NGC40 - Noao-ngc40w
This is a combination of seven exposures through B, V and R filters taken in November of 1996 at the 3.5-meter WIYN telescope. Planetary nebula NGC40 is a low-excitation nebula in the constellation of Cepheus, about 4000 light-years away from Earth. The central star is fairly bright (about magnitude 11.6), has a mass of around 0.7 solar masses, and is much hotter than would be expected just from the properties of the surrounding nebula. This is because its temperature of around 90000 degrees should be hot enough to excite the nebula to a much higher ionization state than is found. This suggests the presence of shielding material between the star and the glowing nebula. Such higher density material could form in the shock interface between the fast wind (about 1800km/s) from the central star and the nebular shells themselves. The nebular material covers about 25% of the sky as viewed by the central star, implying rather asymmetric mass-loss from the star in its asymptotic giant branch stage. NGC40 has an extended halo, not seen here, probably caused by earlier mass ejection. Location: 00 13.0 +72 32 (2000), size: about 0.6 light-years across.
Credit:
WIYN/NOIRLab/NSF |
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NGC 40NGC 40 ist ein planetarischer Nebel im Sternbild Kepheus am Nordsternhimmel. Der Stern, der seine äußere Hülle abgestoßen hat, weist eine Temperatur von 50.000 Grad Celsius auf und besitzt in etwa die Größe der Erde. Dieser Zentralstern hat eine für Weiße Zwerge typische enorm hohe Dichte und damit trotz seines geringen Durchmessers etwa 0,7 Sonnenmassen. Die ihn umgebenden Gase haben eine Temperatur von 10.000 Grad Celsius. Das Alter von NGC 40 wird auf rund 4.500 Jahre geschätzt, wobei sich seine Gaswolken immer noch mit etwa 29 km/s ausdehnen. .. weiterlesen