In qualities 6 and 8 learners spanned material concerning the solar system consisting of the Sun. In grade 7, they concentrated on the mechanism which includes the Sun, Earth and Moon. Learners should be acquainted with the truth that the sun is a star and produces heat and light (energy) via nuclear reactions. In this chapter the emphasis is ~ above the life cycle of stars, including just how they are born and die. The exact development that a star complies with depends ~ above the initial mass of the star. The Sun"s advancement is presented as an example. The main intends of this chapter space to ensure the learners understand the following:

stars room born in vast clouds the gas and also dust

stars spend most of their lives on the main sequence fusing hydrogen gas come helium gas

stars ultimately swell up to kind a red giant star stars prefer the Sun end their resides as planetary nebulae and white dwarfs

Some learners may ask why stars look "spiky" in the photographs from telescopes, however in the diagrams presented here, they space presented as spheres. Clock this video to uncover out and explain to your learners:

Do friend think it is vital to teach astronomy to learners at school? read this interesting and informative write-up detailing the benefits and also applications the astronomy:

5.1 The birth of a star (0.5 hours)

5.2 Life of a star (1 hour)




Activity: Observing Orion in the feather sky


CAPS suggested

5.3 death of a star (1.5 hours)




Activity: Life cycle of a Sun-like star

observing, investigating


Activity: The life bike of the Sun

observing, writing


Activity: flow diagram poster reflecting the lifecycle the a Sun-like star

writing, drawing, sequencing

CAPS suggested

A good way to present the topic of stellar advancement is to begin by asking learners exactly how long castle think stars critical . Numerous will prize forever. Many human being are unaware that, prefer humans, stars are born, live their lives and also then die. Friend can likewise ask lock what is intended by "living" when referring to a star, after all, stars execute not execute the 7 life processes, as taught in Life and also Living. Astronomers generally consider stars that room undergoing nuclear reactions in your cores to be living stars.

You are watching: Which event marks the birth of a star

Stars are also compared in terms of loved one concepts, together as:

young and old cool and hot how big they room how massive they space (the fixed is vital in regards to looking at just how stars die)

Where space stars born? have the right to we talk around a star as "living"? exactly how long do stars like the sun live? how do stars spend most of their life? Why room stars different colours? just how do stars die?
Stars carry out not live forever, as with people. Stars are born, live your lives, transforming or evolving
as they age, and also eventually lock die. Frequently stars execute this in a much much more spectacular way than human beings do!

In this chapter, girlfriend will notification that numerous nouns are used as adjectives, because that example, sun is the noun and solar is the adjective. Other noun and also adjective bag include: moon and also lunar, star and stellar, planet and also planetary.

Scientists speak that stellar evolution once talking around the birth, life and also death that stars. The life time of individual stars is way too long for people to watch the development of a single star, so just how do scientists study mainly evolution? This is possible as there room so numerous stars in our galaxy, so we deserve to see lots of them at various stages of your lives. In this way, astronomers can develop up an overall photo of the procedure of stellar evolution. In this chapter you will find how stars space born, how they evolve, and also how castle die.

Lots the work entered figuring out the procedures in mainly evolution. This work-related is still on going. What you room learning below in natural Sciences is based upon years of research, and also current research study is constantly acquisition place, to update what we know.

In this ar learners will uncover that stars space born in giant clouds of dust and also gas, called nebulae, in space. In order come understand just how collapsing gas clouds warmth up come eventually form stars, learners require to recognize that compressing a gas heats that up and that allowing a gas to increase cools the down. If they are unfamiliar v this concept a great analogy is come think around over-inflating a bicycle tyre (without bursting it). You could demonstrate this in course by obtaining learners to contempt over-inflate a tyre. They will uncover that the pump and tyre get hot!

In the situation of inflating a tyre, you room forcing more and much more molecules right into a offered volume (assuming that the tyre is currently at full capacity). Therefore you are compressing or squeezing the gas. Each molecule has a specific amount that kinetic energy. As an ext molecules are compelled in by the pump, the wait in the tyre is compressed and also the complete thermal power increases because there are much more molecules colliding inside the tyre. As an ext particles are consisted of in the exact same volume, the air"s temperature in the tyre increases. Together you deflate the tyre, you enable the gas come expand, the molecules are an ext spread out. There is then less thermal energy and also so the temperature decreases. You can let students feel the air together it is exit from the tyre - it must be chillier than the ambient air together it is rapidly broadening as the escapes indigenous the tyre.

Stars room born in vast, gradually rotating, clouds the cold gas and dust dubbed nebulae (singular nebula). These large clouds space enormous, they have actually masses somewhere in between 100 thousand and also two million times the massive of the Sun and their diameters range from 50 come 300 irradiate years across.

A irradiate year is the distance that light travel in one year. Light travels extremely fast at 299 792 458 m/s. One light year is indistinguishable to 10 sunshine kilometers.

The "Pillars the creation". This giant, dense dusty clouds that hydrogen gas are vast stellar nurseries where brand-new stars room born. (NASA)

A famous instance of among these large clouds is the Orion nebula in the constellation the Orion. It is visible through the nude eye if the sky is dark enough. These clouds space so massive that they deserve to collapse under their own gravity if they room disturbed.

The collapse of a star deserve to be triggered once the cloud is squeezed. For instance if a cloud passes v a spiral eight in a galaxy it will be slowed down and also compressed. This defines why several stars are created in the spiral eight of galaxies.

The constellation the Orion as perceived from the southerly hemisphere. The Hunter Orion is "upside down" once viewed native the south and his sword lies over the 3 stars in his belt. The jewel in his sword which looks choose a white-pink smudge is the Orion nebula.
This diagram shows just how the stars comprise the constellation the Orion, as viewed in the southern hemisphere.

Over time the clouds contract, become denser and slowly warmth up. The clouds additionally break up right into smaller clumps. As the clumps get smaller they begin to flatten out into a disc shape. The center of every clump will ultimately contain a star and the external disk that gas and also dust may eventually type planets about the star.

Hubble space Telescope photo of the Orion Nebula showing different protostars surrounding by a dark decaying of gas and also dust. These disks (called protoplanetary disks) may eventually kind planets approximately the star.

As the contracting clump proceeds to heat up, a protostar is developed at the centre. A protostar is a dense ball of gas the is no yet hot enough at the center to start nuclear reactions. This stage lasts for roughly 50 million years. Together the fallen continues, the fixed of the protostar increases, squeezing that further and increasing the temperature. If the protostar is massive enough for the temperature to with 10 million levels Celsius, then it becomes hot enough for atom reactions to start and the protostar will will technically be described as a star.

Not also known as its star formation cousin Orion, the Corona Australis region, v the Coronet cluster at the centre, is one one of the nearest and also most energetic star formation regions to us. This picture shows the young stars in ~ the centre, with gas and also dust emissions.

The Coronet cluster, presented in the image, has a hold of young stars at various life stages, which permits astronomers to gather data and pinpoint details of how the youngest stars evolve.

Do you remember that us learned about nuclear reactions critical term in power and change when looking at nuclear strength plants?

The young star starts converting hydrogen come helium via nuclear fusion reactions. Atom reactions in stars produce huge amounts of power in the kind of heat and also light, i m sorry is radiated right into space. This power production avoids the star from contracting further. As the star shines, the decaying of dust and gas surrounding the star is gradually blown far by the star"s stellar wind which leaves behind any planets if lock have currently formed.

A big bubble of warm gas increasing from glowing matter in a galaxy 50 million irradiate years from Earth. Astronomers suspect the bubble is gift blown by mainly winds, released throughout a explode of star formation.

Just favor the sunlight loses corpuscle into an are in the type of the solar wind, various other stars additionally have winds called stellar winds.

Star formation in the nearest galaxy external the Milky Way, referred to as the huge Magellanic Cloud (LMC), taken with the Hubble space Telescope. This picture shows glow gas, dark dust clouds and also young, hot stars.

In the top left the the picture of large Magellanic Cloud, you deserve to see a collection of blue and white young stars. Lock are exceptionally hot and are few of the most huge stars known everywhere in the Universe.

The image presented here of the large Magellanic Cloud, a satellite galaxy come the Milky Way, illustrates very clearly, an instance of sequential star formation, where new star birth is prompted by the previous generation of substantial stars. You can allude some of these observations out to learners:

Just listed below the swarm of warm stars in the top left, is an area that brightly create hydrogen gas, illuminated by the nearby hot stars. Additional to the ideal are number of smaller dark dust clouds through odd shapes. They have the right to be watched silhouetted against the glowing gas. Number of of these dark clouds have a bright rim as they are illuminated and also being evaporated due to the activity of radiation indigenous neighboring hot stars. The region around the cluster of hot stars in the photo is fairly clear the gas as the mainly winds and radiation indigenous the stars have pushed the gas away. When this gas collides with and also compresses surrounding thick clouds, the clouds can collapse under their very own gravity and start to form new stars. The swarm of new stars in the upper left may have been created this way, as it is located on the rim of the large central interstellar bubble of the complex. The stars in this cluster room now beginning to clear far the cloud from their birth, and also are producing new opportunities for succeeding star birth.

Curious around the Universe, but don"t know where come start? have actually a look at this step-by-step guide to ending up being an amazing amateur astronomer. Http://

Life that a star

This ar covers the key stages that a star"s life, from infancy come old age. Learner will likewise discover why stars execute not all look the same and why castle evolve at different rates and also have various lifetimes: the is a an effect of having different masses. Lock will discover how important the mass of a star is in determining its evolution and also observable characteristics.

A star is thought about to it is in "born" once nuclear blend reactions start at its centre. Initially hydrogen is convert to helium deep inside the star. A star that is converting hydrogen to helium is called a main sequence star. Stars spend most of their resides as key sequence stars, convert hydrogen to helium at your centres or cores. A star might remain as a main sequence star for millions or billions of years.

Most that the stars in the Universe, about 90 %, are key sequence stars. The sun is a key sequence star.

Main sequence stars room not every the same. Castle have different masses once they space born, depending upon how much issue is available in the nebula native which castle formed. These stars can selection from around a tenth the the mass of the sun up to 200 times together massive. Various mass stars have different observable properties.

main sequence stars come in various sizes and also colours. Their sizes variety from approximately 0.1 to 200 times the size of the Sun. Their surface ar temperatures determine their colours and also can selection from under 3000°C (red) to end 30 000 °C (blue).

We usually associate red with being hot and also blue with being cold. But, in stars, the bluer the star, the hotter that is, and the redder it is, the older and also colder the is.

Main sequence stars also have various colours, depending upon the temperatures of your surfaces. Look in ~ the following picture and properly label the temperatures of all the stars making use of the perform of temperature below. I beg your pardon star to represent our Sun?

Temperature list: 3000 °C, 4500 °C, 6000 °C, 10 000 °C, 40 000 °C


The complying with image mirrors the exactly labels for the temperature of various stars:


The yellow star represents our Sun.

Why are hotter stars bluer in colour? can you mental what girlfriend learnt about the spectrum of visible irradiate in grade 8? The color blue coincides to irradiate at much shorter wavelengths (higher frequencies) 보다 the colour red. Shorter wavelengths (higher frequencies) exchange mail to higher energies and thus hotter temperatures. This is likewise seen in the flames of a fire or candle. If friend look at the flames, the main regions room bluer (and hotter) 보다 the external regions, which room orange and also yellow.

This artist"s impression mirrors the relative sizes that young stars, from the smallest "red dwarfs", at about 0.1 solar masses, short mass "yellow dwarfs" such as the Sun, to massive "blue dwarf" stars weighing eight times an ext than the Sun, and the 300 solar mass star called R136a1.
Observing Orion in the spring sky

Orion is an easily recognisable constellation clearly shows in cities and in dark skies. In this task learners will have to look at the night skies to clues the constellation and also identify the stars Betelgeuse and also Rigel and also note their distinction in colour. Orion is up in the eastern from about 00:30 in ~ the beginning of October, yet as the months development it rises earlier. By the start on December Orion is visible from about 20:30 in the east. If observing the constellation is unfeasible, you could ask learners to look at the image of the constellation in this thing instead.

This is the an initial direct picture of a star various other than the Sun, made with NASA"s Hubble an are Telescope. This is Betelgeuse, the star marking the shoulder that Orion, i m sorry we see in the bottom appropriate of the constellation, when viewing Orion in the southern hemisphere.

Betelgeuse is so vast that, if it replaced the sun at the facility of our solar system, that outer setting would expand past the orbit that Jupiter (see the range at reduced left that the image).


sky map


A clear skies is necessary for this task. Look external at night towards the east and identify the constellation of Orion. A picture of the constellation is had in this chapter because that reference. Determine the stars Betelgeuse and also Rigel.

At the beginning of October Orion is clearly shows in the eastern from approximately 00:30 until morning. Indigenous the beginning of November Orion is clearly shows in the east from roughly 22:30 and also from the start of December that is visible in the eastern from around 20:30.

exactly how long a main sequence star lives depends on how massive it is. More massive stars relocate onto the following stages of their lives much more quickly than lower mass stars. In reality they are main sequence stars because that a shorter time than reduced mass stars.

A higher-mass star could have much more material, however it likewise uses increase the material much more quickly due to its higher temperature. Because that example, the sunlight will spend around 10 exchange rate years as a key sequence star, but a star 10 times as enormous will critical for only 20 million years. A red dwarf, which is fifty percent the mass of the Sun, have the right to last 80 come 100 billion years.

When the hydrogen in the centre of the star is depleted, the star"s main point shrinks and also heats up. This reasons the outer part of the star, the star"s atmosphere, i beg your pardon is still greatly hydrogen, to start to expand. The star i do not care larger and brighter and also its surface ar temperature cools so it glows red. The star is now a red gigantic star. Betelgeuse, as you it was observed in the last activity, is a red gigantic star.

A colourful view of the globular star swarm NGC 6093 in the Milky Way, containing numerous thousands of old stars. Especially obvious are the bright red giants, which space stars comparable to the sunlight in massive that space nearing the end of your lives.

Globular clusters are particularly useful for researching stellar evolution, since every one of the stars in the cluster have actually the same period (about 10-15 exchange rate years), but cover a selection of mainly masses.

that is referred to as a giant since the external layers have broadened outwards and the star has got much larger than that was as soon as it to be a main sequence star.


Eventually the core of the star i do not care hot enough for the following nuclear reaction to start: atom of helium collide and also fuse right into heavier aspects such together carbon and also oxygen. However, ultimately the helium in the main point will additionally be depleted. From this allude onwards, the fate of the star is figured out by the mass.

For medium-sized stars, such together the Sun, the temperature in their centres will certainly never gain high enough to fuse the newly-formed carbon and also oxygen right into heavier elements and also so they perform not evolve lot further. Following the red huge phase, the star becomes unstable and also will ultimately die together you will uncover in the next section.

Scroll v this interactive animation to acquire a feeling of the range of some of the stars and also other objects in our Universe. Http://

The animation noted in the Visit box offers a really useful tool to give learners a feeling of the range of the Universe. If possible, you can project it up in your classroom and scale v it native a human being all the way out till you gain to several of the huge supergiants, and also then beyond. Friend will additionally be maybe to view the scale of some of the objects mentioned in this chapter, such together the Crab Nebula, the big Magellanic Cloud and Pillars that Creation.

The family member sizes the the Earth, the present day Sun and also a red supergiant star, Canis Majoris, in the constellation. The sunlight will ultimately evolve right into a red gigantic star in around 4.5 billion years time.
In this ar learners will discover how stars die. The emphasis is ~ above the fatality of a low mass star favor the Sun. However, for completeness, the method that high massive stars die is likewise briefly mentioned. There are two tasks in this section concerned the life the Sun-like stars. Both the these space intended to assist learners remember and understand the sequence of phases that a star choose the sun undergoes throughout its life. There is a many unfamiliar ax in stellar evolution and also it have the right to be confusing because that learners. Hope by doing activities rather than just reading around the different stages in a Sun-like star"s evolution, learner will discover the subject simpler to understand.

review interesting write-ups on the latest developments in astronomical research onSpace Scoop, an astronomy news service.

As a star beginning the final stages that its life, after it has come to be a red giant, the star becomes unstable and also expands and also contracts over and over. This reasons the star"s external layers to become detached from the main part that the star and they gently puff off right into space. Once the last of the gas in the star"s outer layers is puffy away, it forms an expanding shell roughly the core of the star called a planetary nebula. Planetary nebulae bright beautifully as they absorb the energy emitted native the hot main star. They can be discovered in plenty of different shapes, as displayed in the following images.

The plural of nebula is nebulae. Planetary nebulae have nothing to do with planets but were named like this in the 1700s because they resembled planets once observed v the telescopes the the time.

A planetary nebula is various to a stellar nebula. A stellar nebula is wherein stars are born, vice versa, a planetary nebula is what some stars form at the end of your lives.

The beautiful Ring Nebula. The gas is lit up by the light from the main star i beg your pardon is the pass out white period in the centre of the nebula.
The Boomerang Nebula is a young planetary nebula and also the coldest object found in the world so far.
Kohoutek 4-55 Nebula has the outer layers that a red large star that were expelled right into interstellar room when the star was in the so late stages that its life.
The Butterfly Nebula. The dying central star itself can not be seen, because it is hidden within a doughnut-shaped ring that dust.
The Dumbbell Nebula.
The Helix Nebula.

The Butterfly Nebula is a dying star the was once five times the massive of the Sun. What resembles the butterfly wings space actually hot clouds of gas tearing across an are at almost 1 million km an hour - fast sufficient to travel from planet to the Moon in 24 minutes!

Some time after ~ puffing turn off its outer layers, the central star will run out of fuel. Once this happens the main star starts to die. Gravity reasons the star to collapse inwards and the star becomes exceptionally dense and compact, around the dimension of the Earth. The star has then come to be a white dwarf star.

one ultraviolet photo of the Helix Nebula. As the star in the centre ideologies the end of that is life and runs out of fuel, that shrinks into a much smaller, hotter and also denser white dwarf star.

White dwarfs have actually this name because of their little size and also because they are so warm that they shine v a white hot light. The central parts that stars are much hotter than their surfaces, and also a white dwarf is do from the remaining central parts of a star which explains why they space so hot.

The adhering to image mirrors the family member size the Sirius B, a nearby white dwarf star, compared to several of the planets in ours solar system. Stars and also stellar remains deserve to be smaller than planets.


White dwarfs no longer develop energy via nuclear reactions and so together they radiate their energy into an are in the form of light and also heat. They gradually cool under over time. Eventually, once every one of their energy is gone, lock no much longer emit any kind of light. The star is currently a dead black dwarf star and also will remain like this forever.

White dwarf stars room so thick that one tespoon of product from a white dwarf would weigh as much as 100 000 kg.

This task can be performed in pairs or small groups. This activity demonstrates the life of a Sun-like star using a yellow balloon to represent the Sun. Learners must follow the accuse to demonstrate each that the phases that a star like the sunlight goes through during its life. This task is ideal completed in pairs wherein one member "gives the orders" and the various other member completes the activity. If you have time you can repeat the activity, swapping the bag around.


yellow ring balloon - one per pair or group black marker red mite scissors 2 cm small white styrofoam sphere - one every pair


In this activity you will work-related in pairs. Among you will certainly instruct your companion using the instructions below. Your companion will follow her instructions. Decision which of you will certainly be the instructor and also which of you will be the experimenter. Experimenter: Insert the white styrofoam ball right into the deflated balloon. Instructor: review out the step-by-step instructions native the table below (listed in order). Very first state the moment from the star"s birth which is offered in the left hand column, then tell your partner what to execute with the balloon. Experimenter: monitor the instructions from her partner an extremely carefully. You will certainly be demonstrating just how a Sun-like star evolves over time.

Step Number


1) Star is born

Blow up the balloon to around 6 centimeter in diameter

2) 5 million years


3) 10 million years


4) 500 million years

Wait - planets space being formed about the star.

5) 1 billion years

Blow the balloon increase a tiny bit

6) 9 exchange rate years

Blow increase the balloon some more and colour it

red - it is currently a red huge star

7) 10 billion years

Blow the balloon up a tiny bit. The external layers are now being swollen off. Come simulate this, slowly allow the balloon to deflate. Cut the balloon right into pieces and also scatter them around the white ball. The star has now end up being a white dwarf (the ball) surrounded by a planetary nebula (the pieces of balloon).

8) 50 exchange rate years

Move the planetary nebula farther away from the white dwarf.

9) 500 billion years

Remove the planetary nebula and colour the ball

black - the star is now a black color dwarf.

The different stages of evolution of a star choose the Sun room summarised in the diagram below and compared to the lifecycle that a person.

See more: The Charge Of A Beryllium 9 Nucleus Is, Regents Chemistry Exam Explanations January 2006


Let"s take it a closer look in ~ the life of ours star, the Sun.

The life bike of the sunlight


The diagram below shows the life of ours Sun. The sun is a common type of star of median size and also mass. Finish the sentence by filling in the gaps which summary the evolution of our sunlight over time.