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Unit 1 Space Exploration • Satellite – any object that orbits around another object in space – Natural satellite – any naturally occurring (nonman-made) celestial body in orbit around another celestial body. • Examples: moons, planets, asteroids Scientific Research • Some satellites are used to gather data for scientific analysis and can be designed to perform different types of missions Communications • Connect distant places, make communication possible with remote areas – Examples: television, telephone, internet Navigation • Use radio waves to locate positions – Example: GPS (Global positioning system): 24 satellites spaced in orbits so that a receiver anywhere on earth, whether mobile or stationary, can always receive signals from at least 4 satellites • GLONASS (Global Orbiting Navigation satellite system) – satellite navigation system owned by Russia Meteorology • Record images of weather systems, show cloud cover, and monitor hurricanes • They also carry instruments to measure temperature, pressure and humidity used in weather forecasting Earth Resources • Help scientists study Earth’s surface • The satellite’s instruments analyze light and other radiation reflected and emitted from surface features Military • Gather information about battlefields, take detailed pictures, locate missing troops and provide secure communications The Study of Space • Space Transportation System (STS) – a proposed system of reusable manned space vehicles envisioned by NASA in 1969 to support extended operations beyond the Apollo program • It was replaced with the International Space Station, with substantial contribution by Russia • The ISS was completed in 2010 ISS ISS • https://www.nasa.gov/mission_pages/station/ main/index.html Space Stations • Allow astronauts to live in space for long periods of time • The MIR space station had been staffed continuously since 1987-2001 • https://history.nasa.gov/SP-4225/mir/mir.htm MIR Space Probes • Car-sized robot craft launched by rockets • They travel to a predetermined target and investigate it using their onboard instruments Types of Space Probes • Fly-By – surveys its target as it flies past, often at a distance of several thousand kilometers – MESSENGER gathered info on Mercury • Orbiter – travels to a planet or moon then moves into orbit around it – Cassini-Huygens gathering info on Titan (a moon of Saturn) • Lander – lands on the surface of a moon or planet (usually start out as orbiters) – Phoenix Mars Lander https://www.nasa.gov/missions/current/ Telescopes • Radio Telescopes • Computers display radio waves as a digitized images • Use a curved dish antenna to gather waves • Atmosphere does not block out radio waves • The larger the collector the more clear the data. • Used to listen to space • Example: In 1992, the cosmic Background Explorer satellite measured ripples in the cosmic background radiation • • • • • Infrared Telescopes Infrared radiation is detected as heat. Is located where the atmosphere is thin: Mountaintop, airplane, balloon, spacecraft Detects objects by how much heat is given off (Can detect stars, extra solar planets, and comets) • Used during day or night • Example: In 1998, the Infrared Space Observatory discovered water is widespread in space, from moons to interstellar clouds • • • • UV, X-ray, and Gamma ray Telescopes Determine the phase of a star’s life cycle. Are sent above the Earth’s atmosphere UV, X-ray, and Gamma rays are absorbed by Earth’s atmosphere and are difficult to detect from the ground. • Example: • In 1987, the X-ray telescope on the Mir space station detected X-rays from a supernova. • In 1990, the Rosat Telescope discovered over 1000 very hot stars that emit extreme ultraviolet light • Optical Telescopes • Functions – Collect visible light from space – Form better images of faint and distant stars then the human eye • Types – Refracting Telescopes -Starlight enters and is refracted (bent) to form a image. – Reflecting Telescopes - use a mirror to gather light and bring the image. These telescopes are often referred to as "Newtonians" because they were first conceived of by Isaac Newton. • http://www.herschel.caltech.edu/ Origin of the Universe • Two Theories: • 1. The Steady State Theory • 2. The Big Bang Theory Steady State Theory • 1948 – Thomas Gold • the universe has always been pretty much the same as it is today and will always stay the same • suggests that the universe is the same everywhere and time is also the same everywhere • Gold claimed that the universe should look the same in all places and at all times past, present, and future (basically nothing is moving or changing The Problem • In 1929, Edwin Hubble had discovered that all matter in space is moving away from all other matter. This means that the universe is expanding • Gold explained this by saying that as matter in space is moving apart, new matter is being created to fill in the gaps. (However, this is not very likely.) The Steady State Theory is Ruled Out • The most important piece of evidence against the Steady State theory comes from NASA. • A satellite called the Cosmic Background Explorer (COBE) looked 15 billion light years into space (which is the same thing as looking 15 billion years into the past). • COBE found temperature differences that indicating that the universe has changed over time. Big Bang Theory • In the late 1920s, George-Henri Lemaitre (a Jesuit priest) used information from Einstein and others to formulate the Big Bang theory. • Scientists originally did not like the Big Bang theory because it proposed a “moment of creation” that seemed to lean towards religious views of creation • The Big Bang Theory states that 15-20 billion years ago the universe began as an infinitely dense “atom” and all matter everywhere was contained in this “atom.” The “atom” exploded,– hence, the big bang A make-believe timetable of the big bang: Within the first second after the Big Bang gravity came into existence The universe then expanded rapidly and became flooded with subatomic particles that slammed into one another, forming protons and neutrons. Three minutes later, the temperature was 500 billion degrees Fahrenheit. Protons and neutrons formed the nuclei of the simplest elements hydrogen, helium, and lithium. 300 million years later, stars and galaxies began to appear (such as our galaxy, the Milky Way). • Approximately 15.5 – 10.5 billion years after the Big Bang (4.5 billion years ago), our sun and planets formed from a solar nebular (cloud of gas and dust). As the nebula condensed, the temperature in its core got hot enough for nuclear fusion to occur. The core became the sun and the bodies farther from the core became the planets Evidence • Traces of background radiation can still be detected with radio telescopes • Proof that the universe is expanding was found when Edwin Hubble traced light from stars in other galaxies and found that matter in space is clearly moving away from other matter • Everything in the universe is still moving away from other matter, even today • It is hard to sense that we are still moving because everything is still moving too. It is sort of like being in an exploding firecracker. • How does the Big Bang Theory explain the concept of linear time? • Stephen Hawking wondered whether the universe has any beginning at all in terms of space or time. • He suggested that in the earliest stages of the universe, linear time (the orderly progression from past to future) did not exist. • He proposed that time, like the Earth, may be a circle. • “Asking what happened before the Big Bang is like asking for a point one mile north of the North Pole.” Other Objects in the Solar System Asteroids: Rocks that orbit the sun, mainly in the asteroid belt between Mars and Jupiter. However, there are some Earth-crossing asteroids. These asteroids are called Near Earth Asteroids (NEAs). How have asteroids affected Earth? • One widely accepted theory blames an asteroid impact for the extinction of the dinosaurs about 65 million years ago. The impact caused a massive dust cloud that killed many plant species essential to the dinosaurs’ survival. Meteoroids, Meteors, and Meteorites • Meteoroids: Asteroids caught by Earth’s atmosphere. • Meteors: Meteoroids that burn up in Earth’s atmosphere. These are commonly referred to as “shooting stars.” Meteors are streaks of light in the sky resulting from the heat generated by the friction of an incoming meteoroid as it passes through the Earth’s atmosphere. • Meteorites: Meteoroids that fall to Earth without burning up and actually strike the surface of the Earth. Comets • Comet: Masses of ice, dust, and rock particles that orbit the sun. • Tail: The tail of a comet is not a permanent part of the comet; it forms only when the comet nears the sun. The tail becomes visible when the ice inside the comet is heated by the sun, sublimates (goes from a solid to a gas), and is given off as a dust filled gas. No matter which direction a comet is traveling, its tail always points away from the sun. • Head (Coma): The head forms at the same time as the tail by the same process. • Nucleus (Center): The solid, permanent part of a comet Where Are Comets Found? • Comets are found in the Oort Cloud and Kuiper Belt (named after the astronomers who discovered them). Both the Kuiper Belt and the Oort Cloud are located outside our solar system, therefore we do not see the majority of comets, but they are still bound to the sun’s gravitational force • The Kuiper Belt extends from the orbit of Neptune out to several thousand astronomical units (AUs) beyond (remember, 1 AU = 150 million km or 93 million miles). Comets in the Kuiper belt orbit the sun peacefully unless some gravitational influence sends one into an orbit that takes it outside of the belt • The Oort Cloud extends beyond the Kuiper Belt, farther away from the sun. Comets in the Oort Cloud may change their path to the inner solar system only if the gravitational field of something else acts upon it Famous Comets • Halley’s comet - the orbit of Halley’s comet comes close to Earth approximately every 86 years and is due back in 2062 • Shoemaker-Levy 9 comet - the ShoemakerLevy 9 comet collided with Jupiter in 1994 What happens when comets get really close to the sun? • When a comet makes its nearest approach to the sun, some pieces break off from the nucleus, forming micrometeoroids and we experience a meteor shower Why do scientists believe that our solar system is 4.6 billion years old? • They use the process of radioactive decay to date objects in our solar system. Radioactive decay is the natural process by which a specific atom or isotope is converted into another specific atom or isotope at a constant and known rate. By measuring the effects of radioactive decay in a given sample (such as a meteorite), it is possible to determining the age of the sample.