THE STARSThe Main Sequence Stage

By Giulia Greco, 5D

The Birth of a new star

Gravity

Pressure

Compression of the central core

Result: increase in temperature 4 million °C

Material in new star

• Hydrogen (about 75 %)

• Helium (about 24 %) • Others elements (about 1 %)

• over 90 % of all atoms• orignated by the Big Bang

Hydrogen Fusion

When temperature = 5,5 million °C

Collision of hydrogen’s protons

FUSION

migrates up to the surface and escapes into space

Stable fusion equilibrium

• Hydrogen fusion explosion• Gravity compression

Prevents the destruction of the star

Particular size

Solar Wind

• Explosions in the core high temperature (over 11 million °C)

• Hot matter fly off into space

Like a wind•1 million km per hour• Blows away the remaining gas

Regular main sequence

• Size: similar to Sun• Color: from white to yellowish

Surface temperature

Hot temperature

blu to blu-white

average temperature

white to yellowish

Cold temperature orange to red

HR Diagram• Hot fast short• Cold slow long

Red Dwarf

• most common Main Sequence star size

• 10% to 50% the size of Sun• fusion rate: low• need telescopes • PROXIMA CENTAURI

Up to 70 % of all star in Milky Way galaxy are Red Dwarf

Yellow Giants or White Giants

• 5 to 50 times larger than Sun• fusion rate: fast

• naked eyeBecause: mass = greater

core temperatures = hotter

Blue or Blue-White SuperGiants

• Hydrogen to last only 100 million yearShort life

• SummaryBlue Supergiants

Blue – White Supergiants

Yellow or White GiantsYellow to White Regular Stars

Red Dwarfs

The Sun• Surface temparture: 5500°C• Core temperature: over 14 milllion °C• It is in equilibrium• Hydrogen fusion for about 5 bilion more years• Solar wind

Proxima Centauri

• The closest star to the Sun• Red Dwarf : 8 % the size of sun• Invisible from Earth• no plants or solar system

Rigel Kentaurus

• Near to Proxima Centauri triple star system• Pair of yellow main sequence star:

Kentaurus A and B

Similar in size, temperature age to our Sun

Sirius A – Canopus - Rigel

• Stars larger than our Sun– Sirius A: twice as large as our Sun

White Main Sequence star– Canopus : 62 times larger than our Sun White to Yellow-White Giant star– Rigel: 68 times bigger in diameter than our Sun

Blue – White Supergiant