The Milky Way (天の川)

The Milky Way is a nebular cluster like a shining belt crossing the night sky. It is also called a Galaxy.


The glittering belt of the Milky Way covers the celestial sphere, and makes diurnal motion together with the fixed stars in it. The Milky Way is a cluster of trillions of fixed stars. The solar system including our planet is a part of the Galaxy (called 'the Milky Way Galaxy'), and the Milky Way looks like a belt covering the celestial sphere because we see the Galaxy from the inside. The center of the Milky Way Galaxy is situated in the direction of the Archer.

The Galaxy' means the Milky Way, while 'galaxy' is a term used to apply generally to other similar heavenly bodies.
The Milky Way Galaxy as a heavenly body that is sometimes distinctively called 'the galactic system.'
"The Milky Way" implies 'the Garaxy' or 'the galactic system,' depending on the context.

In Japan, every summer and winter the Milky Way appears above us across the night sky from north to south. We can see the Summer Triangle in summer and the Winter Triangle in winter twinkling across the Milky Way. And because there also exist many other stars around the Milky Way, the night sky in summer and winter is full of stars, in contrast, in spring and autumn, few notable constellations exist in the night sky.

Incidentally, there exist some dark areas from place to place in the Milky Way like sandbanks in a stream, and this is not because there are no stars in the area, but because dark nebula conceal stars behind itself.


The story of the Milky Way in Greek mythology is explained below:
Zeus wanted to let Hercules, a son between himself and Alkmene, suck the breast of his divine wife Hera in order to make Hercules immortal. But jealous Hera hated Hercules, so she would never let him suck her breast. So Zeus thought out and implemented a plan and he got Hera to take a sleeping pill and that allowed Hercules suck her breast while she was asleep. And then, Hera woke up and was surprised to find Hercules sucking her own breast, so she shook off Hercules, and her milk spilled. And this milk became the Milky Way, they say. The nebular cluster was named Milky Way after this myth.

The legend of the Tanabata Festival, handed down in East Asia in Japan and China, says it is the Milky Way that separates the Weaver Star (the Lyre's Vega) and the Cowherd Star (the Eagle's Altair). They were in love with each other, but God found fault with them, so thereafter they got to meet only once a year on July 7, crossing the Milky Way. For details, please refer to the article "Tanabata."

Stories and Events about the Milky Way

In "Journey to the West," Jade Emperor appointed Zhu Bajie (Pigsy) to Marshal of Heaven, who took control of the Milky Way.

In the "Manyoshu" (Collection of Ten Thousand Leaves), there exists a Japanese poem composed by OTOMO no Yakamochi about the Milky Way, and he wrote about the Milky Way in the Chinese characters "天漢," which reads "Amanogawa" in Japanese.

In Mimasaka City, Okayama Prefecture, 'the Milky Way Fire Festival' is held every summer. In the festival, you can see powerful arm-held fireworks and the elegant ceremonial fires lit on the surface of a mountain in the shape of the Chinese character of "天" - this reads "ten" in Japanese - which means "Heaven."

How to Watch the Milky Way

The light of the Milky Way is so faint that you will have difficulty finding it, if the light is affected by the moonlight or the light pollution of artificial lights from the ground. In Japan, from the 1970s, after a period of high economic growth, places where the Milky Way could be seen became few. To watch the Milky Way, you should look for the clear sky on a moonless night from an altitude as high as possible ar from urban areas. For details, please refer to the article on "Astronomical observation."

You can see the Milky Way throughout the year, and the light of the Milky Way in summer is relatively strong and easy for you to find out, since the center of the Milky Way is situated in the direction of the Archer, a summer constellation. To the contrary, the light of the Milky Way in winter is so faint that you will have difficulty finding it.

[Original Japanese]