Rendezvous with a Comet Challenger Mission: Rendezvous with a Comet

Rendezvous To meet up in a location

A probe entering a comet Courtesy: Pat Rawlings - Deep Impact -NASA & JPL

Simulation Acting out an activity (space mission)

Our Solar System

Earth is a part of The Solar System

Our Solar System is part of the Milky Way Galaxy Which is part of the Universe.

Galaxies

Our Sun Hot ball Of gases

Inner Planets

Outer Planets

Asteroids, Meteoroids and Comets

asteroids Rocky metallic objects that orbit the sun

Year Giuseppe Piazzi discovered the first asteroid, Ceres 1801 Year Giuseppe Piazzi discovered the first asteroid, Ceres

4.6 Earth years it takes the asteroid Ceres to travel around the sun (Ceres – Biggest Asteroid with a 960 km circumference)

2880 Year asteroid 1950 DA will pass close to Earth – The greatest known impact hazard

Asteroids Asteroids are small, rocky worlds. Most asteroids revolve around the sun between the orbits of Mars and Jupiter. (asteroid belt)

Earth has been struck many times in its history by asteroids.

100 km 212 Million years old Canada

A S T E R O I D B L

meteorite Meteor shower A chunk of metal or rock that reaches Earth from space meteorite

Meteoroid A meteoroid is a chunk of rock, metal, or dust in space.

A Meteor: “A shooting star” Shooting stars are not actually stars. These flashes of light across the sky are small bits of rock burning up in the Earth’s Atmosphere.

Meteorite Meteoroids that survive as they pass through the atmosphere and hit Earth’s surface are called meteorites.

There are three major types of meteorites: stone, iron and stony-iron. http://www.meteorlab.com/METEORLAB2001dev/Open1.htm There are three major types of meteorites: stone, iron and stony-iron.

Barringer Meteor Crater, Arizona A meteorite can make a hole, or crater, in the ground when it hits it. The larger the meteorite, the bigger the hole.

METEOROID: A piece of stone or metal that travels in outer space. METEOR: An object from space that becomes glowing hot when it passes into Earth's atmosphere. METEORITE: A piece of stone or metal from space that falls to Earth's surface.

comets Lumps of ice and dust that periodically come to the center of the solar system from the outer reaches.

Dirty Snowballs Comets are dusty chunks of ice During each orbit around the sun they partially vaporize Have elliptical orbits They are about the size of an earth mountain. (dirt and ice) Comets’ orbits are usually very long, narrow ellipses. They produce tails of gas and dust when they approach the sun. Courtesy: Calvin J. Hamilton

History Unlike the other small bodies in the solar system, comets have been known since antiquity. There are Chinese records of Comet Halley going back to at least 240 BC. The famous Bayeux Tapestry, which commemorates the Norman Conquest of England in 1066, depicts an apparition of Comet Halley. As of 1995, 878 comets have been cataloged and their orbits at least roughly calculated. Of these 184 are periodic comets (orbital periods less than 200 years); some of the remainder are no doubt periodic as well, but their orbits have not been determined with sufficient accuracy to tell for sure.

Comets have been regarded as omens, even as recently as 1986. The history of comet watching dates back to 1000 BC from the Chinese records and Chaldea, a place in present Iraq. Comets have been regarded as omens, even as recently as 1986. Battle of Hastings - 1066 Today astronomers study comets from scientific perspectives, and our understanding of these fascinating objects have grown tremendously.

Structure of a Comet Solar heat vaporizes the nucleus to produce Coma - Hydrogen gas Envelope Dust tail Ion tail Courtesy: Deep Impact - NASA & JPL

Parts of a Comet When they are near the Sun and active, comets have several distinct parts: nucleus: relatively solid and stable, mostly ice and gas with a small amount of dust and other solids; coma: dense cloud of water, carbon dioxide and other neutral gases sublimed from the nucleus; hydrogen cloud: huge (millions of km in diameter) but very sparse envelope of neutral hydrogen; dust tail: up to 10 million km long composed of smoke-sized dust particles driven off the nucleus by escaping gases; this is the most prominent part of a comet to the unaided eye; Ion tail: as much as several hundred million km long composed of plasma and laced with rays and streamers caused by interactions with the solar wind.

Comet Nucleus (plural: Nuclei) A drawing of what the surface of a comet might look like. The nucleus of a comet is the central portion of the head of a comet. It is a solid part of the comet, made of a special sort of dust which is called "fluffy" because it could be as light weight and full of holes as a sponge. The holes of this "sponge" are filled with ices like water, carbon dioxide (dry ice), and carbon monoxide (what comes out of your car).

Coma This cloud, called the coma, is the atmosphere of the comet and can extend for millions of miles. The cloud is very thin, however, 10,000 times thinner than a cloud in the Earth's atmosphere! The neutral particles that are in the coma can actually become excited by the solar wind causing the particles to become ions. A continual stream of neutral particles is produced as long as the nucleus is evaporating, and these neutral particles are continually converted to ions. These ions are what help form the comet tail.

Tails A comet generally has two tails, not one. One tail is due to the comet's dust particles, the other is due to ionized gas from the comet coma. Dust particles form the first tail. This comet tail generally points back along the comet path (so if the comet is traveling right, the dust tail extends to the left). Ions (electrically charged particles), which first come from the nucleus as (neutral) gaseous particles, are swept into the second comet tail. Because of the special interaction with the Sun's magnetic field, this tail always points directly away from the Sun.

Schematic of a Comet This image is a schematic of a comet. The center part of the comet, or nucleus, is represented by the flame. The solar wind particles are shown as green dots with arrows. And the ionized particles are shown as green/red dots with arrows. Neutral particles are shown by the other dots (without arrows).

Orbits of Comets Aphelion distance Comet Sun Earth Perihelion distance Elliptical in Shape Randomly oriented Aphelion distance Comet Sun Earth Perihelion distance

Comet Hunters Comet are named by International Astronomical Union (IAU) after the person who first discovers them. Many comets are discovered by amateur astronomers. Charles Messier, E. E. Bernard, Shoemaker and Levy, Hale and Bopp, Ikeya, Seki and Hayakutake are popular comet hunters.

Origins of Comets Comets are thought to be the left over debris from during the time of formation of the solar system. The elliptical orbits of comets suggest that they underwent gravitational pull from the giant planets. This all lead us to infer two possible locations where comets could start their journey towards the sun.

Possible Homes for Comets Kuiper Belt Oort Cloud Courtesy - Deep Impact - NASA - JPL

Kuiper Belt Discovered by Gerard Kuiper in 1951 The belt is 30 to 500 AU from the Sun The plane of the belt is close to the ecliptic Probably contains more than 100,000 objects Some of these objects are 100 km or larger in diameter

Oort Cloud Hypothesized by a Dutch Astronomer Jan Oort in 1950. Shape is spherical distribution around the Sun. 50,000 AU from the Sun. May contain 5 trillion objects. Probably created 4.6 billion years ago.

Comets and their Spectra Spectroscopy is a technique in which light is broken into its component colors. Each chemical element show their fingerprint in the spectrum of the object. We can thus find the composition of comets by identifying the fingerprints. Most of the information on comets comes from infrared radiation, because comets are cold objects they radiate strongly at infrared radiation.

Comet Collisions Comet collisions with Earth can bring devastation to life on Earth. Jupiter in our solar system is the largest planet and thus exerts greater gravitational pull on incoming Comets. Study of Shoemaker-Levey collision with Jupiter gave us important facts about Comet collisions.

Comet Collisions Courtesy: NASA/JPL

Halley’s Comet…. Orbits every 76 years

Halley’s Comet Orbit… next seen in 2062

Winter and early spring of 1997 Comet: Hale-Bopp Winter and early spring of 1997 Next sighting: 4380

Facts Comets are invisible except when they are near the Sun. Most comets have highly eccentric orbits which take them far beyond the orbit of Pluto; these are seen once and then disappear for millennia. Only the short- and intermediate-period comets (like Comet Halley), stay within the orbit of Pluto for a significant fraction of their orbits.

Approaching the Sun As a comet approaches the Sun, it begins to evaporate, forming the coma and a spectacular comet tail. Evaporation is not quite the correct term to describe what happens to a comet as it approaches the sun. The correct term is sublimation. The term describes what happens when a frozen material changes to gaseous form. (Evaporation describes what happens when a liquid changes to a vapor).

Sublimation The most common example of sublimation is that of dry ice, which is the common name of frozen CO2. When dry ice is exposed to the air it begins to sublimate, or change to vapor, before your very eyes. This happens to dry ice because at room temperature the frozen gas would rather be a gas than frozen solid.

Long Period Comets A comet with an orbital period of more than 200 years.

Short Period Comets A comet with an orbital period of less than 200 years. Short period fade over time as more and more of their ices melt with each passage of the Sun. Examples: Comet Halley, 76-year orbit; Comet Encke, 3.3-year orbit; Comet Wild 2, 6.2 year orbit.

orbit The path a planetary body makes as it revolves around the sun The orbit of a comet tends to be far more elliptical than planet’s orbits.

Circle A geometric shape where all points on a plane are the same distance from the center

ellipse A geometrical shape where all the points on a curve is the constant sum of the distances from two fixed points, called focal points.

Perihelion The point where an object orbiting the Sun is closest to the Sun

Astronomical unit (AU) One AU is equal to the average distance between the Sun and Earth, approximately 150 million kilometers (93 million miles)

Ejecta The debris that is ejected from the site of impact when a crater forms

Gravity Force of attraction between two objects Just as Earth pulls on you, you pull on Earth with the exact same amount of force.

mass The amount of matter in an object The measure of an object’s inertia. Mass is not the same as weight, which measures the gravitational force on an object. Your mass is the same everywhere, whether you are at home, on the Moon, or floating in interplanetary space.

particle A tiny quantity of a substance

Flight Director The commander working with the crew in mission control

Image A picture that can be sent from Mission Control to the spacecraft to assist you with your work

Data Log Used in Mission Control to record experimental data

Mission Commander The Commander working with the crew in the spacecraft

Mission Status A television monitor that shows the task each team is working on and the time left in the mission

Monitor A screen that shows mission activities

Priority Something that is very important

Start Code A number entered into the computer system when a spacecraft crew member is starting a new task

Flight Manual Step-by-step instructions for each task found in Mission Control

Task Card Step-by-step instructions for each task found in the spacecraft

Data Team: Data Information collected during the crew’s experiments

Data Team: Image A digital picture of equipment or materials used by a team on the Spacecraft

Isolation Team: Balance A scale for weighing materials

Isolation Team: CPM (counts per minute); the number of radioactive particles striking the sensor of a Geiger counter during each minute.

Isolation Team: Filter A device used to separate impurities from the air

Isolation Team: Geiger Counter A device for measuring radioactivity

Isolation Team: Isolation Chamber An airtight, enclosed work area

Isolation Team: Micrometeoroid Tiny bits of asteroids that travel at 18,000 miles per hour in earth’s orbit: can damage spacecraft upon impact

Isolation Team: Radioactivity A physical property of some hazardous materials that causes the material to emit particles that can be measured with a Geiger counter

Isolation Team: Transmittance The penetration of radioactive particles through materials such as water and aluminum

Remote: Balance An electronic scale used for measuring mass

Remote: Glovebox A special experiment area that is enclosed to protect your experiments

Remote: Mass A measurement of the amount of matter within any object

Remote: Volume A measurement of the amount of space an object takes up

Medical: Auditory Reaction Time How long it takes to react to a sound you hear

Medical: Blood Pressure The pressure of the blood on the walls of the blood vessels

Medical: Peripheral Vision The field seen in a surrounding space while looking straight ahead

Medical: Gravity The force that pulls bodies toward the center of the planet

Medical: Pulse Rate The pressure in the arteries due to the beating of the heart

Medical: Respiration Rate The number of breaths per minute

Medical: Skin Temperature External temperature of the body; lower than internal temperature

Medical: Visual Reaction Time How long it takes to react to a light you see

Probe: Airlock The special drawer in which the probe is securely kept

Probe: Cable A wire that carries electricity from one component to another in the probe

Probe: Component An electronic part that is plugged into the probe

Probe: Deploy Launch

Probe: Probe A data-collecting device which will explore a comet

Life Support: Ammeter A device for measuring light

Life Support: Barometer An instrument for measuring air pressure

Life Support: Beaker A laboratory device for measuring liquid

Life Support: Dissolve To change from a solid to a liquid state

Life Support: Environmental Conditions The temperature, air pressure and humidity in the spacecraft

Life Support: Graduated Cylinder A laboratory device for measuring liquids

Life Support: Hygrometer An instrument used to measure relative humidity

Life Support: Indicator A chemical used for testing if a liquid is acid base or neutral

Life Support: Liter The basic unit of volume in the metric system; one liter equals 34 fluid ounces, or 1.06 quarts

Life Support: MA (milliamperes or Milliamps); the units attached to the number determined by the ammeter , one thousandth of an Ampere

Life Support: milli- One thousandth of something

Life Support: mL One thousandth of a liter

Life Support: pH A number which tells how acidic or basic a liquid is

Life Support: ppm (parts per million); the units attached to the number determined by the TDS meter

Life Support: Solar Energy Energy provided by the sun

Life Support: TDS (total dissolved solids); a number telling how much solid material is dissolved in water, measured by the TDS meter

Life Support: Valve A device used to control the flow of air or water

Navigation Team: Angle The point formed by the joining of two lines

Navigation Team: Detector A device used to gather information

Navigation Team: Grid A system of X and Y coordinates used in launching detectors

Navigation Team: Initialize To begin or name something

Navigation Team: Particle density A number telling how tightly packed the material in a comet is

Navigation Team: Star Chart A paper map of the stars

spectrometer An instrument used to obtain and record a spectrum of an astronomical object A spectrum is a series of colors that is produced when light is spread out in order of wavelength.

Navigation Team: Starfield A group of stars in view of the spacecraft’s camera

Navigation: Density Mass of a substance contained per unit of volume

Navigation: Coma The atmosphere of a comet, which surrounds the nucleus

Navigation: Nucleus The solid part of a comet made up of rocks, dust, gas and ice (dirty snowball)

Navigation: Tail The longest part of the comet caused by solar wind

Navigation: Constellation A group of stars that form a pattern in the sky

Navigation: Declination The label for the Y-axis on a star chart. The declination of an object is its distance in degrees above or below the celestial equator. Decline numbers range from 0 degrees to +90 degrees and 0 degrees to -90 degrees. It is similar to latitude on Earth

Navigation: Right Ascension The label for the X-axis on a star chart. The right ascension of an object in the sky is its position, simply put relative to the vernal equinox. It is measured in hours minutes and seconds from 0 hours, 0 minutes and 0 seconds of right ascension at the starting point (vernal equinox), to 23 hours, 59 minutes of right ascension. Right ascension is equivalent to longitude.

Navigation: Eccentricity A numerical value for the shape of an orbit ranging from 0, which equals a circular orbit, to 1 which equals a flattened, elliptical orbit. Planets , moons, asteroids and short period comets have eccentricity values close to 0. long period comets have eccentricity values of 0.5 or more

Navigation: Short Period Comet A comet with an orbital period of less than 200 years. (Comet Halley is 76 years and comet Encke is 3.3 years.

Navigation: Long Period Comet A comet with an orbital period of more than 200 years. (Hale-Bopp is 2425 years and Hyakutake is 15,000 Years)

Navigation: Magnitude A numerical value for the brightness of a celestial object. The brighter an object appears in the sky, the smaller its magnitude the dimmer an object appears in the sky, the larger its magnitude.

Navigation: Stellar Object A celestial object that produces its own light (the sun)