Until space observations became possible we knew nothing about coronae in any other stars, and had only marginal information about the properties of stellar chromospheres. Now, space observations have shown us that a large fraction of the stars in the sky have chromospheres and coronae. X-ray telescopes carried on satellites have recorded flares in other stars that are far more powerful than the already impressive flares of the Sun. By deciphering the general pattern of stellar properties we can better under stand what makes things happen on the Sun. The Sun presents us with a bewildering variety of surface features, atmospheric structures, and active phenomena.
Sunspots come and go.
The entire Sun shakes and oscillates in several different ways at the same time. Great eruptions called prominences hang high above the Sun's surface for weeks, suspended by magnetic force, and then sometimes shoot abruptly into space from the corona. The explosions called solar flares emit vast amounts of radiation and atomic particles in short periods of time, often with little or no warning. Space observations have discovered many new aspects of solar events that were hidden from ground based observatories. The hottest spots on the Sun shine primarily in ultraviolet and X-rays, rather than in visible light.