Thursday 7 February 2019

ARTICLE: Understanding Nebulae - what it is you are looking at

Hi all, the following is the first of a series of articles designed to help explain some of the things we see through the eyepiece, why we see some things and not others, some of the commons misconceptions regarding telescopes, and how to make the most of the telescope you have AND how to best exploit our very human eyes.  Of PRIME consideration for me though is to keep the tech-talk to a minimum so not to confuse, nor full of astro-jargon.  The articles will develop over a few parts.

The first article is about nebulae, why we see them the way we do on the most part without colour, what is actually going on inside them that gives them their shape, and tips on how to maximize your efficiency at the eyepiece.  


Understanding Nebulae - what it is you are looking at.

Part I
Nebulae can be beautiful stellar nurseries or the remnant ashes of a dying or dead star. In photographs they can also exhibit various colours, but mostly blue and red. And they can also exhibit a multitude of shapes and shades, from brilliant and colourful to dark and foreboding. Despite their many differences, what they all share is the forces of physics at play that form and mould them.

But what does it all mean?

One easy thing about understanding what you are looking at is you don’t need to have a degree in astrophysics, nor be a mathematics whizz. The concepts at play here are actually surprisingly easy to follow, and once you have the basic concepts figured out, then no matter what nebula you look at, you will be able to figure out what is going on with that nebula.

However, here I will let NASA do the heavy lifting for me in explaining nebulae! There is one NASA site that discusses the Eta Carina nebula using the images gathered of it by the Hubble Space Telescope. This Tour of Eta Carina will show you the structures and anatomy of a nebula, and by the end of the tour you will be able to recognise the various components and the forces at play. The greatest part of this is you will be able to use this knowledge with any other nebula you then look at.

What is especially good about this Tour is that the items being shown are ALL visible through amateur telescopes, depending on how large the telescope is, the bigger the aperture, the more details you will see. Yet even a modest 50mm telescope will reveal a lot that is mentioned in this NASA tour of the Eta Carina Nebula:

BUT FIRST! Look at these sketches to prime you for your tour.

To help you along with your learning experience, below are two sketches I have done of the Eta Carina Nebula. Both were done from my home in Sydney. The first using an 8” scope, and the second a 17.5” scope. Please look at these pictures before you visit the NASA site. Then, AFTER completing the Tour, look at the sketches of mine again with your newly gained knowledge, and all of a sudden you will see so much more detail in the sketches that previously you had no idea what you were looking at! Two cosmic bubbles that have two different sources, dark pillars that resist erosion and hide protostars, brand new stars that have just kicked off their nuclear fires, glowing gas that is charged by the intense radiation of enormous stars, a myriad of details that are always on show, but hide from view only because of not understanding what you are looking at.


Now, having armed yourself with a new understanding of what nebulae show in their appearance, you will now be able to identify these same characteristics in other nebulae. At little further education to some other nebula types, such as Super Nova Remnants (the glowing crap left over after a supergiant star explodes) and Planetary Nebulae (the glowing shell of material blown off by smaller stars that are dying (the way our own Sun will end)), yet they all show elements and features seen in the Eta Carina Nebula.

I have deliberately chosen to illustrate this whole document with my sketches in order to demonstrate that the features shown in that tour of Eta Carina are not invisible through a telescope, and very much within visual reach. And by all means, look up photographs of the items below and see for yourself that the view through a telescope can reveal a hell of a lot!

M16, the Eagle Nebula:

M42, the Orion Nebula:

The Veil nebula:

Thor's Helmet:

The Helix Nebula:


1 comment: