Despite being the 5th largest constellation in the night sky, Hercules is not easily visible. This is because none of its stars are very bright. This means that even light smog or light pollution from the moon or city lights can prevent amateur astronomers from getting a clear view. For the best view of Hercules, you need to get to an area without any artificial lighting, on a moonless night.
First noted by the Grecian-Egyptian scholar Claudius Ptolemy during the 2nd century, the constellation of Hercules is the 5th largest of the 88 modern constellations that are visible in the night sky. Early Greek astronomers called the constellation Engonasin (the kneeler). However, with the influence of Romans, the star formation was attributed to the Grecian-Roman demigod Hercules/Heracles.
The constellation depicts a labor of Hercules standing victorious over the body of the slain dragon Ladon (constellation Draco), with a club in his hand, when stealing the apples of Hesperides. The constellation is surrounded by constellations Leo, Hydra, Draco, and Cancer, all of who depict the victims of Hercules in his various labors, i.e., The Nemean lion, Hydra, the nine-headed snake, Ladon the dragon, and the crab sent by Hera to annoy Hercules. Let us now look at this star formation in greater detail.
Where is the Hercules Constellation Located?
It is extremely exciting for amateur astronomers to view heavenly bodies through telescopes by themselves. However, depending on the hemisphere of the earth, the location of Hercules differs widely.
When to See it
The first step is make sure that you are stargazing somewhere in between latitudes 90 degrees North to 50 degrees South, as the constellation is only visible from this region. Another important thing to note is that Hercules is visible in the northern hemisphere only from April to November, and from June to September in the southern hemisphere.
How to Find Hercules in the Northern Hemisphere
- During April, one can notice Hercules on the north-eastern horizon at around 11 pm, which will slowly rise and come directly overhead by around 4 am. After this, it will continue on its way and set near the northwest horizon.
- During May and June, it will rise from the east or northeast horizon at around 10 pm to set in the northwest.
- During July and August, the constellation will appear directly overhead after sundown, before disappearing in the northwest.
- From September to November, it will appear towards the west after sundown, and will dip to the northwest within a few hours.
How to Find Hercules in the Southern Hemisphere
It is important to note that the Hercules constellation will appear upside down in the southern hemisphere.
- In June, the constellation will rise up from the northeast horizon, and will move across the sky to the north for 6-7 hours before setting in the northwest.
- During the month of July, Hercules will be visible after sundown moving from the northeast to the northwest and setting at approximately midnight.
- In September, the constellation appears for 3-4 hours after sundown, moving from the north to the northwest.
Note: It is usually difficult to recognize Hercules from urban locations, as the light and smoke pollution decreases visibility, and one may see only 1-2 stars of the constellation.
How Many Stars are there in Hercules?
There are 14-15 stars which are usually considered to form the basic shape of this constellation. Apart from these, another 15-16 stars are prominent enough to be seen by the naked eye on clear nights. There are also around 3000 stars that are not visible with the naked eye, but have been identified and named with the help of advanced telescopes. However, with the star clusters M13 and M92, the number of stars goes into hundreds of thousands.
- Rasalgethi/ Alpha Herculis is the alpha star of the constellation. It is a red super giant star, with variable brightness of 3.1 to 3.9 magnitude, which forms the head of the figure. It is located 380 light years away from earth. Small telescopes show that Rasalgethi is a double star, with a companion of around 5.3 magnitude. However, when viewed with advanced telescopes, this companion star is actually revealed to be two stars in a binary system. Alpha Herculis is said to have a diameter that is 400 times more than that of our Sun.
- Kornephoros/Beta Herculis forms the right shoulder of Hercules, and is a yellow giant star, 139 light years away from the earth. With a brightness magnitude of 2.7, it is the brightest star in Hercules.
- Marfik/Kappa Herculis is a yellow giant below Kornephoros, designating the elbow of the figure. Viewed through a telescope, this is also a double star. Together, both stars have a combined brightness of 5 mag.
- Kajam/Omega Herculis is a blue main sequence star further along the arm, that represents the club of Hercules. It is 250 light years away from earth and has a brightness of 4.5 mag.
- Sarin/Delta Herculis is another star located on the other shoulder of Hercules. Through telescopes, one will notice that it is a binary system of two white main sequence stars around 79 light years away. Together, they have a brightness of 3.1 making it the third brightest star in the constellation.
- Maasym/Lambda Herculis is an orange giant star around 370 light years away with a brightness of 4.4 mag, and is the wrist of the figure.
- Epsilon Herculis, Zeta Herculis, Eta Herculis, and Pi Herculis are the four stars which make up the torso of Hercules. Of these, Zeta Herculis is a binary star system.
Planetary System: There is a group of 15 stars in Hercules, that have planets revolving around them, most of which are gas giants, many times larger than Jupiter. However, star HD156668 has a planet, thrice the size of earth, which might support life. This star is 78 light years from us.
Deep Space Objects
- M 13, also known as the Hercules Globular Star Cluster, is the brightest globular star cluster in the north sky. Located approximately 22,000 light years from earth, it has a diameter of around 150 light years, and contains around 300,000 stars. Although visible by the naked eye on a clear night, it is best viewed through a telescope. However, to see it in all its glory, one must check out the images taken by the Hubble Telescope.
- M 92 is a smaller and dimmer globular star cluster. It has a brightness magnitude of 6.3 and is approximately 26,000 light years away.
- NGC 6210 is a planetary nebula, which despite its name has no planets. It was only given this name because of the planet-like appearance from small telescopes. It is located 6,500 light years away, and has a magnitude of 9.5, making it visible through small telescopes.
- IC 4593 is another planetary nebula much farther away than NGC 6210, and is difficult to view through small telescopes too, because of its poor brightness at 10.7 mag.
- Abell 2151 is a huge galaxy cluster, that can be viewed by telescopes, near Marfik. The galaxy cluster is more than 400 million light years from earth, and contains around 200 galaxies, many of which are merging.
The Tau Herculids are the only meteor shower taking place in this region, which usually occurs from May 19th to June 19th.
- The nearest star of the constellation GJ 661 is only 21 light years away from earth, but it is barely visible due to its extremely low brightness magnitude.
- Dr. Carl Sagan and Dr. Frank Drake created a message of binary digits called the 'Arecibo Message' in 1974. It was sent towards M 13, with the hope of communicating with beings who might exist somewhere in the star cluster. However, even with the frequency of over 2,000 MHz, it will take around 25,000 years for the message to reach those stars, and another 25,000 years, for the replay to return, if there is any.
Besides the above phenomenon, the Hercules constellation is of special interest to astronomers, due to high levels of X-rays emitted from this region. There are a lot more cosmic secrets to be uncovered by scientists from this constellation, including the secrets behind the creation of the universe.