Astronomy and space science

Astronomy and space science.

If you go to the country,far from city lights,you can see about 3,000 stars on a clearnight.If your eyes were bigger,you could see many more stars.With a pair of binoc-ulars,an optical device that effectively enlarges the pupil of your eye by about 30times,the number of stars you can see increases to the tens of thousands.With amedium-sized telescope with a light-collecting mirror 30 centimeters in diameter,you can see hundreds of thousands of stars.With a large observatory telescope,millions of stars become visible.

It would seem that when it comes to observingthe universe, the larger the instrument, the bet-ter. This is true up to a point, but there are lim-its—limits not imposed by technology but bynature itself.Surrounding Earth is a life-sustaining atmos-phere that stands between our eyes and the radi-ation that falls upon Earth from outer space.This radiation is comprised of a very broad spec-trum of energies and wavelengths. Collectively,they are referred to as the electromagnetic spec-trum. They range from radio and microwaveradiation on the low energy (long wavelength)end through infrared, visible, ultraviolet, and x-rays to gamma rays on the high energy (shortwavelength)end.Gases and other componentsof our atmosphere distort, filter, and block mostof this radiation permitting only a partial pic-ture, primarily visible radiation and some radiowaves, to reach Earth’s surface. Although manythings can be learned about our universe bystudying it from the surface of Earth, the story isincomplete. To view celestial objects over thewhole range of the electromagnetic spectrum, itis essential to climb above the atmosphere intoouter space.From its earliest days, the National Aeronauticsand Space Administration (NASA) has used theemerging technology of rockets to explore theuniverse. By lofting telescopes and other scientif-ic instruments above the veil of Earth’s atmos-phere, NASA has delivered a treasure house of information to astronomers, leading them to

rethink their most fundamental ideas about what the universe is, how it came to be, how it func-

tions, and what it is likely to become.

ASTROPHYSICS

Just a few decades ago,the word astronomy was a general term that describedthe science of the planets,moons,Sun and stars,and all other heavenly bodies.Inother words,astronomy meant the study of anything beyond Earth.Although stillan applicable term,modern astronomy,like most other sciences,has been dividedand subdivided into many specialties.Disciplines that study the planets includeplanetary geology and planetary atmospheres.The study of the particles and fieldsin space is divided into magnetospheric physics,ionospheric physics,and cosmicand heliospheric physics.The Sun has its own solar physics discipline.The originand evolution of the universe is the subject of cosmology.

Generally, objects beyond our solar system arehandled in the field of astrophysics. Theseinclude stars, the interstellar medium, otherobjects in our Milky Way Galaxy, and galaxiesbeyond our own. NASA defines astrophysics as the investigationof astronomical bodies by remote sensing fromEarth or its vicinity. Because the targets of theastrophysicist are generally beyond humanreach even with our fastest rockets, astrophysi-cists concentrate solely on what the electro-magnetic spectrum can tell them about theuniverse. NASA’s astrophysics program hasthree goals: to understand the origin and fateof the universe; to describe the fundamentallaws of physics; and to discover the nature andevolution of galaxies, stars, and the solar sys-tem. The investigations of astrophysicists arecarried out by instruments aboard free-flyingsatellites, sounding rockets that penetrate intospace for brief periods, high-flying aircraft andhigh-altitude balloons, and Space Shuttle mis-sions.