Stars are born within vast, cool clouds of dust and gas in the spiral arms of galaxies like our own. These clouds include molecular hydrogen and helium, plus traces of other elements, such as oxygen, silicon and carbon. Over time, a lot of this gas and dust comes together, probably due to shock waves from exploding stars or passing galaxies.

The gas and dust form into globules, and small disturbances make these globules start to rotate. As the mass of the globules slowly increases, so does the force of gravity, causing the globules to condense into what are called protostars.

As more material spirals inward, the newly formed protostars are surrounded by disk-shaped clouds. Under increasing pressure and temperature, these infant stars begin to glow, radiating light, heat and radio waves. At this point, they’re still not true stars. Their subtle glow is obscured by the surrounding clouds, but we can detect their energy using infrared and radio telescopes.

As the protostar’s core continues to collapse, its temperature increases. Once the core temperature reaches about 4 million degrees Celsius, which takes between 100 000 and 10 million Read More
Stars are born within vast, cool clouds of dust and gas in the spiral arms of galaxies like our own. These clouds include molecular hydrogen and helium, plus traces of other elements, such as oxygen, silicon and carbon. Over time, a lot of this gas and dust comes together, probably due to shock waves from exploding stars or passing galaxies.

The gas and dust form into globules, and small disturbances make these globules start to rotate. As the mass of the globules slowly increases, so does the force of gravity, causing the globules to condense into what are called protostars.

As more material spirals inward, the newly formed protostars are surrounded by disk-shaped clouds. Under increasing pressure and temperature, these infant stars begin to glow, radiating light, heat and radio waves. At this point, they’re still not true stars. Their subtle glow is obscured by the surrounding clouds, but we can detect their energy using infrared and radio telescopes.

As the protostar’s core continues to collapse, its temperature increases. Once the core temperature reaches about 4 million degrees Celsius, which takes between 100 000 and 10 million years, nuclear fusion starts,-and a new star is born.

© Canadian Heritage Information Network, 2003

Trifid Nebula

New stars light up clouds of gas and dust in the Trifid Nebula.

HST/STSI

© US Gov public Domain


The Hercules Cluster

The Hercules Cluster of galaxies is 650 million light-years from Earth. In this image, the spiral galaxies appear bluish because they are home to hot, newborn stars. The elliptical galaxies are yellowish because they are full of cool, old stars.

NASA

© US Gov public domain


30 Doradus

A cluster of hot young stars in 30 Doradus illuminates interstellar gas in the Large Megellanic Cloud.

NASA

© US Gov public domain


From the moment a star is born, its fate is sealed. Depending on its mass, it could end its life quietly or as a blazing supernova. Throughout their lives, stars evolve: they grow and degenerate; they can be violent and explosive; and they are more central to our existence than we ever imagined.

To some ancient people, the stars looked like tiny pinholes in the sky, with the fires of creation shining through them.

When a star begins to shine, it produces a tremendous amount of energy, thanks to the nuclear fusion of hydrogen into helium that happens in its core. Eventually, the star runs out of hydrogen fuel. What happens next depends on how much mass the star had to begin with.
From the moment a star is born, its fate is sealed. Depending on its mass, it could end its life quietly or as a blazing supernova. Throughout their lives, stars evolve: they grow and degenerate; they can be violent and explosive; and they are more central to our existence than we ever imagined.

To some ancient people, the stars looked like tiny pinholes in the sky, with the fires of creation shining through them.

When a star begins to shine, it produces a tremendous amount of energy, thanks to the nuclear fusion of hydrogen into helium that happens in its core. Eventually, the star runs out of hydrogen fuel. What happens next depends on how much mass the star had to begin with.

© Canadian Heritage Information Network, 2003

Globular Cluster

Stars in globular cluster NGC6354 formed more that 12 billion years ago: the universe must be even older.

CFHT (Canada-France-Hawaii Telescope)

© CFHT


When a star with about half the Sun’s mass runs out of hydrogen fuel, it contracts into a white dwarf. A white dwarf is a tiny compact star, so dense that just one teaspoon of its matter would weigh about a tonne on Earth. Although no longer burning, a white dwarf is still incredibly hot. It slowly cools until all that’s left is a burnt out black core. After about 100 billion years, the star’s life is over.

When a star with about half the Sun’s mass runs out of hydrogen fuel, it contracts into a white dwarf. A white dwarf is a tiny compact star, so dense that just one teaspoon of its matter would weigh about a tonne on Earth. Although no longer burning, a white dwarf is still incredibly hot. It slowly cools until all that’s left is a burnt out black core. After about 100 billion years, the star’s life is over.

© Canadian Heritage Information Network, 2003

A star with up to 2½ times the mass of our Sun goes through a red giant stage before it becomes a white dwarf. The star’s core gets so hot that its atmosphere balloons outwards. If you could put a red giant where our Sun is, it would extend as far as the orbit of Venus, or even Earth. Eventually, a red giant collapses and becomes a white dwarf, then slowly cools to a black core.

A star with up to 2½ times the mass of our Sun goes through a red giant stage before it becomes a white dwarf. The star’s core gets so hot that its atmosphere balloons outwards. If you could put a red giant where our Sun is, it would extend as far as the orbit of Venus, or even Earth. Eventually, a red giant collapses and becomes a white dwarf, then slowly cools to a black core.

© Canadian Heritage Information Network, 2003

White dwarf

As a red giant collapses, it expells the outer layers of its atmosphere. The star's core remains as a white dwarf near the centre of the huge bubble.

WIYN /NOAO / NSF

© WIYN /NOAO / NSF


Supergiant stars are up to 100 times more massive than our Sun. When a supergiant runs out of fuel, it collapses and blows apart in a supernova explosion. The remaining core continues to collapse and becomes either a neutron star or a black hole, depending on how much mass was left after the explosion.

Supergiant stars are up to 100 times more massive than our Sun. When a supergiant runs out of fuel, it collapses and blows apart in a supernova explosion. The remaining core continues to collapse and becomes either a neutron star or a black hole, depending on how much mass was left after the explosion.

© Canadian Heritage Information Network, 2003

Light echo

The light echo of supernova 1987A.

David Malin

© Anglo-Australian Observatory


The atoms that make up our bodies were originally created in the thermonuclear fires at the heart of supermassive stars that exploded billions of years ago. In a very real sense, we are all made of stardust!

The atoms that make up our bodies were originally created in the thermonuclear fires at the heart of supermassive stars that exploded billions of years ago. In a very real sense, we are all made of stardust!

© Canadian Heritage Information Network, 2003

Made of stardust

We are made of stardust.

National Research Council of Canada

© National Research Council of Canada


Learning Objectives

The learner will:

  • Define star
  • Describe how stars form
  • Describe in pictures and words the stages of stars

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