Exoplanet Summary

[Helio]

I've developed a more comprehensive Excel program (VBA) to categorize all the exoplanets by stellar types. We are just short of 5000 known exoplanets, and it won't be that long we'll be at 10k.

The only requirement for a user is to cut and paste the data from the catalog at exoplanet.eu. Once done, only the "Run" button needs to be clicked. [Of course, Users can change the parameters shown in the green highlight in column A.]

The program allows the user to increase or decrease the HZ to help with the benefits from atmospheres, for instance. It also allows the User to set the exoplanet mass range to count these separately, also by stellar type.

Not shown are the actual planets listed for each stellar class. These have their own tabs, which means any normal Excel sorting, etc. can be performed by stellar class.

Here are the latest results:

 

[Helio]

I should mention that the table shows the use of two separate HZ determination methods: the classical method (as I call it) and the temp./radius method.

The HZ is all about the star's luminosity. The hotter the star the farther out is the HZ, and broader, IIRC. The classic method requires the visual magnitude, stellar distance and star type in order to calculate luminosity. [A bolometric correction factor is required but that's a simple step.]

The temperature-radius method is very simple. Luminosity is a function of temperature to the 4th power, as well as, to the square of radius. L = (T/5777K)^4 * (R/Rsun)^2.

The "Duplicate" column reveals that in many cases both methods agree that the exoplanet is in the HZ. The hotter stars often produce better results when comparing both methods. M-type can vary dramatically, however.

 

[rod]

Helio, I use these sites for exoplanet studies. The Extrasolar Planets Encyclopaedia (exoplanet.eu), currently 4911 shown. Using 250 K to 350 K surface temperatures calculated/measured, I find 56 exoplanets in that range (possible liquid water range). I also use this NASA site, NASA Exoplanet Archive (caltech.edu), 4884 exoplanets shown. 144 show temperature properties in the 250 K to 350 K range.

Your approach listed 112 in the HZ. Good work Helio Showing these are truly habitable exoplanets with liquid water is another story

 

[Dratonia]

Helio, Just out of curiosity, where do you get your data for this? Do they show it on the NASA website?

 

[Helio]

Helio, I use these sites for exoplanet studies. The Extrasolar Planets Encyclopaedia (exoplanet.eu), currently 4911 shown. Using 250 K to 350 K surface temperatures calculated/measured, I find 56 exoplanets in that range (possible liquid water range). I also use this NASA site, NASA Exoplanet Archive (caltech.edu), 4884 exoplanets shown. 144 show temperature properties in the 250 K to 350 K range.

It's all about luminosity, at least for now. Once the luminosity is known then temperature can be determined for a given orbital distance. Of course, knowing the temperature cuts to the chase.

But it appears to me the more common approach is to simply use luminosity and follow the simple HZ limits of:

Inner limit = (L/1.1)^0.5
Outer limit = (L/0.53)^0.5

Having reached this level of coding -- I am an amateur at this as well, admittedly -- I am confident that I can address the more subtle issues. For instance, an eccentricity of, say 0.8, will likely put the planet into a deep freeze, according to one paper I've read. This should shrink the inner and outer limits.

Then there are those M-class stars that produce more in the NIR than othewise. Since, water absorbs red light more than the normal colors, the outer limit may be a little higher for these. But nailing down the HZ for the cooler M-class stars seems very difficult. I've yet to find the BC value for these that converts the visible magintude to bolometric. [I extrapolated from the main list rather than search hard. ]

The negative to the above is that liquid water may be more common, life may be even less likely with little blue and UV. Time will tell.

Your approach listed 112 in the HZ. Good work Helio Showing these are truly habitable exoplanets with liquid water is another story

Thanks! The more likley HZ exoplanets will be where both luminosity methods match, which is the duplicate list showing 40 so far.

The ~ 350 non-classified star systems with exos may still be useable if I spend more time on it and tickle the data to get to a reasonably accurate luminosity.

 

[Helio]

Any suggestions for advancements?

I likley will look at planet radii. There is a mystery as to why exoplanet radii suddenly drop off between 1.5x and 2x that of Earth. This is called the Fulton Gap. I can address this and perhaps do a graph as well. May this gap will grow over time - up or down.

 

[Helio]

Helio, Just out of curiosity, where do you get your data for this? Do they show it on the NASA website?

Rod has noted the two websites that host the catalog for exoplanets. I don't know which might be the better of the two. The NASA site, however, only seems to interactive, whereas the European site allows downloads for Excel. This makes it a snap in getter the data and processing it.