Exoplanet Stats

[Helio]

There are now 5058 exoplanets listed in the exoplanet.eu catalog.

The results are the same as before with 113 in the HZ but only 8 exoplanets about the size of Earth (radii shown).



Here are those 8 per star type:


[Again, the red highlight simply means it isn't observable from the US (i.e. Tuscalosa).

I've been tweaking the program, as usual, and by adjusting for the HZ expansion line outward due to eccentric orbits, there seems to be no significant change to the count.

Eccentricities, per one paper, show an increase in the radiant flux received from the star. Given that high eccentricities gives a planet much more time farther from the star (ie colder regions) then it is non-intuitive, at least for me, that more heat is received. Of course, the inverse square law makes-up the difference during periapsis, no doubt, but it's still not intuitive.

 

[Catastrophe]

Helio, in the context of intelligent life et cetera, what are the 3 nearest exoplanets with approx Earthlike conditions, allowing for aliens to be slightly different.

I am just trying to get a feeling for the number within communicable distance time span. Any things 50 light years apart, for example, are going to have a 100 years conversation unit.

I do not want to contaminate your thread with alien stuff. I am just asking to introduce (or you can) such information into the relevant thread.

Cat

 

[Helio]

I do not want to contaminate your thread with alien stuff. I am just asking to introduce (or you can) such information into the relevant thread.

I'm happy to oblige! The purpose of the program is to answer questions like yours.

I have a separate tab in the Excel worksheet that lists all exoplanets that pass one of the three HZ tests - Standard method based on star type, etc.; stellar temperature; Planet equilibrium temperature. They don't always agree, surprisingly.

Here is a reduced list based on star type and that are <100 lyrs. distance. [The last column gives distance in parsecs (pc), as is true for the tables in the prior post.]

As a reminder, a value of 50% means the exoplanet is in the middle of the HZ. 100% is the outer limit, 0% the inner limit. [Also, all percentages are based on the width of the HZ, not the distance to the star.]



As you may notice, the exoplanets' radii are absent, so these are more candidates than we might wish. [I have not compared these to the huge NASA, more comprehensive, database, but I doubt it would have radii and the euro site not have radii.]

BTW, are these thumbnails working properly for you?

 

[Catastrophe]

Yes, they magnify up. Bit small for my ageing eyes, but perfectly legible.

Even 1 parsec is pushing it. Round about 7 years communication unit, back and forth.

Cat

 

[Helio]

Yes, they magnify up. Bit small for my ageing eyes, but perfectly legible.

Even 1 parsec is pushing it. Round about 7 years communication unit, back and forth.

Yep. Relay's won't help. Radio is as slow as smoke signals.

Entanglement seems to offer hope, if one is optimistic that they can overcome its current shortcomings.

 

[Helio]

Yes, they magnify up. Bit small for my ageing eyes, but perfectly legible.

If needed, you can click on the "Download" button located just above the image. Your "Download" tab will have it and you can enlarge this image easily. The quality seems to be more than adequate, at least for data info.

 

[Catastrophe]

Helio, It looks easy to me, if I have understood the table correctly.

I have not considered anything around 10 parsecs, which leaves only M type.

I have provisionally discounted low temperatures, as we are looking for solid, liquid and gaseous water simultaneously somewhere on the surface. I am not sure how the stated temperature would work with this condition.

That leaves only Ross 128b -7° (3.38 parsecs 11 LY) and Wolf 1061c +1°C. (4.29 parsecs 14 LY ).

Please correct me if I have misunderstood anything, but it seems to me very unlikely that any communication would be likely between Earth and either of these planets. 22 and 28 year turnaround communications seem very long to actually happen. That would assume simultaneity of relatively advanced civilisations.

What do you think?

Cat

 

[Helio]

I have provisionally discounted low temperatures, as we are looking for solid, liquid and gaseous water simultaneously somewhere on the surface. I am not sure how the stated temperature would work with this condition.

The "equilibrium temperature" is different than average surface temperature. The approach seems to be that atmospheres are very likely for exhibiting life, thus they would serve to hold heat.

The Teq. range for HZ exosplanets is 175K to 270K. [Earth has a Teq. of 255K, but I think, the surf. temp. avg. is around 288K. Correct me if I'm wrong because I'm unsure.]

Please correct me if I have misunderstood anything, but it seems to me very unlikely that any communication would be likely between Earth and either of these planets. 22 and 28 year turnaround communications seem very long to actually happen. That would assume simultaneity of relatively advanced civilisations.

Yes.

However, I think we still have selection bias. The discoveries we have today may just be the "low-hanging fruit" discoveries. M-type stars are more numerous but harder to see, so we see significant data for the close ones.

The G-type is the leader in HZ exoplanets, but since they are much brighter, why don't we have some of these much closer?

The story is unfolding a little at a time and it's wonderful that we get to witness this.

 

[Catastrophe]

Helio, i greatly respect all your work in this area and thank you for your helpful comments. It is all your data, and I would greatly appreciate your assistance. You are in a much better position than I, to understand how your data interacts with the question I am asking. I don't think this is controversial. In this neutral context, I would greatly appreciative it, if you would lend your expertise in using your data to help general understanding in the matter of the possibility/improbability of extra terrestrial communication by EM means.

Location (distance from Earth) is paramount in evaluating time intervals possible in communicating at speed c.

Cat

 

[Helio]

I'm happy to crunch the data for anyone who would like to see results from specific requirements.

As for communication, if we can't convert science fiction FTL to working models, I assume we will be stuck with whatever HZ exoplanets we find, regardless of distance. Of course, the probes will go to the closer ones first, but if nothing is found, we will have no choice but to hunt further and farther. [That line might serve to explain further how the word farther is used properly. ]

I think it will be likely that all future travelers will go autonomously, unfortunately.

 

[Catastrophe]

In my estimates, I have not included the time taken for either party to recognise and decode the actual 'communications'. Learning a mutual language would take time - more time than looking at two stick figures and learning to count from 1 to 10.

Cat

 

[Helio]

In my estimates, I have not included the time taken for either party to recognise and decode the actual 'communications'. Learning a mutual language would take time - more time than looking at two stick figures and learning to count from 1 to 10.

That certainly could be true, especially if culture plays a dominant role. I would expect, however, a civilization with the ability to communicate with us would be able to send enough information to get us moving quickly in understanding the basics to their language. I'm no linguist, however.

 

[Catastrophe]

Helio, "Of course, the probes will go to the closer ones first"

Leaving out science fiction, as you say, we can only be interested (given the choice) in closer planets. Communication with greater than 50 year turnaround is not going to be very productive. And, don't forget, it will take time for mutual understanding of language to develop. It will take more than "little Alfred sees two apples" for extra terrestrial understanding.


Cat

 

[Helio]

Helio, "Of course, the probes will go to the closer ones first"

Leaving out science fiction, as you say, we can only be interested (given the choice) in closer planets. Communication with greater than 50 year turnaround is not going to be very productive. And, don't forget, it will take time for mutual understanding of language to develop. It will take more than "little Alfred sees two apples" for extra terrestrial understanding.

I would guess that a civilization farther out, say 50 lyrs (100 yrs. turnaround time) that is deemed to be friendly based on limited understanding of their transmissions, would give any travelers, traveling at 0.2c, an additional 87 years to improve communications. But, if they meet half-way, then about 1/2 that time.

 

[Catastrophe]

OK, I don't want to quibble about it, but I seriously doubt motivations, unless it is to the benefit of their offspring, and would they 'sacrifice' their lives on the promise of better communication.
1. Let's just take 0.2c with zero acceleration and zero stopping time, for the sake of easy calculation.
2. Likewise, take 50 LY separation. If they each travel halfway, viz., 25 LY each at 0.2c, then it takes each distance/speed = (LY)/(LY/year) = year, or 25/0.2 = 125 years. They could each meet half way after 125 year travel, not counting acceleration and slowing down. Probably by the time 0.2c travel is possible, life expectancy might be 200 years or more, or they might have developed suspended animation.
3. If only one travelled half way, one travels 25 LY at -.2c taking 125 years, after which they are 25 LY and communication takes 25 years each way.

I have not taken relativistic effects into account, but have offset these against acceleration and slowing down. I don't know how these compare but this is your forte.

This is probably where our results differ?

Cat

 

[Helio]

0.2c, coincidentally, gives about a 2% (0.2) time reduction. [1-(0.2)^2]^1/2

W/o time dilation, 50 Lyrs. would take 250 years to reach @ 0.2c; 245 years with dilation. [I rushed me calculation earlier.]

So, that seems too distant to attempt.

I still hold to the view that such travel times are foolish to attempt since if tech. improves only a few percent increasing speed, then our travelers will, regrettably, find themselves in the slow lane, wasting years.

But, I enjoy thinking of star travels, regardless.

Unfortunately, speeds >0.9c are needed to benefit from SR, but beyond science by, well, light years.

iPhone

 

[Catastrophe]

Sounds like we have the familiar SF theme of voyagers being overtaken by later travellers.

 

[RM Lautner]

Does anyone here know of some kind of periodically updated top list of exoplanets based on their likelihood to be suitable candidates for human colonization based on the limited info we have at any given moment?

 

[Helio]

Does anyone here know of some kind of periodically updated top list of exoplanets based on their likelihood to be suitable candidates for human colonization based on the limited info we have at any given moment?

Post #51 should reveal the most likely candidates. Feel free to ask any questions about that list.

The JWST will do more with atmospheres, which will give us a much better idea for life signs.

 

[rod]

FYI, this report was popular on space.com recently showing the top 10 potential earth-like exoplanets.

The 10 most Earth-like exoplanets, https://www.space.com/30172-six-most-earth-like-alien-planets.html

Presently the exoplanet site Helio and I use shows 5059 confirmed exoplanets. 4086 show periods <=370 days and that is a bunch here. 2344 show radii <= 3.0 earth radii size.

 

[Catastrophe]

Would this help? ≤

Cat

 

[Catastrophe]

FYI, this report was popular on space.com recently showing the top 10 potential earth-like exoplanets.

The 10 most Earth-like exoplanets, https://www.space.com/30172-six-most-earth-like-alien-planets.html

Presently the exoplanet site Helio and I use shows 5059 confirmed exoplanets. 4086 show periods <=370 days and that is a bunch here. 2344 show radii <= 3.0 earth radii size.

Thanks, Rod, but apart from Prox. C. b, they all seem too far away for any (even single) communication in one lifetime.

Cat

 

[Helio]

FYI, this report was popular on space.com recently showing the top 10 potential earth-like exoplanets.

The 10 most Earth-like exoplanets, https://www.space.com/30172-six-most-earth-like-alien-planets.html

Presently the exoplanet site Helio and I use shows 5059 confirmed exoplanets. 4086 show periods <=370 days and that is a bunch here. 2344 show radii <= 3.0 earth radii size.

The following are those 10 exoplanets from the Space.com article in January. A few aren't all that promising, IMO.

 

[Helio]

I think Post #51 still gives the best shot, so far. There are only 8 exoplanets shown for the radii limits shown.

The program, for better or worse, ignores the equilibrium temperature in determining if the exoplanet is in the HZ. Instead, it looks at the results from the standard method and the temperature method, as shown. There are number, perhaps 10 or more, that could be added if any one of the three methods are used. I'm reluctant since the equilibrium temperature is very dependent on atmospheres to hold temp. Any advice is welcome.

 

[Catastrophe]

Helio, apologies if I am missing something, but I cannot see distance from Earth. My interest is possibility of communication, which is partly based on the time factor (2c turnaround of messages) . . . . . . but also, of course, on durability of possible civilisations (= temporal coincidence).


Cat