APOD: Zarmina s World (2010 Oct 01)

[Richard Melton]

There is NO WATER on Zarmina!

It is easy to calculate that among the 100 billion known galaxies, each with an average of 100 billion stars that there are likely to be somewhere around 100 billion trillion planets. So, given what we know about matter and the universe, it is easy to speculate that there is life on some of those planets. But, I am extremely disappointed in the lack of credible science in statements that Gliese 581g might have water and even life. There is NO possibility that there could be water or life on the planet Gliese 581g. The star that it orbits is a red dwarf. To be a red dwarf it had to have gone through a phase, after it was similar to our sun, when its super hot gasses expanded to beyond its planets range for millions of years, before it collapsed back into a red dwarf. During that expanded phase it would have burned off all the atmosphere and water, leaving only the hardest rock. So, being in the not too hot or too cold distance from its star at the moment does not make life possible there. It has NO atmosphere and NO water.

[Chris Peterson]

Zarmina's world's star is reputed to be the former. It could be a young red dwarf or an old red dwarf. That info. hasn't been provided to us in this APOD entry.

The paper proposes a mass of about 0.3 times the Sun, a luminosity of 0.013 times the Sun, a metallicity equal or slightly less than the Sun, and an age of 4.3 Gyr.

The luminosity of the star, combined with the distance of the planet under discussion, suggest that the apparent brightness at the surface of the planet would be about half that of the Sun on the Earth. The light would certainly be reddish, but not red; I imagine something like what you'd see through a warm photo filter. Our eyes would quickly adapt to it, making things appear similar to the way we see them with our own Sun.

[hstarbuck]

If one side always faces the star (proposed), then would sleep develop in the (possible) animals/creatures?

[neufer]

I have learned about the 3 methods of detecting planets around stars, but how can you know it is tidally locked?

I think it is an assumption, but solidly based on the expected behavior of an Earth-mass rocky planet only 0.15 AU from its parent star.

Based on the fact that earth-like Venus is almost tidally locked I would estimate that:
Any habitable planet in (circular) orbit around a main sequence dwarf star
would be tidally locked if that star was cooler than a K5.

[neufer]

If one side always faces the star (proposed), then would sleep develop in the (possible) animals/creatures?

No:
----------------------------------------

• The Chicken Roaster

Kramer: Its killing me, I can't eat, I can't sleep,
all I can see is that giant red sun in the shape of a chicken.
You're a heavy sleeper, right? Why don't we switch apartments?

Jerry: If I'm gonna live over there, you gotta take some of this stuff out.
I mean this thing is really freaking me out. I feel like its gonna
come to life in the middle of the night and kill me.

[Jerry holds up a doll]

Kramer: Mr. Marbles? He's harmless.

Jerry: Well don't get too comfortable, as soon as Seth gets
a real job you are gong back in that chicken supernova.

[Jerry puts on giant sunglasses and goes to Kramer's apartment.]

[Later: Enter Jerry, his hair is like Kramer's. Jerry enters doing Kramer's slide]

Jerry: Hey everybody, I'm on no sleep, no sleep!. You don't know
what it's like in there, all night long things are creeping and cracking.
And that red light is burning my brain!
----------------------------------------

[neufer]

The orbits of the Gliese 581 planetary system.

---

http://asterisk.apod.com/vie ... 23#p133223

<<Gliese 581 c initially generated interest because it was originally reported in April 2007 to be the first potentially Earth-like planet in the habitable zone of its star, with a temperature right for liquid water on its surface, and by extension, potentially capable of supporting extremophile forms of Earth-like life. It has since been shown that under known terrestrial planet climate models, Gliese 581 c is likely to have a runaway greenhouse effect, somewhat like Venus, and hence is probably not habitable. A subsequently discovered planet Gliese 581 d, somewhat like Mars, may be just inside or just outside the outer boundary of the habitable zone (depending in part on the greenhouse properties of its atmosphere). The discovery of exoplanet Gliese 581 e, at that time the closest-known in mass to Earth, was announced in April 2009. Excitement has again spiked with the discovery of Gliese 581 g, orbiting in-between Venus-like c and Mars-like d, thus believed to be the most "Earth-like" planet discovered to date, in September 2010.>>

<<The SETI Institute has examined Gliese 581 c "hoping to pick up radio signals that would prove that someone was there," followed by the statement that "no transmissions were detected.">>

<<A Message from Earth (AMFE) is a high-powered digital radio signal that will reach the planet Gliese 581 g in early 2029.

A vote was held to select the 501 messages that were to be included in the digital time capsule, when its users had submitted their messages. Images of notable landmarks and famous people in the world had also been included in the message. Images of the London Eye and Edinburgh Castle were among the landmarks that were selected to be included, while pictures of Hillary Clinton, Cheryl Cole and Richard and Judy were some of the selected images of famous people.

• I understand that in the majority of cases these messages may be naïve,
  but I also hope that we will receive a creative and fresh look at the subject. —Dr. Alexander Zaitsev
  
  If anybody's out there and they find that signal, they at least know that...
  there must be a planet with some pretty clever things on it. —Seth Shostak

The launching of the composed message as a digital time capsule took place on 9 October 2008, at 06:00 GMT. The message, containing all selected 501 text messages and images, was translated into a binary format and included in the digital time capsule. It was transmitted in a high-powered radio wave emitted from the RT-70 interstellar radar telescope of the National Space Agency of Ukraine, located in Yevpatoria (Crimea). As of July 1, 2010 the message has traveled 10.1 trillion miles of the 118 trillion mile trip.

Half a league half a league,
Half a league onward,
All in the valley of Death
Rode the 501:

'Forward, the Light Brigade!'
Was there a man dismay'd ?
Not tho' the soldier knew
Some one had blunder'd:
Theirs not to make reply,
Theirs not to reason why,
Theirs but to do & die,
Into the valley of Death
Rode the 501.

[Guest]

Three things …

First, I essentially copy and paste about 30% - 40% of the APODs, do a little editing, almost invariably add my “tutorials,” and send them on to a large number of friends, including quite a few young folks. One of my prejudices is that giving distances in light years is not very informative to novices who want to know about astronomy but don’t have the “requisite” technical backgrounds.

By way of example, the explanation above says “a mere 20 light-years away …” So we’re talking about a planet that possibly sustains life and it’s “just over there on the next block.” To make that distance a bit more meaningful to my readers, I edit it thusly …

R,W, Hoyer

Hmmmmmmm...............you mean only 6.13247495 Parsecs away right????

[Ann]

It's been incredibly enjoyable to read this thread. Thank you, Léon, for that great picture of Christopher Columbus!

Art, you have outdone yourself. Thank you so much for the entertainment. Where did you find that marvellous picture of "A Glieson 581"? Where is the "rolling on the floor, laughing out loud" smilie? Okay, this one will have to do:

I should probably google that Jerry and Kramer thing, but I don't have the energy. I don't recognize the text or the characters, and I feel sorry for poor Kramer, but the utter absurdity of the whole thing is just my bowl of tomato juice cereal and bloated red sun in the sky!

And your take on The Charge of the Light Brigade was sheer genius. Yes indeed, into the Valley of Death - that is, into leage after leage of trillions of kilometers and miles of blackness and near vacuum and near-zero temperatures, interspersed with the odd high-energy particle and gamma-ray photon - rode the 501 messages for Gliese 581c! Now we are just waiting for the 501 messages for Gliese 501g to make the same trip!

Chris, I noted that you said this:

The paper proposes a mass of about 0.3 times the Sun, a luminosity of 0.013 times the Sun, a metallicity equal or slightly less than the Sun, and an age of 4.3 Gyr.

Really? According to my astronomy software, the luminosity of Gliese 581 is about 0.002 times the Sun. Of course, that refers to Gliese 561's V luminosity, its luminosity in yellow-green light. (In fact, I should say that the wavelength measured as V luminosity by Hipparcos is closer to the blue-green than to the yellow-green part of the spectrum.) When you say that Gliese 581's luminosity is 0.013 times the Sun, what wavelength does that refer to? Are we perhaps talking about the bolometric (total) energy output of Gliese 581 versus the bolometric (total) energy output of the Sun?

Ann

[Ann]

I'd like to add that I personally don't believe that there is any life on Gliese 581g, for the simple reason that this planet must have a locked rotation around its sun. Yes, I know that people have run computer simulations that seem to show that there ought to be a habitable "ring" along the "twilight zone" of such a planet, but sometimes, frankly, the computer simulations don't look the same as the reality out there. My impression is that those computer simulations describe a "best-case scenario". The scientists (or computer nerds) have asked themselves, "Is it impossible for life to exist on a planet with a tidally locked rotation?". And then they have done their simulations and found that, no, it is not impossible, not if we only look at the habitability of a planet as a function of its temperature in its twilight zone. But if the temperature of the twilight zone of Gliese 581g doesn't make it impossible for life to exist there, does that mean that it is probable that we should find life in the twilight zone of Gliese 581? No one has shown that, as far as I know.

But I agree with everyone that Glese 581 is a hugely fascinating solar system. I, too, would just love to find out more about it!

Ann

[DavidLeodis]

Send a probe!

But the inhabitants may send a probe back and I don't fancy being probed!

Being serious though, at only 20 light years away it is very close. If there is life there I wonder if they wonder if there is life here on Earth. I just hope they have not discovered reality television programs!

[bystander]

The star that it orbits is a red dwarf. To be a red dwarf it had to have gone through a phase, after it was similar to our sun, when its super hot gasses expanded to beyond its planets range for millions of years, before it collapsed back into a red dwarf.

I think you need to read what a red dwarf is.

[Chris Peterson]

Chris, I noted that you said this:

The paper proposes a mass of about 0.3 times the Sun, a luminosity of 0.013 times the Sun, a metallicity equal or slightly less than the Sun, and an age of 4.3 Gyr.

Really? According to my astronomy software, the luminosity of Gliese 581 is about 0.002 times the Sun. Of course, that refers to Gliese 561's V luminosity, its luminosity in yellow-green light. (In fact, I should say that the wavelength measured as V luminosity by Hipparcos is closer to the blue-green than to the yellow-green part of the spectrum.) When you say that Gliese 581's luminosity is 0.013 times the Sun, what wavelength does that refer to? Are we perhaps talking about the bolometric (total) energy output of Gliese 581 versus the bolometric (total) energy output of the Sun?

From the paper, The V-band bolometric correction of 2.08 (Delfosse et al. 1998) yields a luminosity of 0.013 L⊙.

If we simply use the absolute visual magnitudes (Gliese: V=10.55, Sol: V=4.84) we get an intensity difference of 194; that is, Gliese has a V-band intensity of 0.005 if the Sun is taken as 1. Either way, there's lots of light there, which was the important point.

[Chris Peterson]

I'd like to add that I personally don't believe that there is any life on Gliese 581g, for the simple reason that this planet must have a locked rotation around its sun. Yes, I know that people have run computer simulations that seem to show that there ought to be a habitable "ring" along the "twilight zone" of such a planet, but sometimes, frankly, the computer simulations don't look the same as the reality out there.

I believe that the models are probably reasonably accurate in terms of the broad climate patterns seen on a tidally locked planet with a substantial atmosphere. What isn't known at all is what conditions are actually required for life to develop, so any discussion about this is bound to be highly speculative.

There is certainly a case to be made that life is more probable on a tidally locked planet because of the terminator dynamics. This is related to the idea that life on Earth developed in extreme tidal zones (lunar tides were much stronger early in the Earth's history). I note also that if Gliese 581g is a water planet like Earth, none of the models are able to describe what's going on in deep water, and we know that life on Earth does very well in the depths.

Personally, I have no opinion at all on whether Gliese 581g has life on it. There simply isn't enough evidence to even hint at an answer to that question.

[Ann]

Chris wrote:

If we simply use the absolute visual magnitudes (Gliese: V=10.55, Sol: V=4.84) we get an intensity difference of 194; that is, Gliese has a V-band intensity of 0.005 if the Sun is taken as 1.

Interesting. According to my astronomy software, Gliese 581 has an absolute V magnitude of 11.584. That is a whole magnitude fainter than the paper you refer to. Someone must have made a significant mistake here.

Ann

[bystander]

frankly, the computer simulations don't look the same as the reality out there.

And you know what reality is out there? You've been out there?

[Chris Peterson]

Interesting. According to my astronomy software, Gliese 581 has an absolute V magnitude of 11.584. That is a whole magnitude fainter than the paper you refer to. Someone must have made a significant mistake here.

What software? Most of it uses a mix of catalogs, and most catalogs do not contain very accurate photometric data. I do a lot of photometry, and generally cannot rely on standard catalogs to provide accurate photometric references.

The Hipparcos catalog, which is pretty good photometrically, gives V=10.5759±0.004. An error of a full magnitude might suggest your software is using GSC data, which has notoriously poor photometric values.

[Ann]

frankly, the computer simulations don't look the same as the reality out there.

And you know what reality is out there? You've been out there?

Well, obviously I haven't.

I guess I'm speaking from a sense of disappointment that Mars and Venus didn't turn out to be what many planet enthusiasts predicted that they would be before we had actually sent probes to those planets. Like I've said before, I vividly remember reading an early 1960s Readers Digest style article about Mars. While the article clearly tried to curb its readers most optimistic expectations - the article clearly stated that there were no little green men on Mars - it did say, nevertheless, that there was almost certainly vegetation on Mars. That is what I believed in for years after reading that article.

I also remember reading about Venus in my local newspaper in the early seventies. The paper's regular science reporter was devastated because NASA had just released the news that Venus was almost impossibly hot. I clearly remember that the science reporter explained that according to the best models that we had for the temperature of Venus, its surface temperature "ought" to have been a little below a 100 degrees Celsius, which is the temperature at which water boils at the typical atmospheric pressure at sea level of the Earth. Instead, Venus turned out to be more than four times hotter than that.

It could be that we were just "unlucky" with our predictions about Mars and Venus. Perhaps we have become much better at predicting the degree of habitability of other planets since the sixties and seventies. I certainly don't claim to know that there is no life on Gliese 581g, bystander!

Ann

[Ann]

I'd like to add that I personally don't believe that there is any life on Gliese 581g, for the simple reason that this planet must have a locked rotation around its sun. Yes, I know that people have run computer simulations that seem to show that there ought to be a habitable "ring" along the "twilight zone" of such a planet, but sometimes, frankly, the computer simulations don't look the same as the reality out there.

I believe that the models are probably reasonably accurate in terms of the broad climate patterns seen on a tidally locked planet with a substantial atmosphere. What isn't known at all is what conditions are actually required for life to develop, so any discussion about this is bound to be highly speculative.

There is certainly a case to be made that life is more probable on a tidally locked planet because of the terminator dynamics. This is related to the idea that life on Earth developed in extreme tidal zones (lunar tides were much stronger early in the Earth's history).

I didn't quite get that, Chris. Do you mean that there is a greater chance for life to develop on a tidally locked planet than on a planet that isn't tidally locked, like the Earth? Why would it be easier for life to develop on a tidally locked planet?

Ann

[Ann]

Interesting. According to my astronomy software, Gliese 581 has an absolute V magnitude of 11.584. That is a whole magnitude fainter than the paper you refer to. Someone must have made a significant mistake here.

What software? Most of it uses a mix of catalogs, and most catalogs do not contain very accurate photometric data. I do a lot of photometry, and generally cannot rely on standard catalogs to provide accurate photometric references.

The Hipparcos catalog, which is pretty good photometrically, gives V=10.5759±0.004. An error of a full magnitude might suggest your software is using GSC data, which has notoriously poor photometric values.

You are right, my software uses a mix of catalogs. It appears that my software has been using GSC data for Gliese 581.

Ann

[Chris Peterson]

I didn't quite get that, Chris. Do you mean that there is a greater chance for life to develop on a tidally locked planet than on a planet that isn't tidally locked, like the Earth? Why would it be easier for life to develop on a tidally locked planet?

I simply mean that there is an argument to be made for that. A geographically small, environmentally dynamic region may be just the sort of thing required for the development and early evolution of life. It has been suggested that life on Earth began in ocean tidal zones for precisely the same reason.

I'm not saying I either agree or disagree with this theory, only that it has been offered up by people who study such things, and is taken seriously. Any discussion concerning the conditions under which life can develop is necessarily speculative.

[emc]

A Red Dwarf and a Red Giant are very different stars.

A Red Dwarf is a small star (smaller than our Sun) so that the nuclear furnace cooks more slowly because of decreased pressures at its core. As a consequence it is cooler and only red.

A Red Giant is a star in the final stages of life. It has used up much of its nuclear fuel and has switched to a different nuclear process, making even heavier elements than Helium. In the process, it bloats its surface far from its core and makes the star huge (and red).

Zarmina's world's star is reputed to be the former. It could be a young red dwarf or an old red dwarf. That info. hasn't been provided to us in this APOD entry.

Hi Craig, Thank you for clearing up my stupid assumption regarding red stars. I should have done a little research before posting but I got caught up in the moment when I thought I had something interesting and fun to say.

There are a lot of bright and shiny people reading and posting in Asterisk*… it's intimidating... I try too hard sometimes to NOT be boring.

[NoelC]

Food for thought...

If we, at the very dawn of technological advance - at the virtual instant of scientific advancement beyond satisfying basic needs - can already detect extrasolar planets capable of supporting life, what can we imagine a civilization out there of, say, 1 million years of advancement can see of us?

Could the others out there - perhaps after having constructed a telescope with an aperture the size of a planetary orbit - be studying our society close-up... Reading headlines on papers tossed in front lawns (okay, so the news might not be too fresh after traversing some tens of light years, but they might find it interesting)... Mapping our planet for their own Google Earth app... Planning their invasion...

-Noel

[Ann]

Interesting. According to my astronomy software, Gliese 581 has an absolute V magnitude of 11.584. That is a whole magnitude fainter than the paper you refer to. Someone must have made a significant mistake here.

What software? Most of it uses a mix of catalogs, and most catalogs do not contain very accurate photometric data. I do a lot of photometry, and generally cannot rely on standard catalogs to provide accurate photometric references.

The Hipparcos catalog, which is pretty good photometrically, gives V=10.5759±0.004. An error of a full magnitude might suggest your software is using GSC data, which has notoriously poor photometric values.

Wait, Chris! I think I have figured it out!

My software gives a GSC measurement for this star, but there is a Hipparcos measurement, too. Hipparcos says that the maximum V luminosity of Gliese 581 is 10.49, and its minimum V luminosity is 10.60. Could it be that the variability has anything to do with the many planets of Gliese 581?

My software also quotes "Johnson", whose measurement gives a V luminosity of 10.57 for this star.

Yes, but the given V magnitudes (10.49, 10.57, 10.60) are not absolute magnitudes. They are the V magnitudes measured for this star at its distance from us, which is, according to the Hipparcos measurements, 20.45 ± 0.29 light-years. But the absolute magnitude for a star describes how bright it would be if it was seen from a distance of ten parsecs. I can never remember exactly how much ten parsecs is, but I know that it is a little more than thirty light years.

So the V luminosity of Gliese 581 is about 10.55 at a distance of about 20 light-years. But if it had been seen at a distance of about 30 light-years, then its V luminosity would probably have been about 11.50 after all.

Chris, I think I'm right here. I think that the absolute V luminosity of Gliese 581 is about 11.50.

Ann

[Chris Peterson]

My software gives a GSC measurement for this star, but there is a Hipparcos measurement, too. Hipparcos says that the maximum V luminosity of Gliese 581 is 10.49, and its minimum V luminosity is 10.60. Could it be that the variability has anything to do with the many planets of Gliese 581?

I don't see any connection there.

My software also quotes "Johnson", whose measurement gives a V luminosity of 10.57 for this star.

"Johnson" just defines a particular set of photometric filters, commonly used. This lets people know the type of filter, which allows for conversion of magnitude to different scales.

Yes, but the given V magnitudes (10.49, 10.57, 10.60) are not absolute magnitudes. They are the V magnitudes measured for this star at its distance from us, which is, according to the Hipparcos measurements, 20.45 ± 0.29 light-years. But the absolute magnitude for a star describes how bright it would be if it was seen from a distance of ten parsecs. I can never remember exactly how much ten parsecs is, but I know that it is a little more than thirty light years.

Good catch. I looked at the Hipparcos catalog, and the stated value ("Hpmag") is indeed the apparent magnitude. Taking the Hipparcos parallax (0.16091 arcsec) gives a distance of 6.22 parsecs, which allows for conversion to an absolute magnitude (based on 10 pc) of 11.6.

Chris, I think I'm right here. I think that the absolute V luminosity of Gliese 581 is about 11.50.

Pretty close. But the GSC value is apparent, so it is simply in error.

[dahowa]

I notice that the artist has included a healthy amount of green on the planet. Not only is it shown as livable, but alive!