Giving up the ghost. The Sun occasionally throws off large amounts of hot, electrically charged gas in events referred to as coronal mass ejections. Thought to be due to instabilities in the solar magnetic field, CMEs can contain tens of trillions of kilograms of gas. This particular CME was observed in December 1996, as the Sun lay in the constellation Sagittarius, by one of the instruments on the SoHO spacecraft. The circular mask in the center of the image covers the Sun's bright photosphere to permit study of the tenuous corona. Image courtesy of SoHO/LASCO consortium. SoHO is a project of international cooperation between ESA and NASA. (carefully) Caught in the Act Note: NEVER look directly at the Sun, even for a short time. It can cause permanent damage to your vision without causing any physical pain. There are two ways to observe the Sun, from Earth and from outer space. The SoHO spacecraft is returning an enormous quantity of exciting data, but Earth-based observers, despite the problem of a rising and setting Sun, can also obtain excellent information-especially if they combine their efforts! A network of telescopes can be used for long observations in spite of the setting Sun. People used to say, "The Sun never sets on the British Empire," because the Sun was always shining on one of the British colonies scattered about the globe. Perhaps today people should say, "The Sun never sets on GONG" (the Global Oscillations Network Group). GONG incorporates six telescopes, at sites in Australia, Hawaii, California, Chile, Africa, and India, to piece together a continuous observation of the Sun that can last for days or weeks. Long observations by GONG provide much information on helioseismology, the branch of solar physics dealing with study of periodic motions on the Sun's surface. As earthquakes on Earth tell us about the inside of our planet, vibrations on the surface of the Sun communicate much about the internal solar structure. These experimental portraits of the Sun help test theories about the general workings of stars. There are several safe ways for anyone to observe the Sun indirectly with little or no equipment. The easiest device to use is a pinhole camera. The opening can be any shape; the round image of the Sun will appear in the shadow of the paper or cardboard if the hole is small enough. You can even make a pinhole camera with a hand, curling up a finger to make a small hole. Look only at the shadow, not through the hole directly at the Sun! The projected image will show the surface of the Sun. See "Making a Pinhole Camera" in this issue for three variations on this simple device. The Sun can also be viewed safely through special types of filters. Do not look at the Sun through any filter unless you know it to be safe. Safe filters include the following: Two layers of fully exposed (fogged) and developed black and white film (color film will not provide adequate protection, nor will film on which an image has been recorded [i.e., film not completely and evenly exposed]). See "Making a Solar Filter" in this issue for detailed instructions on how to prepare the film. A special metal-coated piece of plastic, typically aluminized Mylar. Double-sided coatings greatly reduce the possibility of filter defects. Metal coated glass is also available. Sources for these filters include: Rectangular welder's glass, shade No. 14. Less dense shades (lower numbers) are not suitable for direct solar observation. Welder's glass will produce a green-colored image. Many filters that are sometimes recommended for observing the Sun are not safe for direct-eye viewing, including a piece of glass blackened by soot from a candle, sunglasses, photographic neutral-density filters, and solar filters that operate at the eyepiece of telescopes or binoculars. Eyepiece filters are dangerous; they are placed at the point where the Sun's light is most concentrated and magnified. They can crack or even explode. BONNIE D. SCHULKIN works at the Harvard-Smithsonian Center for Astrophysics on educational outreach materials for the upcoming AXAF mission. She also dabbles in freelance writing, private tutoring, quilting, and volunteering at the Boston Museum of Science. Her email address is bschulkin@cfa.harvard.edu.

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