# Tag Info

1

According to wikipedia it is 10 degrees. Wikipedia cites Peißker et al, which uses the formula: $$\Delta\phi = \frac{6\pi G}{c^2}\frac{M}{a(1-e^2)}$$ to derive a relativistic periapse shift of 9.9 degrees per orbit.

6

I'm assuming you're talking about physical distances (as opposed to any of the other distance measures in cosmology). The comoving distance to a galaxy at redshift $z$ is $$d_C(z) = \frac{c}{H_0}\int_0^z \frac{dz}{\sqrt{ \Omega_r(1+z)^4 + \Omega_m(1+z)^3 + \Omega_k(1+z)^2 + \Omega_\Lambda }},$$ ...

2

In terms of asking the question in the title, there are various catalogues which include stellar ages, if you search on VizieR for the category "Ages" (in the "Astronomy" menu on the right-hand side) you will find a large number of such catalogues, but you will have to bear in mind that they focus on certain sets of objects rather than stars in general. One ...

3

There isn't really a database as you request. Finding the ages of stars is difficult. Only one star has an accurately known age - the Sun. That comes from radioisotope dating of meteorites. For other stars we must rely on models to a greater or lesser extent and we can only estimate an age if the star has a mass or is in a phase of its evolution where things ...

1

Use Wien's displacement law - as you suggest. Let's assume that the spectrum you have been given incorporates almost all the flux from the star. This might be ok, so long as the flux is heading towards small numbers at each end of the spectrum? If so, then you can use the temperature-independent shape of a blackbody function to argue that some fixed fraction ...

1

The average str is about half the size of the Sun. So I get 44 km. 20 km/s is equal to $6.47 \times 10^{-13}$ pc/s, but we've just established that a pc is about 44 km in your sand grain model. So the speed is $2.85\times 10^{-10}$ m/s. Just a double check - to travel 1 pc at 20 km/s would take $1.5\times 10^{10}$s. To travel 44 km at $2.85\times 10^{-10}$...

5

Barry Carter's nice piece of work contains 50 stars within $\sim 74$ light years of Betelegeuse. Leaving aside the question marks over exactly where Betelegeuse is (in terms of distance) and the parallax uncertainties of the 50 stars listed, there is also the problem that the faintest stars in the HYG catalogue are based on the Hipparcos catalogue, which is ...

7

 \begin{array}{|c|c|c|} \hline \textbf{Star} & \textbf{Magnitude} & \textbf{Distance (ly)} \\ \hline \text{Betelgeuse} & \text{0.45} & \text{0.00} \\ \hline \text{HIP27648} & \text{8.24} & \text{17.82} \\ \hline \text{HIP28478} & \text{8.42} & \text{19.03} \\ \hline \text{HIP27573} & \text{7.41} & \text{24.27} \\ \...

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