## How do you find the distance to a Cepheid variable?

Through observations of Cepheid variables, astronomers have determined the distances to other galaxies. They compare the Cepheid variable’s apparent brightness with its intrinsic brightness. The difference between observed and actual brightness yields the distance.

How far out can we measure distances using Cepheid variables?

Cepheid variables can be used to measure distances out to about 30 or 40 megaparsecs with the help of the Hubble Space Telescope. There are also two different types of Cepheid variables, and these two types have different period-luminosity relationships.

What is the distance to m100?

55 million light years
Messier 100/Distance to Earth

### What must be measured to determine distance by the Cepheid variable star method?

What must be measured to determine distance by the Cepheid variable star method? The apparent magnitude of the variable star. With the 100-inch telescope, Harlow Shapley could not resolve variable stars in the more distant globular clusters of the Milky Way.

Why are Cepheid variables important for measuring distance?

The important feature of a Cepheid Variable that allows it to be used for distance measurements is that its period is related directly to its luminosity . This relation allows us to work out how much brighter than the Sun the star is. These have different relationships between their luminosity and period.

How do you calculate modulus distance?

Visual distance moduli are computed by calculating the difference between the observed apparent magnitude and some theoretical estimate of the absolute magnitude.

#### Is the sun a Cepheid variable?

Our own sun is a variable star; its energy output varies by approximately 0.1 percent, or one-thousandth of its magnitude, over an 11-year solar cycle. …

How far can Parallax measure?

Limitations of Distance Measurement Using Stellar Parallax Parallax angles of less than 0.01 arcsec are very difficult to measure from Earth because of the effects of the Earth’s atmosphere. This limits Earth based telescopes to measuring the distances to stars about 1/0.01 or 100 parsecs away.

How does a Cepheid variable work?

A Cepheid variable (/ˈsɛfiːɪd, ˈsiːfiːɪd/) is a type of star that pulsates radially, varying in both diameter and temperature and producing changes in brightness with a well-defined stable period and amplitude. This discovery allows one to know the true luminosity of a Cepheid by simply observing its pulsation period.

## What is the most distant Cepheid?

Based on the Hubble observation, the distance to M100 has been measured accurately as 56 million light-years (+/- 6 million light-years), making it the farthest object where intergalactic distances have been determined precisely.

Which is not a good distance indicator to galaxies?

Unfortunately, the most obvious properties of galaxies are not good distance indicators. Galaxies span an enormous range in luminosity, so the apparent brightness of a galaxy gives very little clue to its distance.

What is the luminosity distance formula?

More generally, the luminosity, apparent flux, and distance are related by the equation f = L/4`pi’d2. If we measure a star’s parallax and its apparent brightness, we can determine its luminosity, which is an important intrinsic property.

### How to calculate the distance to a Cepheid variable star?

They can then use the distance modulus to calculate the distance to the supernova, and the galaxy that it is in. Type Ia supernovae can be used to measure distances from about 1 Mpc to over 1000 Mpc. A Cepheid variable star has a period of 3.7 days, and from this we know its absolute magnitude is -3.1. Its apparent magnitude is 5.5.

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

How did Ejnar Hertzsprung discover the Cepheid variable star?

The Danish astronomer, Ejnar Hertzsprung (1873-1967) quickly realised the significance of this discovery. By measuring the period of a Cepheid from its light curve, the distance to that Cepheid could be determined.

#### How did Edwin Hubble determine the distance of Cepheids?

In 1924 Edwin Hubble detected Cepheids in the Andromeda nebula, M31 and the Triangulum nebula M33. Using these he determined that their distances were 900,000 and 850,000 light years respectively. He thus established conclusively that these “spiral nebulae” were in fact other galaxies and not part of our Milky Way.