Australasian Science: Australia's authority on science since 1938

A Telescope as Big as the Earth

By David Reneke

News from the space and astronomy communities around the world.

Telescopes have expanded humanity's vision beyond what we could have ever imagined, but our eyes are only so sensitive and cover a rather small range of the visible spectrum.

Using the supersharp radio “vision” of one of astronomy's most precise telescopes, scientists have extended our electronic reach three times farther into the cosmos than ever before. This achievement has important implications for numerous areas of astrophysics, including determining the nature of dark energy, which makes up 70% of the Universe.

The continent-wide Very Long Baseline Array (VLBA) is also redrawing the map of our home galaxy, and is poised to yield tantalising new information about extra-solar planets, among many other cutting-edge research projects.

The VLBA is a system of ten radio telescope antennae, each with dishes 25 metres in diameter and weighing 240 tonnes. From Mauna Kea on the Big Island of Hawaii to St Croix in the US Virgin Islands, the VLBA spans more than 8000 km, providing astronomers with the sharpest vision of any telescope on Earth or in space.

Its unique power comes from the distances between the telescopes. This provides the greatest ability to see fine detail of any telescope in the world. It can produce images hundreds of times more detailed than those from the Hubble Space Telescope.

Its resolving power is equivalent to sitting in Sydney and reading a newspaper in Perth! This amount of clout allows astronomers to make precise cosmic measurements with far-ranging implications for research within our own galaxy and far beyond.

In fact, scientists using the VLBA are redrawing the map of the Milky Way. Our galaxy is not only larger than we realised but has four spiral arms, not two, as previously thought.

“Because we sit inside our galaxy, it is difficult to actually map it,” explains astronomer Mark Reid of the Harvard–Smithsonian Centre for Astrophysics in Cambridge, Massachusetts. Earlier work by Reid and his colleagues showed that the Milky Way is rotating faster than previous estimates.

Reid’s team is also observing the Andromeda galaxy in a long-term project to determine the direction and speed of its movement through space. “The standard prediction is that the Milky Way and Andromeda will collide in a few billion years,” Reid says. “By measuring Andromeda’s actual motion, we can determine with much greater accuracy when that will happen.”

You have been warned.

What Goes Up…..
Towards the end of last year news that a defunct US satellite was falling created a sensation around the world. We didn’t know when and where it would fall. The 6000 kg dead mass ultimately entered the Earth's atmosphere and broke into pieces over a large area of the Pacific Ocean and possibly in Canada.

There are thousands of such dead satellites circling the Earth waiting their turn to enter the atmosphere and fall like a meteorite. With more countries entering the space race, the number will increase – and so will the warnings for us to watch the skies.

Space debris includes a wide variety of objects, from man-made satellites to spacecraft. Satellites could fall because of depletion of fuel and their power supply or could explode in space due to malfunction. Or they might be destroyed as part of anti-satellite missile tests like China conducted recently.

Debris includes stages of the rocket carrying the satellite into orbit. It could also consist of things left out in space during space station operations including hand gloves, cameras, toothbrushes, wrenches, tool bags lost by astronauts, garbage boxes and so many other things. The size of the debris varies from a ping pong ball to a passenger bus.

Larger pieces may weigh as much as 6000 kg whereas small bits may be just a few grams. These objects can travel at speeds 30 times faster than a rifle bullet. Ouch!

Space debris is a menace not only for Earth but for orbiting manned space stations, rockets carrying astronauts, air traffic on Earth and live satellites. In the recent past astronauts aboard the space station had to take refuge in the emergency escape module of Soyuz spacecraft until the collision danger was over.

There have been encounters with space shuttles as well, with some flights being delayed in order to avoid clashes with space debris likely to cross it en route. Dead satellites hit operational satellites and damage them all the time. The total weight of debris in space is estimated to be about 60,000,000 kg.

World space agencies are trying to figure out how to tackle the issue of prevention and mitigation of space debris, and a global forum represented by 12 countries has been formed to coordinate the activities in this area.

David Reneke is an astronomy lecturer and teacher, a feature writer for major Australian newspapers and magazines, and a science correspondent for ABC and commercial radio. Subscribe to David’s free Astro-Space newsletter at www.davidreneke.com