Astronomy
- The study of the objects that lie beyond Earth and the process by which these objects interact with one another
- My definition: The study of celestial objects beyond Earth and how they interact with one another.
- An observational science
- Rarely setup traditional experiments
- Any hypotheses must be tested by observing many samples of the objects being studies
- We note how different samples vary
- Light is basically the only information we have access to
Resources
Useful Constants
Physical Constants
| Name | Value |
|---|---|
| speed of light ($c$) | $2.9979 \times 10^8 m/s$ |
| gravitational constant ($G$) | $6.674 \times 10^{-11} m3/(kg s^2)$ |
| Planck’s constant ($h$) | $6.626 \times 10^{−34} J-s$ |
| mass of a hydrogen atom ($M_H$) | $1.673 \times 10^{−27} kg$ |
| mass of an electron ($M_e$) | $9.109 \times 10^{−31} kg$ |
| Rydberg constant ($R \inf$) | $1.0974 \times 10^7 m^{−1}$ |
| Stefan-Boltzmann constant (σ) | $5.670 \times 10^{−8} J/(s \times m^2 deg^4)$ |
| Wien’s law constant ($\lambda \max T$) | $2.898 \times 10^{−3} m K$ |
| electron volt (energy) ($eV$) | $1.602 \times 10^{−19} J$ |
| energy equivalent of 1 ton TNT | $4.2 \times 10^9 J$ |
Astronomical Constants
| Name | Value |
|---|---|
| astronomical unit ($AU$) | $1.496 \times 10^{11} m$ |
| Light-year ($ly$) | $9.461 \times 10^{15} m$ |
| parsec ($pc$) | $3.086 \times 10^{16} m = 3.262 light-years$ |
| sidereal year ($y$) | $3.156 \times 10^7 s$ |
| mass of Earth ($M_{Earth}$) | $5.974 \times 10^{24} kg$ |
| equatorial radius of Earth ($R_{Earth}$) | $6.378 \times 10^{6} m$ |
| obliquity of ecliptic | $23° 26’$ |
| surface gravity of Earth ($g$) | $9.807 m/s^2$ |
| escape velocity of Earth ($v_{Earth}$) | $1.119 \times 10^4 m/s$ |
| mass of Sun ($M_{Sun}$) | $1.989 \times 10^{30} kg$ |
| equatorial radius of Sun ($R_{Sun}$) | $6.960 \times 10^8 m$ |
| luminosity of Sun ($L_{Sun}$) | $3.85 \times 10^{26} W$ |
| solar constant (flux of energy received at Earth) ($S$) | $1.368 \times 10^3 W/m^2$ |
| Hubble constant ($H_0$) | approximately 20 km/s per million light-years, or approximately 70 km/s per megaparsec |