You can view Arcturus in the night sky by extending the arc in Big Dipper. Arcturus is an orange-giant and can be seen from most parts of the world.
As an avid night-sky watcher, you might be well aware of the Big Dipper in the north-easterly sky. The Big Dipper has one long arc-like handle. If you could extend an imaginary line to this arc, it will end up to a bright star called Arcturus.
Its magnitude is -0.05 make it the 4th brightest star in the night sky!
Because Arcturus is located only 19 degrees north of the celestial equator, it is easily visible from the Southern as well as Northern hemisphere.
Arcturus is a member of Bootes constellation as called in the Latin language. In English, Bootes constellation is known as Herdsman, and the French and Spanish people call it Bouvier and Boyero respectively.
Do you know that Arcturus is known as the Bear Guard too? It is so because its constellation, the Herdsman, is often imagined as guarding the Great Bear, or Ursa Major.
In Latin, ‘Ursus’ has the same connotation as the word bear in English! Thus, Ursa Major means greater bear, which is one of the most conspicuous constellations that can be seen throughout the year by those who reside in the Northern Hemisphere. Ursa Major is the third largest constellation that occupies almost 3.1% of the total sky.
Stars within Ursa Major are worth exploring; we will discuss on this constellation in greater detail on some other day!
The distance of Arcturus from our Earth has been estimated close to 37 light years, which is small when seen from the perspective of the vast expanse of the universe.
For those who are in the northern hemisphere, the ‘arc to Arcturus’ is the way to view it in the night sky in the northeast direction!
A moonless night will certainly help you to locate Arcturus through naked eyes!
Many astronomers believe that Arcturus has originated outside the Milky Way galaxy called a Satellite galaxy, which in the subsequent times amalgamated with the Milky Way. That is why Arcturus and its 52 companion stars have somewhat different motion and trajectory through the Milky Way!
The star has some peculiarity in the sense that it does not appear to be moving with other stars in the Milky Way galaxy. The reason for this is that its movement is in a perpendicular direction.
This means that the star will move out of sight after millions of years for the people of Earth!
Do you have any wild estimate how old Arcturus is!
The star is almost 7 billion years old. This means it is older than our Sun, which is estimated to be as old as 5 billion years. The surface temperature of Arcturus is 4000 degree Celsius, which is almost 74% of that of our Sun.
In the relative term, Arcturus is an aging star in the sense that its major life span has passed. It has spent its stock of hydrogen and now burning helium stacked in its core. For this reason, Arcturus has expanded to become 26 times larger in diameter than that of our Sun.
Because of this expansion, Arcturus looks relatively much brighter!
Arcturus almost matches our Sun in mass! But even then it illuminates 100 times brighter than our Sun. The point is that if you took the Sun as far as 37 light years (the current distance of Arcturus from our Earth), its illumination would be 100 times less than that of Arcturus and would not be visible through our naked eyes at all!
While Arcturus is over 100 times brighter than our Sun, a large part of its light is in infrared wavelengths. It also needs to be noted that Arcturus is less efficient in energy production than our Sun, which has a much higher surface temperature at 5770 degree Celsius. With a large part of its fuel finished, one day Arcturus will end up being a white dwarf.
Arcturus is also known for its speed of movement, which is as high as 122 kilometers per second. Other than Alpha Centauri no other Star moves with such breathtaking speed.
Mythology of Arcturus
It is said that Arcturus is one of the few stars that have a mention in the Bible.
According to Chinese mythology, Arcturus is the main star of the Dragon Constellation. Five centuries back, Arcturus has remained a navigational star for the Polynesians and other people of the Hawaiian Islands.
Chicago and Arcturus
Almost 86 years ago, on May 27, Chicago had opened its Century of Progress Exposition highlighting the progress made by science and technology. This exposition was all about technological innovation and organizers thought it to make a big headline by opening the exposition in a novel way!
Prior to that, in 1893, Chicago also had had an opportunity to host its first big fair called the World’s Columbian Exposition. In 1933, astronomers estimated the distance of Arcturus at 40 light years; this means the lights emitted by Arcturus in 1893 would be reaching to the Earth in 1933. Interestingly, both the expositions had a time gap of 40 years!
In the 1930s, the photocell was a revolutionary and raging device making big headlines across the world!
When light falls on the surface of the photocell, it emits electrons generating electricity.
The organizers of the Columbian Exposition allowed the light to fall onto a photocell via a telescope, which was focused on Arcturus. Electricity generated by this arrangement was used to open the Century of Progress Exposition in 1933.
Is not that amazing and unforgettable for all-star lovers of this world?
And Yerkes Observatory was credited for this novel way of opening the exposition. As a backup, telescopes from the Harvard College Observatory, Allegheny Observatory in Pittsburgh, and the University of Illinois Observatory in Urbana also participated in this wonderful event.
It was undoubtedly a proud moment for over 30,000 people when they witnessed this grand event sitting at the Hall of Science!
And it was a great triumph for science and technology too that made this possible!