Watch: Three Years of the Sun
NASA launched a satellite to observe the Sun in February 2010 called the Solar Dynamics Observatory - SDO for short. It carries a telescope for viewing the Sun in incredible detail that is much better than earlier orbiting solar observatories. SDO is sort of like a Hubble Space Telescope for viewing the Sun.
This movie shows a time-lapse view of the Sun from SDO spanning the satellite's first three years of operation. The Sun spins around once every 27 days, but in this movie it spins once every few seconds because the movie is sped up a lot.
The first part of the movie shows the Sun in ultraviolet (UV) "light". UV light comes from hot, high-energy features in the Sun's atmosphere. Most of the bright regions in UV images of the Sun are near "active regions" that form around sunspots. Sunspots appear in places where the Sun's magnetic field is highly disturbed. The solar magnetic field near a sunspot is often a thousand times stronger than elsewhere on the Sun. Huge solar "storms" - solar flares and coronal mass ejections (CMEs) - usually erupt from these magnetically disturbed active regions. You can also see glowing loops of superheated plasma - sort of an electrified gas - arching over the active regions in these UV images. These coronal loops reveal magnetic fields in the Sun's atmosphere in much the same way that iron filings sprinkled over a horseshoe magnet reveal the shape of the magnet's force field.
The latter part of this movie shows the Sun in four different wavelengths of "light" - called electromagnetic radiation in science. The top-left view, marked "4500 Ångstroms", is normal, visible light like our eyes see. The other three views show different wavelengths of UV "light". The different UV wavelengths are like different colors of light. Each wavelength reveals different aspects of the Sun. The 304 Ångstroms image (lower right) shows features in the Sun's lower atmosphere, called the "chromosphere". The chromosphere is hotter than the Sun's visible surface (the photosphere), which is what we see in the visible light image. The other two views - 171 Ångstroms (lower left) and 193 Ångstroms (upper right) - show higher energy UV images of the Sun. They provide a view of the Sun's upper atmosphere, called the corona (the Latin word for crown). The corona is even hotter than the chromosphere, with temperatures reaching millions of degrees. The fuzzy glow we see around the Sun during a solar eclipse is the corona.
Can you see how the bright areas in the UV images often appear in the same place as sunspots in the visible light image?