11 The Earth in space Flashcards
What is the Sun’s temperature on its surface and its centre?
Surface - 6000°C; centre - 15 million °C
What is the diameter of the Sun, the Earth and the Moon?
Sun - 1,390,000 km; Earth - 12,800 km; Moon - 3500 km
What is the distance between the Earth and the Sun? (average)
149,600,000 km
What is the distance between the Earth and the Moon? (average)
384,000 km
By what value is the Earth’s axis tilted?
23.5°
What causes seasons?
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
How long does it take for the Moon to move around the Earth?
27.3 days
What are the phases of the Moon?
New Moon, waxing crescent, first quarter, waxing gibbous, Full Moon, waning gibbous, third quarter, waning crescent
What are the objects of the Solar System, in order from closest to farthest from the sun?
Mercury, Venus, Earth, Mars, asteroids, Jupiter, Saturn, Uranus, Neptune, Pluto (dwarf planet)
The orbits of which planets in the Solar System are more of an ellipse?
Mercury and Mars
What are the distances of the planets of the Solar System from the Sun in million km?
Mercury - 58, Venus - 108, Earth - 150, Mars - 228, Jupiter - 778, Saturn - 1420, Uranus - 2870, Neptune - 4490
What can “ice” in space mean to astronomers?
Frozen water, frozen carbon dioxide, methane, or ammonia
How is Uranus’ axis of rotation tilted?
More than 90°
What are asteroids, comets, meteors and meteorites?
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
What did Isaac Newton find out about gravity?
It obeys an inverse square law, doubling distance between two masses reduced gravitational force to a quarter
What are satellites and their types?
Any object in orbit around a more massive one; natural satellites present through nature, artificial satellites man-made
What is geostationary orbit?
An orbit where the satellite’s period matches the time taken for the Earth to rotate (24 hours)
What conditions must be met to be geostationary?
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
What are the different types of satellites and their purposes?
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
What is a light year?
A unit of distance describing the distance travelled by light in one year, 1 light year = 9.5 * 10^12 km
What is the nearest star to the Sun?
Proxima Centauri
How large is the Milky Way galaxy and how many stars are in it?
More than 100,000 light years across; contains at least 100 billion (10^11) stars
When do scientists think that the Sun and the rest of the Solar System formed?
About 4,500 million years ago
How does a star and the system around it form?
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
Where did the gas giants form and inner planets form and why?
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
What percentage of the Sun is hydrogen and helium?
Sun is 73% hydrogen and 25% helium
What will happen to the Sun in the future (general fate of stars too)?
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
What happens to stars larger than our Sun?
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
How are very heavy elements (like gold and uranium) formed, and why?
Extreme conditions creating a supernova required, to make elements heavier than iron, energy must be supplied for fusion and isn’t released by it
How can supernovae be used to estimate galactic distances?
All type 1 a supernovae have same brightness at peak, by comparing apparent brightnesses, their relative distance can be calculated
What is the Doppler effect and red shift?
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
What is the Big Bang theory?
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
What is cosmic microwave background radiation (CMBR)?
Microwave radiation of particular frequency coming from every direction in space, may be heavily red-shifted remnants of radiation from the Big Bang
What are two pieces of evidence to support the Big Bang theory?
All galaxies appear to be moving apart, radio telescopes have picked up cosmic microwave background radiation (CMBR)
What is the hubble constant?
Scientists now agree on value of 2.3 * 10^(-18) per second
What is the formula for the age of the Universe?
age of universe = 1 / hubble constant
