Comet Hartley 2 - additional findings

A combination of the photographs obtained by the EPOXI spacecraft that passed by the comet and observations lasting several months by the SOHO satellite gave the researchers a rare opportunity to observe the process of ejecting large amounts of ice in the comet

Comet Hartley 2 that was recently photographed by the EPOXI spacecraft (originally the Deep Impact spacecraft) that passed by it was also observed and measured by two satellites and a space telescope. One satellite is the SOHO (Solar and Heliospheric Observer), it is actually a satellite that orbits the Earth from a distance of 1.5 million km and is mainly intended to observe the Sun (1) and the other satellite is the NEOWISE- (Near Earth Objects Wide Field Infra Red Survey Explorer). This satellite was launched in December 2009 and is designed to survey the sky, including small bodies such as asteroids and comets in the solar system (2). Among other things, he also aimed at the comet Hartley 2. The space telescope that was aimed at him is the Herschel telescope (3).

A combination of the photographs obtained by the EPOXI spacecraft that passed by the comet and observations lasting several months by the SOHO satellite gave the researchers a rare opportunity to observe the process of ejecting large amounts of ice in the comet. It turned out to be an unusual comet that blows ice blocks and emits water at a greater rate than expected. These emissions can tell about what existed in the first days of the formation of the solar system. The device found in SOHO and used for this purpose is called SWAN (Solar Wind Anistropy) and is designed to observe the emission of gases from comets.

Its main purpose was to measure the explosiveness of hydrogen atoms in the sky. These measurements help learn about the Sun's magnetic environment by tracking the movement of particles from interstellar streams. In addition, this device can also track comets which are usually surrounded by an extremely thin atmosphere of water vapor. Under the influence of the ultraviolet radiation from the sun, the hydrogen atoms detach from the water molecules at high speeds and form a large cloud (coma) of hydrogen. This cloud absorbs the sunlight and emits it. This phenomenon can be observed using the SWAN photographs. Tracking these clouds makes it possible to determine the amount of water that evaporates from the comet over time. From this set of collected data it became clear that the water production in Shavit in 1997 was 3 times greater than what was observed in 2010. On September 30.9.2010, 2.5, the amount of hydrogen emitted was 6 times greater than on a normal day and then this amount decreased gradually over 2 weeks. To get a broad perspective regarding Comet Hartley 1, comets whose time around the sun is the same as his were also observed (XNUMX).

The observations made from the Herschel space telescope revealed that the comet also contains heavy water and that the ratio between this water and light water is similar to that found on Earth. It was found that the amount of heavy water in the comet is half of that found in other comets observed by this telescope (3). The special shape of the comet resembles the shape of a bone and the great difference between the two lobes raised the hypothesis that these are two comets that were each formed in a different place in the solar system. In the process of a collision course, they hit each other and the middle part of Hartley 2 was filled with ice and dust originating from fragments created during the collision (4).

Geographically, the release of water and 2CO is not homogeneously distributed over the surface of the comet. When the spacecraft passed by the comet the release of 2CO was observed at the edges of the comet. The massive water emission was in the middle with very little emission of 2CO. The material ejected at the edges of the comet returned to the ground and was redeposited (5). Compared to other comets of the same size, the amount of water ejected from it is the largest. During 9 days in September 2011, the amount of cyanide (CN) was several orders of magnitude greater than on other days. This phenomenon was named the cyanide anomaly (CN anomaly). The increase in the amount of water he emitted then was small. It may be that the cyanide gives researchers the opportunity to study the formation and development of comets. At the same time as the emission of other observed gases, there was also a large emission of dust (5), what is interesting about the comet is that the sublimation of the water and other volatile substances found inside it is slow (4). The 2CO emission continued even when the comet was 2.3 AU away from the Sun (6).

The NEOWISE observation made in the same segment where the comet is moving close to the Sun showed that the comet is emitting a tail of gravel made of tiny objects the size of golf balls that continue to survive at a greater distance from the sun than previously thought (6). At the edges of the comet there are glittering blocks that are 80 meters wide and 50 meters high and smaller bodies whose light reflection is 2-3 times greater than their surroundings. The big surprise of the researchers was when it became clear that the comet rotates around another axis of itself (5).

Sources

1. Fox. KC- "SOHO watches a comet fading away" 29.7.2011

http://www.spacedaily.com/reports/ SOHO_ Watches_ a_ Comet_ Fading_ Away_999html

2. http://www.nasa.gov/mission-pages/WISE/news/wise20110201.html

3. PIA14737: Heavy and light just right

http://photojournal.jpl.nasa.gov/catalog/ PIA14737

4. "Hyperactive Hartley 2 has a split history" 10.10.2011

http://www.spacedaily.com/reports/ Hyperactive_ Hartley _2_Has_ a _Split _History_999html

5. "Hyperactive Hartley 2" 22.6.2011

http://www.spacedaily.com/reports/ Hyperactive_ Hartley _2_999html

6. "Comet Hartley 2 leaves a bumpy trail" 15.7.2011

http://www.spacedaily.com/reports/ Comet _Hartley _2_ Leaves_ a_ Bumpy_ Trail_999html