Powerhouse Museum - Sky Guide November 2024

Eridanusis one of Ptolemy’s original 48 constellations and represents a river, which begins near the constellation of Orion and ends at the brilliant blue-white star Achernar, the ninth brightest in the night sky, about 144 light years away. Achernar spins so quickly it is the least spherical star known in the Milky Way Galaxy.

Ophiuchus the serpent bearer is an ancient constellation and one of the original 48 as mapped by Ptolemy. It is said to represent the mythical healer Aesculapius. It sits close to the galactic centre in Sagittarius. It is now the thirteenth zodiac sign with the Sun passing through it from 30 November to 17 December.

Pegasus the winged horse is easy to find low in the north by looking for four bright stars that outline the ‘Great Square of Pegasus’. The Square is large: more than 15 degrees wide and 13 degrees high. In the past all four stars were part of the constellation, though delta Pegasi is now known as Alpha Andromedae.

Sagittarius the archer is located just behind the sting of Scorpius. In Greek mythology the archer is a centaur pointing his arrow towards the heart of Scorpius, although from the southern hemisphere this constellation looks more like a teapot. Sagittarius is home, as we see it, to the centre of our galaxy, the Milky Way. At this centre is a monstrous black hole about four million times the mass of the Sun and 26,000 light years away. Called ‘Sagittarius A *’ (pronounced as Sagittarius-A-Star), images taken in 2017 and released in May 2022 from NASA’s Event Horizon Telescope (EHT) show matter swirling around it at close to the speed of light. The event horizon is about the same distance from the singularity as Mercury is from our Sun.

Taurus the bull is possibly the oldest Western constellation and one of Ptolemy’s original 48. It has the bright red dying star of Aldebaran and the stunning open cluster known as M45 or the Pleiades, a group of very young stars about 445 light years away. Below the horns is the remnant of a star that exploded as a supernova in 1054. It is now called M1 or the Crab Nebula. For the best view you'll need a large telescope and clear northerly view. Its brightest star Aldebaran is 65 light years from the Sun and is 44 times wider but only a little more massive (+16%). It has exhausted its core supply of hydrogen fuel and is now ‘burning’ hydrogen in a shell around a helium core.

Powerhouse Museum - Sky Guide November 2024