pp chain reaction in stars

Twinkle, twinkle little star,
How I wonder what you are.
Giant thermonuclear reaction;
Held by gravitational attraction.
Twinkle, twinkle little star,
You look so small ’cause you’re so far.

As you burn through constant fusion,
Your twinkle’s just an optical illusion.
That happens when your light gets near;
distorted by our atmosphere.
Twinkle, twinkle little star,
spreading light and heat so far.

As you use up fuel you’ll grow,
and give off a scarlet glow;
Maybe you’ll go supernova,
exploding elements all over.
Now I know just what you are;
and I know I’m made of stars.

Where does the Sun get its energy? A straightforward question but physicists struggled to find an answer until the 1920s, when Eddington suggested that nuclear fusion might be responsible.

A star is drawing on some vast reservoir of energy by means unknown to us. This reservoir can scarcely be other than the subatomic energy which, it is known exists abundantly in all matter; we sometimes dream that man will one day learn how to release it and use it for his service. The store is well nigh inexhaustible, if only it could be tapped. There is sufficient in the Sun to maintain its output of heat for 15 billion years. — Sir Arthur Stanley Eddington

Read morepp chain reaction in stars

AH: the Hertzsprung Russell diagram

Our Sun is a typical yellow star, so its emission would be represented by the middle star in this image.

star_colors
image courtesy of kstars, kde.org – colour is exaggerated

The colour of a star also tells us something about the expected behaviour of a star, it’s lifetime, and destiny. This is achieved by plotting stars on a Hertzsprung-Russell diagram. More about HR diagrams here.

This video clip looks at how the stars are arranged on the HR diagram.

Hertzsprung Russell diagram from mr mackenzie on Vimeo.

While some HR diagrams use temperature along the x-axis, others use star classification.

Read moreAH: the Hertzsprung Russell diagram

pp chain fusion in stars

Twinkle, twinkle little star,
How I wonder what you are.
Giant thermonuclear reaction;
Held by gravitational attraction.
Twinkle, twinkle little star,
You look so small ’cause you’re so far.

As you burn through constant fusion,
Your twinkle’s just an optical illusion.
That happens when your light gets near;
distorted by our atmosphere.
Twinkle, twinkle little star,
spreading light and heat so far.

As you use up fuel you’ll grow,
and give off a scarlet glow;
Maybe you’ll go supernova,
exploding elements all over.
Now I know just what you are;
and I know I’m made of stars.

Where does the Sun get its energy?  A straightforward question but physicists struggled to find an answer until the 1920s, when Eddington suggested that nuclear fusion might be responsible.

A star is drawing on some vast reservoir of energy by means unknown to us. This reservoir can scarcely be other than the subatomic energy which, it is known exists abundantly in all matter; we sometimes dream that man will one day learn how to release it and use it for his service. The store is well nigh inexhaustible, if only it could be tapped. There is sufficient in the Sun to maintain its output of heat for 15 billion years. — Sir Arthur Stanley Eddington

Read morepp chain fusion in stars

the Hertzsprung-Russell diagram

Our Sun is a typical yellow star, so its emission would be represented by the middle star in this image.

star_colors
image courtesy of kstars, kde.org – colour is exaggerated

The colour of a star also tells us something about the expected behaviour of a star, it’s lifetime, and destiny.  This is achieved by plotting stars on a Hertzsprung-Russell diagram.  More about HR diagrams here.

This video clip looks at how the stars are arranged on the HR diagram.

Hertzsprung Russell diagram from mr mackenzie on Vimeo.

While some HR diagrams use temperature along the x-axis, others use star classification. 

Read morethe Hertzsprung-Russell diagram

100 years of general relativity

einsteinshow.php

It seems general relativity is 100 years old today. We’ve been struggling a bit with this topic, so I thought these videos might help.

Why Einstein is such a big deal from Fusion Media Network on Vimeo.

General relativity explained in under 3 minutes from Fusion Media Network on Vimeo.

Science Museum – Einstein’s Cosmos from ORDER Productions on Vimeo.

#Einstein100 – General Relativity from Eoin Duffy on Vimeo.

star colours

Astronomers often refer to the colour of a star, which seems a bit odd because we mostly see stars as white twinkly objects.  However, even with the naked eye, we can look closely at certain stars and detect a hint of colour – just look at this image of the Orion constellation.  As we view him, the left shoulder has a red coloured star, while the right shoulder and right foot appear to be blue.

320px-Orion_3008_huge

image: Orion 3008 huge.jpg, Wikipedia

Now click on the image to see the same view at much higher resolution.  In the hi-res photo, look at the stars in the background.  They’re not all white!

What can the colour of a star tell us?

Read morestar colours