The Properties of Our Sun

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The Solar Atmosphere

Above the photosphere, transparent to light.

Unlike radiative zone, here atoms not totally ionized.

Therefore, there are electrons in atoms able to absorb light.

Absorption lines in solar spectrum are from these layers in the atmosphere.

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Atmospheric Composition

Probably same as interior.

Same as seen on Jupiter.

Same as the rest of the Universe.

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The Chromosphere

Very low density

But also very hot

Same as the gas tubes we saw in class and lab.

Energy from below excites the atoms and produces emission from this layer.

Predominant element – Hydrogen.

Brightest hydrogen line – Ha.

Chromosphere = color

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Spicules and Prominences

Emission from the atmosphere is very faint relative to photosphere.

Violent storms in the Chromosphere.

Giant curved prominances

Long thin spicules.

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Prominences

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Ha Sun

Photo by Robert Gendler

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Corona

Spicules and other magnetic activity carry energy up to the Transition Zone.

10,000 km above photosphere.

Temperature climbs to 1,000,000 K

Remember photosphere is only 5800 K

The hot, low density, gas at this altitude emits the radiation we see as the Corona.

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The X-Ray Sun

Q: At 1,000,000 K where does a blackbody spectrum have its peak?

A: X-rays

Can monitor the Solar Coronasphere in the X-ray spectrum.

Monitor Coronal Holes

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Solar Wind

At and above the corona:

Gas is very hot

Very energetic

Like steam above our boiling pot of water, the gas ‘evaporates’.

Wind passes out through Coronal Holes

Solar Wind carries away a million tons of Sun’s mass each second!

Only 0.1% of total Sun’s mass in last 4.6 billion years.