High speed cloud
High-speed clouds (also HVC , for High Velocity Cloud ) are astronomical phenomena made of neutral hydrogen .
Their exact distance is not yet well known. One differentiates essentially:
- HVCs in the Halo of the Milky Way ,
- HVCs associated with Magellanic Current
- HVCs in the intergalactic space of the local group .
Details
An essential characteristic of these gas clouds is that their movement is in no way compatible with the galactic rotation; they move on different orbits and at higher speeds than the rest of the matter in the Milky Way. HVCs have a lower metallicity than interstellar clouds in the Milky Way.
The origin of the high-speed clouds is not yet fully understood. It is assumed that they are remnants from the time the Milky Way or other galaxies were formed or fragments of satellite galaxies that were torn out by gravitational interaction during the merging with our galaxy .
Examples
- Magellanic Stream : A hydrogenbridge that connectsthe Magellanic Clouds with each other and with the Milky Way.
- Complex H : A compact HVC that moves in the opposite direction to the rotation of the Milky Way and is mistaken for the remnant of a satellite galaxy.
- Smith cloud
- HVC 127-41-330 : The first known HVC that is not associated with our galaxy and is about 2.3 million light years away. It is now mistaken for a dark galaxy .
Web links
- What is a high speed cloud? from the alpha-Centauri television series(approx. 15 minutes). First broadcast on Nov 5, 2000.
- Mysterious gas clouds just "galaxy debris, " astronews.com
- High-speed gas clouds - Astronomie.de ( Memento from February 21, 2008 in the Internet Archive )
- High Velocity Clouds and the Milky Way - Astronomy Picture of the Day of December 14, 1999.
- Fog Lifts on Source of High-Speed Galactic Clouds , Space.com (English)
Individual evidence
- ↑ Cosmic Galaxy Food , extrasolar-planets.com
- ↑ Starless galaxy hides in the dark , NewScientist, October 18, 2003