The problem with that with stars was, well, the only place they’d been observed from was Earth. Even the “parallax” of the Earth’s orbit around the sun wasn’t enough to help much with extremely distant stars. Astronomers, historically, would take plates of the night sky in the winter and then compare them to plates taken in the summer. This allowed for parallax with a separation between measurements of nearly two hundred million miles. But when talking about the universe, that was not near far enough for really good triangulation.
So, clever astronomers figured out others ways to get fairly accurate measurements of star distances by using things called Cepheid Variables. Cepheid Variables are a type of star that blinks in brightness with a clocklike periodicity. The period of the blinking is directly tied to how bright the star should be due to the physics of the star’s inner makeup. So if a certain Cepheid was blinking at a given rate, then astronomers knew exactly how bright it should be. By measuring how bright it looked in the sky they could determine just how far away it was, since stars appear dimmer with distance as a one over the distance squared type law.
The Cepheid Variable measurement method was the best way to make deep sky measurements, but the process is much less accurate than good old triangulation. Now being able to use triangulation with many light-years distance on the parallax leg would allow for an amazingly detailed survey of the galaxy. But that would take time.
Runner took as many shots as he could to store away in the database. Astronomers could use the data and analyze it for many years to come. If he ever had the time, Lieutenant Commander Weaver probably wouldn’t mind taking a gander at the data in more detail himself, but Runner doubted the commander would ever have another free moment as long as he lived.
For the first time man was looking at stars from a completely different direction. Before the mission was done it was intended that the entire sphere be swept so that every star in the catalogue could be viewed from another angle.
And soon they would get images from really far away from the sun and…
While the computer was chuckling over the planetary data, Runner extended a second scope, less powerful than the main but still good enough, and started hunting around by eye. Epsilon Eridani had two planets already detected, both gas giants. But one of the gas giants was at only two astronomical units away from the star. That was right at the edge of the potential life zone of E Eridani.
The life zone of a star was the zone in which the star’s luminosity provided enough heat to keep water from freezing but not boiling it. Between 0 and 100 degrees Celsius. For Sol, the home star of Earth, that range was from .95 astronomical units out to 1.5, technically. There was a straightforward calculation to calculate the zone based on a star’s luminosity.
Life zone was an important factor in the potential development of life. Every form of life humans had found by going through the Looking Glasses was based on water to one degree or another. So having liquid water was a given.
Brighter stars, the really hot ones like Vega, would have very broad life zones, if they even had planets rather than just an accretion disks of debris, while cooler ones, such as E Eridani, had very narrow life zones. Based purely on that, life was more likely to be found around hot stars. However, another necessity was sufficient time for life to develop. And hot stars had very short lives. It took about three billion years for the first life to develop on Earth after it cooled. A sun like Vega might only last a couple of billion years, leaving behind cold, dead planets.
On the other hand, smaller cooler stars such as E Eridani, while they lasted a long time, had very narrow life zones. And the life zone changed over time, generally getting closer to the sun and narrower as the star cooled. For that matter, planets close in had a tendency to become tidally locked as the moon was with Earth, one side always facing the star. While life could develop in those conditions, it was unlikely.
That was why the current survey had intended to concentrate on stars much like Sol. G class stars lasted a long time but had relatively broad life zones.
The kicker to all that theory was the experience humans had developed through surveying the planets on the other side of the Looking Glass portals and planets in the Sol system. The first thing that was noted was that greenhouse gases played an important part in whether or not a planet was habitable. Venus, in the Sol system, was right on the inner edge of the life zone. But Venus’ atmosphere was so choked with greenhouse gases that the surface temperature was nearly 400 degrees C. Mars, too, was right at the edge of the life zone, on the chillier side. But Mars had virtually no greenhouse gases in its limited atmosphere. If humans could somehow switch their atmospheres, the two planets would be marginally habitable.
Planets on the other side of the Looking Glass had a tendency to be pretty poor. The portals had connected mostly to planets of some long gone race that had once used a similar system and had left behind inactive bosons. Most of the planets were in fading life zones, either those where the sun was starting to flare up in death or too cooled off to support life. Some of the planets appeared to have been terraformed, that is they had had extensive work done to them to make them habitable. That long gone race, perhaps the same race that made the warp engine for the Blade, had done the equivalent of switching Mars’ and Venus’ atmospheres.
But they showed that, depending on a huge number of factors, the life zone of a planet could be about twice as large as first thought.
Furthermore, it was apparent that while life could crop up under the oddest conditions, only a certain number of types turned up. So far in all the planets surveyed only four different biologies had been found. Two of those, human and Adar, were “green” biologies. That is, both used something that looked more or less like chlorophyll as a basic energy gathering system. One was “blue” and the last was “red.”
Given that over forty planets had been found with some sort of life, there should, by straight evolutionary principles, have been forty different biologies. Instead there were four. Chloro A, Chloro B, Blue and Red.
Biologists and paleontologists were engaged in a hot debate about just why this was the case. The arguments fell into two broad categories: statistical genesis and panspermia.
Statistical genesis argued that when life was developing there were a limited number of functional ways it could occur. An infinite number of monkeys might try to start life, but only four were likely to take. Panspermists called this the “by guess and by gosh” theory.
Panspermists believed that either by the actions of some long gone race or due to microscopic survivors hitching a ride on rocks scattered into space, all life had originated in only four different conditions and then spread through the galaxy.
What statistical genesists said about panspermists wasn’t fit to print. “Creationism by another name…” and it went downhill from there.
Runner had kept up with all the theoretical discussions even before he was volunteered to this mission. He just liked the debates and theories. So when he was hunting around he had a specific mission. The inner planet of E Eridani was well outside the theoretical life zone. But he kept in mind that word: “Theoretical.” There were so many theories being crushed by this mission, he wasn’t willing to settle for “theory.”
The planet itself was unlikely to have life. It was a gas giant, a super-massive planet of nothing but gas and metallic gas, gas crushed under so much pressure it turned solid. In fact, it was possible that the “planet,” which was bigger than Jupiter, had been a brief-lived sun. But gas giants usually had rocky moons. And if the moon had enough CO2…