Starship Asterisk*

MarkBour wrote:I suppose we don't know for certain that the nebula is spherical, but it would seem to provide strong evidence, nonetheless.

neufer wrote: ... wikipedia article ...

Ron-Astro Pharmacist wrote:http://www.rochester.edu/news/show.php?id=3123

Chris Peterson wrote:

Ron-Astro Pharmacist wrote:I think I've asked this before but should the original star had gas giant planets within close proximity (or far) from the star sloughing off matter – could their remnants be noticeable or dectected amongst the star material being ejected?

The creation of a planetary nebula is actually pretty gentle. Any planets in the system should be largely unaffected, although their orbits will necessarily change somewhat because of the lost central mass. But it's reasonable to assume that most planets would still be in orbit. They wouldn't have a visible effect on the nebula, but could potentially be detected using one of the techniques used for doing so (transits, Doppler, direct imaging, etc).

MarkBour wrote:
So, I suppose, to figure out the expansion rate from a Doppler effect, you are looking at the difference between the largest and the smallest values? Does one have a way to sample all sorts of small locations from the region? Is there any way to make sure that the Doppler measurements are actually coming from the nebula itself? I mean, I am imagining you are looking at some emission spectra.

• All your assumptions are correct. According to Wikipedia:

http://en.wikipedia.org/wiki/Cat's_Eye_Nebula wrote:
<<The Cat's Eye Nebula (or NGC 6543) is a well-studied planetary nebula. While the bright inner nebula is rather small—the major axis of the inner ellipse is 16.1 arcseconds, while the distance between the condensations is 24.7 arcseconds—it has an extended halo of matter that the progenitor star ejected during its red giant phase. This halo extends over a diameter of about 300 arcseconds (5 arcminutes).

In recent years observations made using the Hubble Space Telescope have allowed a new method of determining distances [to planetary nebula]. All planetary nebulae are expanding, and observations several years apart and with high enough angular resolution will reveal the growth of the nebula in the plane of the sky. This is typically very small—only a few milliarcseconds a year or less. Spectroscopic observations can reveal the velocity of expansion of the nebula along the line of sight using the Doppler effect. Then, comparing the angular expansion with the known expansion velocity, the distance to the nebula can be calculated.

Hubble Space Telescope observations of NGC 6543 several years apart have been used to calculate its distance. Its [current] angular expansion rate is 3.457 milliarcseconds per year, while its [current] expansion velocity along the line of sight has been found to be 16.4 km/s. Combining these two results implies that NGC 6543 is 1001 ± 269 parsecs, or about 3300 light-years away from Earth.

The angular expansion of the nebula can also be used to estimate its age. If it has been expanding at a constant rate of 10 milliarcseconds a year, then it would take 1000 ± 260 years to reach [an average inner core] diameter of 20 arcseconds. This may be an upper limit to the age, as ejected material will be slowed as it encounters material ejected from the star at earlier stages of its evolution, as well as the interstellar medium.>>

neufer wrote:

MarkBour wrote:
How has an estimate of the age of the outer filaments been made?

Basically he same way the age of the universe (from the Big Bang) is determined:

• 1) A Doppler measurement of the current expansion rate in combination
  
  2) with a simple physical model of the average expansion rate over time.

Run the model in reverse back to the start of the "explosion."

Ron-Astro Pharmacist wrote:I think I've asked this before but should the original star had gas giant planets within close proximity (or far) from the star sloughing off matter – could their remnants be noticeable or dectected amongst the star material being ejected?

BDanielMayfield wrote:

neufer wrote:
Perhaps it used to be one of the "wing tips" of the "very central region."

But this outer feature is asymmetrical with respect to the central star. I could go along with your suggestion if there was something like it on the left, but there isn't.

Could this comet like object be caused by something in orbit of the central star interacting with its ejecta?

http://en.wikipedia.org/wiki/Cat%27s_Eye_Nebula#Kinematics_and_morphology wrote:
<<The Cat's Eye Nebula is structurally a very complex nebula, and the mechanism or mechanisms that have given rise to its complicated morphology are not well understood. It is suspected that the central star of the nebula may be a binary star. The existence of an accretion disk caused by mass transfer between the two components of the system may give rise to polar jets, which would interact with previously ejected material. Over time, the direction of the polar jets would vary due to precession.>>

Chris Peterson wrote:

BDanielMayfield wrote:I was thinking three and even four dimensionally, and I do think it has another star nearby. I was thinking that there might even be a star somewhere close to or embedded inside the brighter part of the halo on the right side, lighting it up. Something has to be making that part of the halo brighter. What do you think?

Yes, but keep in mind that the halo is barely brighter than the sky background- orders of magnitude dimmer than the central planetary nebula (composited from an HST image). The halo is made from narrowband images, which dramatically reduce the intensity of any stars in the field. Bottom line: it's really difficult to make any solid assessments about how bright anything is here. But most likely, virtually all the light of the halo is emitted, not reflected. The bright area to the right is larger than other bright spots, but not brighter. I think it's probably just another region that's shocked, or is just a little denser and therefore brighter from the stimulation of the central star.

BDanielMayfield wrote:I was thinking three and even four dimensionally, and I do think it has another star nearby. I was thinking that there might even be a star somewhere close to or embedded inside the brighter part of the halo on the right side, lighting it up. Something has to be making that part of the halo brighter. What do you think?

geckzilla wrote:

BDanielMayfield wrote:One other thing though. I wonder what might account for the brightest part of the halo on the right side?

It's a mess blowing off your outer layers, especially if you've got another star orbiting nearby. You should try to think of its three dimensional structure. It's too easy to forget that we are viewing a spherical structure when they look so much like they are flat disks and we just happen to view them face on.

BDanielMayfield wrote:One other thing though. I wonder what might account for the brightest part of the halo on the right side?

Chris Peterson wrote:

meadowlark7 wrote:
As the sun revolves around the Milky Way in a span of several hundred million years, will it likely pass through dust clouds or star forming regions and perhaps pick up mass that will defer its ultimate demise?

The Solar System will certainly pass through dust, and possibly some active star forming regions. Neither will have any effect on it. The densest gas and dust regions are still hard vacuums, and even the paltry wind from our stable little star will blow away anything long before it could be captured and add any mass.

• Except, perhaps, for some ENAMAss:

http://en.wikipedia.org/wiki/IBEX wrote:
<<IBEX is collecting Energetic neutral atom (ENA) emissions that are traveling through the solar system to Earth that cannot be measured by conventional telescopes. These ENAs are created on the boundary of our Solar System by the interactions between solar wind particles and interstellar medium particles.

On the average IBEX-Hi detects about 500 particles a day, and IBEX-Low, less than 100. By 2012, over 100 scientific papers related to IBEX were published, described by the PI as "an incredible scientific harvest".>>

meadowlark7 wrote:As the sun revolves around the Milky Way in a span of several hundred million years, will it likely pass through dust clouds or star forming regions and perhaps pick up mass that will defer its ultimate demise?

BDanielMayfield wrote:I haven't come to any conclusion, false or otherwise, and I realize that there is no way this could be a comet for several reasons.

Actually, what this "object" reminds me of most is a particle leaving a vapor trail in a cloud chamber, so I would respectfully ask, is it possible that there could be an orbiting or just passing object like a gas giant to red dwarf star mass inside the dense end that is leaving a trail-like wake in the ejecta it is passing through?

Chris Peterson wrote:

BDanielMayfield wrote:The strangest part of this outer halo is near the right edge. There's a piece that resembles the cone nebula or a comet, but its orientation is odd, like it's moving at nearly a right angle to the stellar wind. How might this be explained?

I'd say it's the pattern recognition system of your brain coming to a false conclusion. You're not looking at something moving perpendicular to the radial flow, you're looking at a shock front moving outwards with everything else. Because it's denser at one end than the other, your brain is screaming "comet". Of course, even comets are seldom actually moving in the direction our minds try to convince us they are.

neufer wrote:"wing tips"

BDanielMayfield wrote:The strangest part of this outer halo is near the right edge. There's a piece that resembles the cone nebula or a comet, but its orientation is odd, like it's moving at nearly a right angle to the stellar wind. How might this be explained?