NGC 6881 HST
NGC 6881 has a dying star at its core which is about 60% of the mass of the Sun. It is an example of a quadrupolar planetary nebula, made from two pairs of bipolar lobes pointing in different directions, and consisting of four pairs of flat rings. There are also three rings in the centre.
A planetary nebula is a cloud of ionised gas, emitting light of various colours. It typically forms when a dying star — a red giant — throws off its outer layers, because of pulsations and strong stellar winds.
The star’s exposed hot, luminous core starts emitting ultraviolet radiation, exciting the outer layers of the star, which then become a newly born planetary nebula. At some point, the nebula is bound to dissolve in space, leaving the central star as a white dwarf — the final evolutionary state of stars.
The name “planetary” dates back to the 18th century, when such nebulae were first discovered — and when viewed through small optical telescopes, they looked a lot like giant planets.
Planetary nebulae usually live for a few tens of thousands of years, a short phase in the lifetime of a star.
The image was taken through three filters which isolate the specific wavelength of light emitted by nitrogen (shown in red), hydrogen (shown in green) and oxygen (shown in blue).
Relevante Artikel
NGC 6881NGC 6881 ist ein Planetarischer Nebel im Sternbild Schwan am Nordsternhimmel, der schätzungsweise 6000 Lichtjahre vom Sonnensystem entfernt ist. Er besteht aus einem inneren Nebel, etwa ein Fünftel Lichtjahr durchmessend, und einer symmetrischen Struktur, etwa ein Lichtjahr von Spitze zu Spitze. Im Zentrum des Objekts befindet sich ein sterbender Stern mit etwa 60 Prozent der Masse unserer Sonne. .. weiterlesen