Sirius (pronounced “serious”) is the brightest star in the sky, at -1.45 apparent magnitude. In astronomy, apparent magnitude is the brightness of a celestial object as seen from Earth, not its intrinsic brightness. The smaller the number, the brighter the object. Our star, the sun, is rated about -26.7, which is why it should never be examined by naked eye!

Sirius is only 8.6 light-years away. In stellar parlance, Sirius is nearby; however, by common measures it is a long, long way away. The value of a single light-year is a fantastic 5.9 trillion miles, the distance light travels in one year.

In actuality, Sirius is a double star consisting of Sirius A, a white main sequence star, and Sirius B, which is a faint white dwarf. Multiple-star systems are common. Gravitationally bound together, they may contain several stars locked in complex orbital configurations.

At about 8 p.m., turn to the south and look about a third of the way up between the horizon and directly overhead. Constellation Orion is close by with its three belt stars to the right and somewhat higher than Sirius. Even in moderately light-polluted areas, this star is easily detected. Stars shine due to the energy they liberate in the process of combining (fusing) lighter elements into heavier ones. In contrast, planets and moons shine by reflected light, not light they generate internally.

Stars are created by the gravitational collapse of unimaginably huge clouds of dust and gas. This process creates tremendous heat which in turn causes nuclear fusion to occur in a young star. The star lights up, so to speak. All stars are massive by human standards but some are more or less massive than others. In a seeming paradox, super-massive stars progress through their life cycles more rapidly. More mass produces a stronger gravitational field, which accelerates the fusion process.

Stars much less massive than our sun will live longer than the present age of the universe, which is thought to be about 13.7 billion years.

Stars create heavier and heavier elements; some all the way up to iron. Even heavier elements are created by other, more massive stars in energetic processes such as nova and supernova explosions. These elements are blown into interstellar space. Next-generation stars in the area contain these elements, as do any planets which may form. Current models for stellar nucleosynthesis (star-formed elements) indicate that all elements beyond hydrogen, helium, lithium and possibly beryllium in our bodies and elsewhere were created by ancient stars.

— Kent Fairfield is a volunteer with Pine Mountain Observatory and a lifelong amateur astronomer. He can be reached at kent.fairfield@gmail.com. Other PMO volunteers also contributed to this article.