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52

I've made this into an answer because it's too long for a comment, and I really want to show the pictures. It is tempting to think of visible light as "close enough" to (near by wavelengths) and to conclude that "yes, actually, the yellow does affect it. I want a mirror without an obvious tint" However you are wrong, Physics will slap you down. Exhibit A ...


46

If you look at the reflectivity of gold (vs silver or aluminum) you can see a plateau at wavelengths below 500 nm source: If blue wavelengths are not reflected as well as other colors, the resulting image will look "more yellow" - which is what you see. At longer wavelengths, gold is a very good reflector (better than the other two above 600 nm). It also ...


5

A solid piece of metal with the thickness of 5 layers of foil is just like 5 layers of foil except that, since it is a single solid piece, the "layers" are able to conduct heat (quite quickly!) directly from one to the next. If the layers are instead separated by vacuum, the conduction of heat is eliminated, and heat transfer is greatly reduced (radiative ...


4

For this answer I'm going to pretend that the y-axis of the plot you've shown has had $\sim 7000\,{\rm km}\,{\rm s}^{-1}$ subtracted - this is a conventional thing to do in diagrams like the one you show, and simplifies the explanation/interpretation. The plot you show is based on observations. When observing distant objects like Coma, only 3 of the 6 ...


4

Both From Wikipedia Luminance Versus Luminosity In astronomy, luminosity is the total amount of energy emitted by a star, galaxy, or other astronomical object per unit time. It is related to the brightness, which is the luminosity of an object in a given spectral region. Now your question: Let's assume we have two stars that have the same surface ...


4

The current data release is DR12. As to how to interact with the data, it depends somewhat on what you want to do. If you have small queries, for instance if you want data for only a handful of objects, there are a couple of web interfaces. If you have larger queries in mind, CASJobs is a good place to start. You'll inevitably need the schema browser to know ...


2

You will see Earth, Venus, JupiTer, Saturn. TheY are either bright enough, or come closer to Mars than Earth, that there are no complications/calculations necessary. Uranus is just a naked eye object from Earth (magnitude 5.3-5.9). Its closest approach to Earth, when it is brightest is 17.2 au distant. Mars' orbit takes it closer by about 0.5 au, so you ...


2

Simply put, it is: how many aliens could we meet? More specifically: The Drake Equation is a way of predicting how many intelligent species there might be in the universe and the likelihood of them contacting us. There are a lot of things that can change the number of aliens we can expect to find. So we use what we know about the universe so far and ...


2

There is a lot more to it than just astronomy. For example, the tide times inside Boston Harbor are significantly different from those on the southeast coast of Cape Cod. It is true that the primary force behind tides is the position of the Moon, but the macro tidal bulges take a long time to propagate around/across oceans, and then the shoreline shape ...


2

Firstly, let's define what's on the axes (thanks to Kyle Oman for prompting me to do this): The velocity on the $y$ axis is not the total velocity of a galaxy through space; it is only the component of the velocity along the line of sight (LOS), measured by the redshift of the galaxy. Let's call it $v_z$, although on your figure it's just called $v$. The ...


1

Even if your ship traveled at (almost) the speed of light, you would have to follow the trajectory of a ray of light traveling from your point of origin to the star; not from the star to your point of origin. As described, you keep following the trajectories of many different rays of light (emitted at different times) backwards, putting yourself on a curved ...


1

DON'T. Yes, using IDL requires a valid license. If the code can be re-implemented in Python in a reasonable amount of time$^1$, do it. You might be helped along by astropy and pydl. The former provides a growing library of useful astronomy functions, the latter specifically targets reproducing astronomy IDL routines in Python (and is affiliated with ...


1

Due to the force of gravity, which goes as the inverse of the square, planets trace out an ellipse in space as they orbit around the sun, which is located at a single focus. The other focus is unphysical. Actually, given two massive bodies, their "difference" vector will trace out an ellipse with the center of mass at the focus. Because the sun is so much ...


1

You can check The Best Cheap Budget Telescopes Under $200; this presents the latest list of all affordable telescopes that are competent for beginners. Also you can check The cheap telescopes of 2014. Remember always that though magnification is good, but you must need to have a good apparture in your device & for that I prefer Newtonian telescopes or in ...



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