The Sky This Month
Welcome to our night-time sky . Please enjoy this monthʼs tidbits of knowledge . We are lucky to live in a dark-sky area where the heavens can shine through . I hope you enjoy the sky and perhaps learn a thing or two . Happy star gazing ! Round and Round – Sometimes two stars get up close and personal . They circle round and round each other in a cosmic dance . These stars are known as binary stars . The two stars get caught in each otherʼs gravitational pull and orbit around their barycenter , which is the combined center of mass of the two stars . Typically we think of an orbit as a planet circling around the Sun . In the case of a planet , the planetʼs mass is minuscule in comparison with the Sun . The Sun exerts so much gravitational force that it remains fairly stationary in comparison to the planet . In the case of a binary star , the two masses are much closer in size . One star does not remain stationary while the other orbits around it . Instead , the stars orbit around the combined center of mass . If the two stars were exactly the same mass , then the barycenter would be exactly halfway between the two stars . In most cases , one star is much larger than the other , so the barycenter is shifted closer to the larger star . The most famous binary star systems are in the handle of the Big
Dipper . In the center of the handle are Mizar and Alcor . These two stars form a visual binary , but do not orbit each other . However , Mizar is actually a combination of multiple binary systems . Mizar A and Mizar B orbit each other over thousands of years . Mizar A is a binary system with an orbit of about 20 days . Mizar B is also a binary system with an orbit of about six months . When Stars Collide – Binary systems do not last forever . As two stars orbit around each other , they eventually get closer and closer , their orbital period speeds up , and eventually they combine to create a new star . What is truly extraordinary is that astronomers have located a binary system that will collide within our lifetime . This magical event will occur in 2022 . For about six months the new star will be visible to the naked eye in the constellation of Cygnus . This new star has been named the Boom Star . Interestingly , the star already exists . We just cannot see it yet . The Boom Star is about 1800 light-years from us , so it takes 1800 years for light from the collision to reach the Earth . Astronomers are able to predict the timing of the creation of the Boom Star by measuring the acceleration of the orbital period . We will have to wait a few more years to see if their prediction comes true .
– Brian Biggs Amateur Astronomer
6 February 2017 pccnews