keep enough composure amid an almost giddy excitement to perform a preliminary analysis of the data. They concluded from the mid-infrared spectroscopic observations that there was strong evidence for silicates or rocky material exposed by the impact. Little doubt remains that the unprecedented quality of the Gemini data will keep astronomers busy for years.

Figure 1. Gemini North Michelle mid-infrared (11.6 micron) false-color images of 9P/Temple 10 minutes before impact (left), 3 hours after (center) and 24 hours after impact (right). Scale and orientation are the same for all images.

“The properties of the mid-infrared light were completely transformed after impact,” said David Harker of the University of San Diego, co-investigator for the research team. “In addition to brightening by a factor of about 4, the characteristics of the mid-infrared light was like a chameleon and within five minutes of the collision it looked like an entirely new object.” Harker’s research partner Chick Woodward of the University of Minnesota speculated further, “We are possibly seeing crystalline silicates which might even be similar to the beach sand here in Hawaii! This data will keep us busy trying to figure out the size and composition of these grains to better understand the similarities and differences between the material contained within comets and other bodies in the solar system.”

Figure 2. This T-ReCS observation from Gemini South in Chile of Comet P9/Tempel was obtained at mid-infrared wavelengths (11.7um). This type of light acts as a tracer of the extended distribution of dust in the coma of the comet. A comet's coma is the fuzzy haze of gas and dust that surrounds, and is produced by, the comet's true nucleus. In this picture, Comet Tempel's coma is seen to extend to sizes larger than 9 arcseconds (5800 km or 3700 miles) in diameter, which is larger than the continental United States (2450 miles).

The impact occurred on the nucleus of the comet which is so small and surrounded by such a bright coma, that it cannot be seen directly in this image. However, the material dispersed by the impact injected fresh new material to the coma. Measurements of the coma in this image show that it is still at an elevated brightness 19 hours after impact at a level 20% brighter than before impact.

These T-ReCS observations were part of a coordinated effort between the the twin Magellan 6.5meter telescopes and the DuPont 100-inch telescope of Las Campanas Observatory, Spitzer Space Telescope, and Gemini South Telescope. The project was headed by Dave Osip of Las Campanas and James De Buizer of Gemini South. Co-investigators are Joanna Thomas-Osip (Las Campanas Observatory), Susan Lederer (California State University San Bernadino), and Casey Lisse (Johns Hopkins Applied Physics Laboratory/University of Maryland).

In addition to the spectroscopic observations, before-and-after images were also obtained by the Gemini telescope in thermal infrared light and can be seen in Figure 1. Gemini monitored the comet for several weeks prior to the impact and will continue to watch it through the end of July.

Figure 3. Subaru Gemini Deep Impact Mid Infrared Collaboration. Subaru team is led by Prof. Sugita (University of Tokyo) and the Gemini team by Dr. Dave Harker (University of California, San Diego).

The Gemini observations were part of a coordinated effort between the W.M. Keck, Subaru and Gemini Observatories so that each could concentrate on different observations and provide a complete, complementary “picture” of the impact. Astronomers anticipate that the data gathered from the largest and most sophisticated set of telescopes positioned to see the impact will add considerably to our understanding of comets as dynamic probes of our solar system’s early evolution some 4.5-5 billion years ago.

The Gemini observations were made using Michelle, the facility mid-infrared imager/spectrograph built at the Royal Observatory of Edinburgh (ROE) in the UK. The instrument has unique capabilities in the mid-infrared especially at Gemini which uses protected silver coatings on main mirrors to provide exceptional performance in the “thermal” or mid-infrared part of the spectrum.

The Gemini Observatory is an international collaboration with two identical 8-meter telescopes. The Frederick C. Gillett Gemini Telescope is located on Mauna Kea, Hawai'i (Gemini North) and the other telescope on Cerro Pachón in central Chile (Gemini South); together the twin telescopes provide full coverage over both hemispheres of the sky. The telescopes incorporate technologies that allow large, relatively thin mirrors, under active control, to collect and focus both visible and infrared radiation from space.

The Gemini Observatory provides the astronomical communities in six partner countries with state-of-the-art astronomical facilities that allocate observing time in proportion to each country's contribution. In addition to financial support, each country also contributes significant scientific and technical resources. The national research agencies that form the Gemini partnership include: the US National Science Foundation (NSF), the Canadian National Research Council (NRC), the Chilean Comisión Nacional de Investigación Cientifica y Tecnológica (CONICYT), the Australian Research Council (ARC), the Argentinean Ministerio de Ciencia, Tecnología e Innovación Productiva, and the Brazilian Ministério da Ciência, Tecnologia e Inovação. The observatory is managed by the Association of Universities for Research in Astronomy, Inc. (AURA) under a cooperative agreement with the NSF. The NSF also serves as the executive agency for the international partnership.