NASAs Galaxy Evolution Explorer

On April 28, 2003, NASA launched the Galaxy Evolution Explorer (GALEX) from Cape Canaveral, Florida. The spacecraft is an orbiting space-based ultraviolet telescope with a mission to study the shape, brightness, size, and distance of galaxies across 10 billion years of cosmic history. The 620-pound (280-kg), three-axis stabilized spacecraft is a cylinder measuring about three feet (1 m) in diameter and is 8.2 feet (2.5 m) high. Much of the spacecraft's flight software is derived from software...

Yohkoh Spacecraft

The Japanese scientific spacecraft Yohkoh (meaning sunbeam) was an 860-pound- (390-kg-) mass, solar X-ray observation satellite launched by the Japanese Institute of Space and Astronautical Sciences on August 30, 1991. The main objective of this satellite was to study the high-energy radiations from solar flares (i.e., hard and soft X-rays and energetic neutrons), as well as quiet Sun structures and pre-solar flare conditions. Yohkoh was a three-axis stabilized observatory-type satellite that...

NASAs High Energy Astronomy Observatory

NASA's High-Energy Astronomy Observatory (HEAO) program consisted of a series of three space-based astronomy missions designed to map and image X-rays. A survey of cosmic gamma-ray sources was also performed. Between 1977 and 1979, NASA placed three different HEAO spacecraft in approximately circular orbits around Earth. These large, massive spacecraft carried equally massive scientific payloads and provided pioneering support to high-energy astrophysics and astronomy. NASA launched HEAO-1 on...

Wrinkles in the Cosmic Microwave Background

Cosmology is the study of the origin, evolution, and structure of the universe. Contemporary cosmology centers around the big bang hypothesis a theory stating that about 14 billion years ago the universe began in a great explosion and has been expanding ever since. In the open (or steady-state) model, scientists postulate that the universe is infinite and will continue to expand forever. In the more widely accepted closed universe model, the total mass of the universe is assumed sufficiently...

Gravitation

Gravitation is a force in nature every person experiences, but it has also proven to be one of nature's most mysterious and interesting phenomena. In classical physics, Newton's universal law of gravitation defines gravitation as the force of mutual attraction experienced by two masses, In 1990 the European Space Agency's Faint Object Camera onboard NASA's Hubble Space Telescope provided astronomers with a detailed image of the gravitational lens G2237 + 0305 (also called the Einstein Cross)....

Lyman Spitzer Jr and the Vision of Space Based Astronomy

In 1946, more than a decade before the launch of the first artificial satellite, the American astrophysicist Lyman Spitzer Jr. (1914-97) proposed the development of a large, space-based observatory that could operate unhindered by distortions in Earth's atmosphere. His vision ultimately became NASA's Hubble Space Telescope, which was launched in 1990. Spitzer was a renowned astrophysicist who made major contributions in the areas of stellar dynamics, plasma physics, and thermonuclear fusion, as...

Big Bang Cosmology

Modern cosmology has its roots in two major theoretical developments that occurred at the beginning of the 20th century. The first is the general theory of relativity, which Albert Einstein proposed in 1915. In it Einstein postulated how space and time can actually be influenced by strong sources of gravity. The subtle, but measurable, bending (warping) of a star's light as it passed behind the Sun during a 1919 solar eclipse confirmed that the gravitational force of a very massive object could...

Brown Dwarfs

Bluntly stated, a brown dwarf is a failed star. The brown dwarf is a celestial object that forms through the contraction and fragmentation of an interstellar cloud in much the same way that real stars form and enter the main sequence. But the big difference is that somehow, the brown dwarf never reaches the necessary critical mass. This critical size (about 0.08 solar mass, or some 80 times the mass of Jupiter) is needed to allow sufficient gravitational contraction to create the intense...

Black Holes

One of the most fascinating objects in astronomy and astrophysics is the black hole, a gravitationally collapsed mass from which nothing light, matter, or any other kind of signal can escape. Astrophysicists now conjecture that a stellar black hole is the natural end product when a giant star dies and collapses. If the core (or central region) of the dying star has three or more solar masses left after exhausting its nuclear fuel, then no known force can prevent the core from forming the...

Exploring Small Bodies in the Solar System

Just two decades ago, scientists did not have a lot of specific information about the small bodies such as comets and asteroids in the solar system. There was a great deal of speculation about the true nature of a comet's nucleus, and no one had ever seen the surface of an asteroid up close. All that changed very quickly when robot spacecraft missions flew past, imaged, sampled, probed, and even landed on several of these interesting celestial objects. This section of the chapter discusses some...

Golden Age of Solar System Exploration

Probes Nasa

The American space age began on January 31, 1958, with the launch of the first U.S. satellite Explorer 1 an Earth-orbiting spacecraft built and controlled by the Jet Propulsion Laboratory (JPL). Explorer 1 discovered Earth's trapped radiation belts and heralded the great wave of scientific discovery that would become an integral part of the Space Age. For almost five decades since the launch of Explorer 1, the JPL has led the world in exploring the solar system with robot spacecraft. The Jet...

Info

NASA's Apollo 13 mission leaves for the Moon on April 11. Suddenly, on April 13, a life-threatening explosion occurs in the service module portion of the Apollo spacecraft. Astronauts James A. Lovell, Jr., John Leonard Swigert, and Fred Wallace Haise, Jr., must use their lunar excursion module (LEM) as a lifeboat. While an anxious world waits and listens, the crew skillfully maneuvers their disabled spacecraft around the Moon. With critical supplies running low, they limp back to Earth on a...

Conclusion

In 1610 Galileo Galilei's simple optical telescope caused a revolution in observational astronomy that promoted the companion revolution in scientific thinking that transformed Western civilization. Today the detailed, multispectral study of the universe made possible by a variety of powerful space-based astronomical observatories is dramatically changing the practice of contemporary science on a short timescale that is without precedence in human history. To many scientists and nonscientists...

From Petroglyphs to The Almagest

Prehistoric cave paintings (some up to 30 millennia old) provide a lasting testament that early peoples engaged in stargazing and incorporated such astronomical observations in their cultures. Early peoples also carved astronomical symbols in stones (petroglyphs) now found at numerous ancient ceremonial locations and ruins. Many of the great monuments and ceremonial structures of ancient civilizations have alignments with astronomical significance. Some people believe one of the oldest...

Star Probe Mission

Star Probe is a conceptual robot spacecraft that can survive an approach to within about 1 million miles 1.6 million km of the Sun's surface This artist's concept shows a solar probe traveling within a million miles of the Sun. The robot spacecraft would use this visit to the nearest star to perform firsthand investigations of the physical conditions in the solar corona. The primary science objective of the solar probe is to help physicists understand the processes that heat the solar corona...