The five planets will appear in a line from low in the East to high in the North.
Mercury, Venus, Mars, Jupiter and Saturn were visible early this morning, high in the north to low in the east, Museum Victoria astronomer Dr Tanya Hill said. The remaining planets Neptune and Uranus and the dwarf planet Pluto are not visible with the naked eye, but Dr Hill said the five bright planets have been observed since ancient times. "There are only a few amazing things in the night sky that can be seen without any equipment," Dr Alan Duffy from Swinburne University said.
The viewing window this morning was between 5:30am and 5:40am (AEDT), however stargazers in Melbourne reported a cloudy sky made planet spotting difficult. The times will expand to an hour-long opportunity between 5:00am and 6:00am until February 20.
Dr Duffy suggested finding a clear horizon and a dark sky to witness the celestial arrangement, which will be easiest outside cities, and to try on more than one morning to get the best view.
Dr Hill said Venus, Mars, Jupiter and Saturn have been visible together since the beginning of the year and will now be joined by Mercury, which is transitioning from an evening to a morning object. "At first it will appear quite low to the eastern horizon and of all the planets it is also the faintest, so it will be hard to see to begin with," Dr Hill said. "However, Mercury will continue to rise higher each morning and by early February it will sit just below bright Venus."
The order of the planets will not be the same as their order from the Sun. Starting from the eastern horizon, Mercury (1) and Venus (2) will appear in order, then Saturn (6) followed by reddish Mars (4), with the solar system's largest planet, Jupiter (5) the last one in line.
The line formed by the planets closely follows the path of the sun across the sky, a line called the ecliptic, Dr Hill explained. "This path marks the plane of our solar system, visual proof that the planets, including Earth, all orbit the Sun on roughly the same plane," she said. However, each planet has a different yearly cycle, from Mercury's 88 Earth days to Saturn's 29.7 Earth years, so an alignment is reasonably rare and "essentially a quirk" of the universe, Dr Duffy said.
To help in identifying the planets, Dr Hill said the Moon will travel past each one in turn, beginning with Jupiter on January 28 and ending with Mercury on February 7. The Moon will pass by Mars on February 1 and 2, Saturn on February 4 and Venus on February 6.
Dr Hill said the five planets will be together again in the evening sky in August, but then not until October 2018.