New Sci Fi Setting Seeds

[AlexanderHowl]

During the year 2051, astronomers detected a brown dwarf heading on an intercepting trajectory with the Sol System. An intergalactic object, it was traveling at 0.1c, so it was thought to have been ejected from its home galaxy by a supermassive black hole. By 2094, astronomers discovered that the brown dwarf would impact Sol in 2157, causing sufficient compression to trigger a supernova.

With the sure knowledge of the destruction of the Sol System in little more than 60 years, the nations of the Sol System poured vast amounts of resources unto FTL research, the equivalent of 1% of system GDP (over $5 trillion per year). Within 10 years, the first FTL drives were developed. With 20 years, the first interstellar colonies were established. While there were no habutable worlds eithin 50 ly, there were no alien civilizations, and half of the star systems possessed worlds that could be terraformed. By 2154, the Sol System was abandoned except for a few million diehards who refused to leave.

It is now 50 years after the destruction of the Sol System, and humanity is distributed among the 1400 star systems within 50 ly if Sol. Since no colony could support every species, there is a substantial trade in biological lifeforms, especially in the 140 systems where terrafirming projects are ongoing. While it will be a 1,000 years before any world is habitable, there is hope among humanity that they might yet survive.

[maximara]

Originally Posted by AlexanderHowl

During the year 2051, astronomers detected a brown dwarf heading on an intercepting trajectory with the Sol System. An intergalactic object, it was traveling at 0.1c, so it was thought to have been ejected from its home galaxy by a supermassive black hole. By 2094, astronomers discovered that the brown dwarf would impact Sol in 2157, causing sufficient compression to trigger a supernova.

Uh. supernovas don't work that way unless you meant a white/black dwarf which would cause a Type Ia supernova: "Brown dwarfs are far too small at 0.08 solar masses to become supernova by accumulating material from another star as they have to reach the Chandrasekhar limit of at least 1.332 solar masses." See also Debunking Doomsday

A brown dwarf is in effect a huge Jupiter like object and would add to the mass of Sol without either it or Sol going supernova. It may not even hit Sol as there as Nemesis (the Sol system's own hypothetical brown dwarf)

[Daigoro]

Originally Posted by maximara

A brown dwarf is in effect a huge Jupiter like object and would add to the mass of Sol without either it or Sol going supernova. It may not even hit Sol as there as Nemesis (the Sol system's own hypothetical brown dwarf)

Well, the premise is that it will hit the sun, however unlikely that might be.

And 0.1c means it's carrying a lot of kinetic energy. I don't know if that would cause a supernova, perhaps it might be more like a bullet going through a water balloon.

However, I question whether an object travelling that fast would survive being ablated to nothing (or at least its solid core) by the intergalactic medium.

[Prince Charon]

Originally Posted by Daigoro

Well, the premise is that it will hit the sun, however unlikely that might be.

And 0.1c means it's carrying a lot of kinetic energy. I don't know if that would cause a supernova, perhaps it might be more like a bullet going through a water balloon.

However, I question whether an object travelling that fast would survive being ablated to nothing (or at least its solid core) by the intergalactic medium.

Good point, though depending on how big that core is, being hit by it at 0.1 C would probably do a lot of damage to the Sun.

[Astromancer]

Originally Posted by AlexanderHowl

Tidal effects are an inverse cube relationship, not an inverse square relationship.

Error corrected.

[AlexanderHowl]

Originally Posted by maximara

Uh. supernovas don't work that way unless you meant a white/black dwarf which would cause a Type Ia supernova: "Brown dwarfs are far too small at 0.08 solar masses to become supernova by accumulating material from another star as they have to reach the Chandrasekhar limit of at least 1.332 solar masses." See also Debunking Doomsday

A brown dwarf is in effect a huge Jupiter like object and would add to the mass of Sol without either it or Sol going supernova. It may not even hit Sol as there as Nemesis (the Sol system's own hypothetical brown dwarf)

At 0.1c, the compression caused by a core impact would cause the complete fusion of around 50% of the mass of the Sun (average temperatures within the core would reach over 6 billion K), releasing around 9 foe of energy, 9 times the average supernova. While it would not be a Type 1 or Type 2 supernova, I imagine that researchers would just create a new category for impact driven supernova.

[malloyd]

Originally Posted by Daigoro

However, I question whether an object travelling that fast would survive being ablated to nothing (or at least its solid core) by the intergalactic medium.

I don't see why it would. Let's try some numbers.

It's around 8 x 10^7 m in radius, so its cross section is around 8 x 10^16 m^2. Moving at 3 x 10^7 m/s is sweeps a volume around 2.4 x 10^24 m^3/s. The intergalactic medium is about 10^-27 kg/m^3, so it hits about 2.4 grams per second. Hitting at 0.1c 2.4 g/sec imparts about 1.1x10^12 J/sec, or about 13 microwatts per square meter. This is probably a bit more than something in a galaxy gets from surrounding starlight, but it trivial on the scale of what anything in a solar system receives from sunlight.

Yeah, steady heating probably doesn't work quite the same as effectively a directional low energy cosmic ray bombardment, particularly in terms of what happens right at the edges of the shadow, but it isn't going to overcome that many orders of magnitude difference.

[malloyd]

Originally Posted by Daigoro

And 0.1c means it's carrying a lot of kinetic energy. I don't know if that would cause a supernova, perhaps it might be more like a bullet going through a water balloon.

In terms of the plot though, I don't know that it matters. It's more than enough to perturb the sun. The exact order and timing of the planets being lethally irradiated, boiled and/or frozen is kind of inconsequential. Sure if its mild enough maybe in a million years something in the Solar System will be habitable again, but that's not of much importance to anybody on Earth.

[Daigoro]

Originally Posted by malloyd

I don't see why it would. Let's try some numbers.

It's around 8 x 10^7 m in radius, so its cross section is around 8 x 10^16 m^2. Moving at 3 x 10^7 m/s is sweeps a volume around 2.4 x 10^24 m^3/s. The intergalactic medium is about 10^-27 kg/m^3, so it hits about 2.4 grams per second. Hitting at 0.1c 2.4 g/sec imparts about 1.1x10^12 J/sec, or about 13 microwatts per square meter. This is probably a bit more than something in a galaxy gets from surrounding starlight, but it trivial on the scale of what anything in a solar system receives from sunlight.

Fair enough. The intergalactic medium appears to be extremely hot as well, but that would only add a few orders of magnitude and would still be trivial.

Originally Posted by malloyd

In terms of the plot though, I don't know that it matters. It's more than enough to perturb the sun. The exact order and timing of the planets being lethally irradiated, boiled and/or frozen is kind of inconsequential. Sure if its mild enough maybe in a million years something in the Solar System will be habitable again, but that's not of much importance to anybody on Earth.

I'm still wondering about how much effect it would have on the sun though. The sun is 1.3e9 m across, so the bullet would traverse that in 30s. What efficiency would the bullet have in imparting its energy to the different layers of the sun before it exits? And what if it's off centre a little? The sun's density drops off a lot from 0.4 radii.

[Astromancer]

Try this one...

In 2050 the faeries returned. They turned out to be from a nearby extradimensional space. Flesh and blood like humans but with powers at least partially gained from living over there the place outside.

At first, it was exciting happy news, at first. It turns out the Faeries were a lot like the ancient Irish or most other ancient warrior peoples. Violent, imperialistic, slave takers, ethnocentric, and self-righteous.

These faeries may be low tech (TL3) but they have a variety of psi powers and the ability to disappear to the Otherside at thousands of constantly shifting points. But humanity is now TL9 (well just barely) so they aren't nearly as vulnerable.

Note: The Arabs may speak of Jinni, the Cherokee may speak of the Nunne hi, the Hopi may speak of Kachinas, the Japanese of Kammi, and the West Africans of Mmoetia, but they all names for the same sort of creatures.

Basically, a sophisticated late 21st-century world is conflict with warrior tribes folk. The powers of the Faeries balance things out. Both the dynamics of tribal cultures and mental changes caused by living on the Otherside make communication less certain than it seems on the surface.