What is the relationship between luminosity and period?
What is the relationship between luminosity and period?
In astronomy, a period-luminosity relation is a relationship linking the luminosity of pulsating variable stars with their pulsation period. The best-known relation is the direct proportionality law holding for Classical Cepheid variables, sometimes called the Leavitt law.
What is the relationship between the brightness and period for Cepheid Variable stars?
As Henrietta Swan Levitt discovered, a Cepheid’s variability period relates directly to its luminosity. The longer the variability period, the more luminous the Cepheid. Through observations of Cepheid variables, astronomers have determined the distances to other galaxies.
Why is period-luminosity relationship important?
Because the luminosity of Cepheids can be easily found from the pulsation period, they are very useful in finding distances to the star clusters or galaxies in which they reside.
How do you find the luminosity of a Cepheid Variable?
Using Cepheid Variables to Measure Distance Once the period of a distant Cepheid has been measured, its luminosity can be determined from the known behavior of Cepheid variables. Then its absolute magnitude and apparent magnitude can be related by the distance modulus equation, and its distance can be determined.
Who discovered the period-luminosity relationship?
Henrietta Leavitt
galaxies. …he made use of the period-luminosity (P-L) relation discovered by Henrietta Leavitt of the Harvard College Observatory.
What is a good range for the period of Cepheid variables?
Several hundred cepheid variables are known in our Galaxy. Most cepheids have periods in the range of 3 to 50 days and luminosities that are about 1000 to 10,000 times greater than that of the Sun. Their variations in luminosity range from a few percent to a factor of 10.
What type of stars have longer periods 2 to 60 days?
Cepheid variables have the following properties: Period = 2 to 60 days.
Why do galactic disks appear blue?
The disks appear bluer because they are the site of ongoing star formation. Massive stars are very bright and very hot, which gives their light a blue color, but they also have very short lifetimes by stellar standards. Only the smaller, cooler stars remain giving these galaxies a red color.
Why do Cepheids pulsate?
Pulsating variable stars are intrinsic variables as their variation in brightness is due to a physical change within the star. In the case of pulsating variables this is due to the periodic expansion and contraction of the surface layers of the stars.
What is responsible for the pulsation cycle of Cepheid variables?
What is special about Cepheid variable stars?
Cepheids Variables are special type of variable star in that they are hot and massive – five to twenty times as much mass as our Sun – and are known for their tendency to pulsate radially and vary in both diameter and temperature.
Which star takes longer to pulse?
star A-091 take longer to pulse than the other star. 2. Because both stars are in the same galaxy, they are about the same distance from Earth.
How is the luminosity of a Cepheid related to its period?
Some types of pulsating variable stars such as Cepheids exhibit a definite relationship between their period and their intrinsic luminosity. Such period-luminosity relationships are invaluable to astronomers as they are a vital method in calculating distances within and beyond our galaxy. Discovery of the Period – Luminosity Relationship
Can a Cepheid be used as a standard candle?
Alternatively if M is known (for Cepheids from the PL relation) then the distance to the object can be found. Once the PL relationship is calibrated, i.e. the absolute magnitude versus period relation is known, Cepheids can be used as standard candles.
Why are Cepheid variable stars important to astronomers?
Cepheid variable stars are crucial tools to measure galaxy distances and hence the determination of the Hubble constant. They are named after the prototype, the 4th magnitude star δ Cephei. They are pulsating variable stars that over their period change in radius, surface temperature and brightness.
What kind of period does a Delta Cepheid have?
Classical Cepheids (also known as Population I Cepheids, type I Cepheids, or Delta Cepheid variables) undergo pulsations with very regular periods on the order of days to months.
