From NAOJ: “The Deep Impact Mission Investigates the Origin of Comets”

NAOJ

NAOJ

Astrophotography・May 26, 2015
Text by: Seiji Sugita (The University of Tokyo)
Translation by: Ramsey Lundock (NAOJ)

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Sequential photographs in the mid-infrared show the conditions from one hour to several hours after the impactor released from the Deep Impact flyby spacecraft collided with the Jovian Comet Tempel 1.

NASA Deep Impact spacecraft
NASA/Deep Impact spacecreft

The red color shows carbon-rich material and green shows material rich in silicates (the main component of normal rocks). We can see that for several hours after the collision, the comet’s internal material expanded rapidly out into space, forming a fan shape. The results showed that the internal composition of Jovian (short-period) comets and long-period comets are extremely similar. This is very important data for theories about the origin of comets.

Long-period Comets and Jovian Comets

Long-period comets and Jovian comets differ both in terms of their momentum and in terms of the types of dust and gas which they expel. This is thought that they hail primarily from, respectively, the Oort Cloud at a distance of tens of thousands of astronomical units (au) from the Sun and the Kuiper Belt in the vicinity of 30-50 au. Whether the composition of objects is similar or different in these two very different locations is important information for understanding the origin of the Solar System.

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An artist’s rendering of the Oort cloud and the Kuiper belt (inset). Sizes of individual objects have been exaggerated for visibility.

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Known objects in the Kuiper belt beyond the orbit of Neptune (scale in AU; epoch as of January 2015).

But it was not known whether the difference between these two species of comets is a difference in the depletion levels of gas and dust, or if it is a difference in the internal composition from the time of formation.

To determine which is correct, it is necessary to peel off the gas-and-dust-depleted surface of a Jovian comet and observe the excavated pristine interior. This experiment was the goal of the Deep Impact Mission.

On the night of the experiment, we watched the experiment unfold from the summit of Mauna Kea. As the activity started to subside, it came as a big surprise as pristine silicate particles, typical of long-period comets, gushed out from the interior of the Jovian comet. The interiors of both have similar compositions.

See the full article here.

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The National Astronomical Observatory of Japan (NAOJ) is an astronomical research organisation comprising several facilities in Japan, as well as an observatory in Hawaii. It was established in 1988 as an amalgamation of three existing research organizations – the Tokyo Astronomical Observatory of the University of Tokyo, International Latitude Observatory of Mizusawa, and a part of Research Institute of Atmospherics of Nagoya University.

In the 2004 reform of national research organizations, NAOJ became a division of the National Institutes of Natural Sciences.

NAOJ Subaru Telescope

NAOJ Subaru Telescope interior
Subaru

ALMA Array
ALMA

sft
Solar Flare Telescope

Nobeyama Radio Telescope - Copy
Nobeyama Radio Observatory

Nobeyama Solar Radio Telescope Array
Nobeyama Radio Observatory: Solar

Misuzawa Station Japan
Mizusawa VERA Observatory

NAOJ Okayama Astrophysical Observatory Telescope
Okayama Astrophysical Observatory

The National Astronomical Observatory of Japan (NAOJ) is an astronomical research organisation comprising several facilities in Japan, as well as an observatory in Hawaii. It was established in 1988 as an amalgamation of three existing research organizations – the Tokyo Astronomical Observatory of the University of Tokyo, International Latitude Observatory of Mizusawa, and a part of Research Institute of Atmospherics of Nagoya University.

In the 2004 reform of national research organizations, NAOJ became a division of the National Institutes of Natural Sciences.