Sky Tour for Binoculars: Orion

Orion Star Map

Orion star map
Copyright: Melbourne Planetarium

Highlights of the tour:

  • a host of bright stars
  • the Great Nebula in Orion
  • a Mira variable star

The constellation of Orion is one of the most impressive sights in the night sky. From Melbourne it is best seen in the summer, when it dominates our northern skies. In ancient Greek mythology, Orion was a legendary hunter. To us in the southern hemisphere, he appears upside-down and is quite easy to recognise. The three bright stars in a line in the centre of the constellation represent his belt. Below these are two bright stars, Betelgeuse and Bellatrix, which mark his shoulders. Above the stars of the belt are two more bright stars, Rigel and Saiph, which are in his legs.

Rigel is the brightest star in this constellation, and shines with a brilliant white light. The next brightest is Betelgeuse, which has a reddish colour. Binoculars bring out the difference in colour very well. Betelgeuse is 310 light-years away. It is a red supergiant, large enough to swallow the Earth’s orbit around the Sun. The brightness of this star varies a little, as the star itself swells and shrinks over a period of more than 5 years. At its brightest it is almost as bright as Rigel. Rigel is much further away, at over 900 light-years, but it is the brighter of the two because it gives off more light.

Stop 1

This group of stars within Orion is commonly known in Australia as the Saucepan. This should fit within your field of view, with the three stars in the belt of Orion at the bottom. Their names are (from left to right) Mintika, Alnilam and Alnitak, and they form the base of the saucepan. Above these are the stars of the sword of Orion, which marks the handle of the saucepan. In the middle of this group is an object which appears to be a fuzzy star to the unaided eye. It is actually the spectacular Great Nebula in Orion, or M42, and through binoculars it can be seen as a large glowing cloud, shaped like a fan. Stars can be seen in the nebula and at the centre is Theta Orionis, a group of four star systems commonly called the Trapezium, though this can be difficult to see. M42 is over 1 000 light-years away and is relatively young, at around 30 000 years old. Stars are being formed in this nebula, and their heat cause the cloud to glow. M42 is actually just the brightest part of a much larger nebula which covers most of the constellation, but much of which we cannot see.

Stop 2

In the middle of this field is the variable star U Orionis. It is a Mira variable, a special type of variable star named after the star Mira in the constellation of Cetus. Mira variables are unstable, pulsating stars, either red giants or red supergiants, whose brightness varies considerably over time. The periods of these stars range from 80 to over 600 days. U Orionis has a period of 373 days, or just over a year. At its brightest it is an easy object to find in binoculars and has a strong reddish colour but at its faintest, it cannot be seen at all in binoculars.

Comments (12)

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Carl Joseph 22 January, 2010 17:45
Theta Orionis (the Trapezium) is usually viewed as four stars, but it's worth mentioning that two of these are actually binary stars. So, the Trapezium is made up of 6 stars.
Discovery Centre 28 January, 2010 15:10
Hi Carl, you are correct that more than four stars can be seen in the Trapezium but you need a telescope to do this. Most backyard telescopes can see 6 stars, but in fact larger telescopes can count many more! However most binoculars will only show the four brightest stars
Gemma 28 April, 2011 08:12
Is there anywhere I can obtain pictures of the stars within orions belt? As in, there are different stars that comprise the southern cross, I would like to get a siimilar view of orions belt and specifically the saucepan.
Discovery Centre 1 May, 2011 12:03

Hi Gemma,

A good place for space images is the NASA website. You should be able to find what you're looking for there.

YoonA 23 June, 2011 19:52
Amazing info! I'm a professional singer (in South Korea-SNSD) but I love Space! Thanks to this website, I now know much more information than I did before! Just wondering... where is the constellation of Leo?
debra 27 February, 2012 09:04
is there a pot and saucepan/fryingpan in the star constellations in the southern hemisphere
Discovery Centre 2 March, 2012 12:58

Hi Debra,

The saucepan is part of the constellation 'Orion' (the hunter) and the teapot can be seen in the constellation 'Sagittarius' (the archer). Both are visible in the southern hemisphere, usually even in light polluted towns and cities, but at different times of the year depending on the season. For example, Orion/Saucepan is visible in summer & autumn in the evening in the north to north-west. The Planetarium website has a comprehensive Skynote newsletter that can keep you up to date with what can be seen in the night sky each month.

TashCam 12 May, 2013 20:29
Do stars move or are they always located in the same spot?? Cameron and I tried looking for the saucepan for about 3 hours last night because it wasn't where it usually is.
Discovery Centre 14 May, 2013 12:46

Hello TashCam; we were asked a similar question on another page on this website found here; in short the answer is that even though everything in the Universe is in motion, constellations appear to move because we see them from a moving Earth. You can read more about the relative positions of constellations in the SkyNotes, which are published monthly.

Hope this helps

Ziggy 26 November, 2014 01:56
Thank you for explaining Orion so clearly. I bought a banana bed today to lie on and look up at the stars with my new National Geographic binoculars. I saw something fuzzy and thanks to you I now know it was the great nebula. Very interesting and clear information. Thanks again. Ziggy
sarah 24 January, 2015 00:41
what is the name of the star that makes up the end of the saucepan opposite orion's sword (between rigel and mintaka)? why isn't it named on star charts? it is quite bright (easy to see) and is part of the asterism the saucepan (or shopping trolley - which i like better) thanx
Discovery Centre 27 February, 2015 15:34
Hi Sarah - according to our experts at the Planetarium, most bright stars seen with the unaided eye (that’s about 10,000 visible to humans) have proper names but not all. It seems the star in question is Eta Orionis. It is the seventh brightest star in the constellation of Orion. Star maps show the half dozen brightest stars in each constellation and but not all the named stars otherwise the map would get too congested and hard to use.

Apart from any proper name given to a star, astronomers traditionally use the Greek alphabet to name stars so that the brightest in each constellation is “alpha”, the second brightest is “beta” etc...  However, this star does have several names depending on which cultural tradition applies or which star map system is used. Here’s an extract from one web source to explain more…

η Orionis (Eta Orionis)

Eta Orionis is an eclipsing binary star system that consists of two blue stars, belonging to the spectral type B0.5V, approximately 900 light years distant. It belongs to the Orion Arm, which is a minor spiral arm of the Milky Way, sometimes also known as the Orion Spur or the Orion-Cygnus Arm.

Eta Orionis, located just to the west of Orion’s Belt, has several traditional names: Saiph (which it shares with Kappa Orionis), Algjebbah, and Ensis, which means “sword” in Latin.

The star is classified as a Beta Lyrae variable, a type of close binary star with variations in brightness caused by one component occasionally passing in front of the other one. It has a visual magnitude of 3.38.

Hope this helps!

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