by Chris Peterson » Sat Jul 30, 2016 2:19 pm
Ann wrote:Chris Peterson wrote:starsurfer wrote:
Jets in planetary nebulae usually arise from an accretion disk around the central star. Also some planetary nebulae are known to have OIII blobs at the outer edges visible in deep images, so I guess these might be high excitation?
Well, it's a big universe and there's a lot of stuff out there, but are there planetary nebulas where their central stars have accretion discs? I can't think of any, and it isn't clear to me how that could even happen. Planetary nebulas are just the glow of ejected gas from late-state, lower mass stars which are hot enough to ionize that gas. Isotropically hot, no stellar structure, no stellar jets, just 30,000 K blackbodies.
HEIC/ESO has just reported about a white dwarf star with a jet.
Are these "fully developed" white dwarf stars different from the central stars of planetary nebulas? Or is it true after all that the central stars of planetary nebulas can have jets?
To be clear, I'm not arguing that such stars
can't have jets, only that I'm not familiar with any PNs where the central star (or stars if binary) actually
do have them. The formation process for PNs seems rather gentle, and has the property (apparently) of clearing the region immediately around the star of material. That means that you don't have anything to accrete, and that means you're not going to have jets.
In a binary system, one of the stars can provide material to the other, which is what we have in the report above. Whether there are examples of such stars at the center of PNs, however, I don't know.
[quote="Ann"][quote="Chris Peterson"][quote="starsurfer"]
Jets in planetary nebulae usually arise from an accretion disk around the central star. Also some planetary nebulae are known to have OIII blobs at the outer edges visible in deep images, so I guess these might be high excitation?[/quote]
Well, it's a big universe and there's a lot of stuff out there, but are there planetary nebulas where their central stars have accretion discs? I can't think of any, and it isn't clear to me how that could even happen. Planetary nebulas are just the glow of ejected gas from late-state, lower mass stars which are hot enough to ionize that gas. Isotropically hot, no stellar structure, no stellar jets, just 30,000 K blackbodies.[/quote]
[url=http://asterisk.apod.com/viewtopic.php?f=31&t=36201&p=260403#p260403]HEIC/ESO[/url] has just reported about a white dwarf star with a jet.
Are these "fully developed" white dwarf stars different from the central stars of planetary nebulas? Or is it true after all that the central stars of planetary nebulas can have jets?[/quote]
To be clear, I'm not arguing that such stars [i]can't[/i] have jets, only that I'm not familiar with any PNs where the central star (or stars if binary) actually [i]do [/i]have them. The formation process for PNs seems rather gentle, and has the property (apparently) of clearing the region immediately around the star of material. That means that you don't have anything to accrete, and that means you're not going to have jets.
In a binary system, one of the stars can provide material to the other, which is what we have in the report above. Whether there are examples of such stars at the center of PNs, however, I don't know.