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 luminosity of a star with a period of 30 days?
Thus a 3-day period Cepheid has an absolute V-band magnitude of −3.1, while a 30-day period Cepheid has an absolute V-band magnitude of −5.3.
What is Levitt’s law?
It took years for the mostly-male astronomy community to realize that this relationship (today known as “the Leavitt Law”) means that measuring the period of a Cepheid variable immediately gives its true brightness — and furthermore, that comparing this to its apparent brightness immediately gives its distance.
What is meant by the period-luminosity relationship of Cepheid variables explain how this can be used to measure distances?
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.
What is the period-luminosity relationship quizlet?
The period-luminosity relationship discovered by Henrietta Leavitt for Cepheid variable stars, relating variability to over-all brightness says that. the shorter the period, the lower the luminosity of the star. The event that settled the debate between Curtis and Shapley about the ‘spiral nebulae’ was.
What is Leavitt’s Law quizlet?
Leavitt’s Law is the relation, discovered by Henrietta Leavitt, that describes how the luminosity of a Cepheid variable star is related to the period between peaks in its brightness: the longer the Cepheid’s period, the more luminous the star.
How is luminosity calculated?
A star’s luminosity, which is how much energy is emitted per second from the star, is measured in Watts or in solar luminosities (L⊙) where 1L⊙ = 3.85 x 1026 Watt. We determine a star’s luminosity by measuring its distance and its apparent brightness, which we call its apparent magnitude.
What does Hubble’s law tell us?
Hubble’s law, which says simply that a galaxy’s velocity (or as is sometimes plotted, its redshift) is directly proportional to its distance, also tells us something important about the state of the universe. If the universe is static and unchanging, there should be no correlation between distance and velocity.
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.
How can we determine the luminosity of a Cepheid variable star?
This discovery allows one to know the true luminosity of a Cepheid by simply observing its pulsation period. This in turn allows one to determine the distance to the star, by comparing its known luminosity to its observed brightness.
Why is the period-luminosity relationship important quizlet?
Henrietta Swan Leavitt discovered the period-luminosity relationship. This relationship is critical because it tells us the longer the pulsation period, the more luminous the star.
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.
What is the period-luminosity relation?
The Period-Luminosity relation. The absolute magnitude of a star, M v, is defined to be the apparent brightness of a star when the star is at a distance of 10 pc (32.6 light years). The difference between the apparent magnitude and absolute magnitude provides (almost) enough information to calculate the distance to the star.
Why did Leavitt use the period-luminosity relation?
Because all of the Cepheids in a Magellanic Cloud are at the same distance from us, Leavitt reasoned that the more luminousCepheids pulsated more slowly. This is the period-luminosity relation. Leavitt did not know the distances to the Magellanic Clouds, so she could not tell what the actual value of the luminosity part of the relation was.
What is the relationship between apparent magnitudes and relative luminosity?
Since all the stars are in the LMC, and are at the same distance from us, the apparent magnitudes are an accurate measure of the true relative luminosities of the stars. She found a relation similar to that shown in Figure 7.
Can we calibrate the period-luminosity relation using Galactic calibration?
Calibrating the period-luminosity relation has been problematic; however, a firm Galactic calibration was established by Benedict et al. 2007 using precise HST parallaxes for 10 nearby classical Cepheids.