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Dark stars and black holes both have a surface escape velocity equal or greater than lightspeed, and a critical radius of r ≤ 2M. However, the dark star is capable of emitting indirect radiation – outward-aimed light and matter can leave the r = 2M surface briefly before being recaptured, and while outside the critical surface, can interact ...
[1] [2] [3] In the unlikely event that dark stars have endured to the modern era, they could be detectable by their emissions of gamma rays, neutrinos, and antimatter and would be associated with clouds of cold molecular hydrogen gas that normally would not harbor such energetic, extreme, and rare particles. [4] [2]
≡ 1 ft/(min⋅s) = 5.08 × 10 −3 m/s 2: foot per second squared: fps 2: ≡ 1 ft/s 2 = 3.048 × 10 −1 m/s 2: gal; galileo: Gal ≡ 1 cm/s 2 = 10 −2 m/s 2: inch per minute per second: ipm/s ≡ 1 in/(min⋅s) = 4.2 3 × 10 −4 m/s 2: inch per second squared: ips 2: ≡ 1 in/s 2 = 2.54 × 10 −2 m/s 2: knot per second: kn/s ≡ 1 kn/s ...
As φ has a range of 360° the same considerations as in polar (2 dimensional) coordinates apply whenever an arctangent of it is taken. θ has a range of 180°, running from 0° to 180°, and does not pose any problem when calculated from an arccosine, but beware for an arctangent.
The Dark Star, a 1917 novel by Robert W. Chambers; Dark Star, a 1929 novel by Lorna Moon; The Dark Star, a 1939 novel by Margaret Mackie Morrison, writing as March Cost; Dark Star, a 1969 novel by Norma K. Hemming, writing as Nerina Hilliard
The FUV channel can work with one of three diffraction gratings, the NUV with one of four, providing both low and medium resolution spectra (table 1). In addition, COS has a narrow field of view NUV imaging mode intended for target acquisition. [2] One key technique for achieving high sensitivity in the FUV is minimizing the number of optics.
Einasto's model has the same mathematical form as Sersic's law, which is used to describe the surface brightness (i.e. projected density) profile of galaxies, except that the Einasto model describes a spherically symmetric density distribution in 3 dimensions, whereas the Sersic law describes a circularly symmetric surface density distribution ...
The light seen is approximately the integral of all emission along the line of sight modulated by the optical depth to the viewer (i.e. 1/e times the emission at 1 optical depth, 1/e 2 times the emission at 2 optical depths, etc.). Near the center of the star, optical depth is effectively infinite, causing approximately constant brightness.