THE COALSACK

There is little or no moon this week so, especially if you can get out to a dark area outside of the big cities, you will be able to see a black area of sky right next to the Southern Cross, and about the same size.

It isn’t dark because space in that direction is empty. It is a nebula, a cloud of dust and gas, called the Coalsack. These galactic clouds are unimaginably huge compared to clouds in Earth’s atmosphere. 

Many nebulae either are, or will become, stellar nurseries, the places where stars are born. Some nebulae are bright, glowing from the radiance of the stars within, while others are dark, awaiting the eventual birth of young stars condensing out of the dust and gas of which they are made.

The galaxy is strewn with dark regions like the Coalsack Nebula, where the gas and dust are so dense that they block the light of the stars beyond them. This particular cloud is quite close by galactic standards, just a few hundred light years away, so it may one day allow us a close peak at the formation of new stars within.

A STELLAR NURSERY

We have another nebula appearing on the other side of the Cross from the Coalsack, and a bit farther away. This one, called The Carina Nebula, is not dark like the Coalsack. 

It’s an enormous rich field of stars embedded in the glowing dust and gas left over from their formation. The atoms of the various gasses in the cloud are emitting light the same way atoms of our atmosphere emit light causing the southern and northern lights.

One of the young stars formed within the nebula, Eta Carinae, is more than 100 times as dense as our Sun, and puts out millions of times more energy. In China it is known as Tseen She or “heaven’s altar".

Astronomers expect that we will see the violent supernova explosion of this massive star within the next 2000 years or so. It will be the brightest thing in our night sky except for the moon. 

Since it takes over 7500 years for light to get here from the Carina Nebula, it means we are waiting to see something that we think already happened several thousand years ago!

In a dark sky, with just your naked eyes, you can see the Carina Nebula as a smudge of fuzzy brightness within the general glow of the Milky Way. 

It will appear white, as our eyes are not sensitive enough to capture the brilliant colours of these distant and beautiful objects. We need time-lapse photographs, like Fraser’s, for that.

Be sure to look for these dark-sky wonders this week if you can. The moon returns brightly to our night sky next week, making these faint objects more difficult to see.

SOUTHERN LIGHTS

This event probably was only visible in the South Island, so here it is for everyone to enjoy. Fraser made this aurora animation just this morning (Monday) looking south from the Church of the Good Shepherd with Lake Tekapo at his back.

The Sun is really putting on a show for us lately, perhaps even intermittently disrupting cellphone service. 

You will see what appear like colourful curtains of light blowing in the wind. This display of the southern lights was well visible at least as far north as Christchurch, halfway to the equator from the South Pole, because of a large magnetic storm on the surface of the Sun just a little over a day ago.

It takes the light from the Sun just over eight minutes to get here, but the heavier charged particles that cause the aurorae travel a little slower.

They were blasted away from the Sun directly toward Earth when the magnetic field lines they were following broke apart. When the particles came near to Earth they were captured by our planet’s magnetic field and sleeted down above the poles where they disrupted the gasses in our high atmosphere causing them to glow in their characteristic colours.

You will see what appear like curtains of red and green light blowing in the wind, moving back and forth above the landscape. The red is nitrogen and the green is oxygen, the two main components of the air we breathe.

 

- © Fairfax NZ News