Starship Asterisk*

by **chuckster** » Mon Mar 10, 2014 5:29 am

LOVE IT
Time will tell. And I wish I could be there for the telling !

by **Beyond** » Sun Mar 09, 2014 10:59 pm

Here's another Vorlon reveal... the revealing of Kosh.

Click to play embedded YouTube video.

by **neufer** » Sun Mar 09, 2014 9:20 pm

Anthony Barreiro wrote:
I hope we can skew the Drake equation by sticking around for a while, even if that means we'll eventually have to wear tight polyester costumes and fight the Vorlons.

http://en.wikipedia.org/wiki/Vorlon wrote:
<<The Vorlon species is a member of the First Ones, a group made up of the earliest species to gain sentience in the galaxy. When in the company of aliens, Vorlons wear encounter suits to conceal their true form. The suits are large, cumbersome units with crest-like shoulders and elongated helmets and draping fabric; aside from a single illuminated iris to represent an eye/face, a Vorlon's shape cannot be deduced from the suit's design. While the official Vorlon explanation is that the suit maintains the specific environment necessary to support them, the actual reason is to hide their appearance. In actuality, Vorlons are incorporeal beings who require very little if any environment to survive; Vorlons have even managed to survive in vacuum with no ill effect.

A Vorlon's true shape, without the aid of telepathic projection, is that of a glowing cephalopod. Vorlon spaceships, being composed of the same organic foundation as their builders, illustrate this appearance in their squid-like design. The only occasion when a Vorlon's true form was viewed by humans was during the assassination of Vorlon Ambassador Ulkesh Naranek in Falling Toward Apotheosis, when his suit was shattered by weaponized electricity. Vorlons are known for speaking cryptically with brief phrases that vaguely relate to the question they are asked (e.g. "The avalanche has already started. It is too late for the pebbles to vote"). This is typically considered a limitation of their language as it is translated into English, Interlac, or other languages, but there remains speculation that they are deliberately obscure to prevent disruptions to the timeline.>>

by **Anthony Barreiro** » Sun Mar 09, 2014 8:55 pm

chuckster wrote: ... . I read someplace that the Milky Way is supposedly 12 billion years old (and the WMAP satellite finally pegged the Universe at 13.7 billion) which makes us a surprisingly old galaxy.

More recent data from the Planck satellite suggest an age of 13.82 billion years. But hey, what's a hundred million years or so between friends?

And as we build more sensitive telescopes we see galaxies at earlier and earlier ages of the universe, some that seem to have formed more than 13 billion years ago. So I wouldn't assume that the Milky Way is a remarkably old galaxy.

If we've got a sky full of red dwarfs outnumbering other star types by three to one, and we're in an old galaxy, we must be the young punks on the scale of galactic life around here. By some analysis, tech civilizations only spend a few thousand years broadcasting in ways we're equipped to detect, and then become directly involved in their own evolution and then disappear again. Not dead, just conducting business outside or beyond the EM spectrum. If we're surrounded by old civilizations (kind of the main theme of "Bablyon Five") I don't doubt they've chosen to leave us alone, or don't even particularly take notice, other than just as a minor data point. But in the absence of intelligent alien species, it seems overwhelmingly obvious that a large variety of situations could support life, even sunless, roving planets with geothermal vents beneath their frozen oceans.

At this point we know of only one planet with life, so what seems overwhelmingly obvious to you seems like an interesting but unproven hypothesis to me. But I hope we can skew the Drake equation by sticking around for a while, even if that means we'll eventually have to wear tight polyester costumes and fight the Vorlons.

by **chuckster** » Sun Mar 09, 2014 8:01 pm

Wow, thanks for the great, focused, subject-specific research and graphics (that I should've done for myself

) I get interested in this stuff, then get distracted, then come back and try to pick up where I left off, and maybe a little noise creeps into my knowledge base !

I didn't mean to suggest that a Sun-like star could be a stage of stellar death for some higher-order star. I was just trying to work out what you were saying about how a star can basically be born as a red dwarf. Also, you seem to suggest that planet formation will be slow in such a star system. I read someplace that the Milky Way is supposedly 12 billion years old (and the WMAP satellite finally pegged the Universe at 13.7 billion) which makes us a surprisingly old galaxy. If we've got a sky full of red dwarfs outnumbering other star types by three to one, and we're in an old galaxy, we must be the young punks on the scale of galactic life around here. By some analysis, tech civilizations only spend a few thousand years broadcasting in ways we're equipped to detect, and then become directly involved in their own evolution and then disappear again. Not dead, just conducting business outside or beyond the EM spectrum. If we're surrounded by old civilizations (kind of the main theme of "Bablyon Five") I don't doubt they've chosen to leave us alone, or don't even particularly take notice, other than just as a minor data point. But in the absence of intelligent alien species, it seems overwhelmingly obvious that a large variety of situations could support life, even sunless, roving planets with geothermal vents beneath their frozen oceans.

by **rstevenson** » Sun Mar 09, 2014 2:41 pm

That's a good chart showing the evolution of the Sun, but note the "not to scale" under the red giant stage. Here's an illustration (from Wikipedia) of the approximate size of the red giant stage compared to the Sun today, drawn to scale. Sol_now is the little yellow dot in the lower left; Sol_RedGiant is about 200 times larger.

Rob

by **Ann** » Sun Mar 09, 2014 9:46 am

chuckster wrote:Got it, and thanks. Main Sequence refers to H to He conversion, which can initiate at red dwarf levels or blue supergiant, etc

A main sequence star fuses hydrogen to helium in its core.

A red giant star fuses hydrogen to helium in a shell around its helium core. This star is not on the main sequence.

I'd thought that red dwarfs were always just the remains of bigger, hotter stars that died. But I guess all gas clouds aren't created equal, and the collapse, if and when it comes, doesn't always produce a nice yellow (or hotter) sun.

The collapse of a star doesn't ever produce a star like the Sun. Yes, it might do so, if the collapse and the ensuing explosion compresses gas clouds in the vicinity and triggers another round of star formation in those gas clouds. If that happens, a new star like the Sun might form. But the star that collapsed never turns into a star like the Sun after collapsing.

: Click to view full size image

This is an illustration of the life cycle of a star like the Sun. It begins forming inside a gas cloud, grows in mass until it becomes hot enough to start fusing hydrogen to helium in its core, and keeps on fusing hydrogen to helium in its core for billions of years until it runs out of core hydrogen. Then it leaves the main sequence forever. It fuses hydrogen to helium in a shell around its core, and after a while it starts fusing helium to oxygen and carbon in its core. After a while it becomes unstable, casts off its swollen atmosphere, exposes its hot inner core, and ionizes its cast-off atmosphere, which glows gloriously as a planetary nebula. Then the planetary nebula fades, and only the small, hot but cooling stellar core remains. It is called a white dwarf.

Ann

by **chuckster** » Sat Mar 08, 2014 9:22 pm

Got it, and thanks. Main Sequence refers to H to He conversion, which can initiate at red dwarf levels or blue supergiant, etc levels. I've spent many a lunch hour following the links in APOD writeups, but some basics seem to get lost on me in the rush. I'd thought that red dwarfs were always just the remains of bigger, hotter stars that died. But I guess all gas clouds aren't created equal, and the collapse, if and when it comes, doesn't always produce a nice yellow (or hotter) sun.

Count me among those who believe life is everywhere out there. I just hope the universe leaves us alone a little longer, and lets us catalogue our extrasolar microbes, slimes and invertebrates, before we have to contend with another technical civilization !

by **Anthony Barreiro** » Sat Mar 08, 2014 6:00 pm

chuckster wrote:...
In one documentary, it was stated that, in our galaxy, red dwarfs outnumber main sequence stars by 3 to 1, ... .

This statement doesn't make sense to me. Red dwarves are main sequence stars, happily fusing hydrogen into helium for tens of billions of years. I.e., they're going to be on the main sequence long after bigger stars like our Sun have run out of hydrogen and died. Just as ants outnumber elephants, red dwarves outnumber larger main sequence stars. But ants and elephants are both animals, and red dwarves and stars like our Sun are both main sequence stars.

by **Ann** » Sat Mar 08, 2014 8:43 am

chuckster wrote:
Aren't there certain conditions under which a star collapses but doesn't lose enough mass to change the orbits of its planets ?

I think you are talking about a Type II (a core-collapse) supernova. A core-collapse supernova is a product of a massive star, many times more massive than a red dwarf, whose core has built up heavier and heavier elements until no more energy can be extracted from further fusion, and therefore the core collapses and the star explodes.

Typically a Type II supernova explosion will leave behind a neutron star or a pulsar with a mass a little more than 1.4 solar masses. This is still a lot more than the typical mass of a red dwarf.

It isn't known what happens to the planets that were in orbit around the star that later went supernova. Maybe the planets survived, maybe not. New planets may form from the massive amounts of dusty debris that are produced by the supernova explosion.

Or will things get rearranged in that star system when the star goes dwarf, as in some planets flying away and others finding new, closer orbits ?

Our own Sun became a so called "yellow dwarf" at the point when it got hydrogen fusion going in its core. At that point, the Sun entered the main sequence, which is the time in the life of a star when it produces energy by fusing hydrogen to helium in its core.

Red dwarf stars are also main sequence stars, because they, too, fuse hydrogen to helium in their cores. But red dwarfs are always less massive than the Sun. A typical mass of a red dwarf may be half the mass of the Sun, but it may contain as little as about 8% the mass of the Sun.

Because red dwarf stars don't contain a lot of mass, they accrete mass slowly and grow slowly. It takes a long time for them to get their hydrogen fusion going.

Planets, which are even less massive than red dwarfs, probably form even more slowly than the red dwarfs themselves. To my knowledge, the onset of hydrogen fusion in a red dwarf isn't likely to upset the orbits of any planets, for two reasons. I don't think that the onset of hydrogen fusion is a very violent process (certainly not in comparison with the titanic explosion of a supernova), and in any case, the newborn red dwarf may not yet have any planets.

However, planetary scientists believe that planets may migrate so that they end up closer to or farther away from the star than the position in the proto-planetary disk where they were born. It is also true that planets may be kicked out of the solar system where they were born.

I suppose you could postulate a former frozen planet thawing out now and providing the liquid water to get things going.

There has been speculation that, say, Saturn's largest moon Titan might become nice and warm after the Sun has become a red giant. When that happens, the Earth will be burnt to a crisp. But when we are talking about red dwarfs, the stars themselves are not going to grow much larger or become a lot more energetic for hundreds of billions of years. Of course a planet orbiting a red dwarf may migrate inside its own solar system, so that it ends up in the red dwarf's habitable zone. But remember that the habitable zone of the red dwarf (where water may become liquid) is so small that a planet moving in there will become tidally locked.

If a red dwarf lives so much longer than it's former yellow self, I guess you' would have to consider it part of the main sequence.

A star that is a red dwarf has never been a yellow dwarf in the past, and it will never become a yellow dwarf in the future, unless it, for some reason, stars to accrete a lot of mass.

But certainly, a red dwarf star fuses hydrogen to helium in its core, and therefore it does, indeed, belong to the main sequence.

Ann

by **chuckster** » Sat Mar 08, 2014 6:44 am

Aren't there certain conditions under which a star collapses but doesn't lose enough mass to change the orbits of its planets ?
Is that true of a red dwarf ? Or will things get rearranged in that star system when the star goes dwarf, as in some planets flying away and others finding new, closer orbits ? I suppose you could postulate a former frozen planet thawing out now and providing the liquid water to get things going. And how much heat could circulate to the cold side via, say, atmospheric movement ? Probably some nasty winds.
I wonder if life that developed around deep sea volcanic geysers could survive such a radical change in the parent star whose light never penetrated to their depth. Since the whole star system got old, would a red dwarf star have planets that still have molten centers, or would they be so old that they've cooled off, and their magnetic shields are gone ? Oh well, some of this is going on somewhere out there. If a red dwarf lives so much longer than it's former yellow self, I guess you' would have to consider it part of the main sequence.

by **Chris Peterson** » Sat Mar 08, 2014 6:27 am

chuckster wrote:In one documentary, it was stated that, in our galaxy, red dwarfs outnumber main sequence stars by 3 to 1, so they represent numerous opportunities for things to not be so easy for life to arise.

Not sure what they meant by that. Red dwarfs are main sequence stars. Because of their low mass, they are very long lived; while they may be any age, the oldest are probably nearly as old as the Universe, and still haven't left the main sequence. Many red dwarfs have planets. Habitability, of course, is largely a matter of definition at this point. Planets around red dwarfs are likely to be very different from Earth, which suggests that any life is likely to be quite different, as well.

by **Ann** » Sat Mar 08, 2014 6:07 am

chuckster wrote (before editing):
In one documentary, it was stated that red dwarfs outnumber main sequence stars by 3 to 1, and therefore life has had a lot of chances to arise on any orbiting planets during the dying stages of many stars.

This is a good and interesting point. On one hand, the surfaces of planets orbiting in the habitable zones of red dwarfs are problematic places for life (not impossible, but problematic). On the other hand, life has a long, long, long time to make it either on the surface or below the surface of such a planet.

Since the habitable zone of a red dwarf is so small, a planet orbiting there will become tidally locked, so that one side of the planet always faces its sun. The opposite side of the planet will always face away from the star. This arrangement should be disadvantageous for life on the surface of such a planet, although it may not at all be impossible. Of course, life below the surface may not be affected at all.

And the long, long, long-lasting existence of a red dwarf will certainly give life many chances to find a way to survive on the surface or below the surface of a planet in orbit of such a star.

But suppose it really does take a long time for life to find a way to make it on the surface of a planet orbiting a red dwarf. If so, life may not have had enough time to establish itself on the surface of a planet of a red dwarf. Remember that the universe is "only" about 14 billion years old.

Ann

by **chuckster** » Sat Mar 08, 2014 5:11 am

Thanks for the insights ! I flew the radius of the solar system in that link you provided - I think it brings home the meaning of distance in a more "tangible" (i.e. finger on the right arrow key) way than most. The comments along the way were entertaining and mind-expanding. Now I'll go read that link on Alpha Cen.

Let me leave you with another insight, from a fictional physicist in the novel "Fiasco" by Stanislaw Lem :

"Physics, my friend, is a narrow path drawn across a gulf that the human imagination cannot grasp. It is a set of answers to certain questions that we put to the world, and the world supplies answers on the condition that we will not then ask it other questions, questions shouted out by common sense. And common sense? It is that which is understood by an intelligence using senses no different than those of a baboon."

by **geckzilla** » Sat Mar 08, 2014 4:13 am

There are a couple of references in the Alpha Centauri's Wikipedia article regarding the existence of a possible planet. See the fourth paragraph from the top. For the wobble method to work, the wobble has to be significant enough to be detectable. Maybe something is there but it's not detectable. They looked at it, said there was one there, looked again, then said maybe it's not there. For Alpha Cen, any planets may be lost in the noise for a while yet.

by **chuckster** » Sat Mar 08, 2014 3:58 am

I guess I got caught up in the "blocking in" of the question of exoplanets in greenzones. It's one thing to assay the relative populations of star types in the Milky Way, and another for the universe at large. I read someplace that, for Jupiter to have gravitationally collapsed and begun fusing, it would have had to be 11 times larger.

I've also read that when we look at Alpha Centauri from Earth, we see a single point of light that is really both of the Sunlike stars buried in each other's glare. But as far as I know, for exoplanet search purposes, that doesn't matter. All the currently listed exoplanets orbit stars a LOT further away then Alpha Cen. If the transit method only works when our ecliptic is coplanar with the target star's, then what about the wobble method ? Isn't that a Doppler shift measurement ? Has this been done on the Alpha Cen system ?

by **geckzilla** » Sat Mar 08, 2014 2:59 am

chuckster wrote:There's been an "are we alone week" running on cable this week, that got me thinking, and I had a couple questions that maybe someone on here can help me with.
In one documentary, it was stated that red dwarfs outnumber main sequence stars by 3 to 1, and therefore life has had a lot of chances to arise on any orbiting planets during the dying stages of many stars. OK, but what is the ratio of double star systems to single systems, like ours ? If red dwarves are so numerous, and ostensibly unlikely to host life, aren't double stars also highly unlikely to do so, and are even more numerous than the dwarves ? And how many of those red dwarves are orbiting a barycenter with a main sequence star ? I remember something about Poincarre's three-body problem being unsolvable and a prime example of nonlinear dynamics, etc, so does that mean double (or more) star systems are, by definition, not eligible to harbor planets in a Goldilocks zone, because they would never allow orbiting planets to settle into stable orbits at all ? To me, it seems that single-star systems are the only happy hunting ground, using any method of detection.
Finally, in all the talk of exoplanets we don't hear much about good ol' Alpha Centauri. Granted, it's a two- and possibly three- star system, but at 4.5 light years, can't we get a better look at what's going on out there somehow ?

THANK YOU

The Universe's occupants comes in many shapes and sizes so you'll just have to use your imagination on all of the many configurations out there. A double star system doesn't have to preclude life if the stars are positioned correctly. Some interesting dynamics are possible with such a system. I imagine a larger star with a very small star, sort of like our system except replace Jupiter with a small star. If everything is just right, maybe you could have more than one habitable zone in such a system. Maybe that makes it twice as likely to harbor life.

Alpha Centauri... we can't even see Pluto and its angular diameter is 0.063″ – 0.115″ depending on its current orbital position. Alpha Centauri A is 0.007″, which is only 6% as big as Pluto under Pluto's best possible viewing conditions. Space between objects is unfathomably big. I know it's getting hackneyed to say things like that but go ahead and click that link.

by **chuckster** » Sat Mar 08, 2014 2:28 am

There's been an "are we alone week" running on cable this week, that got me thinking, and I had a couple questions that maybe someone on here can help me with.
In one documentary, it was stated that, in our galaxy, red dwarfs outnumber main sequence stars by 3 to 1, so they represent numerous opportunities for things to not be so easy for life to arise. If red dwarves are so numerous, and ostensibly unlikely to host life, aren't double stars also highly unlikely to do so, and are even more numerous than the dwarves ? And how many of those red dwarves are orbiting a barycenter with a main sequence star ? I remember something about Poincarre's three-body problem being unsolvable and a prime example of nonlinear dynamics, etc, so does that mean double (or more) star systems are, by definition, not eligible to harbor planets in a Goldilocks zone, because they would never allow orbiting planets to settle into stable orbits at all ? To me, it seems that single-star systems are the only happy hunting ground, but everything I've seen and read so far is silent on this.
Finally, in all the talk of exoplanets we don't hear much about good ol' Alpha Centauri. Granted, it's a two- and possibly three- star system, but at 4.5 light years, can't we get a better look at what's going on out there somehow ? It's our closest neighboring star system, so what say the exoplanet hunters ?

THANK YOU

by **Chris Peterson** » Wed Mar 05, 2014 5:28 am

Beyond wrote:But it's a lot better than expiring! :yes:

If it doesn't ever warm above freezing, however, "dormant" and "expired" are functionally the same

by **Beyond** » Wed Mar 05, 2014 5:16 am

But it's a lot better than expiring!

by **Chris Peterson** » Wed Mar 05, 2014 4:14 am

BMAONE23 wrote:The Tardigradewould have no problem at -92c

A tardigrade at that temperature survives by becoming dormant. That isn't thriving.

by **BMAONE23** » Wed Mar 05, 2014 4:01 am

http://www.dailymail.co.uk/news/article ... years.html

Boil the 1mm creatures, freeze them, dry them, expose them to radiation and they're so resilient they'll still be alive 200 years later. Water bears can hack temperatures as low as -457 degrees, heat as high as 357 degrees, and 5,700 grays of radiation, when 10-20 grays would kill humans and most other animals. The animals can also live for a decade without water and even survive in space

The Tardigradewould have no problem at -92c

: Click to view full size image

Click to play embedded YouTube video.

by **Chris Peterson** » Wed Mar 05, 2014 3:51 am

Ann wrote:Are there really life forms on the Earth that thrive at a mean temperature of -92 C? And are there really many places on the Earth that have colder mean surface temperatures than -92 C?

Colder mean temperatures? No. But the coldest temperatures are right around that, and have nearby life (such as below the surface). Europa is much colder on the surface, but is probably habitable not far beneath that. So it's no real stretch to presume that a planet with a - 92°C surface temperature could support Earth-like lifeforms.

by **Ann** » Wed Mar 05, 2014 2:32 am

Chris Peterson wrote:
BDanielMayfield wrote:In the order in which they are presented in today's APOD, the estimated mean temperatures in degrees C of these exoplanets (per Wikipedia) are:

Upper row: 23, -3, 70, -24, -34, 6
Lower row: 59, 0, 22, -65, -64, -92
I believe those are mean surface temperatures, not mean temperatures. Certainly, we have examples of lifeforms on Earth that can thrive at any of these, and we have a wider range of local temperatures on the Earth than this.

Are there really life forms on the Earth that thrive at a mean temperature of -92 C? And are there really many places on the Earth that have colder mean surface temperatures than -92 C?

Ann

by **Chris Peterson** » Wed Mar 05, 2014 1:04 am

Ann wrote:But when it comes to planets actually harbouring life, we still have an example of one, namely the Earth.

But understand, when you review exobiology publications, only a tiny fraction even deal with other planets, or searching for life elsewhere. The vast majority are papers exploring lifeforms on Earth, exploring biogenesis, exploring alternate organic chemistries. Exobiology is, first and foremost, about understanding life along broader principles than just the examples we have.

Starship Asterisk*

APOD: Habitable Worlds (2014 Mar 03)

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