Ultra-cool dwarf star?
Frankly, "set course for the Tyrion system" would be cooler...
Astroboffins have discovered a trio of roughly Earth-sized planets orbiting an ultra-cool dwarf star, the first time such a system has been identified. Using the Belgian TRAnsiting Planets and PlanetesImals Small Telescope (TRAPPIST) 'scope at The European Southern Observatory's La Silla Observatory in Chile, a team led by …
"not massive enough to sustain hydrogen fusion"
If it was not sustaining Hydrogen fusion then it wouldn't be a star; it would just be a gas giant. It does, in fact, sustain Hydrogen fusion but via Deuterium fusion, which is the second stage of the Hydrogen-1 proton-proton fusion process that powers larger stars.
Hydrogen is the easiest element to fuse and so yes, all stars start by fusing Hydrogen.
Briefly, as the gas that is to become a star collapses and compresses under its own gravity it reaches a point where the Hydrogen at the center of the gravitationally collapsing gas becomes heated and compressed sufficiently for fusion to occur. The outpouring of energy from the the newly started fusion process then counteracts further collapse due to gravity but once most of the Hydrogen in the core is fused the out-pressure from fusion drops and the star resumes gravitational collapse until the Helium in the core, produced by the fusion of the Hydrogen, can start fusing. The Helium fusion, along with the renewed gravitational collapse, leads to Hydrogen fusion in a shell around the Helium core (which is when the star starts its giant phase). This process may repeat several times, depending upon the characteristics of the star, with successively heavier elements fusing in the core, surrounded by multiple fusing shells of progressively lighter elements.
Evolution of life as we know it requires three major things - liquid water, sufficient energy input, and time. The first two are taken care of, has the third been?
Another potential issue is that planets that close would be tidally locked to the star, and have one side in perpetual daylight and the other in perpetual (and likely icy) night. The habitable range of the planet may be the relatively small portion in perpetual twilight, though at a certain distance the large section under full sun would be good to go. I wonder what sort of different creatures might evolve in an environment without a night or in perpetual twilight? Probably would look like Avatar's world with a lot of bioluminescent critters, if our deep ocean is any guide.
You do realise that cold, small stars burn for a lot longer? Or not so much burn as smoulder and eventually cool. They're lifetimes could be measured by the trillion years, not the 10 or so billion our little yellow dwarf star can look forward to.
Not necessarily, if they are so small they don't burn their hydrogen, but only deuterium...
Granted the lifetime is probably very very long anyway, but I was more curious about how old the system was. If the star only formed 100 million years ago, life is unlikely.
The bottom of our oceans gives clues as to what dark side inhabitants of these planets might look like and their food chain. In fact, it may be less of a strict separator than we think. Some creatures might require sunlight and stay in light, some abhor it and stay in dark, and some may go back and forth. Like deep water vent ecosystems.
If the planets are tidally locked, wouldn't the dark side be frozen solid? Unless the heat differential causes ocean currents and winds strong enough to mix things up and prevent that...not really sure how that would work.
Studies of HD 189733b – discovered in 2005 transiting the star HD 189733, which lies some 63 light years from Earth in the constellation Vulpecula – have revealed that the planet has a mass of around 13 per cent greater than Jupiter's, but that it's 180 times closer to its sun than our own gas monster.
That, and the fact that it's tidally locked, mean that temperatures on the permanently sun-facing side hit 1,000°C, and a positively balmy 650°C on the dark side.
That's according to a 2007 observation by NASA's Spitzer Space Telescope, although later work by Swiss astronomers suggested temperatures in the upper atmosphere might reach a scorching 3,000°C.
Whatever the case, it's bloody hot, but the "mild" (as NASA puts it) temperature variation between the planet's lit and unlit sides mean that winds are likely distributing heat around the planet.
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