Grade 9 Academic Science Space

Grade 9 Academic Science – Space Life Stages of a Star

A star has many descriptive possibilities:  A luminous globe of gas producing its own heat and light by nuclear reactions (nuclear fusion).  Stars consist mostly of hydrogen and helium gas.  Surface temperatures range from 2,000OC to above 100,000OC, and the corresponding colours from red to blue-white.  The brightest stars have masses 100 times that of the Sun and emit as much light as millions of Suns. The faintest and smallest mass stars have less than one-thousandth the brightness of the Sun and about 8% of the Sun’s mass (about mass Jupiter).  Most stars live for less than a million years.  At the end of its life, a star swells, loses it outer layers, and then, shrinks

Some of the life stages of a star, in somewhat chronological order…  Nebula  Protostar  Main Sequence Star  Red Giant  Red Dwarf  White Dwarf  Supernova  Neutron Star  Pulsar  Black Hole

Task  Read the description and assign the Star Life Stage from the list above

Star Life Description Stage These coloured Super Giants have luminosities often 1,000,000X greater than the Sun The explosive death of a star A cloud of hydrogen gas and dust in space. When the gravitational and pressure forces within the initial cloud become unbalanced, the cloud collapses and breaks into small fragments. The smallest of these fragments contract further to form these pre-stars This catastrophic event is thought to be main source of elements heavier than hydrogen and helium A mass similar to that of the Sun, but only 1% of the Sun's diameter (approximately the diameter of the Earth). These form from massive stars at the end of their life times Star type consists of degenerate matter with a very high density due to gravitational effects (i.e., one spoonful has a mass of several tonnes). Birthplace of stars An early stage in the process of star formation A star composed mainly of neutrons These stars are very bright because they are so large; yet, their surface temperature is lower than that of the Sun (…about 2000-3000OC) Four different types  Emission that glows brightly because the gas in it is energised by the stars that have already formed within its borders  Reflection where starlight reflects on the grains of dust  Dark that are dense clouds of molecular hydrogen which partially or completely absorb the light from stars behind them  Planetary are the outer layers of a star that are lost when the star changes from a red giant to a white dwarf Typically, these stars have a mass 3X greater than the Sun but a diameter of only 20 km. If its mass is any greater, its gravity will be so strong that the star will shrink further and implode to become a Black Hole. The gravitational pull is so great that nothing can escape from it, not even light Cool, small, faint and coloured star A very small, hot star Lasting about 100,000 years, it starts with a core of increased density within a molecular cloud and ends with the formation of a star leading to the development of a Main Sequence Star A large bright star with a cool surface Type of star that cools and fades There are two types:  Type I occurs in binary star systems in which gas from one star falls on to a white dwarf causing the dwarf to explode.  Type II occurs in stars ten times or more as massive as the Sun. Runaway internal nuclear reactions near the end of the star life leads to an explosion The shrunken remains of normal stars A large mass that forms by contraction out of the gas of a giant molecular cloud These large stars have diameters between 10X and 100X that of the Sun. If the star is a Super Giant, their diameters can be up to 1000X of the Sun. A late-life stage sub-species star that emits a beam of electromagnetic radiation that can be only seen when the beam of emission is pointing toward the Earth. This makes the star seems to “beat” They distort the space around them and can suck neighbouring matter into them, including nearby stars. The surface temperature is about 8000OC; yet being smaller than the Sun, the overall luminosity's is less than 1% of the Sun. Clouds initially balanced between gravitational forces (…which work to collapse the cloud) and pressure forces (…primarily from the gas which work to keep the cloud from collapsing) The Sun A teaspoonful of their matter from this star would weigh as much on Earth as an elephant…about 5.5 metric tons. This star type is produced when a Supernova explodes and forces the protons and electrons to combine The outcomes of the explosive event is either a Neutron Star or a Black Hole Its density cannot be measured Stars exist in hydrostatic equilibrium (i.e., outward forces of energy production equal impact of inward gravitational pull) Just prior to this “life-ending” event, the star obtains a brightness of 100 million suns It forms from a Main Sequence Star that runs out of hydrogen fuel in its core, starts to collapse, burns hotter to create greater outward pressures and quickly expands outward. About 1/10 the mass and diameter of the Sun A sub-species of star that is very dense and spinning rapidly These star use hydrogen as their fuel source for nuclear fusion reactions These small colourful stars burn so slowly that their estimated lifetimes are 100 billion years Crushed by high density of gravity, the core temperature of this small star exceeds 100,000OC Almost 90% of all stars in the Universe

There are other life stages of a star including (1) Black Dwarf and (2) Brown Dwarf. A Black Dwarf forms from a cooling White Dwarf; whereas, a Brown Dwarf is considered a sub-species of star. Can you define these two star types based on information in the tables? ANSWERS

Star Life Description Stage Red Giant These coloured Super Giants have luminosities often 1,000,000X greater than the Sun Supernova The explosive death of a star Nebula A cloud of hydrogen gas and dust in space. Protostar When the gravitational and pressure forces within the initial cloud become unbalanced, the cloud collapses and breaks into small fragments. The smallest of these fragments contract further to form these pre-stars Supernova This catastrophic event is thought to be main source of elements heavier than hydrogen and helium White Dwarf A mass similar to that of the Sun, but only 1% of the Sun's diameter (approximately the diameter of the Earth). Black Holes These form from massive stars at the end of their life times White Dwarf Star type consists of degenerate matter with a very high density due to gravitational effects (i.e., one spoonful has a mass of several tonnes). Nebula Birthplace of stars Protostar An early stage in the process of star formation Neutron Star A star composed mainly of neutrons Red Giant These stars are very bright because they are so large; yet, their surface temperature is lower than that of the Sun (…about 2000-3000OC) Nebula Four different types  Emission that glows brightly because the gas in it is energised by the stars that have already formed within its borders  Reflection where starlight reflects on the grains of dust  Dark that are dense clouds of molecular hydrogen which partially or completely absorb the light from stars behind them  Planetary are the outer layers of a star that are lost when the star changes from a red giant to a white dwarf Neutron Star Typically, these stars have a mass 3X greater than the Sun but a diameter of only 20 km. If its mass is any greater, its gravity will be so strong that the star will shrink further and implode to become a Black Hole. Black Hole The gravitational pull is so great that nothing can escape from it, not even light Red Dwarf Cool, small, faint and coloured star White Dwarf A very small, hot star Protostar Lasting about 100,000 years, it starts with a core of increased density within a molecular cloud and ends with the formation of a star leading to the development of a Main Sequence Star Red Giant A large bright star with a cool surface White Dwarf Type of star that cools and fades Supernova There are two types:  Type I occurs in binary star systems in which gas from one star falls on to a white dwarf causing the dwarf to explode.  Type II occurs in stars ten times or more as massive as the Sun. Runaway internal nuclear reactions near the end of the star life leads to an explosion White Dwarf The shrunken remains of normal stars Protostar A large mass that forms by contraction out of the gas of a giant molecular cloud Red Giant These large stars have diameters between 10X and 100X that of the Sun. If the star is a Super Giant, their diameters can be up to 1000X of the Sun. Pulsar A late-life stage sub-species star that emits a beam of electromagnetic radiation that can be only seen when the beam of emission is pointing toward the Earth. This makes the star seems to “beat” Black Hole They distort the space around them and can suck neighbouring matter into them, including nearby stars. White Dwarf The surface temperature is about 8000OC; yet being smaller than the Sun, the overall luminosity's is less than 1% of the Sun. Nebula Clouds initially balanced between gravitational forces (…which work to collapse the cloud) and pressure forces (…primarily from the gas which work to keep the cloud from collapsing) Main The Sun Sequence White Dwarf A teaspoonful of their matter from this star would weigh as much on Earth as an elephant…about 5.5 metric tons. Neutron Star This star type is produced when a Supernova explodes and forces the protons and electrons to combine Supernova The outcomes of the explosive event is either a Neutron Star or a Black Hole Black Hole Its density cannot be measured Main Stars exist in hydrostatic equilibrium (i.e., outward forces of energy Sequence production equal impact of inward gravitational pull) Supernova Just prior to this “life-ending” event, the star obtains a brightness of 100 million suns Red Giant It forms from a Main Sequence Star that runs out of hydrogen fuel in its core, starts to collapse, burns hotter to create greater outward pressures and quickly expands outward. Red Dwarf About 1/10 the mass and diameter of the Sun Pulsar A sub-species of star that is very dense and spinning rapidly Main These star use hydrogen as their fuel source for nuclear fusion reactions Sequence Red Dwarf These small colourful stars burn so slowly that their estimated lifetimes are 100 billion years White Dwarf Crushed by high density of gravity, the core temperature of this small star exceeds 100,000OC Main Almost 90% of all stars in the Universe Sequence

There are other life stages of a star including (1) Black Dwarf and (2) Brown Dwarf. A Black Dwarf forms from a cooling White Dwarf; whereas, a Brown Dwarf is considered a sub-species of star. Can you define these two star types based on information in the tables?  Black Dwarf – Star that emits no energy  Brown Dwarf – Star that emits very little energy, small mass so hydrogen fusion does not occur (may fuse lithium or deuterium), differ from large planet only in formation and composition