Astronomy and related astronomical terms

(the science of the celestial bodies: the sun, the moon, and the planets; the stars and galaxies; and all of the other objects in the universe)

The astronomer said,
As he raised his cup,
"Thank heavens my business
Is looking up."
—Ennis Rees, Pun Fun;
Scholastic Book Services; New York; 1965; page 13.
solar day
The interval between two successive noons.

Since the sun is moving across the sky background at a rate of about one degree per day in an easterly direction, the solar day is slightly longer than the sidereal day; also, the sun's rate of motion varies, and it is greatest at perihelion.

The mean solar day is equal to 24 hours, 3 minutes, 36.555 seconds.

solar energy
Heat and light which is generated from the sun.

The Solar Energy Technologies Program focuses on developing cost-effective solar-energy technologies that have the greatest potential to benefit the nation and the world.

Solar technologies diversify the energy supply, reduce the country's dependence on imported fuels, improve air quality, and offset greenhouse gas emissions. A growing solar industry also stimulates the economy by creating jobs in solar manufacturing and installation.

solar system
The collective name for the sun and all the bodies that orbit around it, including the major planets, their satellites, periodic comets and the asteroids.

Its boundary could be taken as the outermost point reached by Pluto or about fifty astronomical units from the sun.

solar wind
1. A stream of charged atomic particles, mostly protons an electrons, from the sun's corona, flowing outwards at speeds of between 300 kilometers per second or 200 miles per second and 1,000 kilometers per second or 600 miles per second.
2. The stream of charged particles "blown" by the thermal pressure of the sun out from its corona, which it can not retain by gravity.

In the vicinity of the earth, these particles have a velocity of about 300 miles, or 500 kilometers, per second.

1. The moment when the sun is at its northernmost or southernmost point in the sky then it is the first day of summer or winter.

The summer solstice, when the sun is farthest north, occurs around June 21; the winter solstice takes place around December 21.

2. The point at which the sun reaches its greatest positive and negative declinations.

The referenced dates, summer solstices and winter solstices, are considered the longest and shortest days of the year, respectively.

space storms
When space weather is bad, dangerous particles abound and so space weather has become a general term for the environmental conditions above the earth's atmosphere: "Space storms include protons and ions, known as galactic cosmic rays (GRCs), raining down at near-light speed from space, and similar particles coming in bursts from the sun, called solar energetic particles (SEPs)."
space, outer space
The void that exists beyond the earth's atmosphere.

Above 120 kilometers or 75 miles, very little atmosphere remains, so objects can continue to move quickly without extra energy.

The space between the planets is not entirely empty because it is filled with the tenuous gas of the solar wind as well as particles of dust.

speckle interferometry
A technique for obtaining better images of celestial bodies by taking a series of rapid photographic exposures of the object.

This enables the effect of scintillation to be minimized.

An instrument for studying an image of the sun taken at one particular wavelength, instead of the usual mixture of wavelengths of white light.

The spectrohelioscope is a type of scanning spectroscope that enables an image of the sun to be formed by examining the sun in hydrogen light on the sun's surface and in its atmosphere.

This technique makes the arched prominences and solar flares visible which would otherwise not be seen.

A process in which the light of the sun is reflected down the tunnel by a large, driven, flat mirror at the top, open end of the tunnel.

This arrangement has two advantages in that the only moving part is the flat mirror, rather than the whole massive telescope, and the tunnel can be kept at a uniform temperature and so eliminates any thermal air current that would cause a magnified image to "boil".

1. An instrument that allows quantitative measurements to be made of spectra (splitting up of electromagnetic radiation into constituent wavelengths).
2. In optics, the arrangement according to wavelength of visible, ultraviolet, and infrared light.

An instrument designed for visual observation of spectra is called a spectroscope; an instrument that photographs or maps spectra is a spectrograph.

1. The study of spectral lines from different atoms and molecules which is an important part of studying the chemistry that goes on in stars and in interstellar clouds.
2. Any of various techniques for analyzing the energy spectra of beams of particles or for determining mass spectra.

There are many spectroscopic techniques designed for investigating the electromagnetic radiation emitted or absorbed by substances.

Spectroscopy, in various forms, is used for analysis of mixtures, for identifying and determining the structures of chemical compounds, and for investigating energy levels in atoms, ions, and molecules.

In astronomy, it is used for determining the composition of celestial objects and for measuring red shifts.

spectrum (s), spectra (pl)
1. The study of spectral lines from different atoms and molecules which is an important part of studying the chemistry that goes on in stars and in interstellar clouds.
2. The splitting up of electromagnetic radiations into the constituent wavelengths.

Atoms can exist in a number of discreet energy levels and they emit or absorb photons when they make transitions from one level to another.

The energies of the photons emitted or absorbed by one atom are different from those of all of the other atoms.

The photon energies are directly related to their frequencies, which set their colors in the spectrum, so by observing the colors of the photons, it is possible to determine which atoms are being observed.

This can be done in a laboratory, and it can also be done with the light reaching us from stars, near or distant, which enables us to identify the atoms that stars are made of.

A meteor not associated with a major meteor shower.
spring tide
The tide on the earth's surface when the effect of the moon and sun is greatest; that is, when the two bodies are in line.

This occurs at new and full moon.

Also check out the Index of other Scientific and Technological Topics.