Space

1. Space

2. Perspectives of Earth • Summer solstice (June 21) – the longest period of daylight; the start of summer • Winter solstice (December 21) – the shortest period of daylight; the start of winter • Solstices are reversed in the southern hemisphere • Equinox: day and night are of equal length (March 21 and September 22)

3. The Celts created Stonehenge to mark winter and summer solstices. • African cultures made large stone pillars into patterns to predict the timing of the solstices • Useful to know when to plant and harvest crops

4. Stonehenge is angled such that on the equinoxes and the solstices, the sun rising over the horizon appears to be perfectly placed between gaps in the megaliths.

5. Orbits • Ecliptic: path of the sun through the sky during the year, crosses the celestial equator at the vernal (spring) and autumn (fall) equinoxes. • The Sun’s northerly position on the ecliplipse marks summer solstice. Its most southerly position marks winter solstice.

7. Inuit: the width of a mitt held at arm’s length to gauge the height of the sun above the horizon. When the sun rose to the height of one mitt width, it meant the seal pups would be born in two lunar cycles. • The sun played a role in mythology of ancient cultures (North American natives, Aztecs, Chinese, Inuit, Greeks, Norse, Japanese). • Ancients used rock structures and buildings to align with stars (2700 BC pyramids built in Egypt, Stonehenge).

8. Models of Planetary Motion • 2000 years ago Aristotle developed the geocentric model (Earth-centered model) • Earth was at the center with concentric spheres encircling it • The distant stars were fixed on the outermost or celestial sphere • Predicted the phases of the moon, but little else

9. Ptolemy added epicycles, smaller spheres attached to the main spheres. This helped make predictions more accurate.

10. In 1530 Copernicus developed the Heliocentric model: the sun at the center and planets revolved in orbits around it. • In the 1600s, Galileo used a telescope to provide observations to back up this model

11. Johannes Kepler: orbits of the planets were elliptical, figured out the shape and scaled the entire solar system from the same observations. • Sir Isaac Newton explained elliptical orbits by proving that there is a gravitational attractive force between all objects that pulls them together in an orbit.

12. Ancestral Contributions • stars make unchanging patterns in the sky which looked like named objects • use the movement of stars to mark months and seasons, led to the development of the calendar • the Sun, Moon and Planets rise and set at different rates from the stars

13. 7000 years ago, sundials were used to measure the passage of time • Egyptians invented a merkhet to chart astronomical positions and to predict the movement of stars. • Egyptians designed a quadrant to measure a star’s height above the horizon. • Arabian astronomers used an astrolabe to make accurate charts of star position.

14. Levi ben Gurson invented the cross staff to measure angle between the moon and a star. • Hans Lippershey invented the telescope in the late 16th century. • Galileo Galilei improved the telescope and it revolutionised astronomy. He concluded that the stars are much farther away than the planets.

16. Kepler described the elliptical shape of the planet’s orbits. • Isaac Newton: law of universal gravitation an explanation for the planets’ elliptical orbits. • The introduction of mathematical approaches (Kepler and Newton) into describing the motion of objects within the universe allowed astronomers to make accurate predictions about the motion of objects in the universe.

17. Distribution of Matter in Space • Astronomical Units (AU): used for measuring “local” distances, inside our solar system. One AU is equal to the average distance from the center of the earth to the center of the sun (149 599 000 km). Astronomers use this when describing the positions of the planets relative to the sun. • Light-year: equals the distance light travels in one year. Used for measures beyond our solar system.

18. Star Classification and Life Cycle • Star: a hot glowing ball of gas (mainly hydrogen) that gives off light energy. The number of stars in the universe is in the billions. • Stars vary greatly in characteristics • The color of a star depends on its temperature. A very hot star looks blue. A very cool star looks red. • Hertzsprung and Russell: compared the surface temperature with brightness (luminosity). Star distribution in their diagram is not random – there are several specific groupings.

20. Nebulae (Prostar): area of space where huge accumulations of gas and dust collect and where stars are formed. • Each nebulae is composed of 75% hydrogen and 23% helium. The other 2% is oxygen, nitrogen, carbon and silicate dust. • Some of this interstellar matter came from exploding stars. Depending on the mass of the star formed from a particular nebula, the star will be sun-like (in terms of mass) or massive. • Both types of stars spend most of their lives in this main sequence converting hydrogen to helium in their cores.

21. Paths of Star Development • Nebula  sun-like stars (main sequence)  red giant  white dwarf  black dwarf • Nebula  massive stars (main sequence)  red supergiant  supernova  black hole

22. Red Giant/Red Supergiant: when a sun-like star increases in size and becomes very bright. • White Dwarf: when a sun-like star collapses: white dwarfs are very hot but very faint. • Black Dwarf: when a white dwarf fades. • Supernova: an enormous explosion that marks the death of a massive star.

23. Black Hole: a dense remnant of a super nova; an object around which gravity is so intense even light cannot escape. Neutron Star: If the explosion does not destroy a star, the core is left as a neutron star. Black Hole

25. Constellations: groupings of stars we see as patterns in the night sky. • Asterism: distinctive star grouping that is not one of the 88 constellations (e.g. Big Dipper which is part of the Ursa major constellation). • Galaxy: a grouping of billions of stars, gas and dust held together by gravity.

27. Shapes of Galaxies • Spiral: long curved arms radiating out from a bright central core • Elliptical: football or egg-shaped which is made up of old stars • Irregular: no shape and smaller than the other 2; made up of young and old stars

28. Bodies Making Up Solar Systems • Protoplanet hypothesis (explains the birth of solar systems): • A cloud of gas and dust in space begins swirling • Most of the material (more than 90%) accumulates in the centre, forming the sun • The remaining material accumulates in smaller clumps circling the centre. These form the planets.

30. Solar Wind: streams of electrically charged particles discharged by the sun in every direction. • Solar wind is the result of solar flares, explosions that force particles from the sun into space. • Some of these particles spiral down the Earth’s magnetic field and enter the atmosphere to produce the Northern and Southern lights (Aurora Borealis and Aurora Australis).

32. Sun: the centre of our solar system, 110 times wider than the Earth. • The solar system can be divided into two planetary groups: the Earth like (terrestrial)planets and the outer or Jovian planets. • Terrestrial planets: smaller, rockier, closer to the Sun. • Jovian planets: large and gaseous, located greater distances from the Sun with small densities, rings, and many satellites.

33. Size of space objects • Milky Way (galaxy) > Solar System > Planets (Jovian > Terrestrial) > Moons • Asteroids: small, rocky or metallic, range in size from a few meters to several hundred kilometers across and are found between the orbits of Mars and Jupiter. • Comets: “dirty snowballs” made up of dust and ice, have bright center and a long faint tail that always points away from the Sun. Ex. Halley’s comet.

34. Meteoroids: small pieces of rock flying through space with no particular path, are as small as a grain of sand or as large as a car. • Meteor: (shooting stars) When a meteoroid gets pulled into the atmosphere by Earth’s gravity, the heat of atmospheric friction causes it to give off light. • Meteorite: a meteor that hits the Earth’s surface

36. Eclipses • A solar eclipse occurs when the moon passes between the Sun and Earth casting a shadow on Earth. • A lunar eclipse occurs when Earth passes between the Sun and Moon, casting its shadow over the Moon.

38. Determining Position and Motion in Space • To locate the position of an object in space two questions must be answered, “How high in the sky is it?” and “In which direction?” • This problem can be solved with two measurements. The first is the compass direction called azimuth, with north as 0. The second is how high in the sky and is called altitude, which ranges from 0 to 90 degrees. Zenith refers to highest point directly overhead.

41. Spectrometry or Spectrometers • Spectroscopes tell us how fast a celestial body, such as a star, is moving toward or away from us using the Doppler Effect. • Light refracted from stars creates a ‘fingerprint’ for each star. Astronomers compare the spectra of a star with known spectra of elements (H, He, Na, Ca) to determine a star’s composition.

47. The Doppler Effect occurs when sound waves are compressed in front of a vehicle as it speeds along. This results in a shorter wavelength and a higher pitch. • Behind the vehicle sound waves stretch out, creating a longer wavelength and lower pitch. • It can also be used in radar guns to show how fast a vehicle is moving.

49. The Doppler effect can apply to light-emitting objects such as stars. • When a star is approaching you, its wavelengths of light become compressed. As a result, the dark lines in the star’s spectrum shift toward the shorter-wavelength end of the spectrum – the blue end. • If a star is moving away from you, its spectral lines will be red shifted (moving toward the longer-wavelength part – red end- of the spectrum). • The amount of shift showing up in observations indicates the speed at which the star is approaching or receding.