Posts by HDE 226868
We have plenty of examples where stars have been hidden by nebulae - and not just newborn stars. Typically, the gas and dust comes from mass loss from one of the stars in the system. Examples inclu...
TL;DR I'd propose that weak force life has a tiny change of existing in environments where particles travel at high speeds. A possible example is the jets produced by an active galactic nucleus. A...
Your environment is quite similar to that in a globular cluster. At its densest, a globular cluster may see peak stellar number densities of $\sim1000$ stars per cubic parsec, which implies a mean ...
TL;DR As most of the other answers say, the plants on this world would likely be purple-ish, using photosynthetic pigments that operate at the same wavelengths as bacteriochlorophylls. Chlorophyll...
Atmosphere loss As you've suggested in your question, once a Sun-like star leaves the main sequence, it begins losing mass through a strong stellar wind, a stream of charged particles driven by ph...
Not unless life evolves extremely quickly. There are two conditions for cosmic background radiation to be able to support life: It's partially composed of photons at wavelengths required by phot...
Supercritical carbon dioxide Once upon a time, Venus may have had seas of supercritical $\text{CO}_2$ ($\text{scCO}_2$) thanks to a higher surface temperature (by a few hundred Kelvin) and surface...
Super-rotation As I wrote in an answer to another question about winds, studies of slow-rotating planets like Venus have yielded information about what we should expect for planets like this in ge...
Summary It turns out that even relatively low-mass ocean planets are capable of forming some of the exotic ices you name in their cores. Ice VII appears to form at the centers of planets of $0.015...
Tachyons are detectable. Fortunately, I believe your question is based on a mistaken premise. Tachyons, if they exist, would likely indeed be detectable. In fact, since they were initially theoriz...
Models of planetary structure indicate that ocean planets should reach peak size at a few hundred to a thousand Earth masses, reaching maximum radii of perhaps 4-5 Earth radii. Add in some iron and...
Introduction In our universe, the cosmic microwave background was formed approximately 400,000 years after the Big Bang. It was hot, but within a few million years after the Big Bang, it would no ...
Equations of state The "ocean" should be described by an equation of state that relates thermodynamic variables (e.g. density $\rho$, temperature $T$, pressure $p$, etc.) to one another. Different...
Yup! This is possible, and a number of small bodies in the Solar System have rings: Haumea, a dwarf planet in the outer Solar System, was recently discovered to have rings, which lie inside its R...
What can a star be made of? A star's composition is limited by the elements that exist in significant quantities in the universe. These include primordial elements - hydrogen, helium and lithium -...
The answer to your question depends strongly on the supernova rate in the galaxy. The Milky Way currently is not an active galaxy - the supermassive black hole at its center is relatively quiescent...
Alexander's answer is completely correct; there is no way to split one black hole into smaller ones. I think, though, that it might be worth explaining why this is the case, particularly because th...
The situation you're considering involves a rotating black hole characterized by the parameters $M$ and $J$, the mass and angular momentum of the black hole. The two are encapsulated in something c...
No, wind patterns are not always going to be the same. Venus is a key counterexample here. Its Hadley cells extend to 60 degrees above and below the equator - double the size of Earth's Hadley cel...
In my answer to another question, I suggested that the Super-Earth in question be tidally locked to its host star for a period of time while part of its surface experienced a bombardment. After tha...
I'm reminded strongly of Iapetus, a moon of Saturn that has a dramatic two-tone coloring. One hemisphere is quite light, while the other is dark. It almost looks like you dunked half of the moon in...
A star's life ends when it can no longer undergo fusion at its core. For massive stars, this often happens when the core is made largely of iron, which can be fused (and is) in small amounts, but o...
With the naked eye, humans can see approximately 6th-magnitude objects. We can compute the apparent magnitude of a planet at a given distance, and find the distance corresponding to an apparent mag...
Pressure is important here. It's both a problem and a solution. As expected in giant planets, the atmospheric pressure and temperature change with altitude and depth. By the time you get to the ba...
Backwards running will almost certainly never be as fast or efficient as regular running. A study back in 2011 showed that it should takes about 30% more energy to run backwards at a given speed. W...