April 11, 2000
Somewhere between the hydrogen and the starlight, between the gravity and the grace, the universe conspired to bring you into being.
The Local Interstellar Cloud
Birthday · April 11, 2000
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APOD published April 11, 2000. Credit: Linda Huff (American Scientist), Priscilla Frisch (U. Chicago). A publication-date match, not a photo taken on your date. Independent of NASA.
The stars are not alone. In the disk of our Milky Way Galaxy about 10 percent of visible matter is in the form of gas, called the interstellar medium (ISM). The ISM is not uniform, and shows patchiness even near our Sun. It can be quite difficult to detect the local ISM because it is so tenuous and emits so little light. This mostly hydrogen gas, however, absorbs some very specific colors that can be detected in the light of the nearest stars. A working map of the local ISM within 10 light-years based on recent observations is shown above. These observations show that our Sun is moving through a Local Interstellar Cloud as this cloud flows outwards from the Scorpius-Centaurus Association star forming region. Our Sun may exit the Local Interstellar Cloud during the next 10,000 years. Much remains unknown about the local ISM, including details of its distribution, its origin, and how it affects the Sun and the Earth.
Image credit: Linda Huff (American Scientist), Priscilla Frisch (U. Chicago)