The document discusses near-Earth objects such as asteroids and comets that pose a potential hazard to Earth, noting that over 8,000 near-Earth objects have been discovered so far, including over 1,200 that are considered potentially hazardous asteroids due to their close orbital approaches to Earth. It also provides background on the composition, origins, and properties of asteroids, comets, meteoroids and related small solar system bodies.
The document discusses the history of models of the solar system. For thousands of years, the geocentric model placed Earth at the center. Ptolemy created an influential geocentric model in the 2nd century AD. In 1543, Copernicus published a heliocentric model placing the Sun at the center, though he was afraid to publish it while alive due to religious opposition. Galileo's observations of Jupiter's moons in 1609 provided further evidence supporting the heliocentric model.
Planetesimal ejection describes how leftover debris from the formation of the planets was captured as moons or ended up in the asteroid belt, Kuiper belt, or Oort cloud. Asteroids and meteoroids are small rocky or metallic objects found primarily in the inner solar system, with asteroids larger than 100 meters and meteoroids smaller. They orbit near the plane of the solar system in regions like the asteroid belt. When these objects enter the Earth's atmosphere, they appear as meteors and some survive impact as meteorites. Larger impacts are rarer but can cause global effects like the extinction of dinosaurs.
The document discusses the distribution of matter in the universe. It notes that matter is not evenly distributed, but rather is concentrated in certain areas called galaxies. Galaxies themselves form larger groups known as galaxy clusters. There are also large empty spaces between galaxies and clusters.
The document summarizes the nebular hypothesis theory of solar system formation. It explains that:
1) The solar system formed from the gravitational collapse of a giant interstellar gas cloud 4.5 billion years ago.
2) As the cloud contracted, conservation of angular momentum caused it to flatten into a disk with orderly planetary motion.
3) Variations in temperature caused the inner, rocky planets and outer, gaseous planets to form.
This document contains multiple choice questions and answers about detecting exoplanets. It discusses how the Doppler shift of a star's spectrum can be used to detect planets by looking for periodic redshifting and blueshifting caused by the star's wobble in response to planetary orbits. It also addresses detecting transiting planets by measuring periodic dimming in a star's brightness as planets pass in front of it. Space missions are working to find smaller, Earth-sized planets using these detection methods.
This document provides information about astronomy and various astronomical objects. It begins with definitions of astronomy and early astronomers like Ptolemy, Aristotle, Copernicus and Galileo. It then describes the formation of the solar system and details the inner and outer planets. Other sections discuss the moon, stars, galaxies, and dwarf planets. Key facts are provided about objects like the sun, Milky Way galaxy and planets like Jupiter, Saturn and Mars.
The document provides information about astrophysics and the universe. It discusses the solar system including the sun and planets. It then discusses galaxies including spiral, elliptical, and irregular galaxies. It also covers constellations, nebulae such as the Eagle Nebula and Crab Nebula, and supernovas.
The document contains multiple choice questions about asteroids, comets, and dwarf planets from Chapter 12 of The Cosmic Perspective textbook. It covers topics such as the composition and orbits of asteroids and comets, meteorites, comet tails, meteor showers, and the Kuiper Belt. The questions test understanding of key concepts about small solar system bodies like where they form, what they are made of, how their orbits behave, and potential discoveries.
The document discusses the immense size and scale of the universe. It provides sizes and comparisons for objects from Earth to the observable universe. Earth is compared to a salt grain, while the Sun is like a gumball. The solar system spans a football stadium and galaxies are like orbits of outer planets. The observable universe extends as far as the Oort cloud at the edge of our solar system. Precise measurement techniques are needed to determine astronomical distances.
The document provides an overview of the components of the solar system, including the sun, eight planets, asteroids, comets, and satellites. It discusses the key features of terrestrial and Jovian planets, and provides brief introductions to each of the planets as well as other celestial bodies like asteroids, meteors, comets, and satellites. The document aims to teach students about the structure and composition of objects in the solar system.
Astronomy Photographer of the Year 2014: winners announcedguimera
The Royal Observatory Greenwich announced winners of the 2014 Astronomy Photographer of the Year competition. British photographer James Woodend won first place for his photo of the aurora over a glacier lagoon. A variety of stunning photos were awarded, including images capturing nebulae, galaxies, solar phenomena, and a hybrid solar eclipse in Kenya. Winning photos were selected from over a thousand submissions and are on display at the Royal Observatory Greenwich.
Stars are balls of plasma held together by gravity. Nuclear fusion reactions in their cores release electromagnetic radiation, determining their temperature, color, and luminosity. Stars are classified by temperature from hottest O-type blue stars to coolest M-type red stars. Main sequence stars like our Sun derive energy from hydrogen fusion. As stars age, they evolve through red giant, red supergiant, and white dwarf phases before becoming virtually dead brown or neutron stars. The death of massive stars occurs in supernova explosions that can trigger new star formation.
The document provides information about various space-related topics including: the sun, moon, gravity, the solar system, UFOs, the space race, the moon landing, stars, galaxies, aliens, and orbits. Key points are that the sun is a ball of gas and fire, the moon orbits Earth and reflects sunlight, gravity pulls objects towards each other, our solar system contains planets orbiting the sun, the space race occurred between the US and USSR to reach space first, and Neil Armstrong was the first person to walk on the moon in 1969.
This document discusses several topics in astrophysics including the solar system, meteors and comets, black holes, time travel, and extraterrestrial life. It provides definitions and key facts about these subjects such as meteoroids becoming meteors upon entering Earth's atmosphere, black holes having no surface and stretching objects that fall into them, the possibility of time travel causing paradoxes, and evidence that extraterrestrial life could exist but has not been proven. The document also shares some additional interesting astronomical facts and comparisons.
The document provides information about astronomy and the solar system. It discusses the 8 planets, their characteristics, and interesting facts about each planet. It also describes other space objects like asteroids, comets, and meteors. Tools used to study space such as telescopes, satellites, space probes, and spectroscopes are explained. Finally, it discusses concepts like light years, galaxies, and how mass and distance affect gravitational pull.
The document summarizes key facts about the Milky Way galaxy and the universe:
1) A constellation is a group of stars that appear close together but are not actually physically close. Constellations help people navigate the night sky.
2) A light year is the distance light travels in one year, around 6 trillion miles. The closest star to our solar system, Proxima Centauri, is about 4 light years away.
3) A galaxy is a large group of stars bound together by gravity. Our Milky Way galaxy is a spiral galaxy estimated to contain 200 billion stars.
The document provides an introduction to astrophysics concepts. It outlines the general structure of the solar system as having 8 planets orbiting the sun on orbital paths that are not circular. It distinguishes stellar clusters as groups of stars that are gravitationally bound and relatively close together, compared to constellations which are patterns of stars that can greatly vary in distance from Earth. It defines a light year as the distance light travels in one year and compares the distances between stars within our galaxy and between galaxies. The document describes the apparent motion of stars due to the rotation and revolution of the Earth.
This document provides an overview of stars, galaxies, and the universe. It begins with definitions of key terms like stars, galaxies, and the universe. It then covers the composition of stars and how they are classified. The next sections discuss the life cycles of stars and the different types of galaxies. The document concludes with an explanation of the big bang theory of the universe and how scientists estimate the age of the universe.
The document provides an overview of what is known about the universe based on observations from the Hubble Space Telescope. It discusses how ancient models placed Earth at the center, whereas it is now known that Earth revolves around the sun, which is one of billions of stars. Distances to stars are enormous, measured in light years. Stars appear to move due to Earth's rotation. Stars are giant balls of plasma undergoing nuclear fusion, and their life cycles depend on their mass. Galaxies contain billions of stars and come in different shapes. The universe began in a massive explosion known as the Big Bang around 13.8 billion years ago.
The document defines strategy as "a pattern of decisions and actions in the present, undertaken to take advantage of opportunities and secure future success." It discusses the differences between mission, vision, and strategy. As an example, it outlines Blizzard Entertainment's mission to create epic entertainment experiences, business model of subscriptions for World of Warcraft, and eight core values that represent the company's beliefs, such as "gameplay first" and "every voice matters."
The document contains code for simulating various network protocols like sliding window protocol, stop and wait protocol, socket programming for client server communication, ARP, RARP and code to simulate PING and TRACEROUTE commands. It includes algorithms, programs written in Java with sample inputs and outputs. The programs demonstrate implementation of network layer protocols and utilities.
This study analyzed mercury concentrations in 12 commonly consumed freshwater fish species in Bangladesh. Samples were collected from markets and analyzed using radiochemical neutron activation analysis. Mercury concentrations ranged from 0.250-0.438 μg/g dry weight. Four species had levels from 0.250-0.293 μg/g, four from 0.335-0.393 μg/g, two from 0.407-0.413 μg/g, and one was 0.500 μg/g. The average for all fish was 0.359±0.063 μg/g. Estimated daily mercury intake from fish consumption in Bangladesh was below international safety limits. The results indicate mercury levels in these fish are low and pose no health
Determination of Arsenic, Chromium,Selenium and Zinc in fish samples of Bangladesh has been described and compared with the results published elsewhere.
This document proposes a new OWL profile called OWL LD (Linked Data) based on an analysis of ontology language usage in the Billion Triple Challenge dataset. The analysis found that RDFS features were most prominent, while only certain OWL features expressed in single triples were widely used. OWL LD is defined as a subset of OWL RL that includes only these single-triple features to balance expressiveness with easier implementation. Rules and a grammar are also defined to allow OWL LD ontologies to take advantage of existing OWL reasoning tools.
The document outlines regulations for post-graduate programs at Anna University in Chennai, India. It defines key terms, lists the programs offered and admission requirements. Programs include M.E., M.Tech., M.B.A., and M.C.A. and can be full-time or part-time. The duration is a minimum of 4 semesters for full-time and 6 semesters part-time. Students must earn 65-75 credits including core courses, electives, and a project. Project work is evaluated over two phases and must be supervised by qualified faculty.
The document provides code for simulating various network protocols:
1. It includes Java programs for a client and server to simulate the Address Resolution Protocol (ARP) using TCP. The client sends a logical IP address to the server, which responds with the corresponding physical MAC address.
2. A similar pair of programs simulate the Reverse Address Resolution Protocol (RARP) using UDP. The client sends a MAC address and the server responds with the corresponding IP address.
3. The document also states the aim and algorithm for writing code to simulate the PING and TRACEROUTE commands, but does not include the code.
The programs are run and the outputs shown, verifying successful execution and results
An interactive teaching and learning on earth and space educationMank Zein
This document discusses hands-on exercises for teaching astronomy concepts. It introduces CLEA (Contemporary Laboratory Experiences in Astronomy), a project that provides modular laboratory exercises using simulations and real data. The exercises are designed for non-science majors and illustrate modern astronomical techniques and data analysis. Some example CLEA modules measure star properties, study star clusters using the H-R diagram, and determine the speed of light using observations of Jupiter's moons. The goal is to provide an interactive, hands-on experience of what astronomers do through measurement simulations and analysis of real astronomical data sets.
Skolemising Blank Nodes while Preserving IsomorphismAidan Hogan
A talk presented at WWW 2015 on how to label blank nodes in an RDF graph in a deterministic way. Applications include Skolemisation (mapping blank nodes to IRIs); detecting RDF graph isomorphism; as well as RDF graph hashing, signing, canonicalisation etc.
(The slides make heavy use of animation and when flattened, they will not make much sense. Hence I recommend to open them as a slideshow in .ppt format.)
This document summarizes a talk on common errors found in Linked Data. It discusses several types of errors discovered through analyzing over 150,000 RDF documents, including HTTP-level issues like URIs that don't return RDF descriptions, inaccurate content-type reporting, and duplicate content served at different URIs. It also describes reasoning issues such as undefined classes and properties, non-unique values for inverse-functional properties, malformed datatypes, and instances of disjoint classes. The document provides solutions like application workarounds, publishing validators, and the Pedantic Web Group for improving Linked Data quality.
The document provides details on population sizes and areas for several municipalities in the Castile-La Mancha region of Spain, including Zorita de los Canes, Campillo de Dueñas, Torija, Consuegra, Barcience, Calatrava la nueva, Uclés, Sigüenza, Almansa, and Molina de Aragon. Historical context is given for some municipalities. Population sizes range from 98 in Zorita de los Canes to 10,538 in Consuegra. Areas of the municipalities range from 19 square kilometers in Barcience to 358 square kilometers in Consuegra.
This document provides an overview of desktop virtualization using the Pano Logic solution. It discusses the value proposition for partners and customers in reducing costs through centralized management, provisioning, and security. It also addresses some of the challenges of desktop virtualization and how the Pano System provides a complete, integrated solution with a zero client endpoint requiring no management. The document concludes with case studies of education, manufacturing, financial services, and healthcare customers that achieved cost savings, management efficiencies, and security benefits through desktop virtualization with Pano Logic.
Price discrimination occurs when identical goods or services are sold at different prices by the same provider. The goal is to charge each customer the maximum price they are willing to pay. Perfect price discrimination involves charging each customer their exact reservation price, maximizing profits but eliminating consumer surplus. Price discrimination takes various forms in practice, including peak/off-peak pricing for utilities, and offering different ticket prices to business vs leisure travelers for airlines. While it increases profits, price discrimination can be seen as unfair by consumers who pay higher prices than others.
This document summarizes information about the solar system and beyond. It discusses the reclassification of Pluto as a dwarf planet in 2006 based on its size and inability to clear its orbital neighborhood. It also describes the discovery of new moons around Pluto in 2005 and 2006. The document discusses other large trans-Neptunian objects like Eris, Sedna, and Quaoar. It provides information on comets, asteroids, meteoroids, and meteorites. It discusses theories on the origin of comets from the Oort cloud and Kuiper belt and describes comet tails and nucleus. The document summarizes crater formation from meteorite impacts and mass extinction events. It also discusses finding exoplanets using the radial velocity
What is Earth and space science about?
Earth and space science (ESS) connects systems
Earth and space science explores the interconnections between the land, ocean, atmosphere, and life of our planet. These include the cycles of water, carbon, rock, and other materials that continuously shape, influence, and sustain Earth and its inhabitants.
ESS also explores the cyclical interactions between the Earth system and the Sun and Moon.
ESS explores how New Zealand has been shaped by its location
New Zealand straddles the boundary between two major tectonic plates. ESS scientists – and students who study ESS – investigate how this precarious location has impacted (and continues to impact) on New Zealand’s geology and landforms, sometimes in dramatic ways.
ESS investigates the major ocean currents that flow past New Zealand and the impact these and other factors have on our weather and climate.
ESS explores the solar system and beyond
Planet Earth is dynamically linked with the solar system and the wider universe. ESS investigates the structure and composition of these systems and develops understanding of the vast distances and times involved.
What is the Nature of Science strand about?
Why study Earth and space science?
Key concepts: Earth and space science
What is biology | physics | chemistry about?
Interpreting the Nature of Science in an ESS context
Understanding about science
Students learn how understanding of the Earth system, the solar system, the universe, and the interactions between them has developed over time. For example, how:
Wegener and other scientists came to understand that the surface of the earth is broken into tectonic plates that move and interact at their boundaries
Pluto was discovered in 1930 because of disturbances in the orbits of Uranus and Neptune and became the ninth planet, only to be declared a dwarf planet in 2006 after the discovery of Kuiper Belt objects of similar sizes
technologies such as space telescopes and probes have facilitated a build-up of knowledge and understanding about planets, moons, and the rest of the universe
attempts by humans to travel in space have been influenced by the politics of the day
satellites that can measure such factors as the temperature of the surface of the ocean make it possible to build computer models that can be used to accurately monitor changes in the Earth system
the cumulative work of many scientific teams has led to such breakthroughs as understanding the mechanisms of climate change and ocean acidification.
Investigating in science
Students investigate aspects of the Earth system, the solar system and the universe. For example:
Investigating the exchange of carbon dioxide between the ocean and atmosphere by undertaking practical investigations and processing and interpreting secondary data.
Investigating the Sun, Moon and Earth cycles by exploring and developing different models.
useful student materials reference for basic education. Asteroids, comets, and meteors are chunks of rock, ice, and metal left over from the formation of our solar system 4.6 billion years ago. They are a lot like a fossil record of our early solar system. There are about 1.3 million known asteroids, and more than 3,800 known comets. If we take a complete inventory of the entire contents of the Solar System, we find that there are many small, rocky bodies ranging in size from similar to grains of sand up to the size of small moons or comets. The smallest rocky objects that are found in space are referred to as meteoroids. There are three different classifications of meteoroids, depending on how they are observed:
Meteoroid: A chunk of rock orbiting the Sun inside the Solar System.
Meteor: When a meteoroid encounters the Earth's atmosphere, it interacts with the gases in the atmosphere and all or most of it gets vaporized. The streak of light that we see as the rock penetrates the atmosphere is called a meteor, which many people refer to as "a shooting star."
Meteorite: If some of the material that makes up a meteoroid survives the trip through the atmosphere and is found on Earth, we refer to the remnant as a meteorite. If you want help identifying candidate meteorites you can see the following page:
University of New Mexico: How to Identify a Meteorite(link is external)
There are many meteorites that have been recovered on Earth. We find that there are several types of meteorites that can be separated based on their composition. Some meteorites are almost entirely made up of iron and nickel. These chunks of metal are very easy to find when they land on the Earth because they are so dense and are essentially chunks of metal. There are also stone and stony-iron mix meteorites that land on the Earth (these are more common), but since they appear to the untrained eye more like the naturally occurring rocks on the Earth, without extensive testing they are more difficult to identify as meteorites. During its mission, the Mars Rover Opportunity discovered an iron meteorite on Mars. It just happened to be lying on the planet's surface right near where the Rover's heat shield landed after the spacecraft jettisoned it. This is an iron meteorite, making it stand out among the other rocks the Rover has studied intensively during its trip around the surface of Mars.
The document discusses asteroids, comets, and Pluto. It explains that asteroids formed from leftover material from planet formation and are found mainly in the asteroid belt between Mars and Jupiter due to Jupiter's gravitational influence. Comets formed beyond the frost line and have icy compositions; their tails form when they near the Sun and ice sublimates. Most comets originate from the Kuiper Belt and Oort Cloud. Pluto has properties matching Kuiper Belt objects. An impact likely caused the mass extinction that killed the dinosaurs. While impacts pose a real threat, the likelihood of a major impact within our lifetimes is low. Other planets can affect Earth's impact rates through their gravitational influence on small solar system bodies.
The Solar System consists of one star (the Sun), 8 planets that orbit it, over 100 moons, and various smaller objects like asteroids and comets. Planet sizes are determined by measuring their angular sizes and using geometry and known distances. Terrestrial planets like Earth are small and rocky, while Jovian planets like Jupiter are large and gaseous. The formation of the Solar System began from a large cloud of gas and dust that collapsed due to gravity and spun to form a disk, within which planets formed from condensation of dust particles and grew through collisions over millions of years.
This document summarizes key components and concepts about the structure of the solar system:
- The solar system consists of the Sun, eight planets, dwarf planets, asteroids, comets, and other small bodies. The Sun contains over 99% of the solar system's mass.
- The inner terrestrial planets are rocky, while the outer gas giants are large planets composed primarily of hydrogen and helium. An asteroid belt exists between Mars and Jupiter.
- Factors like a planet's mass, distance from the Sun, composition, and atmospheric properties help determine its environment and surface conditions. Larger planets retain heat and atmospheres better than smaller ones.
- Techniques like radioactive dating indicate the solar system formed
Comets are loose collections of ice, dust, and small particles that orbit the sun in elongated ellipses. As comets approach the sun, their ice sublimates and forms an atmosphere and two tails made of gas and dust that point away from the sun. Most comets originate from the Kuiper Belt or distant Oort Cloud. Famous comets include Halley, Hale-Bopp, and Hyakutake. Asteroids orbit in the asteroid belt between Mars and Jupiter and range in size from pebbles to Ceres at 578 miles wide. Some asteroids may have been captured into orbit around Mars as its moons. Meteoroids are small rocks or dust that become meteors as they burn up in
Science and astronomy club (types of celestrial objects)Antilen Jacob
This document provides an overview of celestial objects and Newtonian mechanics. It begins with definitions and images of different types of galaxies such as spiral, elliptical, lenticular, and irregular galaxies. It then discusses pre-Newtonian theories of planetary motion from Ptolemy to Kepler. Next, it covers Newton's universal law of gravitation and its applications by scientists like Halley, Adams, and Le Verrier for predicting comet orbits and deviations in Uranus' orbit. The document concludes with descriptions of objects in our solar system like planets, dwarf planets, moons, comets, and asteroids, followed by an introduction to exoplanet detection methods like the radial velocity and transit methods.
The document provides information about the sun and solar system. It describes the key layers of the sun's atmosphere, including the photosphere, chromosphere, and corona. It also classifies and compares the eight planets based on their size, composition, distance from the sun, rotation, and other characteristics. Additionally, it discusses asteroids, comets, and meteors, noting that asteroids reside in the belt between Mars and Jupiter, while comets have elliptical orbits and meteors appear as streaks of light in the night sky.
Comets are icy members of the solar system that orbit the sun in elliptical orbits. They likely formed from the original material from which the solar system was created 5 billion years ago, making them some of the oldest objects in the solar system. Comets have three main structures - the icy nucleus, a coma of evaporated gases that surrounds the nucleus, and one or two tails that always point away from the sun due to radiation pressure and solar winds. Comets originate from two regions in the outer solar system - the Kuiper Belt and the distant Oort Cloud. The most famous periodic comet is Halley's Comet, which orbits the sun every 76 years.
Recent advances in space technology have allowed scientists from different backgrounds to collaborate on studying Near-Earth Objects like comets and asteroids. Studies of these objects provide clues about the origins of the solar system. Several asteroids have been discovered to come close to Earth in recent years, including Asteroid 2012 DA14 in February 2012. Impacts from asteroids and comets have significantly affected Earth in the past, including possibly causing the extinction of dinosaurs 65 million years ago. On average, objects large enough for an impact are estimated to hit Earth once every 100,000 years or so, with smaller objects hitting more frequently.
Recent advances in space technology have allowed scientists from different fields to collaborate on studying Near-Earth Objects like comets and asteroids. Both comets and asteroids provide clues about the origins of our solar system. Several asteroids have been discovered to come close to Earth in recent years, including Asteroid 2012 DA14 which had a very close approach in February 2012. Impacts from asteroids and comets have affected Earth in the past and could cause catastrophic effects if a large one collided with Earth, though such collisions are rare.
Comets and asteroids are remnants from the formation of the solar system. Comets originate from the Kuiper Belt and Oort Cloud and are icy bodies, while asteroids originate from the Main Asteroid Belt and are rocky fragments. Both have irregular shapes and sizes ranging from 1-100 km. Comets have highly elliptical orbits with periods of 75 years to millions of years, while asteroids have more rounded orbits with periods of 1-100 years. When a meteoroid from space enters the atmosphere, it becomes a meteor or "shooting star"; any fragments that reach the ground are called meteorites.
The document summarizes the key components of the solar system. It describes the terrestrial and Jovian planets, asteroids, meteoroids, and comets. It also outlines theories for how the solar system formed from an initial nebula of dust and gas, including how planets condensed from this nebula via accumulation of dust particles and subsequent collisions of planetesimals over hundreds of millions of years.
Comets are small icy bodies that orbit the sun in elliptical orbits and consist of dust and frozen gases. There are over 650 known comets that range in size from 42 miles to 0.3 miles in diameter. As comets pass near the sun, their ice sublimates and forms a coma of dust and gas around the nucleus. Asteroids are smaller rocky bodies that orbit mainly in the asteroid belt between Mars and Jupiter. Meteors are small rocky objects that burn up as meteors or meteorites when entering the Earth's atmosphere. The document discusses properties of stars like magnitude, color, composition and distance measurement techniques. It describes groupings of stars like clusters, associations and galaxies. Various astronomical instruments used to
The document discusses astronomy and the evolution of our understanding of the universe. It begins with early astronomers like Aristotle, Aristarchus, Eratosthenes, and Hipparchus making observations that helped establish ideas like the Earth being round and the sun being farther than the moon. Later, astronomers discovered properties of stars, galaxies, and proposed theories like the expanding universe. Key topics covered include the formation and life cycles of stars, classification of galaxies, and the standard model of the Big Bang.
The solar system consists of the Sun and everything that orbits around it, including 8 planets. The inner terrestrial planets - Mercury, Venus, Earth, and Mars - are small and rocky. The outer gas giant planets - Jupiter, Saturn, Uranus, and Neptune are much larger. Other objects in the solar system include asteroids in the asteroid belt between Mars and Jupiter, comets made of ice and dust, and meteorites which are rocky debris from space that reaches Earth. The solar system resides in one of the spiral arms of the Milky Way galaxy.
The document provides information about the solar system, including:
- The solar nebula hypothesis which explains how the sun and planets formed from a cloud of gas and dust.
- Distances in space are measured in light years or astronomical units.
- The eight major planets consist of four inner terrestrial planets and four outer gas giants, along with the dwarf planet Pluto.
- Key facts are provided about each of the planets, such as their composition, moons, temperatures, densities and more.
1) Comets, asteroids, and meteoroids are remnants from the formation of the solar system. Comets originate from the Oort Cloud or Kuiper Belt, while asteroids originate from the Main Asteroid Belt.
2) When meteoroids enter Earth's atmosphere, they heat up and glow, appearing as meteors or "shooting stars." Any fragments that reach the ground are called meteorites. Meteor showers occur when Earth passes through the orbit of a comet.
3) Earth has been hit by comets and asteroids in the past, with major impacts potentially causing mass extinctions. Small impacts from meteoroids are more frequent but less damaging. Large impacts capable of threatening life on Earth occur on time
Into the Edge of the Stars Humanity’s changing vision of the cosmos Presenter...Haileyesus Wondwossen
Into the Edge of the Stars Humanity’s changing vision of the cosmos
Presenter: Haileyesus Wondwossen
Basic measurement.
How old our universe is?
Evidence that the universe had a beginning.
Size comparison.
The universe-Earth
Faster travel.
Search for life-bearing planets
Mystery question
oriaethiopia1@gmail.com
+251920720556
Into the Edge of the Stars Humanity’s changing vision of the cosmos Presenter...
Seameo qitep pha_dhani
1. Potential Earth
Hazardous Objects
Dhani Herdiwijaya
Astronomy Research Division, Institute Technology Bandung
Email: dhani@as.itb.ac.id
Training Course on Earth and Space Science for Sustainable
Development, Bandung, 5-11th June 2011
2. Overview
Small Bodies of the Solar System
• Comet
• Asteroid
• Meteoroid
NEO and PHA
Detection, Characterization, and Mitigation
Conclusions
4. Raw materials
Comets, asteroids, and meteors are the
remaining leftovers from the formation of
the solar system.
Their chemical compositions and
distribution yield clues as to how the
solar system formed.
2
5. Small Bodies
Photograph of a meteor entering
Comet: large and old rocky body Earth’s atmosphere.
Asteroid: Small rocky body orbiting the Sun.
Meteoroid: Small particle from a comet or asteroid orbiting
the Sun.
Friction due to the Earth atmosphere
Bolide:
• Extraterrestrial body that collides with Earth, or
• Exceptionally bright, “fireball” meteor.
Meteor:
• The streak of light created in the sky when an asteroid enters
Earth’s atmosphere.
Meteorite:
• Solid remains of a meteoroid that survives atmospheric
passage and lands on Earth’s surface intact.
8. Comets Origins
Primordial gas, dust, and ice frozen in clumps at
the outer limits of the solar system
• Kuiper belt--out to 500 AU
• Oort Cloud--50,000 AU
Occasionally perturbed into elliptical orbits
approaching the Sun
9. Comet Origins & Orbits
Kuiper Belt
• Short period comets (return <200 yrs)
• 50 to 200 A.U.
• Several billion comets
• Cometary orbits are more often near the
ecliptic, but may be prograde or
retrograde.
33
10. Comet Origins & Orbits (2)
Oort Cloud
• Long period comets (return >200 years
or may only pass by sun once)
• Spherical shell of matter up to 2 light
years (65,000 A.U.) in radius.
• Trillions of comets
• Comets may come in from any direction,
with prograde or retrograde orbits.
34
12. Comet Structure
Nucleus
• Water ice, frozen CO , N , methane,
2 2
ammonia, HCN, (CN)2 (cyanogen), amino
acids, sugars all detected.
• Embedded with rocks and dust
• Extremely dark, tarry surface.
Coma
• Envelope of water vapor and H 2 around
nucleus
13. Comet Structure (2)
Ion
tail – ionized gas pushed directly
away from the sun by solar wind.
Dusttail – heavier particles that follow
along behind the path of the comet.
• The dusty path of a comet lingers for
decades, even centuries. When the earth
passes through the dusty path again later, a
meteor shower is produced.
16. Nucleus of Halley’s Comet
Sunlight causes
Jets of gas
jets of gas to
spew from
the comet’s
nucleus. This
creates the
coma.
Photo by Giotto spacecraft •Dark, tarry organic coating
(ESA)
21. Missions to Comets
There have been 11 past missions to comets,
with 2 current missions.
Giotto – examined Halley’s comet in 1986.
Photographed the nucleus from a distance of
only 200 km, then continued on to comet
Grigg-Skellerup in 1992.
Deep Impact – launched a 350 kg copper
impactor into the nucleus of comet 9P/Tempel
1, in July, 2005.
• A 100 m x 25 m crater was created.
22. Comets Demise
Comets eventually
• breakup into smaller fragments (Comet
West below)
• evaporate
• collide with the sun
• collide with other planets
24. Comet Shoemaker-Levy 9 fragments impact
Jupiter, July 16-22, 1994
‘Bull’s eye’
on Jupiter
larger than
Earth; first
evidence of
water in the
jovian
atmospher
27. Comets and Asteroids
Comets:
• Have very eccentric, longer orbit periods.
• Can be more difficult to detect if far from the
Sun.
• Are much less numerous than Near-Earth
Asteroids (NEAs).
• Exhibit jets of volatiles due to heating when in
proximity to the Sun.
Near-Earth Asteroids:
• Orbits are within region of inner planets.
• No volatiles.
• Very numerous:
• Thousands with mean diameter > 1 km.
• Possibly millions with mean diameter of a few
hundreds of meters or less.
28. Ceres – largest, (1030 km). Named
after the Roman goddess of the
harvest (cereal). Recently named a
dwarf planet.
29. Asteroids – rocky leftovers of the
inner solar system
Location
• Asteroid Belt
• Trojan or Lagrange Asteroids
• Random Orbits
Types of Asteroids
Minor planets
NEO’s
30. Asteroid belt
Generally, just outside Mars’ orbit
2.7 A.U. average distance
Total mass of all asteroids is
<5% of the earth’s mass (2 to 4 of
our moons.)
31. The so-called Main Belt of
asteroids lie between the orbits of
Mars and Jupiter, with semi-major
axes 2.2 to 3.3 AU.
32. Orbits: Gaps
• In the main belt, orbital distances are not distributed evenly.
Picture: JPL/SSD Alan B.
Chamberlain
33. Asteroid orbit classifications
Earth-crossing:
• Apollos
• Semi-major axis > 1.0 AU
• Perihelion distance < 1.107 AU
• Atens
• Semi-major axis < 1.0 AU
• Perihelion distance > 0.983 AU
Mars-crossing:
• Amors
• 1.3 AU > perihelion distance > 1.017 AU
34. Lagrange Asteroids
Clusters of asteroids co-orbit with the gas
giant planets, 60o ahead and 60o behind the
positions of the planets.
The clusters are centered on the L4 and L5
Lagrange points (points in space where
Jupiter’s gravitational influence equals the
sun’s gravitation.)
Jupiter’sLagrange asteroids are known as
the Trojan asteroids.
36. By the Number s
• Ceres, the largest asteroid is just less than 1000
km in diameter.
• Total mass of all asteroids is 3x1021 kg:
= 1/2000 mass of Earth
= 1/20 mass of Moon
• We probably now know all asteroids larger than 25
km across, and 50% of the ones down to 10 km in
size.
• There are an estimated 100,000 asteroids larger
than 1 km in size.
37. Expected Population
• What do we expect in terms of numbers of asteroids of
different sizes?
More small ones?
More large ones?
Equal numbers in each size range?
• Scientists predict that fragmentation processes would
produce equal masses of material in each size range.
• But, a 10 km diameter object has 1000 times the volume
(mass) of a 1 km diameter object.
• So, if there is equal mass in each range, then we expect
1000 times as many objects of 1 km diameter as 10 km
diameter.
38. Asteroid Size Distribution
• In mathematical notation, we
expect the number of objects of a
given diameter D to be inversely
proportional to the volume (cube
of diameter):
Expect: 1
N∝ 3
D
• In fact we find that: 1
N ∝ 2.3
D
• Therefore proportionally more of
the mass in the larger objects.
Picture: Tom Quinn and Zeljko Ivezic, SDSS
Collaboration
39. Sizes and Masses
• Because most of the total mass is contained in the
larger bodies, we can estimate the overall mass of the
main asteroid belt quite well.
• How do we describe average size in the distribution of
this type? Most asteroids are still small, but most of the
mass is in the larger ones.
• Until about 1975, asteroids were mostly unresolved,
star-like points in the sky. We were largely restricted
to:
1. charting their orbits, and
2. measure their rotation rates, by observing
periodic changes in brightness (think of a police
light).
40. Obser ving From Ear th
• Two of the most interesting challenges for asteroid scientists
were to measure:
1. the actual sizes, and
2. the reflectivity.
• One method we can use to determine the size is to watch as
asteroid passing in front of (‘occulting’) a bright background
star.
• If we observe the shadow of the asteroid simultaneously from
various points on the Earth, we can deduce the size and
possibly the shape.
• This technique was first used to measure the size of asteroid 3
Juno on Feb 19th 1958 in Malmo, Sweden (P. Bjorklund and S.
Muller).
• Is this likely to work for very many asteroids?
(about 350 have actually been observed, most in the last 5
years, since Hipparcos).
42. Types of Asteroids
Asteroid composition classifications:
• Wide variety of spectral classifications, but there are
three main types:
• S-(Stony) type
• Silicaceous, majority of inner asteroid belt
• Iron mixed with iron- and magnesium-silicates
• M-(Metallic) type
• Metallic iron, most of middle asteroid belt
• C-(Carbonaceous) type
• Carbonaceous, 75% of known asteroids
43. Spectroscopy: Composition
• Spectroscopy is also useful in determining composition,
although the spectral features of minerals are much less
sharp than the spectral lines seen in gases (atmospheres).
• This figure shows spectral
data of bright and dark
terrain on asteroid 433
Eros, as measured by the
NEAR spacecraft.
• The spectra are similar in
some respects to primitive
meteorites, but
differences in composition
remain to be explained.
Figure: from Clark et al 2001
49. Toutatis – one of the closest !
Toutatis spins on 2 axes.
5 km long. Passed just 29 lunar distances
from the earth in 2000.
19
50. Meteoroids – asteroids on a
collision … with us!
Meteor – the trail of light & ionized
gas left by a meteoroid
Meteorite – what’s left of a
meteoroid that hits the Earth.
Bolide – a fireball or especially
bright meteor.
51. Types of Meteorites
Types – just like asteroids!
• stony (incl. carbonaceous chondrites)
• irons & iron / nickel (90% / 10%)
• stony-irons (a combination of
materials)
• the type of meteorite tells you where
it came from.
53. •An iron meteorite (easier to find)
Where the formation of Iron element occurs ?
54. Meteoroids were formed in
parent bodies (planetessimals)
Stonies were formed in the:
mantle
Irons were formed in the:
core
55. Meteoroids – early planet stuff
Meteoroids come from the earliest
condensed stuff in the solar
system. They give us the
chemical composition of the
earliest planetissimals.
Most are about 4.6+ billion years
old ~ the age of solar system
57. Near-Earth Objects
Near-Earth Objects (NEOs) are comets and
asteroids that have been nudged by the
gravitational attraction of nearby planets into
orbits that allow them to enter the Earth's
neighborhood within ~ 45 million km of
Earth’s orbit
Composed mostly of water ice with
embedded dust particles, comets originally
formed in the cold outer planetary system
while most of the rocky asteroids formed in
the warmer inner solar system between the
orbits of Mars and Jupiter.
58. Potentially Hazardous Asteroids
Potentially Hazardous Asteroids (PHAs) are defined based on
parameters that measure the asteroid's potential to make
threatening close approaches to the Earth. Specifically, all
asteroids with a minimum orbit intersection distance (MOID) of
0.05 AU or less and an absolute magnitude (H) of 22.0 or less
are considered PHAs. In other words, asteroids that can't get
any closer to the Earth (i.e. MOID) than 0.05 AU (roughly
7,480,000 km) or are smaller than about 150 m in diameter
(i.e. H = 22.0 with assumed albedo of 13%) are not considered
PHAs.
This ``potential'' to make close Earth approaches does not
mean a PHA will impact the Earth. It only means there is a
possibility for such a threat. By monitoring these PHAs and
updating their orbits as new observations become available, we
can better predict the close-approach statistics and thus their
Earth-impact threat.
59. How Many Near-Earth Objects
Have Been Discovered So Far?
8074 Near-Earth objects have been
discovered.
829 of these NEOs are asteroids with a
diameter of approximately 1 km or larger.
1232 of these NEOs have been classified
as Potentially Hazardous Asteroids (PHAs)
(updated May 31, 2011 from http://neo.jpl.nasa.gov)
60. NEO properties and size
Physical properties
Mass
Density
Porosity
Internal structure
and composition
Surface chemical
composition
Spin state
61. Near-Earth Objects (NEOs)
Asteroids and comets whose orbits are
in close proximity to Earth’s orbit.
• When the phasing is right, such NEOs will
closely approach Earth.
•
Galileo Photograph of Asteroid Gaspra
Potentially Hazardous Asteroids (PHAs) taken October 29st, 1991
have orbits that come to within 0.05 AU of
Earth’s orbit.
If a NEO’s orbit intersects that of Earth,
a collision is possible.
• Depends on phasing (timing).
• Annual meteor showers are caused by Earth Photograph of Comet Linear
C/2002 T7 [May 2004]
passing through the paths of comets.
62. NEO Search and Mitigation Study
Milestones
1992 - NASA recommends six 2.5 m telescopes with
limiting magnitude = 22 to enable the discovery of 90%
of NEOs larger than 1 km within 25 yrs.
1995 – NASA sponsored “Shoemaker Report,” which
recommends the discovery of 90% of NEOs (D > 1 km)
within 15 years.
2003 – NASA recommends extending
search down to D~140 m
63. The Tidal Wave of PHA Discoveries
NASA’s report (3/2007) to Congress outlined several
search techniques (optical & space-based IR) that could
carry out the next generation of search.
~50 times the current data flow
~17,000 PHA discoveries
D>140 m (83% complete)
~80,000 PHA discoveries
D>50 m (~40% complete)
≥10 times the current rate
for Earth impactor warnings
64. NEO internal structure
Monoliths or rubble piles?
• A rubble pile is a non-cohesive (strengthless) asteroid
held together only by gravity.
• Ground observations of spin rates show that most
asteroids are not required to be solid.
• However, this is not conclusive evidence that such
asteroids are in fact rubble piles.
Solid asteroids are more susceptible to
mitigation techniques that rely on deflection,
particularly impulsive deflection.
Porous asteroids may be more difficult to
deflect.
65. Craters on the Earth
Earth’s geologic record (surface
and strata) shows evidence of
many impacts, ranging in size from
small to extinction-level events.
• Most craters on Earth’s surface are
masked by weathering and foliage.
• Shocked quartz is a telltale sign
of an impact site.
• Examples:
• Barringer crater in Arizona
• Chicxulub in the Yucatan
peninsula
• Newly discovered Wilkes Land
crater in Antarctica.
66. Craters on the Earth
Barringer crater in Arizona:
• ~ 50,000 years ago.
• 55 km east of Flagstaff, near
Winslow.
• 1200 m wide, 170 m deep.
• Caused by a nickel-iron meteorite
~ 50 m in size.
• 2.5 Megaton explosion:
• All life within 4 km killed instantly.
• Everything within 22 km leveled.
• Hurricance-force winds out to 40
km.
67. Craters on the Earth
Chicxulub crater:
• Cretacious/Tertiary (K/T) boundary extinction
event.
• ~ 65 million years ago
• More than 70% of species made extinct, including the
dinosaurs
• Caused by the impact of a 9 – 19 km diameter NEO in
the Yucatan Peninsula near Chicxulub
Map Showing The Yucatan Location Detailed Enhanced Image Showing Topographic Enhanced Image of the
the K/T Crater Edge 180 km wide, 900 m Deep K/T Crater
68. Craters on the Earth
Newly discovered Wilkes Land
crater in Antarctica.
• ~ 480 km wide
• Believed to have been
caused by a NEO up to 48
km in mean diameter.
• Likely cause of the Permian-
Triassic extinction 250 million
years ago.
• Confirmation pending.
If so, the impact killed off most
life on Earth at the time. Ohio State University
• Eventually allowed dinosaurs
to flourish.
69. ~1/2 mile across; 300,000 years old, W. Australia
Wolfe Creek Also associated with many small iron meteorites
70. Simple vs. Complex Craters
Simple bowl structure
Diameter is 15-20 times
diameter of impacting
object
All less than 1-2 miles
across on Earth
Complex structure with
central peak, peak ring,
or multiple rings
Melt sheet generated
and thick breccia lens
Terraced, collapsed
walls; about 10x
impactor diameter
71. ENVIRONMNETAL EFFECTS IMPACTS
CRATER FORMING PROCESS
Comet or Asteroid hitting the Earth
Large meteorites form complex
craters
1) incoming meteoroid hits
earth at speeds as high as
30km/sec
2) Impact shock creates high P
& T that vaporizes most of
the crater rock and the
meteoroid
72. ENVIRONMENTAL EFFECTS IMPACTS
CRATER FORMING PROCESS
Comet or Asteroid hitting the Earth
3 The release wave
following the shock
wave causes the center
to rise.
4 The fractured walls
slide into the crater
producing wider and
shallower rim.
Outer walls can have a
diameter 100 times the
depth.
73. Periodic Extinction?
Researchers have found
patterns of periodic
extinction in the fossil
record.
• 62 ± 3 million years
• 140 ± 15 million years
Cause for some periodic
extinctions may be NEO
impacts.
• NEO impact did cause
the K/T boundary
extinction ~65 million
years ago. Rohde & Muller, Cycles in Fossil Diversity, Letters to Nature, vol. 434, pgs. 208-210
74. Famous “Near Misses”
Meteoroid 2004 FU 164
Discovered on 31Mar04
• Crossed Earth’s orbit same night
• 6m in diameter
• Closest approach was 6,400 km
• Closest approach ever recorded
• Would have burned up in the upper atmosphere
75. Famous “Near Misses”
Aten 2004 FH
Discovered on 15Mar04
• Crossed Earth’s orbit on 18Mar04
• 30m in diameter
• Closest approach was 43,000 km
• Geosynchronous satellites at 35,790 km
•2 nd
closest approach ever recorded
• Next approach in 2044
76. Famous “Near Misses”
Apollo 4581 Asclepius (also 1989 FC)
• Discovered on 31Mar89
• Crossed Earth’s orbit on 22Mar89
• 300m in diameter
• Closest approach was 700,000 km
• Missed a direct hit with Earth by 6 hours
77. Apophis
Asteroid 99942 Apophis (previously 2004 MN4)
Apophis is the Greek name
for the Egyptian God Apep,
who is the God of death,
destruction, and darkness.
Discovered on 19Jun04 2036 Apophis Collision Event Data
This asteroid will pass Size 320 - 400 m ¼ mile
within ~ 30,000 km of
Earth’s surface on April 13th, Mass 4.6×1010 kg 130,000 Fully loaded 747
2029. aircraft
If it passes through a Impact 12.59 km/s 28,000 mph
“keyhole” location in space, Velocity
it will return to impact in Impact 870 Mt 43,500 Hiroshima Bombs
Earth in 2036. Energy (20 Kt each)
• Probability fluctuates as Impact 1/38,000 Comparable to death by
observations are made. Probability snakebite or tornado.
78. Upcoming Events
29075 (1950 DA)
• Discovered on 23Feb50 then lost until
31Dec00
• 1.1-1.4 km across (About 1/10 size of
K-T object)
• Calculations predict possible impact
on 16Mar2880 (Torino 1) Radar image of 1950
• Highest mathematical probability ever DA by Arecibo
telescope during the
assigned to a known object (1:300)
2002 pass
• Impact will cause cataclysmic
environmental/climatic damage
79. FREQUENCY OF LARGE IMPACTS
ANNUAL RISK OF DEATH
Over 2000 NEO’s. 25-50% will
eventually hit the earth.
Average time between impacts is
100,000 years.
Risk being killed by impact is 1 in
20,000. High because a huge
number of people 1.5 Billion will
be killed in an impact.
80. Mitigation NEO collisions
Motivation for studying and learning how
to mitigate NEO collisions with Earth:
• Small but dangerous NEOs collide regularly.
• Large and catastrophic NEOs have collided in
the past and will do so again.
• The ability as a species to save ourselves
from this celestial threat is a true milestone.
81. Mitigation NEO collisions
Early detection, accurate threat
assessment, and scientific Asteroid Eros Seen During NEAR Mission
characterization are all essential
to mitigation, so these are
motivated also.
• We already want to study NEOs to
advance solar system science and Comet Tempel 1 Stuck During Deep Impact Mission
have deployed spacecraft missions to
do so.
• NEAR
• Deep Impact
• Hayabusa (MUSES-C) Asteroid Itokawa Seen During Hayabusa Mission
82. Systems Engineering
There is no “silver bullet” solution to the NEO
mitigation problem.
• Each scenario is unique.
• At our current level of knowledge and experience, we
can derive generalized requirements and principles.
• Actual experience gained in practicing on test NEOs
will greatly improve our proficiencies:
• NEO Mitigation
• NEO Science
• NEO Resource Utilization
83. Systems Engineering
Systems:
• Detection and tracking
• Optical and radar
• Ground- and space-based
• Orbit modeling and impact probability assessment
• Post-processing of observational data
• Spacecraft transponder beacon mission
deployed to NEO
• Physical characterization
• Ground or space observatory data processing
• Spacecraft science mission deployed to NEO
• Mitigation system
• Spacecraft mitigation mission deployed to NEO
84. Systems Engineering
We need mitigation systems and spacecraft
missions for mitigation.
• Requirements follow from analysis of the general
hazardous NEO scenario.
• Scenario is expressed as a timeline comprised of
events.
• Each event has an associated system.
• Generalized mitigation mission architecture has been
devised and will be presented.
• Requirements drive this architecture.
• The most important requirement is simply this: If a
NEO is on a collision course with Earth, we must
prevent the collision.
85. NEO Detection
NEO discovery and cataloguing:
• Detection and observations:
• LINEAR
• NEAT
• LONEOS
• Catalina Sky Survey http://www.ll.mit.edu/LINEAR/
• Spacewatch
• Tracking and threat characterization:
• Near-Earth Asteroid Tracking (NEAT) program at JPL
• Near-Earth Objects Dynamic Site (NEODyS) in Pisa,
Italy
86. NEO Characterization
NEO characterization
• Ground or space observatory systems
• The observational data from these systems can
provide estimates for a NEO’s bulk properties.
• These need to be created.
• Spacecraft science missions
• On-orbit NEO science is the only way to gather
accurate and detailed physical data on the NEO.
• Such information is crucial for effective mitigation
system design.
87. NEO Orbit Characterization
Orbit propagation and collision detection:
• Knowledge and classification of NEO orbits
• Identification of PHAs
• Determination of collision probabilities
• Ground or space observatories
• Space observatories offer more coverage and
better observations.
• Allows detection and characterization goals to
be met much more swiftly but at higher cost.
• Position accuracies on the order of 100 m and
velocity accuracies on the order of 0.1 mm/s
within a geocentric distance of 2 AU, assuming
a 35 m receiving dish on Earth.
88. EVENTS OF 20TH
CENTURY
BIGGEST NEAR EVENTS
Assessing Hazards
Have Torino scale which assesses
hazards on a 0 - 10 scale.
Enables calm communication about
the threats.
90. NEO Threat Characterization
Palermo Scale
PI
P = log10
P ∆T - Palermo Scale Value
B
PI - Probability of Impact
PB - Annual Background Probability of Impact
for a NEO with Same Kinetic Energy
∆T - Time in Years Before Impact
91. NEO Threat Characterization
The Torino scale is intended for
communicating impact risk to the general
public.
The Palermo scale is intended for impact risk
communication within the scientific and
engineering communities.
Both scales rate threat by cross-referencing:
• Impact energy.
• Probability of impact.
92. NEO Mitigation
Gravitational keyholes
Small regions in space near Earth defined by the
dynamics between the NEO and Earth such that:
• If the NEO passes through a given keyhole, it will
be placed onto a “resonant” orbit by Earth’s
gravity, causing the NEO to return to collide with
Earth some number of orbits later.
• Example: 7:6 resonance – NEO orbits the sun 6
more times while the Earth orbits 7 more times
and at the end of the 7th Earth orbit, the NEO
collides with Earth.
93. NEO Mitigation Modes
There are three modes of mitigation:
annihilation, fragmentation, and deflection.
Annihilation
• Reduction of NEO to vapor or fine-grain dust cloud by
energy application or pulverization.
• Provides the highest assurance that the threat is
permanently eliminated.
• Requires the most energy out of the three modes.
• Energy requirements are generally prohibitive.
• Required technologies are generally unavailable.
• Ultra high-power laser beams.
• Sets of many high-yield explosives.
• Antimatter torpedoes.
• Series of ultra-high energy kinetic impactors.
94. NEO Mitigation Modes
Fragmentation
• Reduction of NEO to (hopefully) small but not
necessarily negligible pieces.
• Provides assurance that the threat is permanently
eliminated only if the largest fragment is smaller than
the threshold for burning up in Earth’s atmosphere (~
20 – 50 m).
• Least controllable mitigation mode.
• Medium to high energy requirements.
• Examples:
• Properly placed explosives (conventional or nuclear).
• Sufficiently energetic kinetic impactor(s).
• Tungsten bullet “cutters.”
95. NEO Mitigation Modes
Deflection
• Modification of NEO’s orbit such that it misses Earth
rather than collides.
• Potentially provides the least assurance that the threat
is permanently eliminated.
• Gravitational keyholes.
• NEO still exists.
• Most controllable mitigation mode.
• Low to medium energy requirements.
• Examples:
• Nuclear detonations (surface or standoff).
• Attached thrusters (low or high thrust)
• Solar concentrators
• Gravity tractors
96. NEO Deflection Methods
Deflection is the preferred mode of
mitigation.
• Most practical mitigation mode, given current and
foreseeable technology.
• Energy requirements are tractable for a wide
range of NEOs.
• Most controllable, generally.
• With practice we can develop proficiency and
learn the pitfalls.
• This is absolutely critical if we are to be
prepared.
97. NEO Deflection Methods
Nuclear explosives offer the following advantages:
• No anchoring of equipment to NEO.
• Highest available energy density.
• High capability for imparting momentum to a NEO.
• High energy density equates to easier launch from Earth.
• Multiple launches are more feasible.
• High momentum transfer performance:
• Can adequately deflect larger NEOs than other methods even
with limited warning time.
• Technology is currently available.
• Puts former weapons of mass destruction to a use that
benefits all humankind.
98. NEO Deflection Methods
Nuclear explosive disadvantages:
• Untested.
• Required rendezvous and proximity operations
are challenging in some cases.
• Requires special packaging inside launch
vehicle to ensure containment in the event of
launch vehicle failure.
• Danger of inadvertently fragmenting NEO in
an undesirable fashion.
99. NEO Deflection Methods
• Sensitive to NEO physical properties.
• In the absence of good knowledge of NEO physical
properties, the system must be over-designed.
• Requires amendment of the “Nuclear Test Ban
Treaty” (1963).
• Public fear and misunderstanding.
• Political tensions.
100. NEO Scenario Timeline
A general hazardous NEO scenario has
a timeline associated with it.
• Events ranging from initial detection to Earth
collision, if threat goes unmitigated.
• Analysis indicates steps that will maximize our
chances of successful mitigation.
• Lays foundation for requirements derivation
and mitigation mission planning.
101. NEO Scenario Timeline
We don’t necessarily want to have pre-built
mitigation systems on standby.
• Collision of dangerous NEOs is a low-frequency event.
• Maintenance costs.
• Uniqueness of NEO scenarios requires custom
designs.
• We can still improve our rapid deployment skills and
develop modular systems that have both mitigation
and other applications.
• NEO Science
• NEO Resource Utilization
102. Conclusions
Detection and Characterization NEO’s and PHA’s systems
must be maintained, enhanced, and expanded:
• Space-based observatories
• More NEO science missions
• Combine these with mitigation missions for synergy.
• Might even combine with resource utilization
technology test missions for additional
synergy.
• Rapid-deployment beacon mission development.
Continue and enhance NEO science missions.
Frequently, presenters must deliver material of a technical nature to an audience unfamiliar with the topic or vocabulary. The material may be complex or heavy with detail. To present technical material effectively, use the following guidelines from Dale Carnegie Training®. Consider the amount of time available and prepare to organize your material. Narrow your topic. Divide your presentation into clear segments. Follow a logical progression. Maintain your focus throughout. Close the presentation with a summary, repetition of the key steps, or a logical conclusion. Keep your audience in mind at all times. For example, be sure data is clear and information is relevant. Keep the level of detail and vocabulary appropriate for the audience. Use visuals to support key points or steps. Keep alert to the needs of your listeners, and you will have a more receptive audience.
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Determine the best close for your audience and your presentation. Close with a summary; offer options; recommend a strategy; suggest a plan; set a goal. Keep your focus throughout your presentation, and you will more likely achieve your purpose.