Wikipedia:Reference desk/Archives/Science/2014 November 7

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November 7

Sun/Star

Hi everyone!

I would like some help with the following questions please:

1. Does a star’s solar mass increases/decreases as they evolve/age? Partly done: View Bulletin 6, 10, 11 below.
2. Is Blue staggers real or fake?  Done
3. After a protostar is formed, what comes next a blue star or an orange star? Y
4. Pre-main sequence or post-main sequence star, is it the protostar creation period or the protostar itself? Y
5. Main sequence star, can a blue star fall in the main sequence period… or main sequence is just called an yellow star from ZAMS?
6. Is the following, the true steps a star’s life follows? – protostar (baige colour), Blue star (after its fully formed), yellow star, orange star, red star, white star, neutron star (what colour?), black star (black hole).
7. What is a dead star?
8. What is a black hole? A ‘dead star’ or a ‘black hole’ just like a drain.
9. When was ‘Dark age’ and when was ‘reionaziation’ epoch? Did Reionaization occur during the dark ages?  Done

(Russell.mo (talk) 01:38, 7 November 2014 (UTC))

1. A star's mass decreases over time for several reasons 1) It is giving off a ton of energy in the form of light, and energy is mass. 2) It is also shedding mass directly in the form of solar wind. Early in their life they are gaining mass as they actually form as gravity pulls them together, but eventually they start to lose mass.
2. The only references I can find to blue staggers are the plant Dicentra cucullaria aka Dutchman's Breeches: [1]. They're quite real.
3. You can read more about the life cycle of stars at Stellar evolution.
4. See above
5. See above
6. See above
7. See above
8. See black hole
9. The dark ages can mean many things, I assume you mean the one from astrophysics. You can also read about the reionization epoch at the article titled Reionization.

I hope that helps some. --Jayron32 02:41, 7 November 2014 (UTC)

You deserve the masochist's barnstar for that one, Jayron. μηδείς (talk) 02:43, 7 November 2014 (UTC)

In this context, "Blue staggers" is probably luminous blue variable, and, yes, they do exist. Tevildo (talk) 02:47, 7 November 2014 (UTC)

Or possibly a Blue straggler star. CS Miller (talk) 12:26, 7 November 2014 (UTC)

I've read through point 3, 8, the things I mentioned were unclear that's why I asked... Can some help me understanding by explaining in simple terms please? -- (Russell.mo (talk) 18:45, 7 November 2014 (UTC))

If you could point out passages from the stellar evolution article which are unclear, perhaps we can help make them more clear. The article is fairly well written and quite accessible, but if there are words or statements in that article that you are struggling with, let us know, and we'll try to explain them a bit differently if we can. --Jayron32 21:41, 7 November 2014 (UTC)

Thanks Jayron32. I appreciate it. I have to come back to this topic at a later time I think I have muddled a few things up myself in my course work. In the meantime if you and others can help me out with the followings to understand it better, I will be grateful.

6)

In the H-R diagram it illustrates a blue star evolves into a white star, then to an orange star. In the articles it defines a white star appears after the red star phase. This is the time it degenerates the outer layers… When do you see/does a white star appear?

7 & 8)

It says it is a dead star, meaning it doesn’t have no fuel to burn, though it can accrete matter from nearby star/ISM/GMC. Can it spark up again? Note, I know that this is a hypothesis, no black hole exist yet...

In Star Trek, it shows that spock’s friend, from his world, fires a red liquid into their planet and destroys the planet, by creating a “black hole”. Spark also creates a black hole using the same liquid from the enemy ship and goes back to the past or something, by entering the black hole… I don’t get the “black hole”? is there two types of black holes? One a dead star and one that takes you into the past...?

10. What is the limit for a star to follow the Henyey track, “< 0.5” mass or “>”, to follow through the main sequence. One article says “< 0.5”, another “> 0.5”…

11. Can a star possess 1 or 2 solar mass during the main sequence stage, post main sequence stage, while it’s in a white dwarf or neutron dwarf or black dwarf stage?

12. What gets created first? A star or a planet? Is there a chance of a vice versa?

13. What will occur if two stars collide?

14. A star burns hydrogen into helium during its main sequence stage (in the core). What occurs in the shell? What kind of fusion takes place in the shell? When the supply of hydrogen is finished at the core, helium fusion takes place into the shell. What happens in the core?

14.1. How many layers of shell does a star have/create? According to calculation “four” if it is a massive star but at what solar mass? and what about the small solar mass star?

14.3. When it goes to the red giant phase (post main sequence) it burns helium into ________. What occurs in the shell? What kind of fusion takes place in the shell?

14.4. What kind of molecules can a star create/what kind of things can a star burn/fuse in the core and in its shell?

(Russell.mo (talk) 13:14, 8 November 2014 (UTC))

6) Stars don't evolve diagonally along the "main sequence" of the HR diagram (though it looks that way). As they age, stars move horizontally left-to-right in the diagram, roughly speaking, though even that has some variability. If you check out the diagram at File:Zams and tracks.png, you'll see that stars generally evolve from blue colors (hottest, youngest) towards the redder colors (coolest, oldest). Heavier stars start out bluer on the scale, but they all generally trend that way. The color of a star is governed by the principles of blackbody radiation, which connects the peak color of a hot object and its temperature. The specific way in which a star ages depends on what happens when its supply of hydrogen runs low, but they all generally expand in volume and thus cool off some, gradually becoming redder.

7 & 8) The existence of everything outside your own mind is an unproveable hypothesis, black holes are at least as proven as anything else. We have identified many hundreds of black holes. Anyone that tells you that we haven't found any black holes, or that they are "just a hypothesis" can be ignored as entirely not understanding anything about science and understanding. They're plainly wrong. Also, any question regarding "why" some bit of physics happens in a work of fiction has one answer "because the people who wrote the work of fiction wrote it that way." Fiction means "something people invented to entertain people" and physics that happens in fictional worlds is still "physics made up to entertain people". How black holes work in the fictional world of Star Trek is up to the whims of the writers, and has no necessary connection to real-world science.

10) The Henyey Track applies to any star of greater than half of a solar mass (from the mass of 1/2 of our own sun to greater).

11) Stars can be any mass at all; 2 solar masses is actually pretty small for a star. The largest stars are well over 100 times the mass of our own sun; on the main sequence the largest stars are the bluest and hottest.

12) The stars and planets generally form together in the Protoplanetary disk. As the protostar begins to accrete mass towards itself and as it starts to spin at the same time, the matter around the forming star flattens out into a disk. Planets form as eddies in the spinning disk form their only little balls of matter which also accrete material towards themselves. A star is just a bigger ball of matter than a planet is in this giant, swirling disc-like cloud; stars are balls of matter whose gravity is high enough to fuse hydrogen, but the entire process that creates stars (swirling discs of diffuse matter which slowly concentrate into dense balls) creates the planets that form around them. Many decades ago, before Exoplanets were discovered, it was thought that our own system, with a bunch of planets circling a star, may be rare. Now, the general belief is that nearly every star system should have a collection of these planets around them. Our ability to find them is only limited by the fact that they're fiendishly hard to find. But if you consider the basic premise of the cosmological principle, that our own perspective on the universe is not privileged or unique, the same process that formed our sun and planets is forming suns and planets all over the universe in the same way, billions and billions of times.

13) Read Stellar collision.

14 & 14.1) The article Stellar structure contains the basics of different types of stars; the "layers" of a star will vary with the kind of star you're dealing with.

14.3) Carbon. See Triple-alpha process.

14.4) The articles nucleosynthesis, Stellar nucleosynthesis, and Supernova nucleosynthesis will help you understand how various elements are formed in stars. As far as I know, the hot plasma of a star is far to hot for molecules to form in any meaningful sense. For a molecule of anything, you'd need to be cool enough to form stable, neutral particles, and stars aren't cool enough. --Jayron32 15:23, 8 November 2014 (UTC)

I've gathered the articles, I'll read through them. Thanks for the little summary along. Regards. -- (Russell.mo (talk) 16:18, 8 November 2014 (UTC))

---

I have few more questions I would like help on, could you kindly help me please, or direct someone who would be able to help.

1)

Dark Ages

Before decoupling occurred, most of the photons in the universe were interacting with electrons and protons in the photon–baryon fluid. The universe was opaque or "foggy" as a result. There was light but not light we can now observe through telescopes. The baryonic matter in the universe consisted of ionized plasma, and it only became neutral when it gained free electrons during "recombination", thereby releasing the photons creating the CMB. When the photons were released (or decoupled) the universe became transparent. At this point the only radiation emitted was the 21 cm spin line of neutral hydrogen. There is currently an observational effort underway to detect this faint radiation, as it is in principle an even more powerful tool than the cosmic microwave background for studying the early universe. The ‘Dark Ages’ are currently thought to have lasted between 150 million to 800 million years after the Big Bang.

Reionization, 150 million to 1 billion after the Big Bang

In Big Bang cosmology, ‘reionization’ is the process that reionized the matter in the universe after the "dark ages", and is the second of two major phase transitions of gas in the universe. As the majority of baryonic matter is in the form of hydrogen, reionization usually refers to the reionization of hydrogen gas. The primordial helium in the universe experienced the same phase changes, but at different points in the history of the universe, and is usually referred to as ‘helium reionization’.

They found the galaxy UDFj-39546284 to be at a time some 480 million years after the Big Bang or about halfway through the Cosmic Dark Ages at a distance of about 13.2 billion light-years.

I’m confused, with the highlighted bits. When did the reionization occur and when was the dark ages?

2)

The dark matter clump together under gravitational attraction due to the initial density perturbation spectrum caused by quantum fluctuations. This derives from Heisenberg's uncertainty principle which shows that there can be tiny temporary changes in the amount of energy in empty space. Particle/antiparticle pairs can form from this energy through Mass-energy equivalence, therefore enacting a gravitational pull, which will cause other nearby particles to move towards it, disturbing the even distribution and creating a centre of gravity. The gravity of these denser clumps of dark matter then caused nearby matter to follow suit, and start falling towards the centre. This resulted in a clouds of gas, predominantly Hydrogen to form, and within these clouds began to form the first stars. These clouds of gas and early stars, many times smaller than our galaxy, were the first protogalaxies.

I don’t understand this highlighted bit, hydrogen was there from before, right? During the “Dark ages”.

3)

View the link (https://en.wikipedia.org/wiki/Star#Classification) and explain please why this is the second time it defines a white star occurs twice during its evolution phase [Once after the blue star phase and the other after the red star phase]. I actually don't get it. The diagram you told me to look at earlier in the other discussion does not have a white star line during its evolution phase.

4)

A blue dwarf is a hypothesized class of very-low-mass stars that increase in temperature as they near the end of their main-sequence lifetime. – Can you tell me when a white dwarf appears, after the blue or red star? Does it depend on its mass, when it fails/falls/breaks apart?

This article Dwarf star displays names of some main sequence stars which should be in the post main sequences phase. I don’t understand why?

Can someone please check if the following step are correct?

1. Protostar formation

2. Pre-main sequence phase:

Blue star to Yellow star, (assuming that it passes through the white star phase or straight to yellow just like the way Jayron32 mentioned. Pre-main-sequence star says what Jayron32 says too. [Which one? please reassure me again]). Blue dwarf and Pre-main sequence star article mentions that it can go straight from blue to white depending on its mass.

3. Main sequence – (What kind of stars are they talking about in this article?):

3.1 Yellow Star/dwarf – Note: G-type main-sequence star article mentioned the word post main sequence to white dwarf, not to a red star/dwarf? the Star article mentions post main sequence to the red giant star.

3.2 Orange Star/dwarf

4. Post main sequence [unable to find the article; only mentioned in the aforementioned article]:

4.1 Red giant star (Star article say it’s a post main sequence star.

4.2 Red dwarf (Dwarf star and Red dwarf article say it’s a main sequence star when its intricacies are similar as red giant and red supergiant.

4.3 Blue dwarf (Dwarf star, blue dwarf article say it’s a main sequence star. This and the Blue stragglers article define the word hypothesis/hypothetical/theoretical. Should a blue dwarf (T tauri star) come after the protostar formation? which is real? Does it also come after the red giant phase? Note: Whether it is a theory or hypothesis, how can a red star/dwarf turn blue star/dwarf without accreting molecules? A cooking gas fire turn from blue to yellow to red, it doesn't go white colour. What is the reason it turns white in colour?

4.4 Red supergiants (Dwarf star and Red supergiant and article say it’s a main sequence star. Red dwarf article has some information similar as Red supergiant.

5. What sequence phase are the following [I didn’t find anything]:

5.1 White dwarf - apparently its a post main sequence phase/star defined in G-type main-sequence star article.

5.2 Neutron star

5.3 Black hole – I don’t understand how this occurs. I thought the clashes between the molecular clouds of galaxies will create a black hole. All I understand that it occurs when a massive star collapses. Can you go inside it? Is it like a worm hole? it seems like a black dwarf to me after re-reading both articles. According to analysis, black hole are called the massive stars and black dwarfs are called the less massive stars. The article also mentions that the Milky Way galaxy holds a black hole at the center of the galaxy. In the Milky Way article I didn't see any black hole star at the centre of the galaxy.

5.4 Black dwarf – this article states that no black dwarf exists yet… What’s the difference between Black hole and black dwarf.

5.5 Brown dwarf – Where do I put this?

(Russell.mo (talk) 16:00, 9 November 2014 (UTC))

• I'm not sure why you are so resistant to reading the article titled Stellar evolution. For one, it presents a more nuanced view of the life cycle of stars. Stars do not merely follow a neat, orderly pattern of colors. Depending on their size and specific composition they live different types of lives. It would be better for you to read the Stellar evolution article and come to understand a more complete, accurate, and nuanced view of the life of a star, rather than looking for some universal list of colors which doesn't really represent a good heuristic for understanding the processes involved. Just read the article and let go of the little timeline you're trying to develop. --Jayron32 02:46, 11 November 2014 (UTC)

Lol I'm just running out of time, that's all. I have read the article Stellar Evolution once before, its just re-reading when I don't have the time. Thank you for replying back Jayron32 -- (Russell.mo (talk) 11:45, 11 November 2014 (UTC))

Not done: On hold until

Prestressed concrete failure

Is it correct to say that the failure of a prestressed beam is explosive due to the stresses which have built up in the concrete? — Preceding unsigned comment added by 194.66.246.101 (talk) 19:06, 7 November 2014 (UTC)

This is just off the top of my head: As the 'tensional' stress is in the rebars, The failure is not down to the stress in building up in the concrete. High alumna cement (for example) when poorly mixed (too much water) may start to crumble and loose the 'compressive' strength required to hold the rebar stress in place- which is imposed during casting. The compressive stress within the concrete is already imposed in casting and curing, so should not (I think) build up over time. Off the top of my head again: I think that rebars lose about 5% of their strength per decade. Therefore, by my reckoning the stress on the concrete is ever diminishing not building up. Err.. does that make sense. It is not the build up of stress “in the concrete” but the reduction of the concrete’s ability to resist the tension stress imposed on it by the rubars.Also, cracks in the concrete can allow water and atmospheric oxygen to get down to the rubars. This makes them corrode. The corrosion not only weakens the rubars, it also causes them so expand volumetrically, which makes the concrete cocoon spall off. Which will further weaken the structure. Possible leading to an 'explosive' or rapid unscheduled disassembly of the building or structure (in other words - it collapses). This maybe the phenomena of which you maybe inquiring about. --Aspro (talk) 19:49, 7 November 2014 (UTC)

But let's say you apply a load to a prestressed beam, you increase the bending on it and hence I would have thought you have increased bending stress on the beam. And then that stress builds up eventually causing failure. — Preceding unsigned comment added by 194.66.246.16 (talk) 10:28, 11 November 2014 (UTC)

actually I suppose that bending stress is in the rebar and not the concrete. But could you argue that the opposing force of concrete which is trying to stay in compression is causing an increase in stress? — Preceding unsigned comment added by 194.66.246.16 (talk) 10:30, 11 November 2014 (UTC)

The deal is that concrete is very strong in compression - but incredibly weak in tension. When you apply weight to a beam, the top of the beam is compressed but the bottom is tensioned. So simple concrete beams snap rather easily - often under their own weight. So the idea is to apply artificial compression forces to the beam when there is no weight on it. Then when you do apply weight, the top part gets compressed both by the load, and by the artificial compression source...the bottom is compressed by the artificial compression MINUS the tension caused by the load. If you get the tension right, the bottom of the beam is still in compression - so it's still strong. Hence, the rebar (or cable system or whatever) that pre-stresses the concrete isn't being stressed by the load directly - but rather by the beam itself. When you load the beam, the top of it is increasing the tension in the rebar - but the bottom of it is reducing the tension - so the average doesn't change. If everything works out right, the rebar doesn't get any extra forces applied to it at all when a load is applied to the concrete. The concrete does all of the work.

When something fails (anything really), it's tough to say whether the result will be "explosive" or rather gentle. The failure modes are many - some will release the energy rapidly, and others more slowly. So it's hard to say what will happen without a lot more information about the application. SteveBaker (talk) 20:55, 11 November 2014 (UTC)

Organic chemistry question

Say, in an organic compound, we have a main chain of nine carbons (-nonane); on the sixth carbon there is a propyl side chain (normal position), while on the fifth carbon there is an isopropyl side chain; would the preferred IUPAC name be "5-isopropyl-6-propylnonane" or "5-s,6-dipropylnonane"? Thanks 74.15.5.210 (talk) 21:41, 7 November 2014 (UTC).

Neither. It would be 4-propyl-5-isopropylnonane. Always number from the end which gives you the lowest numbers for your side chain. --Jayron32 21:45, 7 November 2014 (UTC)

Actually, it might be 5-isopropyl-4-propylnonane. I think you put side chains in alphabetical order. But you would still always number from the short end. You'd never have a 5,6 nonane, because 4.5 nonane is a lower way to name the same molecule, whatever the side chains are. --Jayron32 21:47, 7 November 2014 (UTC)

5-isopropyl-4-propylnonane is correct according to the IUPAC rules for alkanes. Longest chain gets the root name, then side chains in alphabetical order, then lowest (total) numbering. Mihaister (talk) 23:00, 7 November 2014 (UTC)

Why don't new complex lifeforms keep on arising from microbes?

Complex life evolved just before the start of the Cambrian, presumably due to rising oxygen levels. What is not clear to me is why all complex life forms of today can be traced back to having evolved in that time period rather than microbes forming new complex life forms much later. Count Iblis (talk) 23:21, 7 November 2014 (UTC)

What do you mean by "complex life"? Sure, animalia complexity greatly increased at that point... but other kingdoms of multicellular life may have had different times for that. Certainly there were different times for complex life conquering different regions, i.e. in the sea vs. on land. That said, I think some of the issue may come down to competition. A "new" complex form or transitional form may not be well enough adapted to conditions/niches to outcompete against existing complex lifeforms. Think about it like this. Go to a forest, and imagine some plant that is currently nothing like a tall tree, but is currently alive (i.e. some part of the ecosystem). What evolutionary pressure does it have to go towards being a tree? Even if that pressure exists, how is it going to outcompete existing trees for the same resources along the way? It can't. Now, if a fire comes through and wipes out all of the trees, but somehow that one plant survives, it might evolve along a parallel path to a form similar to trees. But in the case of complex lifeforms, we're here, and not terribly absent from anywhere that we can thrive. --OuroborosCobra (talk) 23:40, 7 November 2014 (UTC)

The evolution of multicellular organisms was not a single event. There are multicelluluar plants, multicellular animals, multicellular fungi, etc., so the multicellularity has evolved independently multiple times. The Cambrian explosion gave rise to the majority of multicellular animal groups known today, apparently under the effect of predation pressure: growing larger is a good strategy to not be eaten. Still, pluricellular and multicellular organisms kept evolving after the Cambrian explosion. For example, Volvox - a colonial (pluricellular) organism - evolved from single-cell green algae ancestors in Triassic. --Dr Dima (talk) 00:06, 8 November 2014 (UTC) (It is interesting to note that Volvox seems to have evolved right around the Triassic–Jurassic extinction event, when the predation pressure was probably reduced). --Dr Dima (talk) 00:20, 8 November 2014 (UTC)

In Power, Sex, Suicide Nick Lane argues that the formation of the eukaryotic cell is an exceedingly unlikely event, and that without the eukaryotic structure, microbes will not evolve into effective multicellular organisms (other than colonies). Once this hurdle is passed, however, complex lifeforms can evolve readily. —Quondum 03:36, 8 November 2014 (UTC)

• Species largely evolve by adaptation and isolation. If there's a niche like an mammal-uninhabited island with plants with fruit, birds like the Dodo and the Kakapo can evolve from pigeons and parrots in strange new ways to fill the ecological niche elsewhere held by monkeys and rodents. But the macroscopic niches are mostly filled, and filled by better adapted animals. There's just no open higher position to be promoted to. Unles the earth is hit by a large asteroid Chicxulub or has a major tectonic or outgassing event Permian extinction, or some miraculous new chemical process that produces energy but poisons other life forms, like photosynthesis Oxygen crisis evolves, the grey goo are likely to be our next mighty new microbe rulers, whom I, for one, welcome. μηδείς (talk) 05:27, 8 November 2014 (UTC)

Thanks for all the answers. I guess that eliminating competition should also be possible in a laboratory. Although evolution takes a long time, in the lab you could engineer the right circumstances. So, could we create new animals de novo in the lab within a reasonable time frame using mainly natural selection and a minimal amount of engineering? Count Iblis (talk) 19:40, 8 November 2014 (UTC)

I've added a few more links to my above answer, in case they are useful. Count Iblis. Consider mammals. Marsupials and monotremes paralleled every form of land placental from the mole to the Rhino. But neither the egglaying platypus nor the pouched opossum could evolve into a truly flying or full aquatic form. It was only with the arrival of the placenta that bats and whales could swim and fly without losing their vulnerable young. You might also look at what Amazon.com did to Borders and what the internet is doing to print and broadcast media. The radically new business models have opened up new niches, but have driven a lot of other industries to or close to extinction. μηδείς (talk) 22:00, 8 November 2014 (UTC)

• I think a reason may be that slime molds are paraphyletic - so if a new multicellular life form arises, at least on land, you would probably call it a slime mold. I don't know if the taxonomy has been revised since last I looked; it certainly was too confused for me to say that none of them evolved after the Cambrian. There are many other "non-multicellular" life forms that certainly look otherwise - Volvox, Spirogyra, colonial choanoflagellates, etc. The definition of multicellular life can be fine-tuned to exclude many of these things, but the way our article uses it, it credits at least 46 separate origins. Wnt (talk) 15:17, 9 November 2014 (UTC)

I agree with the relevance of Wnt's comment, but pretty much and presumably all known phyla of animals date back to the Cambrian explosion. There's a difference between grade-lifestyle and clade-genetic relationship. For example, insects, pterosaurs, birds and bats have all accomplished the grade of flying animal, while whales, bats, elephants and shrews all belong to the placental clade. The slime molds are worse than paraphyletic, they are polyphyletic. They don't form a coherent group at all. This would be the same as for the groups we call worms and shellfish. There are many unrelated groups of animals well call worms, like flatworms, earthworms, and nematodes; or shellfish which are simply things like crabs and clams that are edible sea creatures that don't meet the Kosher definition of edible fish, which must have both fins and scales. μηδείς (talk) 22:19, 9 November 2014 (UTC)

The Cambrian explosion was indeed a big deal, but for all known animal phyla to date back to that point is essentially a tautology. Any "phylum" that arose more recently could be grouped with some sister group with similar characteristics from before they split, and joined into a single phylum from Cambrian times. And of course this only describes animals, whose multicellularity is rarely at issue. Wnt (talk) 17:57, 10 November 2014 (UTC)

I am not quite sure what you are trying to qualify, Wnt. It would help if you would point out some traditional phyla that don't date to about the Cambrian explosion, if you are implying there are many. Land plants and fungi seem to date to this period as well. I'll grant phylum is an artificial term, but even if we just look at the proliferation of the deepest clades they seem to date to that era. But I suspect we are probably in agreement, actually. μηδείς (talk) 18:27, 10 November 2014 (UTC)

Well, the point is that anything that arose more recently, however different the morphology may be, will still not rate as a phylum. Something like Lernaeodiscidae doesn't look like its relatives, but because it is more recent in origin, traces of its ancestry remain at a larval stage and by DNA homology. Wnt (talk) 00:47, 12 November 2014 (UTC)