Stars Flashcards
Protostar
A precursor to a star which is born in a nebula. The dust and gas condenses and begins to heat up. Once it condenses enough, the hydrogen fuses to form helium and it turns into a Main Sequence Star. If the mass of dust and gas isn’t large enough to begin this fusing process, it forms a Brown Dwarf instead.
Main Sequence Star
A star in which the hydrogen is fusing to form helium. An example is our Sun in its current form. The smaller the star, the longer it burns. A star with one solar mass takes almost 10 billion years to complete the transformation of all of its hydrogen into helium. Larger stars fuse their hydrogen much more quickly and therefore end the Main Sequence stage sooner.
Red Giants and Blue Giants
A Main Sequence Star which has fused all of its hydrogen into helium. As the hydrogen disappears, the star begins to swell and cool. As it swells it will begin to lose gases around the white dwarf core in the form of a planetary nebula.
• Contrary to what the green bean farmers will have you believe, there is no such thing as a “Green Giant” and that includes stars, too.
White Dwarf
Comparable in size to Earth but comparable in mass to the sun. Instead of nuclear fusion like a Main Sequence star, they are powered by the leftover energy remaining in the core. (I like to think of them as glowing embers) They are less luminous than the Sun and usually take several billion years to fade.
Super giant
A byproduct of a star with larger mass. Instead of turning into a Red Giant after its Main Sequence Stage, larger stars (above 10 solar masses) become Supergiants. With a rapidly expanding shell of gases around the core, they can be up to 1000 times the diameter of our Sun. The difference between a Supergiant and Red Giant, apart from size, is in how they die. A Supergiant tends to do so in a violent explosion as the core collapses upon itself in less than a second. This is known as a Supernova.
Supernova
An event that occurs when a massive star undergoes a gravitational collapse. The resulting supernova explosion produces extreme luminosity which can temporarily out outshine an entire galaxy. If the core survives the explosion, it forms a Neutron Star or a Black Hole.
Neutron Star
The remnants of a star that dies through particular types of supernova gravitational collapses. Very small and very dense. Generally have less than three solar masses. Anything larger than three solar masses and the core will collapse onto itself forming a Black Hole.
Black Hole
A gravitational vacuum from which even light cannot escape. Formed after a supernova when the core collapses upon itself, black holes consume nearby matter which may include stars or even other black holes.
Pulsar
A type of neutron star which emits radiation that appears as a pulse when observed from Earth. This is due to the star rapidly spinning and emitting energy. When the rotation points it towards Earth, we see the energy released as a “Pulse”.
Binary Star
A star system made up of two stars orbiting around a common center point. Many of the stars you see in the night sky may actually be a binary star system. The two stars are so close that the light appears to be coming from a single point.
Blue Stars
Otherwise known as Class O stars, they are the hottest of the Main Sequence Stars. A Blue Supergiant, which can have surface temperatures around 40,000 degrees Kelvin or higher, is one of the hottest types of stars known to exist. Remember that a blue star burns hotter than a red star.
Cepheids
Pulsating variable stars. They change luminosity at very regular intervals and by very regular amounts. This behavior makes them excellent ‘standard candles’ and they are thus useful for determining distances in space.
Nebula
The birthplace of stars. These large collections of hot gasses and dust are interstellar nurseries where stars are born.
Metalliticity Classification
The Population I, II, III classification system indicates the metallicity of stars. This is important because it is believed that by using this we can determine a star’s age.
Population III Stars
The lowest of mental content and thus the oldest. When they were formed there wasn’t much metal in the unvierse. These are still unobserved since it is belived most of them went supernova soon after the universe’s creation.
