Star Spy: Forming shapes

21:22, Feb 05 2013
Orion south
Orion south


Taking a few steps back from last week’s view of the Horsehead and Flame Nebulae, we can see more of their context in the Orion constellation.

This beautiful image presents a wider and yet still detailed view of a portion of what is known as the Orion Molecular Cloud Complex.

It is a long name for a region of dust and gas and new young stars that stretches across more than 200 light years of space. 

Around 1400 light years from us, it is one of the closest regions of star formation to our solar system. 

More than 2000 of the hot young stars forming within the complex appear to be forming planetary systems around them.     


The main stars that make up the shape of Orion the Hunter are at varying distances between us and the cloud.  

The Orion and Flame Nebulae are bright stellar nurseries, while the Horsehead is a dark cloud silhouetted against the glowing region behind it.   

We are learning a great deal by studying the various structures, and the processes occurring, in this important and nearby region of our galaxy. 


This one is ours, of course, clearly resembling a blotchy melon at the supermarket, in this Full Moon photo (above). 

Just as mankind has spent time gazing at the night sky to find patterns of familiar objects and stories in the stars, what we call constellations or asterisms, we have also enjoyed finding patterns in the light and dark areas of the Moon.

There are The Man in the Moon, The Cow Jumping Over the Moon, The Rabbit making sticky rice cakes, and a round chunk of Swiss Cheese to name a few.

Most moonlit nights, viewed through binoculars or a small telescope, the origin of the Swiss Cheese idea becomes clear. 

Our moon is pock marked with thousands of craters, the remains of impacts with large and small rocks, bits and pieces left over from the formation of the solar system. 

One recently formed crater (in astronomical timescales), distinctive for its appearance and pale colour, is called Tycho, pronounced TeeCo, named for 16th century Danish astronomer Tycho Brahe. 

An early name given to Tycho (the crater) was Umbilicus Lunaris, meaning ‘the navel of the Moon’. 

The impact that made the 85km wide crater threw up enormous amounts of lunar soil and ejecta forming the pale rays we see emanating from the crater. Some of the rays from the impact stretch as far as 1500km from their source.

If you could take a position directly above Tycho you would clearly see that most of the ejecta has travelled north, south and east on the Moon’s surface, with very little to the west of the crater. 

This is a strong indication that the object that hit the Moon came in low from west, scattering lunar material forward from the impact. 

Dinosaurs, roaming the Earth a little over 100 million years ago, may have observed the event.