Chapter 30 section 1 characteristics of stars pages 775-780

By: Kaylah Thomas

Characteristics of stars

• A star is a ball of gases that give off a tremendous amount of electromagnetic energy.

• Stars in the night sky appear to be tiny specks of white light.

• If you look closely at the stars in the sky, they are vary in color.

Examples of stars

• Antares- shines with a slightly reddish color.

• Rigel- shines blue-white

• Arcturus- shines with a orange tint

• A famous star is sol it is a yellow star which you see every night.

Analyzing starlight• Astronomers direct starlight through spectrographs

which are devices that separate light into different colors or wavelengths.

• Spectrum- starlight passing through a spectrograph produces a display of colors and lines called spectrum.

• There are three type of spectra; emission, or bright line, absorption or dark line: and continuous.

Continue analyzing starlight• All stars have dark line spectra bands of color

crossed by dark lines where the color is diminished.• Stars are made up of different elements in forms of

gases.• The inner layers of stars are very hot• The outer layers are somewhat cooler• Elements in the outer layers absorb some of the

light radiating from within the star. Because different elements absorb different wavelengths of light.

The compositions of stars

• Every chemical element has a characteristic spectrum in a given range of temperatures.

• The colors and lines in the spectrum of a star indicate the elements that make up the star.

• The most common element in stars is hydrogen• The most second common element is helium• Elements such as carbon, oxygen, and nitrogen,

usually in small quantities, make up most of the remaining mass of stars.

The temperatures of the stars

• The surface temperature of a star is indicated by the star's color.

• The temperature of most stars range from 2,800c to 24,000c,but some are hotter.

• Mostly a star that shines with blue light has about the average surface temperature of 35,000c.

The sizes and masses of stars• Stars also vary in size and

mass• A medium- sized star has a

diameter of about 1,390,000km.• Some giant stars have a

diameters that are 1,000 times the suns diameter.

• Many stars also have about the same mass as the sun, through some stars may be significantly more or less massive.

Distances to stars• A light year- is the

distance that light travels in one year.

• Parallax- an apparent shift in the position of the object when viewed from different locations.

• The stars and earth are measured in light years.

Stellar brightness

• Apparent magnitude- the brightness of a star seen from the earth

• Absolute magnitude- the brightness that a star would have at a distance of 32.6 light-years from earth.