Galactic Neighbours

Galaxies containing billions of stars, wandering in different directions of the sky. Residing in the Milky Way, we can not see our home galaxy but other ones for sure! Like our neighboring galaxy Andromeda, M31. Isn’t it look beautiful?

Andromeda is double in the size and age of Milky Way. There exist even bigger and older galaxies, just need to seek deeper in the space and you will find many. Seeing all these chaos, I feel lost sometimes and wish to make a map of my neighborhood. For that, measuring distances to galaxies seems right thing to do, but how to proceed further?

Sit and observe the night sky. Observe for weeks and take pictures of night sky. On comparing such pictures, it was found that some star changes brightness periodically. One of the first such star observed in consellation Cephus, in 1784, hence the family of such stars are named as Cephied variables. While developing a catalog of variable stars, in 1908, Henry Leavitt noticed a correlation between changing brightness and respective pulsating period of Cepheids, i.e. Cepheid of longer period are brighter. The linear equation correlating intrinsic brightness of Cepheid with their period is known as Leavitt Law. It is one of the most robust method to find distances to galaxies, provided they host Cepheid variables.

Research Work

I am refining a century old equation to achieve more reliable measurement of distances to galaxies. New technology and high standard data from space-based telescope opens up possibility to gain more accuracy in distance measurement. Focusing on Cepheids residing in the Milky Way, my goal is to determin the systematic errors in emperical Leavitt Law using multiband photometry data and pre-determined distances from Gaia satellite. Upon comparing the zero-point of calibrated Galactic Leavitt Law with the Leavitt Law of other galaxies, distance can be determined by simply calculating the difference in zero-points of respective galaxy. With distance, galaxies can be located in the space map, giving me an idea about where do we reside.