Inhabitable Planets Too Close Together?

Depending on the Ph of the oceans, the concentration of Fe-II would be on the order of one part in 1eex6 to 1eex7.

With average Ocean depth of 4,000 meters, the sectional density of H2O is 4eex6 Kg per square meter.

The sectional density of dissolved Fe-II available to deplete the Oxygen is then on the order of 4 kilograms per square meter.

Compare this to the sectional density of Oxygen in the atmosphere of 2,000 Kilograms per square meter.

Even if the oxidation process is rapid, the supply of dissolved Fe-II will be depleted long before the supply of free Oxygen is depleted.

To add a little hydrogen to the fire, here's a suggestion that systems with "hot Jupiters" have the munchies. The process that creates the "hot Jupiter" sends all the inner terrestrial planets into the star.

http://www.sciencedaily.com/releases/20 ... 215039.htm

The good thing is that detailed analysis of a high-definition spectrum can tell whether the star has eaten its own children.

Burp!

JohnRoth wrote:To add a little hydrogen to the fire, here's a suggestion that systems with "hot Jupiters" have the munchies. The process that creates the "hot Jupiter" sends all the inner terrestrial planets into the star.

http://www.sciencedaily.com/releases/20 ... 215039.htm

The good thing is that detailed analysis of a high-definition spectrum can tell whether the star has eaten its own children.

Burp!

Interesting. We already knew that giant planets can sometimes migrate, which would disrupt the orbits of rocky planets of the inner system. That part has been known for almost fifteen years. This new research suggests that some of those disrupted orbits cause rocky planets to fall into the star, with resulting changes in spectrum. Basically, this could be a way of detecting systems where giant planets have migrated inward and removed rocky planets.

Conversely; this suggests that stars with low "metalicity" are most likely to have earth like planets. Confirmation that such stars have gas giant type plaets in the outer system but not the inner system would identify stars that are most likely to have earth type planets.

If very large telescope built in space during the early diaspora were incapable of identifying habitable planets, perhaps they launch very high Cee fractional probes?

Imagine a probe massing perhaps 10 tons.

It is equipped with a relatively small diameter but robust light sail massing perhaps 90 tons.

The package massing a total of 100 tons is launched at ten gees using lasers to boost it.

Thrust = 100m/s^2 x 1eex5 Kg = 1eex7 Newtons

Power requirement?

Light pressure (at rest) = 2P/Cee

1eex7 N x 3eex8 M/s = 3eex15 Joules

Assume technology for solar pumped lasers exists during the early diaspora exists.

Assume buildigsuch a system at about 1/3 AU from sun.

Insolation is 1eex4 Watt per square meter.

Surface area = 30eex10 square meters.

Diameter = 6eex5 meters or 600 kilometers.

If you boost at ten gees for about a month or 2.5eex6 seconds

Velocity = 100 m/s^2 x 2.5eex6 s = 2.5eex8 M/s or about 5/6 Cee

Distance from the Sun at end of boost?

Distance = 1/2 x 100 m/s^2 x (2.5eex6s)^2 = 300eex12 meters or 300 billion kilometers
or 2,000 AU
Or .03 Light Years.

Our probe can use it's light sail to perform gravity assist course changes at a series of candidate stars that it desa fly by of to search for terrestrial planets.

Our probe would beableto detect planets,
Image planets with perhaps ten kilometer resolution.
Derive orbital data.
Derive temperature and gross climate data.
Perform Spectroscopic data to verify composition of atmosphere.
Relay all data to slower colony ship that is launched simultaneously (or even earlier) that then uses gravity assist maneuvers to arrive a star system where a habitable planet has been identified.

These probes might make boo boos just like Niven's ramrobotos that result in colonies discovering that their new planets are very marginal.

Hence we get Grayson.

SWM wrote:

JohnRoth wrote:To add a little hydrogen to the fire, here's a suggestion that systems with "hot Jupiters" have the munchies. The process that creates the "hot Jupiter" sends all the inner terrestrial planets into the star.

http://www.sciencedaily.com/releases/20 ... 215039.htm

The good thing is that detailed analysis of a high-definition spectrum can tell whether the star has eaten its own children.

Burp!

Interesting. We already knew that giant planets can sometimes migrate, which would disrupt the orbits of rocky planets of the inner system. That part has been known for almost fifteen years. This new research suggests that some of those disrupted orbits cause rocky planets to fall into the star, with resulting changes in spectrum. Basically, this could be a way of detecting systems where giant planets have migrated inward and removed rocky planets.

We don't have textev for unmanned probes, but it is certainly plausible.

But for Grayson, the text states pretty clearly that the colonists left Earth with no idea whether there would be a habitable planet at the other end. It was a true leap of faith. They also set out fairly early in the Diaspora 314 PD (2417 AD). Grayson is over 500 light-years from Earth. If a sublight craft launched from Earth today (2014 AD), it still would not have reached Grayson by the time the Grayson colony ship left Earth. They deliberately went far far beyond any exploration had yet occurred.

This press release just crossed my system: "Milky Way may bear 100 million life-giving planets." Compare this number to the estimated 400 billion stars in the galaxy.

http://www.sciencedaily.com/releases/20 ... 100725.htm

As usual, the journal reference is at the bottom.

100 million planets is still plenty. That's an average of 1 out of 400 stars, which is actually fairly high. Assuming a star density similar to that in the Solar neighborhood, that means 1 habitable planet per 100,000 cubic light-years, or an average separation of 46 light-years between habitable planets.

SWM wrote:100 million planets is still plenty. That's an average of 1 out of 400 stars, which is actually fairly high. Assuming a star density similar to that in the Solar neighborhood, that means 1 habitable planet per 100,000 cubic light-years, or an average separation of 46 light-years between habitable planets.

Isn´t it 1 out of 4000?

Tenshinai wrote:

SWM wrote:100 million planets is still plenty. That's an average of 1 out of 400 stars, which is actually fairly high. Assuming a star density similar to that in the Solar neighborhood, that means 1 habitable planet per 100,000 cubic light-years, or an average separation of 46 light-years between habitable planets.

Isn´t it 1 out of 4000?

Sorry, you're right. 1 out of 4000 stars.

SWM wrote:100 million planets is still plenty. That's an average of 1 out of 400 stars, which is actually fairly high. Assuming a star density similar to that in the Solar neighborhood, that means 1 habitable planet per 100,000 cubic light-years, or an average separation of 46 light-years between habitable planets.

Tenshinai wrote:Isn´t it 1 out of 4000?

SWM wrote:Sorry, you're right. 1 out of 4000 stars.

The press release says there are 10 billion stars in the galaxy, while the Fount of All Knowledge says 100 to 400 billion. (http://en.wikipedia.org/wiki/Milky_Way ) Their comment is that 1% to 2% of all systems would have a planet which could host multi-cellular life. Either their estimate of the number of stars in the galaxy is incorrect, or the press release isn't telling the full story (What! A press release is wrong? Egads, what is the world coming to!)

I'm translating "complex" into "multi-cellular" here. That doesn't include planets with life that's still in the single-cell stage. To interpret this, remember that the Great Oxygenation Event occurred prior to the origin of multi-cellular life here on Earth.