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Grade 9 Academic Science – Unit 3 Space Origin and Evolution of the Universe Section 9.7 Pages 393-397 On 4 June 2002, a new planet-like object was observed circling the Sun more than one and a half billion kilometres beyond Pluto. Named Quaoar, it is nearly 1,280 kilometres wide (…half the size of Pluto, larger than Pluto’s moon Charon OR about one-tenth the diameter of Earth) and circles the Sun every 288 years. Quaoar is the biggest astronomical find in the Solar System since the discovery of Pluto 81 years ago. How was Quaoar detected? It was observed with the aid of the Hubble Telescope. So… The Hubble Telescope was named for American astronomer Edwin Hubble. He (1) identified individual stars outside the Milky Way galaxy and (2) determined the Universe was expanding outward. Prior to Hubble, it was believed the only stars in the Universe occurred in the Milky Way, while the rest of the Universe was mainly gas and dust. Hubble observed stars in the Andromeda galaxy. Hubble realized the galaxies were moving apart. Hubble measured RED SHIFTS in the light emissions from the galaxies and observed that the galaxies were moving away from each other at a rate constant to the distance between them. In 1929, he produced Hubble’s Law: The Universe is expanding at a constant rate as determined by the linear proportional relationship between recessional velocity (i.e., rate at which an object is moving away from Earth) and distance. Hubble’s Law suggests the greater the distance from Earth, the faster the movement is occurring. This finding has helped astronomers determine the age of the Universe and prove that the Universe was expanding. (NOTE: Albert Einstein had used his Theory of Relativity in 1917 to predict the Universe was expanding. Einstein suggested that space was curved by gravity, and therefore, it must be able to expand or contract. He found his idea so far fetched that he rejected the idea.) Red Shift See Page 394 in your textbook for an illustration The Red Shift is a pattern of light. In space, each galaxy emits its own distinctive spectrum of light. This distinct pattern, the Light Spectra, shifts depending on whether the light source is moving or stationary. Literally, the wavelength of light is stretched… towards the red end of the spectrum. Thus, a Red Shift is the phenomenon of light from galaxies shifting toward the red end of the visible spectrum demonstrating that the galaxies are moving away from Earth. To understand more, watch the “Ask an Astronomer” You Tube “What is a Redshift?” presentation at http://www.youtube.com/watch?v=FhfnqboacV0 How would you know a shift has occurred…since light travels very fast and we do not observe any spectral shift in our daily lives? HINT: Comparison…”to what?” For fun, watch the “Ask an Astronomer” You Tube clip called “Why aren’t there any Green Stars?” at http://www.youtube.com/watch?feature=endscreen&v=BvjeP3SfD1g&NR=1 Dark Matter Space is mostly black and empty. However, something must occupy the mass called space. Dark Matter is an undetermined type of matter thought to be the undefined mass of the Universe. Dark matter does not emit or scatter electromagnetic radiation (…including visible light), and as such, dark matter cannot be seen. Yet, dark matter is estimated to makeup 83% of the matter in the Universe. Isn’t space fun? How would I know about dark matter if it is not seen…and presently, largely undefined? To answer a question, you start with what you know. The Universe is expanding Expansion can be determined by Red Shifts Light moves across space as electromagnetic radiation Gravitational Forces exist throughout the Universe, and these forces influence other objects in space Stars are luminous (i.e., emit light) Luminosity (i.e., amount of light emitted) is used to determine the size and mass of stars. …and more Scientifically, the size of a galaxy is estimated using, among other measures, luminosity. If I know an object’s luminosity, I can determine its mass. Yet, non-random discrepancies and errors occurred in the measurements. That is, the expected luminosity and the observed luminosity were slightly different. It seemed the observed luminosity was greater or pulled in unanticipated directions….by unseen mass or gravitational force, respectfully. Moreover, the discrepancies showed a consistent pattern such as amount and shift. To account for the error, dark matter must exist. Dark matter is something that has a gravitational force. More interestingly, the Universe contains lots of dark matter. Some dark matter may consist of ordinary matter (e.g., contains atoms) but does not emit electromagnetic radiation. This is called baryonic dark matter. Most dark matter is non-baryonic dark matter. It is not composed of ordinary matter, carry electric charges or interact with ordinary matter via electromagnetic radiation. It may contain neutrinos and supersymmetric particles (…ha…prove that on…all theoretical to date…) that undergo total destruction to produce observable photons. Most often, non-baryonic dark matter can only be inferred by observed gravitational attraction. Do you believe it? The June 1988 Scientific American article “Is dark matter theory or fact?” (http://www.scientificamerican.com/article.cfm?id=is-dark-matter-theory-or) notes dark matter reveals its presence via the gravitational effect it exerts on luminous matter (i.e., matter seen with telescopes) in the Universe. The best example of the gravitational effects of dark matter is observed when looking at the rotation of galaxies. Galactic rotation is observed via the Light Spectra of stars in each part of the galaxy. When the light from a star is observed using a prism, the starlight is separated into its true colours with a specific wavelength of light. The wavelengths “show” which elements the stars contain, and thus, a star's composition. When a star is moving away from us, all of the wavelengths of the spectral lines are shifted to higher values (i.e., red) than they would have been were the star stationary or moving side to side (neither towards nor away from us). This shifting is known as a Doppler shift. By measuring the shift in wavelength, the speed of movement away (red) or towards (blue) Earth can be calculated. When a galaxy is rotating, the starlight from stars on the side of the galaxy that is moving towards are blue-shifted (…think opposite of Red Shift), while the starlight from the stars on the other side of the galaxy are red-shifted. Thus, the speed and direction that a star in the galaxy is orbiting about the centre of the galaxy can be observed. When stars orbit the centre of a galaxy, their orbital speed is determined by the distribution of the mass contained within the galaxy. A graph showing the orbital speeds of the stars versus their distances from the centre of the galaxy is the "rotation curve" for the stars in the galaxy. By adding all the luminous matter seen in the galaxy (…including stars, gas and dust…) and using Newton’s laws of gravitational physics, the speed of stars should decrease in a predictable manner the father away they are from the centre of the galaxy. This was NOT observed. Rather, stars far from the centre move faster than expected. To account for this observation, dark matter must exist in the galaxies…in a large, spherical distribution known as a galactic halo. Neat, eh? Dark Energy If the Universe is expanding at a steady rate, it is logical to think that at some point the Universe will slow its expansion, eventually start to contract (i.e., shrink) and, once again, become a singularity. “We are all doomed,” you yell. Well, not yet. The Universe is expanding. Moreover, the rate of expansion is increasing. Some unknown and unexplainable force, called DARK ENERGY, is offsetting the force of gravity and causing the Universe to expand faster. Essentially, dark energy has the opposite function of dark matter. Dark matter brings things together by gravitational force; whereas, dark energy is an unseen and unknown agent that drives things apart. Big Bang Theory Task Write a summary of your perception of the Big Bang. Write or draw a short story that incorporates accurate and essential parts of the Big Bang. Draw a cartoon depicting accurately the Big Bang.