Astronomical Concepts – Week 4

This week’s main topic was light.

James Maxwell

James Maxwell was a Scottish scientist who lived from 1831 to 1879. He is well known for the research he did on electromagnetism and light, building on the work of Michael Faraday. He produced a set of equations that explain the properties of magnetic and electric fields which helped to show that light was an electromagnetic wave. He was able to bring together well established laws of electricity and magnetism and with Faraday’s law they could imply that any disturbance in the electric and magnetic fields will travel out together in space at the speed of light.

He also described Saturn’s rings as numerous small particles, and this theory was proved later on in the 20th century by a space probe.

Einstein’s Photoelectric experiment

Einstein’s experiment showed that packets of light, called photons, contained a fixed amount of energy that depends on the light’s frequency. When a metal plate is exposed to light electrons are expelled. This is the photoelectric effect. The effect was discovered by German scientist Heinrich Hertz in 1887. His observations showed there was an interaction between light and matter. But Albert Einstein was needed to explain the theory further in 1905, his theory of light. Einstein said that light is a particle, called a photon. Einstein was awarded the Nobel Prize in physics in 1921 for his experiment.

Spectroscopy

Spectroscopy is a technique used to measure the light that is emitted or absorbed or scattered by materials. It breaks light into its component parts and this information can be used to identify and quantify those materials.

spect-prism-sm

When light is absorbed or reflected by materials not all light behaves the same way. Only certain wavelengths of light are absorbed other get reflected. When you seperate the light that is passing through a sample you end up with an emission spectrum or absorption line.

An emission spectrum in the visible light range may look like this.

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A spectrum like this would be created when material is given extra energy and that extra energy is later emitted as light energy.

An absorption spectrum would look like this.

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A spectrum like this is created when light is passed through a gas or liquid or strikes a solid. Certain wavelengths of light will be absorbed by the material and later emitted in random directions. Most wavelengths will pass through the material without being absorbed. sun_spectrum

The image above shows a spectrum of our sun. From this spectra astronomers can tell what elements the sun is made from, for example hydrogen and helium. It is like a rainbow with holes, the holes are coming from the absorption of energy at a particular wavelength, at a particular colour, by the atoms in the cloud. This goes back to the energy levels of the atom, of only taking energy at very particular energies, as electrons move from one excited state to another excited state. So what you’re seeing is the absorption of photons by atoms. When energy is absorbed you are seeing the energy raising the energy level of an electron. So, we see the rainbow because the inside of the sun is hot and it emits a continuous thermal spectrum. The atoms in the outer layer of the sun absorb some of the energy and use it to promote electrons from a low energy level to a high energy level.

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Astronomers also take pictures of light, usually through a filter. Astronomers want to see what the light looks like in red light or green light.

Astronomers also do timing with light, which means to measure the brightness or phase changes as things happen in time.

The combination of spectroscopy, imaging and timing can tell us all kinds of information from the thing we are looking at. We can tell hoe fast something is rotating, if it is moving towards or away from us, temperature, density and composition. Light is our spaceship, we can’t travel to stars and planets light years away but light does travel to us, it is the only way to get the information we need.

Doppler effect

Light waves from a moving source experience either a red shift or a blue shift in the lights frequency. A light source moving away from a stationary observer causes a shift towards the red end of the light spectrum, called a red shift. When the light source moves towards an observer the frequency shifts towards the blue end of the spectrum.

em_spectrum

Why is the sky blue?

The sky is blue because atoms in our atmosphere scatter blue light more than they scatter red light. When we look towards the sun at sunset we see red and orange because the blue light has been scattered away from the line of sight. Blue is scattered more because it travels as small and short waves.

That’s enough about light, next week is all about the sun.

Astronomy at Questacon in Canberra

Questacon in Canberra has a pretty cool section on space and astronomy. Check out the pictures I took in the gallery below.

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A few of the highlights from this exhibition.

NASA WMAP

  • WMAP is the Wilkinson Microwave Anisotropy Probe
  • It launched on June 30, 2001
  • Has mapped fluctuations in the cosmic microwave background (CMB) radiation (the oldest light in the universe) and has produced a full map view of the microwave sky
  • Has determined the universe to be 13.77 billion years old
  • Determined the curvature of space to within 0.4% of flat Euclidean
  • Found that the universe is 24% dark matter
  • Found that dark energy makes 71.4% of the universe, causing the expansion rate of the universe to speed up

Morgan Keenan System (MKK)

  • Classification of stars based on temperature
  • Categories divided into Roman numerals, with sub-categories and classes
  • To completely describe a star the MK luminosity class is appended to the original Harvard classification for the star
  • The Harvard Spectral Classification assigns each star a spectral type with is further divided into 10 sub-classes depending on the absorption features present in the spectrum. E,g, our Sun has a temperature of 5,700 Kelvin and is classified as a G2 star
  • Our Sun is a main sequence star G2 and the full classification is G2V

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Types of orbit

  • The Moon does not orbit the Earth, the Moon and Earth orbit each other around their common centre of mass. The common centre of mass is inside the Earth
  • Kepler showed the orbits of the planets were ellipses with the Sun at one foci
  • Newton showed there were other types of orbit
  • Elliptical and circular orbits are both bound orbits
  • Parabolic and hyperbolic are unbound orbits
  • Comets and asteroids typically have hyperbolic or parabolic orbits, they zip around the Sun once and they go off never to be seen again because they do not have gravitationally bound orbits
  • Look at the circular cone above, how you slice the cone determines what kind of geometric cross-section you get – horizontal makes a circle, an angle creates an ellipse, increase the angle and get to the bottom of the cone you get a parabolic and cut the cone vertically you get a hyperbola
  • So 4 different types of orbits

Additional…

  • Newton’s laws of gravity showed that Kepler’s first 2 laws, ellipses and equal area in equal time are a consequence of the conservation of angular momentum (Mass x speed x distance = constant)
  • At perihelion the distance to the Sun is smaller so to keep the mass times the speed times the distance the same the conservation of angular momentum the plane must move faster
  • At aphelion, further away from the Sun, conversely the speed must decrease
  • P squared is a cubed (P^2 = a^3)
  • P is the period the time it takes to go around and the semi-major axis of a of the ellipse, a is the average orbital distance

Thank you F.X. Times at Arizona State University for some of the information included.

Exploring the Heavens – Week 2

The focus of this week’s class was Celestial Rhythms and the development of the constellations.

We started the class upstairs in the observatory and outside on the balcony with Paul describing our session and then identifying a few of the objects on display in the night sky, including a crescent Moon. Paul described how the Moon is moving around the Earth and how the position of the Sun in relation to the Earth and Moon affects the different phases of the Moon. He explained that next week the moon will have moved across the sky in counter-clockwise direction and showed us approximately where it would be.

We then headed downstairs and outside to a large model of the solar system painted on the ground, as seen in the image below during the daytime. We sat around the model and Paul described the motion of the Earth and other planets around the Sun. This demonstration was a great way to visualise our solar system and how various planets move in relation to the Sun. Paul also described how our view on Earth is affected by the Sun and how the Sun blocks various stars at certain parts of the year.

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This session was about the importance of understanding how the sky moves during a night and throughout a whole year.

“The sky is on a continual march that presents us with different constellations at different times of night, and different times of year.”

After our outside demonstration and further observing of the night sky we moved back inside for a much needed tea break and to escape the chilly Sydney evening weather, should have taken a jacket!

After our break we headed downstairs to the 3D theatre and enjoyed another presentation by Paul. The focus of the inside session was to demonstrate the motion of the Earth travelling around the Sun and its rotation on its own axis, what causes the seasons as well as examine closely what makes a day and a year, which is not quite what we thought.

I learnt so much over our 2 and a half hour class. As we spin around our axis once per day we actually move about 1 degree around the Sun. We rotate and orbit in a counterclockwise direction and in a year there are 365.25 days. So, the Earth, rotating at 1360 km/h, must spin on its own axis 360 + 1 degrees to have the Sun reappear in the same position. A day as we know it is 24 hours long, this is actually a solar day as our clocks have been tuned to the combined motion of our rotation and orbit around the Sun.

A different kind of day is called a sidereal day, which is 23 hours 56 minutes and 4 seconds long. This is the time astronomers use to predict the location of stars on the night sky. All of this means that we will see a slightly different sky each night.

We all know we have four seasons on Earth and the seasons are caused by our axis of rotation being tilted by 23.5 degrees to the plane of our orbit, called the ecliptic. The axis points in the same direction as we orbit the Sun, and this is what causes the seasons and the variation in the length of a day throughout the year. Paul gave us examples of the equinoxes and the solstices. The equinoxes occur approx. half way between the solstices on March 21 and 21 September, the solstices on 21 June and 21 December. In June the axis is pointed towards the Sun so the northern hemisphere will see the Sun high in the sky and will receive many hours of sunbathed daylight. In the southern hemisphere people will see the Sun much lower in the sky and will experience less daylight compared to the northern hemisphere. The reverse is true for December. At equinox the day and night are the same length for both hemispheres – equal.

AxialTiltObliquity.png

“We spend our days and nights humbly on planet Earth. We suffer from the illusion that we feel stationary on the surface of the Earth and that the Sun and stars seem to revolve around us.”

Infant, our axis is slowly precessing, like a spinning top over a period of 26,000 years. This means that the celestial poles on the celestial sphere sweep out a circle every 26,000 years carrying our coordinate system of the stars with it. This small drift was actually measured by Hipparchus around 140 BC. Paul has recommended we purchase a planisphere, seen below, a dynamic map that can portray the night sky for a given location at any time of night throughout the year. These are only designed for one latitude and do not contain much information.

There are 88 constellations in the night sky. Each constellation is an area of the sky and are recognised and classified by the International Astronomy Union (IAU). We learnt heaps about the constellations:

  • Each culture developed its own constellations
  • Constellations often symbolised mythological creatures
  • Constellations are a reminder of a lesson or a seasonal event
  • Many originated in Babylonia
  • The Greeks adopted many and developed their own mythologies to explain them
  • The constellations the Sun passes through along the ecliptic are called the zodiacs
  • There are actually 13 zodiacs, including Ophiuchus, although the Sun does not spend too much time in this sign
  • The Babylonians set up the zodiacs and their counting system was based on base 12, so they stuck with just the 12 constellations and that is why we have 12 hours of day, 12 hours of night and 12 months a year
  • The Sun now spends more time in Ophiuchus than in some neighbouring constellations

I am a Pisces and here is my constellation from the IAU (http://www.iau.org/static/public/constellations/gif/PSC.gif)

PSC.gif

A few facts about Pisces:

  • One of the most ancient constellations
  • Depicts 2 fishes swimming in opposite directions with their tails joined
  • In mythology the two fishes represent Aphrodite (Venus) and Eros (Cupid)
  • One day they hide to hide in rushes along the Euphrates to escape a monster called Typhon. The two fishes swam away to safety
  • Pisces is watery and faint, it lies in an undistinguished part of the sky
  • Its brightest stars are only magnitude 4
  • One way to locate Pisces is by reference to the square of Pegasus
  • The Sun passes through Pisces between Feb 19 and March 20
  • The 12th sign
  • Famous Pisces include Steph Curry (Mar 14), Einstein (Mar 14), Steve Jobs (Feb 24), Daniel Craig (Mar 2), Jon Hamm (Mar 10)

Pisces stars

Pisces

Eta Piscium is the brightest star at 316x that of the Sun. It is 294 light years from Earth and is a G class bright giant star.

Pisces contains a Messier object called Messier 74, a spiral galaxy located between the stars alpha Arietis and eta Piscium. It is also known as the Phantom Galaxy, shown below.

M74

Messier-74

The grand-design spiral galaxy Messier 74 as photographed by the Hubble Space Telescope in 2007. Image: NASA, ESA, and the Hubble Heritage (STScI/AURA)-ESA/Hubble Collaboration. Acknowledgment: R. Chandar (University of Toledo) and J. Miller (University of Michigan)

The red areas indicate pockets of hydrogen gas. They glow due to the radiation from hot, young stars. Astronomers call these areas H2 regions. The brighter stars are not part of the galaxy and are actually located a lot nearer to us. The galaxy appears face-on and is approx. 30 million light years from Earth. It is roughly the same size as the Milky Way with a diameter of 95,000 light years. Two supernovae have been seen exploding in recent years in this galaxy. It contains about 100 billion stars. It is not easy to observe due to low surface brightness and requires clear skies. The only other object with a lower surface brightness is M101, the Pinwheel Galaxy, shown below.

M101

M101-HST-GendlerS.jpg

The Phantom is an example of a grand design spiral galaxy with 2 clearly defined arms which extend for about 1,000 light years. The arms contain clusters of young blue stars and star forming nebulae. It is receding at a speed of 793 km/s.

Zoom into M74:

M74 was first observed in 1780 by French astronomer Pierre Méchain who told his good friend Charles Messier about it, Charles added it to his famous catalogue.

More about M74 here.

Thank you Hubble!

Exploring the Heavens – Week 1

On Tuesday 3 May I attended the first week of my new course on astronomy at Sydney Observatory. The course is titled ‘Exploring the Heavens’ and is led by Dr Paul Payne. The structure of the course is as follows:

  1. History of Astronomy
  2. Celestial rhythms
  3. The solar system
  4. The stars
  5. Telescopes

So the course started with Dr Payne’s two hour version of the history of astronomy in the Sydney Observatory 3D theatre. Some of the main figures covered included:

  • Aristotle (384 – 322 BC)
  • Claudius Ptolemy (~140 BC)
  • Nicolas Copernicus (1473 – 1543)
  • Tycho Brahe (1546 – 1601)
  • Johannes Kepler (1571 – 1630)
  • Giordano Bruno (1547 – 1600)
  • Galileo Galilee (1564 – 1642)
  • Isaac Newton (1642 – 1727)
  • Edmund Halley (1656 – 1742)
  • Charles Messier (1730 – 1817)
  • William Herschel (1738 – 1822)
  • James Bradley (1693 – 1762)
  • Friedrich Bessel (1784 – 1846)
  • John Adams (1819 – 1892)
  • Jean Le Verrier (1811 – 1877)
  • Albert Einstein (1879 – 1955)

Dr Payne kept the pace moving pretty quickly to cover all of these historical and important figures and more about the ancient Greeks, Romans, Babylonians, Renaissance as well as advancements in mathematics, engineering and technology.

Dr Payne also used his homemade 3D graphics to help demonstrate certain themes and concepts, including retrograde motion of planets, constellations and the movement of the moon and planets from Earth’s point of view. The graphics were great and they certainly enhanced the presentation putting us firmly in the cosmic realms.

I was surprised at how important astrology was in ancient times and how seriously it was taken to predict future events. People were also very superstitous and heavenly objects played an important role in how people lived their lives, including Roman emperors. It is also amazing at how much people knew about the solar system hundreds and thousands of years ago without even the aid of a telescope.

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As well as learning about the history of astronomy Dr Payne gave us a tour of the night sky on what was a beautiful and clear evening in Sydney. Some of the notable objects we spotted were: Mars, Jupiter, Alpha Centauri, Sirius, Betelgeuse, as well as some notable constellations.

Jupiter-planet

The final part of the evening involved us moving to the south dome of the observatory to use the telescope to view the night sky. We were lucky enough that the sky was clear from clouds and we were treated to an amazing view of Jupiter and the Galilean moons Ganymede, Io, Europa and Callisto.

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Image of the telescope in the south dome of Sydney Observatory.

This telescope is the oldest working one in Australia and was built in 1874 by Hugo Schroder in Hamburg, Germany. An interesting article about the telescope can be found here.

This was actually my first time looking through a telescope and the view did not disappoint. I was amazed by how clear Jupiter appeared, being able to clearly identify its white zones and brown belts, both of which are cloud systems with winds that blow in opposite directions. The Galilean moons, although tiny, were very bright and also so clear to see. This is exactly what I had been hoping to see and has just added more fuel to my growing love for astronomy.

Looking forward to week 2!

Introduction to Solar Systems Astronomy Design Project

Earth’s twin: No oxygen, no water, scorching temperatures and a runaway greenhouse effect. What else do we know about our closest neighbour, Venus?

Arizona State University’s AST111

Introduction to Solar System Astronomy

Design Project evidence

Learning objective

Describe the origins, structure, contents, and evolution of our solar system.

Project goal

“Venus favours the bold” – Ovid

Describe the planet Venus, how it became so hot and examine the scientific impact resulting from the many missions to Venus, otherwise known as Freya’s planet.

venus.jpg

Image courtesy of http://www.space.com/images/i/000/044/599/original/venus-surface-magellan-spacecraft.jpg

Venus fact file

  • Second planet from the Sun, 67 million miles apart (0.72 AU)
  • Second brightest object in the night sky, behind the Moon. Venus’ clouds are highly reflective, making it shine bright in the night sky
  • Named after the Roman Goddess of love and beauty
  • Has no moons or rings
  • Spins very slowly in a clockwise direction (retrograde rotation), backwards to the other planets in the solar system. Backwards spin is probably due to a cosmic collision early in its history
  • Venus is very nearly a perfect sphere, thanks slow rotation!
  • 80% size of Earth, similar mass and both rocky worlds
  • Hottest world in our system, 480 degrees celsius on the surface, hot enough to melt lead
  • Runaway greenhouse effect. It is thought Venus used to have oceans but due to extra heat from the Sun these oceans evaporated and the water vapour trapped more heat in the atmosphere warming the planet further, trapping more heat until the oceans were no more
  • Has a cratered and volcanic surface
  • 1 year on Venus is equal to 225 Earth days, and 1 day on Venus lasts 243 Earth days – making a day last longer than a year on Venus
  • Atmosphere consists mainly of carbon dioxide (~96%), Nitrogen (~4%)
  • More than 40 spacecraft have explored Venus

Venus in culture

The Venus de Milo is ancient Greek statue created between 130 and 100 BC. It depicts Aphrodite, the Greek goddess of love and beauty, known as Venus to the Romans. It is on permanent display at the Louvre in Paris.

Venus_de_Milo_Louvre_Ma399_n2

Men are from Mars, Women are from Venus. This book published in 1992 has sold over 50 million copies around the world. It states that common relationship problems between men and women are a result of fundamental psychological differences between the sexes because they are from ‘different planets’.

menarefrommars

Beyond Apollo – Barry M. Malzberg. A novel about a 2 man mission to Venus which is aborted and when the mission returns to Earth the captain is missing and the other man cannot explain what happened to him. The novel tries to get to the bottom of this mystery and overall it represents humanity’s incompetence at the enormity of space exploration. The book is listed as in development on IMDb so look out for a motion picture soon. (http://www.imdb.com/title/tt2403823/?ref_=fn_al_tt_1)

beyond apollo

For a twin planet, Venus is very different to Earth

4 billion years ago Venus was thought to be a lot like Earth, with evidence pointing towards Venus supporting bodies of water (H2O), perhaps even oceans. However, 4 billion years ago the Sun was less powerful that it is today and was only 70% as bright. Over time as the Sun became much hotter any bodies of water on Venus evaporated and water vapour was driven into the atmosphere, causing major greenhouse changes. Water vapour can trap heat, acting as a blanket around a body. At the top of the Venus atmosphere water molecules were split into hydrogen (H) and oxygen (O), under the full intensity of sunlight and ultraviolet rays. Much of the hydrogen (H) escaped into space whilst the oxygen (O) combined with carbon to form carbon dioxide (CO2), a great absorber of heat. Oxygen also bound with sulphur (S) and created sulphur dioxide (SO2) which created droplets of sulphuric acid (H2SO4). Could this runaway greenhouse effect ever happen here on Earth?

Venus atmosphere

The Venus atmosphere is extremely dense and hot. It is mainly composed of carbon dioxide with clouds of sulphuric acid, which gives Venus its yellow colour. It does rain sulphuric acid, but drops never reach the surface due to the extreme heat. The thick atmosphere traps heat and the tremendous amount of carbon dioxide adds to the runaway greenhouse effect on the planet. The weight of the thick, dense atmosphere creates enormous pressure on the surface of 90 times heavier than standing on the surface of Earth. The equivalent pressure on Earth is about 1 km beneath the surface of an ocean. The atmosphere is slowly being stripped away by the solar wind, a million tonne per second stream of material coming from the Sun. About 300 kg of the atmosphere is being lost every day from Venus.

Internal structure

Venus has an iron core approx. 3000 km in radius. This is similar to all terrestrial planets because of the effects of gravity, causing heavier material to sink to the middle of the planet whilst lighter material floated to the top. Venus does not have a magnetic field as it rotates too slowly.

InteriorOfVenus

Image courtesy http://astronomy.nmsu.edu/tharriso/ast105/InteriorOfVenus.png

Missions to Freya

Over 40 missions have explored Venus. The first craft to land on the surface was Venera 7 and was actually the first craft to land on another planet, after 15 failed missions. This Soviet mission in 1970 successfully landed on the surface and was able to send back 23 minutes worth of data, including a surface temperature reading of 475 degrees celsius and a pressure reading of 90. Not a very pleasant place to be!

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Image courtesy http://solarsystem.nasa.gov/missions/venera_07/galleries

There is presently an active Venus mission called Akatsuki. The goal of the mission is to study weather patterns, confirm the presence of lightning in thick clouds and search for signs of active volcanism. This mission suffered a huge blow early on in its mission when thrusters failed to fire and the craft ended up on a journey around the Sun rather than Venus. Over the next five years JAXA (the Japanese Space Agency) tested the various thrusters and came up with a strategy to fix the craft and send it back to Venus. To do this they dumped fuel from the broken thrusters and used the secondary control thrusters to orient the probe towards Venus. This happened in December of 2015 and the probe entered the orbit of Venus as originally planned.

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Image courtesy http://solarsystem.nasa.gov/galleries/space-tourism-posters

Magellan – mapping the surface of Venus. Launched in 1989 by NASA, the Magellan deep space orbiter was designed to map the surface of Venus down to a resolution of 120 to 300 metres. On 15 September 1990 the craft began to send high resolution radar images of the surface  clearly showing signs of vulcanism, tectonic movement, surface winds, lava channels and pancake shaped domes. During its first cycle it mapped 83.7% of the surface returning 1200 GB of data, an incredible amount at that time. After the second cycle it had mapped 96% of the surface and the third mapped 98%. Contact with the probe was lost on 12 October 1994 after it had plunged into the atmosphere to collect further aerodynamic data.

Magellan findings:

  • 85% of the surface is covered with volcanic flows
  • Complete lack of water
  • Extremely slow erosion process
  • Surface features persist for hundreds of millions of years

ESA goes express to Venus in 2005! The ESA sent the Venus Express to Venus in 2005 with the primary goal of studying the atmosphere. This was the ESA’s first mission to Venus and it was named Express due to the quick time the mission took to prepare and execute.

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Image courtesy http://www.esa.int/spaceinimages/Images/2007/11/Artist_s_concept_of_lightning_on_Venus

The magnetometer (MAG) on board ESA’s Venus Express detected wave signals that show evidence of lightning in the atmosphere.

Major achievements of Venus Express include:

  • Discovery of a shape-shifting southern solar vortex. It can take almost any shape indicating complex weather patterns due to centre of vortex being offset to geographical pole
  • Evidence of recent volcanism, perhaps in the last few thousand to ten thousand years

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Double volcano on Venus. Image courtesy http://astronomy.nmsu.edu/tharriso/ast105/Ast105week08.html

A ten-fold increase in sulphur dioxide in the atmosphere has led scientists to question whether volcanos are still active today.

  • Venus’ rotation is slowing down, found by comparing data collected by the Magellan mission. Features monitored by Express could only be lined up with Magellan if the length of a day on Venus is on average 6.5 minutes longer than when Magellan tracked the same features
  • Discovery of a cold area 125 km above the surface where snow or ice could exist. The temperature of -175 degrees celsius means the carbon dioxide can freeze
  • Detection of a thin ozone layer approx. 90 to 120 km above the surface, far higher than on Earth where ozone exists at 15 to 50 km above the surface
  • Water loss due to splitting of water molecules in upper atmosphere by ultraviolet radiation from the Sun. The process creates two hydrogen atoms and one oxygen atom which are carried into space by the solar wind. Venus does not generate a magnetic field which can protect its atmosphere from the solar wind
  • Discovered mean wind speed of 400 km/h, an increase of 100 km/h over the 8 year mission

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Pancake domes on Venus. Image courtesy http://astronomy.nmsu.edu/tharriso/ast105/Ast105week08.html

Images from the surface – Venera 13. On 1 March 1982 Venera 13, a Soviet mission, set down on the surface of Venus and began relaying data back to Earth. It was able to transmit data for 127 minutes, far longer than the expected 32 minutes before the craft was crushed and melted by the extreme pressure and heat on the surface of Venus. It successfully relayed the first colour pictures of the surface of Venus, something previous missions had failed to do. It sent 8 panoramas showing fields of orange-brown rocks and loose soil. Soil analysis showed soil similar to terrestrial leucitic basalt with high potassium content.

Venera13Camera2

Image above shows Venus surface.

Future Venus missions?

1. The clockwork Venus rover. The solution to Venus landers not lasting longer than 2 hours could be a clockwork lander with no electronics. To send messages back home it would record data on a phonograph and then loft it on a balloon to rendezvous with a spacecraft overhead. (https://www.newscientist.com/article/mg23030693-600-our-top-5-wacky-nasa-missions-that-might-just-happen/)

The phonograph is a machine invented by Thomas Edison in 1877. It is a machine for recording sound on tinfoil coated cylinders. It has 2 needles, one for recording and one for playback. It is incredible to think that over one-hundred year old technology could be used to explore the solar system today.

2. Can sound help us detect ‘earthquakes’ on Venus? (http://www.astrobio.net/topic/solar-system/venus/can-sound-help-us-detect-earthquakes-on-venus/)

Researchers are planning to deploy an array of balloons in the atmosphere of Venus that could detect seismic activity on the surface using sound. A team of experts at the Keck Institute for Space Studies began thinking of ways to use infrasonic observations to get a better look at the geological dynamics of Venus. If we can get a better idea of the seismic activity on the planet this can tell us more about the history of the planet and its interior.

Escape velocity of Venus

During the course the mathematical labs have not been my strongest area, but I have learnt so much from attempting the challenges, something I really enjoyed doing. I would like to finish with a math problem I can do – the escape velocity of Venus. So here goes…

What is the escape velocity from the Venus exosphere, which begins about 220 km above the surface?

mass = 4.867 x 10^24 kg

radius = 6.05 x 10^6 m

height = 2.2 x 10^5 m

Formula:

Screen Shot 2016-05-01 at 2.16.56 PM.png

= 2 x 6.67 x 10^11 x 4.867 x 10^24 / (6.05 x 10^6 + 2.2 x 10^5) = 1.03 x 10^8

v = sqrt (1.03 x 10^8) = 10148 m/s = 10.1 km/s ~ 10 km/s

Please check the math and let me know if I have made a mistake along the way.

Watch BBC The Sky at Night Venus documentary https://www.youtube.com/watch?v=82fS9C9koxU for more information.

Finally…

Huge thanks go to Dr Frank Timmes for being an outstanding teacher during this course, your videos and notes were amazing, thank you sooo much! You have inspired me to learn more about the universe. Big thanks also go to the rest of the team at Arizona State University for putting together an amazing course and for all their support. This has been the best course I have enrolled in on edX and I would highly recommend it to anyone interested in astronomy.

https://courses.edx.org/courses/course-v1:ASUx+AST111x+2161B/info

Thanks for reading, bye bye!

venus hipster.jpg

5 Earth facts to celebrate Earth Day 2016

5. Earth is a terrestrial planet meaning it has these characteristics compared with Jovian planets:

  • Smaller size and mass
  • Higher density of rock and metal
  • Solid surface
  • Closer to the Sun
  • Warmer surface
  • Few moons
  • No rings

pale blue dot

4. Earth’s continents used to be one giant super-continent called Pangaea that existed around 200-300 million years ago.

pangea

3. Earth’s atmosphere is mainly nitrogen, followed by oxygen. So we breathe the second most abundant gas in our atmosphere.

2. If the Earth didn’t spin we would have nasty 200mph winds that blow from the tropics to the poles and back again. Our rotation, and the Coriolis effect, causes 3 convection cells per hemisphere that diverts air flowing north-south to east-west. Air is transported from hotter regions to cooler regions.

coriolis

1. Earth’s atmosphere formed after the world was created. The 3 sources of our atmosphere are:

  • outgassing
  • evaporation
  • surface ejection

We got our deposits of gases and liquids during the era of heavy bombardment during which asteroids and comets brought gases to Earth in frozen form. These were then deposited into the body of the planet.

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5 cool facts about our planets…

5. Venus rotates in the opposite direction to Earth so the Sun rises in the west and sets in the east. It also rotates very slowly so its days and nights are very long.

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4. The ‘no atmosphere’ temperature of Earth is 3 degrees Fahrenheit (-16 Celsius). Without the Greenhouse Effect our oceans would freeze over.

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3. Saturn is light and fluffy enough that its density is less than 1 gram per cubic centimeter – the density of water. So Saturn would float if placed in water.

2. Jupiter’s coloured bands are different cloud systems. The white stripes are called zones and the brown stripes are called belts. The winds in zones go one way, winds in belts go the other way. When you see different colours on the Jovian planets you are actually seeing clouds at different heights.

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1. Earth’s surface gets repaved every 100 million years. This is due to volcanism, tectonics and erosion. Large craters on Earth have been paved over.

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