(Chapter 6.1) Describing the Universe Flashcards
(40 cards)
Define star
A giant luminous ball of plasma, mainly consisting of hydrogen and helium, held together by its own gravity
Recall what feature of plasma makes it the fourth fundamental state of matter
A significant portion of plasma consists of charged particles – ions and/or electrons. The presence of these charged particles is what primarily sets plasma apart from the other fundamental states of matter
Define nuclear fusion
A reaction in which at least 2 atomic nuclei are combined to form one or more different atomic nuclei and subatomic particles
Identify where nuclear fusion takes place in a star
Nuclear fusion takes place in the core of the star
Explain why stars emit light
Nuclear fusion converts mass into energy and electromagnetic radiation, such as visible light
Define apparent magnitude
Apparent magnitude (m) is a measure of the brightness of a star or other astronomical object observed from Earth
Identify the factors that impact the apparent magnitude
An object’s apparent magnitude depends on its intrinsic luminosity (energy output/distance), its distance from Earth, and any extinction of the object’s light caused by interstellar dust along the line of sight to the observer
Define absolute magnitude
The apparent magnitude an object would have if it were located at a distance of 10 parsecs
Recall the lifecycle of a star
- Birth from clouds of gas and dust
- Steady state - The star fuses hydrogen into helium to survive
- Old age - The star runs out of hydrogen fuel, expands and cools
- Death - The star implodes and the particles is blown away
Identify what property changes the colour of a star
The temperature of a star affects its colour
Identify the colour of a star in descending order of temperature
Blue, white, yellow, and red
Identify what property changes the brightness of a star
The size
True or False: “The size of a star is inversely proportional to the brightness”
False. The size of a star is proportional to the brightness
Define galaxy
A gravitationally bound system of stars, stellar remnants, interstellar gas, dust, and dark matter
Define solar system
The gravitationally bound system of a central star (the Sun) and the objects that orbit it
Define nebula
A cloud of gas, predominately hydrogen, and dust in space and is the ‘birthplace’ of stars
Define planet
According to the IAU (International Astronomical Union), a planet is a celestial body that:
* is in orbit around the Sun;
* has sufficient mass for its self-gravity to overcome rigid body forces so it assumes hydrostatic equilibrium (a nearly round shape), and;
* Has “cleared the neighbourhood” around its orbit
Define planetary nebula
A type of emission nebula consisting of an expanding and glowing shell of ionised gas ejected from red giant stars late in their lives
True or False: “Planetary nebulae are related to planets”
False. Planetary are misnamed as when they were discovered, they were misclassified as planets
Identify another term for planetary nebula
Stellar nebula is another term for planetary nebula
Define asteroid
A small rock body that orbits the Sun
Define comet
A celestial object consisting of a nucleus of ice and dust and when it approaches the Sun, a ‘tail’ of gas and dust particles appears
Define meteoroid
A small rocky or metallic body that orbits the Sun
Define meteor
A small rocky or metallic body of matter from outer space that enters the Earth’s atmosphere, becoming incandescent as a result of friction and appearing as a streak of light
