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- Radiation consisting of electromagnetic waves that travel at the speed of light.
- Below is a section of the electromagnetic spectrum, some common names for certain types, and their wavelengths.
- A telescope that uses a lens to collect the light from an object.
- A telescope that uses a mirror to collect the light from an object.
- An artificial object that orbits Earth, the Moon, or another celestial body; also a celestial body that orbits another of larger size (for example, the Moon is Earth's natural satellite).
- Artificial satellites orbit Earth at different altitudes and have many purposes such as GPS, international television, telephone, and Internet. They can also help scientists forecast the weather, study climate change, algae blooms, etc.
- They are a type of satellite with many sensors such as cameras that are sent to other planets to study them. They generally have short mission durations such as 2 to 3 years but some have lasted as long as 10.
- An example is the MESSENGER orbiter that NASA launched to 2004 to explore Mercury.
Solar nebula theory
- The theory that describes how the stars and planets form from contracting, spinning disks of gas and dust.
- At first there is a large cloud of gas and particles (a neblula) and then gravity starts to contract the gas together and creates a spinning motion around the centre. As the gas gathers in the centre it begins to heat up and condense becoming a protostar. During this time the gas and particles that don't get sucked up by the protostar clump together to form planetesimals, and if they last long enough and survive enough collisions, planets.
- A celestial body made of hot gases (plasma), mainly hydrogen and some helium, that is undergoing nuclear fusion.
- Stars have enormous size, temperature, and colour ranges.
A vast cloud of gas and dust, which may be the birthplace of stars and planets.
- Hot, condensed object at the centre of a nebula.
- Eventually nuclear fusion will commence and it will become a full-fledged star.
The process of energy production in which hydrogen nuclei combine to form helium nuclei.
- The surface layer of the Sun.
- The average temperature of the photosphere is 6000oC.
- An area of strong magnetic fields on the photosphere.
- They appear darker on the Sun since they are cooler than the photosphere (4500oC instead of 6000oC). They occur in 22-year cycles with peak activity occuring approximately every 11 years.
- A stream of fast-moving charged particles ejected by the Sun into the solar system.
- When the solar wind interacts with Earth's atmosphere the beautiful aurouras are created near the poles, however too much solar wind can interfere with satellites, or knock out telecommunications.
An event where complex groups of sunspots cause magnetic fields to explosively eject intense streams of charges particles into space (Solar wind).
Importance of the Sun
The Sun is necessary for all life on Earth. It allows plants to perform photosynthesis which is the base for almost every food chain on Earth, its energy drives the weather systems such as wind and ocean currents, and it keeps Earth warm by providing constant energy that Earth can absorb to keep a livable temperature.
A star's total energy output per second; its power in joules per second (J/s).
- The magnitude of a star that we would observe if that star were placed 32.6 light-years from Earth.
- Negative numbers are bright and as you get into the positive numbers the stars become dimmer. Our Sun is about +4.7 in absolute magnitude.
An optical instrument that produces a spectrum from a narrow beam of light, and usually projects the spectrum onto a photographic plate or digital detector.
- Certain specific wavelengths within a spectrum characterized by lines; spectral lines identify specific chemical elements.
- This is useful because by examining the spectral lines emitted by a star scientists can determine the composition of the photosphere of that star.
Hertzsprung-Russell (H-R) diagram
- A graph that compares the properties of stars.
A narrow band of stars on the H-R diagram that runs diagonally from the upper left (bright, hot stars) to the lower right (dim, cool stars) of the H-R diagram; about 90% of stars, including the Sun, are in the main sequence.
- A small, dim, hot star.
- They are lefftover matter from after the point when a star can no longer sustain fusion. While these stars do not produce energy of their own they take tens of billions of years to cool down.
- A massive explosion in which the entire outer portion of a star is blown off.
- In the cores of high-mass stars much higher temperatures are achieved and heavier elements form. Eventually iron forms in the core and since it doesn't release energy through fusion the core collapses violently and the shock wave travels through the star, the outer portion of the star explodes and a supernova occurs.
- This is very important because all the heavier elements in the Universe are from supernovas, even the rock and metal that makes up Earth.
- A star so dense that only neutrons can exist in the core.
- When stars begin with 12 to 15 solar masses the core will shrink to 20km in diameter after their supernova, under that pressure electrons are squeezed into protons and the star eventually becomes a neutron star. Some types spin very quickly and emit pulses of radiation into space so they are also called pulsars.
How low-mass stars evolve
They have less mass then the Sun and consume their hydrogen slowly over periods as long as 100 billion years. Over this time they lose significant mass and eventually turn into a white dwarf.
How intermediate-mass stars evolve
Intermediate-mass stars consume their fuel faster than low-mass stars over a time period of around 10 billion years (the Sun is an intermediate mass star). When their hydrogen gets used up their core collapses. As the core contracts, the temperature increases and the outer layers expand and cool. At this stage the star is now a red giant. As time progresses the outer layers will evaporate off until a white dwarf is left.
How high-mass stars evolve
- High-mass stars (12 or more solar masses) consume their fuel much quicker and so they die quicker and a lot more violently then intermediate-mass stars in a supernova.
- If they had 12-15 solar masses to begin they will from a neutron star after their supernova.
- If they have more then 25 solar masses then a black hole forms after their supernova.
When stars have more then 25 solar masses the remnants of the supernova are so massive that they get crushed into a space with no volume but a huge amount of mass. The gravity is so strong that not even light can escape from a black hole.