“Just So Science” – The Astral Archer’s Bow

By Elf Eldridge 01/08/2011 1


As a follow-on from my previous Sagittarius post, this week I want to mention a few of the eye-watering spectacles viewable within this astral archer at this time of the year. All of the objects i’m about to mention are just to the North of the cosmic teapot, where the steam would billow from the spout in fact. The first two, M8 and M20 are visible in most photos of the centre of the Milky Way as large glowing, red smudges of starlight reflected and emitted from huge clouds of interstellar dust and gas.

Galactic Centre within Sagittarius showing red patches of emission nebulosity
Galactic Centre within Sagittarius showing red patches of emission nebulosity

These are two famous, and extensively studied Messier objects: the Trifid and Lagoon nebulae. The trifid nebula is, like most of the nebulae I blog about, a hot-spot of star formation. The somewhat strange name comes from its ‘tri-lobed’ appearance in the visible spectrum due to vast dark dust-clouds swirling between us and it (on the left of the image below). The power of infrared images (below right) is evident by allowing us to peer curiously through those dust clouds into the heart of this structure, full of bright ’embryonic’ stars. There are over 30 individual star forming regions within this nebula and we currently believe that this is due to the single massive star at the nebula’s centre causing the parent gas clouds to condense into embryonic proto-stars.

Trifid Nebula in various regions of the spectrum
Trifid Nebula in various regions of the spectrum

Nearby is the next, smaller object – the lagoon nebula, M8. To give some idea of scale, from the night sky this nebula covers an area of 8 times larger than the full moon, however the colour is not readily apparent to human eyes due to the low light levels. This is an H II region, hence the red colouration and houses a couple of star forming regions, but the image to the right below is what has drawn many astronomers to this nebula and from where it gets its name. The colours here are from the ionization of Nitrogen, produced by the radiation given off by the young stars in the picture, smashing into the massive nitrogen clouds and causing them to emit green light. When coupled with the effect of the stars’ stellar winds, it appears as if ‘ripples’ are flowing through these clouds giving rise to a lagoon-like visage.

Lagoon nebula as it appears through a telescope in the night sky
Lagoon nebula as it appears under long exposure photograph conditions in the night sky.
Closeup of one of the internal regions of the Lagoon Nebula
Closeup of one of the internal regions of the Lagoon Nebula

Further away from these is yet another mysterious Sagittarian nebula: the Omega (or Swan or Lobster or Horseshoe) Nebula. The clouds visible in these images are sculpted by the out-pouring of gas from the stars clustered within them, contorting the clouds into spirals and bulbs, punctuated occasionally by shockwaves from the radiation of these stars.

Omage Nebula - inset showing shockfronts from stars within.
Omage Nebula - inset showing shockfronts from stars within.
Boiling star formation clouds within Omega nebula
Boiling star formation clouds within the Omega nebula

I mention these images for one other reason as well as just their aesthetic appeal, namely to show that the universe in all it’s expansive wonder is a predominantly hostile to us squishy little humans. In fact, if space isn’t completely empty (as most of the universe is) then there’s a good chance it will burn us, crush us, poison us, irradiate us or one one millions of other ways for us to meet grisly ends. And yet somewhere in the midst of this chaos we have managed to find a tiny dot that is actually tolerant to our continued presence. A little dot where we can all live and love, experience joy and pain, raise a family and explore – where our biggest danger is ourselves. And currently we find ourselves debating whether to take action against climate change or not. We snipe and criticise, complaining about lack of reproducible results and the age old correlation vs causation, all simply to give us excuses to sit on our hands whilst our atmosphere slowly heats up and eventually boils, taking us and every glorious species on our planet with it.

Well I propose this: No price it too high to pay for the safety of our home. It’s the only one we may ever have. Possibly the only suitable one in existence. The question we should be debating is not whether to take action or not, but what can our species do to ensure that our home remains just that, a home, and not one of the other thousand billion inhospitable planets in our galaxy.


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