Posts by HDE 226868
In reality, if you want to build a star, you need to specify a mass and a chemical composition, and then use the equations of stellar structure. This requires some numerical integration, and it's f...
I agree largely with Matthew's answer; this is intended to put everything on a more quantitative footing. The answer to your question primarily depends on three things: the mass of molecules in th...
Sort of. A structure similar to the one you describe can in fact form. Triple-stranded DNA can be stable under certain conditions. Two bases bond via slightly different structures, and a third bas...
Sure. Not a whole lot, but you'll get a decent number. Beer et al. 2004 present a formula for calculating the mean time before a star passes within a distance $b_{\text{min}}$ of another star: $$...
Just reduce the rate at which you lose entanglement (The paper, for anyone wanting to read it, is Humphreys et al. 2018.) The hey problem here isn't entangling particles, per se - the problem is ...
Based on the current state of thinking, somewhere in the vicinity of a couple hundred kilometers. This particular formation theory (Zhang & Lin 2020) is a variant of an idea that's been kicked...
A decent proxy for habitability and long-term colonizability is the effective temperature of the planet - essentially the surface temperature. A planet's effective temperature scales as $T\propto (...
Try microlensing other evaporating black holes Folks have suggested Hawking radiation; I don't think that's a particularly good idea. If you run the numbers, a black hole would need to have a mass...
It would be uniform. The crust of the Moon is, on average, about 50 km thick. There is indeed some stratification in its composition, with upper layers composed largely of feldspar and a lower lay...
A cosmic void. Your best bet would be in a cosmic void. While not entirely empty - they do contain small numbers of galaxies and clouds of gas - they are substantially rarefied compared to your av...
The best tools for this job, I think, are perturbation theory and Laplace's planetary equations. You might know that the orbit of a planet can be described by six osculating elements $(a,e,i,\omega...
The behavior of strange matter is not well understood - least of all under the conditions we're used to on Earth! Most theoretical treatments focus on places in which strange matter is likely to be...
At least on Earth, astronomical instruments are extremely precise and sensitive compared to the innate biological abilities of an astronomer! Sure, I can look up at the sky and see that Betelgeuse ...
Simulations of the dynamics of planets close to massive stars during a supernova (Veras et al. 2011) indicate that a planet in a reasonably tight orbit ($\sim2\text{ AU}$) around all but the lowest...
The scenario you describe - accreting matter being expelled by radiation pressure - will occur if the object exceeds the Eddington luminosity, a limit derived from hydrostatic equilibrium based on ...
A simple answer is that the planet is on an orbit with a high inclination relative to our line of sight. The other planets in the system may appear, from our perspective, to be in line with us and ...
There are a whole bunch of different ways to determine the thickness of a planet's ice sheets; over the decade, dozens have been tried on Europa and other icy bodies. Broadly speaking, as we're wor...
The density profile of a planet's atmosphere arises from two laws of physics: hydrostatic equilibrium and the ideal gas law. Put together, they require that the density $\rho(z)$ be a function of t...
In most quantum field theories$^{\dagger}$, we have a quantity called the Lagrangian, from which we can derive information about the behavior of our system. It consists of a number of terms represe...
Imagine an Earth-like planet orbiting a Sun-like star in the inner halo of the Milky Way. As a halo star, it will likely be somewhat metal-poor, having formed early in the life of the galaxy, but o...
This has actually been an area of intense research for decades now. Astronomers are quite interested in the distribution of stellar masses in a variety of different galaxies and clusters. The preci...
Here's a first-order approximation based on a fundamental limit: diffraction and angular resolution. How far someone can see of course depends on the size of the object they're looking at, because...
It wouldn't. The field of a magnetic dipole has a strong radial dependence; it falls off proportional to $r^{-3}$, where $r$ is the distance to the dipole. The values you list are the strengths of...
The collapse of bubbles on various scales has actually been an area of research for quite some time. Analyses are typically numerical, and rely on something known as the Rayleigh-Plesset equation, ...
You have two questions to consider here: Can compounds required for blue atmospheres form in significant amounts on this planet, and are the temperatures right for them to condense and form clouds?...
