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Another NASA Success: Solar Dynamics Observatory

April 22, 2010

On February 11, NASA launched into orbit 1,600 miles above the surface of the Earth an Atlas V rocket containing the Solar Dynamics Observatory, a new space telescope designed to study the sun.  Since then, NASA has raised the orbit to about 22,000 miles and brought its three instruments online. 

The first  instrument is called the Extreme Ultraviolet Variability Experiment (EVE).  Extreme ultraviolet photons are the part of the sun’s output that have a significant impact on the Earth’s atmosphere and on our artificial satellites.  EVE will allow scientists to study the sun’s effects on GPS satellites, for example.

The Helioseismic and Magnetic Imager (HMI) will allow scientists to observe the goings-on inside the sun that create the effects we can observe on the solar surface.  Right now, there are a lot of questions about events inside the sun that lead to things like sunspots.   HMI will return data that will allow astronomers to link related solar events to one another.

 Finally, the Atmospheric Imaging Assembly (AIA) allows the Solar Dynamics Observatory to return unprecedentedly clear images of the sun in several wavelengths that will be key to developing a fuller understanding of our near star.

After 2 months of startup procedures, the SDO has come online. Yesterday, NASA displayed the first clips of video data returned by the SDO. To call it stunning would be an understatement.

In case you need to brush up on just what the sun is, I will include a passage from a book I just finished called Death From the Skies. Its author, Phil Plait, Ph.D. is a skillful writer and speaker whose love for his subject oozes from his charmingly-energetic prose. Here’s his introduction to a section about the sun:

Invariably [in astronomy textbooks], there will be some permutation of this sentence, “The Sun is an ordinary, average star.”

If you decide to read only this chapter and then close this book forever, then please walk away with just one thing: the Sun is a star, with all that this implies. The sun is a mighty, vast, furiously seething cauldron of mass and energy. The fires in its core dwarf into microscopic insignificance all the nuclear weapons ever built by mankind. A million earths would be needed to fill its volume, and the light it emits can be seen for trillions upon trillions of miles. Invisible forces writhe and wrestle for control on its surface, and when it loses its temper, the consequences can be dire and even lethal.

That is what it means to be an ordinary star.

The Sun is about 93 million miles away. If you could build a highway and drive there, it would take over 170 years. Even an airplane would take two decades to fly to the Sun if it could.

And yet…The sun is so bright that you can’t even look at it. And if you stand [outside in the summer] for more than a few minutes you risk damaging your skin.

The Sun’s fearsome power is generated deep in its core, where a controlled nuclear reaction is taking place: the Sun is continuously fusing nuclei of hydrogen together to create helium nuclei. Every time this reaction occurs, a little bit of energy is given off…every second of every day, the Sun converts 700 million tons of hydrogen into 695 million tons of helium.

The missing 5 million tons gets converted into energy, via Einstein’s famous equation E = mc^2.

Plait goes on for pages, but I’ll stop there. Keep in mind that hydrogen is the lightest element: twice as light as helium which keeps balloons afloat. The upshot is that 5 million tons of hydrogen is an ENORMOUS amount. The sun is fucking nuts.

One Comment leave one →
  1. David permalink
    April 22, 2010 4:04 pm

    Dude, poor choice of topics on Earth Day! If you’re going to blog about the sun, do it on Sunday! You know, Sunday. The first day of the week. The day between Saturday and Monday. The day I like to refer to as “my day.”

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