New molecules around old stars
Using ESA's Herschel space observatory, astronomers have discovered that a molecule vital for creating water exists in the burning embers of dying Sun-like stars.
When low- to middleweight stars like our Sun approach the end of their lives, they eventually become dense, white dwarf stars. In doing so, they cast off their outer layers of dust and gas into space, creating a kaleidoscope of intricate patterns known as planetary nebulas.
Herschel image of the Helix Nebula using the SPIRE instrument at wavelengths around 250 micrometres, superimposed on Hubble image of the nebula. The spectrum corresponds to the outer region of the Helix Nebula outlined on the SPIRE image. It identifies the OH+ molecular ion, which is needed for the formation of water.
Credits: Hubble image: NASA/ESA/C.R. O'Dell (Vanderbilt University), M. Meixner & P. McCullough (STScI); Herschel image: ESA/Herschel/SPIRE/MESS Consortium/M. Etxaluze et al.
Like the dramatic supernova explosions of weightier stars, the death cries of the stars responsible for planetary nebulas also enrich the local interstellar environment with elements from which the next generations of stars are born.
The remaining core of the star eventually becomes a hot white dwarf pouring out ultraviolet radiation into its surroundings.
Two separate studies using Herschel astronomers have discovered that a molecule (OH+) vital to the formation of water seems to rather like this harsh environment, and perhaps even depends upon it to form.
- "Herschel planetary nebula survey (HerPlaNS). First detection of OH+ in planetary nebulae," by I. Aleman et al., Astronomy & Astrophysics.
- "Herschel spectral-mapping of the Helix Nebula (NGC 7293): extended CO photodissociation and OH+ emission," by M. Etxaluze et al., Astronomy & Astrophysics.
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