This spun up the larger star, and the centripetal force flung off material in a huge disk well over a light years across.

NO NO NO no no no no…

The centripetal force is by definition an INWARDLY DIRECTED force. It CANNOT throw things outwards, this would violate Newton’s second law*. The centripetal force acts AGAINST the outward motion.

Once again, since this point seems to be confusing: CENTRIPETAL FORCE IS AN INWARDLY DIRECTED FORCE.

If we look at this in an inertial frame then it is inertia that is responsible for the material being flung outwards. Or we go to a rotating frame in which case you have to incorporate centrifugal force in the equations of motion, and it is the centrifugal force that throws the material outwards.

(And yes we all get taught that centrifugal force is a fiction, but it is perfectly real in a rotating reference frame. Similarly general relativity demonstrates that gravity is also a fictitious force caused by the geometry of space-time but strangely enough no-one gets hang-ups about gravity being “not real”…)

*Unless you are dealing with negative inertial mass that is, but this situation does not appear to be realised in the real world…

Every action has an equal and opposite reaction. Many physicists maintain that there is no such thing as the popularly-known “centrifugal force”, so it could be that the BA was simply implying that the reactive force to the centripetal acceleration was responsible.

Action-reaction pairs don’t act on the same object, so it’s not correct to speak of reactive the force of the centripetal force, which is already acting on the gas surrounding the star, acting on the gas as well. If anything, it should act on the star.

Either that or he meant centrifugal force.

I thought of that illusory force too.

@23. Nigel Depledge : I’m guessing that ‘Ni’ is a typo for Nitrogen (N) rather than indicating gaseous clouds of nickel, surely?

Either that or he meant centrifugal force.

BTW, as someone who uses a centrifuge on a routine basis, I think there probably is such a thing as centrifugal force, even if it is fundamentally an illusion.

Usually H and Ni are red, so they colored them differently to distinguish them.

Huh? I don’t remember you mentioning Nickel (Ni) in the article . . . ?

“This spun up the larger star, and the centripetal force flung off material in a huge disk well over a light years across.”

If the centripetal force is “centre-seeking”, then how could it have flung things out?

Given in our local stellar region only a handful of stars seem likely to host goldilocks planets (Alpha Centauri – 4.3 ly, Tau Ceti – 10 or so, Epsilon Eridani – 10 or so) I’m guessing the odds of such PN destroying habitable worlds are fairly low.

To be precise Tau Ceti – an old metal poor G8 yellow dwarf star :

http://stars.astro.illinois.edu/sow/taucet.html

is located 11.9 light years distant with Epsilon Eridani – a very young K2 orange dwarf star – is located a fraction nearer at 10.5 light-years distant. (Link for that from the Tau Ceti link via Kaler.)

There are only 3 stars known within 5 light years radius of our Sun – Proxima Centauri and Alpha Centauri A & B whilst going out to ten lightyeras adds only – Sirius A & B, Barnard’s Star, Wolf 359, Lalande 21185, the UV Ceti “Luyten’s Flare star” red dwarf binary and Ross 154. Almost all those are red dwarfs which may be extremely unlikely to host habitable planets – although OTOH :

http://kencroswell.com/reddwarflife.html

may have us rethinking that.

So in a nutshell stars are pretty far apart and as this nebula extends “only” 8 trillion miles when a single lightyear equals 6 trillion miles. (Source : Wikipedia – lightyear page) it is unlikely it envelops more than its system of origin.

Exoplanetary discoveries have been both positive when it comes to habitable “goldilocks” planets suggesting there are indeed many worlds out there – and also negative in showing that earthlike exoplanets and solar system anaologes are rare. We’ve been surprised by many exoplanetary systems that are hostile for habitable goldilocks planets due to Hot Jupiters (which may destroy earth-like planets as they migrate inwards) or eccentric orbiters (which again could disrupt any earth-like planets and force it too orbit to elliptically for likely life) or just the wrong planets in the wrong places such as here :

http://blogs.discovermagazine.com/badastronomy/2007/08/03/new-planet-with-earthlike-orbit-nah/

where an exoplanet, HD 17092, touted by some as having an “earthlike” 360 day orbit is in fact a superjovian orbiting a red giant star.

(The more massive star which has 2.3 solar masses would have been probably too hot, too bright and too short-lived to host living planets even when it was on the main-sequence as a Sirian type star.)

So, as noted we can’t really assess the odds of goldilocks planets being destroyed by this planetary nebula forming because we don’t really know yet how rare or common they are. We don’t know if this star that’s dying this necklace nebula case had any goldilocks type exoplanets itself – although that’s something that working out its mass and former spectral class could aid in – but it seems unlikely to me that it would kill off too many other worlds based on star populations and densities -and the fact, again, that space is big!