Astronomy

Astronomy is the science of observing space and the objects in it (excluding Earth). It has been studied since ancient times, forming a major part of the religions of many early civilizations such as the Egyptians and the Aztecs. The great stone henge at Stonehenge in England is also thought to be an astronomical observatory. The handing down of complex astronomical teachings shows these early civilizations must have had formalized systems of education.

Astronomy was crucial to the development of safe and accurate navigation for ships, and observations of the movement of heavenly bodies helped lead to the theories we know call physics. In fact, much of astronomy today relies physics, thus many astronomers are considered astrophysicists.

Recent research

Astronomers have searched for ways to find out accurately how old a star is. A new technique called gyrochronology, which works this out based on the star’s rate of rotation, has just been announced and will be published in the Astrophysical Journal. Knowing the age of the host star of a planetary system helps astronomers understand how planetary systems change over time.

The research shows that the rotation period of a star changes steadily and predictably in line with its age and color. Thus, by measuring two of these attributes you can determine the third. The star’s color is a visible sign of its mass or surface temperature. The age of the Sun is known (4.6 billion years) and can be used to calibrate the gyrochronology of most other stars.

There are other methods of working out a star’s age, but they have much larger uncertainties than gyrochronology. Unlike some other methods, gyrochronology also works well for stars not found in star clusters (‘field’ stars). It is used to calculate the age of stars that burn their hydrogen fuel at a predictable and steady rate; it does not work so well for younger stars, although the researchers hope to do future work to extend the method to these.

The forthcoming NASA Kepler Mission will yield more information about the rotation period of other stars, as this is information gleaned while searching for the transit of new planets orbiting across their disks. Once researchers have more precise ages for stars, other problems of chronometry can be solved and a better study made of the way astronomical phenomena change through time, using the stars themselves as clocks.

EXTERNAL LINKS

The NASA Homepage
The NASA Planetary Photojournal
American Astronomical Society
British Astronomical Association
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