Comet Hartley 2

103P/Hartley happening around us, every 6 years

Every 6,46 years, the small comet Hartley 2 (103 / P Hartley) passes near the Earth and the Sun. 103P/Hartley or comet Hartley 2, is a periodic comet discovered by Malcolm Hartley in 1986 with the Schmidt telescope at the Siding Spring Observatory, Australia. In October 2010 it passed near Earth and the Sun. Against this backdrop of night sky of October 2, 2010 you can see right image, the comet dragging her beautiful hair greenish.
It shared the image with the emission nebula NGC 281 (left) and stars in the constellation Cassiopeia (center). The shape of the nebula NGC 281 earned him the nickname Pacman Nebula.
The nucleus of the comet has left a small trail of light on the sensors during the time of exposure required for shooting this photo. Comet Harley 2 with its green tail, is closely watched, Deep Impact is not the only observer space, WISE and the Hubble also observed. On November 4, 2010, the spacecraft's new mission EPOXI Deep Impact, will increase to 700 km from the comet nucleus. This comet nucleus active, is similar in size and mass, Tempel-1. For the occasion, a new mission, called EPOXI,, aims to fly Hartley 2 during its passage. This is the Deep Impact spacecraft that scientists have delegated this investigation.

Developed in December 2007, the trip took over 2 ½ years. The probe hit the comet after a trip equivalent to 18 times the Earth-Sun distance and used three times, the gravity assist from Earth. The mission aims to draw maps of temperature, measure its size, albedo, modeling its nucleus, to study the distribution of dust and gas, search for volatile compounds, identify surface features, observed distribution of craters,...

Image: Comet Harley 2 with its green tail, rose to 18 million kilometers, 20 October 2010 it was closer to Earth. Deep Impact is not the only observer space, WISE and Hubble also observe the comet Hartley 2. Its orbital period is 6.46 years.

Deep Impact flew over the nucleus of comet

November 4, 2010, the former American probe Deep Impact, Epoxy renamed for the occasion, flew over the nucleus of comet Hartley 2 at a distance of 700 km. Comet 103P/Hartley 2 is a young and active comet with green specialists will study the active regions that release the gas and dust at the root of the hair.
In 2010, commenting on the radar images of the comet nucleus taken by the giant radio telescope at Arecibo, Tim Larson, head of the mission Epoxy, said: "She looks a bit like cross between a bowling pin and a pickle and darkens through space at 37 kilometers per second. " Kernel size is estimated at 2 km long and 700 meters wide. The comet turns on itself in 18 hours.
The meeting between the probe and the comet Epoxi was held November 4, 2010 to 15 hours French time.
The U.S. probe has crossed its target to more than 8 kilometers per second.
The images of comet Hartley 2 show clearly its shape into a pickle and various jets of gas and dust.

When a comet approaches the Sun, the outer layer vaporizes and forms a gaseous envelope (coma). Solar radiation exerts pressure on the coma and force particles and gases away from the Sun, forming a glowing tail of ionized particles.

Image: View of core 103P/Hartley 2 made by the probe Epoxi when it is passed closest of the comet the 04/11/2010. The smallest details visible on the surface are approximately 10 meters. Kernel size is estimated at 2 km. © NASA.

The green comet

The images of the coma of comet Hartley 2 show a beautiful green color.
The coma of comets, is a trail extended by several tens of thousands of miles following the nucleus opposite the sun. These jets from the sublimation of ice due to solar radiation, because it's the wind and thus the solar radiation pressure pushes dust grains of comet.
The hair is composed of gas and dust grains torn from the comet's surface ice. The green color is produced by the fluorescence of cyanogen (C2N2) and diatomic carbon (C2).

Other comets have brought this beautiful green color, like Hale-Bopp in 1995, Machholtz in 2005, 2009 or Lulin Mc Naught in 2010.

Image: Example of green hair when crossing the comet Lulin 02/04/2009.