Constellations & Stars

1. Constellations & Stars

2. I. Constellations • Group of stars that appear to form a pattern in the sky. • 88 recognized by International Astronomy Union

3. A. Zodiac • Band of 12 constellations along the ecliptic.

4. B. Ecliptic • – the plane of the Earth’s orbit around the sun • The apparent path that the sun (and planets) appear to move along against the star background.

5. Ecliptic

6. C. Circumpolar Constellations • Can be seen all year long • Never fully set below the horizon • Appear to move counter clockwise around Polaris • Caused by Earth’s Rotation

7. Circumpolar Constellations

8. Star Trails

9. Examples of Circumpolar Constellations • Ursa Major – The Big Bear • Ursa Minor – The Little Bear • Cassiopeia – Queen on Her Throne • Draco- The Dragon • Cepheus- The King

10. # of stars seen as circumpolar depends on the observers latitude • Further North the observer lives, the more stars will appear circumpolar • Earth turns west to east • Sky appears to turn east to west

11. D. Ursa Major • Best known constellation • Common name is Big Dipper • Pointer stars- front 2 stars of the Big Dipper which point to Polaris (North Star)

12. II. Seasonal Changes in Constellations • Big Dipper • In Fall: Low over northern horizon • Spring: High overhead • Cassiopeia • In Fall: Straight overhead • Spring: Low over northern horizon

13. Seasonal Change & Nightly change of the Dippers

14. III. Summer Constellations • 1st 3 bright stars that rise form the Summer Triangle • Vega- in Lyra the Harp • Altair- in Aquilla the Eagle • Deneb – in Cygnus the Swan (Northern Cross)

15. Summer Triangle

16. IV. Most Famous Winter Contellation • Orion Contains: • Betelgeuse (Bet el jooz) a bright red super giant star found forming Orion’s right shoulder • Rigel – a blue super giant: 7th brightest star in the nighttime sky

18. 3 Stars of Orion’s Belt • Can be used to find 2 other constellations & a star cluster • Canis Major- (Big Dog) follow the line made by the 3 stars of Orion’s belt down to the left • Sirius-the brightest star in the nighttime sky is found in Canis Major

19. 2. Taurus (the Bull) • Follow the line made by Orion’s belt up & to the right • Aldebaran- Red star that is the eye of the bull is the 13th brightest in the nighttime sky

20. 3. Pleiades Star Cluster (7 sisters) • Follow the line made by Orion’s belt up to the right, go through Taurus to a clump of stars to the right. • Called Subaru in Japan – means “Unite”

21. V. Kinds of Stars • Red Giant - large red star at least 10x diameter of the sun • Old Stars • Ex. Aldebaran • The sun will swell into a Red Giant when it is old

22. B. Super Giant • Largest of all stars 100x more luminous • Explode as a Super Nova • Can form Black Holes • Ex. Betelgeuse, Rigel, Polaris

23. C. Dwarf Stars  • Less luminous • Very dense, mostly carbon • Tightly packed nuclei • Remains of a red giant that ran out of fuel • 1 cup full of star =20 tons or 5 elephants.  • Most are red/orange/yellow • White dwarf is the exception to the color • Sun is a yellow dwarf

26. Size Comparison of Various Stars

27. VI. Variable Stars • Change in brightness over regular periods of time • Ex. Cepheid Variables/Pulsating Stars Binary Stars & Eclipsing Binary Stars

28. A. Cepheid Variables/Pulsating Stars • Change in brightness as they expand & contract • Unequal balance between gravity & nuclear fusion • Ex. Polaris, Betelgeuse

29. B. Binary Star Systems • Two stars of unequal brightness revolving around a center point • Ex. Algol & its companion star in Perseus

30. C. Eclipsing Binary Stars • Two close stars that appear to be a single star varying in brightness. • The variation in brightness is due to one star moving in front of or behind the other star. Occurs because we see the system on edge instead of from above or below

31. VII. Pulsars or Neutron stars • Discovered in 1967 (LGM) • A distant heavenly object that emits rapid pulses of light & radio waves • Formed when a Super Giant collapses; Protons & Electrons are forced so close together that they fuse and form only neutrons 

32. Twinkle Twinkle Little Star "Twinkling Stars" are due to Earth's atmosphere

33. VIII. Life Cycle of a Medium Mass Star • Nebula • Protostar • New/Stable State Star • Red Giant • Planetary Nebula • White Dwarf • Black Dwarf

34. 1. Nebulae (Plural of Nebula) • Space gas seen as faint glowing clouds • Mostly hydrogen    • Star dust is extremely small, smaller than a particle of smoke & widely separated, with more than 300 ft. between individual particles. • Nebulae still hinder star gazing because they absorb light which passes through them.

35. Types of Nebulae • Diffuse Nebula - gases glow from stars w/in them Ex. Nebula found in Sagittarius

36. Types of Nebulae • Dark Nebula- nebula not near a bright star  • Ex. Horse Head Nebula in Orion

37. 2. Protostar • Shrinking gas balls, caused by a swirl of gas forming dense areas.  • The gravity of the dense swirl in turn attracts nearby gases so a ball forms. • Nuclear fusion occurs & Helium is formed from Hydrogen • A new star is born in our galaxy every 18 days

38. 3. Stable State Star • Star that releases energy in enough force to counter balance gravity • Star stops contracting • Also known as a main sequence star • Ex. Sun

39. 4. Planetary Nebula • The outer layers of the Red Giant puff out more and more. • The star loses gravitational hold on its outer layers and they get pushed away by the pressure exerted from solar winds

40. Planetary Nebula

41. 5. White Dwarf • Fuel is used up • No nuclear fusion occurring • Remaining heat radiates into space

43. IX. Life Cycle of a Massive Star • 1st three steps are similar • Super Giant • Super Nova • Neutron Star / Pulsar • Black Hole

44. 1. Super Giant • Rare stars, largest of all • 100x more luminous • Only stars with a lot of mass can become super giants • Some are almost as large as our entire solar system • Ex. Betelgeuse & Rigel

45. 2. Super Nova • Explosion from a massive Super Giant • Outer layer blasts away at end of Life Cycle • Emits light, heat, X-rays, & neutrinos • Leaves behind a neutronstar or black hole

46. 3. Neutron Star/ Pulsar • The remains of a super nova • Very small, super-dense star which is composed mostly of tightly-packed neutrons • Rapidly spinning leftovers of a star • Emits energy in pulses

47. 4. Black Hole • Occurs when a star's remaining mass is greater than three times the mass of the Sun • Star contracts tremendously • Incredibly dense with a gravitational field so strong that even light cannot escape.

48. Life Cycle of a Massive Star

49. X. Distance to stars • The Sun is closest star to Earth • Takes light 8 minutes to reach Earth • Avg. distance:150,000,000Km = 1 AU distance from Earth to the Sun • Next nearest star is Proxima Centauri4.2 light years away; it can only be seen in the southern hemisphere

50. E. Light year • The distance light has traveled in a year • 9.5 x 1012 Km/yr • Speed of light 300,000 Km /sec