Learning Goals Students will: 1) understand the terms for common celestial objects and define the physical properties of each

Learning Goals Students will: 1) understand the terms for common celestial objects and define the physical properties of each.

Success Criteria Students will display learning goals by: 1) Defining the physical properties of each celestial object.

Common measurement systems used in Astronomy

Distances in Space 1 light-year (1 ly) = the distance light can travel in one year = 9.467 x 10 15 m or 9.467 x 10 12 km = 23 668 200 000 return trips from here to Toronto = 236 169 970 trips around the world. It takes light about 8 minutes to travel from the Sun to our planet

Distances in Space 1) Astronomical Unit The average distance from the Earth to the Sun (Earths orbit is not a perfect circle) 1 A.U. = 1.495 x 10 11 m = 1.495 X 10 8 km (about 150 million km) Most conveniently used for measuring distances to planets or other objects in our Solar System (far better than using kilometers) The most distant planet (Neptune) is about 30 AU from the sun.

Distances in Space Parsec (pc) A parsec is calculated using the following right triangle: If the base of the triangle (adjacent side) is 1 astronomical unit (1 AU) and the opposite angle is 1 second, then the length of the opposite side is 1 parsec. 1 pc = 3.086 x 10 16 m = 3.261 light years (ly)

Distances in Space Methods of Measuring Distances 1) Parallax The angle to the distant object is measured twice during a year. The angle between the measurements can be used to find the distance. Parsecs are often used when measuring distances with parallax This method is used when measuring the distance to nearby stars (usually less than a few hundred ly)

Distances in Space Methods of Measuring Distances 2) The Red Shift. This method will be explained in detail when discussing the Big Bang Theory (not the TV show). It is the light wave equivalent of the Doppler Shift for sound waves. This method uses the speed at which stars are moving away from the Earth. It is the most commonly used method of determining the distance to stars. http://www.youtube.com/watch?v=FhfnqboacV0 (excellent video 2:28) http://www.youtube.com/watch?v=FhfnqboacV0 Astronomers look for the hydrogen and helium lines in the spectrographs of celestial objects (usually the two strongest sets of lines on the absorption question)

Using the Red Shift to measure distances The most accurate way to measure redshift is by using spectroscopy. By looking at the spectra of stars or galaxies, astronomers can compare the spectra they see for different elements with the spectra they would expect. If the absorption or emission lines they see are shifted, they know the object is moving either towards us or away from us. In the image at right, the object is redshifted because the absorption lines are all shifted towards the red end of the spectrum. This object is moving away from us. Astronomers talk about redshift in terms of the redshift parameter z. This is calculated with an equation: z = ( observed - rest )/ rest where observed is the observed wavelength of a spectral line, and rest is the wavelength that line would have if its source was not in motion.

Sample red-shift data Rest Wavelengths of Hydrogen - Balmer Series NameColor Wavelength (Angstroms) Alpha () Red6562.8 Beta () Blue-green4861.3 Gamma () Violet4340.5 Delta () Deep Violet4101.7 The normal wavelengths for the 4 most distinct lines in the hydrogen (H) spectrum are listed in black The position of these wavelengths is listed for galaxy 587731512071880746. Notice that the values are all higher! Using the Hubble Constant (H o ) and the equation: cz = H o d (c= speed of light, z = redshift, d= distance), the distance to the galaxy can be determined. This method can be verified (for objects closer than 100 ly) using the parallax method. Wavelengths of Hydrogen - Balmer Series for a distant galaxy Object ID # 587731512071880746 NameColor Wavelength (Angstroms) Alpha () Red7220 Beta () Blue-green5360 Gamma () Violet4780 Delta () Deep Violet4500

Sample data z Time the light has been traveling Distance to the object now 0.00007151 million years 1 million light years 0.10 1.286 billion years 1.349 billion light years 0.25 2.916 billion years 3.260 billion light years.55.019 billion years 5.936 billion light years 17.731 billion years 10.147 billion light years 2 10.324 billion years 15.424 billion light years 5 12.469 billion years 22.322 billion light years 10 13.184 billion years 26.596 billion light years Notice how the absorption spectral lines shift further to the red end as more distant objects are compared.

Meteoroid A chunk of interplanetary rock or dust that can be seen as a track of light in the sky as it burns up in the Earths atmosphere. This is a constant occurrence in the Earths atmosphere. These chunks are too small to survive the heat of friction as they travel through the Earths atmosphere.

Meteorite an interplanetary chunk of rock after it impacts on a planet or moon. More simply a meteoroid that hits a planet or moon. Meteorites have to pass through the atmosphere to hit the Earth and therefore must be fairly large. Meteorites of immense size have hit the Earth one that was approximately 20 km across caused the extinction of the dinosaurs.

Meteor a chunk of interplanetary rock that is much smaller than an asteroid. More simply a meteoroid that is travelling through space. The melted appearance of this specimen suggests that is actually a meteorite. Most meteors were formed as the Solar System formed and are chunks of debris left over from this process geologists used meteors to date the age of the Earth and the solar system as a whole. There are a great variety of Meteor types based on composition iron rich, stony, stony-irons, chondrites (some rich in carbon)

Meteors & meteorites Two typical meteors are show at far left. The famous Barringer meteor crater (below) in Arizona is almost 2 km across. A massive meteorite roared over the Russian city of Chelyabinsk on Feb 15, 2013, shattering windows and damaging buildings.

Meteor Showers Meteor occur at random intervals and we generally refer to them as shooting stars There are particular periods where the rate of meteor sighting increase dramatically these are called meteor showers The name is somewhat misleading, as 1 meteor/minute would rate as a good meteor shower. Some meteor showers happen at regular intervals. For example the Perseid meteor show (named because the meteors seem to come from the constellation Perseus) occurs every August and is the result of the earth passing through the debris of the comet Swift- Tuttle.

Kitchener Meteorite This meteorite, weighing 202 grams, fell to Earth at 8:30am on Sunday, July 12, 1998. It passed close to the left shoulder of Orville Delong, who was walking up to the 6th tee of the Doon Valley Golf Club in Kitchener (very close to the Highway 401 overpass over the Grand River) The meteorite is completely covered with a black fusion crust about 0.5mm thick. This crust is formed of glass produced by the intense heat of friction as the meteorite slowed down in the atmosphere The interior of the meteorite is almost white, with particles of iron scattered through it. It is scientifically described as a class L6 chondrite and it probably originated in a body in the asteroid belt which lies between Mars and Jupiter. The Kitchener Meteorite was sliced open and shows a black fusion crust of about 0.5mm and a light coloured interior with particlees of iron scattered though it.

Asteroids A minor planet or non- luminous chunk of rock that is smaller than a planet, but bigger than a meteoroid that orbits a star. A belt of asteroids can be found between Mars and Jupiter. Some asteroids have been perturbed from their orbits and travel in elliptical paths through the inner planets. Since many asteroids would likely be rich in metallic elements, they are a target for future exploration.

Comets An object orbiting the sun, often in a very eccentric elliptical orbit. Comets have been given the nickname dirty snowballs as they are composed mostly of ice and loose rocky material. When the comets path comes close to the sun, the ice is turned into vapour and is released in a long, luminous tail. The tail points directly away from the sun. Often a smaller second tail, points away from the direction of movement.

Comets Comets generally originate from a region of space called the Oort Cloud. Some originate from the Kuiper Belt. When comets pass near larger objects, their orbits are disturbed and they can be directed towards the sun and form elliptical orbits. There are some comets which now travel within the planetary orbits they must have been pushed into these orbits. It is believed that many dwarf planets found in the Kuiper Belt, including Pluto, have compositions similar to comets. Comets have struck the Earth. It is possible that the Tunguska Explosion of 1908 was a comet. Many scientists believe that the source of water in our oceans was due to comet impacts early in our planets existence.

The Oort Cloud The Oort Cloud is a hypothetical region that is thought to stretch outward beyond the Kuiper Belt along the plane of the Solar System. It is named for Dutch Astronomer Jan Oort who proposed this region in 1950. This is a cloud of debris left over from the formation of the Solar System and is the source of comets. Astronomer theorize that it contains over a trillion long period comets greater 0.6 km in size (some which take 50 million years to orbit the sun). It is located beyond the Kuiper Belt The Oort Cloud is located from 5000 to 100000 AU from the sun.

Moons A natural satellite that orbits a planet. Moons can travel in very elliptical orbits. Only moons with sufficient mass form spheres this is because they have sufficient gravity to form this shape. Therefore all small moons are irregular in shape. There are 4 moons larger than our moon in the Solar System, but relative to its planet, Earths moon is by far the largest. Some moons are larger than Mercury (a planet) The 4 largest moons of Jupiter

Planets The definition of a planet became a topic of great interest in 2006, when the Pluto debate came up! As a result, planets must meet the following criteria: 1. An object that orbits the sun. 2. An object that is large enough to be spherical in shape due to a sufficient amount of mass. 3. An object that has an orbit that is not controlled by another planet. 4. An object whose orbit has been cleared of asteroids by its gravity. 5. An object that does not emit own light (and is therefore too small to be considered a star). Many stars form binary systems in which two stars orbit each other. Stars need a sufficient mass of Hydrogen to generate enough gravity to start a nuclear fusion reaction.

Mercury eclipsing or Transversing the Sun

Pluto demoted Planet Due to this definition, Pluto was demoted to the definition of Dwarf Planet. Pluto was discovered in 1930 and was considered a planet until 2006. Pluto has a highly elliptical orbit that is found tilted 17 from the plane of the other 8 planets orbits. Its mass is only 1/20 that of Mercury (and therefore lighter than the moon. Pluto orbit has a 3:2 resonance with Neptune. Thus Pluto orbits three times for every two orbits of Neptune. Neptunes gravity has locked Pluto into this resonance. Some astronomers suggest that Pluto may actually be a very large captured comet.

Pluto demoted Planet Pluto has a moon that is almost half its size suggesting that it is a binary (dwarf) planet (two objects revolving around each other). Four other smaller moons have since been found. Plutos orbit is inclined 17 from the 8 planets. Plutos orbit is retrograde (opposite spin direction to the 8 planets)

Planets The IAU (International Astronomical Union) at one point even suggested expanding the number of planets to 12 (and counting) They suggested making the largest asteroid Ceres a planet (Ceres is the only spherical asteroid in the Asteroid Belt), keeping Pluto a planet, and adding two more Pluto-like planets that were found in the Kuiper belt Sedna and Eris. Since more Pluto-sized objects are being found in the Kuiper Belt (Quaoar and Makemake to name two), the number of planets would continue to increase. However, all of the objects mentioned dont meet all of the criteria on slide 18. Ceres has not cleared its orbit of debris and most Kuiper Belt objects are in resonance with Neptune. Thus we are forever stuck with 8 planets!

Dwarf Planets and the Kuiper Belt Large objects orbiting the sun that do not meet all of the criteria on slide 18. Discovery of dwarf planets in the Kuiper Belt started with Eris in 2003. It is believed to be larger than Pluto. It is suggested that there may be hundreds of dwarf planets in the Kuiper Belt most of them too distant and non-luminous to be found. It is also suggested that they have icy compositions similar to comets and Pluto.

The Kuiper Belt The Kuiper Belt is a doughnut- shaped ring, extending just beyond the orbit of Neptune from about 30 to 55 AU. Named for astronomer Gerard Kuiper. Short period comets originate from the Kuiper Belt (those with orbital periods less than 200 years) It is also the host of many icy dwarf planets including Pluto (also known as KBOs (Kuiper Belt Objects) or TNOs (trans- Neptunian Objects))

Exoplanets There are now thousands of known exoplanets. Planets that orbit other stars than the sun. The first exoplanets were only found 25 years ago. They are found when they pass in front of a star. The search is on to find an Earth- like exoplanet (especially one that might support life)! Many have been found by the Kepler Spacecraft. This will be a separate topic for the discussion of potential life outside of Earth.

Exoplanets as of October 2013

Stars a self-luminous ball of gas that shines or has shone because of a nuclear fusion reaction in its interior. Extreme temperatures (several million K (kelvin)) and pressures are required to ignite a fusion reaction. The sun is our closest star. There are many types of stars that you will learn about in lessons this coming week so I will not get into details at this time! The colour and size of a star can tell an astronomer a great deal about its lifespan and ultimate future. Stars emit light due to the fusion of lighter elements into heavier elements. The vast majority of stars are fusing Hydrogen into Helium.

Infrared image of the Sun. Coronal Mass Ejection (Solar Flare) and several sun spots. An artists rendering of neutron star drawing gas from a companion star that is in orbit. This is often a prelude to a Type II supernova

Constellations Ancient astronomers grouped these stars to form creatures and objects that we call Constellations. Predicting your behaviour or future based on these constellations (particularly the 12 constellations called the Zodiac) is called astrology. Astrology is NOT a science. The stars in a constellation are not necessarily located in a group or a star-cluster.

Zodiac Constellations The position of Zodiac constellations and their appearance in the sky.

Nebula Interstellar region of gas and dust If enough gas and dust are present, gravity will draw the dust together (over millions of years) and the material could pull together to form a star or a cluster of stars. (Our Solar System formed like this) Nebulas can either emit light, absorb light or reflect light. Nebulas can also result from the explosion of a star (Nova or Supernova). Gases from the star are expelled into space. A small remnant star can be seen in the middle of expelled gas in the Hourglass Nebula

Galaxy A collection of stars, gas, and dust bound together by gravity. (all other celestial objects will also be found) The smallest galaxies may contain only a few hundred thousand stars, while the largest galaxies have thousands of billions of stars. Galaxies can be classified based on their shape - this also gives information about their age! Galaxies rotate about a central point the Milky Way galaxy takes 220 million years to rotate.

Milky Way Galaxy Our sun is found in the Milky way Galaxy. We can see the Milky Way at night in a sufficiently dark place (cities produce too much light). The Milky Way galaxy contains 200 - 400 billion stars and is about 120,000 light years across.

The Milky Way Galaxy The Milky Way galaxy contains our solar system. Galaxies come in a variety of shapes (which are indicative of their age and size), but we will discuss this in more detail later in the course.

Galaxies Images from the Hubble Space Telescope and other types of modern telescopes show that the Universe contains billions of galaxies. The Hubble Deep View Telescope provides images of thousands of galaxies in a single frame. (bottom picture)

Neutron Stars and Pulsars A star that has a mass of 1.5 to 3.0 times the mass of the Sun but a radius of only 10 km. It is the result of the gravitational collapse of a large star! This collapse has crushed all matter into neutrons. A teaspoon of a neutron star would weigh thousands of tons. If the neutron star emits jets of matter and energy in a pulsating fashion, it is known as a pulsar. Pulsars spin rapidly and jets of material are often ejected from the poles of the pulsar.

Black Hole a region in space from which, according to the general theory of relativity, neither light, radiation, nor matter can escape. Obviously we cannot see Black Holes, but we can infer their existence from the behaviour of stars and other objects nearby. Black holes have immense gravity and suck in stars and other material that get too close to their gravity wells. It is believed that a supermassive black hole exists in the middle of our galaxy (and the middle of most galaxies. The black holes continue to get larger as they suck in more and more material.

Novas When a star dies, the nuclear reaction in the core stops. Since the outward force no longer exists, the star collapses onto itself due to its force of gravity. This collapse is called a Nova and can be seen from the outer layers of gas ejected from the imploding star (A nebula forms that is illuminated by the collapsed star within). When a small star goes Nova, it leaves behind a small star called a white dwarf and a nebula. Our sun will follow this route (I am simplifying this process I will add more detail later). As stated before, when a star that has a mass of 1.5 to 3.0 times the mass of the Sun goes Nova it will leave behind a neutron star and a nebula.

Black Holes and Supernovas Black holes can only form from the collapse of supermassive stars. (Those with a mass of more than about 10 solar masses). The explosion will form a supernova. The energy released in a supernova is so great that the supernova will outshine every other object in the galaxy for a period of a few weeks. We have only observed two supernovas in our own Galaxy. The core of a supernova may become a black hole if there is sufficient mass.

Supernova The explosion of a star with the resulting release of tremendous amounts of radiation (energy) and dust. They only form from the explosion of very massive stars and leave behind neutron stars or black holes. Elements heavier than iron generally only form from supernovas. A supernova will briefly outshine all other stars in a galaxy. The Crab Nebula is the remnant of a supernova recorded by Chinese astronomers in 1054. It was exceedingly bright in the night sky for years after.

Quasar Quasars or quasi-stellar radio sources are the most energetic and distant members of a class of objects called active galactic nuclei. Scientists believe they are found at the centers of super-massive galaxies and surround supermassive black holes. They release so much energy, they outshine entire galaxies over many EM wavelengths. They are extremely distant, among the most distant objects in the universe and likely formed shortly after the Big Bang (creation of the universe)

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Learning Goals Students will: 1) understand the terms for common celestial objects and define the physical properties of each