Starship Asterisk*

Björn wrote:
I think it has a fish-like appearance
with a big head and a long tail-like body

Björn wrote:I think it has a fish-like appearance with a big head and a long tail-like body

Boomer12k wrote:Could what we see also be the affect of filters. I have seen other planetary nebula in different light and time exposures to give a totally different depiction of the Nebula.

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ta152h0 wrote:
to our ancient ancestors, unpolluted by artificial light, this object would just be another dot of light, right ?

• Only if they had telescopes.
  
  (At the distance of NGC 5189 a 10⁴ solar luminosity star would barely be visible.)

http://en.wikipedia.org/wiki/Asymptotic_giant_branch#Circumstellar_envelopes_of_AGB_stars wrote:

[b][color=#006F00]Evolution of stars of different masses on the Hertzsprung-Russell diagram. The asymptotic giant branch is marked AGB in the case of a star of 2 solar masses.[/color][/b]

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<<The asymptotic giant branch is the region of the Hertzsprung-Russell diagram populated by evolving low to medium-mass stars. This is a period of stellar evolution undertaken by all low to intermediate mass stars (0.6–10 solar masses) late in their lives.

Observationally, an asymptotic giant branch (AGB) star will appear as a red giant. Its interior structure is characterized by a central and inert core of carbon and oxygen, a shell where helium is undergoing fusion to form carbon (known as helium burning), another shell where hydrogen is undergoing fusion forming helium (known as hydrogen burning) and a very large envelope of material of composition similar to normal stars.

The extensive mass loss of AGB stars means that they are surrounded by an extended circumstellar envelope (CSE). Given a mean AGB lifetime of one Myr and an outer velocity of 10 km/s, its maximum radius can be estimated to be roughly 3×10¹⁴ km (30 light years). This is a maximum value since the wind material will start to mix with the interstellar medium at very large radii, and it also assumes that there is no velocity difference between the star and the interstellar gas. Dynamically most of the interesting action is quite close to the star, where the wind is launched and the mass loss rate is determined. However, the outer layers of the CSE show chemically interesting processes, and due to size and lower optical depth are easier to observe.

Guestation wrote:Maybe a double star each exploding simultaneously.

Boomer12k wrote:Could what we see also be the affect of filters. I have seen other planetary nebula in different light and time exposures to give a totally different depiction of the Nebula.

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Ann wrote:

Boomer12k wrote:Could what we see also be the affect of filters. I have seen other planetary nebula in different light and time exposures to give a totally different depiction of the Nebula.

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Absolutely, the filters affect the appearance of the nebula immensely.

On another note, and with apologies to William Blake...

Plane! Tary! burning bright
In the vastness of the night
What immortal hand or eye
Could frame thy fearful symmetry?

Ann

Raven wrote:Now this is what happens when you try to reverse temporal trajectory in your TARDIS without first pausing and offsetting your physical coordinates by at least one external diameter. Your time capsule overlaps itself while traveling in opposite temporal directions, paradox ensues, and the picture shows the intermediate outcome, a navigational hazard for Gallifreyan generations. Eschew paradox!