The human eye can only see a very small fraction of the electromagnetic spectrum, less than a billionth of a billionth of the whole thing. Considering the amazing things we can see with our own eyes, what wonders are we missing out on with the rest of it? Fortunately we have developed instruments that can detect much of the rest of it and software that can turn this data intopictures that our eyes can interpret.
The image below represents eleven slices of the electromagnetic spectrum (and two other forms of detection in greyscale), only two of which are normally visible to the human eye. All of these images were taken of the same event and yet look very different. This demonstrates how you can observe many different things from a variety of wavelengths.
Six of the images are depicting the emission spectra of eight different iron ions at various temperatures ranging from 600,000K – 20,000,000K (1,000,000 – 36,000,000°F). These highlight varying parts of the sun’s corona and flares, giving indications as to the local magnetic field lines of the sun. One of them is looking at a piece of helium’s emission spectrum at 50,000K (90,000°F) and tells us about the sun’s chromosphere (upper atmosphere). Another looks at 160nm, belonging to carbon at 10,000K (17,000°F), giving hints about the uppermost portion of the sun’s photosphere (lower atmosphere).
Three of the other images show portions of the spectrum given off by the sun’s black body radiation. Each of them reveals details of the sun’s photosphere (surface) and indicates temperature differentials. One of them is in the ultraviolet, 170nm, another in the visible range, 450nm (blue/purple), and the last is a broad sweep of the visible spectrum, what it would look like to the human eye.
This image only covers pieces from 9.4nm to about 7000nm: low energy x-rays, ultraviolet, and visible light; it doesn’t incorporate gamma rays, high energy x-rays, infrared, microwave, or radio waves, each of which can yield its own fascinating discoveries. Imagine what more there is for us to see and learn by looking at the universe with “wider” eyes!
In the next few days I’ll be covering some of these topics in more detail such as the composition and range of temperatures of the sun, how these things produce different wavelengths of light, what the two greyscaled images are, and what different wavelengths reveal about the rest of our universe.
Neptune has 13 moons, and the largest of them, Triton, has a rather unusual feature. It has a retrograde orbit – it orbits Neptune in the opposite direction to the planet’s spin, and it is the only large moon in our solar system to do so. It takes speedy 5.87 earth days for this rebel moon to complete an orbit around Neptune.
In addition to being the odd one out in terms of its orbit, Triton also has a surprising composition. Underneath its frozen nitrogen crust lies an icy mantle, which houses a core made of rock and metal. Triton’s density of 2.050 g per cubic cm (one of the most dense of the outer solar system satellites) suggests that is has a higher rock content than the other icy moons that orbit Saturn and Uranus. Overall, Triton’s composition is remarkably similar to that of dwarf planet and Kuiper Belt object, Pluto.
Triton’s unusual orbit, coupled with its unexpected composition, suggests that Triton was originally part of the Kuiper Belt. Instead of being formed at the same time as Neptune, Triton was instead captured by Neptune’s gravity and coaxed into orbit.
This geologically active moon, which spews out nitrogen gas, has an orbital eccentricity of almost zero; it is nearly a perfect circle. Tidal forces, caused by interactions between the two bodies’ gravitational fields, cause Triton’s orbit to decay. Currently, Triton orbits at a distance of 354,759 km from Neptune; this is closer than our moon orbits the Earth. In an estimated 3.6 billion years, it is thought that the moon may pass the Roche limit (the limit by which the moon’s gravity can no longer withstand the pull of Neptune and thus disintegrates) and be torn apart, creating a ring system similar to that of Saturn.
From the odd way it orbits Neptune, to vomiting nitrogen and eventually meeting a violent demise, Triton should definitely call it a night.