Ultimate space simulation software

 
Mr. Abner
Explorer
Explorer
Posts: 233
Joined: 08 Jun 2017
Location: Mississauga

Science and Astronomy Questions

17 Mar 2018 23:44

Watsisname deserves some kind of award for the best-written and most informative replies.

Always love your posts.
 
User avatar
Watsisname
Science Officer
Science Officer
Posts: 1336
Joined: 06 Sep 2016
Location: Bellingham, WA

Science and Astronomy Questions

18 Mar 2018 02:10

Thanks!  But to me, seeing someone learn something new and finding it interesting is the only reward that matters. :)

FastFourierTransform may not answer questions as frequently, but his have consistently very high quality and are also a joy to read.
 
User avatar
Mosfet
World Builder
World Builder
Posts: 1063
Joined: 24 Oct 2016
Location: Italy
Contact:

Science and Astronomy Questions

18 Mar 2018 04:11

Starlight Glimmer wrote:
Source of the post Another question. What types of stars are Polaris C and D? Are they bound to the Polaris system?

According this interesting article regarding observations of Polaris system with Chandra X-ray telescope published in 2010,
C and D were extremely difficult to discern at the time, but they seem to have a proper motion and other characteristics not compatible with stars orbiting within the system. They prudently assume a class M for both stars.
"Time is illusion. Lunchtime doubly so". Douglas N. Adams
My mods | My specs: Asus x555ub - cpu i5-6200u, ram 4gb, gpu nvidia geforce 940m 2gb vram | IRC freenode.net canale ##SpaceEngineITA
 
User avatar
Starlight Glimmer
Explorer
Explorer
Posts: 284
Joined: 02 Nov 2016
Location: Somewhere

Science and Astronomy Questions

18 Mar 2018 06:57

Mosfet wrote:
Starlight Glimmer wrote:
Source of the post Another question. What types of stars are Polaris C and D? Are they bound to the Polaris system?

According this interesting article regarding observations of Polaris system with Chandra X-ray telescope published in 2010,
C and D were extremely difficult to discern at the time, but they seem to have a proper motion and other characteristics not compatible with stars orbiting within the system. They prudently assume a class M for both stars.

Wow. This is very interesting, I love this article. Even if they aren't bound to the system, imagine what it'd be like to be on a planet, perhaps a habitable world around one of those. How bright Polaris would be in the sky...
 
User avatar
FastFourierTransform
Explorer
Explorer
Posts: 228
Joined: 17 Nov 2016

Science and Astronomy Questions

18 Mar 2018 15:16

Watsisname wrote:
Source of the post FastFourierTransform may not answer questions as frequently, but his have consistently very high quality and are also a joy to read.

What an honor! Greater still when said by a person that is so admirable to me.
 
User avatar
Starlight Glimmer
Explorer
Explorer
Posts: 284
Joined: 02 Nov 2016
Location: Somewhere

Science and Astronomy Questions

01 Apr 2018 19:41

Is it possible for stable Neutron Stars or White Dwarfs to have habitable planets?
 
User avatar
FastFourierTransform
Explorer
Explorer
Posts: 228
Joined: 17 Nov 2016

Science and Astronomy Questions

02 Apr 2018 14:43

Starlight Glimmer wrote:
Source of the post Is it possible for stable Neutron Stars or White Dwarfs to have habitable planets?

Fascinating topic!
Your answer has been adressed by researchers at least in these cases I have found.
Habitability in White Dwarf systems: https://arxiv.org/pdf/1207.6210.pdf
Habitability in Neutron Star systems: https://arxiv.org/pdf/1705.07688.pdf


White Dwarfs
Every sufficiently hot object has an habitable zone (in terms of temperature strictly). White dwarfs reach hundreds of thousands of Kelvins at their surfaces, so they are adequate to harbour a circumstellar habitable zone (where water could be found in liquid state).

When an object has a high temperature with respect to its surroundings it loses heat to the environment (very rapidly at the beginning and slower when there is less energy left). Cool white dwarfs (cool means with temperatures similar to that of our Sun) are loosing heat slowly (and because there is a phase transition under 6000K where the star literally crystallizes the heat loss is even slower). That means that the habitable zone is going to change position in the time span of, maybe, billions of years. Any planet located there has plenty of time until it freezes and gets uninhabitable due to the slow drifting of the habitable zone to the insides of the system as the white dwarf slowly radiates the heat.

White dwarfs are also very constant in terms of luminosity. Their variability tends to be even smaller than our Sun's, so the climate would be stable for eons and any catastrophic flaring event can be discarded.

It's also true that 10% of white dwarfs have huge magnetic fields that could make the planet unsuitable for life (radiation belts and other complex issues), but still 90% are... let's say... OK.

So far so good. Now comes the tricky thing. White dwarfs as an evolutionary stage of a late type star, are preceded by a red giant phase, in which the inner planets are generally engulfed by the expanding star. Far away planets could survive this stage but the inner ones would probably fall apart while spiraling inwards inside the extremely tenuous outer layers of the red giant. Thus, we wouldn't expect planets close to the white dwarf, the only survivors should be the outer ones. And here comes the problem,the habitable zone of a cool white dwarf with temperatures in the range of 4000K and 6000K (solar-like temperatures) is just 0.01 AU away from the star. A hotter white dwarf would push the habitable zone farther away, but remember, we need a cool white dwarf to sustain habitability for large periods of time (life needs time to appear and time to evolve and with little time the probability of finding life there diminishes). With a cool white dwarf a planet in the habitable zone would retain Earth-like temperatures for 8 billion years!. Therefore we need our planet at the 2,5% of Mercury's distance to our Sun. But how can we archive this if the inner planets were destroyed in the red giant phase of the star?

Well we have some possible scenarios for that. Maybe planetary migration (for example due to pure friction of the planet as it moves through stellar wind or the interplanetary residuals of the red giant phase) takes some outer planets sufficiently close to make the deal. But this is improbable since the process of planetary migration would have to be precisely tuned as to stop the inspiraling planet just face-to-face with the stellar corpse. A jupiter-like planet orbiting inside the red giant (this can actually happen) could survive the entire phase while loosing a lot of its atmospheric content until, finally, a small rocky body remains in a close orbit around the residual white dwarf. This is what is thought to happened with Kepler-70b and Kepler-70c, both small rocky planets that have survived the red giant stage of their host star (their star is not yet a white dwarf but this is just a matter of time). We don't know of any exoplanets around white dwarfs yet (except perhaps for thesecircumbinary planets around a red dwarf - white dwarf binary system) but, as It turns out, having planets close to them could be quite common in fact as we have detected the chemical pollution of a terrestrial planet that recently was cannibalized by one.

So, yeah habitability around white dwarfs sounds promising. There are even good news in terms of ultraviolet radiation as the dose in these conditions would be inferior to that needed for DNA disruption, again as explained in this paper. Photosynthesis would be particularly benefited by the white dwarf's electromagnetic radiation. We are not accounting for problems like tidal locking (a probable situation at such distances) and the maybe poor chemical diversity of the planet (that would make nutrients and biochemical reactions much more improbable) as the red giant could have sublimated and dissociated many interesting compounds (or even ripped apart the entire atmosphere).

Detectability is in our current capabilities. The constancy of white dwarf's luminosity allows for any planetary transit to be easily confirmed. White dwarfs have small radii and so the transit would be quite abrupt while the planet eclipses a huge part of the stellar disk. The fact that we should search for a planet so close to its star makes the probability of seen the particular alignment needed for a transit even greater (transits are more frequent for inner planets because the orbital period is small and also because a wide range of orbital inclinations can yield those transits). Campaigns are being undertaken to search for them. And there is also the fact that polarization of light from the atmospheres of these white dwarf exoplanet's would be very easy to detect in relative terms.

Another interesting question would be if there can be life on white dwarfs themselves. We can't forget that white dwarfs could eventually be so cold as to become habitable carbonaceous planets. Would life evolve on the surface of a diamond planet (an extinct white dwarf) or the chemical environment would be inherently sterile and devoid of water?






Neutron stars
Planets around Neutron stars are known. In fact the first exoplanets discovered where around a neutron star (the pulsar PSR B1257+12). At the moment there are 4 pulsar planets confirmed

Neutron stars environment is extreme and harsh; Energetic flares, high X-ray flux, large magnetic fields and in the case of pulsars you even have a particle accelerator beam of dead. But these guys proposed a possible scenario were a Super-Earth with a dense atmosphere could retain it against the pulsar winds, gamma and X-ray flux for even billions of years and at the same time protect a possible biosphere below the thick fog.

If the planet is far away radiation could be less damaging. And there, where the thermal radiation of their neutron stars is low (thus the corresponding heating is less important) the X-ray heating of the atmosphere takes the lead and can be sufficient to create life-sustaining conditions on the distant planet. In this way the habitable zone has to be redefined for these exotic systems as the place where heat transferred by X-rays reacting with the atmosphere can be sufficient to allow for liquid water.

I want to quote two particularly inspiring notes from them:

Imagine what would be life on such planets: a huge pressure on the surface (due to the large atmospheric mass) able to crush anything we are familiar with. And completely dark. A very thick, black, warm fog. Indeed since gamma and X-rays cannot penetrate the whole atmosphere and reach the surface, neither will ultraviolet, optical or infrared light. It must vaguely look (and feel) like the deepest regions of the sea here on Earth with the difference that you have a whole planet at your disposal.

and

What would it be for an intelligent organism to communicate in this immensely thick fog. And if they would manage to make it outside their enormous atmosphere what would they see? A neutron star spinning hundreds of times per second and emitting beacons of radiation. They would learn with little effort things which are incredibly complex for us. They would witness the effects of general relativity in front of their eyes. Neutron stars do indeed bend space and time in a way that is second only to black holes. They could learn about ultra-dense matter and the behavior of the strong force if they could measure the mass and radius of their neutron star. They would witness the effects of strong magnetic fields and complex electromagnetism by looking at the pulsar. And perhaps they would then look at the other stars, the “normal” stars, like the Sun, and wonder whether life would be possible around those large distant objects, whether such poor emitters of X-ray radiation could sustain life. Whether it would be even conceivable to have life around such pale, cold, weak stars

As before another interesting question would be if there can be life on neutron stars themselves. According to this source, Martin Rees once said that neutron stars could hypothetically harbor "hyper-dense microscopic organisms controlled by nuclear forces with a metabolism faster than ordinary chemical-based life". An idea explored in the science-fiction novel "Dragon's egg", where a microscopic civilization rises in a matter of months on the surface of a neutron star and overcomes natural catastrophes such as starquakes and magnetic field anomalies just to start an exponential technological growth that surpasses that of the human visitors that study the phenomena.

________________________________________________

And as always, sorry for my English. I just writted this in the metro and had no time to be as vigilant as I should with grammar.

EDIT: I edited some parts (my spelling was terrible) and added some links to interesting readings. Thanks for the feedback also :D
 
User avatar
Gnargenox
World Builder
World Builder
Posts: 604
Joined: 11 Dec 2016
Location: 179° 56′ 39.4″ +0° 2′ 46.2″ @ 7,940 ± 420 pc

Science and Astronomy Questions

02 Apr 2018 21:25

Textbook quality sir ^
CPU: AMD FX-8350 8 core processor 4GHz / GPU: GeForce GT 730 @ 1920x1080, 60Hz with 1GB adapter RAM / RAM: Patriot Signature 4GB 1600MHz 240-Pin DDR3 (only 2GB work, don't buy it) / Motherboard: MSI 970 Gaming MS-7693
 
User avatar
Watsisname
Science Officer
Science Officer
Posts: 1336
Joined: 06 Sep 2016
Location: Bellingham, WA

Science and Astronomy Questions

03 Apr 2018 02:26

Great stuff, FFT.  I really enjoyed the excerpts, especially the second one.  Life in a neutron star system would be very alien indeed, and it's interesting to think of their development of science.
 
User avatar
Starlight Glimmer
Explorer
Explorer
Posts: 284
Joined: 02 Nov 2016
Location: Somewhere

Science and Astronomy Questions

03 Apr 2018 03:18

Now THAT is very interesting. A very good read, Sir. This will help me in developing situations similar to the ones. I cannot thank you enough for that read.
 
User avatar
PlutonianEmpire
Pioneer
Pioneer
Posts: 410
Joined: 02 Nov 2016
Location: MinneSNOWta
Contact:

Science and Astronomy Questions

03 Apr 2018 20:07

Wow, that is indeed fantastic writing!


I do have some new questions of my own. I was reading some tin foil hat stuff to laugh at, and I ran across one article claiming that they know about aliens who breathe C02 and supposedly stop aging upon maturity, and that O2 causes aging.

Lets take this apart.

My first question, what would it take for organic lifeforms to evolve and thrive under an atmosphere similar to Earth, with the exception that O2 and C02 have switched places (0.21 atm of CO2, 400 ppm of O2)?

Second question, we know O2 is an oxidant. What's the likelihood that it causes aging? How do we know if it does or if it does not?

Final question, if we were to find that O2 were somehow to blame for aging, how would humans need to evolve to breathe another substance that somehow keeps us young forever? How would we know if we'd be able to adapt to a new element to breathe in the first place?

Bonus question, if we taught ourselves to breathe CO2, wouldn't that open up every lifeterra ever in SE to us? :D :lol:
Specs: Dell Inspiron 5547 (Laptop); 8 gigabytes of RAM; Processor: Intel® Core™ i5-4210U CPU @ 1.70GHz (4 CPUs), ~2.4GHz; Operating System: Windows 7 Home Premium 64-bit; Graphics: Intel® HD Graphics 4400 (That's all there is :( )
 
User avatar
midtskogen
World Builder
World Builder
Posts: 649
Joined: 11 Dec 2016
Location: Oslo, Norway
Contact:

Science and Astronomy Questions

04 Apr 2018 00:17

I'd rather ask, would evolution at all work if there were no aging?

As for breathing CO2, we breathe to be able to fuel chemical reactions that give us energy, so to breathe CO2 there must be something that chemically reacts with CO2 releasing energy, so our diet would have to change radically from carbon based food to something completely else (and likely extremely toxic to ordinary humans).
NIL DIFFICILE VOLENTI
 
User avatar
PlutonianEmpire
Pioneer
Pioneer
Posts: 410
Joined: 02 Nov 2016
Location: MinneSNOWta
Contact:

Science and Astronomy Questions

04 Apr 2018 11:24

midtskogen wrote:
I'd rather ask, would evolution at all work if there were no aging?

As for breathing CO2, we breathe to be able to fuel chemical reactions that give us energy, so to breathe CO2 there must be something that chemically reacts with CO2 releasing energy, so our diet would have to change radically from carbon based food to something completely else (and likely extremely toxic to ordinary humans).

Oh wow. Ja that makes sense then. Thanks :)
Specs: Dell Inspiron 5547 (Laptop); 8 gigabytes of RAM; Processor: Intel® Core™ i5-4210U CPU @ 1.70GHz (4 CPUs), ~2.4GHz; Operating System: Windows 7 Home Premium 64-bit; Graphics: Intel® HD Graphics 4400 (That's all there is :( )
 
User avatar
Starlight Glimmer
Explorer
Explorer
Posts: 284
Joined: 02 Nov 2016
Location: Somewhere

Science and Astronomy Questions

07 Apr 2018 07:02

This question is inspired from a dream I had.

Are hotter brighter suns able to support life as we know it? F stars? A type stars? Even brighter ones like B and O, or subgiants?
 
User avatar
FastFourierTransform
Explorer
Explorer
Posts: 228
Joined: 17 Nov 2016

Science and Astronomy Questions

08 Apr 2018 14:55

Starlight Glimmer wrote:
Source of the post Are hotter brighter suns able to support life as we know it? F stars? A type stars? Even brighter ones like B and O, or subgiants?

Well, in the last post, with White dwarfs and Neutron stars I had a fairly optimistic approach but just because we were in a very exotic situation and thus the only reasonable analysis was on exotic lifeforms. Since O, B, A and F stars are more "normal" I'm going to switch to a more "life-as-we-know-it" approach and obviate exotic and less probable scenarios. But I have to warn you, now I'm going to be more pessimistic.

Problem with numbers
O, B, A and F stars constitute the 3,7% of the stars in the Milky Way galaxy, thus is less probable to find life in one of those than in any other kind of star just by numbers. This says nothing about habitability but says a lot about where we should focus our attention if our primary goal is to find life in the universe. For this reason little effort has been made in astrobiology to characterize the habitability of these systems (at least in comparison to G, K and M stars).

Problem with timespan
Hot main sequence stars have larger masses than our Sun and other cool stars. This means that they have larger amounts of nuclear fuel to combust. This alone would trick us into thinking that these stars can live longer than our Sun, but there's an effect that shrinks stellar lifespan: more mass means more gravitational pull, more gravitational pull means that the pressure and temperature inside the star can be very high indeed, this increases nuclear reaction rates and allows to more energetic nuclear reactions that are not accessible to other stars. This effect wins over the other and therefore hotter stars live shorter than cooler ones. In fact, these stars are hot mainly because they are combusting their nuclear fuel faster and more energetically.

This is a list of the lifespans for different stellar types:

  • M7  - 10.000.000.000.000 years
  • M4  - 4.000.000.000.000 years
  • M0  - 100.000.000.000 years
  • K2  - 25.000.000.000 years
  • G8  - 9.840.000.000 years
  • F5  - 4.910.000.000 years
  • B9  - 585.000.000 years
  • B5  - 94.500.000 years
  • B0.2 - 16.000.000 years
  • O8  - 6.510.000 years
  • O4  - 3.450.000 years
  • O3  - 2.560.000 years
As you can see O and B stars end quite quickly. The hypothetical protoplanetary disks around these stars wouldn't even have enough time to coalesce (around tens of millions of years are needed) into planetary bodies at the time the star explodes as a supernova. The coolest B stars could barely see their new-born planets before they die. A-type stars can form mature planets but even then life needs to emerge and that takes some hundreds of millions of years (at least in our case it was as little as that and it couldn't probably have been quicker). This means that life on A-type stars would probably be an incredible oddity.
The only possibility in terms of time is in F-type stars, that would have a few billion years for life to emerge. Even then, do not expect a huge evolutionary traverse (consider also that the star evolves in that timespan making habitable planets unhabitable in terms of hundreds of millions of years). On Earth life arouse in a matter of some hundreds million years but it was just single cell simple organisms for another billion years. Even the first insect had to wait for 4 billion years to appear since the formation of Earth. I wouldn't expect complex life on an F-star but surely I wouldn't bet for intelligent one.
This strict time regime make O, B, A and F stars even more uninteresting for astrobiologists. Even cool white dwarfs and neutron stars have larger prospects for habitability in terms of lifetime.

Problem with stellar winds
This is regarded as a huge problem (even if we ignore all the previous). Hot blue stars have an immense flux of particles in their stellar winds. They can lose between 10-6 and 10-5 solar masses each year by means of stellar winds. This means that in their ~1 to 10 Myr lifespan they can lose tens of times the mass of the entire sun as a continuous emanation. Compare that to our Sun that will have lost 0,034% of it's mass in 5 billion years.
Solar wind is a threat. It contributes to radiation in interplanetary space and if the planet is not protected with a magnetic field it can destroy their atmospheres slowly and dehydrate the planet (as has happened with Mars). Now imagine the stellar wind of a O, B or A star with a stellar wind ten billion times stronger. It would be an important issue for life. Their atmospheres would be bombarded with highly energetic particles.

We could locate the planet very far away and suppose a high magnetic field, but would it be safe enough? And would that distance to the star be compatible with the planet been gravitationaly bound to the system for sufficient time as to make life possible?

Problem with ionizing radiation
Hotter main sequence stars are more luminous than cooler ones. More luminous means more heat is transferred to a certain planet. The habitable zone defined by the temperature necessary to have liquid water on the surface of a hot star needs to be farther away logically. The habitable zone defined in this terms for O and B stars would lie between 5.000 and 10.000 AU from their star (compare that to the 39 AU distance of Pluto).
This might seem reasonable. A planet there could have oceans (even if we are reaching an important fraction of a light year distance). I'm going to ignore the probability of a planet forming at those extreme distances for a moment (let's suppose it was pulled there in the early stages of formation of the system and the orbit circularized enough to maintain the planet inside the thermal habitable zone along his orbit). The problem here is that stars that are hotter are not only more luminous in general but the increase in luminosity depends on the wavelength of light ("color").

Look at this graph. Here you have the intensity of the light emmited from some stars (at different temperatures) in terms of the wavelength of light. The peak intensity has been adjusted for all of them so they loom the same in the graph (a proportional graph would make very difficult to see the intensity for cooler stars and we are not caring for the general intensity itself but for how is distributed in terms of wavelength).

Image
Our star is a little cooler than the 6000K curve (so imagine this curve a little displaced to the right). The Sun emits a lot in the visible spectrum and less in the ultraviolet or infrared. Cooler stars than the Sun emit also visible light but the vast majority of the emission is in the infrared (these stars look red because inside the visible spectrum they emit a lot more in the red than in any other color). Now look at hottest star. This curve is generated by a B-type star with 24.000K temperature at surface. As you can see it emits a lot in the visible spectrum (more blue than red in this case), in fact it emits more visible light than our Sun (but since this graph has this condition that makes all peaks equal hight you can't see this from it). But the important thing here is the emission in ultraviolet light. It is huge compared to visible light emission! And this is just a B star, imagine an O star!. A and F stars also emit more ultraviolet radiation than visible light (but less than O and B stars).
Why this is important? Well because strong UV radiation can be extremely dangerous for life as we know it. The upper parts of our atmosphere absorb the UV radiation of the Sun and in that process water molecules and complex compounds are dissociated by radiolysis (if eroding the atmosphere by intense stellar winds was not enough). Strong UV is called ionizing radiation for a reason, it can break chemical bonds. DNA is severely damaged from UV radiation (mutations that can generate cancer are due to this effect in many cases). Even if we abstract ourselves from carbon based life we have to consider the fact that complex molecules are necessary for the complex biochemical reactions that produce all the processes to make a self-sustaining "natural automaton" and complex molecules have many chemical bonds that are susceptible to UV damage and complete dissociation.
If a planet is too close to a star it would absorb a lot of UV radiation. Therefore we can define an ultraviolet habitable zone where life can thrive without intense radiation doses. In O, B and A stars the minimum distance a planet should be to avoid getting fried by UV rays is farther away than the thermal habitable zone. A planet there would have no ionizing radiation problems but would be cold and frozen. Liquid water would be impossible. All of this has to do with the graph. O and B stars have their peak luminosity in the range of highly ionizing UV light. This was discovered in this research paper. Keeping it short: the thermal habitable zone and the ultraviolet habitable zone do not overlap in at least 60% of the cases studied.
The situation could be barely mitigated by considering a thick ozone layer. The planet could be closer since UV wouldn't penetrate so much but still not hot enough for life as we know it.
The only possibility here is for F-type stars that have their UV habitable zones in the external limits of their thermal habitable zones as was analyzed here. F stars are the best for habitability in our O, B, A and F populations as you can see (timespans are also barely good for life).
Life under water would be shielded from UV light so much as to be secure for some time (while UV light dissociates water molecules on the atmosphere and pushes the residuals into space dehydrating the planet slowly).


Problem with planetary formation
Planetary formation around strong UV light emiters as are O and B stars is very difficult. Ultraviolet radiation in the birth of a hot star play a huge role in opening a cavity in the interstellar medium.The protoplanetary disk is photoevaporated by the intense radiation and possibly no planets could even form.
We know of some protoplanetary disks around blue starsbut those are extremely far away from the star. Are these far disks capable of planet forming? How much time do they need to create the first planets if they rotational period is so large as it is?

Problem with variability
Finally, many O and B stars have large variations in their luminosity and that can destroy any climatic regularity to which life may have adapted.

Who is online

Users browsing this forum: No registered users and 1 guest