Discovering and Observing Sirius B

Observing the companion of Sirius through an amateur telescope is a challenge even when the two stars are farther apart than usual (as will be the case for the next few decades). The story of the Pup's prediction and discovery is an exciting tale. You will recall that in 1718 Halley announced his discovery of proper motion that he had made by comparing the positions of Sirius, Arcturus, and Aldebaran in his time to those recorded in ancient times. In the years from 1834 to 1844, the...

How Big Is Betelgeuse

The brightness variations of Betelgeuse are interesting enough but they are accompanied by changes in the star's size. These pulsations in the size of red giants have been compared to the beat of a vast heart and to the breathing of a vast beast. An AAVSO publication discusses the probable cause of the pulsations Astronomers think the outer layers of the star expand slowly for several years and then shrink again, so the surface area alternately increases and decreases, and the temperature rises...

The Foot of Al Jauzah

Rigel is sometimes said to mark the western knee of Orion, the Hunter, but its name suggests that it marks the foot (we can picture Orion with this forward foot upraised as he prepares to strike with his club at the onrushing Taurus, the Bull). Paul Kunitzsch tells us that the name Rigel was first used in the West more than a thousand years ago, when it was adopted from the Arabic title rijl al jauza the foot of al Jauzah. We do not know who al Jauzah was but the word seems to refer to Orion as...

The Departing

When we learn of the true brightness and motion of Aldebaran in space, the story of the star in relation to us is as thought provoking as any of the myths and legends about it. Ever since I was quite young, I was impressed by a certain seldom-noted fact about Aldebaran it is receding from us much more rapidly than is any other 1st-magnitude star. In fact, of the more than three hundred stars that are brighter than magnitude 3.5, I count only three that are moving away from us at a greater rate...

The Names and Lore of Spica

In ancient Egypt, Spica was supposedly very important, being known as the Lute-Bearer and Repa, meaning the Lord. The English astronomer Sir Joseph Norman Lockyer believed that several very important temples of very ancient Egypt and ancient Greece were dedicated to Spica, which may have been associated with the legendary Egyptian personage Menes. In medieval times, one of the names that the Arabs applied to Spica was Sunbulah. The nineteenth-century deep-sky writer Admiral Smyth states that,...

Sirius in Lore and Culture before the Twentieth Century

A reasonably complete guide to the lore of the brightest stars would fill a long book of its own. In such a book Sirius might have the longest chapter. Here, I will touch upon only a brief selection of the lore beyond what we have already discussed. An interesting point about Sirius is that it seems to have been identified as a dog or doglike creature in many ancient cultures. How did this characterization of the star get started It has been suggested that Sirius was regarded as a faithful dog...

The Closest Neighbor

We still should start our discussion of Alpha Centauri with a look at its most famous attribute its nearness. The story of how that nearness was discovered begins in the 1830s. Three different astronomers were trying to be the first to find stellar parallax, each astronomer with a different star. Friedrich Wilhelm Bessel settled on a dim naked-eye double with large proper motion, called 61 Cygni. Friedrich Wilhelm von Struve chose Vega. But Scottish astronomer Thomas Henderson had the advantage...

The 200 Brightest Stars continued

Greek Proper RA for Declination Spectral Visual Absolute Distance Name Name 2000 for 2000 Classification Magnitude Magnitude(in light-years) Greek Proper RA for Declination Spectral Visual Absolute Distance Name Name 2000 for 2000 Classification Magnitude Magnitude(in light-years) Absolute Distance Magnitude (in light-years) absolute magnitude The magnitude of brightness a star would have if seen at a standard distance of 10 parsecs (about 32.6 light-years). altazimuth system A system for...

The Name Sirius and the Dog Days

Sirius is mentioned in the writings of Homer and Hesiod, but they called it Kyon, the Dog. Indeed, later, the eighth brightest star in the heavens, Pro-cyon, received its name, which means before the Dog, in reference to its rising just a little before Sirius for viewers at midnorthern latitudes. So mighty is Sirius that even another star's name is derived from that star's role of coming up just before Sirius magnitude 1.98 Beta Canis Majoris is called Murzim or Mirzam in Arabic, the roarer...

Eyes and Telescopes4

Learning how astronomers measure the positions of stars and understanding in what fashion stars move during the course of a year is very important. We can't observe particular stars if we don't know where to look for them. We had quite a lot to say on these topics in the previous chapter. But what happens once we do figure out the positions of the stars we want How well we may actually see them will depend strongly on how much light pollution we have at our observing site, how much haze is in...

Motions of Stars in Space

We've listed the major parts in the structure of the universe and discussed the distances between those parts. All that remains for this chapter is to explain how the parts move. The fact that objects in the solar system move in more or less in some cases, very much less circular orbits around the Sun is well known. The movements of galaxies within our Local Group or of even larger-scale motions other than the expansion of the universe are mostly poorly known. So it's only the motions of stars...

Red Sirius the Dogon and Triple Sirius

Is it possible that Sirius B became a white dwarf as recently as two thousand years ago A number of ancient writers seem to say that Sirius was reddish others, such as Manilius, speak clearly of its blueness . In, Burnham's Celestial Handbook, Robert Burnham lists Aratus, Cicero, Horace, Ptolemy, Seneca, and others as having made comments indicating the Dog Star's ruddiness. Could Sirius B have still been a red giant then, dominating the coloration of the point of light called Sirius even to...

Sirius and Sirius B as Suns

Two thousand years ago, Manilius wrote of Sirius that hardly is it inferior to the sun, save that its abode is far away. He was right, but compared to most stars Sirius is close to us. Sirius lies 8.60 light-years from Earth, making it the seventh closest star system known but the second closest visible to the naked eye. Sirius is almost exactly twice as far away as the Alpha Centauri system, but the latter is too far south to be seen by much of the world's population. Sirius is over half a...