# Tag Info

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Surprisingly it's quite easy to answer this because we can use the cosmic microwave background as a reference. The CMB gives us an average inertial frame for the universe so our motion relative to it is the closest we can come to defining the Solar System's motion through space. The CMB is isotropic, but because we are moving relative to it the radiation is ...

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Orbits are pretty complicated. Most texts on this deal in terms of predicting positions at a specific time rather than just a simple ellipse, because that model while correct is too basic. As others mentioned position estimation makes it more complex because there are more parameters involved. I'll just pull some stuff for you on the basics. For standard ...

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Try to read this paper Accurate masses and radii of normal stars: modern results and applications. G. Torres, J. Andersen and A. Gimenez. Astron. Astrophys. Rev. 18 no. 1-2, pp. 67-126 (2010), arXiv:0908.2624. You can find links to systems with orbits and accurate fundamental parameters there. Some of them calculated on the base of third Kepler's law. ...

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The BICEP2 paper reports a tensor/scalar ratio r=0.20+0.07−0.05, but then says: This is the value taken before corrections. There exist contributions to the B- mode due to changes in the photon polarization of the CMB while it is traveling before reaching the detector. The dust is the interstellar dust that has to be modeled. Subtracting the various ...

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Most of the brightest stars are spectral types B,A,F main sequence stars (50%), but there are also a bunch of O-type main sequence and giant stars (5%) and another big clump of red giants (about 35%) and a few percent are supergiants. There are no white dwarfs, and definitely no neutron stars! I have attached an image which I created by selecting 4992 ...

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$L = \int \int {\bf F} \cdot d{\bf s}$ is where you should start, where $F$ is the flux in units of Watts/m$^2$. Blackbody flux is given by $\sigma T^4$ and hence an isotropic flux integrated over a sphere $$L \int^{2\pi}_{0} \int^{\pi}_{0} \sigma T^4 r^2 \sin \theta\, d\theta\,d\phi = 4\pi r^2 \sigma T^4$$

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The surface of the sun is where local plasma cools enough to recombine and go transparent, the photosphere. You would still be deep within the sun's atmosphere, and it would be LOUD. H-bombs are LOUD at the edge of their fireballs.

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The Milky Way is receding from the members of the Hydra-Centaurus Supercluster. The Hydra cluster has a red shift of 0.0548. The Centaurus cluster has a red shift of 0.0114. The Norma cluster has a red shift of 0.0157. The local group is and will continue moving away from the Hydra-Centaurus Supercluster.

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Extensive googling hasn't helped me to understand how this observed earth rotation angle is used to compute UT1 As explained in: this lecture Earth's angle of rotation = 2π(0.7790572732640 + 1.00273781191135448(Julian UT1date - 2451545.0)) radians. So one observes Earth's angle of rotation and calculates the Julian UT1 date as a decimal date from that ...

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Sound as you hear it is waves of pressure differences in the air, which is interpreted by your ear as sound. So no, you cannot directly hear electromagnetic radiation (EMR). You could, however, take the EMR and convert it into sound waves in the audible range, which you could listen to. This was done in 1990 for Jupiter by Voyager as it passed Jupiter. It ...

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One perspective (heh) involves the following relation among position vectors: $$\vec{r}_{A\rightarrow C} = \vec{r}_{A\rightarrow B} + \vec{r}_{B\rightarrow C}.$$ These position vectors can be for anything; object $A$ could be a house, object $B$ an ant, and object $C$ a leaf on the river. Here's a diagram to help: So if you want to know the position of ...

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Yes, the Sun and our whole Solar System are revolving around the centre of our galaxy, the Milky Way. Milky Way is a spiral galaxy and hence has four major spiral arms and a central buldge. The Sun (and, of course, the rest of our solar system) is located near the Orion arm, between two major arms (Perseus and Sagittarius).

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You could also try the VizieR online catalog of astronomical databases Put "binary stars" in the search box and you will find many databases, many of which will include the sort of orbital parameters you are looking for.

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inner radius of habitable zone (AU) $= \sqrt{\frac{L}{1.1}}$ outer radius of habitable zone (AU) $= \sqrt{\frac{L}{0.53}}$ where $L$ is absolute luminosity of the star. See Calculating the Habitable Zone for more information.

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There is a reasonable chance that yes, planets can form before the star "ignites" (which I take to mean the fusion of hydrogen into helium, not the very brief phase of deuterium burning which certainly will take place before planets can form). Planets form in a disk of circumstellar material around their parent protostars. The "core-accretion" model of ...

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1) First, you said that the telescope would be > 150 mm so that atmosphere is the limit, not diffraction. But the question was, will a 114 mm scope work? Not only are you diffraction-limited, but actually coupling all of the laser power into the scope so as to get that level of collimation on the output beam is not trivial. It is true, though, that this ...

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I'm not sure what you are looking to know in your question. There are many problems with specifying a date/time centuries in the future and saying XXXX body will be at RA YYY, DEC ZZZZ. The Mayan calendar was primary designed to predict seasons much like most calendars. The basic elements of the Mayan calendar had little to do with astronomy and much like ...

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