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Flashcards in Facts I Must Know Deck (151):

What is the diameter of the moon?



What is the distance from the Earth to the Moon?

380,000 km


What is the distance from Earth to the Sun?

150 million km


What is the diameter of the sun?

1.4 million km


What are rilles?

Valleys or trenches found on the moon


What are wrinkle ridges?

Feature found on lunar Maria, low sinuous ridges found on moon surface. They can extend up to 100km and were created when basaltic lava cooled and contracted


What are mascons?

A region of excess gravitational attraction on the moon


What is a dome?

A type of shield volcano on the moon


What is a Maria?

Large basins filled with lava that became solid, look like seas from Earth


What are sinuous?

Collapsed lava tube channels up too 5km wide


What is the chromosphere?

An irregular layer above the photosphere where the temperature rises up to 20,000 degrees Kelvin and hydrogen emits a reddish colour


What does the butterfly diagram show?

The sunspot cycle and how over 11 years they make their way from the poles to the equator then repeat again


How long does the sun rotate at the poles? And the equator?

36 at poles 25 at equator


What is the equation of time?

Eot = apparent sun - mean sun


What is the photosphere?

The luminous envelope of a star which it’s light and heat radiate


How hot is the photosphere?

5,800 degrees Kelvin


What is the corona?

An aura of plasma that surrounds stars and extends for millions of km into to atmosphere as can only be seen in a solar eclipse


In a lunar eclipse where are the sun, earth and moon located?

The Earth is in between the moon and sun


In a solar eclipse where are the moon, sun and earth located?

The moon is between the sun and Earth


What is how far north and south measured by? What about East and west?

Latitude and longitude


What is the point directly above you called?

The zenith


What are the 4 Maria on the east of the moon called?

Sea of Crises, tranquillity,fertility and serenity


Name a lunar terrae

The Apennine Mountains


Name a lunar crater

Tycho, Kepler and Copernicus


What is fusion?

The process of joining 2 or more things together to form a single entity


What is a sunspot?

A temporary phenomena on the photosphere of the sun that appear to have darker spots, are cooler, than surrounding regions. This is due to concentrations of magnetic field flux that inhibit convection


What is the solar wind?

A stream of charged particles flowing out from the sun through the solar system at speeds as high as 900km/s and at temperatures of 1 million degrees Celsius


How long does the lunar (rotational) cycle take? What about a sidereal (orbital) cycle?

One cycle is 29.5 days as the Earth has moved round the sun whilst the moon is orbiting so it has to catch up, one sidereal/full rotation of the moon, is 27.3 days


What is the diameter of the Earth?



When using the equation EOT = AST - MST to find the mean solar time (of where you are, MST = AST - EOT ) if your watch (set to GMT) is ahead of the MST calculated you are where of the prime meridian? What about if your watch is behind?

Watch is ahead you are west, behind is East


What is the closest point Earth gets to the sun in orbit called? What about the furthest?

Closest is called the Perihelion, furthest is called the Aphelion


What is the closest and furthest point the moon gets to the Earth in orbit called?

Closest is the Perigee and furthest is the Apogee


What temperature is the corona?

2 million kelvin


How long is a solar day? What about a sidereal day? What’s the difference?

Sidereal is 23 hours 56 minutes, solar is 24 hours. This is because the Earth is constantly moving around the sun so once we have moved and rotated we need to catch up by one degree which takes 1 degree (4 minutes)


What is the proper name for the northern lights?



What are aurorae caused by?

Light given off as particles from solar wind interact with atmosphere after spiralling in near the poles


What is the penumbra and umbra in moons and suns?

The umbra is the area of deepest shadow in either the centre of a sunspot or the shadow behind the Earth and a penumbra is the less dark shadow on the rim of a sunspot or the rim of the earths shadow


What is H-alpha?

A wavelength the sun gives of due to the hydrogen it emits (656 nm), this can be observed through a telescope with a fitted filter


What are the 3 types of eclipses?

Total, partial and annular


What is the plain the Earth orbits the sun called?

The ecliptic, 67 degrees from the axis of earths rotation


Which of the 2 tropics , cancer and Capricorn, appear furthest north?



How many signs of the zodiac are there? Give some examples

12, Aquarius , Capricorn , lea, cancer, Pisces, Virgo, Aries, Taurus , Gemini , Libra, Scorpio and Sagittarius


What is the zodiacal band?

The region in the night sky which the moon, planets and constellations of the zodiac are located


Where is your sign of the zodiac when you are born?

Behind the sun


What is the mean sun?

For a given time where the sun should be on average across the year isn’t the sky


Where is longitude measured from?

The prime meridian in Greenwich, London


What does circum polar mean?

It can be seen throughout the year, it is far enough north or south, such as Polaris is north


What is magnitude?

How bright a star is


What is the equation for the apparent magnitude of a star? What about the equation to figure out absolute magnitude?

Apparent magnitude is m= M-5 +5log d. Where apparent magnitude is m and absolute magnitude is M and d is distance is parsecs for both equations. Absolute magnitude formula is M=m + 5 - 5logd


What is apparent magnitude? What about absolute?

Apparent magnitude is the brightness of a star from Earth, absolute magnitude is the brightness of a star from the distance of 10 parsecs away


What is declination?

How high/below a star is from the celestial equator


What is right ascension?

How far around a star is, like longitude for stars, it is from 0 to 24 and get larger as stars move across the sky east until it starts again


What is a terrae?

A lunar feature of hills and mountains


What are the 3 main layers of the suns atmosphere?

Photosphere, chromosphere and the corona


Which is the lowest of the main 3 layers of the suns atmosphere?

The photsphere


What is the top layer of the suns atmosphere?

The corona, followed by the chromosphere then the photosphere


How thick is the photosphere?



What bright star does Orion’s belt point towards?



What do fuzzy patches in the night sky often represent?



Name one of the days that the sun crosses the celestial equator?

On the equinoxes, 21st March , 21st September


What is the temperature of sunspots? How does this differ to the surrounding photosphere?

They are about 3,800 degrees Kelvin which is 2,000 degrees Kelvin less than the photosphere


What does the temperature of the chromosphere vary between? In general we say it is the higher end of this range, which is hotter the chromosphere or the photosphere ?

The chromosphere ranges between 4500 and 20000 degrees Kelvin, this means that despite being further away from the centre of the sun the chromosphere is hotter than the photosphere


What are meteoroids?

A small piece of rock that has not entered the earths atmosphere, possibly debris from comets or asteroids


What are meteors?

Small pieces of rock/dust sized particles left behind from meteoroids that are left in a trail in the meteoroids orbit. They burn up as they meet the earths atmosphere, also known as a shooting star


Why do meteor showers occur roughly annularly on Earth?

Because at the same point in orbit (same time of year) the Earth intercepts where the meteoroids orbit was and therefore all the meteors its left behind


What are meteorites?

A rock, stony or iron, that lands on Earth, most come from asteroids and some from the moon or mars. They form an impact crater


What is a micrometeorite?

An extremely small particle that is to small to burn up in the Earths atmosphere and can be collected at the poles, places there aren’t many humans


What is a fireball?

A meteor brighter than magnitude -5


What is a comet?

A dirty ice ball that we see when it is near its perihelion(closest point to the sun in its orbit) in its orbit, as it starts to sublime (goes from solid to gases). It has 2 tails, a nucleus and a coma


What is a coma of a comet?

The nebulous envelope (large cloud) around the nucleus of a comet which is made up of gas and dust


Who discovered Pluto? When?

Clyde Tombaugh 1930


Who discovered Ceres? When?

Giuseppe Piazza 1801


How was Pluto discovered?

Tombaugh noticed irregularities in Neptune’s and Uranus’ orbit so used repeated photographs and a blink comparator to find differences in the images, he found the differences to be caused by what at the time was the ninth planet, now known as a dwarf planet


How was Ceres discovered?

Using a large reflecting telescope and Bodes law to predict where more large sized objects (dwarf planets/ planets) were Ceres was located in the asteroid belt, although at the time it was believed to be a comet as it was moving quickly


Which is the largest dwarf plant? Which one is closest to the Sun (and Earth)?

Eris is the largest, closely followed by Pluto
Ceres is the closest to the sun and earth (located in the asteroid belt)


What are the 3 main ways of detecting exoplanets?

Astrometry, radial velocity and transit


How can astrometry be used to detect exoplanets?

Astrometry (parallax) is the science of precise measurements in a stars location in the sky, it detects slight but regular wobbles in a stars position. If it is detected, regularly over a long time of observing, it is likely to be an exoplanet. This is the oldest technique used.


How can transit be used to detect exoplanets?

It measures the small drop in magnitude as the planet transits in front of the star. It is a very minute change but noticeable after lots of observation.


How can radial velocity be used to detect exoplanets?

Radial velocity, redshift, can be used to detect how colour of objects differ as they move (whether they become more stretched out or shorter). This shows whether planets are orbiting as they move towards or away from us.


Where do long period comets originate from?

The Oort Cloud


Where do short period comets originate from?

The Kuiper belt


What is the definition of a parsec?

The distance to a star which has a parallax angle of 1 arc second. It is a unit, it corresponds to the distance at which the mean radius of the earth's orbit subtends an angle of one second of arc.


What are the key “stages” in a stars evolution?

Birth/ pre main-sequence
Main sequence
Death/ Post main sequence


Which principle part of the EM spectrum do astronomers use to detect neutron stars?

Radio waves


Which principle part of the EM spectrum do astronomers use to detect black holes? How can this happen?

X rays, although nothing escapes the black hole surrounding mass before the event horizon emits a lot of high energy radiation, in the form of x rays


Why does the moon not possess an atmosphere?

It has too low a mass and therefore gravitational field strength


How are wrinkle ridges different from rille?

They are wider and longer, aren’t as deep


What is the Messier catalogue?

A catalogue of 110 astronomical objects, consisting of nebulae and star clusters, all catalogued by Charles Messier. First published in 1771, refined in 1784


Where are young stars located in a galaxy?

The disc/ spiral arms


Where is the dust found in a galaxy?

In the disc / spiral arms


Why is it not possible to map the spiral arms using visible light?

Because there is lots of dust that absorbs it


What is the diameter of the Milky Way? What about the diameter of its bulge?

30,000 pc or 30 kpc diameter
6,000 pc or 6 kpc bulge


What are PHOs and why is it important to measure there orbits?

They are Potentially hazardous objects, it is important to measure there orbits to help predict if an impact with Earth is likely


With the aid of a H alpha filter what features in the solar atmosphere will be able to be observed?

Filaments, prominences, plages, etc


What is a prominence in reference to the sun?

A large, bright features that extend out from the sun often in a loop shape, anchored from the suns photosphere and extended into the corona, where it is visible compared to the corona. They are basically the same as filaments but appear to the side of the sun so are brighter and clearly visible


Why can’t we see the corona, except is a total solar eclipse?

The corona consists of hot ionising gases, known as plasma, which does not emit much visible light so isn’t visible in comparison to the sun which has a very high luminosity


What are filaments in reference to the sun?

Dense, cool gas ejected from the photosphere that appear usually in a loop. They are basically the same as prominences but they appear over the sun so look cool and dark compared to the background star


Who discovered the CMB? How?

Penzias and Wilson, but accident when using a horn antenna and hearing static


What does WMAP stand for and what is its purpose?

Wilkinson Microwave Anisotropy Probe, to study ‘ripples’ or variations in CMB in more detail


How do astronomers use the spectrum of a star to classify its spectral type?

They use the relative strength of H, He and metals, and the relative amounts of these in a star (figured out by absorption lines) relate to the stars spectral type, O,B,A, etc. These are displayed on the HR diagram


Who was the first astronomer to explain planetary motion in terms of an inverse square law?

Issac Newton


What is the inverse square law?

Any physical law stating that a specified physical quantity or intensity is inversely proportional to the square of the distance from the source of that physical quantity


What did Newton’s law state to do with gravitational attraction and masses?

The gravitational attraction force between 2 point masses is directly proportional to the product of their masses and inversely proportional to the square of their separation distance


What does Newton’s law to do with the inverse square law have anything to do with stars? What about gravity?

The apparent magnitude of a star is inversely proportional to the square of the separation distance. For example, if you move 2 times away from a light source it will appear 1/2 squared , 1/4 , 4 times dimmer. This also means that when something is double the distance away from us (the sun) then it will have a quarter the gravity/ gravitational attraction we have. This is why planets have fixed orbits


In the Big Dipper what star do the 2 stars on the right hand side point to?



In the Big Dipper what star does the star on the left point to?



What is a planetesimal?

A minute planet, a body which could come together with many others by gravity to form a planet


What is a centaur?

Icy planetesimals located between Jupiter and Neptune They cross the orbits of one or more of the giant planets in their journey around the Sun, and interactions with these outer planets cause the orbits of Centaurs to be inherently unstable.


Between which 2 planets do most centaurs orbit the sun?

Jupiter and Neptune


Which member of the solar system was first to be discovered with the aid of a telescope? What about using photographs?

Telescope, Uranus
Photographs, Pluto


What star does Orions belts point towards?



What would a star open cluster appear like to the naked eye?

A fuzzy patch in the sky


In which month do shadow sticks give the shortest shadows at noon in the UK?



Name some sources of light pollution

Street lights, bonfires, the moon, Aurora, etc


Name some factors in the Drake Equation

Number of stars in the galaxy
Fraction of ...
Stars with planetary systems
Life forms that are intelligent
Planets capable of sustaining life
Intelligent life forms that wish to communicate
Of a planets lifetime during which civilisations can live


What is the Drake equation?

A mathematical equation that combines factors to estimate the number of planets in our galaxy that might contain intelligent life


What is the solar maximum (to do with sunspots)?

The period in the sunspot cycle (usually roughly half way through the 11 year cycle) when solar activity is highest and sunspots are most abundant


Name some charged particles in the solar wind

Ions, elctrons, protons, etc


Give the simplified definitions of conjunction and opposition

Conjunction, the sun is in the middle of 2 objects
Opposition, the Earth is in the middle of 2 objects (the sun is opposite the other object)


Why would Mars appear brighter when it is at its opposition?

It is closer to Earth and fully illuminated by the sun


What are the main parts of the tuning fork diagram?

E0, E4 (or E7, E5, E6, all elliptical), S0 (lenticular), Sa, Sb, Sc (all normal spirals), SBa, SBb, SBc (all barred spirals), and irregular


Which astronomer was the first to classify galaxies using a tuning fork diagram?

Edwin Hubble


Which gas absorbs UV radiation in the atmosphere?

Oxygen / ozone


Which gas absorbs infrared radiation in the atmosphere?

Carbon dioxide, methane, water vapour


What is the Van Allen belt? How was it discovered?

It is a belt of radiation that surrounds the Earth, it was discovered by instruments on spaceships, the Geiger counter, in 1958


How many minutes (earlier or later?) does a star culminate each night?

Each night a star usually culminates 4 minutes earlier


What is meant by culmination?

When a star reaches its highest altitude in the sky


What can we observe that shows there is a black black hole? Hint: there are 3 main things

Emissions from nearby mass (surrounding mass before the event horizon emits strong X ray radiation)
Gravitational lending (gravity bends light of neighbouring stars)
Binary systems (stars orbiting black hole and moving towards it)


Why can’t EM waves escape from a black hole?

The escape velocity is greater than the speed of light


How many constellations are there in the official international astronomy union list? Why aren’t these every single constellation?

88 constellations, it takes into account the main Greek ones but not others from other cultures, such as Indian, Chinese, etc


What constellation is Polaris located in?

Ursa Minor


Who discovered Uranus? How?

Willian Herschel 1781, he used his own telescope and noticed one of the stars was ‘different’ so started observing it more and noticed it orbits the sun


How was Neptune discovered ? By who?

It was mathematically predicted (using Newton’s law of gravitation) by Urbain Le Verner and John Adams (separately) and observed by Johann Gottfried Galle in 1846. He also noticed irregularities in Uranus’ orbit


What 4 (3 main) things did Galileo discover that showed the solar system was geocentric?

Saturn had rings
Jupiter had moons (4 main ones)
Phases of Venus (don’t see the whole cycle, only the greatest elongation, sun blocks some of it)
The moon had relief


What does greatest elongation mean? Include Western and Eastern

When an inferior planet as viewed from Earth is at its furthest position from the sun (at a tangent). When an inferior planet is visible after sunset it is near its greatest Eastern elongation. When an inferior planet is visible before sunrise it is near its greatest Western elongation


What is occulation?

An event that occurs when one object is hidden by another object that passes between it and the observer


How many major laws did Kepler come up with?



What was Keplers first law?

All planets orbit the sun in an ellipse with the sun at one focus


What was Keplers second law?

The area swept out by an orbiting planet is constant (always the same) in a certain amount of time (despite where it is in its orbit, nearer or further from the sun)


What was Keplers third law?

(Time in Earth years) squared = (Radius of orbit, on average, in AU) cubed
(T)squared = (R) cubed


What is the Hubble constant? What is its equation?

It is a value that corresponds to the expanding of the universe, it is estimated to be 71 km/s/Mpc at the moment
v = H d
Velocity = Hubble constant x distance


How to we measure the distance to distant stars outside of our galaxy?

We use standard candles such as cepheid variables and supernovas, which we know their absolute magnitude already so can work out the distance to them


What is an arc second?

1/ 3600 of a degree


In trigonometric parallax how can the distance be calculated in parsecs using the parallax angle?

Distance = 1/parallax angle


How would you go about working out the Hubble constant from the graph Edwin Hubble plotted? (Recessional velocity against distance away in Mpc)

You would draw 3 lines of best fit, middle, shallowest and steepest that seem reasonable (on the graph of the Virgo Cluster Edwin Hubble plotted) then figure out the gradient of these (change in y axis / change in x axis). This gives you an estimate for the Hubble constant


What is the equation for redshift? Hint: using absorption lines

(Observed wavelength - true wavelength)/ true wavelength
= velocity of object / speed of light


What is the speed of light?

3.0 x 10 to the 8 m/s


What shape is the Earth?

An oblate spheroid, it is not perfectly spherical


What is an asteroid?

A body that orbits the sun in a stable orbit


What is chromatic aberration?

The effect when wavelengths are refracted at slightly different angles which may cause in a failure to focus


What did Copernicus do?

Suggest the theory the solar system was heliocentric