Chandra s focusing power is equivalent to the ability to read the headline of a newspaper at a distance of half a mile!

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1 Chandra X-Ray Observatory What is Chandra? Chandra is the third of NASA s Great Observatories along with the Compton Gamma Ray Observatory and Hubble Space Telescope. It is the largest and most sophisticated X-ray observatory ever constructed. After it is launched into orbit around Earth, Chandra will be able to detect X-ray sources that are billions of light years away and produce images twenty-five times sharper than the best previous X-ray telescope. Chandra s focusing power is equivalent to the ability to read the headline of a newspaper at a distance of half a mile! Mission Specifications Size: 45.3 ft x 64.0 ft Antennas: two low-gain, conical log (solar arrays deployed) spiral antennas Weight: 10,560 pounds Frequencies: transmit 2250 MHz, receive MHz Orbit: 6,200 x 86,000 miles Command Link: 2 kilobits per second (kbps) 28.5 deg. inclination Ascending node: 200 degrees Data Recording: solid state recorder; 1.8 gigabits (16.8 hrs) recording capability Argument of perigee: 270 degrees Downlink: downloaded typically every Operations: eight hours Life: minimum 5 years Contingency Mode: 23 kbps Power: two 3-panel silicon solar arrays (2350W) Safing: autonomous operation three 40 amp-hour nickel hydrogen batteries

2 The Chandra Launch - STS 93 Astronaut Crew The Chandra Observatory will be carried into orbit by the Space Shuttle Columbia, on shuttle mission STS 93. The space shuttle commander for this mission will be Col. Eileen Collins, USAF, NASA. Colonel Collins will be the first woman to command a space shuttle mission. The shuttle pilot will be Cmdr. Jeff Ashby, USN, NASA. Dr. Steven Hawley, NASA, Dr. Cady Coleman, Maj. USAF, NASA, and Col. Michel Tognini, of the French Air Force and French Space Agency, will be the mission specialists in charge of carrying out the scientific objectives of the mission. Eileen Collins was born in Elmira, New York. She is married to Pat Youngs. They have one child. She enjoys running, golf, hiking, camping, reading, photography, and astronomy. She graduated from Elmira Free Academy, Elmira, New York, and received degrees from Corning Community College and Syracuse University and a master of arts degree in space systems management from Webster University. Before becoming an astronaut, Col. Collins was an instructor pilot at the Air Force Academy in Colorado. She has logged over 5,000 hours in 30 different types of aircraft, over 400 hours in space. In 1995 she became the first woman to pilot the space shuttle. Jeffrey S. Ashby was born in Dallas, Texas and raised in the Colorado mountains. In his spare time he likes to ski, backpack and go fly-fishing. Major Ashby graduated from Evergreen High School, Evergreen, Colorado, received a bachelor of science degree in mechanical engineering from the University of Idaho and a master of science degree in aviation systems from the University of Tennessee. He is a Top Gun aviator and test pilot with over 6000 flight hours, 1000 carrier landings, and 33 combat missions during Operation Desert Storm. This will be his first flight into space. Steven A. Hawley was born in Ottawa, Kansas and grew up in Salina, Kansas. He is married to the former Eileen Keegan. He enjoys basketball, softball, golf, running, playing bridge, and umpiring. Hawley graduated from Salina (Central) High School; received a bachelor s degree in physics and astronomy from the University of Kansas and a Ph.D. in astronomy and astrophysics from the University of California in This will be Dr. Hawley s fifth flight on a space shuttle mission. Altogether, he has logged 650 hours in space. Catherine G. Cady Coleman was born in Charleston, South Carolina. Married, she enjoys flying, scuba diving, sports, and music. She graduated from W.T. Woodson High School, in Fairfax, Virginia, received a bachelor of science degree in chemistry from the Massachusetts Institute of Technology, and a Ph.D. in polymer science and engineering from the University of Massachusetts. Dr. Coleman, who is also a Major in the U.S. Air Force, was a mission specialist on a previous space shuttle Columbia flight, in Michel Tognini was born in Vincennes, France. He is married to the former Elena Vassilievna. They have four children. Hobbies include Aeroclub, parachuting and parenting, tennis, wind-surfing, water-skiing, snow-skiing, cross-country running, wave-surfing and microcomputers. Col. Tognini was educated at Lycee de Cachan, Paris. He received an advanced mathematics degree from Epa Grenoble, and an engineering degree from Ecole de l Air (the French Air Force Academy). He is an experienced test pilot and made his first space flight on board the Soyuz spacecraft.

3 CHANDRA The Man Behind The Name NASA s premier X-ray observatory was named the Chandra X-ray Observatory in honor of the late Indian-American Nobel laureate, Subrahmanyan Chandrasekhar. Known to the world as Chandra (which means moon or luminous in Sanskrit), he was widely regarded as one of the foremost astrophysicists of the twentieth century. Chandra immigrated in 1937 from India to the United States, where he joined the faculty of the University of Chicago, a position he remained at until his death. He and his wife became American citizens in Trained as a physicist at Presidency College, in Madras, India and at the University of Cambridge, in England, he was one of the first scientists to combine the disciplines of physics and astronomy. Early in his career he demonstrated that there is an upper limit - now called the Chandrasekhar limit - to the mass of a white dwarf star. A white dwarf is the last stage in the evolution of a star such as the sun. When the nuclear energy source in the center of a star such as the sun is exhausted, it collapses to form a white dwarf. This discovery is basic to much of modern astrophysics, since it shows that stars much more massive than the sun must either explode or form black holes. Chandra was a popular teacher who guided over fifty students to their Ph.D s. His research explored nearly all branches of theoretical astrophysics and he published ten books, each covering a different topic, including one on the relationship between art and science. For 19 years, he served as editor of the Astrophysical Journal and turned it into a world-class publication. In 1983, Chandra was awarded the Nobel prize for his theoretical studies of the physical processes important to the structure and evolution of stars. According to Nobel laureate Hans Bethe, Chandra was a first-rate astrophysicist and a beautiful and warm human being. I am happy to have known him. Chandra probably thought longer and deeper about our universe than anyone since Einstein, said Martin Rees, Great Britain s Astronomer Royal

4 Chandra X-Ray Observatory Why does Chandra have to be in space? Earth s atmosphere absorbs X-rays coming from very hot cosmic matter. Even if Chandra were on a mountaintop like most optical telescopes, no cosmic X-rays could be detected. What is unusual about Chandra s orbit? Chandra will not be in low- Earth orbit like the Hubble Space Telescope. After launch, a built in propulsion system will boost Chandra into a large elliptical orbit around Earth. In this orbit, the distance of Chandra from Earth will range from 10,000km (6,200 miles) to more than a third of the way to the moon. The time to complete an orbit will be 64 hours and 18 minutes. This allows for observation times as long as 52 hours, much longer than can be achieved with the low-earth orbit of a few hundred kilometers used by most satellites. When Chandra is in orbit, how will the observatory be operated? The Observatory will be operated by the Chandra X-Ray Observatory Center (CXC) located in Cambridge, Massachusetts, at the Smithsonian Astrophysical Observatory (SAO), and staffed by personnel from SAO, MIT, and TRW. The CXC is responsible for mission planning and science operations. The CXC s Operations Control Center will be responsible for controlling the flight operations of the observatory, for executing the observing plan, and for receiving the data that Chandra sends back.?how many days is 52 hours? What would happen if you left ordinary camera film exposed for this long? What does this tell you about the brightness of distant cosmic X-rays sources? What other types of radiation (besides X-rays) does our atmosphere block out? What types of radiation does it let through?

5 The X-ray Universe What is the X-ray Universe? Light produced by matter in space comes in many forms: radio waves, infrared radiation, visible light, ultraviolet radiation, X-rays and gamma rays. The starlight our eyes can see in the night sky is visible light. The X-ray universe refers to the universe as observed with telescopes designed to detect X-rays. We could equally well speak of the radio universe or the visible universe. These are not separate universes they are just different ways of observing the same universe. Why observe the cosmos with different types of telescopes? Many objects cannot be seen by even the most powerful optical telescopes which detect radiation in the form of visible light. Radio and infrared telescopes can observe cool clouds of gas and dust that are invisible to optical telescopes. X-ray telescopes observe extremely hot matter with temperatures of millions of degrees Celsius. Without different types of telescopes, we would miss important discoveries about the universe. Does an X-ray telescope take X-rays of the cosmos? No, X-ray telescopes do not work like X-ray machines. An X-ray machine in a doctor s or dentist s office produces X-rays. An X-ray telescope does not produce X-rays. Instead, the telescope collects and focuses X-radiation from cosmic X-ray sources onto detectors. The data from these detectors are then used to make an image of the cosmic X-ray source. What are some examples of cosmic X-ray sources? X-rays are produced when a star explodes, or when matter is heated to millions of degrees near a black hole or neutron star. The largest cosmic X-ray sources are vast clouds of hot gas in galaxy clusters that contain enough matter to make several hundred trillion stars. An optical picture of the cluster of galaxies A1367 shows many galaxies. The X-ray picture of the same cluster reveals hot gas filling the space between the galaxies. The gas has enough mass to make hundreds of galaxies. The color gradations represent differences in brightness of the X-rays due to differences in the density of the hot gas.?if our eyes could somehow see X-rays, would we be able to see peoples bones? If we took a Chandra image of a person, would we be able to see his or her skeleton? Why or why not?

6 The Chandra Telescope & Scientific Instruments Why does an X-ray telescope need to be different from an optical telescope? The high energy of X-rays causes them to reflect off mirrors only if they strike at grazing angles, like a stone skipping across a pond. For this reason, X-ray mirrors have to be carefully shaped and aligned nearly parallel to incoming X-rays. The Chandra telescope is an assembly of four pairs of glass, barrel-shaped mirrors. By nesting the mirrors inside one another, the collection area and therefore the sensitivity of the telescope is increased. Chandra s mirrors are the largest, most precisely shaped and aligned, and smoothest X-ray mirrors ever constructed. How smooth are the mirrors? If the surface of the Earth were polished to the same relative smoothness, Mt. Everest would be less than one foot tall! What happens to the X-rays collected by the mirrors? The telescope mirrors will reflect cosmic X-rays into a small region of the telescope called the focus. The science instruments that will be used at the focus are the High Resolution Camera and the CCD Imaging Spectrometer. These instruments record the number, position and energy of the cosmic X-rays information which can be used to make an X-ray image and to study other properties of the source. Besides the science instruments used to detect X-rays at the focus, Chandra will have two sets of finely-ruled gold gratings, which can be swung into position between the mirrors and the focal plane. When used with either of the science instruments, the gratings will allow precise determination of the energies of the X-rays.?Imagine an Earth with nothing over one foot tall. What kinds of natural and man-made things would be impossible? Why do the Chandra mirrors have to be so smooth?

7 The Chandra Spacecraft What kind of protection does the Chandra telescope need in space? Direct light from the sun will damage the delicate scientific instruments, so the spacecraft has a sunshade door that remains closed until Chandra has achieved pointing control in orbit. After being opened it shadows the entrance of the telescope to allow it to point as close as 45 degrees to the sun. The Chandra spacecraft is protected from the extreme heat and cold of space by special thermal coatings, insulation blankets, radiators, and electrical heaters. This equipment is designed to keep the temperature near the mirrors and science instruments as constant as possible. Will astronauts operate Chandra? No astronauts will help to launch Chandra from the Columbia Space Shuttle, but once it is in orbit Chandra will be operated remotely from the Operations Control Center in Cambridge, Massachusetts. A system of onboard computers in the spacecraft module will automatically: Keep track of the position of the spacecraft in its orbit, Monitor the spacecraft sensors to track temperature, power, etc., Receive and process commands from the ground for the operation of the observatory, Store and process information gathered by the science instruments so that it can be transmitted to the ground. How does the spacecraft get the power it needs to operate? Two solar arrays with a wingspan of 64 feet generate 2 kilowatts of electrical power. The energy is stored in three nickel-hydrogen batteries. How accurately can the Chandra telescope be pointed? Precise control of the spacecraft s attitude, or orientation in space, is critical for making scientific observations, for communicating with the ground, and for collecting solar power. Chandra uses gyros and sensitive cameras which locate known guide stars to tell where it is pointing at any given moment. The spacecraft can be maneuvered to a desired pointing and held there steadily. Chandra s pointing system is extremely precise from a kilometer (0.6 miles) away, it would be able to find the center of a bull s-eye to within three millimeters about the size of a pinhead!?think of some appliances in your home. Can you identify some that use as much power (2 kw) as Chandra? Start with something simple: how much power does the light bulb in your bedroom use? How many of those light bulbs could be powered by the Chandra solar arrays?

8 Chandra will Investigate: Black Holes. What is a black hole? When a collapsed star has more than three times the mass of the Sun, Einstein s general theory of relativity requires that it will collapse forever to form one of the weirdest objects in the universe: a black hole. A black hole does not have a surface in the usual sense of the word. There is simply a region in space around a black hole beyond which we cannot see, because nothing not even light can escape from this region. The boundary between what we can see and what we can t see is called the event horizon. How can scientists observe black holes? Scientists can t observe black holes directly. They can observe light in the form of X-rays produced by matter as it swirls toward a black hole. Why does matter falling toward a black hole produce X-rays? As gas and dust particles swirl toward a black hole, they speed up and form a flattened disk. Collisions between the particles heat them to extreme temperatures. Just before particles pass beyond the event horizon, their temperature rises to many millions of degrees hot enough to produce X-rays. An X-ray telescope is the only way to observe this process, and Chandra s increased sensitivity will allow scientists to see details of this process as never before. Do Black holes grow when matter falls into them? Yes, a black hole in the center of a galaxy where stars are crowded together may grow to a billion times the mass of the Sun. The energy released from large clouds of gas as they fall into these supermassive black holes can be stupendous greater than the output of an entire galaxy with a hundred billion stars!? The average speed of particles in a 100 million degree gas is over 2 million miles per hour. Why do you think the gas around a black hole gets so hot? (Hint: a black hole has extremely strong gravity.)

9 Chandra Will Investigate: The Creative Violence of Supernovae What is a supernova? A supernova is a catastrophic explosion of a massive star. In our galaxy this occurs, on average, about once every 50 years. What causes a massive star to explode? When a massive star uses up its nuclear fuel, it collapses. The interior of the star is crushed to higher and higher densities, eventually reaching temperatures of billions of degrees. Under these extreme conditions, more energetic nuclear reactions occur violently and the collapse is reversed. A thermonuclear shock wave races through the now expanding stellar debris, fusing lighter elements into heavier ones, and producing a brilliant visual outburst that can be as intense as the light of ten billion suns! Why are supernovae important to our existence? Without supernovae many of the elements necessary for life would not be available on Earth. Elements such as carbon, nitrogen, and oxygen are manufactured deep in the interior of stars. They remain there until a supernova spreads them throughout the galaxy. Elements heavier than iron, such as gold or iodine, cannot be produced from reactions in normal stars. A supernova is the only process in the universe energetic enough to form these heavier elements. Why is an X-ray telescope useful for observing the effects of a supernova? The shell of matter thrown off by a supernova plows through the surrounding matter and creates a bubble of multimillion-degree gas. This hot gas will expand and produce X-radiation for thousands of years. Chandra will make it possible to study, better than ever before, the carbon, nitrogen, oxygen, silicon, calcium, iron, and other elements created by stars and spread by supernovae. Supernovae are creative flashes that renew the galaxy. They seed the interstellar gas with heavy elements, heat it with the energy of their radiation, stir it up with the force of their blast waves and cause new stars to form. Tycho Supernova Remnant?Look at a periodic table of the elements and find the elements numbered higher than iron. How would life be different if there were no supernovae and these elements were never created?

10 Chandra will Investigate: Clusters of galaxies and dark matter. Are galaxies spread evenly throughout space? No most galaxies clump together in groups. A group of galaxies can contain anywhere from a few galaxies to a few thousand galaxies; the larger groups are called clusters of galaxies. More than half of all galaxies are members of groups or clusters. Our own Milky Way is part of a group of galaxies called the Local Group. Why were X-ray observations of clusters of galaxies a big surprise? The X-ray observatories discovered very hot, X-ray emitting gas between the galaxies. The mass of this gas in any one cluster is tremendous greater than all the stars in all the galaxies in the cluster. A cluster of galaxies that contains multimillion-degree gas poses a puzzle. Hot gas expands, and the combined gravity from the galaxies and gas in the cluster isn t enough to prevent the gas from escaping. Scientists conclude there must be some unobserved, dark matter providing additional gravity to hold the gas in the cluster. How much dark matter is needed to hold the hot gas in a cluster? An enormous amount is needed about three to ten times the total mass observed in the gas and galaxies combined. Most of the matter in the universe may be in the form of dark matter! What could dark matter be? Dark matter could be collapsed stars, planets or black holes. Or it could be subatomic particles that unlike the particles that make up normal matter produce no light, and can only be detected through their gravity. The exact nature of dark matter is a mystery at this time. Detailed measurements of the size and temperature of the hot gas clouds in clusters of galaxies by Chandra will help to unveil the nature of dark matter and give scientists new clues to the origin, evolution and destiny of the universe. An optical image of a Cluster of galaxies overlayed with contours showing the hot gas trapped in the Cluster.?Astrophysicists cannot visit clusters of galaxies to take direct measurements of the dark matter. Suppose you were asked to describe the weather today without going outside. Think of some creative ways you could estimate the wind speed, the temperature, or the amount of rain or snow from inside your house.

11 For the Classroom The picture on the left shows an optical photograph of the Coma Cluster of galaxies which is about 300 million light years from Earth. The optical image shows many individual galaxies, but that is only part of the story. By coloring in the numbers on the grid on the right according to the following code: 3 = Red, 2 = Yellow, 1 = Blue, 0 = Black you can make an X-ray image of the same region. The color code represents the brightness of the X-ray emissions due to the concentration of hot gas, from very bright (3) to none (0). The false-color X-ray image reveals the presence of vast clouds of hot gas which contain more mass than all the stars in the galaxies put together. This enormous cloud of hot gas is several million light years across. (One light year is equal to the distance light travels in a year 6 trillion miles!) Advanced Activity: How much gas is there? Assuming that the gas cloud shown above can be approximated as a sphere with a radius of 8 million light years, calculate its volume in cubic light years. Measurements with X-ray telescopes have helped estimate the mass density in the hot gas in the Coma Cluster. The average mass density for this gas is vastly smaller than Earth s average mass density. In fact, a volume of this gas with mass equal to the mass of the Earth would fill up a sphere one light year in radius! Using this information, determine how many Earths could be made with the total mass from the gas cloud above. The mass of the Earth is about percent of the mass of the Sun. How many Suns could be made with this cloud of hot gas?

12 Top Ten Amazing Facts About Chandra #1 Chandra will fly 200 times higher than Hubble - more than 1/3 of the way to the moon! #9 Chandra will be observing X-rays from clouds of gas so vast that it takes light five million years to go from one side to the other! #8 During maneuvers from one target to the next, Chandra slews more slowly than the minute hand on a clock. #7 At 45 feet long, Chandra is the largest satellite the shuttle has ever launched. #6 If Colorado were as smooth as Chandra's mirrors, Pikes Peak would be less than one inch tall! #5 Chandra s resolving power is equivalent to the ability to read the headline of a newspaper at the distance of half a mile. #4 The electrical power required to operate the Chandra spacecraft and instruments is 2 kilowatts, about the same power as a hair dryer. #3 The light from some of the quasars observed by Chandra will have been traveling through space for ten billion years. #2 STS-93, the space mission that will deploy Chandra, is the first NASA shuttle mission commanded by a woman. #1 Chandra can observe X-rays from particles up to the last second before they fall into a black hole!!!!