As Halloween approaches, there is a star that is associated with the season. Early watchers of the night sky noticed that the star dimmed and then rose in brightness. Early astrologers associated the star with bad fortune.
The star is officially known as Beta Persei. It is the second brightest star in the constellation Perseus. From mythology, Perseus was the Greek hero that killed Medusa, rode the winged horse Pegasus, and killed Cetus the sea monster. He then rescued Andromeda and married her.
The ancient stellar map makers named this star “Algol,” which means the “Demon Star.” To the Hebrews, it was called “Rosh ha Satan,” which is “Satan’s Head.” It was also known as the “Winking Star.”
It wasn’t until the late 1800s that Edward Pickering suggested that the reason for the varying brightness was a dimmer star rotating in orbit around a brighter star. Due to its alignment to earth, this dimming is visible to us.
In 1889 evidence was provide by Hermann Vogel that this star was actually a binary star. It’s varying brightness being caused by one star passing in front of the other. The distance between the two stars is one-twentieth the distance of the sun from Earth. After carful observations, the star varied in brightness over a period of about three days, the exact time for one star to orbit the other. The star varied from a minimum of 3.5 to a maximum of 2.3. The change in Algol’s brightness was not caused by any evil influence, but by the laws of gravitation.
The best time to actually seen the change in the star’s brightness is to use tables to find the time of the star’s minimum brightness. Watching the star over a period of a couple of hours, anyone can watch the star brighten by a full magnitude.
Saturn will be visible in the southern skies this month. The moon will be extremely close to Saturn on the evening of Oct. 5.
Mars makes its return to the morning skies this month. On the morning of Oct. 26, the moon will be above Mars.
Mercury and Venus will return to the evening skies this month. On the evening of Oct. 29, the moon will be close to both Mercury and Venus. On Oct. 30, both Mercury and Venus will be next to each other.
Jupiter will be visible in the southwest skies this month. On Oct. 31, the moon will be above Jupiter.
The next meeting of the Springfield Astronomical Society will be Oct. 22. It will be at the Library Center at 4653 S. Campbell Ave., Springfield. Starting time is 7 p.m. Our web site is http://www.springfieldastronomy.org.