kottke.org posts about light

Personal light conesDec 02 2008

When I was born 35.2 years ago, a light cone started expanding away from Earth out into the rest of the universe (Minkowski space-temporally speaking, of course). Thanks to updates from Matt Webb's fancy RSS tool, I know that my personal light cone is about to envelop the Zeta Herculis binary star system, located 35.2 light years from Earth in the constellation Hercules.

With a mass some 50 percent greater than the Sun, however, and beginning its evolution toward gianthood (its core hydrogen fusion likely shut down), Zeta Her A is 6 times more luminous than the Sun with a radius 2.5 times as large. Nevertheless, the star gives a good idea of what the Sun would look like from a great distance, in Zeta Her's case 35 light years. The companion (Zeta Her B), a cooler class G (G7) hydrogen-fusing dwarf with a luminosity only 65 percent that of the Sun and a mass about 85 percent solar, orbits with a period of 34.5 years at a mean distance of 15 Astronomical Units (over 50 percent farther than Saturn is from the Sun). A rather high eccentricity takes the two as far apart as 21 AU and as close as 8 AU.

Hercules is of course named for the Greek hero, Heracles. Next up is Delta Trianguli, another binary star system, in about two months.

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