Origami is an ancient Japanese style of paper folding. However, it is not only a decorative art form. Rather, origami provides solutions to many problems in modern science and engineering. For example, origami-inspired techniques are used to unfold stents in clogged arteries, release airbags during automobile collisions, and even unfurl the large mirror for the soon-to-belaunched James Webb Space Telescope. In astrophysics, there are instances where the expansion and unpacking of origami demonstrates what scientists witness. Take the death of stars. When a star about 10 to 15 times more massive than our Sun runs out of nuclear fuel, it will collapse onto itself and then create a giant explosion. This energetic event, known as a supernova, hurls the outer layers of the star into space, creating an elegant tapestry of energy and stellar debris. NASA’s Chandra X-ray Observatory has looked at many of these explosions and the debris fields they leave behind (called “supernova remnants”.) On this web site, we will explore how to use origami to understand the death of a massive star and its transformation into its own unique cosmic pattern.
An airbag is a ubiquitous piece of equipment in most cars these days. But if you think about how they have to work, airbags have to open very quickly and become sturdy enough to protect the passenger. What's the best way to do that? Create a 3-D polyhedron from a flat sheet with folds.
In medicine, origami techniques are often applied via stents, which are collapsible tubes that can be inserted into a patient’s veins or arteries to a site of a clot. When deployed, the stent, which can be made of bioplastics or other similar materials, expands to open the vein or artery to critically improve blood flow.
NASA's James Webb Telescope (JWST) is expected to launch in 2018. It is a large infrared telescope with a main mirror of 6.5-meters that will study the history of the Universe, from the first glow after the Big Bang, to the formation of solar systems. But with a mirror that size, how do you get it fit inside a rocket? The answer is origami. The NASA engineers had to segment it so that it could be folded up for the rocket and then unfolded in space. Instead of using glass for the primary mirror, the engineers used beryllium instead—making the mirror incredibly light.
Every 50 years or so, a massive star in our galaxy blows itself apart in a supernova explosion. Supernovas are one of the most violent events in the universe, and the force of the explosion generates a blinding flash of radiation, as well as shock waves analogous to sonic booms. How does it happen? When the nuclear power source at the center or core of a star is exhausted, the core collapses. In less than a second, a neutron star (or a black hole, if the star is extremely massive) can be formed. The formation of a neutron star releases an enormous amount of energy in the form of neutrinos and heat, which reverses the implosion. All but the central neutron star is blown away at speeds in excess of 50 million kilometers per hour as a thermonuclear shock wave races through the now expanding stellar debris, fusing lighter elements into heavier ones and producing a brilliant visual outburst that can be as intense as the light of several billion Suns.
The intense radiation emitted by a supernova lasts from several months to a few years before fading away. In the meantime, the rapidly expanding (millions of miles per hour) matter from the explosion eventually crashes into circumstellar gas. This collision creates a supernova remnant consisting of hot gas and high-energy particles that glow in radio through X-ray wavelengths for thousands of years.
The process of forming the remnant is somewhat like an extreme version of sonic booms produced by the supersonic motion of an airplane. Expanding stellar debris creates a shock wave that races ahead of the debris. This forward shock wave produces sudden, large changes in pressure and temperature behind the shock wave.
The forward shock wave also accelerates electrons and other charged particles to extremely high energies. Electrons spiraling around the magnetic field behind the shock wave produce radiation over a wide range of wavelengths.
X-rays are produced by the forward shock wave and by a reverse shock wave that heats the debris, or ejecta, of the exploded star. The reverse shock is formed as the high pressure gas behind the forward shock wave expands and pushes back on the stellar ejecta.
A Chandra observation of the supernova remnant Cassiopeia A (Cas A) clearly shows both the outer shock wave and the debris heated by the reverse shock wave. The study of supernova remnants with radio, infrared, optical and X-ray telescopes enables astronomers to trace the progress of the shock waves and distribution of elements ejected in the explosion. These data are especially significant because supernovas are the primary means for seeding the galaxy with many elements such as carbon, nitrogen, oxygen, silicon and iron that are necessary for planets and life.
More on the James Webb Space Telescope: https://jwst.nasa.gov/about.html
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