4.1.1 How Stars Form

​How Stars Form
4.1.1

By Caitlin Ford

Objectives

- explain how protostars form from nebulae

- explain how a protostar evolves into a star

- identify the different properties of a star

Nebulae

A Nebula is a vast region of gas and dust.

 

They are enormous, with a single cloud weighing hundreds of thousands of times more than the Sun.

 

They can be the size of a solar system. Or bigger.

 

When particles pile up in one area of the nebula, gravity causes them to collapse.

The Collapsing Nebula

Nebula are cold, but when gas and dust clump, they warm up.

 

When the collapsing region of the nebula becomes 10,000AUs in diameter, it is called a pre-stellar core.

 

In 50,000 years, it shrinks to 1/10 the size.

 

As it shrinks, it starts to spin. It becomes a flat disk.  Material shoots from the top and bottom. The pre-stellar core becomes a protostar. 

Multiple Choice

Which force is primarily responsible for causing particles in a nebula to form clumps?

• gravitational force

• nuclear force

• magnetic force

• frictional force

A Star Forms

A protostar will continue to gather material, growing larger and hotter.

 

If it gets hot enough for nuclear fusion, it becomes a main-sequence star.

 

If fusion doesn't start, it becomes a failed star called a brown dwarf.

 

A star is considered stable when its gravity balances internal core pressure.

Wein's Law

The wavelength, or color, of light emitted by an object is determined by its temperature.

 

The light will be bluer if the object is extremely hot. The light will be redder if the object is cooler.

 

This is Wein's Law!

Apparent Brightness

Apparent Brightness - how bright an object appears from Earth

 

A negative number means brighter. A positive number means dimmer. This number represents the object's magnitude.

Abolute Brightness

Imagine placing ALL the stars at the same distance from Earth. Which one is the brightest now?

 

This is absolute brightness, a measure of the true brightness of a star.

 

The Sun is the brightest object in our sky, but if put at the same distance as every other star, it isn't that bright.

Hotspot

Which star is the hottest?

Luminosity

Luminosity - a measure of the total amount of energy radiated by a star or other celestial object each second

 

High luminosity stars emit a lot of energy, low luminosity stars emit less energy.

 

This depends on size and temperature of a star.

Star Size and Lifespan

Larger stars have shorter lifespans because they burn through their nuclear fuel faster, due to their higher internal temperatures and pressures.

 

Larger stars have more gravity and hotter cores than smaller stars.

Dropdown

When gas and dust collapse in a certain area of a nebula, the temperature gradually ​

Select answer

.

Hotspot

Which of these objects is the brightest from an observer on Earth's surface?

Drag and Drop

If a star has more mass, it will have​

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gravity and a ​

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lifespan.

If a star has less mass, it will have ​

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gravity and a​

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lifespan.

Drag these tiles and drop them in the correct blank above

more

shorter

less

longer

Great Job!

Today, you learned: 

- how protostars form in nebulae

- how a protostar becomes a star

- about the different properties of a star