Three Dimensional Look at the Winter Sky Sirius Stars of Orion and Aldebaran

The beautiful winter constellation Orion and the nearby brightest fixed star Sirius are well known. On the opposite side of Orion is the bright Aldebaran in the constellation of Taurus, or the Bull. Only two centuries ago, the distances to these stars were unknown. A watcher of this section of the starry sky would think of it as two dimensional. But now, when admiring this region, we have the extra bonus of knowing how far away they are. We indicate in Fig. 8.5 this part of the sky, together with distances for most of the stars. Here the nearest ones are Sirius at 2.7 pc and Aldebaran at 20 pc (or 65 light years). The other bright stars are all farther than 100 pc and generally at such large distances, parallaxes cannot be measured from the ground, and the distances have been estimated by other means.

Today, the measurement of parallaxes is a fundamental step in the cosmic distance ladder. Stars beyond 50 pc may be reached from above the Earth's atmosphere, where the stars look sharp. The European Hipparcos satellite in the 1990s measured stars several times more distant. A total of 100,000 were measured, nevertheless reaching only a small fraction of the size of our Milky Way. In the 2010s, the space observatory Gaia will measure out to at least 20,000 pc almost covering the whole Milky Way!

Aldebaran 20 pc

Fig. 8.5 Sirius, the stars of Orion and Aldebaran of the Bull (Taurus) make a beautiful view in winter evenings. The stars are located at very different distances in space, here given in parsecs (1 pc = 3.26 light years)

0 400 pc Rigel 240 pc

Aldebaran 20 pc

Fig. 8.5 Sirius, the stars of Orion and Aldebaran of the Bull (Taurus) make a beautiful view in winter evenings. The stars are located at very different distances in space, here given in parsecs (1 pc = 3.26 light years)

The Art Of Astrology

The Art Of Astrology

Get All The Support And Guidance You Need To Be A Success With Astrology. This Book Is One Of The Most Valuable Resources In The World When It Comes To A Look at Principles and Practices.

Get My Free Ebook


Post a comment