Starship Asterisk*

http://apod.nasa.gov/apod/ap080727.html
http://antwrp.gsfc.nasa.gov/apod/ap020618.html
http://antwrp.gsfc.nasa.gov/apod/ap000416.html


http://antwrp.gsfc.nasa.gov/apod/image/ ... st_big.jpg

http://geology.about.com/library/bl/ima ... cracks.htm
http://www.depauw.edu/acad/geosciences/ ... cracks.htm
http://www.earthscienceworld.org/images ... =Mudcracks

http://upload.wikimedia.org/wikipedia/e ... y_logo.jpg

http://en.wikipedia.org/wiki/Crack_the_Sky

APOD wrote:The star primarily responsible for this interstellar sculpture can be found in the planetary nebula's center.

The penny, right?

You guys crack me up.

emc wrote:You guys crack me up.

As Thin Lizzy (the ol town) said: "This guys is cracking up, this guys has broken down". That's how i feel, when i read the description of todays APOD. An explosion which accordingto the APOD is cylindrically shaped, according to the Hubble description shaped as a 'donut', which seems to be a ring shaped pastry.

I'm puzzled. How can an explosion be ring shaped or cylindrically shaped? When a star blows, such explosion is supposed to be spherical. Space is isotropical, since the gravity field is isotropical, apart from some slightly flattened stars. A magnetic field can break this spherical symmetry. Usually explosions are matter controlled, matter dominates the effects of a magnetic field, however in solar spots and the accompanying prominences the magnetic field plays a major role. The discussion about the plasma bullets elsewhere on this site, is yet another example of magnetically controled 'explosions'.

So suppose the magnetic field dominates. At the poles of the exploding star matter is ejected radially. The magnetic field lines are radially directed, the plasma flies parallel to the field lines. At some height, the lines bend towards the stellar equator, and the direction of the plasma has angle to the field lines. As a result, due to the Lorentz force the plasma starts to spiral along the field lines, hampering the radial motion. Still suppose the magnetic field is sufficiently strong, the matter bends towards the stellar equator.

At the stellar equator matter is ejected radially, thats perpendicular to the magnetic field lines. Here the Lorentz force controls the movement of the matter completely. At the stellar equator matter from the equator itself and matter from the north and south poles of the sun is brought together. Since the matter is accumulated, it might be able to dominate the magnetic field. The only thing this line of thought produces is a slight preference for the matter to be diverted from the poles. Whether that is sufficient to explain quantitatively the odd shape in todays APOD, that is up to the professional astronomers. I'm JAA.

E.g. Art Neuendorfer, do you have any ideas or objections on this line of thought?

Here's a flash video worth a look.

It describes the Retina Nebula (IC 4406 - this APOD) as undergoing the same ring progression as some other planetary nebulae. From youngest to oldest in this progression, it names the following planetary nebulae:

Dumbbell Nebula (M27 - APOD 2005 June 03)
Retina Nebula (IC 4406 - this APOD)
Ring Nebula (M57 - APOD 2004 July 04)
Eskimo Nebula (NGC 2392 - APOD 2006 July 09)
Helix Nebula (NGC 7293 - APOD 2004 December 29)

Sorry, I have no theory of the doughnut.

Of course, these planetary nebulae are viewed from Earth at different angles - we look at the side of the ring of IC 4406 (this APOD), but almost straight into the hole of the Ring Nebula.

Apodman's flash video indicates that 'cracked' core part
of IC 4406 is a fat dough-nut whose axis parallels
the axis of the fuzzier non-core cylindrical part:

Almost all rotating stars have a dipole magnetic field (albeit a cyclically alternating one like the sun's 11 year cycle).

The ionized particles of the supernova will balloon out the dipole magnetic field into a large concentrated thin toroidal shell which partially traps the ionized particles themselves.

M2-9: Wings of a Butterfly Nebula (APOD 2004 February 01)

The Planetary Nebula Show (APOD 2001 October 03)

NGC 7009: The Saturn Nebula (APOD 1997 December 30)

NGC 6164: A Bipolar Emission Nebula (APOD 2006 June 06)

The Hubble 5 Planetary Nebula (APOD 1998 January 19)

http://antwrp.gsfc.nasa.gov/apod/ap080727.html

a doughnut viewed from the side is also square 9 and when you add hidden lines to describe structure hidden from view, you might get this APOD.

There's another topic already open for this APOD:

IC 4406 mudcracks (APOD 27 Jul 2008)

Some of the posts may approach the subject in an oblique way, but the subject is there.

Hello All,

Just wondering if the shape of this nebula:

http://antwrp.gsfc.nasa.gov/apod/ap080727.html

could occur, as outlandish as this sounds, by having the majority, if not all, of the matter ejected at the equator line. Then having the poles collapse or be gravitationally pulled inward to follow the path of the initial outward explosion. The magnetic lines could then flatten and create vector fields as the poles approached and repelled each other sending matter into a flatter plane. This may be initiated, as the spin rate increases with an increase in density perhaps creating an equatorial bulge. I am unaware of the time frame such a senario would require if this were the case.

If this were so, I don't think that the opposite, with matter being ejected at the poles followed by an equatorial collapse, would result in the same thing unless the pole jets caused a pole-to-pole spin.

Either Professor Nemiroff or Bonnell wrote:Are stars better appreciated for their art after they die? Actually, stars usually create their most artistic displays as they die.
(From:M2-9: Wings of a Butterfly Nebula)

Of course, this is not usually true of people… at least the second part anyway.

However, on a more serious note… I expect many folks share the “this is art” sentiment regarding these beautiful “nearly still” life APOD images. The subject object is one of many good examples here of science merging with art – at least, for me anyway. The composited false colors are cool and serve a two-fold purpose in providing an indication of the primary ingredients and also paint an aesthetic composition… something for scientists and others too.

A third dimension I see (...as I ramble on) from this and other APOD and Asterisk endeavors is the bringing together of strangers from very different backgrounds in a friendly, creative and informative way through cyberspace… kind of an open-ended internet social gathering for fun and learning challenges.

astrolabe wrote: as outlandish as this sounds, by having the majority, if not all, of the matter ejected at the equator line. Then having the poles collapse or be gravitationally pulled inward to follow the path of the initial outward explosion.

In 2003 Vincent Icke of the Leiden University published an article on the hydrodynamics of planetary nubulae (Europhysics news jan/feb 2003, page 12-15). He first used an analytical solution of the Kompaneyets equation. Then, Mellema and coworkers solved the numerical part of the analytical solution of the Kompaneyets equation. Icke and Van Winckel made some quick time movies available of the numerical solutions for the expansion of the red rectangle nebula.

The shape of the nebula is non spherical due to the interaction of two winds: a slow dense outflow deposited during the time immediately after the red giant phase and a very fast, tenuous wind driven by radiation from the dying white dwarf.

Potentially the same can have happened for the Seemingly square nebula.

elena wrote:Hello henk, your link "quick time movies" doesn't work for me.Can you fix it please?

The link, http://www.strw.leidenuniv.nl/~icke/html/VincentRR.html works fine. But if you were expecting it to be a movie, it's not. Rather, it is a site where the movies can be found.

Wow .. what a great bunch of photos. Thanks to the posters.