STARS Visual Vocabulary

LEARNING OBJECTIVES: SC.912.E.5.3: Describe and predict how the initial mass of a star determines its evolution

Thermal Nuclear Fusion The way to achieve nuclear fusion by using extremely high temperatures.

Spectra The field of optics to describe the rainbow of colors in visible light when separated using a prism

Hydrogen Basically, stars are big exploding balls of gas, mostly hydrogen and helium Our nearest star, the Sun, is so hot that the huge amount of hydrogen is undergoing a constant star-wide nuclear reaction, like in a hydrogen bomb

Gravity The force that attracts a body toward the center of the earth, or toward any other physical body having mass.

Star A massive ball of plasma (very hot gas) held together by gravity It radiates energy because of the nuclear reactions inside it.

Magnitude  Measure of the brightness of an object, measured in a specific wavelength or passband, usually in the visible or near-infrared spectrum.

Apparent Magnitude Absolute Magnitude How bright it is from Earth How bright a star appears at a standard distance

H-R Diagram The Hertzsprung-Russell diagram is a graph of many stars. It shows the relation between stars’ luminosity (that is, how bright they are) and their temperature (how hot they are).

Star Classification

Properties of Stars

Star Classification

Star Classification

Kinds of Stars

Life Cycle of a Star Stars are formed in clouds of gas and dust, known as nebulae. The exact lifetime of a star depends very much on its size. All stars over time, will expand, cool and change color to become red giants or super red giants. The path they follow beyond that depends on the mass of the star. Small stars, like the Sun, will undergo a relatively peaceful and beautiful death that sees them pass through a planetary nebula phase to become a white dwarf. Massive stars, on the other hand, will experience a most energetic and violent end, which will see their remains scattered about the cosmos in a enormous explosion, called a supernova. Once the dust clears, the only thing remaining will be a rapidly spinning neutron stars, or possibly even a black hole.

Nebula A large cloud of gas and dust in interstellar space A region in space where stars are born

Pulsars A celestial object, thought to be a rapidly rotating neutron star, that emits regular pulses of radio waves and other electromagnetic radiation at rates of up to one thousand pulses per second.

Black Hole A black hole is a region of space time exhibiting such strong gravitational effects that nothing including particles and electromagnetic radiation such as light can escape from inside it It is the result of the curving of space/time caused by a very dense mass. Around a black hole there is a position of no return, called the event horizon.

Super Nova Massive stars, fuse elements until no more fusion can occur, which results in a massive explosion called a supernova.

Gamma Ray Bursts Extremely energetic explosions that have been observed in distant galaxies. They are the brightest electromagnetic events known to occur in the universe.  Bursts can last from ten milliseconds to several hours.

Neutron Star Neutron stars are created when giant stars die in supernovas and their cores collapse, with the protons and electrons essentially melting into each other to form neutrons.

White Dwarf A star, approximately th e size of the earth It has undergone gravitational collapse and is in the fin al stage of evolution for low- mass stars, beginning hot and whit e and ending cold and d ark (black dwarf).

Sun The Sun gives life to the Earth and the Earth would have no life at all without the energy it receives from the Sun. The Sun is only one of millions and millions of stars in the Galaxy. Like all stars, the Sun is composed of a great burning ball of gases. It is made of 92.1% hydrogen and 7.8% helium (helium is from the ancient Greek word helios, which means Sun).

Blue Giant Stars Blue Supergiants are supergiant stars (class I) of spectral type O. They are extremely hot and bright, with surface temperatures of between 20,000 - 50,000 degrees Celsius. The best known example is Rigel, the brightest star in the constellation of Orion.

Red Dwarf Stars A red dwarf is a small and relatively cool star on the main sequence, of either K or M spectral type.  Red dwarfs range in mass from a low of 0.075 solar masses (M☉) to about 0.50 M☉ and have a surface temperature of less than 4,000 K

Yellow/White Stars Like the Sun, these medium-sized stars are yellow because they have a medium temperature. Their higher temperature causes them to burn their fuel faster. This means they will not live as long, only about 10 billion years or so.

Red Giants and Supergiant Stars After a star leaves the Main Sequence, its core contracts and heats up. Hydrogen burning ignites in a shell around the core, causing the envelope to expand, but as it does, it cools. The cooler but bigger star becomes redder but more luminous.

Brown Dwarfs Substellar objects that occupy the mass range between the heaviest gas giants and the lightest stars