5.1 Light from the stars/stellar spectra Flashcards
What can the study of brightness and the wavelengths that are present in the particle reactions that happen inside stars?
Its temperature
Its chemical composition
The nature of the processes that are taking place to produce.
What is the luminosity of the star?
The total power (energy per second) it radiates.
What does the power radiated by each square metre of the surface of a star depends on what?
Its surface temperature.
What does the luminosity depend on?
Both the power per square metre and the surface area of the star.
What do astronomers refere to the brightness of a star as?
Its magnitude.
What are the brightest stars that are visible with the naked eye referred to as?
The first magnitude.
What are the dimmest stars that are visible with the naked eye referred to as?
The sixth magnitude stars.
What colour does most emitted energy by a cool star produce?
In the infra red region with some red light.
What colour do shorter wavelengths stars have?
They appear in hotter stars so these look yellow or increase.
The star types are labelled what?
O, B, A, F, G, K, M
The O type being the hottest.
Our sun is the G type star.
The emission spectra from stars fall into what three types?
Continuous spectra
Band spectra
Line spectra
Where continuous spectrum come from?
Hot (incandescent) bodies such as hot or molten ion.
What does a determination of where the peak of the energy in continuous spectrum give us?
The temperature of the star.
What is a line spectrum a result of?
Excitation of atoms.
Line spectra only contain certain well defined wavelengths. What do these present?
Characteristic of the element that produces the light so comparison of the starlight with a laboratory source reveals the elements in the star.
How is a band spectrum produced?
In the same way as a line spectrum but is produced by molecules. It consists of bands of light produced by a range of wavelengths separated by gaps.
What is an absorption spectrum?
When the continuous spectrum of the light from a star is analysed the spectrum contains dark light.
What is the difference between the apparent magnitude and absolute magnitude of a star?
Apparent magnitude is brightness observed at Earth.
Absolute magnitude is brightness observed at Earth if all stars at constant distance or some specified distance of 10 parsecs/32.6 light years.
Explain the conclusions that astronomers have reached about the nature of galactic mass from their measurements of the orbital speeds of the stars in a galaxy.
Mass observed does not match that required for observed orbital speed.
There must be dark matter present.
Define a light year
Distance traveled by light in 1 year
