User:RJHall/temp

From Wikipedia, the free encyclopedia

1 Proposed lead
2 Wiktionary
3 Starbox character2
4 Orbit
5 Barnard's Star
6 References
7 Separation
8 Asteroid
9 Proxima Centauri

[edit] Proposed lead

Cygnus X-1 (abbreviated Cyg X-1)^[1] is a strong X-ray source in the constellation Cygnus. It was found in 1964 during a rocket flight and is one of the strongest seen from Earth, producing a maximum X-ray flux of 2,300 μFy. Cygnus X-1 was the first X-ray source widely considered to be a black hole candidate and is amongst the most studied astronomical objects in its class. It is now estimated to have a mass about 8.7 times the mass of the Sun^[2] and has been shown to be too compact to be any known kind of normal star or other likely object besides a black hole. If so, the radius of its event horizon is probably about 26 km.^[3]

[edit] Wiktionary

/ˈɝːθ/

[edit] Starbox character2

Characteristics

Test 1

G2 V

^[A]

K1 V

^[B]

Test 2

0.24

0.64

Test 3

0.24

0.64

Test 4

0.24^A

0.64^B

Test 5

0.24^A

0.64^B

Test 6

None

[edit] Orbit

The solution for the orbital period of a small body is given by:

$\begin{smallmatrix}P = 2\pi\sqrt{\frac{a^3}{GM}}\end{smallmatrix}$

where P is the orbital period, M is the mass of the central body, a is the length of the orbit's semi-major axis, and G is the gravitational constant.^[4] It follows that for a hypothetical, relatively small planet in orbit around Vega:

$\begin{smallmatrix}\frac{P_{planet}}{P_{Earth}} = \sqrt{\frac{M_{Vega}}{M_{Sun}} \cdot \left( \frac{a_{planet}}{a_{Earth}} \right)^3} = \sqrt{ 2.11 \cdot {6.1}^3} = 21.9\end{smallmatrix}$

giving an orbital period of 21.9 Earth years.

[edit] Barnard's Star

From Barnard's Star the Sun would appear on the diametrically opposite side of the sky at the coordinates RA=5^h 57^m 48.5^s, Dec=−04° 41′ 36″, which is located in the eastern part of Monoceros. The absolute magnitude of the Sun is 4.8, so, at a distance of 1.828 parsecs, the Sun would have an apparent magnitude $\begin{smallmatrix} m = M_v + 5\cdot((\log_{10} 1.828) - 1) = 1.1 \end{smallmatrix}$ .

[edit] References

^[5]

^[6]

^ Cite error: Invalid <ref> tag; no text was provided for refs named science3656
^ Cite error: Invalid <ref> tag; no text was provided for refs named iorio
^ Harko, T. (June 28, 2006). Black Holes. University of Hong Kong. Retrieved on 2008-03-28.
^ Braeunig, Robert A. (2007). Orbital Mechanics. Rocket and Space Technology. Retrieved on 2007-11-02.—See formula 3.9.
^ Hwang, Shuen-Cheng; Robert D. Lein, Daniel A. Morgan (2005). "Noble Gases", Kirk-Othmer Encyclopedia of Chemical Technology, 5th edition, Wiley. DOI:10.1002/0471238961.0701190508230114.a01.pub2. ISBN 047148511X.
^ Häussinger, Peter; Reinhard Glatthaar, Wilhelm Rhode, Helmut Kick, Christian Benkmann, Josef Weber, Hans-Jörg Wunschel, Viktor Stenke, Edith Leicht, Hermann Stenger (2001). "Noble Gases", Ullmann's Encyclopedia of Industrial Chemistry, 6th edition, Wiley. DOI:10.1002/14356007.a17_485. ISBN 3527201653.

[edit] Separation

In cartesian coordinates, a star's position in parsecs can be represented as:

$x = \frac{1}{\pi} \cos( 15 \cdot \alpha ) \cos( \delta )$

$y = \tfrac{1}{\pi} \sin( 15 \cdot \alpha )\cos( \delta )$

$z = \frac{1}{\pi} \sin( \delta )$

where α is the Right ascension in units of hours, and δ is the declination in degrees. Thus, Tau Ceti is located at:

$x = \frac{1}{0.274} \cos( 15 \cdot 1.73 )\cos( -15.93 ) = 3.6496 \cdot 0.8992 \cdot 0.9616 = 3.1557$

$y = \frac{1}{0.274} \sin( 15 \cdot 1.73 )\cos( -15.93 ) = 3.6496 \cdot 0.4376 \cdot 0.9616 = 1.5357$

$z = \frac{1}{0.274} \sin( -15.93 ) = 3.9496 \cdot -0.2745 = -1.0840$

or (3.1557, 1.5357, -.1.084). UV Ceti is located at:

$x = \frac{1}{0.374} \cos( 15 \cdot 1.65 )\cos( -17.95 )= 2.6736 \cdot 0.9081 \cdot 0.9513 = 2.3097$

$y = \frac{1}{0.374} \sin( 15 \cdot 1.65 )\cos( -17.95 )= 2.6736 \cdot 0.4187 \cdot 0.9513 = 1.0649$

$z = \frac{1}{0.374} \sin( -17.95 ) = 2.6736 \cdot -0.3082 = -0.8240$

or (2.3097, 1.0649, -2.8472). The distance D between these two stars is then: $D = \sqrt{ (3.1557 - 2.3097)^2 + (1.5357 - 1.0649)^2 + ((-1.0840) - (-0.8240))^2}$ $= \sqrt{0.7157 + 0.2217 + 0.0676}$ = 1.005 parsecs, or 3.28 light years. As a sanity check, Tau Ceti is 11.9 ly distant and UV Ceti is 8.73 ly distant. The absolute minimum separation between them is 11.9-8.73=3.17 ly.

[edit] Asteroid

Proper motion (μ)

RA:
Dec.:

4156.93 mas/yr
3259.39 mas/yr

For asteroid albedo α, semimajor axis a, solar luminosity $L 0$ , Stefan-Boltzmann constant σ and the asteroid's infrared emissivity ε (~ 0.9), the mean temperature T is given by:

$\begin{align} T & = \left ( \frac{(1 - \alpha) L_0}{\epsilon \sigma 16 \pi a^2} \right )^{\frac{1}{4}} \\ & = \left ( \frac{(1 - 0.0436) (3.827 \times 10^{26})} {0.9 (5.670 \times 10^{-8}) 16 \cdot 3.142 (3.959 \times 10^{11})^2} \right )^{\frac{1}{4}} \mbox{K} \\ & = 173.7 \mbox{K} \end{align}$