It’s a big universe, especially when you’re looking for something small like a planet, or rare like signals from an alien civilization. Astronomers have already found planets outside our solar system, and they’re looking for more. For more than 40 years, we’ve been searching for life on other planets by listening to radio waves. And astronomers are also hunting for rare pulsars - the small spinning stars that are left over after massive stars collapse.
It’s a big universe, especially when you’re looking for something small like a planet, or rare like signals from an alien civilization. Astronomers have already found planets outside our solar system, and they’re looking for more. For more than 40 years, we’ve been searching for life on other planets by listening to radio waves. And astronomers are also hunting for rare pulsars - the small spinning stars that are left over after massive stars collapse.

© Canadian Heritage Information Network, 2003

Planets are too small for us to see through a telescope, so planet hunters use the "Doppler wobble" technique. As an unseen planet orbits a distant star it tugs on the star, making the star move back and forth in space. That wobble can be detected by the Doppler shift in the star’s light.

In the early 1990s, astronomers found the first planets outside our own solar system. Since then, planet hunters have been busy combing the stars for more. A team of astronomers from the U.S., Australia and the UK has found several new planets. In 2002, they found the first system that looks something like our own solar system, with a Jupiter-like planet orbiting a Sun-like star.

The newfound planet is about the same distance from its star as Jupiter is from our Sun. It’s between 3.5 and 5 times the mass of Jupiter, and its slightly elongated orbit takes it around the star in about 13 years, similar to Jupiter’s orbit of 11.86 years.
Planets are too small for us to see through a telescope, so planet hunters use the "Doppler wobble" technique. As an unseen planet orbits a distant star it tugs on the star, making the star move back and forth in space. That wobble can be detected by the Doppler shift in the star’s light.

In the early 1990s, astronomers found the first planets outside our own solar system. Since then, planet hunters have been busy combing the stars for more. A team of astronomers from the U.S., Australia and the UK has found several new planets. In 2002, they found the first system that looks something like our own solar system, with a Jupiter-like planet orbiting a Sun-like star.

The newfound planet is about the same distance from its star as Jupiter is from our Sun. It’s between 3.5 and 5 times the mass of Jupiter, and its slightly elongated orbit takes it around the star in about 13 years, similar to Jupiter’s orbit of 11.86 years.

© Canadian Heritage Information Network, 2003

Extrasolar Planet

Imaginary view of an extrasolar planet passing in front of a sun-like star.

Richard Joli

© Richard Joli


The search for life outside our planet is called SETI-Search for Extra-Terrestrial Intelligence. For more than 40 years, astronomers have been trying to find radio signals that could come from extraterrestrial civilisations.

What kinds of signal would an extraterrestrial civilisation make? It might send signals deliberately to attract our attention. Or signals might just 'leak' out into space. Our radio signals-from radio, television and military radars-have been leaking off Earth for about 50 years, so it's possible someone could be listening to us!

Most SETI searches concentrate on a small section of the microwave part of the radio spectrum (see Spectroscopy to learn about the types of radiation). There aren't a lot of natural radio emissions in this range, so there is less background noise.

The most sensitive SETI search so far is called Project Phoenix. The first Phoenix observations were done at Parkes radio telescope in Australia, and the search continues today at the Arecibo radio telescope in Puerto Rico.

Instead of scanning the whole sky, Project Phoenix focuses nearby stars that are similar to our Sun. These are the stars w Read More
The search for life outside our planet is called SETI-Search for Extra-Terrestrial Intelligence. For more than 40 years, astronomers have been trying to find radio signals that could come from extraterrestrial civilisations.

What kinds of signal would an extraterrestrial civilisation make? It might send signals deliberately to attract our attention. Or signals might just 'leak' out into space. Our radio signals-from radio, television and military radars-have been leaking off Earth for about 50 years, so it's possible someone could be listening to us!

Most SETI searches concentrate on a small section of the microwave part of the radio spectrum (see Spectroscopy to learn about the types of radiation). There aren't a lot of natural radio emissions in this range, so there is less background noise.

The most sensitive SETI search so far is called Project Phoenix. The first Phoenix observations were done at Parkes radio telescope in Australia, and the search continues today at the Arecibo radio telescope in Puerto Rico.

Instead of scanning the whole sky, Project Phoenix focuses nearby stars that are similar to our Sun. These are the stars we think have the best chance of hosting planets that can support life. When the project finishes in 2004 it will have searched for signals from about 750 stars, out to a distance of roughly 200 light-years.

Project Phoenix has been carried out by the California-based SETI Institute. The Institute plans to do a follow-on search with its new Allen Telescope Array, which is being built now. The new search will look at a few hundred thousand stars.

© Canadian Heritage Information Network, 2003

Pulsars are small spinning stars, the super-dense cores of massive stars that have exploded at the end of their lives. They are about 20 km across, but they have more mass than our Sun, and can spin at up to hundreds of times every second.

Pulsars put out a continuous beam of radio waves. The beam lies at an angle to the pulsar’s spin axis, so the end of the beam travels around in a circle like a lighthouse beacon. If the Earth happens to be in the path of the beam, we see repeated "pulses" of radio waves as the beam sweeps over us. The faster the pulsar spins, the more often we see the beam and the shorter the gap between the pulses.

Australia’s Parkes radio telescope holds the world record for having discovered the largest number of pulsars since the first was found in 1967. Hundreds of thousands of pulsars are thought to live in our Galaxy, but we will never find them all. Some are too far away, and others have beams that don’t point towards us.

There are many different kinds of pulsars. Some spin only once every few seconds. Others, called "millisecond pulsars", spin hundreds of times every second. These Read More
Pulsars are small spinning stars, the super-dense cores of massive stars that have exploded at the end of their lives. They are about 20 km across, but they have more mass than our Sun, and can spin at up to hundreds of times every second.

Pulsars put out a continuous beam of radio waves. The beam lies at an angle to the pulsar’s spin axis, so the end of the beam travels around in a circle like a lighthouse beacon. If the Earth happens to be in the path of the beam, we see repeated "pulses" of radio waves as the beam sweeps over us. The faster the pulsar spins, the more often we see the beam and the shorter the gap between the pulses.

Australia’s Parkes radio telescope holds the world record for having discovered the largest number of pulsars since the first was found in 1967. Hundreds of thousands of pulsars are thought to live in our Galaxy, but we will never find them all. Some are too far away, and others have beams that don’t point towards us.

There are many different kinds of pulsars. Some spin only once every few seconds. Others, called "millisecond pulsars", spin hundreds of times every second. These are very old pulsars that have been spun up to high speeds by material flowing onto them from a companion star. Usually the partner is a white dwarf an old, shrunken star at the end of its life.

© Canadian Heritage Information Network, 2003

Pulasar

As a pulsar spins, its radio beam sweeps over the Earth.

Graphic: D. Parr

© CSIRO.


See a pulsar.

Canadian Heritage Information Network

© Canadian Heritage Information Network, 2003


Learning Objectives

The learner will:

  • Describe scientific and technological developments, past and present and appreciate their impact on individuals and societies
  • Relate some of the current questions being investigated by cosmologists, and the technology being used, or proposed, to answer them
  • Develop enthusiasm and continuing interest in the study of science

Teachers' Centre Home Page | Find Learning Resources & Lesson Plans