Page 17 - Curriculum Visions Dynamic Book

The birthplace of new stars: interstellar clouds
Stars were created from material scattered through space. At the end of their lives they will throw much of this material back into space. In this way the same material is used over and over again.
It is called interstellar gas and dust. When it is concentrated enough to be seen, it is called an interstellar cloud. Dust makes up about 1% of these clouds and so contains much of the heavy elements in the Universe.
The most common clouds are made from hydrogen atoms or molecules. Clouds made
from ionized gas (gas in which the particles
are charged) are less common but much more spectacular, containing flUorescent masses of gas. The hydrogen atoms break apart and become ionized when they are bombarded by Ultraviolet light (photons) from massive blue giant stars being formed within the cloud. Examples include the Orion Nebula.
constellation One of many commonly recognized patterns of stars in the sky.
evaporate The change in state from liquid to a gas. false coloUr The colours used to make the
appearance of some property more obvious.
flUorescent Emitting the visible light produced by a substance when it is struck by invisible waves, such as ultraviolet waves.
hUbble space telescope An orbiting telescope (and so a satellite) that was placed above the Earth’s atmosphere so that it could take images that were far clearer than anything that could be obtained from the surface of the Earth.
infrared Radiation with a wavelength that is longer than red light.
ionized Matter that has been converted into small charged particles called ions.
light-year The distance traveled by light through space in one Earth year, or 63,240 astronomical units.
photon A particle (quantum) of electromagnetic radiation.
space Everything beyond the Earth’s atmosphere.
Ultraviolet A form of radiation that is just beyond the violet end of the visible spectrum and so is called “ultra” (more than) violet. At the other end of the visible spectrum is “infra” (less than) red.
 This star is 25,000 light-years away in the direction of the Sagittarius constellation. It is one of the brightest stars in our galaxy, though it is normally hidden from us by cosmic dust. The picture was taken using only infrared light, which can penetrate the dust cloud. The star has a radiance of 10 million Suns.
In this picture you can also see a massive star explosion. The explosion has sent enough material into space to create two shells of gas (red colour) with a mass equal to several of our Suns. The largest shell is 4 light-years across.
This star is shedding material at a tremendous rate and may once have had a mass of 200 of our Suns.
This is a false-colour image.
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