Stars are massive, luminoussphere of hot gas cloud, heldtogether by gravity, main elementis Hydrogen. StarsProperties of 1. generate energy by itself 2. Have an evolution to build a massive element such as Helium , Lithium and Beryllium The nearest star to Solar system is Alpha Centauri
Star-forming region in Orion’sBelt
Cloud Collapse - occurs deep in cloud
“Pillars of Creation”Visible light - Hubble Near Infrared lightSpace Telescope (HST) - ESO Very Large Telescope (VLT)
“EGGS” (Evaporating Gaseous Globules)Dense regions forming new stars -surrounding gas & dust “eaten into”by strong stellar winds, UV photons& ionization fronts
QuickTime™ an d a Sorenson Video deco mpressor are need ed to see this p icture .IR (infrared) seesdeeper than visiblelight & detects thermalemission of warm dust
Dark clouds &deeply embeddedyoung stars withgas outflows andHerbig-Haro (HH)objects
Someyoungdisks & jetsrevealed
“proplyds”(protoplanetary disks)seen in star-formingregions
6.1 Stars Evolution The formation of a star beginswith gravitational instability withinthe nebula. When the hot cloud hasapproximately reached the stablecondition of hydrostaticequilibrium, a Protostar.
• Low mass stars , not much light , use less fuel , have a long life and end up not a bomb.• Massive stars that are very light and fuel consumption rate is very high. Will have a short life span. And ending with a violent explosion called a supernova.
Mass of protostar (M) Star Evolutioncomcompare with Mass of the Sun MM ≥ 25 M Blue giant star Final : Black Hole9M ≤ M ≤ 25M Blue giant star Red giant star Final : Neutron Star
Conclusio n: Super massive Stars Blue giant star Supernova Black hole Nebula
Massive Stars Red Giant Star Supernova Neutron Star + Nebula
Small star Red giant star white Dwarf planetary nebula
6.2 Birth andevolution of the Sun
G25,000 10,000 100 1100
6.3 Brightness and Magnitude Brightness 1Magnitude
1 2.512 5 2.512 5100 -26.7 -4.5 -0.5 0.45 1.2
Apparent magnitude describes the relativebrightness of objects as they appearsin sky from the Earth. Absolute magnitude the apparent magnitude itwould have if it were at a distance of10 parsecs (32.6 light-years) fromEarth.
6.4 Color andTemperature
Color of the star related tosurface temperature , is divided in 7 Spectraltype. And related to lifetime ofstars. ( ) thatthe youngest stars is Blue , theoldest stars is Red.
O O 9.5 30,000B 30,000- B3 10,000A 10,000- A2 7,500F 7,500- F5 6,000
6.5 Determination of Distance Parallax) 2
•• Parsec” Parallax Angle of 1 Arc Second AU•
• r = 1/p r= distance) pc) p= parallax angle)
Regulus) r = 1/p = 1/(0.04) x 3.26 = 81.5 x 206,265 = …………….AU
1. Great Nebula)• M42
2.•• IC 434
3.•• Charles Messier M1
4.• Monoceros)• NGC 2237
5. Trifid Nebula)•
6.7 Stellar system 1. Binary star systems: two stars are gravitationally bounded and they orbit each other ex. Sirius , Procyon 2. Triple star systems : Alpha Centauri A,B,C 3. Star cluster ex. The Pleiades , Great Globular Cluster in Hercules M13.
6.8 Mass of the Stars• Mass is the matter of the Star• Tiny Star have low gravitational force, low pressure of hot gas, useless fuel.• Measuring the mass of distant stars is Newton’s version of Kepler’s Third Law of orbital motion because motion period