While solar wind is constant, the sun's emissions go through a roughly 11-year cycle of activity. "Some of the dominant colors seen in aurorae are red, a hue produced by the nitrogen molecules, and green, which is produced by oxygen molecules." "Every type of atom or molecule, whether it's atomic hydrogen or a molecule like carbon dioxide, absorbs and radiates its own unique set of colors, which is analogous to how every human being has a unique set of fingerprints," Teets told. The bright colors of the northern lights are dictated by the chemical composition of Earth's atmosphere. "These particles are deflected towards the poles of Earth by our planet's magnetic field and interact with our atmosphere, depositing energy and causing the atmosphere to fluoresce," said astronomer Billy Teets, the director of Dyer Observatory at Vanderbilt University in Nashville, Tennessee. In the Northern Hemisphere, the phenomenon is called the northern lights (aurora borealis), while in the Southern Hemisphere, it's called the southern lights (aurora australis). When that wind slams into Earth's ionosphere, or upper atmosphere, the aurora is born. (Image credit: NASA) What are the northern lights?Īt any given moment, the sun is ejecting charged particles from its corona, or upper atmosphere, creating what's called the solar wind. A portion of the space station's solar array is visible in the top left corner of the image. At the time this photo was taken, the space station was orbiting about 258 miles (415 kilometers) above Russia and the Ukraine. The theory would eventually prove correct, but not until long after Birkeland's 1917 death.Ī lime-green aurora glows above Earth's city lights in this view from the International Space Station. Norwegian scientist Kristian Birkeland proposed that electrons emitted from sunspots produced the atmospheric lights after being guided toward the poles by Earth's magnetic field. The science behind the northern lights wasn't theorized until the turn of the 20th century. also notes the aurora, according to NASA (opens in new tab). A royal astronomer under Babylon's King Nebuchadnezzar II inscribed his report of the phenomenon on a tablet dated to 567 B.C., for example, while a Chinese report from 193 B.C. One North American Inuit legend (opens in new tab) suggests that the northern lights are spirits playing ball with a walrus head, while the Vikings thought the phenomenon was light reflecting off the armor of the Valkyrie, the supernatural maidens who brought warriors into the afterlife.Įarly astronomers also mentioned the northern lights in their records. The NASA Hubble Space Telescope took this picture of an aurora on Jupiter using ultraviolet (UV) light.Since that time, civilizations around the world have marveled at the celestial phenomenon, ascribing all sorts of origin myths to the dancing lights. These swirls of red light are an aurora on the south pole of Saturn. We've seen amazing auroras on Jupiter and Saturn. If a planet has an atmosphere and magnetic field, they probably have auroras. They sure do! Auroras are not just something that happen on Earth. This is the name for an aurora in the Northern Hemisphere. These green bands of light in the winter sky above Alaska are an aurora borealis. There, the particles interact with gases in our atmosphere resulting in beautiful displays of light in the sky. When a solar storm comes toward us, some of the energy and small particles can travel down the magnetic field lines at the north and south poles into Earth's atmosphere. During one kind of solar storm called a coronal mass ejection, the Sun burps out a huge bubble of electrified gas that can travel through space at high speeds. There is a constant streaming solar wind and there are also solar storms. The protective magnetic field around Earth shields us from most of the energy and particles, and we don't even notice them.īut the Sun doesn't send the same amount of energy all the time. The Sun sends us more than heat and light it sends lots of other energy and small particles our way. This beautiful view of the aurora was taken from the International Space Station as it crossed over the southern Indian Ocean on September 17, 2011.Įven though auroras are best seen at night, they are actually caused by the Sun. If you're near the South Pole, it is called an aurora australis or the southern lights. If you're near the North Pole, it is called an aurora borealis or northern lights. Frequently there are beautiful light shows in the sky. If you're ever near the North or South Pole, you may be in for a very special treat. Watch this video to learn all about auroras! Click here to download this video (1920x1080, 277 MB, video/mp4).
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