Shadow of the planet Venus during it's transit of the Sun on June 5th, 2012 at approximately 18:00 Central Time. Photograph taken from the MH Solar Observatory in St. Louis, MO, USA.
It’s pretty amazing how ecstatic seeing a simple circle with a little blobby dot can make a person feel. Following Ron Hipschman’s instructions, I installed a small aperture (~0.5 mm) solar projector at the newly established Muddle Home Solar Observatory (MHSO). The kids and I used it, and SunAeon’s app, to observe Venus transiting the Sun. It was, in a word, awesome.
The MHSO's small aperture (pinhole), solar projector.
For us the transit occurred late in the day, so by the end we had trees getting in the way.
Trees beginning to obscure the Sun.
If it seems odd that the trees are at the top of the image, it’s because the images in pinhole projectors are inverted. If I flip it around the right way, the image would actually look like this.
Corrected (inverted) image from the pinhole projector.
This video from NASA (via physorg.com) includes a nice little section showing the movement of charged particles (cosmic rays) through the Sun’s magnetic field. What’s really neat, is that the Voyager spacecraft (now 33 years old) have discovered magnetic bubbles at the edge of the solar system that make the particles dance a little. It’s a wonderful application of the basic principles of electricity and magnetism.
Comet colliding with the Sun coincides with a coronal mass ejection. Image from the NASA SOHO Observatory.
SOHO scientists think that coronal mass ejection that happens right after the comet hits the Sun was probably not caused by the collision. But it looks really cool.
Expanding globe of debris from the explosion of Tycho's Star. Tycho Brahe observed the star as it went supernova about 540 years ago. The red is the debris, the stardust, created by the explosion. Image from NASA.
We could have been talking about the nuclear meltdowns in Japan, but I’m not sure. Our conversations tend to wander. I remember trying to explain where the carbon atoms, that are so essential for life, came from. It’s been a while since we saw this topic, so I figured it wouldn’t hurt to go it over again. And then I found this wonderful image of the Tycho supernova from the Chandra space telescope. Supernovas are where the heaviest atoms are formed.
In the beginning … the big bang created just the smallest elements, hydrogen and helium. But even these tiny things have gravity, so they pull each other together until there’s so much stuff that the pressure at the center of the clump is enough to fuse hydrogen atoms together.
Now fusion is easy to confuse with chemical bonding that occurs around us every day. After all, the hydrogen in the atmosphere is usually in the form of H2, which is two hydrogen atoms bonding together by shared electrons.
With fusion, on the other hand, the single protons that make up the nuclei of the hydrogen atoms are pushed together to create a bigger atom, helium. I say pushed together, because it takes a lot of pressure to fuse atomic nuclei. And it also releases a lot of energy. Notice all that heat and radiation that comes from the Sun? All that energy was created by the fusion of hydrogen atoms; the smallest element, hydrogen, fuels the stars.
Fusion of two hydrogen atoms to create helium, compared the chemical bonding of hydrogen atoms to produce hydrogen gas (H2). The nutrons are left out for clarity.
The huge amounts of energy released by fusion makes fusion power one of the holy grails of nuclear energy research. If we were able to create and control self-sustaining fusion reactions, just like what happens in the Sun, we would have a source of tremendous energy. There is a lot of research in this area. Some people have figured out how to build fusion reactors in their basements, but these use a lot more energy than they produce so they’re not very useful as a power plant (Barth, 2010). The ITER reactor, currently being built in France, aims to be the first to produce more electricity than it uses.
Now back to the stars. Hydrogen atoms fuse to form helium, but it takes a lot more pressure to create larger atoms: carbon has six protons, nitrogen seven, and oxygen eight. These elements are essential for life (as we know it). The only time stellar forces are great enough to produce these are when stars explode; an exploding star is said to have gone nova. Bigger atoms, like iron (26 protons), gold (79 protons), and uranium (92 protons) need even greater forces, forces that only occur when the largest stars go supernova.
DNA. (from Wikipedia)
So if these elements are only produced in novae and supernovae, how did they get to Earth? How did they get into your DNA?
Well when stars explode, a lot of these newly formed elements are blasted off into space. It’s a sort of cosmic dust. We could even call it stardust. It’s matter, just like the hydrogen and helium from the big bang, only bigger, which means they have more mass, which means they have more gravity.
Formation of the solar system (model).
The gravity pulls the stardust together with the hydrogen and helium sill floating around in space (there’s a lot of it), to form new stars, and, now that there are the larger elements to create them, rocks, asteroids, and planets.
So, if you think about it, some stars needed to have been formed, lived their lives (which consists of fusing hydrogen atoms until they run out), and exploded to create the matter that makes up the planets in our solar system and the calcium in our bones, the sodium in our blood, and the carbon in our DNA.
Notes:
1. Lots of information about Tycho’s Star on SolStation.com.
We’ve seen that autotrophs get their energy from sunlight or chemical reactions, while heterotrophs get their energy from eating other organisms. We’ve also seen that some protists, called mixotrophs, can do both.
We have not yet discussed reptiles, which are heterotrophs (as are all members of the Domain Animalia), but use the sun to regulate their internal temperature (they’re ectotherms).
The researchers used the pigment to make their own solar cell, but it proved to be quite inefficient, only converting 0.335% of the incoming light to electricity. However, the microscopic ridges on the hornet, and the layering of the insect’s cuticle, suggest that the hornet itself is more efficient.
I’m not quite sure how the hornets would use the electricity if that’s what they’re doing, but they are more active in sunlight than in the dark, so some type of “solar harvesting” is probably going on.
SketchUp model of our simple solar heat collector.
For real experiential learning, projects should have useful, practical applications. This passive, solar heat collector window unit seems pretty easy to build (you’ll find out more about it in about a week). It’s passive because there are no fans to push the air through the collector, the air flows through it because of the hot air in the upper channel rises, creating a siphoning effect that drags cool air into the lower chamber. With a couple solar cells and spare electric motors from some toy cars, however, we should be able to turn it into an active, forced-convection heater. What’s nice, is that we can now demonstrate two methods of capturing solar energy.
Solar powered fans for forcing convection in the solar collector
This project may also work well if it’s split into two, the solar collector and the photoelectric fan system, and at the end the students bring them both together to create a single unit.
Directions to build similar units can be found on the Build it Solar website and the Solar Heater page. Mother Earth News has an article from 1977 on how to construct one. These images were produced from a Google SketchUp model, which is really useful in trying to prototype little constructions like this. Though, I probably spend too much time trying to get the models to look just right.
