How do ships in the BSG universe calculate their position in the galaxy?

Question

In the BSG universe, the Colonials seems to struggle quite a lot to be able to determine their position in the galaxy.

In the episode Scattered of the new series, it takes 20 minutes for the Galactica to check it's position and thus be able to compute new jump coordinates.

In the pilot of the new series, it is said that jumping beyond the Red Line is dangerous because they cannot accurately plot the jump coordinates thus risk jumping into another spatial object and be destroyed.

What method do they use to check their position in the galaxy, whether before or after every jump?

Answer 1

I would only presume that they have a system for triangulating stars and other landmark galactic features (clusters nebulae, pulsars, quasars etc)

I would imagine it takes significant processor time to calculate, given that computers on galactica are not networked.

In real world physics, I would guess this would also need each star's position corrected for gravitational lensing from other large bodies in the galaxy, which would strain the computers further, as well as their continual motion.

With a GPS, if the GPS already has some idea where it is, and where it expects the satellites to be it will tend to get a good position fix faster - so I would guess that if you jumped galactica to your intended destination, you would likely already have a computed model for star locations and would get your position fix fairly fast - but if you didn't end up where you thought you were - then the task of getting a fix will take longer.

Its the same if you look at a street directory (remember those?) if you basically already know were you are, you will find your location much faster than if you have no idea.

"It aint like dustin' crops boy, without precise calculations we could fly right through a star or bounce too close to a supernova and that'd end your trip real quick, wouldn't it?"

Answer 2

Interstellar space is transparent. Very, very, very, very transparent. That means that you can see objects that are unimaginably far away, if they are intrinsically very luminous.

If you look up at the stars at night, they all seem to be on a two dimensional surface, and thus all at the same distance from Earth. But it is quite possible for one star to be tens, hundreds, or thousands of times as far away as the star that appears closest to it in the sky.

Astronomers invented techniques to measure very, very small angles. With those techniques they could measure the differences in the directions to a star when Earth was on opposite sides of its orbit around the Sun. Even the largest such differences in angle, for the closest stars, are less than one second of arc, or less than 1/1,296,000 (0.0000007) of a full circle.

With those techniques the distances to three stars were measured before 1840, over 179 years ago. And techniques for measuring the distances to stars have been improving all the time. See the Gaia space observatory.

https://en.wikipedia.org/wiki/Gaia_(spacecraft)1

Gaia orbits near the L2 Lagrangian point of Earth's orbit and thus slightly more than 1 Astronomical Unit (AU) from the Sun, since earth's average distance from the Sun is one AU. Thus it has a baseline for making its measurments that is a little more than 2 AU.

A parsec is defined as 206,264.81 AU. Therefore a distance of one parsec is 103,132.4 times the baseline of an observatory on Earth measuring the angles to stars at opposite sides of Earth's orbit.

If a Gaia-like observatory near Earth and Gaia-like observatory exactly 1 parsec away measure the angle to the same star at the same time, the differences in the angles would be 103,132.4 times larger than if both observations were made at opposite ends of Earth's orbit. Therefore the distance measurements could easily be 100,000 times as precise, or objects 100,000 times as far away could be observed with equal precision. The nearest star to Earth, Alpha Centauri C, is farther away than one parsec, 1.3 parsecs to be precise.

Therefore, if a faster than light (FTL) drive, or a method of instantly jumping from position to position, is ever invented, all interstellar expeditions will carry robotic observatories many times more advanced than Gaia, and leave one in every star system they explore.

Thus the Humans and the Cylons in Battlestar Galactica should have both established interstellar networks of super-Gaia observatories long before the series begins and should have already mapped the positions of 99.99 percent of all the stars in their galaxy.

So when a spaceship jumps to a new position in space it should be able to quickly locate objects that are very bright in various bands of the electromagnetic spectrum.

It will identify some of them as very distant galaxies and quasars billions of light years away, and should be able to quickly see that it is still within a hundred million or so light years of where it jumped from by measuring the angles to them.

It will identify some of the bright sources as galaxies and clusters of galaxies that are "only" millions of light years away, and so should quickly determine that it is still in its original galaxy by measuring the angles to them.

The next step is to identify some of the globular clusters in its galaxy and narrow down its region of space by measuring the angles to them.

And so on and so on. The astrogators on the ship can quickly narrow down its position more and more by identifying closer and closer bright objects like super giant stars, giant stars, bright nebulae, and open star clusters. Eventually they will be measuring the angles to nearby stars of ordinary brightness to find the ships's precise location.

You might want to look at answers, including mine, to this question:

https://worldbuilding.stackexchange.com/questions/120255/how-can-i-know-where-to-point-my-spaceship/120278#1202782

And this one:

https://worldbuilding.stackexchange.com/questions/123371/how-can-i-locate-myself-in-a-random-point-of-space/123429#1234293

And:

https://worldbuilding.stackexchange.com/questions/122461/can-my-spaceship-figure-out-its-position-using-cepheid-variables/122492#1224924

And:

https://worldbuilding.stackexchange.com/questions/120295/how-to-find-earths-relative-position-anywhere-in-the-galaxy-without-any-markers/120391#1203915

And:

In Star Trek Discovery why can't Saru triangulate their position from the stars?6