Skylights Bite Size 15 - Orion the Hunter and Sirius the Dog Star

By ANDY FLEMING

The Orion Nebula, one of the most brilliant star-forming regions in our galaxy. Other, newly-discovered regions like the Orion Nebula could help astronomers determing the chemical composition of our galaxy. Image Credit: APOD/Hubble Space Telescope

If you look to the southern horizon on a clear winter's evening from a location in the northern hemisphere, you’ll see the gorgeous constellation of Orion the Hunter, unmistakable due to the three bright stars in a diagonal line that constitute his belt. These are called Alnilam, Alnitak and Mintaka.

Look down from the left hand side of the belt and running down almost vertically is Orion’s sword. A hazy patch around the middle of the sword reveals itself through binoculars as the Great Nebula in Orion… a stellar nursery with some new born stars in its centre.

This podcast examines an astronomical constellation with a real 'wow' factor and also takes a look at Sirius the Dog Star near to Orion, and one of the closest stars to the Earth.

MP3 DOWNLOAD FOR YOUR FAVOURITE MEDIA PLAYER

Skylights Bite Size 15 - Orion the Hunter and Sirius the Dog Star
Download this episode (right click and save)

Podcast also available on

Skylights is featured on Solid Gold Sunday each Sunday afternoon at 1425h UTC on 102.4FM in Hartlepool/East Durham, UK and live around the world online at www.radiohartlepool.co.uk
________________________________________________________________
Show Notes and Transcript

If you look to the southern horizon on a clear late evening from Hartlepool this month you’ll see the gorgeous constellation of Orion the Hunter, unmistakable due to the three bright stars in a diagonal line that constitute his belt. These are called Alnilam, Alnitak and Mintaka.  Look down from the left hand side of the belt and running down almost vertically is Orion’s sword. A hazy patch around the middle of the sword reveals itself through binoculars as the Great Nebula in Orion… a stellar nursery with some new born stars in its centre.

Star-hop following a line straight down from Orion’s Belt and you will find Sirius, easy to locate as it’s the brightest star in the night sky.  A very hot star and hence a bluish hue, it’s actually part of another constellation, called Canis Major, or the Greater Dog.  Sirius is bright for two main reasons – it’s much larger than our Sun and is just 8.6 light years distant.

Sirius is also known colloquially as the "Dog Star", and was an important object in antiquity. The heliacal rising of Sirius marked the flooding of the Nile in Ancient Egypt and the "dog days" of summer for the ancient Greeks, while to the Polynesians it marked winter and was an important star for navigation around the Pacific Ocean.

But Sirius has a secret that wasn’t revealed until as late as 1862. It turned out it wasn’t alone. Orbiting it was an intensely dense and tiny star at the end of its life, a cosmic cinder otherwise known as a white dwarf. It was unresolved until bigger and more powerful telescopes came along, due to the glare from the Dog Star itself that thereafter was named Sirius A. It orbits Sirius at a distance much less than the radius of our solar system.  It’s called Sirius B or appropriately enough, the Pup! So Sirius is what astronomers term a binary star system!