(A) Topic 5,6,7,8 wrong Flashcards
Explain why we see inferior planets best at the maximum angle of elongation
Inferior planets can’t be seen in opposition
Explain the term elongation
Angle at which we see an inferior planet
What happens during an occultation?
One celestial body obscures and covers the other, blocking its light
When does an opposition occur?
When a planet is opposite the Earth from the Sun
Describe the main features of a meteor shower
- can last several hours
- happens when the Earth passes through a dusty meteoroid stream in the wake of a comet
Define the term meteor
Fragments of dust from comets or asteroids that Earth smashes into whilst orbiting the sun
What is a planetary track?
Path a planet makes on a star map
What is inclination?
Angle between the orbital plane of the object and the plane of the ecliptic
What is the Earth’s inclination?
23.5
Devise an experiment to observe the Sun using a paper or card
- Cut out a small hole in a card paper
- Find a smooth surface
- Angle the hole so the sun can be seen through it
- Look at the Sun (through the projection)
Why are red torches used by astronomers?
To ensure they don’t ruin their adapted eye
How does the milky way look from Earth as seen with the naked eye?
furry light irregular column
How can we find an observer’s latitude using NCP?
Altitude of NCP = Latitude of Observer
Explain why the sky appears to move from east to west when we know the Earth rotates
The apparent motion of the sky- we think we are stationary, whereas in reality, we may be standing still but the Earth is still moving
Define circumpolar stars
Stars that never set below the horizon: can be seen from one location throughout the year
What two things affect how long we can view the constellations?
- Earth’s titled axis
- 23.5 degree angle to the ecliptic
What formula determines the circumpolarity of stars?
declination >/ (90 - latitude of observers)
observer’s latitude +/- co-declination of stars
declination=co-latitude
Define the term upper culmination
Star at its highest point
Define the term lower culmination
Star at its lowest point
What other word can be used instead of culmination?
transit
What is co-declination?
Distance between NCP and stars
What is the formula for co-declination?
Co-declination = 90 degrees - declination
When does the upper culmination take place?
Takes place when right ascension = LST
Define cardinal point
Compass point in space
Define circumpolarity
When a star never sets below the horizon from a certain latitude
Define culmination
When a star (or another body) reaches the observer meridian
Define the term meridian
Imaginary line between north and south pole
What is an hour angle?
Angle between the meridian of the observer and star’s meridian line
What is the formula for the hour angle?
local sidereal time - RA of stars
Define the term Altitude
How high an object is above the horizon
Define the term Azimuth
How far eastwards an object is in degrees
When can we work out the Sun’s altitude and use which equation?
When the sun is at its highest point in daytime
sun altitude = sun declination + (90 degrees - latitude of observer)
Describe other visibility problem that affect astronomers
- Rising and setting of sun + thicker atmosphere
- Saharan dust + volcanic ash in Upper Earth atmosphere
- weather conditions
- landscape
- other celestial bodies
Why are many of the constellations based on Greek Mythology?
Ptolemy, a Greek astronomer was responsible for scripting all the constellations
What are star maps and charts?
Map that gives positions and magnitudes of stars
What is a planisphere?
Rotating star locator
What is the Plough used to find?
Polaris and Arcturus
What does Orion point to?
Sirius the brightest star
What does the square of Pegasus point?
Andromeda Galaxy
Define the term open cluster
Group of stars close to each other but form no specific symmetry
Define the term globular cluster
Groups of stars which are spherical shaped with more stars closer to the nucleus
Define the term nebulae
Place where stars are born + where they die
Define the term supernovae
The large explosion which takes place after the death of a star
Define the term aurorae
The solar wind interacts with the atmosphere which produces light and colour displays in the sky
What are binary stars?
Stars that orbit around a common center - share a gravitational bond
What is another name for binary stars?
double stars
What are optical double stars?
Stars that look close together from Earth but are actually not related to each other
How do we know the difference between a star and a planet when viewed from Earth without a telescope?
Planets are typically brighter and don’t tend to oscillate
Define the term asterism
Pattern of stars that may or may not be related to a constellation.
Define epicycles
Each planet revolves uniformly along a circular path, which revolves around the earth in a larger circular path
Who came up with the idea of epicycles?
Ptolemy
Why were epicycles created?
To justify the geocentric theory by solving the inability to explain the imperfect motion of heavenly bodies
What is the inverse proportion law?
Every body in the Universe attracts another with a force that is directly proportional to the product of their masses and inversely proportional to the square of their distance
How is the inverse proportion law related to Kepler’s third law?
As an object orbits nearer in an elliptical orbit, there must be an increase in gravitational force between them at that point
What is Kepler’s third law?
The square of the orbital period of a planet (t) is proportional to the cube of its mean distance (r) from the sun
What is the role of mass in Kepler’s third law?
Gravitational attraction is dependent on the mass, therefore mass must accounted for
What is an orbit?
The celestial path of body in space around another body
What is Kepler’s first law?
Planets move in elliptical orbits around the sun, with the sun at one focus
What is Kepler’s second law?
An imaginary line from the Sun to a planet sweeps out equal areas in equal intervals of time
What is an ellipse?
Oval shape with two foci
Who introduced the Geo-heliocentric model?
Tycho-Brahe
What did the geo-heliocentric model suggest?
Moon and the Sun orbited Earth but everything else orbited the Sun
What did Kepler discover using Tycho’s observations?
Planets didn’t follow circular orbits but elliptical
