Starship Asterisk*

TheOtherBruce wrote: ↑Fri Aug 02, 2019 1:23 am That's an interesting snippet upthread about this being an asymmetric supernova. That's something else new I've learned; I thought by definition a supernova reaction has to light up in the middle of the star's core, so where is the asymmetry coming from?

Unless... could the progenitor have been part of a binary (or more) system? That's the only situation I know of that can send a supernova remnant going thataway at a high rate of knots.

MarkBour wrote: ↑Thu Aug 01, 2019 8:16 pm

BDanielMayfield wrote: ↑Thu Aug 01, 2019 1:42 pm Is the type of supernova which produced this object known or suspected? I ask because the APOD's explanation talks of the production of elements heavier than Fe (no. 26) but then says that the remains are "exceptionally enriched" in O, Ne and Mg, elements 8, 10 and 12 respectively. Seems like this SN might have had a particularly low yield of heavy elements, perhaps?

Bruce

Bruce, sometimes the APOD text gets changed part way through the discussion. But by my reading of the text currently, I don't think there was meant to be any implication that this supernova (nor its progenitor) produced any elements heavier than Fe. There are 2 sentences that contain "heavier elements", but I think they just meant "heavier than helium".

Super-AGB stars

Stars close to the upper mass limit to still qualify as AGB stars show some peculiar properties and have been dubbed super-AGB stars. They have masses above 7 M☉ and up to 9 or 10 M☉ (or more[20]). They represent a transition to the more massive supergiant stars that undergo full fusion of elements heavier than helium. During the triple-alpha process, some elements heavier than carbon are also produced: mostly oxygen, but also some magnesium, neon, and even heavier elements. Super-AGB stars develop partially degenerate carbon–oxygen cores that are large enough to ignite carbon in a flash analogous to the earlier helium flash. The second dredge-up is very strong in this mass range and that keeps the core size below the level required for burning of neon as occurs in higher-mass supergiants. The size of the thermal pulses and third dredge-ups are reduced compared to lower-mass stars, while the frequency of the thermal pulses increases dramatically. Some super-AGB stars may explode as an electron capture supernova, but most will end as an oxygen–neon white dwarf.[21] Since these stars are much more common than higher-mass supergiants, they could form a high proportion of observed supernovae. Detecting examples of these supernovae would provide valuable confirmation of models that are highly dependent on assumptions.

BDanielMayfield wrote: ↑Thu Aug 01, 2019 1:42 pm Is the type of supernova which produced this object known or suspected? I ask because the APOD's explanation talks of the production of elements heavier than Fe (no. 26) but then says that the remains are "exceptionally enriched" in O, Ne and Mg, elements 8, 10 and 12 respectively. Seems like this SN might have had a particularly low yield of heavy elements, perhaps?

Bruce

BDanielMayfield wrote: ↑Thu Aug 01, 2019 4:17 pm
Interesting, innocuous origin for the word 'aftermath'. It went from describing a fine productive field's second harvest to describing scenes of horrific destruction.

I wonder how many people's fear of math stems from seeing and hearing news accounts of death and devastation called "the aftermath". Oh the horror! Look what math causes! Run for your lives kiddies, math is about to happen.

neufer wrote: ↑Thu Aug 01, 2019 2:25 pm

https://www.etymonline.com/search?q=aftermath wrote:
aftermath (n.) 1520s, originally a second crop of grass grown on the same land after the first had been harvested, from after + -math, from Old English mæð "a mowing, cutting of grass." Also known as aftercrop (1560s), aftergrass (1680s), lattermath, fog (n.2). Figurative sense is by 1650s. Compare French regain "aftermath," from re- + Old French gain, gaain "grass which grows in mown meadows," from Frankish or some other Germanic source similar to Old High German weida "grass, pasture.">>
................................................

• When the summer fields are mown,
  When the birds are fledged and flown,
  And the dry leaves strew the path;
  With the falling of the snow,
  With the cawing of the crow,
  Once again the fields we mow
  And gather in the aftermath.
  
  [Longfellow, from "Aftermath"]

Ann wrote: ↑Thu Aug 01, 2019 1:56 pm

BDanielMayfield wrote: ↑Thu Aug 01, 2019 1:42 pm Is the type of supernova which produced this object known or suspected? I ask because the APOD's explanation talks of the production of elements heavier than Fe (no. 26) but then says that the remains are "exceptionally enriched" in O, Ne and Mg, elements 8, 10 and 12 respectively. Seems like this SN might have had a particularly low yield of heavy elements, perhaps?

Bruce

I seem to remember reading somewhere that the progenitor of an oxygen-rich supernova remnant was probably a massive star, and the supernova was a core-collapse one.

But hey, it could be my scatterbrained mind playing tricks on me.

Ann

Supernova remnants are the debris from exploded stars. G292.0+1.8 is a rare type of supernova remnant observed to contain large amounts of oxygen. Because they are one of the primary sources of the heavy elements (that is, everything other than hydrogen and helium) necessary to form planets and people, these oxygen-rich supernova remnants are important to study. The X-ray image of G292+1.8 from Chandra shows a rapidly expanding, intricately structured field left behind by the shattered star. The image is colored red, green, teal and purple in X-rays ranging from the lowest to highest energy levels.

Recently the first detection was made of iron debris from the exploded star. Authors constructed a map of this debris, along with that of silicon and sulphur, to understand more about the explosion. They found that these three elements are mainly located in the upper right of the remnant. This is in the opposite direction from the neutron star that was formed in the explosion, and was then kicked towards the lower left of the remnant. This suggests that the origin of this kick is gravitational and fluid forces from an asymmetric explosion. If more than half of the star’s debris is ejected in one direction, then the neutron star is kicked in the other direction so that momentum is conserved. This finding argues against the idea that the copious amounts of neutrinos formed in the supernova explosion were emitted in a lop-sided direction, imparting a kick to the neutron star.

https://www.etymonline.com/search?q=aftermath wrote:
aftermath (n.) 1520s, originally a second crop of grass grown on the same land after the first had been harvested, from after + -math, from Old English mæð "a mowing, cutting of grass." Also known as aftercrop (1560s), aftergrass (1680s), lattermath, fog (n.2). Figurative sense is by 1650s. Compare French regain "aftermath," from re- + Old French gain, gaain "grass which grows in mown meadows," from Frankish or some other Germanic source similar to Old High German weida "grass, pasture.">>
................................................

• When the summer fields are mown,
  When the birds are fledged and flown,
  And the dry leaves strew the path;
  With the falling of the snow,
  With the cawing of the crow,
  Once again the fields we mow
  And gather in the aftermath.
  
  [Longfellow, from "Aftermath"]

https://www.quora.com/What-rpm-do-a-typical-gasoline-and-electric-push-lawnmower-spin wrote:
<<Blades on riding mower typically spin between 2700 and 3200 rpm [ i.e., a period of 22 to 19 milliseconds.]>>>>

https://en.wikipedia.org/wiki/Pulsar wrote:
<<The shortest period pulsar, PSR J1748-2446ad, with a period of ~1.4 milliseconds.

The longest period pulsar, at 118.2 seconds, as well as the only known example of a white dwarf pulsar, AR Scorpii.>>

BDanielMayfield wrote: ↑Thu Aug 01, 2019 1:42 pm Is the type of supernova which produced this object known or suspected? I ask because the APOD's explanation talks of the production of elements heavier than Fe (no. 26) but then says that the remains are "exceptionally enriched" in O, Ne and Mg, elements 8, 10 and 12 respectively. Seems like this SN might have had a particularly low yield of heavy elements, perhaps?

Bruce

orin stepanek wrote: ↑Thu Aug 01, 2019 12:23 pm G292 Chandra; The element factory!