science space notes part 2

7/31/2019 Science Space Notes Part 2

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The Sun

Composed of many layers of gas Suns energy comes from nuclear fusion reaction which occurs at the core of the Sun

and produces large amounts of quantities

Energy released by the fusion makes its way to the photosphere, where light and otherradiation escapes

Solar energy is the driving force behind the Earths weather and climate, and alsoprovides the energy needed for life to exist on Earth

Stars

1. Mass: Mass of our Sun is 2x 1630 kg or 1 solar mass Solar mass is the mass of other stars compared to our Sun E.g. the mass of the star A1, a very massive star, has the solar mass of 118

meaning it has a mass 118 times greater than that of our Sun

2. Temperature: Related to its colour Hottest to coldest: Bluewhiteyelloworange - red The colour of the star determines its life stage

3. Composition of stars: Using a special instrument called a spectroscope Splits up light so we can see lines of colour Each element emits only certain frequencies of light Helps us determine what kinds of elements are found in a star

Life Cycle of a Star:

Every star has a life cycle. Our Sun has been around for almost 5 billion years but still is inthe middle of its life cycle

5 major stages: Birth and early lifeMain sequence phase

Old age

Death

Remains

2 Main Forces that Affect Birth, Maintenance and Death of Stars:

1. Gravitational Force: As mass increases, gravity increases and mass will attract other masses

towards its center

2. Nuclear Fusion: At very high temperatures and pressures, particles collide and fuse together,

creating new elements

Releases a lot of energy, and is responsible for the luminosity of starsStage 1: Birth and Early Life

Stars begins in a nebula-huge cloud of dust and gases (mainly hydrogen and helium)


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Gases in the nebula are unevenly distributedsome denser pockets, some less densepockets

Nebulas can extend thousands of light years in space As materials gather, density, temperature and pressure increase producing energy in

forms of a proto star

Proto stars grow bigger as they pull in more gases and dust, increasing its gravity anddensity

Stage 2: Main Sequence Phase (Adulthood)

As core temperatures reach a critical point (15 million C), nuclear fusion begins Hydrogen atoms join to form helium atoms, producing enormous amounts of energy and

radiation, causing outer gas layers to burn

Average stars like our Sun will burn for 10 billion years, but larger massed stars will burnmuch brighter for a shorter period

Stage 3: Old Age

When stars hydrogen supply begins to deplete, the stars expand and cool They become red giants or red supergiants depending on their original mass

Stage 4: Death

A star dies when nuclear fusion stops For a star (like our Sun), the outer layers of gas are released and the core shrinks to

become a small, hot, dense white dwarf

A more massive star will collapse on itself, but the outer layers will explode as a supernova

Stage 5: Remains

White dwarf stars will eventually cool and fade away, possibly releasing gases into thenebulae

More dense stars may form a neutron star or even a black holeSummary Of A Stars Life Cycle

Formation of a star:Nebulaproto starmain sequence star (adult)

Death of a star like our Sun):Main sequencered giantwhite dwarf

Death of a star with 10-20 solar masses:Main sequencered supergiantsuper novaneutron star

Death of a star with >30 solar masses:Main sequencered supergiantssuper novablack hole

Rotation vs. Revolution

Viewed from above, the Earth makes a complete counter clockwise rotation (spins on itsaxis) once in each 24 hr period

This is why the Sun appears to rise in the east and sets in the west The Earth also revolves counter clockwise around the Sun once every 365 days


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Earth also wobbles on rotational axisprecisiontraces a circle every 26 000 yrsThe Earths Orbit around The Sun

The Earths orbits around the Sun in 365.25 days In a elliptical orbit

The seasons change primarily because of Earths tilt, on top of the changes in the EarthSun distance

During the summer, the north hemisphere leans towards the Sun:-Longer days, more concentrated sunlight, hotter (shorter shadows in the summer)

During the winter, the north hemisphere leans away from the Sun:-Shorter days, Sun hits at an angle, appears lower in the sky

-Less intense heat because rays are spread out

Northern Hemisphere

When the Earth is furthest away from the Sun, the Earths axis is most inclined towards oraway from the Sun

Summer Solstice

When the Earth is most inclined towards the Sun (June 21Summer Solstice)-Northern Hemisphere receives more direct sunlight

-Warmer temperatures, longer days

Winter Solstice

When Earth is the most Inclined away from the Sun (Dec. 21Winter Solstice)-Northern Hemisphere receives less direct sunlight (light is spread out over a larger

area)

-Cooler temperatures, shorter days

Equinox

There are two days of equal daytime and high time hours, at Mar 21st and Sept 21stTheyare called equinoxs

-Vernal Equinox: March 21

-Autumnal Equinox: September 21

Eclipses

Darkening of a celestial object due to the position of another celestial object

Solar eclipse:From Earth, the Sun and Moon appear the same size

When Moon aligns between the Earth and the Sun, it blocks the Sun from being

observed

During a solar eclipse, only the Suns corona is visible

Lunar Eclipse:When the Earth is directly between the Sun and the Moon

This causes Earth to cast a shadow on the Moon making it look orange-red

Tides


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The rise and fall of the water levels/ oceans surface Caused by gravitation pull of Moon and sometimes Sun Creates bulges of water to form on the side of the Earth facing the Moon as well as the

opposite side

During lunar cycle (when Earth, Sun and Moon are aligned), high tides form due to extragravitational pull

science space notes part 2

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