11 The Earth in space

Question 1

What is the Sun’s temperature on its surface and its centre?

Answer 1

Surface - 6000°C; centre - 15 million °C

Question 2

What is the diameter of the Sun, the Earth and the Moon?

Answer 2

Sun - 1,390,000 km; Earth - 12,800 km; Moon - 3500 km

Question 3

What is the distance between the Earth and the Sun? (average)

Answer 3

149,600,000 km

Question 4

What is the distance between the Earth and the Moon? (average)

Answer 4

384,000 km

Question 5

By what value is the Earth’s axis tilted?

Answer 5

23.5°

Question 6

What causes seasons?

Answer 6

Earth’s tilt, which causes differing hours of sunlight in orbit, and Sun’s radiation being more or less spread out in parts of orbit

Question 7

How long does it take for the Moon to move around the Earth?

Answer 7

27.3 days

Question 8

What are the phases of the Moon?

Answer 8

New Moon, waxing crescent, first quarter, waxing gibbous, Full Moon, waning gibbous, third quarter, waning crescent

Question 9

What are the objects of the Solar System, in order from closest to farthest from the sun?

Answer 9

Mercury, Venus, Earth, Mars, asteroids, Jupiter, Saturn, Uranus, Neptune, Pluto (dwarf planet)

Question 10

The orbits of which planets in the Solar System are more of an ellipse?

Answer 10

Mercury and Mars

Question 11

What are the distances of the planets of the Solar System from the Sun in million km?

Answer 11

Mercury - 58, Venus - 108, Earth - 150, Mars - 228, Jupiter - 778, Saturn - 1420, Uranus - 2870, Neptune - 4490

Question 12

What can “ice” in space mean to astronomers?

Answer 12

Frozen water, frozen carbon dioxide, methane, or ammonia

Question 13

How is Uranus’ axis of rotation tilted?

Answer 13

More than 90°

Question 14

What are asteroids, comets, meteors and meteorites?

Answer 14

Asteroids can range from a few km up to 1000 km, most have orbits between those of Mars and Jupiter; comets have highly elliptical orbits with an icy lump to be the head, several km across, and tail million of km long formed by particles of dust and gas; meteors are tiny grains of material hitting the Earth’s atmosphere; meteorites are chunks of material which hit the ground

Question 15

What did Isaac Newton find out about gravity?

Answer 15

It obeys an inverse square law, doubling distance between two masses reduced gravitational force to a quarter

Question 16

What are satellites and their types?

Answer 16

Any object in orbit around a more massive one; natural satellites present through nature, artificial satellites man-made

Question 17

What is geostationary orbit?

Answer 17

An orbit where the satellite’s period matches the time taken for the Earth to rotate (24 hours)

Question 18

What conditions must be met to be geostationary?

Answer 18

A satellite must be put in a circular orbit of 35,900 km above the equator, with a required speed of 11,100 km / hour

Question 19

What are the different types of satellites and their purposes?

Answer 19

Communications satellites beam signals from one part of the Earth to another; Navigation satellites used to help objects locate their position; Monitoring satellites scan and survey the Earth; Astronomical satellites observe distant stars and galaxies

Question 20

What is a light year?

Answer 20

A unit of distance describing the distance travelled by light in one year, 1 light year = 9.5 * 10^12 km

Question 21

What is the nearest star to the Sun?

Answer 21

Proxima Centauri

Question 22

How large is the Milky Way galaxy and how many stars are in it?

Answer 22

More than 100,000 light years across; contains at least 100 billion (10^11) stars

Question 23

When do scientists think that the Sun and the rest of the Solar System formed?

Answer 23

About 4,500 million years ago

Question 24

How does a star and the system around it form?

Answer 24

Huge, rotating cloud of gas and dust called nebula; slowly collapses inwards due to gravity, rotating faster; protostar heated up, temperature rising and nuclear fusion eventually occurring creating star; outward pressure from radiation balanced gravity and grains pulled into clumps turned into planets and moons in accretion disc around star

Question 25

Where did the gas giants form and inner planets form and why?

Answer 25

Sun's radiation drove off most of gas from inner planets, so they were left small and rocky, but further out planets retained gas and became gas giants

Question 26

What percentage of the Sun is hydrogen and helium?

Answer 26

Sun is 73% hydrogen and 25% helium

Question 27

What will happen to the Sun in the future (general fate of stars too)?

Answer 27

In about 6 billion years, all hydrogen in core converted into helium, core will collapse, and outer layer will expand to about 100 times present diameter and glow red (red giant), outer layer will drift into space, exposing dense hot core called white dwarf which will fuse helium into carbon, after which it will cool and fade forever

Question 28

What happens to stars larger than our Sun?

Answer 28

Become red supergiants, explode in supernova, and leave behind neutron star if core can resist gravity, or black hole if core can't resist gravity

Question 29

How are very heavy elements (like gold and uranium) formed, and why?

Answer 29

Extreme conditions creating a supernova required, to make elements heavier than iron, energy must be supplied for fusion and isn't released by it

Question 30

How can supernovae be used to estimate galactic distances?

Answer 30

All type 1 a supernovae have same brightness at peak, by comparing apparent brightnesses, their relative distance can be calculated

Question 31

What is the Doppler effect and red shift?

Answer 31

Doppler effect is when light waves' wavelengths from objects moving away from Earth at high speed become stretched out; red shift is wavelengths shifted towards red end of visible spectrum

Question 32

What is the Big Bang theory?

Answer 32

A theory where the Universe (and time) began many billions of years ago when a single, hot "superatom" erupted in a burst of energy called the Big Bang, all matter in the Universe coming from this

Question 33

What is cosmic microwave background radiation (CMBR)?

Answer 33

Microwave radiation of particular frequency coming from every direction in space, may be heavily red-shifted remnants of radiation from the Big Bang

Question 34

What are two pieces of evidence to support the Big Bang theory?

Answer 34

All galaxies appear to be moving apart, radio telescopes have picked up cosmic microwave background radiation (CMBR)

Question 35

What is the hubble constant?

Answer 35

Scientists now agree on value of 2.3 * 10^(-18) per second

Question 36

What is the formula for the age of the Universe?

Answer 36

age of universe = 1 / hubble constant