The two bright stars marking the location of the Southern Cross are called the Pointers. Alpha Centauri, the one that appears furthest from the cross, is the closest star to the Sun at a distance of 4.3 light years from Earth. On the other hand Beta Centauri, the other Pointer star, is 392 light years from us.
The pointer stars. Photo Nick Lomb
The Southern Cross gives us an easy means of finding south on any clear night. Extend its long axis by four and a half times its length to reach a point known as the South Celestial Pole. South is the point on the horizon directly below the pole.
How to find south using the Southern Cross. Chart Nick Lomb
The stars of the Cross all appear to be at the same distance but that is not the case. Like the stars of all constellations, they are physically far apart: the closest star to us in the Cross is Gamma at a distance of 88 light years, while the furthest star Delta is at 364 light years distance.
The Southern Cross. Photo Nick Lomb
Today is the anniversary of the birth of the first Astronomer Royal John Flamsteed in 1646 in Denby (near Derby), Derbyshire, England. Flamsteed took charge of the newly built Greenwich Observatory in 1675 and began plotting star positions. His catalogue of 3000 stars was published after his death.
Flamsteed House at Greenwich. Photo Nick Lomb
Date: 1 September 2014
Time: 6:30pm (followed by members presentations)
Place: Sydney Observatory ‘Discovery Room’
John Webb leads the observational work at UNSW using high resolution spectroscopy of quasars to search for variations in the fundamental constants of Nature.
New observations are hinting at departures from standard cosmology. It is possible that the so-called “Cosmological Principle”
is only a good approximation to reality and that the universe may be more complex (and even more interesting) than previously thought.
John will summarise recent observations and describe how we might confirm (or refute) these ideas with more data from the world’s best observatories.
Below Spica, the brightest star of Virgo the Maiden, is the star Porrima, the name of which means the goddess of prophecy. Porrima, also in Virgo, is a double star 38 light years away. The two components circle each other every 170 years.
The constellation of Virgo with the position of Porrima indicated. Chart drawn with Stellarium
If the sky is clear it maybe worthwhile rising early tomorrow morning as the two brightest objects in the night sky apart from the Moon, Venus and Jupiter will be close to each other. Separated by less than a moon-width, the two planets will be low in the east in the brightening dawn sky.
Venus and Jupiter on the morning of 18 August 2014. Chart Nick Lomb
These are the 13 constellations that the Sun passes through during the course of a year. Looking from west to east in the early evening the following zodiac constellations are visible: Virgo, Libra, Scorpius, Ophiuchus, Sagittarius, Capricornus and Aquarius.
The zodiacal constellation of Libra the Scales. Chart made with the help of Stellarium
Spica, the brightest star in the constellation of Virgo the Maiden, is high in the west. Astronomers have found that it is made up of a pair of stars whirling around each other every four days.
An artist’s impression of the two stars of Spica. Courtesy Manuel Perez de Lema Lopez
The constellation of Virgo the Maiden is high in the western sky in the early evening. According to one legend the constellation represents the daughter of the harvest goddess Ceres. Thus Virgo is usually pictured with a palm branch in her right hand and an ear of wheat in her left.
Virgo in the August evening sky. Chart made Stellarium