STARS...

History of Observations

Astronomy, the study of the heavens, may be the most ancient of the sciences, present since the dawn of recorded civilization, with the stars often playing a key role in religion and proving vital to navigation. The invention of the telescope and the discovery of the laws of motion and gravity in the 17th century prompted the realization that stars were just like the sun, all obeying the same laws of physics. In the 19th century, photography and spectroscopy — the study of the wavelengths of light that objects emit — made it possible to investigate the compositions and motions of stars from afar, leading to the development of astrophysics. In 1937, the first radio telescope was built, enabling astronomers to detect otherwise invisible radiation from stars. In 1990, the first space-based optical telescope, the Hubble Space Telescope, was launched, providing the deepest, most detailed visible-light view of the universe.

Star Naming Designations

Ancient cultures saw patterns in the heavens that resembled people, animals or common objects — constellations that came to represent figures from myth, such as Orion the Hunter, a hero in Greek mythology. Astronomers now often use constellations in the naming of stars, with the International Astronomical Union, the world authority for assigning names to celestial objects, officially recognizing 88 constellations that cover the entire sky. Usually, the brightest star in a constellation is has "alpha," the first letter of the Greek alphabet, as part of its scientific name. The second brightest star in a constellation is typically designated "beta," the third brightest "gamma," and so on until all the Greek letters are used, after which numerical designations follow.

Since there are so many stars in the universe, the IAU uses a different system for newfound stars. Most consist of an abbreviation that stands for either the type of star or a catalog that lists information about the star, followed by a group of symbols. For instance, PSR J1302-6350 is a pulsar, thus the PSR. The J reveals that a coordinate system known as J2000 is being used, while the 1302 and 6350 are coordinates similar to the latitude and longitude codes used on Earth.

A number of stars have possessed names since antiquity — Aldebaran, for instance, means "the follower" in Arabic, as it seems to follow the Pleiades, or Seven Sisters star cluster, across the sky. These possess scientific names as well — Aldebaran is also known as Alpha Tauri.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Characteristics

• Brightness

Astronomers describe star brightness in terms of magnitude and luminosity.— the brightest star in the night sky is Sirius, with an apparent magnitude of -1.46

• Color

Stars come in a range of colors, from reddish to yellowish to blue. The color of a star depends on surface temperature.

• Size

Astronomers generally measure the size of stars in terms of the radius of our sun. For instance, Alpha Centauri A has a radius of 1.05 solar radii (the plural of radius). Stars range in size from neutron stars, which can be only 12 miles (20 kilometers) wide, to supergiants roughly 1,000 times the diameter of the sun.

• Mass

Astronomers represent the mass of a star in terms of the solar mass, the mass of our sun. For instance, Alpha Centauri A is 1.08 solar masses.

Stars with similar masses might not be similar in size because they have different densities. For instance, Sirius B is roughly the same mass as the sun, but is 90,000 times as dense, and so is only a fiftieth its diameter.