The Astronomy Thread

[Ithekro]

The suggestion was that the Loroi explorers found a lot of dead worlds in the direction of Earth and stopped looking in that direction.

[jterlecki]

I reckon there would be less of a need for 'sufficiently advanced' exoplanetary observation techniques once you have mastered FTL travel...
Simply sent a survey vessel instead of watching old photons.

Depending on costs - maybe even something unmanned could do

[Gudo]

If I recall correctly, the Earth has the distinct feat if being 'louder' than the Sun in the RF spectrum.

In some frequencies, but not others. If I recall correctly, the gas giants are also "louder" than either the sun or the Earth in some frequencies as well. It's related to the way that charge particles from the sun interact with planetary ionospheres, but it's been a very long time since I read that literature. Suffice to say, amplitude of RF emissions alone are not sufficient to reveal the existence of intelligent life. Loud but very regular emissions probably indicate natural phenomenon like pulsars. The frequency matters as well, since some are more likely than others to be used by intelligent life. So the best bet to find Earth from RF emissions would be to search for irregular transmissions in the watering hole. Since Loroi planets presumably have a significant amount of atmospheric water, that would be a natural frequency band for the Union and Hierarchy to search as well, if only to look for more Loroi splinter colonies. Who knows, a search in that band might be how they found the Pipolsid.

Other species might have been aware of the existence of Earth without necessarily knowing about humanity, especially if they observed our world before the 1900s.

Yes, I contend that all major powers would be aware that the planet exists, as well as it's mass and orbit. A while back, there was discussion related to page 107 that concluded that the Loroi would likely be able to pinpoint which planet is Earth given only the rough direction and orbital period.

I reckon there would be less of a need for 'sufficiently advanced' exoplanetary observation techniques once you have mastered FTL travel...
Simply sent a survey vessel instead of watching old photons.

Old photons would probably be your best way of deciding where to send those survey vessels. It would be prohibitively expensive to send a ship to each system especially considering the need to refuel and resupply. You'd want to chose the targets from the systems with planets that most resemble what you're looking for. In the Loroi's case, they'd want atmospheric oxygen and water, as well as suitable gravity and surface temperatures, all things that we are able to detect on exoplanets with current technology. Given the incentives to establish new colonies, locate other splinter colonies, and locate and identify other intelligent species, I see no reason why any species would fail to develop more advanced exoplanet detection techniques than we currently possess.

The suggestion was that the Loroi explorers found a lot of dead worlds in the direction of Earth and stopped looking in that direction.

Maybe, but the cost of making observations is so low as to be a rounding error in a modern nation's budget. Where was this suggestion made?

Depending on costs - maybe even something unmanned could do

Range is likely a limiting factor, even for unmanned systems. Fuel in Outsider is neither free nor limitless.

[Ithekro]

Page 118 its said the Sol System is beyond the "Empty Quarter". No one goes out there. It is not well surveyed. The star doesn't appear on Loroi charts. It is a "fainter star" after all.

[Gudo]

Seems I stand corrected then. Not sure how I missed that. Considering the state of exoplanet discovery today though, if I were Mr. Jardin my first reaction would be:

I mean, 200 LY really doesn't seem like that far, and Sol isn't particularly dim.

[Krulle]

Even automated star observation systems at their tech levels should have catalogued Sol and Earth.

An issue may be a larger distance between stars, making the jumps from star to star more expensive.


You need to jump "higher", which I presume costs a lot more energy.


Oh, and you need to know quite a low about the relative movements of your and the target's star, to properly predict where the gravity well is now (because the old photons will only tell you where it was n years ago).
And that may result in a larger hyperspace jump fail percentage.

That may be the reason why active exploration in that direction has been halted, besides the costs during an extermination defence war.
And the Loroi were also busy with themselves before that. All that internal strife makes it difficult to focus on external topics.

And nobody is looking at the results of any automated star observation systems, as long as they don't suddenly indicate "intelligent LIFE - there!".

[Arioch]

By "surveyed" they mean the star systems visited and orbits charted. The stars themselves are visible from a great distance, especially a G star like Sol.

Unless the plane of the planetary orbits happen to be edge-on and transit the star, I think it would be very hard to deduce the orbits in a large system like Sol by remote observation. The slight wobbles would be pretty hard to pick out amidst the noise of solar activity.

[Mk_C]

Seems I stand corrected then. Not sure how I missed that. Considering the state of exoplanet discovery today though, if I were Mr. Jardin my first reaction would be:

I mean, 200 LY really doesn't seem like that far, and Sol isn't particularly dim.

It can be simply obscured by the shine of several brighter stars when observed from Loroi territory - not even totally, just enough to make it a bother to look into, and thus push it down the list of interest of the Union astrographers.

[GeoModder]

I reckon there would be less of a need for 'sufficiently advanced' exoplanetary observation techniques once you have mastered FTL travel...
Simply sent a survey vessel instead of watching old photons.

Old photons would probably be your best way of deciding where to send those survey vessels. It would be prohibitively expensive to send a ship to each system especially considering the need to refuel and resupply. You'd want to chose the targets from the systems with planets that most resemble what you're looking for. In the Loroi's case, they'd want atmospheric oxygen and water, as well as suitable gravity and surface temperatures, all things that we are able to detect on exoplanets with current technology. Given the incentives to establish new colonies, locate other splinter colonies, and locate and identify other intelligent species, I see no reason why any species would fail to develop more advanced exoplanet detection techniques than we currently possess.

Due to the nature of FTL travel in Outsider, the expense is there as a matter of fact. A vessel needs to jump from system to system in order to reach a high-lighted star for closer scrutiny.
As far as I can discern from the Insider, the Scout Corps surveys each and every star within reach, whether or not some telescopic survey marks this-or-that star as interesting. The only thing such an observation program can add is offer possible priority targets.
The Loroi have it even easier. Their Farseers can detect alien minds over interstellar distances. That's a sure tell-tale of an inhabitable planet, though appearances can be misleading as seen with Golim-chei.

[Gudo]

By "surveyed" they mean the star systems visited and orbits charted. The stars themselves are visible from a great distance, especially a G star like Sol.

That makes way more sense.

Unless the plane of the planetary orbits happen to be edge-on and transit the star, I think it would be very hard to deduce the orbits in a large system like Sol by remote observation. The slight wobbles would be pretty hard to pick out amidst the noise of solar activity.

We've already used a number of techniques to locate exoplanets, many don't relay on the transit of said planet in front of it's star. Looks like the wiki lists 16 methods that have found planets and another 6 that are plausible. It doesn't really matter much in this case I think, since Alexander is simply going to point out the star and planet for them. I assume he'd also give them enough information about the system (number of planets, major moons, etc) that Union astronomers could piece together a fairly accurate map of the system. Still, the Loroi have had access to space based telescopes and vantages from multiple stellar systems for well over 1000 years by now.

Due to the nature of FTL travel in Outsider, the expense is there as a matter of fact. A vessel needs to jump from system to system in order to reach a high-lighted star for closer scrutiny.... The only thing such an observation program can add is offer possible priority targets.

You're 100% correct that you'd get a "free" opportunity to survey each system en-route to a point of interest. But I don't think the Terrans would've been in the habit of visiting absolutely everything, at least not until they contacted the Orgus. Unless a system was en-route to a potentially habitable planet, I can't see the justification for pre-contact Terrans to visit. They only thing an uninhabitable system could provide would be raw resources and there should still be plenty in Terran space. The TCA would probably have plenty of other budgetary priorities and might have a hard time justifying a physical survey unless they could point to a possible colony site and say "This expedition will enable us to colonize this location."

As far as I can discern from the Insider, the Scout Corps surveys each and every star within reach, whether or not some telescopic survey marks this-or-that star as interesting.

I wonder how much of the justification for the "physically visit each system" approach is due to the TCA's need for detailed maps for military purposes. It would be interesting to compare the pre and post Orgus contact survey practices.

[Arioch]

We've already used a number of techniques to locate exoplanets, many don't relay on the transit of said planet in front of it's star. Looks like the wiki lists 16 methods that have found planets and another 6 that are plausible.

The majority of the methods listed are only available in rare, exotic cases, like when the primary is a neutron star, or the primary transits a background star. There are really only three methods that have produced a decent number of planet detections: transit, radial velocity, and direct imaging. But even these three methods only work in specific situations, and none of them maps out a whole system.

Transit has been the most successful, but it can only be used on a tiny fraction of stars, because the orbital plane of the planets has to be exactly lined up with your line of sight. Even then, transit will only detect the innermost planets which orbit quickly and in the same plane. Beyond a few AU, even the slightest orbital inclination will mean the planet doesn't transit the star, and even if it does, the longer orbital periods will require decades of observation to observe. Union space is well above the Sun's ecliptic plane, so they will not observe any transits from Union space.

Direct imaging only works for detecting very large planets that are very far away from the primary. The smallest exoplanet detected by direct imaging is twice the mass of Jupiter and twice as far out. At best, ultra-tech astronomy might be able to directly image Jupiter and some of the outer gas giants.

Radial velocity is really the only method Union observers could use to remotely map the Sol system; this measures the Doppler shift of the primary's spectrum caused by the wobble induced by the planets. We have only used this method to detect planets that are very massive and/or orbit very close to their primary. In theory, sufficiently precise spectrum measurements can reveal an entire planetary system, but noise from stellar activity puts a maximum limit on how accurate those measurements can be, and you have to observe the system for several complete orbital cycles, which take hundreds of years. And even when successful, the detection only tells you the mass and orbital period of the planet; nothing about its diameter or composition.

[GeoModder]

Due to the nature of FTL travel in Outsider, the expense is there as a matter of fact. A vessel needs to jump from system to system in order to reach a high-lighted star for closer scrutiny.... The only thing such an observation program can add is offer possible priority targets.

You're 100% correct that you'd get a "free" opportunity to survey each system en-route to a point of interest. But I don't think the Terrans would've been in the habit of visiting absolutely everything, at least not until they contacted the Orgus. Unless a system was en-route to a potentially habitable planet, I can't see the justification for pre-contact Terrans to visit. They only thing an uninhabitable system could provide would be raw resources and there should still be plenty in Terran space. The TCA would probably have plenty of other budgetary priorities and might have a hard time justifying a physical survey unless they could point to a possible colony site and say "This expedition will enable us to colonize this location."

Why not? In Outsider humanity has had the capability for interstellar travel for almost 3 generations, and still they've only gone as far out as Aldebaran as indicated in the Local Bubble map. And our ensign seems to mark human territory within the region around Arcturus, Vega, and Sirius. There's not too many stars within that area to make it impossible to visit in that timespan. For a fair number of star systems within this region scientific curiosity alone warrant closer scrutiny.

[Bamax]

Due to the nature of FTL travel in Outsider, the expense is there as a matter of fact. A vessel needs to jump from system to system in order to reach a high-lighted star for closer scrutiny.... The only thing such an observation program can add is offer possible priority targets.

You're 100% correct that you'd get a "free" opportunity to survey each system en-route to a point of interest. But I don't think the Terrans would've been in the habit of visiting absolutely everything, at least not until they contacted the Orgus. Unless a system was en-route to a potentially habitable planet, I can't see the justification for pre-contact Terrans to visit. They only thing an uninhabitable system could provide would be raw resources and there should still be plenty in Terran space. The TCA would probably have plenty of other budgetary priorities and might have a hard time justifying a physical survey unless they could point to a possible colony site and say "This expedition will enable us to colonize this location."

Why not? In Outsider humanity has had the capability for interstellar travel for almost 3 generations, and still they've only gone as far out as Aldebaran as indicated in the Local Bubble map. And our ensign seems to mark human territory within the region around Arcturus, Vega, and Sirius. There's not too many stars within that area to make it impossible to visit in that timespan. For a fair number of star systems within this region scientific curiosity alone warrant closer scrutiny.

A valid point.

I cannot argue with you that yes, if technologically new to space Earth can enter Loroi occupied space, the Loroi could easily do likewise.

The best reason I think Arioch could possibly give is one word....make it two....UMIAKS MAN!

Earth is so far away that am sure the Loroi would not have brought any attention to it until the war reached it.

Fortunately Alex reached them first.

Bottom line is the Loroi only want to take worlds right now so the Umiak cannot add their resources to their arsenal, even of that means genocide.

[Gudo]

The majority of the methods listed are only available in rare, exotic cases, like when the primary is a neutron star, or the primary transits a background star. There are really only three methods that have produced a decent number of planet detections: transit, radial velocity, and direct imaging. But even these three methods only work in specific situations, and none of them maps out a whole system.

Valid criticism, but my point was more to the effect that we've only been seriously searching for two decades and we've already developed a number of techniques. At a higher tech level, I'm sure we'll develop more which may have potential. A grand unified theory or a better understanding of dark matter or dark energy might unlock quite a few doors. Who knows, maybe gravitational wave observatories like LIGO could be useful (if the lasers, mirrors, and detectors were put on asteroids or orbital platforms, such an observatory could be made truly massive with only a minimal investment in actual material.)

Transit has been the most successful, but it can only be used on a tiny fraction of stars... Union space is well above the Sun's ecliptic plane, so they will not observe any transits...

That's good to know, I was having a hard time figuring out what planes things were in relative to each other.

Radial velocity is really the only method Union observers could use to remotely map the Sol system... In theory, sufficiently precise spectrum measurements can reveal an entire planetary system, but noise from stellar activity puts a maximum limit on how accurate those measurements can be, and you have to observe the system for several complete orbital cycles, which take hundreds of years.

The Loroi alone have (had the ability to make) over a millennium and a half of observations, and from multiple systems. Intelligence sharing agreements are surely part of Union membership, so there's also observations by the Neridi, Barsam, Pipolsid, and all the rest that can be consolidated. Comparing many observations, taken over multiple centuries and from multiple vantage points, could cut down a significant amount of noise. Presumably both the Union and Hierarchy have conducted a program of comparing observations made by their various member spices, if only to give some Pipolsid PhD student something to do.

[EDIT]I'm not trying to argue that there's some compelling reason the Union must have discovered Earth, let alone everything there is to know about it. Only that it's plausible the Union has already identified that a planet exists in Earth's position given the detection techniques already available to a TL8 civ and the sheer volume of observations the Union has access to. My personal feeling is that it's sufficiently plausible that I expect the Union to have already identified the mass and orbit of the planet, but again I have no reason to argue that must be the case. If it turns out the Union hasn't cataloged the planet, I would consider it to be unexpected, but not anything like a plot hole or something.[/EDIT]

And even when successful, the detection only tells you the mass and orbital period of the planet; nothing about its diameter or composition.

It should also tell you the distance from the star. But like I said in an earlier post, it's likely the Union does not have much more information than that, as otherwise the planet would be too interesting.

Why not? In Outsider humanity has had the capability for interstellar travel for almost 3 generations, and still they've only gone as far out as Aldebaran as indicated in the Local Bubble map. And our ensign seems to mark human territory within the region around Arcturus, Vega, and Sirius. There's not too many stars within that area to make it impossible to visit in that timespan. For a fair number of star systems within this region scientific curiosity alone warrant closer scrutiny.

I feel like this is getting a little out of the astronomy lane and more into theoretical economics of a fictional nation. I don't think we have a way of gauging if going out "only" as far as Aldebaran represents an ambitious scouting program, or a conservative one. We don't really have a good way of considering the costs, especially the opportunity costs of the program. I think we can all agree: the ability to send survey ships (autonomous or not) reduces the need for, and therefore value of, especially advanced exoplanet detection techniques; there's no reason to not use both survey ships and observatories in tandem; and astronomical observations can be used to guide a survey program.

[spacewhale]

Consider nations on Earth that had the technological capability to potentially explore the rest of the planet for centuries, but due to various political reasons they did not, like Zheng He and the treasure fleet. With a series of wars with your immediate neighbors, I can't imagine there was much drive to sail across the galactic Pacific to find Earthlings.

[GeoModder]

Consider nations on Earth that had the technological capability to potentially explore the rest of the planet for centuries, but due to various political reasons they did not, like Zheng He and the treasure fleet. With a series of wars with your immediate neighbors, I can't imagine there was much drive to sail across the galactic Pacific to find Earthlings.

During the Age of Sail in Europe, there was almost always some war between the European naval powers going on (France, England, Spain, the United Provinces,...). That didn't stop trade or discovery travels to be made to all possible corners of the Earth.

Why not? In Outsider humanity has had the capability for interstellar travel for almost 3 generations, and still they've only gone as far out as Aldebaran as indicated in the Local Bubble map. And our ensign seems to mark human territory within the region around Arcturus, Vega, and Sirius. There's not too many stars within that area to make it impossible to visit in that timespan. For a fair number of star systems within this region scientific curiosity alone warrant closer scrutiny.

I feel like this is getting a little out of the astronomy lane and more into theoretical economics of a fictional nation. I don't think we have a way of gauging if going out "only" as far as Aldebaran represents an ambitious scouting program, or a conservative one. We don't really have a good way of considering the costs, especially the opportunity costs of the program. I think we can all agree: the ability to send survey ships (autonomous or not) reduces the need for, and therefore value of, especially advanced exoplanet detection techniques; there's no reason to not use both survey ships and observatories in tandem; and astronomical observations can be used to guide a survey program.

I was only taking the amount of time in account. 70+ years of interstellar capability. At most several hundred stars within say a 10 parsecs radius.
And no doubt an urge to find shiny new things by the nations of Earth with interstellar capability in the late 21st century, and the TCA afterwards at the onset of the 22nd century.
Say that perhaps half a dozen ships are capable of traveling and jumping towards 40 star systems/year, and return.
Its something the Scout Corps is doing in the comic right now.

[spacewhale]

During the Age of Sail in Europe, there was almost always some war between the European naval powers going on (France, England, Spain, the United Provinces,...). That didn't stop trade or discovery travels to be made to all possible corners of the Earth.

Sure, but I'm just pointing out that Zheng He's voyages could have easily done the same, they didn't. Just because you *can* do something doesn't mean you will do something.

[GeoModder]

Of course not. And there were a number of European nations at the time who didn't sail out and colonize far-out regions. But most did, even as early as the 10th millennium if Norse Edda's are to be believed.

[gaerzi]

I reckon there would be less of a need for 'sufficiently advanced' exoplanetary observation techniques once you have mastered FTL travel...
Simply sent a survey vessel instead of watching old photons.

Problem is that you can't go very far with this method because there's only so much hyperfuel your ship can carry. So you need to be able to refuel at some point, and when you're going through a patch of useless empty systems, at some point you cannot go further beyond without organizing the hyperspace equivalent of the Black Buck Raid.

Which is what the Scout Corp did. The Bellarmine was supposed to jump back to refuel from a tanker ship.

[GeoModder]

Which is what the Scout Corp did. The Bellarmine was supposed to jump back to refuel from a tanker ship.

You said it yourself.
So a dedicated Scout Transport of the L'Amour class could well be capable of traveling to the edge of the Local Bubble, and back.
Which reminds me. In the comic Alex mentions their tanker vessel is '10 jumps back'. That gives us a minimum of 20 jumps between refueling. That doesn't sound like a Bennett-class scout isn't capable of traveling the region between Vega, Aldebaran, and Sirius, on its own.