Sat. Mar 2nd, 2024
the origin of the stars

In our previous post, we talked about the Big Bang and the formation of galaxies, globular clusters and supernova remnants using images taken from the Killarney Provincial Park observatories.

In today’s post, we will explore how stars are born and how they begin their lives.

Nebulae and star formation.

Our galaxy, the Milky Way, is one of billions containing stars, gas, dust and dark matter.

Milky Way

Within and between the stars within a galaxy, we find the nebula.

Nebula, which comes from the word nebula (meaning hazy or unclear), is a term that astronomers use to describe three types of objects:

  • emission nebulae
  • reflection nebulae
  • dark nebulae

Emission nebula

If an interstellar cloud of gas and dust is charged with light from nearby stars and fluoresces like a neon sign, astronomers will refer to it as an emission nebula.

There are countless emission nebulae visible in the night sky with the right equipment, which often appear reddish in photographs due to the wavelength of light produced by charged atoms and electrons.

reflection nebula

If there is a lot of dust, but little starlight to carry the cloud of gas and dust, we will often see the light reflected by this dust in the form of bluish light.

We call these types of nebulae reflection nebulae.

dark nebula

When astronomers look into the distant reaches and observe the many splendours, they often observe what at first appear to be dark regions within the distant areas.

But astronomers have studied these dark areas and determined that they are not an absence of material in the background view, but rather clouds of interstellar dust that are so thick that they obscure the light from more distant objects.

We know this because we can switch our vision from visible light to infrared light, which is not as affected by dust, and see objects in the background with less obscuration.

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The life of stars like the phoenix

While the first stars would have formed only from hydrogen (see our first post in this series), the often destructive deaths of those first stars would have enriched their surroundings with hydrogen-filled supernova shock waves, as well as many other atoms, including:

  • helium
  • coal
  • oxygen
  • magnesium
  • sodium
  • iron

Just to name a few.

Most of the nebulae we see today contain a large amount of atomic elements, the remains of former stars mixed like condiments in a soup broth, among the ever-present hydrogen gas.

Some of these atomic elements combine into molecular clouds, producing a complex and rich set of chemistry available for the next generation of stars to use in their formation.

This “soup” of matter is what gives rise to the emission, reflection and darkness nebulae that we observe. Our Sun is believed to have formed in exactly this way when a nearby supernova explosion affected the nebulae from which our Sun and solar system were born.

The image below is of the Trifid Nebula, named for the three largest lobes visible to those who first discovered it hundreds of years ago.

The reddish emission nebulae in the background appear to be divided into these lobes by the lines of dark nebulae in front of them. Upward from the red emission nebulae is a reflection nebula that glows with blue light.

nebulaPhoto: M20, the “Trifid Nebula” photographed by a 0.25 meter telescope in the Waasa Debaabing dome of the Killarney Observatory Complex

The compression of installed clouds of gas and dust, such as the Trifid Nebula, by a supernova shock wave (more on the Veil Nebula), or random collision with other interstellar clouds, creates eddies of gas that begin to condense together .

Creating a protostar

As these condensing balls of gas increase in mass, their gravitational pull increases and they begin to attract more material. This positive feedback loop continues until the ball of gas becomes massive: a protostar.

The large mass of a protostar constantly tries to crush its core, which in turn causes enormous densities and heat within the core.

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This accumulation of heat eventually exceeds 10 million degrees, hot enough for nuclear fusion of hydrogen to helium to occur and… a star to be born.

The external radiation generated by nuclear fusion is so great that, at least for most of the star’s life, it is able to counteract the crushing force of gravity.

Photo: M8, the “Lagoon Nebula” photographed by the 0.13 meter refractor in the Kchi Waasa Debaabing Dome of the Killarney Provincial Park Observatory Complex

In the image above of the Lagoon Nebula, notice the large number of bright stars just to the left of center. These are newly formed stars that are born within their stellar nursery of gas and dust.

Sister stars travel alone

Newly formed stars produce tremendous radiation pressure that pushes against the nebular cocoon of gas that surrounds them.

This constant pressure is so intense that over time it can completely expel the gas from the nebula, leaving few traces of its beautiful natal homes.

What remains is an open (loose) star cluster.

group of wild ducksPhoto: M11, the “Wild Duck Cluster”, photographed by the 0.25 meter refractor in the Waasa Debaabing Dome of the Killarney Provincial Park Observatory Complex.

The Wild Duck open cluster (shown above) is one of the richest open clusters in the sky, made up of a thousand stars.

Most clusters contain between a few dozen and a few hundred stars. The Sun formed this way, but it has long since separated from its stellar siblings, allowing it to embark on the next stage of its journey: using leftover gas and dust to form our solar system.

Do you want to continue reading?

To continue the story of our astronomical origins, here are the other installments of From the Big Bang to our provincial parks and beyond:

Note: Unless otherwise noted, all astronomical images used for this series were taken with equipment at one of our two observatories in Killarney Provincial Park; Waasa Debaabing, “see far (as far as the eye can see)” and Kchi waasa Debaabing, “see far away (as far as the eye can see).”