Sometimes Gamma Cassiopeiae dims to 3rd-magnitude, while during other periods it shines as brightly as magnitude 1.6, as it did in the 1930s. That star is Gamma Cassiopeiae, the middle point in the W shape of Cassiopeia. If you’d like to seek out one of these for yourself, there’s a bright and easy-to-find eruptive variable in the northern sky - and you’ve probably seen it many times without knowing it. Gamma Cassiopeiae is the middle point of the "W"-shape constellation. Cassiopeia hangs above the glow of Northern Lights. Other stars are more dramatic, including a class of irregularly changing stars known as eruptive variables. Even the Sun is slightly variable, brightening and dimming over a roughly 11-year period by 0.1%. Variable stars are a large class of objects that amateur and professional astronomers have long chased for both fun and science. But over the next hundred thousand years or so, the radiation and winds from these stars will eat through the dust, allowing future skywatchers to see the many other stars that have been born there.Varies currently about 2.15 (historically 1.6–3.0)Ī variable star is a star that fluctuates in brightness over a period of time, perhaps less than a day, or maybe weeks, months, or years. Today, the stars in the Cassiopeia nebula are hidden inside a dense cloud of dust. The stars are similar to the brightest stars of the Orion Nebula, which is the largest stellar nursery in our region of the galaxy. A few years ago, astronomers discovered a tight cluster of several very young, hot, massive stars there. In addition to dead stars and stars that are about to die, Cassiopeia is also home to one of the largest collections of young stars in the galaxy. These elements may someday be incorporated into new stars, planets, or even living organisms. It contains lots of oxygen and other elements that will disperse into the galaxy. This material continues to expand into space as a giant shell. It blasted its outer layers into space at a few percent of the speed of light. One of those, known today as Cassiopeia A, exploded about three centuries ago as seen from Earth. The star could be building up to another eruption soon.Ĭassiopeia has produced two supernovae in recent centuries. The most recent expelled 20 times more material than is contained in all of the planets and moons of our solar system combined. Three times in the last six decades, it has blasted shells of gas into space. Actually, Rho Cas is in the process of doing just that. It may be just about as bright as a star can get without blowing itself apart. Rho Cas, which is to the right of Cassiopeia's W, is far bigger and more massive than the Sun and at least a half-million times brighter. It is about 10,000 light-years away, making it one of the most distant stars that is visible to the unaided eye. For a few days or weeks, it will outshine everything in the night sky except the Moon.Īnother of the constellation's stars, Rho Cassiopeia, is also destined to explode as a supernova. Eventually, the star will no longer be able to produce energy in its core, causing the core to collapse and its outer layers to explode as a supernova. That energy works its way to the surface and shines into space as visible light, ultraviolet, and other forms of electromagnetic energy. Such a monster produces a lot of energy through the nuclear reactions in its core. That's because Gamma Cas is about 15 times as massive as the Sun and hundreds of times wider. If you add up all of its energy - not just the light that is visible to the eye - it shines about 40,000 times brighter than the Sun. Gamma Cassiopeia is the star at the middle of the W. Cassiopeia looks like a flattened "W" against the frothy background of our home galaxy, the Milky Way. The best time to see her is in late fall, when she stands high in the northeastern sky during the evening hours.
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