How do astronomers study the sun?
Juie Shetye  Star News  Astronomers have long used telescopes to zoom into the night sky, allowing us to witness dramatic phenomena like the birth and death of stars, monstrous back holes that can eat a million suns, and even collisions of entire galaxies. However, some astronomers prefer to observe at daylight, pointing at the sun with amazing special telescopes like the Dunn Solar Telescope, here in New Mexico. And what they observe is equally astonishing. Day after day the sun shines over us, steadily, as it has done for billions of years. We are used to the idea of a constancy to the sun. Few things are as tranquil as a sunny day. But astronomy shows that, if you get close enough, the sun is very far from constant. The sun is a mass of ionized gas, which goes by the fancy name of plasma  like in plasma TVs. With these telescopes, solar astronomers can derive information about the solar plasma, like its temperature and motion. Essentially, we can monitor the weather on the sun. Astronomers use these telescopes to zoom into the face of the sun, take very detailed photos, and build time-lapse movies of the motions we witness. With this approach they can zoom into areas that are smaller than a city on Earth, like Las Cruces. At these scales, we see details of sunspots, which are small dark circular regions on the sun, appearing dark to us because they are colder than the rest of the solar surface. By studying the time-lapse movies, we notice that these sunspots pulse, like a heartbeat, repeating every three to five minutes. Another interesting phenomenon on the sun is what we call coronal rain. Just like how it rains on the Earth, the sun also has rain, except that it is not made of water, but of the hot plasma from the corona falling back on the surface of the sun. A team of astronomers at New Mexico State University's Department of Astronomy is using these techniques, using telescopes to observe an area the size of New Mexico. At these scales, the images show a plethora of tall, slender jets, called spicules, each about the diameter of Las Cruces, and rising up 5,000 miles above the surface of the sun. Some of these jets seem like straws, grass and wheat fields. Other jets are clustered together. To most people looking at movies of these jets for the first time, they say they look like worms moving on the surface of the sun! Studying these events comes with a challenge, as some do not last long enough to track, and some move too fast to photograph. Easy, we use a high-speed camera! Astronomers take hundreds of images in a few seconds, and run the sequences of images in time. This shows how far the plasma within this jets has moved and allow us to identify the velocity of the motion. The spicules are very dynamic, they last for minutes, and move at 1,000 times the speed of a bullet, crossing an area the size of Las Cruces in one second. Imagine the shock waves that crossing the whole city in a single second would generate! Just as bullets cause vibrations and waves, these spicules can cause vibrations and waves in plasma. Some of these waves can dissipate energy in the form of heat, hinting at a possible solution to the long-standing problem of explaining why the sun is so hot. Sometimes these jets can travel across the solar atmosphere and cause events that can accelerate the solar wind and reach us here on the Earth, causing geomagnetic storms, making these jets the talk of the town. Geomagnetic storms are large disturbances on Earths magnetic field; if powerful enough, they can disrupt electrical systems and damage satellites, throwing our communication system and electric grid in disarray. It is an amazing feat of modern technology that we can trace these jets and their impacts as they originate from the sun and travel to the Earth. Understanding the sun is key to protecting the fragile thread that sustains our presence on the planet we have the privilege of calling home. Juie Shetye is an assistant professor of astronomy at New Mexico State University who is investigating such events. She can be reached at jshetye@nmsu.edu. More Star News: