Scorpius star map
Copyright: Melbourne Planetarium
Highlights of the tour
- a supergiant star
- galactic clusters
- globular clusters
- double stars
- the strongest X-ray source
The constellation of Scorpius can be found in our evening skies in winter. These stars are directly overhead during August at about 9:00 pm. In Greek and Roman tradition, the hook shape made by the brightest stars represented the scorpion whose sting caused the death of the great hunter Orion. A number of temples at Delphi and Corinth were thought to be aligned to the rising of its brightest star, Antares. The symbol of the scorpion was also one of the oldest of the Egyptian hieroglyphics and Antares was the sacred star of the goddess Isis. In ancient China this constellation was known as the Azure Dragon and Antares was the Fire Star.
Stop 1
The stars you can see here form the head of the Scorpion. The brightest is Beta Scorpii, the one to the east is Nu Scorpii, the other two are Omega 1 and 2 Scorpii. Nu is actually a quadruple star system made of two pairs of stars. You may just see the brightest star of each pair in very good binoculars. The faint fuzzy blob to the south is M80, a bright globular cluster of stars. These are relatively old. It is thought that such clusters were formed early in the life of the galaxy, about 12 - 13 billion years ago. This group of stars is about 50 light-years across. It is estimated that the stars in this cluster are so close together that 2 700 star collisions would have occurred since the cluster was formed. Near Beta Scorpii, but invisible to us, is Scorpius X-1, one of the strongest X-ray sources ever detected. The X-rays are coming from a neutron star, a star that has collapsed into a tiny but extremely dense object that is spinning rapidly.
Stop 2
In the center of your field of view is Antares. The name Antares means 'the rival of Mars' because the red colour of the star is similar to the planet Mars. This star is also known as the heart of the Scorpion. It is a supergiant star about 700 times the size of the Sun, but although it is large in size its mass is only about 10 or 15 times that of the Sun. It is 9 000 times more luminous than the Sun and its surface temperature is a cool 3 000°C, however it lies at a distance of 520 light-years from Earth. Antares has a small companion star not visible in binoculars. The two stars are embedded in a vast reddish cloud of gas and dust about 5 light-years in diameter.To the south-east of Antares is Tau Scorpii. To the north-west is Sigma Scorpii, which is thought to be about 900 light-years away. Between Sigma and Antares is M4, another globular cluster of about 10,000 stars. This is one of the largest such clusters and it is also thought to be one of the closest, at an estimated distance of 6,200 light-years. This cluster is moving away from us at a speed of 62 kilometres per second.
Stop 3
In the north of your field of view is Epsilon Scorpii. This star marks the beginning of the tail of the Scorpion and is one of the closest stars in the constellation, at only 65 light-years away. South of Epsilon is Mu Scorpii, a double star. The two stars are locked together by their mutual gravitation, even though they are separated by almost a light-year. There are also a few galactic clusters, NGC 6281, NGC 6242 and NGC 6268 to be found in this area on a very clear night. These sorts of clusters are mainly found along the Milky Way.
Stop 4
Of the two brightest stars in your field of view Zeta Scorpii looks like another double star. In fact there is no real association between these two stars as the brightest is only 155 light-years away, while the other is nearly 6,000 light-years away. You should notice a difference in colour between these stars, the brighter is orange while the fainter is white. This denotes a difference in temperature - the orange star is cooler. The other bright star in your field of view is Eta Scorpii, close at only 50 light-years.
Stop 5
The southernmost bright star in your field of view is Theta Scorpii and nearby is NGC 6388, another globular cluster about 35,000 light-years distant. To the north-east is Iota Scorpii. While this star may not look spectacular it is another supergiant about 60,000 times more luminous than the Sun, but over 3,000 light -years away.
Stop 6
The Scorpion's sting is made of two stars at the south-western edge of your field of view, Upsilon and Lambda Scorpii, known also by their Arabic names Lesath and Shaula. Again, these stars are now really close, even though they appear so from our viewpoint. The two faint fuzzy patches in the north-east are M6 and M7, two of the largest and brightest galactic clusters.