Explore Orion

Orion's Belt

Orion's belt is one of the most noticeable asterisms in the night sky. It is defined by the three bright stars cutting through the middle--the "waist"--of the Orion constellation. They serve as a good starting point for one to get oriented with the night sky. Bruce McClure from EarthSky writes,

See the three stars at the mid-section of the constellation Orion the Hunter? These stars are very noticeable and famous in many cultures as Orion’s Belt. But – to the Aymara people of Bolivia, Peru and Chile – they represent a Celestial Bridge. And there’s good reason for that. Orion’s Belt – the Celestial Bridge – links the northern and southern hemispheres of the sky.

Consider the westernmost star of Orion’s Belt, called Mintaka. This star sits almost directly astride the celestial equator: the projection of Earth’s equator onto the stellar sphere.

Where can you find Mintaka and the constellation Orion? In late November, from around the world, Orion rises into your eastern sky around 9 p.m. and climbs highest up for the night around 1 to 2 a.m. local time (the time on your clock no matter where you are on the globe).

When dawn is breaking, or about to break, say around 5 to 6 a.m., the Hunter sits low in your western sky.

Bruce McClure, Orion’s Belt – a Celestial Bridge – links northern and southern skies

Rigel

Rigel lies about 860 light years away, and is actually part of a four star system.

The blue supergiant is quite bright--in fact, it is between 61,500 and 363,000 times as bright as the Sun and is 18-24 times as massive. Rigel's mass will decide its ultimate fate. Rigel will eventually run out of fuel to burn in its core, resulting in a catastrophic chain of events culminating in a supernova--a massive explosion. Rigel will leave behind either a neutron star or a black hole, depending on its precise mass. Until then, we can always look up and admire the blue jewel of Orion.

Betelgeuse

Betelgeuse is around the tenth brightest star in the sky, and the second brightest star in the Orion constellation. Betelgeuse is less than 10 million years old--young for a star. Its rapid lifecycle is due to its large mass; it is between 16.5 and 19 times the mass of the Sun. Betelgeuse is also fairly close to the Sun at around 500 light years.

It is a red supergiant star similar to Rigel. Its mass also means that it will end its life as a Supernova. Betelgeuse is expected to reach the end of its life within 100,000 years--imminently soon in Astronomical terms. It is possible that this has already happened and that we could see the result in our lifetimes. For us to see the supernova, the light will need to reach us before we notice that it has happened! This means that if we see Betelgeuse light up the sky as a supernova, it actually happened roughly 500 years ago. The supernova would be quite a sight, being visible in daytime with a brightness comparable to the full moon.