Sky Guide June 2023

Over thousands of years the sky has been mapped into suburbs or constellations. They are groups of stars that have been given a name and more recently a border. They have been used as tools to share significant cultural stories, events and as markers. Today, the 88 western constellations used here help astronomers map the sky and search for astronomical objects. In June these constellations dominate the sky.

Leo the lion, in the northwest. The brightest part looks more like an upside-down question mark, as seen in the southern hemisphere, than a lion from the north. Its brightest star Regulus (Little King) is a system of four tightly bound stars at 79 light years. It was once referred to as one of the four Royal Stars, or guardians of the heavens because of its proximity to the point in the sky that marked the northern Summer Solstice as seen by Persian astronomers ~5,000 years ago. Precession of the equinoxes has now moved this point to Cancer the crab.

Virgo the maiden, high overhead is the second largest constellation in the sky and one of the two in which the ecliptic and celestial equator cross. This one marks the current position of the September equinox, the beginning of our southern Spring. It is home to a cluster of galaxies, of which M87 is the largest, at around 60 million light years with a central black hole at least 7 billion times the mass of the Sun. Virgo has one bright star, the 16th brightest in the night sky called Spica which is about 250 light years away. Like most stars, it is a binary. The brighter of the two being about 7 times the diameter of the Sun and 10 times more massive. Its hot surface temperature of around 20,000 kelvin makes it blue white in colour.