What Is a Black Hole? An artist's drawing a black hole named Cygnus X-1. It formed when a large star caved in. This black hole pulls matter from blue star beside it. A black hole is a place in space where gravity pulls so much that even light can not get out. The gravity is so strong because matter has been squeezed into a tiny space. Because no light can get out, people can't see black holes. How Big Are Black Holes? Another kind of black hole is called "stellar." An artist's drawing shows the current view of the Milky Way galaxy. The largest black holes are called "supermassive." How Do Black Holes Form? Stellar black holes are made when the center of a very big star falls in upon itself, or collapses. Scientists think supermassive black holes were made at the same time as the galaxy they are in. This image of the center of the Milky Way galaxy was taken by the Chandra X-ray Observatory. Image Credit: NASA/CXC/MIT/F.K. If Black Holes Are "Black," How Do Scientists Know They Are There? Image Credit:
Black hole A black hole is defined as a region of spacetime from which gravity prevents anything, including light, from escaping.[1] The theory of general relativity predicts that a sufficiently compact mass will deform spacetime to form a black hole.[2] Around a black hole, there is a mathematically defined surface called an event horizon that marks the point of no return. The hole is called "black" because it absorbs all the light that hits the horizon, reflecting nothing, just like a perfect black body in thermodynamics.[3][4] Quantum field theory in curved spacetime predicts that event horizons emit radiation like a black body with a finite temperature. This temperature is inversely proportional to the mass of the black hole, making it difficult to observe this radiation for black holes of stellar mass or greater. Objects whose gravity fields are too strong for light to escape were first considered in the 18th century by John Michell and Pierre-Simon Laplace. History General relativity
Milky Way (chocolate bar) The Milky Way bar was created in 1923 by Frank C. Mars and originally manufactured in Minneapolis, Minnesota. The name and taste were taken from a famed malted milk drink (milkshake) of the day – not the Earth’s galaxy, as many contend.[1][2] On March 10, 1925, the Milky Way trademark was registered in the U.S., claiming a first-use date of 1922.[3] In 1924, the Milky Way bar was introduced nationally and sold USD800,000 that year. The chocolate for the chocolate coating was supplied by Hershey's.[4] In 1935 the slogan was "The sweet you can eat between meals In 2010, the Milky Way Simply Caramel bar went on sale. In 2012, Milky Way Caramel Apple Minis went on sale as a limited time offering for the Halloween season. The American Milky Way bar contains 260 Calories in each 58 gram bar, while the smaller Milky Way Midnight contains 220 Calories in each 50 gram bar and the Milky Way Simply Caramel bar contains 250 calories in each 54 gram bar.[9] List of chocolate bar brands
Milky Way Stars and gases at a wide range of distances from the Galactic center orbit at approximately 220 kilometers per second. The constant rotation speed contradicts the laws of Keplerian dynamics and suggests that much of the mass of the Milky Way does not emit or absorb electromagnetic radiation. This mass has been given the name “dark matter”.[22] The rotational period is about 240 million years at the position of the Sun.[9] The Galaxy as a whole is moving at a velocity of approximately 600 km per second with respect to extragalactic frames of reference. The oldest known star in the Galaxy is at least 13.6 billion years old and thus must have formed shortly after the Big Bang.[6] Surrounded by several smaller satellite galaxies, the Milky Way is part of the Local Group of galaxies, which forms a subcomponent of the Virgo Supercluster. Appearance[edit] The Milky Way has a relatively low surface brightness. Size and mass[edit] Schematic illustration showing the galaxy in profile
HSF > Living In Space > SPACE WEAR Astronauts wear various types of clothing for all aspects of a mission to space. Whether preparing for launch, working inside the space shuttle or the space station, working outside in space, or landing back on Earth, astronauts wear the proper garments for both comfort and protection. Space Station Clothing International Space Station crewmembers choose the shirts, shorts and pants they will wear in space months before they are scheduled to launch. Space station crews can choose from either Russian or U.S. clothing supplies. Because it's expensive to take supplies into space and there's no washing machine aboard the space station -- in order to save water -- station crews don't change clothes as often as people do on Earth. On average, station crewmembers get one pair of shorts and a T-shirt for every three days of exercising. When a piece of clothing has been worn as many times as possible, it's placed in a bag for disposal. Space Shuttle Clothing Launch and Landing
Orbits in Space Atmospheric Re-entry The Kepler formula also applies to elliptical motion, provided R is replaced by the semi-major axis a of the orbit. Over time however orbits stray from exact Keplerian ellipses because to additional forces, such as the attraction of the Moon and the Sun. Atmospheric friction also causes low-altitude satellites to re-enter, sooner or later: all these, as they lose energy, descend deeper and deeper into the atmosphere, and ultimately reach denser regions, where they burn up. Meanwhile the peak of the 11-year sunspot cycle arrived, a more active peak than NASA had hoped for, bringing a greater intensity of solar x-rays and extreme ultra-violet radiation. The Bulge of the Earth If the Earth were a perfect sphere, orbit calculations could assume that all its mass was concentrated at its center: the force, at least outside the Earth, would have been exactly the same. That modifies the orbits of satellites and must be taken into account. Lagrangian Points
Low Earth orbit A low Earth orbit (LEO) is an orbit around Earth with an altitude between 160 kilometers (99 mi), with an orbital period of about 88 minutes, and 2,000 kilometers (1,200 mi), with an orbital period of about 127 minutes. Objects below approximately 160 kilometers (99 mi) will experience very rapid orbital decay and altitude loss.[1][2] With the exception of the manned lunar flights of the Apollo program, all human spaceflights have taken place in LEO (or were suborbital). The altitude record for a human spaceflight in LEO was Gemini 11 with an apogee of 1,374.1 kilometers (853.8 mi). All manned space stations to date, as well as the majority of artificial satellites, have been in LEO. Orbital characteristics[edit] Objects in LEO encounter atmospheric drag in the form of gases in the thermosphere (approximately 80–500 km up) or exosphere (approximately 500 km and up), depending on orbit height. Equatorial low Earth orbits (ELEO) are a subset of LEO. Use of LEO[edit] Examples[edit]
How Orbits Work What an Orbit Really Is The drawings at the right simplify the physics of orbiting Earth. We see Earth with a huge, tall mountain rising from it. The mountain, as Isaac Newton first envisioned, has a cannon at the top. When the cannon is fired, the cannonball follows its ballistic arc, falling as a result of Earth's gravity, and it hits Earth some distance away from the mountain. If we put more gunpowder in the cannon, the next time it's fired, the cannonball goes halfway around the planet before it hits the ground. If you were riding along with the cannonball, you would feel as if you were falling. Getting Into Orbit The cannonball provides us with a pretty good analogy. Raise It Up (the mountain) to a high enough altitude so that Earth's atmosphere isn't going to slow it down too much. Apogee Kick How does a satellite get from low earth orbit (where the shuttle lets go of it) to geosynchronous orbit? Elliptical Orbits: most orbits are not perfectly circular. Gimme More! Questions
Neil Armstrong American astronaut and lunar explorer (1930–2012) Neil Alden Armstrong (August 5, 1930 – August 25, 2012) was an American astronaut and aeronautical engineer, and the first person to walk on the Moon. He was also a naval aviator, test pilot, and university professor. After he resigned from NASA in 1971, Armstrong taught in the Department of Aerospace Engineering at the University of Cincinnati until 1979. He served on the Apollo 13 accident investigation and on the Rogers Commission, which investigated the Space Shuttle Challenger disaster. In 2012, Armstrong died due to complications resulting from coronary bypass surgery, at the age of 82. Early life Armstrong was born near Wapakoneta, Ohio, on August 5, 1930, the son of Viola Louise (née Engel) and Stephen Koenig Armstrong. At age 17, in 1947, Armstrong began studying aeronautical engineering at Purdue University in West Lafayette, Indiana. Ensign Neil Armstrong on May 23, 1952 College years Test pilot Astronaut career Gemini program Legacy