* Astronomy

Members Login
Post Info
TOPIC: Algol


L

Posts: 130035
Date:
Algol
Permalink  
 


Algol, (Beta Persei), in the constellation Perseus is nearly overhead at around 10:30 p.m. local time.

Algol is an eclipsing binary system.
The light from Algol appeared to fade every 68 hours 48 minutes and 56 seconds.
Medieval Arabs were aware of its marked changes in brightness, and assigned it the name "Demon Star". The word "ghoul" comes from the same Arabic word.
To the Ancient Greeks, Algol was the "Head of Gorgon Medusa".
The Chinese gave it the gruesome title Tseih She, the "Piled-up Corpses".


Position(2000): RA = 03h 08m 10.13s Dec= +40 57' 20.3"

In 1782, amateur astronomer John Goodricke realised that the star was really a pair of stars orbiting a common centre of gravity. When the dimmer of the two crossed in front of the other, the light from Algol appeared to fade.


A blue spectral class B8 star with a diameter of 3 solar diameters and red-yellow spectral class K2 star of about 3.5 solar diameters are in very close orbit around each other . There are indications that Algol system contains at least one other star, quite distant from the other two, and orbiting them in a little under two years. There is also evidence for as many as three other companions, which would make Algol a sextuple star system.

Algol lies some 93 light years (28 parsecs) from the Earth. When not eclipsed by its companion, its magnitude of +2.1 makes it the second brightest of the stars in the constellation of Perseus.

On the night of November 26-27, observers across much of North America and throughout Europe will be in perfect position to watch Algol undergo its eclipse. Most of the time the star's light appears constant, but for about four hours its light varies noticeably. At its minimum brightness Algol appears only about one-third as bright as normal.

It is and ideal target for Amateurs, because the entire eclipse takes 9 hours and 40 minutes from start to finish, the entire eclipse can be seen in a single night.
November/December is the ideal time.



Algol will be at minimum at 1:25 GMT on November 27, ideally placed for Europeans.
Check Algol's brightness, against nearby stars, a couple of hours before the predicted minimum. It is at minimum light for a 20-minute period, as the large, dim star passes directly in front of the smaller, brighter companion.

There are several opportunities to see Algol undergo an eclipse during December.
For the Americas, it will be at minimum on December 14 at 1:20 a.m. EST and on December 16 at 10:09 p.m. EST (7:09 p.m. PST).

__________________
«First  <  129 30 31 | Page of 31  sorted by
Quick Reply

Please log in to post quick replies.



Create your own FREE Forum
Report Abuse
Powered by ActiveBoard