Interstellar Matter
Table 1 shows a breakdown of the properties of the components of the ISM of the Milky Way.
| Component | Fractional Volume |
Scale Height (pc) |
Temperature (K) |
Density (atoms/cm³) |
State of hydrogen | Primary observational techniques |
|---|---|---|---|---|---|---|
| Molecular clouds | < 1% | 80 | 10—20 | 102—106 | molecular | Radio and infrared molecular emission and absorption lines |
| Cold Neutral Medium (CNM) | 1—5% | 100—300 | 50—100 | 20—50 | neutral atomic | H I 21 cm line absorption |
| Warm Neutral Medium (WNM) | 10—20% | 300—400 | 6000—10000 | 0.2—0.5 | neutral atomic | H I 21 cm line emission |
| Warm Ionized Medium (WIM) | 20—50% | 1000 | 8000 | 0.2—0.5 | ionized | Hα emission and pulsar dispersion |
| H II regions | < 1% | 70 | 8000 | 102—104 | ionized | Hα emission and pulsar dispersion |
| Coronal gas Hot Ionized Medium (HIM) |
30—70% | 1000—3000 | 106—107 | 10−4—10−2 | ionized (metals also highly ionized) |
X-ray emission; absorption lines of highly ionized metals, primarily in the ultraviolet |
Read more about this topic: Interstellar Medium
Famous quotes containing the word matter:
“It is worth the while to live respectably unto ourselves. We can possibly get along with a neighbor, even with a bedfellow, whom we respect but very little; but as soon as it comes to this, that we do not respect ourselves, then we do not get along at all, no matter how much money we are paid for halting.”
—Henry David Thoreau (1817–1862)