Solar System Trail
Navigate the solar system from the sun to the outer planets by following the bike and walking trail on the City of Port Phillip’s foreshore.
In 2008 artists and scientists constructed a model of our solar system to a scale of one to one billion between St Kilda and Port Melbourne. Instead of navigating 4.5 billion kilometres from the sun to Neptune, and 5.9 billion kilometres from the sun to Pluto, you only travel 4.5 kilometres and 5.9 kilometres. The foreshore has always been a superb location to view the sun setting on the western horizon. Port Phillip Bay’s crescent shape is perfect for a model where the ‘sun’ can be viewed from every one of the nine model locations.
Open to the elements, many of the artworks are temporary so you’ll always see something new. Keep your eyes open as you’re sure to make your own special discoveries along the way.
The Sun is a star, one of 300 billion in the Milky Way galaxy and is about five billion years old. All life on Earth depends on the light and heat from the Sun. It is 110 times the Earth’s diameter. It is has an estimated surface temperature of 5,800C and a core temperature of 20,000,000C. It is a middle-aged star, at least 4.6 billion years old but has an expected lifespan of 10-12 billion years. The Sun contains 99.86% of the total mass of the solar system and its gravity holds all of the planets in orbit.
Mercury is the closest planet to the Sun. Like the Earth’s moon it is a grey barren world covered in a thick layer of dust and heavily scarred with impact craters. These craters never erode because of the lack of atmosphere. Mercury at times can be seen close to the Sun, just after sunset or just before sunrise. The ancient Greeks believed it to be two separate objects: Apollo in the morning and Hermes in the evening.
Venus is similar in size to Earth. It is a hellish world with crushing pressures, scorching temperatures and sulphuric acid rain. The Russian Venera 13 spacecraft survived only 2 hours and 7 minutes after arrival. Venus shines brilliantly because of a thick atmosphere of carbon dioxide. The ‘evening’ or ‘morning’ star, as it is often called, appears soon after sunset or not long before sunrise. Twice in every 120 years Venus passes or ‘transits’ between the Earth and the Sun, including in1874, 1882, 2004 and 2012. The Transit of Venus played a major role in Australian history. Captain James Cook, whose statue stands east of St Kilda Pier, claimed Terra Australis for the British crown in 1770 when, after observing the 1769 Transit at Tahiti, he was directed to search for the ‘great southern land’\"
Earth is unique, the only place we know of in the Solar System and galaxy that supports life. It lies within the Sun’s ‘habitable zone’ with liquid water on its surface and with life-supporting concentrations and amounts of chemicals. The core of iron is covered by a thick mantle of liquid rock. Continents and oceans float on the thin outer crust of solid rock. The atmosphere is 78% nitrogen, 21% oxygen, a little carbon dioxide and other gases. The moon is about one quarter the diameter of the Earth. Scientists believe it was formed after an object the size of Mars collided with the Earth when it was very young
Mars has inspired curiosity and imagination for thousands of years, including theories of advanced civilisations however there is no evidence of life on the planet. Its famous red colour is due to iron oxide on the surface. The tilted axis creates seasons and there are often violent dust storms. Its spectacular features include the immense volcano ‘Olympus Mons’ (27km high) and the vast canyon ‘Valles Marineris’ with a length about the distance from Sydney to Perth (4000km). The two moons, Phobos and Deimos, are actually small captured asteroids
Jupiter contains more than twice as much material as all the other planets combined. The atmosphere is thousands of kilometres deep with hydrogen, helium, methane and ammonia. It has at least seventy moons and a faint ring system. Io, one of Jupiter’s largest moons, is the most volcanic planet or moon in the Solar System. Europa has an ice crust above an ocean of water. Ganymede, the largest moon in the Solar System, is made of rock and ice. ‘The Great Red Spot’ is a cyclonic storm up to three times the Earth’s diameter, which has been observed for at least 300 years.
Saturn, one of the four gas giants, is famous for its spectacular system of rings made from billions of icy rocks, sized from small grains to kilometres wide. It has about sixty moons. Titan, the largest, is the only moon in the Solar System with an atmosphere (nitrogen). It also has lakes of liquid methane discovered by the Huygens Probe which landed in 2005.
Uranus lies on its side causing it to ‘roll’ around the Sun. Strangely, its equator has been tilted more than ninety degrees to its orbit. Perhaps early in its history it collided with a huge unknown object. In 1781 it was the first planet since ancient times to be discovered (by William Herschel). The atmosphere is mainly hydrogen with some helium and methane. Of its thirty or so moons, Titania, Oberon, Umbriel and Arial are over 1000 km in diameter. It has a faint ring system discovered in 1977 when it moved in front of a star
Neptune is a cold distant gas giant. Through a telescope it is bluer than Uranus because it has more methane. Giant storms whirl through its atmosphere with the fastest winds recorded in the Solar System, up to 2,400 km/h. One storm, nearly as large as Earth, circles the planet every eighteen hours. In 1989 the Voyager 2 spacecraft discovered eleven small moons and a faint ring system. Triton is the largest (2,700km in diameter) as well as being the coldest moon in the Solar System. Geysers of nitrogen spew from its surface
Pluto, discovered in 1930, is a tiny world smaller than the Earth’s moon. Charon, one of its five moons, is half the size of Pluto. Beyond Neptune are tens of thousands of asteroids of ice and rock left over from when the planets were formed. This asteroid belt is called the ‘Kuiper Belt’. In 2005 a Kuiper Belt Object (KBO) larger than Pluto was located and named Eris. Now we realise that Pluto is just one of these large asteroids or ‘Dwarf Planets’. The New Horizons spacecraft reached Pluto in July 2015, after a nine year voyage, to study Pluto, Charon and other KBO’s. Part of Pluto’s orbit can be closer to the Sun than Neptune.