Exploring The Solar System Flashcards
(31 cards)
Describe the structure of comets
They have a ~10km nucleus of rock and ice, which is enveloped by a coma of rarified gases and dust when it approaches the sun. Their tails can be millions of kilometres long, and become more visible the closer they are to the sun. Their tails always point away from the sun. The ion tail is long, straight and mostly blue consisting of ions excited by the charged particles in the solar wind. The dust tail is broader and more curved, and is caused by solar radiation pushing reflecting particles out of the nucleus and into the sunlight.
Describe the orbit and origin of short - period comets
Short period comets have an orbital period of less than 200y, and originate in the Kuiper Belt. Some even have elliptical orbits
Describe the orbit and origin of long period comets
Long period comets have orbital periods of more than 200 years, and originate in the Oort Cloud. Most have inclined and unpredictable orbits.
Describe the location and nature of the outermost parts of the solar system
The Kuiper Belt is a region of icy objects including frozen gases, rock, ice and dwarf planets
The Oort Cloud is a distribution of icy bodies at the border of the solar system.
The heliosphere is the field of influence of the sun, and at its boundary is the heliopause, a volatile region of space.
What is the atmospheric composition of the planets
Mercury has little atmosphere
Venus’ is 96 % CO2, as well as 3% N and traces of SO2
Earth’s is 78% N, 21%O, and traces of CO2 and H20
Mars’ is 95% CO2, 3% N, and 1.5% Ar
Jupiter’s is 90% H, 10% He, traces of CH4 and NH3
Saturn is 96% H, 3% He, traces of CH4
Uranus is 83% H, 15% He, and 2% CH4
Neptune is 80% H, 19% He, and 1% CH4
What is the core accretion theory for the formation of gas giants?
Past the frost line of ~5AU, compounds like water and CO2 are solid, so can clump together to form solid cores. This then has enough mass to gravitationally attract gases like hydrogen and helium to form the gas giant. This is evidenced by gas giants having solid cores, and matches to other star systems. One limitation is that it doesn’t explain how gas giants form so quickly.
What is the origin and structure or meteoroids and meteorites?
Meteoroids are particles of dust, rocks or chunks or ice orbiting the sun. They enter Earths atmosphere often and at high speeds. The air resistance causes lots of thermal energy, heating small particles and causing them to glow. This streak of light in the sky is known as a meteor. Meteor showers occur when Earth passes through the meteroid stream in a comets’ wake.
What is the Disk Instability theory for the formation of gas giants
Unstable parts of the solar nebula collapsed under their own gravity, forming the gas giants without a solid core first. This is evidenced by the very large gas giants seen in other star systems, and also works faster than core accretion. One limitation is that it isn’t likely for our solar system due to the stability of our nebula.
How do most bodies orbit the sun?
In, or close to, a plane called the ecliptic
What are the main theories for the origin of water on Earth
- Volcanic outgassing - internal source. When early volcanoes erupted, they released lots of water vapour, which condensed when the Earth cooled, and fell as rain. Evidence - 1)Water vapour is release in volcanic eruptions today. 2) This matches the composition of Earth’s early atmosphere.
- Comet and asteroid impacts- external source. In Earths early life, it was bombarded with icy comets and water rush asteroids, which then melted giving Earth water. Evidence- 1) Some asteroids and comets contain water. 2) The type of hydrogen (deuterium) in our oceans matches that of asteroids.
Describe the use of the transit of Venus to determine the absolute size of the solar system
As Venus transits the Sun, observers at different latitudes would see Venus trace different paths across the sun. By using the difference in these chords and simple triangulation, astronomers could work out Earth’s distance from Venus and so the Sun. The AU was calculated to 2.5% of its true value
How is the human eye limited in astronomical observations?
It’s small aperture and limited sensitivity in low light
What does the objective element of a telescope do?
Captures as much Light as possible and focuses it into a small bright image so that it can be magnified by the eyepiece
What lenses and mirrors can be use to collect and focus light
Convex lenses and concave mirrors
How to make a simple telescope with an objective and an eyepiece.
Place the objective and the eyepiece in line with each other, with their focal points as close together as possible. The objective should have a long focal length and the eyepiece should have a short focal, length. The image would be seen inverted by this is acceptable in astronomy.
How does a telescope’s “light grasp” and aperture relate to the objective element
In is directly proportional to the area of the objective, element, so therefore the square of the diameter
The aperture is the diameter of the objective elements.
What is the field of view?
The circle of sky visible through the eyepiece, measured in degrees and the arcmin.
How does a telescope’s resolution link to the diameter of the objective element and the wavelength of light?
It is proportional to the diameter of the objective element and reduced by observing at a longer wavelength
Magnification formula
Mag = Fo/Fe where Fo is the focal length of the objective element and Fe is the focal length of the eyepiece.
What is focal length?
The distance between the lens/mirror and the focal point.
What was the importance of Galileo’s observations in establishing a heliocentric model?
- He observed 4 moons orbiting Jupiter, which showed that not everything orbited Earth
- He observed the phases of Venus, which is only possible if Venus orbited then Sun.
What is the difference between reflectors and refractors?
Reflectors use a parabolic concave mirror to capture and focus light
Refractors use a convex lens to capture and focus light
What are the advantages of reflecting telescopes?
- They do not experience chromatic aberration - lenses focusing different wavelengths at different points, causing blurred imagers
- They have very long focal lengths (of the objective) which increases magnification
- Large aperture lenses can be difficult to make and fragile, so mirrors are easier
- Multiple mirrors can be used to collect more light
