47

Let's interpret your question to be about whether the conditions would permit blobs of water to remain liquid, whether or not water existed yet. And the answer is No, because the pressure was by then far too low. Basically, space was already a vacuum, just not as hard a vacuum as intergalactic space is now. It is appealing to imagine an era when the universe ...


21

As others have mentioned in the comments, there wouldn't have been any oxygen to form water. Soon after the Big Bang, the protons were hot or dense enough to fuse up to helium and some lithium but nothing heavier. Heavier elements were eventually fused in the first stars and partially dispersed in space by their winds and when they exploded as supernovae, ...


8

At high temperatures, do planets glow like blackbodies? Yes, and at low temperatures too!1 1As @DavidHammen points out, since there's likely going to be a star nearby the planet, it will also be reflecting light from it, so the "glowing" with thermal radiation may in some cases be masked or at least mixed with reflected thermal radiation from the ...


8

The one from 2014 is still the record holder I believe - in the sense that it is reasonably convincing that the unseen companion of the pulsar PSR 2227-0137 is consistent with being a white dwarf with a surface temperature below 3000 K. It is worth considering why such objects might be difficult to find. (1) It is only the highest mass white dwarfs that have ...


7

The answer is of order 1 million years to cool from a standard end of He burning temperature of just over $10^8$ K to the top end of the white dwarf temperature range you give in your question. The details would depend exactly on the mass and composition of the white dwarf and there are also some theoretical uncertainties in neutrino cooling rates. The ...


7

Second question first: If the emitted power is the same does it matter if the emitting body is a large sphere of gas or a solid sphere? Not really. For thermal radiation discussed below, as long as the emissivity is high at the wavelength in question, it will radiate similarly to a blackbody. We see light from the Sun's photosphere which is roughly where ...


6

Consider a planet with effective temperature $T$ radiating as a blackbody, emitting a total luminosity $L=4 \pi \sigma R^2 T^4$. At distance $a$ the power per square meter will be $$P = \frac{L}{4\pi a^2} = \sigma \left(\frac{R}{a}\right)^2 T^4.$$ If we demand a sun-like energy flow of $P_{required}$, we get a necessary temperature $$T=\left[\frac{P_{...


5

Possible, but rare. The reason is that many things are not linear with respect to temperature. Volume of gas is in direct proportion to temperature (at given pressure) but we rarely need to consider this. But, for example, the density of water is markedly non-linear with temperature. Moreover our physiometric response to temperature is also non linear. We ...


4

Partial problem with Anders' answer: 730K is a "hot Jupiter", which I think are usually kept hot by stellar insolation, which would also heat the proposed moon. Removing that heat-source: Shortly after Jupiter formed, assuming it orbited at its present distance from the Sun, at some point it might have had a surface radiation temperature of 730K, ...


4

No, they aren't all covered in water ice. As an example, Io, a moon of Jupiter is covered in volcanically deposited sulfur and sulfur dioxide frost. Solar system mechanisms are pretty complex and varied, so we wouldn't expect similar quantities of water as exist on Earth. Also, the "frost line" for water in the Solar System isn't the same as the &...


4

The confusing language is due to wave-particle duality. At higher frequencies and larger distances, the particle model is more accurate: Ray-tracers can track photons as they reflect, refract and scatter (but not diffract) and photons arrive in discrete events. But at low frequencies the wave model is more accurate: individual photons are less important and ...


4

They are looking at one very specific degree freedom of the individual mirrors. The collective oscillatory motion the mirror in the direction of the laser beam. When isolated from the full equations of motion for the mirror, the effective equation of motion for this degree of freedom is a harmonic oscillator with an effective mass of 10 kg (remember the ...


4

Color is a difference, not an absolute value Being "blue" doesn't (necessarily) mean that a light source has a large flux in the $B$ band. A color is not an absolute value; it is the ratio between two fluxes or, equivalently, the difference between two magnitudes. Being blue means "More flux in some short wavelength band (e.g. $B$) than in a ...


3

Your general idea about this process is correct. At close semimajor axis distance, rock can evaporate and will form a Silicate-oxygen atmosphere. For low-mass rocky planets, the condensation flow from day to night-side, as it necessarily is very hot, will have to compete with the possibility of instead escaping vertically from the nightside, instead of ...


3

My impression is that for answering your question, one would actually have to run simulations, ideally so-called global circulation models (GCM). If this is for a research project, the MIT GCM would be a good candidate to set up for the atmosphere of Io. Of course, there are research groups working on that issue, e.g. the team of Prof. Goldstein at the ...


3

I would not attribute too much importance to the quote "colder than expected", because that always depends which expectations one had initially. Here the quote you are discussing: Temperatures on the moon's surface plummeted to minus 190 degrees celsius (-310 degrees Fahrenheit) during the probe's first lunar night, which "was colder than ...


3

TL;DR: about 5 times current eccentricity for a deviation by 5 degrees from the mean... but the devil is in the celestial mechanics and climate model details. It would not quite work, because the length of seasons would be uneven. Currently Earth's north and south hemispheres get nearly exactly as much or little sunlight as the other. But on the eccentric ...


2

The website on Main sequence stars fromr the Austalian national telescope facility lists star mass, temperature and life span: Mass/MSun Luminosity/LSun T=Effective Temperature/K Radius/RSun t=Main sequence lifespan/yrs 0.10 $3×10^{-3}$ 2,900 0.16 $2×10^{12}$ 0.50 0.03 3,800 0.6 $2×10^{11}$ 0.75 0.3 5,000 0.8 $3×10^{10}$ 1.0 1 6,000 1.0 $1×10^{10}$ 1.5 ...


2

Don't have high enough reputation to comment, but someone should mention the Stefan-Boltzmann Law: https://en.wikipedia.org/wiki/Stefan%E2%80%93Boltzmann_law When a planet (or anything) gets warmer, the amount of radiation it emits increases with the 4th power of temperature (measured on an absolute scale like Kelvins). A planet's temperature reaches ...


2

Maybe somebody can help me understanding the following quote intuitively: However, by looking at the ratio of two different but related lines - those of iron - we found the ratio itself related to temperature. And it did so in a consistent and predictable way. A particular atom can only be at integer quantum states (Hydrogen is depicted here for simplicity)...


2

Stars behave like blackbodys. Not perfect idealized blackbodies, however, the spectrum of a star is close enough to the standard blackbody spectrum. Reason why you can use the Wien's Law to calculate an estimate of its surface temperature: $\lambda_{\rm max} = (0.29 {\rm\, cm\, K}) / T$ Where $\lambda_{\rm max}$ is the frequency of maximum measured emission ...


2

I imagine that a planet will become too hot for Earth type life - or even hypothetical life with different biochemistries might be able to live at much higher temperatures than Earth life - long before it becomes engulfed by its star's atmosphere. Even the coolest stars have surface temperatures of a few thousand degrees, so a planet which is close enough to ...


2

I don't have time to write up a full answer with derivation, but you might want to have a look into the standard radiation transport literature (e.g. the book by Mihalas & Mihalas) or the radiation transport in stellar interiors (e.g. Kippenhahn) or literature for irradiated exoplanets, see e.g. Guillot (2010). The Milne-Eddingtion-approximation (short: ...


2

Hardly. Maybe. Probably. It depends. Liquid water at atmospheric pressure is densest at 4°C - but that is a function of pressure and temperature. The phase of a material (solid, liquid, gas, critical) depends on both, pressure and temperature - and so does the density which depends on both, linearly within one phase, discontinuous at phase boundaries. The ...


2

On the basis of this review article by Delbo et al. (2015) about modeling asteroid properties, I think it might work something like this: From optical measurements (where you're seeing reflected sunlight) and knowledge of the asteroid's orbit and its current orientation with respect to the Sun and Earth, you can work out its approximate size, shape, and ...


1

this sounds like a fun homework question for upper-division astronomy !! a couple more points to consider in your solution: small angle approximation (to go from radius r to solid angle subtended by the star's disk as seen from the planet). is the planet rotating? if rotating fast, temperature as a function of longitude will be constant. if rotating slow, ...


1

OK, let's try some simple calculations. (Short answer: it's overwhelmingly the body's own thermal emission.) The mid-IR light (let's use 10 microns, since a key design goal for NEOCam was ensuring imaging out to that wavelength) from the Sun can be approximated by emission from a 5800 K blackbody. The reflected 10-micron sunlight for an asteroid at a ...


1

So, the big bang started 13.7 billion years ago, and for the next 380,000 years, the universe expanded and cooled, so atoms could start forming later on. 13,685,000,000 years ago, the early universe was too hot and dense for liquid water to form. So, the answer is NO, liquid water could not form about 15 million years after the big bang. Hoping this was ...


1

The "dark" side of the Moon is only truly dark during full Moon. Everywhere on the Moon there is day and night as well. The dark side of the Moon is called like that because we do not see it from Earth, since the Moon shows us always the same side due to tidal locking - not because it is always dark there. In other words: During (lunar) day, the ...


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