How many stars and planets could be catalogued within 100 parsecs by 2100?

[chasrob]

I'm working on a story that takes place in the 22nd century. Is it reasonable to assume that all stars and planets within 100 parsecs have been found and studied and determined to be habitable (in the case of planets)? Without any means to actually visit each body by FTL starship/probe.

I'm amazed about all the info scientists have gathered as of today, enough so to make that guess.

 

[phinds]

I'm working on a story that takes place in the 22nd century. Is it reasonable to assume that all stars and planets within 100 parsecs have been found and studied and determined to be habitable ... ?

Habitable to what life form?

 

[chasrob]

Habitable to what life form?

Any organism on our planet, I suppose

 

[phinds]

What do you have against other life forms? Do you think Earth is special?

 

[chasrob]

?? Define other life forms.

 

[phinds]

?? Define other life forms.

Any life form that is not native to Earth

 

[chasrob]

There is any life form that's non-native?

 

[phinds]

There is any life form like that?

The odds are extremely high but so far no evidence.

 

[Drakkith]

I'm working on a story that takes place in the 22nd century. Is it reasonable to assume that all stars and planets within 100 parsecs have been found and studied and determined to be habitable (in the case of planets)? Without any means to actually visit each body by FTL starship/probe.

I'm amazed about all the info scientists have gathered as of today, enough so to make that guess.

Yes, I think it would be reasonable to assume that we would be able to study all stars and their planets within 300 light years within the next 200 years.

 

[member 656954]

Is it reasonable to assume that all stars and planets within 100 parsecs have been found and studied and determined to be habitable (in the case of planets)?

I'm writing a novel where FTL allows expansion and it is incredible how much information we already know, @chasrob, so it is entirely likely everything out to 300 parsecs will be cataloged within 200 years. But you know it's science fiction right? You get to say and nobody this side of 200 years can prove you wrong

It is a lot of stars though. I was going to upload a LibreOffice spreadsheet of just 30LY out - that's as far as my novel goes at the moment - but it's not a supported file type for attachments hence the table below, but if you've not already created one, you'll likely need a tracking sheet as you'll be making up planets and their attributes, and once you get past a few, keeping them all in your head is hard work!

Also, as the list below shows, a lot of stars are red dwarf flares, which complicates habitability. As do the double - and triple - stars, depending on how far apart they are. This list is only close in, I've another couple of tabs going out 50LY (300 parsecs is a lot of systems) that I won't bother to include but it highlights that you'll need to just make stuff up if your story has travel to other suns. Which is fun, but time consuming!

Good luck with the writing

Name of Star​	Local Name​	Light Years​	Stellar class​	Absolute magnitude (higher number is less bright)​	Official Notes http://www.stellar-database.com​
Sun​	​	0​	​	4.85​	​
Proxima Centauri​	Proxima​	4.2441​	Brown Dwarf Flare​	15.53​	​
Alpha Centauri A​	Alpha​	4.365​	Sun like​	4.38​	​
Alpha Centauri B​	Beta​	​	Sun like​	5.71​	​
Barnard's Star​	Barnard​	5.9577​	Red Dwarf Flare​	13.22​	​
Luhman 16A​	​	6.5029​	Brown Dwarf​	14.2​	​
Luhman 16B​	​	​	Brown Dwarf​	​	​
WISE 0855−0714​	Ghandi​	7.26​	Subbrown Dwarf​	25​	One planet, 2 Earth Masses​
Wolf 359​	​	7.856​	Red Dwarf Flare​	16.55​	​
Lalande 21185​	​	8.307​	Red Dwarf​	10.44​	one suspected planet​
Sirius A​	Sirius​	8.659​	A type (hotter than Sun)​	1.42​	​
Sirius B​	Bashful​	​	White Dwarf​	11.34​	​
Luyten 726-8 A​	​	8.791​	Red Dwarf Flare​	15.4​	​
Luyten 726-8 B​	​	​	Red Dwarf Flare​	15.85​	​
Ross 154​	​	9.7035​	Red Dwarf Flare​	13.07​	​
Ross 248​	​	10.2903​	Red Dwarf Flare​	14.79​	​
Epsilon Eridani​	​	10.446​	Bright Dwarf​	6.19​	three circumstellar disks, two suspected planets​
Lacaille 9352​	​	10.7211​	Red Dwarf​	9.75​	​
Ross 128​	​	11.0074​	Red Dwarf Flare​	13.51​	One planet​
EZ Aquarii A​	​	11.109​	Red Dwarf Flare​	15.64​	​
EZ Aquarii B​	​	​	Red Dwarf Flare​	15.58​	​
EZ Aquarii C​	​	​	Red Dwarf​	16.34​	​
61 Cygni A​	​	11.4008​	Red Dwarf​	7.49​	​
61 Cygni B​	​	​	Red Dwarf Flare​	8.31​	Circumstellar disk​
Procyon A​	​	11.402​	White like Sun​	2.66​	​
Procyon B​	​	​	White Dwarf​	12.98​	​
Struve 2398 A​	​	11.488​	Red Dwarf Flare​	11.16​	​
Struve 2398 B​	​	​	Red Dwarf Flare​	11.95​	​
Groombridge 34 A​	​	11.6182​	Red Dwarf Flare​	10.32​	Two suspected planets​
Groombridge 34 B​	​	​	Red Dwarf Flare​	13.3​	​
DX Cancri​	​	11.678​	Red Dwarf Flare​	16.98​	​
Tau Ceti​	​	11.753​	Sun like​	5.68​	One debris disk, two planets, three suspected planets, two refuted planets​
Epsilon Indi A​	​	11.869​	Orange-red Dwarf​	6.89​	one planet​
Epsilon Indi Ba​	​	​	Methane Brown Dwarf​	​	​
Epsilon Indi Bb​	​	​	Methane Brown Dwarf​	​	​
Gilese 1061​	​	11.9803​	Red Dwarf​	15.26​	​
YZ Ceti​	​	12.1084​	Red Dwarf Flare​	14.17​	Three planets, one suspected planet​
Luyten's Star​	​	12.199​	Red Dwarf​	11.97​	Two planets​
Teegarden's Star​	​	12.496​	Red Dwarf​	17.22​	​
SCR 1845-6357 A​	​	12.571​	Red Dwarf​	19.41​	​
SCR 1845-6357 B​	​	​	Brown Dwarf​	​	​
Kapteyn's Star​	​	12.8294​	Red Subdwarf​	10.87​	two suspected planets​
Lacaille 8760​	​	12.9515​	Red Dwarf Flare​	8.69​	​
Kruger 60 A​	​	13.0724​	Red Dwarf​	11.76​	​
Kruger 60 B​	​	​	Red Dwarf Flare​	13.38​	​
DEN 1048-3956​	​	13.1932​	M8.5V[5]​	19.37​	​
Ross 614A​	​	13.424​	Red Dwarf Flare​	13.09​	​
Ross 614B​	​	​	Red Dwarf​	16.17​	​
UGPS J0722-0540​	​	13.43​	Brown Dwarf​	​	One planet​
Wolf 1061​	​	14.0458​	Red Dwarf​	11.93​	three planets​
Wolf 424 A​	​	14.05​	Red Dwarf Flare​	14.97​	​
Wolf 424 B​	​	​	Red Dwarf Flare​	14.96​	​
Van Maanen's star​	​	14.0744​	White Dwarf​	14.21​	Possible debris disk, possible planet​
Gliese 1​	​	14.1725​	Red Dwarf​	10.35​	​
WISE 1639-6847​	​	14.3​	Brown Dwarf​	22.1​	​
L 1159-16​	​	14.5843​	Red Dwarf Flare​	14.03​	​
Gliese 674​	​	14.8387​	Red Dwarf​	11.09​	One planet, Uranus sized​
Gliese 687​	​	14.8401​	Red Dwarf Flare​	10.89​	Super earth, 18 masses​
LHS 292​	​	14.885​	Red Dwarf Flare​	17.32​	​
WISE J0521+1025​	​	16.3​	Brown Dwarf​	16.95​	​
LP 145-141​	​	15.1182​	White Dwarf​	13.18​	​
Gliese 208-44 A​	​	15.209​	Red Dwarf Flare​	15.17​	​
Gliese 208-45​	​	​	Red Dwarf Flare​	15.72​	​
Gliese 208-44 B​	​	​	Red Dwarf Flare​	18.46​	​
Gliese 876​	​	15.2504​	Red Dwarf​	11.81​	four planets, two possible planets​
LHS 288​	​	15.7703​	Red Dwarf​	15.51​	one tentative planet​
Gliese 1002​	​	15.8164​	Red Dwarf​	15.4​	​
Groombridge 1618 (Gliese 380)​	​	15.8797​	Red Dwarf Flare​	8.16​	One suspected debris disk, one suspected planet​
DEN 0255-4700​	​	15.885​	Brown Dwarf​	24.44​	​
Gliese 412 A​	​	15.983​	Red Dwarf​	10.34​	​
Gliese 412 B​	​	​	Red Dwarf Flare​	16.05​	​
Gliese 832​	​	16.1939​	Red Dwarf Flare​	10.2​	Two planets​
AD Leonis​	​	16.197​	Red Dwarf Flare​	10.87​	​
GJ 1005 A​	​	16.26​	Red Dwarf​	​	​
GJ 1005 B​	​	​	Red Dwarf​	​	​

 

[chasrob]

Thanks for the info. I extrapolated info I got from Wikipedia and there are nearly 86,000 stars that are K class and earlier in our 100 parsec volume. And most of them are G and K class, although a lot are multiple systems, no doubt.
So yeah, a whole lotta data in such a catalogue, but I'm sure the computers of ~2100 AD could handle that.

 

[Drakkith]

So yeah, a whole lotta data in such a catalogue, but I'm sure the computers of ~2100 AD could handle that.

Indeed. Even current computers can easily handle this much information.

 

[Vanadium 50]

I'm not so sure. There are about a half million stars in that volume, down to 15th magnitude. Finding small planets close in will be difficult, especially for systems that present an unfavorable aspect ratio to the Earth.

 

[Drakkith]

I'm not so sure. There are about a half million stars in that volume, down to 15th magnitude. Finding small planets close in will be difficult, especially for systems that present an unfavorable aspect ratio to the Earth.

C'mon, you just got to reroute warp power to the sensor array!

 

[member 656954]

So yeah, a whole lotta data in such a catalogue, but I'm sure the computers of ~2100 AD could handle that.

It is more whether you as an author can handle it, @chasrob. If your question was merely a sense check on capabilities 200 years out, then it's an easy 'yes'. But if you're looking to world build with even a few planets, consider how quickly you can be swamped in details that bog down the writing because you are surfing a fact and fiction wave that swallows many research hours.

I think Peter F. Hamilton is the master at describing numerous planets in his novels in detail but without laboring the point. Check out his Commonwealth series as an example, it is stunning in breadth and scope, but also note that he does not generally tie his planets to know stars, giving him considerable leeway to write what he needs.

 

[snorkack]

Currently the more successful ways of planet spotting have been radial velocity (does not give true inclination or radius) and transits (only spot transiting planets). Astrometric planets have been rare.
For nearby stars, astrometry immediately gives true inclination and mass (but not radius). How good is Gaia at spotting astrometric planets?

 

[Vanadium 50]

If you're planning on pointing your telescope at a planet and finding it that way, good luck. You're reaching down to magnitudes of maybe 35. Half a million times.

 

[snorkack]

I realized that Gaia cannot see Earth-sized planets astrometrically. You could derive why.

 

[chasrob]

Gaia Century 22 can see them planets. ;)

 

[member 656954]

Gaia Century 22 can see them planets. ;)

Yep, absolutely the right approach. And eactly what I did for my novel Tyranny. I made it up. Called it the Orbital Refactoring Telescope, and @mfb was kind enough (in another thread) to work out the resolving power vis-a-vis Betelgeuse, which was the topic of observation in the story.

Surely, that's the fun of writing sci-fi, that you can imagine impossible things and craft a story around them!

 

[chasrob]

Anybody remember the Overwhelmingly Large Telescope? Set up on the far side of the Moon, I wonder if it could get photos of an earth-like planet a couple hundred light years away?

 

[mfb]

500 ly * 500 nm / (100 m) = 23 million km. Just at the edge of what you need to resolve e.g. something like Earth as separate from the star (as you need much more than 1 standard deviation to see a 1 in a billion contrast), but orders of magnitude too small to see features on the planet directly. Phase curves can still give some information.

 

[snorkack]

Consider the known methods of remote detection of exoplanets:

1. Transit
2. Radial velocity
3. Astrometry
4. Direct imaging

Note that hot Jupiters, and hot Uranuses, are not interesting because they are not habitable anyway.
Which methods give you a ground truth differentiation between a Venus-like planet, a Mars-like planet and and Earth-like planet?

 

[BillTre]

Moons of large planets can be interesting too.
Titan, Europa, etc.

 

[mfb]

If you're planning on pointing your telescope at a planet and finding it that way, good luck. You're reaching down to magnitudes of maybe 35. Half a million times.

Planets are surprisingly bright. Earth at full illumination has ~10^-9 times the brightness of the Sun, giving it an absolute magnitude of ~25. The absolute magnitude matches the apparent magnitude at a distance of 10 pc = 33 light years. At 10 times the distance we lose 5 in magnitude, so Earth is still a magnitude 30 object at 330 light years. Make it magnitude 32 or so to account for the worst-case phase angle. If you want a planet to be habitable its surface brightness can't be that much lower and the planet cannot be that much smaller either. The peak can be more in the infrared, lowering the magnitude without lowering total emissions, but that is okay. Even Hubble could capture some objects of that magnitude, JWST will go down to magnitude 34. A 22nd century telescope should make these look like toys.
Light collection won't be the limit, angular resolution is. Habitable planets around low-luminosity red dwarfs (if there can be habitable planets) will likely need some space-based interferometer if we don't find them via other methods.

 

[Vanadium 50]

Unless you know a priori that you don't have to check M's, you have to check them. Even if 99.99% of them can't support life, it leaves about 50 in the range. There are also thousands of K's And you need to be able to go down to Europa-sized. So maybe I was wrong with 35 and it's only 34.

 

[mfb]

100 years ago we didn't even know about Pluto, at magnitude ~15. Today we are about to launch a telescope that can find magnitude 34 objects, and LSST will monitor over half of the sky for objects down to magnitude 24-28. If surveys don't reach magnitude 35 or better in the next 100 years something went seriously wrong.

 

[Vanadium 50]

The problem with extrapolating is that if you draw a line between Orville Wright and Neil Armstrong, you don't get where were are today. You get Buck Rogers.

I don't want to say this is impossible, just that there are a number of hurdles one needs to jump over, and need to be considered. I am also going to take the OP's "all" (in italics) literally. To ensure that you get them all, you need to be substantially more sensitive that what you need to get most of them.

Step 1: get all 500,000 stars. We're not there yet. If you plot stellar density vs. distance, it starts falling over at 10 or 15 parsecs. We're missing stars that close. So we need at least a 100 times better threshold, and probably more like 500.

Step 2: see the planets. You only need to go out maybe 100 uradians from each star, so you only need to look at maybe 1/1000 of the sky. That's good. And bad - that's still a lot of sky. About 25,000 Hubble deep fields. (About 1500 years equivalent for the Hubble Deep Field).

Step 3: See the planets move. If you don't want fakes, you need at least 5 shots of each system, and more for systems with many planets. So we're at 7500 Hubble-years. If there's a century between now and the story, and we launch one Hubble per year, we'll just about get it.

Step 4: Pull spectra off all these planets. This is very photon-hungry and you'll have millions of targets. Maybe you could get colors with photometry and eliminate ones where you don't need to do a spectrum, but it's still a lot.

So you have maybe four steps to take and 2 or 3 decades for each step. Possible? Sure. Guaranteed? I don't think so.

 

[mfb]

I didn't take "all" literally. I guess 99.9% would be sufficient.

Step 1: get all 500,000 stars. We're not there yet. If you plot stellar density vs. distance, it starts falling over at 10 or 15 parsecs. We're missing stars that close. So we need at least a 100 times better threshold, and probably more like 500.

Get all stars with a chance to have habitable planets. Proxima Centauri is somewhere at the threshold, some people see it below. Absolute magnitude 15.6, easier to see in the infrared, but let's be really pessimistic and say were are looking for magnitude 18 stars. At 330 light years they have an apparent magnitude of 23. LSST will easily see them. Gaia will get distance estimates for all objects down to magnitude 20.

ELT will have 250 times the light collection of Hubble. A single ELT equivalent in space, operating for 20 years, would give you observation time equivalent to 7500 Hubble years. It wouldn't have the angular resolution needed for most planets, so you probably want a larger interferometer with the same mirror area (or more), but that's the point I mentioned earlier: The resolution is the limit, not the light collection.

Spectra of the planets will be much more difficult. You can limit it to planets in the habitable zone, that excludes various stars.

I don't say it is guaranteed, but it's something we can do with projects we could reasonably work on today. An ELT-like telescope in space isn't that outrageously beyond current technology.

 

[stefan r]

500 ly * 500 nm / (100 m) = 23 million km. Just at the edge of what you need to resolve e.g. something like Earth as separate from the star (as you need much more than 1 standard deviation to see a 1 in a billion contrast), but orders of magnitude too small to see features on the planet directly. Phase curves can still give some information.

With a thriving economy and rapid exploitation of the asteroid belt astronomers should be able to have arrays of telescope lenses and starshades built there. The diameter of the interferometer lens should be around 6 or 7 astronomical units 10¹²m.