Star
* All stars appear to be white in color
  - are blue-white in color
* All stars are in gaseous form - balls of helium and hydrogen plus other elements
  - orbit around something, with orbits defined by gravitational accelleration
  - like the sun, but very far away - so making their own light
  - much hotter at their centers, however
  - so far away that they only appear as dots even in the most powerful telescopes
  - suns
* All stars are the same distance away, but some are naturally bright while others are just dim
  - form the Earth
  - from the Earth
  - become red giants when they run out of hydrogen in the core
* All stars begin as being made up almost entirely of hydrogen
  - their lives by fusing hydrogen into helium in their cores
  - can generate energy from gravitational collapse
  - collapse to become black holes upon their death
  - convert some hydrogen to helium
* All stars emit a continuous spectrum of all wavelengths through the electromagnetic spectrum
  - eventually burn out and die when their source of fuel runs out
  - evolve the same way up to the red giant phase
  - form out of dense collapsing condensations in large dust clouds
* All stars have a finite life, and one can therefore say they are all dying
  - magnetic field
  - different temperatures
  - mass loss
  - mass, therefore all are massive
  - variable brightness at some level
* All stars lose mass
  - material from their surfaces in a steady wind
  - radiate energy, particularly in the forms of heat and light
  - start by burning hydrogen and end up creating many heavier elements inside their cores
* Every star generates a stellar wind of particles that causes a continual outflow of gas into space.
* Every star has a core
  - life cycle, and the sun is no exception
  - is attracted to every other by a force which lessens with distance
  - starts out as a cloud of gas and dust, part of a larger cloud called a nebula
* Many stars appear to be of similar magnitude
  - are actually arrangements of two or more stars that orbit each other
* Many stars are binary stars or multiple stars, with several stars orbiting around one another
  - stars, or double stars
  - brighter than first magnitude
* Many stars are in binary star systems - which means that two stars orbit each other
  - multiple systems of two or more stars
  - lighter than it is and many others are much more massive
  - members of clusters of hundreds or thousands of stars
  - microwave emitters
  - much bigger and hotter, and many stars are smaller and cooler
* Many stars are part of a system with two or more stars
  - binaries or multiple systems
  - visible and the horizon is barely visible
  - can form from a single nebulous cloud
  - come in pairs
  - congregate in clusters, some of which are visible to the naked eye
* Many stars form in clusters
  - together in clusters, so they all have the same age
* Many stars have carbon-rich dust
  - noticeable colors
  - lose a substantial part of their mass as they age
  - occur in pairs, multiple systems, and star cluster s
  - puff off their gas in a spherical shell
  - ring with sound waves
  - shoot out powerful jets of gas
  - show a periodic change in their apparent magnitude
* Many stars vary in brightness over periods ranging from less than a day to several years
  - the amount of light they radiate
* Most stars appear only as points of light
  - same brightness
* Most stars appear to be normal, mature stars that are using their nuclear fuel at a steady rate
  - white and twinkling
  - move very little against the background sky
* Most stars are dwarfs
  - either multiple or have circumstellar disks, or both
  - grouped into a small number of spectral types
  - hot and bright and appear white or blue
* Most stars are in multiple systems
  - such systems, usually binaries
  - systems of two or more stars orbiting around one another
  - main sequence stars
* Most stars are members of a binary or multpile star system
  - binary or multiple systems
  - multiple-star systems
  - part of binary or other multiple star systems
  - so far away that they never appear to move when viewed from the Earth
  - too faint to see without a telescope
  - very similar to our sun
  - begin their lives burning hydrogen to helium
  - belong to the main sequence , which consists of ordinary hydrogen-burning stars
  - change their positions as Earth rotates and revolves
  - destroy lithium during an early hydrogen-burning phase of their evolution
  - die at the end of the main sequence phase
* Most stars emit X-rays which satellites can detect
  - unpolarized light, containing equal amounts of the two polarizations
  - exhibit absorption line spectra, but a few rare stars show emission lines
* Most stars have binary companions
  - essentially the same chemical composition., yet show different absorption spectra
  - four rays
  - less mass than our sun
  - similar life cycles
  - very similar chemical compositions
* Most stars live in multiple star systems where two or more stars are orbiting each other
  - the main part of their lives as main sequence dwarfs
  - look like shiny dots from Earth , because they are far away
  - occur in binary systems
  - seem to shine with a constant light
  - send out radio waves, but some send out more
  - use up the hydrogen at their core
* Some stars actually change in magnitude and are aptly called variable stars
  - appear to form definite patterns which are called constellations
* Some stars are bigger than our sun
  - bigger, more massive, and brighter
  - billions of light years away
  - closer to the earth, while others are extremely distant
  - dark and others are light
  - halo stars
  - hotter than others
  - intrinsically variable
* Some stars are much smaller than the sun, others are millions of times bigger
  - younger than the sun
  - periodic with periods ranging from several hours to several decades
  - small and dim while others are super-giants by comparison
  - smaller than our sun
  - so bright they have negative magnitudes
  - three times larger than the sun and are called massive stars
  - too close to be split visually
  - very bright, many are dim
  - visible every night of the year, all night long
  - blow off their outer layers to produce planetary nebulas
  - continue to form so the disk has some young metal-rich stars
* Some stars even come in triplets or quadruplets
  - orbit around each other
  - exhibit a regular variation in the degree of red shift in their spectra
  - exist in pairs called binaries
  - explode in slow motion
  - form in giant spherical masses of stars
  - have a companion star nearby, kind of like a twin
  - just appear next to each other because they lie along the same line of sight
  - keep shrinking until they become a cooling ember made up of iron
  - lie in a tenuous spherical halo which surrounds the disk
  - look single to the naked eye but really are two stars orbiting each other
  - oscillate in brightness
  - seem brighter than others
* Some stars show obvious color and brightness differences
  - two simultaneous cycle periods
  - stay above the horizon and never set
  - swallow their own planets, according to a team of Spanish and Swiss researchers
* Some stars vary in brightness and are called variable stars
  - because they pulsate in and out
* also appear in clusters
  - change as they age
  - conserve angular momentum
  - have magnetic fields, probably caused by rotations of hot ionized gases in the star
  - mean the stars of Hollywood
* always appear as pinpoints of light.
* appear as pinpoints of light, and the atmosphere distorts the light so that they twinkle
  - brighter according to their visual magnitude
  - dimmer and hence appear further away than they really are
  - in the sky
* appear like comets having tails on one side
  - small lights in the night sky, but they are really huge balls of burning gas
  - much fainter because they are much further away
  - only as pinpoints of light in the sky, even through the most powerful telescopes
  - red shifted when receding away from the earth and blue shifted as they approach
* appear to be stationary on the sky because of their exceedingly large distances
  - have different colors
  - move in the night sky rising in the east and setting in the west
  - twinkle as starlight passes through shifting air pockets that act as roving lenses
  - when the mouse is passed over an object that animates
* are a good example of how the temperature of plasmas can be very different
  - light source
  - source of a gravity field
  - actors
  - also approximate black body radiators
  - always fit, have great teeth, skin and hair, and are usually white
  - another good example of how the temperature of plasmas can be very different
  - arranged in various classes by their spectral characteristics
  - as grains of sand swirling around in the ocean-universe
* are balls of gas with a nuclear furnace at the center
  - hydrogen gas that are so massive the centers burst into nuclear reactions
  - basically huge balls of hydrogen gas
  - big balls of gases at really high temperatures
* are born in nebulae
  - some nebulae, and create new ones as they die
  - within the clouds of dust and scattered throughout most galaxies
* are born, live, and die
  - they live, and they die
  - bright in the optical band
  - bright, thermonuclear furnaces producing massive amounts of heat and light
  - brighter when they are larger because there greater area of star emitting light
  - capable of supernovas
* are celestial bodies
  - objects consisting mostly of hydrogen and helium
* are classified as supergiants on the basis of their spectral luminosity class
  - into five main luminosity classes
  - composed of mainly hydrogen and helium, with trace amounts of other elements
  - different sizes
  - difficult but possible to see during a total eclipse
  - divided into seven spectral classes according to their color
  - elements in galactic circuits
  - enormous gaseous masses held together by gravity
  - enormously massive hydrogen bombs
  - essentially superheated balls of plasma
  - extraordinarily distant from one another
  - fairly uniform in brightness, with the red star the brightest
  - formed in clouds of gas and dust called nebulae
  - fueled by the nuclear fusion of hydrogen to form helium deep in their interiors
* are giant balls of gas in space that shines through the darkness
  - fire balls of gas
  - spheres of gas, mainly hydrogen and helium
  - giant, luminous spheres of plasma
  - gigantic balls of gas, mostly hydrogen gas
  - grouped into spectral classes based on a range of temperatures they fall into
  - heavenly bodies
* are hot and bright because they are huge nuclear reactors
  - bodies of glowing gas that start their life in Nebulae
  - hot, dense objects which emit a continuous spectrum of light from their surface
* are huge balls of burning gas
  - gas generating tremendous amounts of energy
  - hot gas
  - hot, glowing gases
  - luminous balls of gas powered by nuclear reactions at their centers
  - indisputably important, particularly in a young bird s learning and development
  - less visible at night
  - like the filament in the light bulb
* are located in constellations
  - eyes
  - galaxy
  - globular clusters
  - night skies
  - outer space
  - press conferences
  - solar systems
  - universes
* are made in nebulas
  - many light years apart
  - many, but the sky is one
  - massive bodies in space that are self-luminous
  - massive, glowing balls of hot gases, mostly hydrogen and helium
  - millions and millions of kilometers away
  - more complex than an equal amount of gas dispersed to 'infinity'
  - most numerous in the nucleus and their numbers decline outward through the disk
* are much bigger than our planet
  - denser than the interstellar medium
  - hotter and denser in their cores than on the outside
  - nearly opaque
  - objects that shine because they give off energy by process of nuclear fusion
  - of finite size
  - often form in groups called star clusters
* are on an outermost celestial sphere
  - fire and can burn out
  - only a mile across and burn out within a year of their formation
* are part of constellations
  - plasmas as well
* are point sources of light, with no visible signs of offending color, coma, or astigmatism
  - sources, even for the closest stars
* are points of light because they are so small
  - reflect so little light
  - polygons
  - predominantly hydrogen, with helium as the other major constituent
  - really huge, hot, spheres of hydrogen and helium gas which are producing their own energy
  - responsible for cosmic cooking today
  - shapes
  - simple things, giant spheres of mainly hydrogen gas
  - smaller than sun or moon
* are so distant that they appear as points of light even through powerful telescopes
  - far away that it is impossible to measure their distances only in kilometers
* are so far away that they have angular diameters of zero, i.e. they are point objects
  - look like points of light
  - look like unresolved points of light even in large telescopes
  - some of the most imteresting phenomenon in our universe
  - sources of radiation, giving off their own energy
* are spherical balls of hot gas
  - because of a. the high temperature in the interior
  - still points of white light
  - suns and, do produce their own energy, some in light waves
* are the basic units of population in the universe
  - life force of a galaxy
  - most plentiful objects in the visible universe
  - objects that heat and light the planets in a system
  - primary light source in the universe
  - principle source of energy for the interstellar medium
  - used for guidance
  - very different objects than are planets
* are very far apart, compared to their size
  - away, much farther away than any object in the solar system
  - luminous yet thoroughly opaque
* are visible in every single image
  - much closer to the horizon
  - through the expanding coma
* are, after all, giant hydrogen bombs, efficient thermonuclear furnaces
  - to a good approximation, blackbody radiators
* arise in gas clouds.
* assemble to write messages in the sky.
* become white dwarfs at the ends of their active careers, when their fuel is used up.
* begin inside a nebula which dark cloud of gas and dust
  - life as clouds of dust and gas called nebulae
  - their lives as clouds of dust and hydrogen
  - to form in the coldest depths of space within huge clouds of interstellar gas and dust
* blaze in intensity, and colors are often glimpsed in the brighter nebulae.
* burn by evolving higher elements through nuclear fusion
  - deuterium and hydrogen, brown dwarfs only deuterium, planets nothing
  - fuel through thermonuclear fusion
  - gas and they continue through life orbiting around the center of their galaxy
  - hydrogen in a process known as fusion
* can actually go through several red giant phases.
* can be big or small, hot or cool, young or old
  - billions of years old
  - highly colored
  - pendants or earrings or sewn together as a string of stars
  - variable for many reasons
  - very active, but also unpredictable
  - burn out very quickly
  - change very much between when they are first created and when they run out of energy
  - come by their names in strange ways
  - extract energy from the fusion of elements up to iron
  - gain mass if they are members of an accreting binary system
  - have temperatures of thousands of degrees or higher
  - live for billions of years
  - loose mass in a variety of ways
  - meet their ends in a few different ways all of which depend on one thing, their mass
* can pulsate in brightness, temperature and other ways
  - temperature, size and other ways
  - range from a few million to a several billion years old
  - symbolize either faithful or unfaithful teachers
  - thus be smaller than some gas giant planets, including Jupiter
  - turn into meteors
  - twinkle randomly
* change considerably with time.
* change in brightness either when they are very young , or when they are very old or dying
  - when they are very young, or when they are very old or dying
  - color, luminosity, size and temperature through their lifespan
  - over time
* come in a bewildering array of sizes, colors, and temperatures.
* come in a variety of colours, mass, volumes, contents and nature
  - sizes and colors, but they all shine because they are hot
  - wide range of sizes and temperatures
  - all different colors
* come in all sizes, brightnesses, temperatures and colors
  - temperatures, and ages
  - colors from red, orange, yellow, white, and bluish-white
  - great variety of sizes and brightness, or luminosity
  - many different colors based on their temperatures
  - several fixed 'spectral types' which are quite different from one another
* condense out of tenuous clouds of gas.
* consist mainly of hydrogen and helium, with varying amounts of heavier elements
* contain a finite amount of fuel.
* convert some of their mass to light.
* create their own light from thermonuclear energy in their cores.
* die in different ways, and they leave different things around
  - when they run out of hydrogen or other nuclear fuel to burn and iron is produced
* differ in colour.
* differ in size, brightness and color
  - color and magnitude
* differ widely in colour, ranging from blue-white to red
  - mass , size, temperature , and total energy output, or luminosity
  - mass, size, temperature, age, and luminosity
* do have their own real motion, called proper motion.
* eat each other, planets collide, gases ignite.
* eject their material into space in a variety of ways.
* emit blackbody radiation
  - light over a wide range of wavelengths
* evolve - and so do galaxies
  - and eventually die
  - because their chemical composition changes
* evolve, and astronomers have a pretty good handle on just how fast stars age
  - explode or die and now stars form from the residue
  - or change, over time
* exhibiting such behaviour are called rotating variables.
* exist only in galaxies.
* expand as they grow old.
* explode and the dust forms a nebula
  - in supernovae
* float on the horizon, threatening to sink forever into the sea's depths.
* focus to sharp points of light.
* form as a result of gravitational instability of large gas clouds.
* form by gases and dust clumping together
  - the gravitational collapse of interstellar gas
  - deep inside vast clouds of interstellar gas and dust called nebulae
  - directly from the collapse of dense clouds of interstellar gas and dust
  - due to the contraction of a nebula of gas and dust under the influence of gravity
* form from cloud, cycle repeats, galaxy gets more enriched
  - clouds of gas and collapse under self-gravity
* form from collapsing clouds of gas and dust
  - concentrations in huge interstellar gas clouds
  - giant clouds of gas and dust, lots of material so can form lots of stars at once
* form from gravitational collapse of vast clouds of gas and dust in interstellar space
  - pull of matter
  - huge clouds of dust and gas
  - massive clouds of hydrogen gas
* form from the gravitational collapse of large clouds of interstellar material
  - molecular clouds in interstellar space
  - contraction of dense clumps of cold, molecular gas
  - half the detectable mass of the Milky Way
* form in clouds of dust
  - gas and dust that collect into a swirling disk
  - clumps of cool molecular gas that hide the nascent stars
* form in clusters from expansive clouds of gas and dust
  - when clouds of gas and dust come together
  - cocoons of gas and dust
  - interstellar clouds, which are cold and dense
* form in the center of a disk of dust and gas
  - inner, denser parts before they form in the outer, less dense parts
* form out of clouds of gas and dust
* form out of the densest clouds which astronomers call molecular clouds
  - gravitational collapse of large clouds of interstellar gas and dust
* form when a giant cloud of cold hydrogen gas collapses in on itself
  - cool interstellar gas clouds collapse under their own gravity
  - hot dust and gas spiral in to a central point, eventually clumping together
  - hydrogen atoms in space are pulled together in bigger and bigger spheres
  - with disks of dust and gas which can condense into planets
  - within a vast collection of other stars and clusters of stars known as a galaxy
* frequently form in groups.
* gather in galaxies.
* generally form through a fragmented collapse of a molecular cloud as a group or cluster
  - move in free orbit
  - produce Helium, and other heavier elements, and eventually can produce iron
* generate their own energy during their lives by the process of nuclear fusion.
* get the energy they produce through nuclear fusion of hydrogen into helium
  - their heat from two sources - gravity, and nuclear fusion
* give light to cheer the heart.
* glisten in crystalline profusion through the dry atmosphere of a mid-spring sky.
* go out with a bang, with explosions that glow in X rays.
* grow old and die, while new stars are being formed all throughout the universe.
* have a LOT of mass
  - certain position, distance and brightness
  - fixed declination so their visibility remains the same for a given location
  - limited lifetime, and finally they ends up as light travelling through the universe
* have a wide range of radii
  - surface temperature as measured by their color
  - accurate colors, twinkle, and dim near the horizon
  - bright emission lines in their spectra, but no absorption lines
  - complex magnetic fields
* have different colors because they have different surface temperatures
  - due to different temperatures
  - colours, depending on how hot they are
  - life cycles, just like people
  - real motion through space as well as apparent motion as Earth orbits the Sun
  - several ways of dying
  - their own names
  - to have enough mass to get hot enough inside to spark thermonuclear fusion reactions
* heavenly body
* includes sections.
* increase in luminosity as they age.
* indicate membrane-bound compartments one of which appears as a bleb from the plasmalemma
  - vesicles one of which appears as a bleb from the plasmalemma
  - the location of the magnetopause
* leave the main sequence when they stop burning hydrogen
  - sky during the daytime
* lie on a narrow sequence because luminosity and temperature climb steadily with mass.
* live and die over the course of millions to billions of years.
* live for billions of years and go through four basic stages
  - up in the sky
* look bright because emit light from the nuclear fusion happening in their cores
  - different colors because they are different temperatures
* lose mass during their lives.
* make energy by nuclear fusion
* manifest in cyclic patters.
* map only loss, where vacuum lenses out their light.
* move across the sky on a regular schedule, much like the sun
  - in space relative to the sun
  - parallel to the celestial equator
  - through the spiral arms
  - very slowly across the night sky
* never form by themselves.
* obtain energy by converting light elements, like hydrogen, into heavier ones.
* often form as binary pairs
  - groups, traveling together through space
* orbit the center of galaxies
  - the cluster, and the cluster orbits the center of our Galaxy
* originate as large bodies of slowly rotating gas.
* ought to form in groups, since large interstellar clouds are more unstable than small ones.
* pass each other within galaxies, although they also orbit around the galactic center.
* produce energy from nuclear reactions that lead to the formation of all the other elements
  - reactions, primarily the fusion of hydrogen to form helium
  - through a process known as fusion
  - great amounts of electromagnetic energy in the forms of light ant heat
  - light by nuclear fusion, which builds heavier elements out of lighter elements
  - massive amounts of heat energy and in so doing they also give off light
  - powerful jets and winds during their birth
* produce their energy through nuclear fusion
* provide much of the illumination NVGs see on moonless or low illumination nights.
* pulsate in many different modes simultaneously, each with a slightly different period.
* radiate away enormous amounts of energy in the form of electromagnetic radiation.
* range greatly in their size and distance from Earth
  - in density from very tenuous to very, very dense
* reflect light from planets.
* rely on their image.
* represent fossil records.
* require unimaginable, but quantifiable amounts of energy to shine as they do.
* rise four minutes earlier every day, as seen from a given observation point
  - straight up from the horizon
* seem to move less the further north or south they are located.
* seems to be on the inner surface of a sphere surrounding the Earth.
* shine and the light can be seen with a telescope , but they also give off radio waves
  - play host to extremely energetic nuclear fusion reactions in their cores
  - brighter when they dance
  - due to the chemical combustion of hydrogen
  - like our sun
  - with coldness out of distant depths of the universe
* show up as bright dots, while galaxies are more spread out.
* sometimes form in colorful ways.
* spend most of their life converting hydrogen to helium and producing heat and light
  - lifetime burning hydrogen into helium
  - the bulk of their existence as main sequence stars
* spin, and some spin very fast.
* stand out better in images produced by reflecting telescopes.
* start as huge regions of gas, mostly hydrogen
  - forming, but the most massive ones became supernovae within a few million years
  - out as dense cores in molecular clouds
  - to die when they stop burning hydrogen
* streak out when spacecraft are shown accelerating to light speed.
* symbolize mental-light and purpose.
* take millions of years to be visible on earth.
* tend to fall only into certain regions of the diagram
  - generate high amounts of income
* touch the ends of time.
* trace out circles around the celestial pole as the Earth rotates.
* trail around the Celestial South Pole.
* twinkle due to many changes in the density of air between the observer and source.
* use gravity to balance the kinetic pressure or expanding force of the plasma
  - hydrogen as a fuel with which to produce energy
* use up deuterium when they are born, evolve and finally die in supernova explosions
  - their fuel and thus undergo change
* usually change their brightness when they are young and when they are old and dying
  - occur in groups called clusters, which are gravitationally bound
* vary greatly in size and in color
* vary in brightness due to a number of factors, the most prevalent is their distance
  - throughout their lives based primarily on their mass
  - many different ways, often by changing the amount and colour of the light they emit
  - size and brightness
  - widely in size
* work by converting one gas into another - usually hydrogen into helium.
+ Binary star
  * A 'binary star' is two stars which orbit around each other. For each star, the other is its 'companion star'. Many stars are part of a system with two or more stars. The brighter star is called the 'primary star', and the other is the secondary.
+ Black hole, Formation of black holes, Explanation: Stars :: Astrophysics
  * Most black holes are made when a supergiant star dies, and leaves behind a mass that is at least one solar mass. Stars die when they run out of hydrogen or other nuclear fuel to burn and iron is produced. Iron does not give off energy and therefore the star has no fuel and in a short amount of time the star collapses.
+ Category:Stars: Astronomical objects
  * Stars can be billions of years old. The Sun is a star.
+ Main sequence: Astrophysics :: Types of stars
  * Stars are created from nebula and first appear on the main sequence. They stay on the main sequence for millions or billions of years. When a star begins to run out of fuel, it gets much bigger and colder and turns into a red giant. After this happens, the star is no longer on the main sequence.
+ Neutron star, Properties, Magnetic Field: Types of stars :: Astrophysics
  * All stars have a magnetic field. When a star collapses, it becomes smaller. This means that the magnetism is pushed into a smaller area, which means that the magnetic field is stronger nearer the star.
+ Orbital inclination: Celestial mechanics
  * Orbital inclination' is a term for the angle between two orbital planes. It is often used to describe the movement of celestial bodies such as stars and planets. In that context, one of the planes is the standard, or reference. Many stars are in a galaxy that has a galactic plane which is used as reference. For a planet's orbit, the inclination is the angle to the ecliptic plane. For a moon, an inclination of 0 degrees means the orbiting body orbits the planet in its equatorial plane, in the same direction as the planet rotates.
+ Radio telescope: Telescopes
  * A 'radio telescope' is like a huge satellite dish. An ordinary telescope allows people to see light from distant objects. Stars shine and the light can be seen with a telescope, but they also give off radio waves. Scientists with radio telescopes receive these radio waves and use computers to learn about the stars. Other things like black holes also give off radio waves and radio telescopes are useful for learning about them too.
+ Star, Birth and life and death of stars
  * Stars are made in nebulas. These are big areas that has more gas than normal space has. The gas in a nebula is attracted to all the other gas by gravity. This makes the gas in the nebula very thick. Stars form in these thick areas. The Orion Nebula is an example of a place where gas is coming together to form stars.
  * Most stars use up the hydrogen at their core. When they do, their core shrinks and becomes very, very hot. It becomes so hot it pushes away the outer layer of the star. As the outer layer expands it makes a red giant star. Astro-physicists think that in about 5 billion years, the sun will be a red giant. Our sun will be so large it will eat the Earth
  - Numbers, distances
  * Most stars are very old. They are usually thought to be between 1 and 10 billion years old. The oldest stars are thought to be around 13.7 billion years old. Scientists think that is close to the age of the Universe.
  * Stars vary greatly in size. The neutron star is incredibly dense. If you were to take a layer a micrometre thick and apply it onto a tank, it would be a very tough armor. The tank would be so heavy, it would sink into the center of the Earth.
  * Stars are a source of a gravity field. This is what keeps planets close to them. It is also not unusual for two stars to  orbit each other. This happens when they are close together. This is also because of gravity, in the same way as the Earth orbits the Sun. There are even groups of three or more stars orbiting each other
  * Most stars look like shiny dots from Earth, because they are far away. Our Sun is the closest star to us. The Sun and all things that orbit it are called the Solar System
+ Stellar evolution
  * Stellar evolution' is the study of how a star changes over time. Stars can change very much between when they are first created and when they run out of energy. Because stars can produce light and heat for millions or billions of years, scientists study stellar evolution by studying many different stars in different stages of their life.