Héliopause

Structure

The Solar wind breath a “bubble” in the interstellar Environment (the Gaz of Hélium and Hydrogène rarefied which fills up the Galaxie). This bubble is called Héliosphère, and its external limit is where the push of the solar wind is not sufficient any more to push back the interstellar environment, made up of the stellar winds of the stars close and the gas clouds between these stars. This limit is known as being the héliopause and is often regarded as being the Frontière external of the Solar system.

Within the héliopause is a limit called “final Choc” where particle S of solar wind Supersonique S are slowed down at speeds Subsonique S by the interstellar environment. The layer between the final shock and the héliopause is known like the Héliogaine ( heliosheath in English). When particles emitted by the sun enter in collision with the interstellar particles, they slow down by emitting energy (being heated). Many particles accumulate with and around the héliopause, strongly energized by their deceleration, creating a Shock wave.

The distance to the héliopause is not known precisely. It is probably much shorter side of the solar system facing the orbital movement through the galaxy. It can also vary according to the current speed of the solar wind and the local density of the interstellar environment. It is known to be located well beyond the Orbite of Pluton.

Study

The current mission of the Probe S To travel 1 and Voyager 2 is to discover and study the final shock, the héliogaine and the héliopause. In 2003, the review Nature published two scientific articles successively on this subject, in which the authors interpreted measurements To travel 1 for or against the attack of the final shock by the probe. The detector of plasma has not been operational any more for several years, but the scientists study the data of other detectors and the controversy exists because in August 2002 (with 84,7 UA of the sun), Voyager 1 would have passed beyond the final shock and, in February 2003 (with 87 UA), it would have returned inside. The most current interpretation seems to be that the limits defined here are highly fluctuating (undoubtedly under the direct influence of the solar wind). But the interpretation of the data remains prone to guarantee and it is possible that the phenomenon observed was only one harbinger of the final shock itself.

In May 2005 NASA announces that thanks to new data the scientific community agrees to say that Voyager 1 crossed the final shock and entered the héliogaine. To travel should reach the héliopause from here 2020 at the rate of 3 UA per annum and should have enough energy to transmit information.

Previously, Pioneer 10 was the first object manufactured by the Homme to cross the héliopause in 1987. But information that it could provide to this occasion remained very compartmental compared to what is awaited probes Voyager 1 and To travel 2. Nevertheless, the budgetary difficulties of NASA for the preparation of the exploration of Mars could lead the space agency to stop the program at the moment-even brutally when it can bring back information in absolutely single matter.

By Analogie, an alternative definition is that the héliopause is the Magnétopause between the Magnétosphère of the solar system and the currents of plasma of the galaxy.

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