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Deep Impact Captured by Gemini

July 2, 2005

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.

Full-Resolution Image

“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.

Figure 4. White Board modeling of the predicted mid infrared spectrum.

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.

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El telescopio de Gemini Norte ubicado en Mauna Kea captó exitosamente el impresionante espectáculo pirotécnico que produjo el choque del Impacto Profundo de la Nasa con el Cometa 9P/Tempel 1. Investigadores ubicados en dos salas de control en la Isla Grande de Hawaii (en Mauna Kea y en Hilo) fueron capaces de mantener la compostura en medio de toda la emoción y realizar un análisis preliminary de los datos obtenidos. De acuerdo a las observaciones espectroscópicas del mediano infrarrojo, ellos pudieron concluir que había una fuerte evidencia de silicates o material rocoso expuesto por el impacto. No hay duda alguna que la calidad sin precedentes de los datos obtenidos por Gemini mantendrá a los astrónomos ocupados por años.

Figura 1. Imágenes del 9P/Temple I captadas por el instrumento Michelle de mediano infrarrojo en Gemini Norte, con colores no reales, 10 minutos antes del impacto (izquierda), 3 horas después (centro) y 24 horas después de la colisión (derecha) . La escala y orientación son las mismas para todas las imagines.

Imagen-en alta resolución.

“Las propiedades en la luz del mediano infrarrojo fueron completamente transformadas después del impacto” señaló David Harker de la Universidad de San Diego, co investigador del equipo de investigación. “Además de la brillantez de un factor de más o menos 4, las características de la luz en el mediano infrarrojo fue como un camaleón y en apenas 5 minutos desde la collision, se veía como un objeto completamente nuevo”. El compañero de investigación de Harker, Chick Woodward de la Universidad de Minnesota, especuló aún más allá “Posiblemente estemos viendo silicates cristalinos los que podrían ser incluso similares a la arena de la playa acá en Hawaii! Esta información nos mantendrá ocupados tratando de dilucidar el tamaño y la composición de esos granos para entender major las similitudes y diferencias entre el material contenido dentro de los cometas y otros cuerpos en el sistema solar.”

Además de las observaciones espectroscópicas, las imeagenes del antes y después también fueron obtenidas por el telescopio de Gemini en la luz termal infrarroja y puede apreciarse en la Figura 1. Gemini monitoreó el cometa por varias semanas antes del impacto y continuará observándolo hasta fines del mes de Julio.

Las observaciones de Gemini formaban parte de un esfuerzo conjunto entre los observatorios W.M.Keck, Subaru y Gemini de modo que cada uno se concentrara en obserrvaciones distintas y entregara un completo, cuadro complementario del impacto. Los astrónomos anticiparon que los datos recogidos del meas grande y sofisticado set de telescopios posicionado para ver el impacto agregará mucha información a nuestro entendimiento sobre los cometas como pruebas dinámicas de la temprana evolución de nuestro Sistema Solar hace algunos 4.5- 5 billones de años atrás.

Las observaciones de Gemini se realizaron utilizando Michelle, el espectrógrafo en el mediano infrarrojo construido en el Royal Observatorio de Edimburgo (ROE) en el Reino Unido. El instrumento tiene capacidades únicas en el mediano infrarrojo especialmente en Gemini ya que utiliza recubrimiento protegidos de palta en los espejos primaries para brindar un trabajo excepcional en el parte mediana infrarroja “termal” del espectro.