GC 4889 is the largest galaxy in the Coma Cluster (shown in the image below taken by the Hubble Space Telescope). After analyzing the spectrum of NGC 4889, an astronomer identifies a spectral line as being CaII (singly ionized Calcium) with a measured wavelength of 401.8 nm. The true, rest wavelength of this spectral line, measured in a lab, is 393.3 nm. a) What would be this galaxy’s recessional velocity, in km/s? b) Using a Hubble constant of ?0 = 70 km/s/Mpc, find the distance to this galaxy cluster. Give your answer in megaparsecs and in light-years.
Stellar evolution
We may see thousands of stars in the dark sky. Our universe consists of billions of stars. Stars may appear tiny to us but they are huge balls of gasses. Sun is a star of average size. Some stars are even a thousand times larger than the sun. The stars do not exist forever they have a certain lifetime. The life span of the sun is about 10 billion years. The star undergoes various changes during its lifetime, this process is called stellar evolution. The structure of the sun-like star is shown below.
Red Shift
It is an astronomical phenomenon. In this phenomenon, increase in wavelength with corresponding decrease in photon energy and frequency of radiation of light. It is the displacement of spectrum of any kind of astronomical object to the longer wavelengths (red) side.
The elliptical galaxy NGC 4889 is the largest galaxy in the Coma Cluster (shown in the image below taken by the Hubble Space Telescope). After analyzing the spectrum of NGC 4889, an astronomer identifies a spectral line as being CaII (singly ionized Calcium) with a measured wavelength of 401.8 nm. The true, rest wavelength of this spectral line, measured in a lab, is 393.3 nm.
- a) What would be this galaxy’s recessional velocity, in km/s?
- b) Using a Hubble constant of ?0 = 70 km/s/Mpc, find the distance to this galaxy cluster. Give your answer in megaparsecs and in light-years.
- c) How would your answer to part b) differ if the Hubble constant had a smaller value? A larger value? Explain.
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