The original Discs from Japan

Southern Hemisphere

The starry sky of the southern hemisphere, which includes Australia and New Zealand, is quite different from what can be seen from countries such as Japan in the northern hemisphere.

Constellations peculiar to the southern hemisphere cannot be seen from most parts of Japan. While the Southern Cross is visible only from the southern hemisphere, constellations such as the Big Dipper or Cassiopeia are only visible from the northern hemisphere. Still, many constellations are closer to the equator and can be seen from anywhere. However, their position varies greatly and they look upside down from the opposing hemispheres.

The star's movement also appears different in the two hemispheres. In the north, the stars appear to rotate anticlockwise around the North Star. And while they appear to be rotating clockwise in the south, there is no bright star at the south celestial pole. As in the north, stars rise in the eastern sky and set in the western sky. But since the equator is in the north, the movement of stars, Sun and Moon seems to be opposite the movement in the northern hemisphere leaving first-time visitors with a magical impression.

Even the appearance of the Milky Way differs between opposing hemispheres. In the south, the central part of the Milky Way rises high in the sky in an exceptionally beautiful manner. Especially in abandoned places with low light pollution, the Milky Way presents a myriad of mysterious dark nebulae. Their three-dimensional becomes apparent and the depth of the universe can be felt first-hand. It is highly recommended to take some time to watch the Milky Way upon the next trip to the southern hemisphere. The view is best between April and September.

Furthermore, the seasons are opposite in the north and south. While the northern hemisphere experiences winter from November to March the southern hemisphere enjoys summer during that time. Hence, the constellation of the winter, Orion, is no longer a freezing Orion, but becomes a sweating Orion. On the other hand, the southern hemisphere has winter from May to September. Summer constellations, such as Scorpius, are therefore better observed during winter in the southern hemisphere.

Comets

The famous Halley's Comet approaches the sun every 76 years, the next time in the summer of 2061. However, it is not possible to predict when most other comets will come back. The discs shows a review of the of the comets that decorated our sky for a few days between 1965 and 1997. The disc is based on photographs of the comets back at the time they were visible, while reproducing them at their original position. However, the size and brightness have been increased in order to enhance the viewing experience. The photographs used for this discs were provided by Akihiro Fuji.

Comet Ikeya–Seki

The Comet Ikeya–Seki has been discovered almost simultaneously by Japan's famous comet hunter, Kaoru Ikeya, from Shizuoka and Tsutomu Seki from Kochi. After its approach to the sun, it drew a long tail into the sky's east shortly before dawn. The photograph of the comet has been taken on 4 November 1965, when the comet's head as in Corvus.

Comet Bennett

The comet was discovered by John Caister Bennett from South Africa. It became a large comet of magnitude -3, which can be seen with the naked eye. Due to the strong brightness, it even appeared clearly visible in the night sky of the city, decorating the east sky before dawn. The photograph of the comet has been taken on 4 April 1970, when the comet's head was around the front foot of Pegasus.

Comet West

The comet was discovered by Richard M. West of the European Southern Observatory. Because the comet's nucleus split into four fragments, a huge amount of dust was released, creating a beautiful, long tail. The impressive photograph of the comet has been taken on 5 March 1976, when it was rising in the east, shortly before dawn.

Comet Halley

The British astronomer Edmond Halley first determined the comet's periodicity and predicted its approach of the sun approximately every 76 years. Comet Halley's last approach was in March 1986 when the Soviet and the European Space Agency launched spacecraft to investigate the comet's nucleus. The photograph of the comet has been taken on 14 March 1986 by ESA's Giotto spacecraft.

Comet Hyakutake

The Japanese amateur astronomer Yuji Hyakutake from Kohjima prefecture discovered Comet Hyakutake. The comet approached the sun closer than any other planet in the last 200 years. The photograph was taken on 26 March 1996 when it crossed the Big Dipper in the direction towards Virgo approaching the North Star.

Comet Hale–Bopp

Alan Hale and Thomas Bopp separately discovered Comet Hale–Bopp before it became visible to the naked eye. The comet was the most widely observed of the twentieth century as it was one of the brightest for decades. The blue gas tail and the yellow dust tail formed a V-shape. The photograph was taken on 1 April 1997.

Universe with Galaxies

The night sky keeps a lot hidden from the naked eye. A myriad of colourful nebulae, star clusters and galaxies far away can only be discovered using telescopes.

The famous Orion Nebula is visible with the naked eye as the middle "star" in the sword of Orion, formed by the three stars located south of Orion's Belt. The nebula is a stellar nursery where new stars are being born, there are approximately 700 stars in different stages of formation. The Orion Molecular Cloud Complex extends throughout the constellation of Orion and also comprises the Horsehead Nebula. This nebula is the easternmost "star" of Orion's Belt, where a dark cloud of dust and gas shows the silhouette of a horse's head. The further vicinity comprises the Pleiades, which in Japanese are known by the name Subaru and which are a star cluster of middle-aged hot blue stars in the constellation of Taurus.

The universe not only hosts nebulae where stars are born, but there are also nebulae which are formed by the remnants of former stars. The Ring Nebula in the Summer Triangle is a planetary nebula in the constellation of Lyra, which is made up of expelled gas by a red giant star before becoming a white dwarf. The Veil Nebula in the constellation of Cygnus has been formed when a supernova twenty times as massive as the sun exploded. The supernova remnant is so large that various arcs of the nebula have their own name. There Western Veil, the Eastern Veil and the Pickering's Triangle are the main three components forming the Cygnus Loop.

Messier 13 is a cluster of several hundred thousand stars in the constellation of Hercules. The stars in the Hercules Globular Cluster are more than a hundred times denser than the stars in the neighbourhood of the sun. When two stars of the cluster collide, they produce new stars called blue stragglers.

The previous celestial objects were all within our galaxy. But there are also other galaxies, such as the Andromeda Galaxy. The spiral galaxy is about 2.5 million light years away from the Earth. It is the closest galaxy to the Milky Way and thus is among the brightest Messier objects and visible to the naked eye on moonless nights in the autumn sky.

The celestial bodies cannot be seen as clearly with the naked eye as depicted. However, it is very impressive to see their appearance in a science museum or at an observatory with a large telescope.

Starry Night with Four Seasons

The sky of the four seasons shows the northern hemisphere. It displays the sky as it appears when looking south between eight in the evening and midnight in each season.

The spring sky shows the Big Dipper. It seems as if the Big Dipper’s curve is placed above the red Arcturus and Virgo's white star Spica. The curve of the asterism is well visible in the sky and acts as a sign that temperatures are about to rise again.

Summer brings many opportunities to go out to discover the stars in the sky on the sea or on top of a mountain. Between twilight and late midnight, the Summer Triangle ascend in the sky. The asterism is defined by Deneb in Cygnus, Vega in Taurus and Altair in Cancer. The dark areas of the sky show a light band, the Milky Way, passing through the large triangles. The intersection of the Milky Way and the southern horizon shows Scorpio in which its bright, red star Antares is shining.

By the time the trees turn red and yellow, the autumn constellations will appear. However, there are not many bright stars. While the Square of Pegasus is made up of Pegasus’ four stars, Fomalhaut shines in southern Pisces.

The cold winter makes astronomical observations outdoors a freezing task. Above the snow-covered bare winter trees, the Winter Triangle can easily be spotted. The asterism is formed by the three stars Betelgeuse in Orion, Sirius in Canis Major and Procyon in Canis Minor. The gorgeous starry sky is rounded up with the bright stars Pollux in Gemini, Cappella in Auriga and Aldebaran in Taurus.

Earth in Space

What would you see if you fly away from Earth with a spacecraft and look back? The view would be similar to the view of the Earth from the Sun (with the Earth’s size enlarged considerably).

Looking at the Earth from the Sun

The heat near the sun would be too galactic to even approach it. But how would space look like? The stars and the Milky Way would still look the same as viewed from Earth. This makes sense as the Earth is orbiting the Sun and the stars look the same in winter and summer as well. However, the planets will appear at different positions and in addition to the five planets which are visible by the naked eye, there will also be the Earth, making them six: Mercury, Venus, Earth, Mars, Jupiter, Saturn.

Seen from the Sun, the Earth looks as bright as Venus from Earth and is about 100 times smaller than the Sun from Earth. For best visibility, the Earth has been enlarged 10 000 times, so it can be enjoyed properly while floating in space. The size of the Earth corresponds about to what is visible from a geostationary satellite such as the Japanese meteorological satellite Himawari, which orbits the Earth at an altitude of 36 000 km.

Path of the Earth (Ecliptic)

When observed from the Sun, the Earth follows ecliptic. From a heliocentric point of view, the Earth follows the same path. Throughout the year, the Earth passes through the zodiac. This belt is made of the twelve well-known constellations: Aries, Taurus, Gemini, Cancer, Leo, Virgo, Libra, Scorpio, Sagittarius, Capricorn, Aquarius and Pisces.

On 20 April, the Earth will be appear to be in Virgo when observed from the Sun. The Sun, however, would be at the boundary between Pisces and Aries. This would be the start of the sixth solar term, called Kokuu for Grain Rain in Japanese, in the traditional East Asian calendar, in which the year is divided into 24 solar terms.

Moon Phases

Throughout the month, the Moon appears in many various forms. While the Moon is spherical like the Earth, the portion visible from Earth is not always fully illuminated by the Sun. Therefore, the same Moon appears as New Moon, Crescent, Half Moon, Gibbous or Full Moon over time.

Waxing Crescent

When New Moon is considered the first day, the crescent will be first visible on the third day. It will appear after sunset in the western sky for a few hours, shortly before its own disappearance, the moonset.

First Quarter (Half Moon)

After four to five days of crescent, the moon will be half-visible. This marks the first quarter of the lunar phase. The half moon is always exactly south at sunset and vanishes around midnight in the west.

Full Moon

When the Moon is opposite the Sun as observed from Earth, it will appear fully illuminated. During the full moon, the Sun is on the same side as the Earth as observed from the Moon. In the lunar calendar, used in ancient Japan, the fifteenth day of the eight lunar month is the day of Mid-Autumn-Festival. While new moon is always the first day, the full moon falls the between the fourteenth and sixteenth day of each lunar month. During full moon, the Moon is opposite the Sun and thus rises in the east around sunset and sets around sunrise. With each day, the Moon rises about one hour later and will gradually show less of its illuminated side.

Waning Gibbous

The seven days following full moon, a waning gibbous moon can be observed. Each day, it raises later until it eventually becomes a half moon again. This time called the last quarter as it marks three third of the lunar phase. At this point, the Moon rises around midnight and is south at sunrise. It can still be seen in the morning before its moonset around noon.

New Moon

About fifteen days after full moon, the Moon is on the same side as the Sun as seen from Earth. Almost none of the illuminated side can bee seen and sunrise and moonrise almost coincide. In rare cases, the Sun, Moon and Earth align in one line and a solar eclipse occurs. The Moon appears as a black shadow passing in front of the Sun.

Solar System

Sun

The Sun is the Solar System’s only star, providing energy and gravity to all the other planets. With 1 390 000 km, its diameter is 109 times the one of the Earth.

Mercury

The planet Mercury is the closest to the sun. Its surface is dominated by craters and it resembles the Moon. During one orbit around the Sun, Mercury rotates one and a half times around its own axis.

Venus

The planet Venus is nicknamed "morning star" and "evening star". It is covered by a substantial atmosphere with and is the hottest planet in the Solar System.

Earth

The Earth is the third planet. Its liquid hydrosphere is unique in the Solar System and it is the only celestial body on which the existence of life has been confirmed.

Moon

The Moon is the Earth’s only permanent natural satellite with a diameter of about one quarter of the Earth’s. Most likely, it has been formed not long after Earth during an impact of the Earth with another planet.

Mars

The fourth planet, Mars, is slightly smaller than Earth and has a red colour from iron oxide in its soil. Spacecraft missions showed that there was once liquid water on its surface.

Jupiter

The biggest planet, Jupiter, is largely composed of hydrogen and helium and rotates around its own axis at a high frequency. The Great Red Spot is an anticyclonic storm resembling a typhoon.

Saturn

The sixth planet, Saturn, is a gas giant with a low density. It is easily distinguished by its ring, which can be seen with a telescope and which is made of ice and rock particles.

Uranus

The light blue gas planets has been discovered in 1781. With an axial tilt of over ninety degrees to the ecliptic, it orbits the sun on its side, once every 84 years. There are several narrow rings.

Neptune

The eight planet, Neptune, is the furthest from the Sun. The gas planet with its blue colour has been discovered in 1846 and orbits the Sun once every 165 years.

Northern Constellations

The twelve constellations of the zodiac are marked with a ★.

Aries ★ This mid-sized constellation is located south of Andromeda and Triangulum. In Hellenistic astrology, Aries represents the golden ram of Greek mythology.
Taurus ★ The constellation includes Aldebaran, a bright red star west of Orion’s three stars. The Pleiades are located in this constellation.
Gemini ★ The twins Castor and Pollux of the Greek mythology are standing shoulder to shoulder. The stars named after them represent their heads.
Cancer ★ This mid-sized constellation represents a crab. The constellation consists of five faint stars and is home to the Beehive Cluster in its centre.
Leo ★ The represents a lion. It is composed of flipped question mark with Regulus as its dot, representing the front legs, and Denebola for the end of the tail.
Virgo ★ The second largest constellation resembles the letter Y. It can easily be found through its brightest star Spica.
Libra ★ The constellation located west of Scorpio is the only of the zodiac representing an instrument. The weighing scales are held by Astrea, the Roman goddess of justice.
Scorpio ★ The S-shaped constellation contains red, bright star Antares. In Greek mythology, the scorpion killed Orion with its venomous stinger.
Sagittarius ★ The constellation lies deed inside the Milky Way and is home to many nebulae and star clusters. In Greek mythology, it is associated with the centaur Chiron.
Capricorn ★ The stars of this constellation are all faint and are arranged as an inverted triangle. In Greek mythology it is associated with a creature that is half goat, half fish.
Aquarius ★ In Greek mythology, it shows beautiful Ganymedes, prince of Troy, pouring water out of a bottle. The stars aligned in two arrows represent the flowing water.
Pisces ★ The stars form two joining strokes (<) representing two fish. In Greek mythology, the goddess of beauty, Aphrodite and her son Eros transformed into fish during an escape.
Ursa Major ☆ The seven bright stars form the asterism Big Dipper. In connection with the surrounding stars, the Big Dipper forms the tail of the Great Bear.
Ursa Minor ☆ The Little Bear is formed by seven stars and resembles the Big Dipper. The stars are not as bright as its partner, Ursa Major. The tail ends with Polaris, the North Star.
Lyra ☆ This small constellation can be seen on the edge of the Milky Way. It is home to Vega, one of the night sky’s brightest stars.
Aquila ☆ The brightest star or Aquila is Altair. In the East Asian Tanabata legend, Vega represents the weaver girl Orihime, while Altair represents the cowherd Hikoboshi.
Cygnus ☆ This constellation is home to the asterism Northern Cross. Together with the surrounding stars, it displays a swan spreading the wings, with Deneb at its tail.
Cassiopeia ☆ The W- or M-shaped constellation can easily be found. Cassiopeia is the queen of Aethiopia and the mother of Princess Andromeda, also a constellation.
Canis Major ☆ The constellation of the bigger dog contains Sirius. This is the brightest star of the night sky and was described as "burning" or "flaming" in Greek literature.
Orion ☆ The winter constellation is named after a hunter in Greek mythology. It features the red and blue supergiants Betelgeuse and Rigel and the three stars in between.

Southern Constellations

Constellations in the Southern Hemisphere

When travelling south from Japan, the Southern constellations start to rise on the horizon. While they are not visible from Japan, the more south you go, the more of them become apparent. Most of them have been established by Europeans during the Age of Discovery (15th to 17th centuries). Not few of those are creatures of the Southern Hemisphere as well as equipment of that time. They are thus constellations without any myths.

Argo Navis (Ship Argo)

The name is derived from the ship Argo in Greek mythology. Argo Navis was sailed by Jason and the Argonauts and has been a great adventure. Since the constellation was incredible big, it has since been divided into four parts: Vela, Pyxis, Puppis, and Carina.

Centaurus

This large constellation depicts a centaur, a creature that is half human, half horse, attacking Lupus in front of it with a spear. It is similar to the zodiac constellation Sagittarius, which is also named after a centaur. The front of Centaurus's foot consists of Alpha Centauri, the closest star system to the Sun, about four light-years away.

Crux

It is commonly known as the Southern Cross, but correctly called Crux. The constellation of four bright stars on the southern end of the Milky Way is among the most easily distinguished. While there is no bright star at the celestial South Pole, extending the long side of the cross by 4.5 times gives the position with a good accuracy.

Constellations of Creatures

Johann Bayer from Germany published Uranometria, in which he extended the classical Greek constellations by additional ones. These constellations depict creatures living in the Southern Hemisphere, such as Pavo, Phoenix and Chamaeleon. The appearance of those animals must have left a lasting impression on the European discoverers who saw them for the first time.

Constellations of Tools and Utensils

The constellations depicting tools and instruments such as Octans, Fornax, Horologium and Antlia were established by the French astronomer Nicolas-Louis de Lacaille. Most of them are difficult to spot as they are made up of faint stars.