SJAA

Ephemeris

The Central Bulge - From Central Australia

Jane Houston


The spectacular shapes of Uluru (Ayers Rock) and Kata Tjuta (The Olgas) dominate the surrounding flat desert of Central Australia. They are the culmination of geologic events stretching over millions of years.

Human settlement in this region dates from at least 22,000 years. Earlier still, 900 million years ago, most of Central Australia lay at or below sea level, forming an arm of the sea known as the Amadeus Basin. 550 million years ago this basin was raised up, squeezed, crumpled, buckled into folds. These folds fractured along faults. The country uplifted and was subjected to erosion. Ayers Rock and the Olgas are the result we see today.

Ancient Australian Aborigines inhabited and worshiped here. They camped out beneath the Otars for thousands of years before the invention of light pollution. They slept and dreamt under the stars. They took the night stars for granted. They embraced the darkness. It is woven into their culture through song, dance, ritual, art and myth.

The Magellanic clouds and dark patches we call dark nebulosity figured into aboriginal mythology. Some say the Coal Sack is a watering hole, surrounded by the ancestral heroes. The great stars Alpha and Beta Centaurus, and the beautiful stars of the Southern Cross, for example, represent these heroes.

The Magellanic clouds appear as twilight ends. Appearing first as soft glows, they remind me of passing clouds. The LMC is highest and 22 degrees away from the SMC. It is difficult to discern the barred spiral shape. Most of the light and mass of the LMC is concentrated around the bar. It is rich with star clusters and nebulae. There are hundreds of planetary nebulae, supernova remnants, and gas bubbles within the LMC. A month of Ayers Rock nights would not be enough to do observing justice. My five nights offer but a glimpse!

The single most interesting object in the LMC is the giant HII region NGC 2070, the Tarantula Nebula. Also called the 30 Dorados Nebula, it is a vast area of ionized gas 900 light years in diameter. Its mass is 500,000 suns. It owes its power to over 100 supergiant stars. To me the round dark patches, circled by wispy arms of gas, are beautiful and flower-like. I found myself returning often to the Tarantula.

The Keyhole Nebula section of NGC 3372, Eta Carina, is a dark rift dividing the petal-like sections of the massive nebula spanning over 1 degree in diameter. Eta Carina, the star, is involved in the most interesting transformation. It is an exceptional class of supernova, surrounded by dense by dense nebula, which is expanding at 500 km per second. Through the 20-inch, 15-inch, and 12.5-inch telescopes we could observe ropy dark knots in the nebular on either side of the unstable star.

I could go on and on. Omega Centauri, the spectacular cluster, looks like lace in the 20-inchers. Perhaps the most spectacular sights so far (after three observing nights) are the arm of the Milky Way, the Southern Cross and Coal Sack dark nebulae overhead, Scorpius and Sagitarius being pulled out of the horizon, or maybe Mars rising on one horizon and Venus setting on the opposite side - the slow tango on the ecliptic plane.

[Dispatched by fax from Ayers Rock Australia, April 15, 1999. - ed.]


Jane Houston; last updated: October 04, 2007 Prev Next