Instruction
Next we'll look at the other table, star. This table stores details about the stars in a given constellation.
First, let's learn some basic star facts.
A light-year is an astronomical measure describing the distance traveled by light in one Julian year (365.25 days). (Remember that light travels at about 300,000 \frac{km}{s}.) The distance covered in one light-year is about 9.46 trillion (9.46 \cdot 10^{12}) kilometers or 5.88 trillion (5.88 \cdot 10^{12}) miles. In this table, the distance column uses the ly unit (1 ly is 1 light-year).
In the observation of stars, we use also the apparent (visual) and absolute magnitudes:
- The apparent magnitude (denoted by the symbol m) measures a star's brightness as seen from the Earth. The brighter an object is, the lower its magnitude. Apparent magnitude depends on the star's luminosity and its distance from Earth.
- The absolute magnitude (denoted by the symbol M) measures how bright a star would be if it were observed from a distance of 10 parsecs. (The parsec (pc) is a unit of length used in astronomy. One parsec is about 3.26 light-years).
Each star also has mass, which is described by units of solar mass (M☉); one unit of solar mass equals the mass of the Sun.
Exercise
Select all data from the table star. It contains these columns:
id– The unique internal ID of that star.name– The official name of that star.constellation_id– The constellation to which that star belongs.apparent_magnitude– The star's apparent magnitude.absolute_magnitude– The star's absolute magnitude.distance– The star's distance from our Sun, in light-years.mass– The mass of that star.temperature– The star's temperature, in Kelvin (K).
