Station 2: The Cosmic Cycle of Matter

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The bright blue objects at the top of the picture are stars and regions of hot gas. The brown-gold darker regions at the right and the bottom are cool clouds of dust and gas from which new stars are made. Atoms and molecules can move between the two regions.

From the diffuse medium between stars, matter gathers in a dense interstellar cloud that collapses and forms new stars, which later return their substance to interstellar space. Nuclear processes within the stars change the elemental makeup from its initial composition to the legacy materials bequeathed to the Universe upon stellar death.

Some Elements are Older than Others

BUILDING THE ELEMENTS: The elements grew in number after the Big Bang. About 100 elements occur naturally, but many are rare. Hydrogen (H) is the most common and it plays a major role in biology.

The elements on the periodic table make up all that you can see around you today, including stars and other objects in outer space. Hydrogen, carbon, oxygen, nitrogen, sulfur and phosphorus are some of the more abundant elements in biological organisms. Rarer, but biologically important, elements include iron, copper, zinc and iodine.


The icon at the top of this station is known as the “periodic table,” a special arrangement of all the elements found in nature, here colorcoded to show the manner in which they were made. The protruding pegs highlight elements found in DNA. On the reverse side, the most abundant elements used in human biology are highlighted.


The dark object at left is a Bok Globule. At right is the Horsehead Nebula, a cold interstellar region of gas and dust in front of hot clouds of hydrogen atoms (red light). The horsehead is about 4 light years (38,000,000,000,000 kilometers) in size, from top to bottom.


Huge interstellar clouds of dust particles and gas can form between the stars. In the cold cores of dense clouds, a rich chemistry develops as atoms combine to form molecules. The star-forming region (“core”) is a hot and turbulent place where energetic radiation abounds as X-rays and ultraviolet light. This energy fuels a rich and diverse chemistry that extends the formation of complex organic molecules begun in the interstellar cloud. The legacy chemicals found in primitive Solar System materials reveal this mixed heritage. Astronomers have identified more than 120 kinds of molecules in such clouds. Simple molecules can be made in space either as a gas or on dust grains, and those simple molecules evolve into even more complicated ones through processes studied by scientists of the Goddard Center for Astrobiology. Most of the atoms in your body are bound up in molecules.

We Study Chemistry in Space

Members of the Goddard Center for Astrobiology use sophisticated equipment to study the atoms and molecules in outer space between stars, around stars, on planets and moons, and on comets an asteroids. We identify them by the light the absorb or emit at X-ray, ultraviolet, visual, infrared or radio wavelengths. Our laboratory scientists study how cosmic rays and higih-energy light can both make and destroy moelcules, including those with biological roles.

The calcium in your bones and the iron in your blood were made in stars. Also, some of the molecules made in the cold birth cloud of our Solar System are preserved in comets and carbonaceous meteorites.

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