Taurus

In late autumn, look for the angry eye of the Bull.

Taurus and the Pleiades … and You



The Taurus Region

[source: Nicolas Eynaud, Creative Commons license]


Taurus ...

We should locate Taurus first. Find the Pleiades, that tight knot of 6 (or 11?) bright stars (upper right in the diagram). A bit later, east of the Pleiades, look for a reddish star at one tip of a “V” cluster lying on its side. The star is Aldebaran, the angry eye of the Bull. The “V” is the cluster named Hyades which indicates the Bull's head, the start and direction of the longish horns. The horns reach NNE toward the Milky Way.


Where is the rest of the Bull? The myth makers needed to explain why only the head, horns, and forequarters were visible. Problem solved. Taurus is the Bull rising from the sea and so he is largely submerged. Good pics and facts can be found here.


There are, however, competing myths because almost every culture recognized the Bull. Cave paintings made over 15,000 years ago depict Taurus. The Minoans, according to Burnham, were very “Bull-oriented.” Their capital Knossus was home to the legendary maze guarded by the Minotaur. In the illustration above you see Orion, rising a bit later, either defending against or attacking the Bull, or both.


In 1603 Bayer described the Bull’s eye as having a “rose-red tint.” The Hindus named the star rohini, the Red Deer. To me the term rohini evokes “red” references across cultures and continents. Aldebaran is spectrum K5. More on stellar classes here.


Aldebaran will not remain part of the Hyades “gang” forever. The star is twice as near to us as most of the “V,” and is moving in a different direction from our perspective. An Ohio State website defines proper motion as the apparent angular motion of a star across the sky with respect to more distant stars. Aldebaran has a divergent proper motion. Compared to the rest of the heavens, the Hyades is a close neighbor. The light from it that we see this month left those stars in 1890 or so.




The Pleiades

[source: Rochus Hess, homepage]


Pleiades are commonly known as the Seven Sisters. My favorite origination story is Polynesian: the mighty hunter Orion, offended by a competing bright star in his stomping grounds, picked up Aldebaran and hurled it, smashing the rival into the many still-bright Pleiades. We have another thing to clear up. How many Sisters are there? Close inspection caused people to think there was a missing sister, giving rise to more myths.

One claim not to be believed is that Pleiades is the Little Dipper, at least not the official one which is far to the north. Their proper motions are very similar, and the false little dipper is expected to hang together for at least 20,000 more years.


... And You

If you’d like to learn more, you might consider tackling these more probing questions and projects. At the conclusion there will be my answers and opinions, and the gist of each task will be repeated there.


1. A thought question: Your own view toward the eastern horizon may be obstructed. You may have to wait a while in the evening, or wait until later in December or even January, but Taurus then will be up earlier in the east and these descriptions will not be affected. Let’s say you spot the Pleiades but nothing lower. If Aldebaran is 12 degrees below (behind) the Sisters, how much time must you wait for it?


2. When you see Pleiades and Aldebaran both, use your outstretched hand to estimate the degrees it covers. Can you use that gauge to find the tips of the Bull’s horns 8 degrees to the north northeast? Can your thumb cover the 2-degree diameter of Pleiades?


3. Aldebaran is spectrum K5 III. Fiind other sources that explains the spectrum scale, and use them to compare the redness of Aldebaran with other major red giants like Betelgeuse, Antares, and alpha Hercules? For a start use

https://courses.lumenlearning.com/astronomy/chapter/colors-of-stars/

https://www.cfa.harvard.edu/~pberlind/atlas/htmls/note.html


4. Burnham reported the date of Hyades opposition as December 3. What is opposition? Among the Hyades, Aldebaran is twice as close to us as most of the others and has a different proper motion. Find the distances and describe in general terms the proper motions of each. What will happen to the shape of the V over time?


5. With your unaided eye, how many bright Pleiades do you count? … how many with binoculars?


 

For my results, see below ...

1. If Aldebaran is 12 degrees below (behind) the Sisters, how much time must you wait for it? The stars appear to return to their positions in 24 hours because the earth has rotated 360 degrees. Twelve degrees is one-thirtieth part of a rotation and also a thirtieth part of 24 hours, or 48 minutes. The stars also return to position in a year and so they will advance 12 degrees at the same time of night 12 days later.


2. When you see them both, use an outstretched handspan to estimate the degrees it covers. Can you use that gauge to find the tips of the Bull’s horns 8 degrees to the SSE? Can your thumb cover the 2-degree diameter of Pleiades? I use the fact that a pencil’s thickness will cover one-half degree. A big thumb and a short arm might just do it!


3. … compare the redness of Aldebaran with other major red giants like Betelgeuse, Antares, and alpha Hercules. Alpha Hercules is a red double star. The brighter is also redder at spectrum M5. Betelgeuse is also an M-star. Antares in Scorpius is type M1. These are all redder (cooler) than Aldebaran. Maybe the Bull is not as angry as I thought.


4. Hyades opposition is December 3. What is opposition? Among the Hyades, Aldebaran is twice as close as most of them and has a different proper motion. Find the distances and the proper motions of each. What will happen to the shape of the V over time? A reference you might want to bookmark is the Sky&Telescope glossary. On page 10 of this pdf a map of Hyades motions shows that the “V” will tighten up a bit in 100,000 years.


What about the Bull’s eye? Stardate reports that “Aldebaran is fairly close — just 65 light-years away — so its motion is more pronounced than that of many other visible stars, which are farther away. Since the occultation of 509 CE, in fact, Aldebaran has moved roughly a quarter the diameter of the Moon in our sky. It’s a tiny shift, but it adds up. Over the millennia, Aldebaran will drift slowly southward — depriving the bull of his bright eye.”


... and in the next video, you can fly out past Aldebaran and be among the Hyades.


5. With your unaided eye, how many bright Pleiades do you count? … how many with binoculars?


I’d be happy to hear your results on any of these items, and your comments on the article. You can use the Feedback form in the footer of each page.