Capella (42 light-years): Space aficionados remember 1973 (when Capella’s light took flight for Earth) as the year Comet Kohoutek (C/1973 E1) was discovered and Skylab, the first U.S. space station, was launched. Veterans of the Vietnam War will note that 1973 was the year direct U. S. military involvement in this conflict finally ended.
All in the Family was the top-rated TV show, and many of today’s middle-agers were disco dancing beneath a rotating mirror ball.
Aldebaran (65 light-years): In 1950, the year Aldebaran’s light began its earthly journey, Dutch astronomer Jan Oort proposed the existence of an orbiting cloud of comets (now called the Oort Cloud) at the outer reaches of the solar system. If you’ve arrived at retirement age (typically, mid to late 60s), Aldebaran shines in your honor. Its ruddy light left around the time you were born, continued onward as you went to school, began a career, got married, and had children and then grandchildren. It finally arrived just as you retired — literally the journey of a lifetime!
Betelgeuse (640 light-years): When it comes to accurately knowing a star’s distance, we now enter a realm of uncertainty. The parallax of Betelgeuse is so minuscule that even Hipparcos satellite measurements are iffy. The currently accepted figure means the photons striking your retinas left during the latter part of the 14th century. Since none of us was around then, we have to rely on historical events. When light left the surface of Betelgeuse, China’s Ming Dynasty had begun, the Aztecs were settling in what is now Mexico City, and the European Renaissance was in its infancy.
Rigel (860 light-years): Rigel’s distance is variously reported as between 700 and 900 light-years, with a Hipparcos measurement hinting at 860 light-years. Imagine a star so luminous that it ranks seventh in brightness in our nighttime sky even though the void separating us is so vast that its light has been traveling since the middle of the 12th century! When we look at Rigel, our eyes are picking up starlight launched earthward around the time of the early Crusades.
Defining a star’s distance by the events occurring on Earth when its light began its journey adds a dimension not achieved by mere numbers. Later this year, we’ll revisit the distance/history link with a look at summer stars.
Questions, comments, or suggestions? Email me at
gchaple@hotmail.com. Next month: What’s in a name? Clear skies!