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29/10/09 How Far Is Our Sun From The Galactic Plane? [200 words] We aren’t exactly sure. Estimates are between 44,000 Light Years and 65,000 Light Years. By observing the hydrogen gas that envelopes our galaxy scientists deduced we are above the mid plane of the galaxy. There are some reasons why we are unclear. Firstly, we are unsure exactly how large the galaxy is or even what shape it is! As recently as 2005 scientists revised our outlook when it was discovered our galaxy had a barred line of stars in the centre. Secondly, we cannot directly determine the distance between any two points in our galaxy with complete accuracy. This is simply because everything is moving without a known frame of reference. All astronomical measurements are given with a margin of error to take this into account. This is given as the figure ± with certain measurements. Thirdly, the fact that the Milky Way divides our night sky into two roughly equal parts suggests that we must be close to the galactic plane. This is because if we were further above or below we would see a greater concentration of stars on one side of the sky. Effectively we are looking at a cross section of our galaxy, made up of the stars and nebulae we can see in the sky. 3/11/09 Why Don’t We See Any Green Stars? [180 words] Though we cannot ‘see’ any green stars, we know they exist, that is stars that emit most of their light in the green frequency, In fact, the Sun’s frequency peaks at blue green; yet it appears yellow. Simply put, it peaks in blue green, but it still emits light at other colours.

Jack Oughton - Short Astronomy Magazine Articles

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Some short 'Q&A' style science articles written with the intent for eventual publication in an astronomy magazine.

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Page 1: Jack Oughton - Short Astronomy Magazine Articles

29/10/09

How Far Is Our Sun From The Galactic Plane? [200 words]

We aren’t exactly sure. Estimates are between 44,000 Light Years and 65,000 Light Years. By observing the hydrogen gas that envelopes our galaxy scientists deduced we are above the mid plane of the galaxy.

There are some reasons why we are unclear.

Firstly, we are unsure exactly how large the galaxy is or even what shape it is! As recently as 2005 scientists revised our outlook when it was discovered our galaxy had a barred line of stars in the centre.

Secondly, we cannot directly determine the distance between any two points in our galaxy with complete accuracy. This is simply because everything is moving without a known frame of reference. All astronomical measurements are given with a margin of error to take this into account. This is given as the figure ± with certain measurements.

Thirdly, the fact that the Milky Way divides our night sky into two roughly equal parts suggests that we must be close to the galactic plane.

This is because if we were further above or below we would see a greater concentration of stars on one side of the sky. Effectively we are looking at a cross section of our galaxy, made up of the stars and nebulae we can see in the sky.

3/11/09

Why Don’t We See Any Green Stars? [180 words]

Though we cannot ‘see’ any green stars, we know they exist, that is stars that emit most of their light in the green frequency, In fact, the Sun’s frequency peaks at blue green; yet it appears yellow.

Simply put, it peaks in blue green, but it still emits light at other colours.

This is important for a number of reasons. In the spectrum of visible light, green is in the centre. Stars emitting at this wavelength are strongly in the middle of the colour spectrum. As a white beam of light from a prism is split into a rainbow of colours, stars emitting green also put out a lot of red and blue, making them appear white.

There are some other reasons; Firstly, human eyes have evolved to be more sensitive to certain colours. Since green is seen alongside with other colours on this star’s wavelength, the eye notices the reds and blues more.

Another factor is the earth’s atmosphere; it acts like a colour filter, which emphasizes light frequencies of a smaller wavelength by splitting light and scattering more of the smaller waves. This is called Rayleigh scattering; as human

Page 2: Jack Oughton - Short Astronomy Magazine Articles

eyes aren’t very sensitive, we notice the overwhelming amount of blue that is scattered, about four times more than red light.

3/11/09

Why Is the Sun’s Corona Much Hotter Than The Surface? [220 words]

We aren’t really sure. Current theories suggest a number of possibilities, here are two of them.

Magnetic Reconnection

This is caused by energy conservation. A tapered whip conserves the energy added into it’s thicker end, even as it travels down to the thinner tip. That force is finally released in kinetic motion as the whip’s crack.

This same amplification process may occur in the corona. An input of kinetic energy at the base of the corona is amplified, and travels away from the base of the corona. As the density of gasses decreases with the distance, this same amount of energy has an even greater effect. This energy causes the gasses furthest from the base of the corona to travel faster and faster, heating the gaseous plasma more and more the further you get!

Alfven Waves

This theory develops on our previous theory of energy transfer through magnetism. The sun's corona is threaded with morphing, unpredictable magnetic fields. It is believed that magnetic waves transport the sun’s energy outwards on hot gas ions radiated from the sun. Like ripples traveling across a lake, these Alfven waves move energy through the coronal plasma (which is fluid, like water). Evidence supporting this theory was recently discovered when scientists observed ripples traveling outward from the sun at 9 million miles per hour.