The spectrum of an object can give us a lot of information, such as type of the object, radial velocity, redshift, presence of chemical elements or compounds in its atmosphere, an estimate of its distance, etc. In this article we take a look at one-dimensional spectra created by SDSS and Read more…
In a recent post I have written about a few basic concepts of the Sloan Digital Sky Survey (SDSS) and how to retrieve some data using ADQL from its servers. Now, in this post, I’m going to introduce two major kinds of objects in more depth and explain how to Read more…
The Sloan Digital Sky Survey (SDSS) is one of the greatest deep-sky surveys ever made. It has been launched by *Apache Point Observatory* in New Mexico, United States. Here, I’m going to introduce briefly some basic concepts needed to work with the rest of our tutorial. For a complete description, Read more…
Imagine a photon of light, or any type of particle, has been emitted at the first moment of beginning of the Universe, i.e, when the Big Bang happened. What is the maximum distance that this particle could have traveled to reach us at the current moment? We call this distance Read more…
What is the scale factor? One of the most important characteristics of a universe is its scale factor. Scale factor is a dimensionless function of time. Imagine the current distance between two points to be . If the universe is expanding, this value will be increased in the future. At Read more…
Hubble Constant In 1929 Edwin Hubble published an article in which he presented empirical evidence that our universe is expanding. At that time, most of the scientists believed in a static universe. After publishing Hubble’s article, Einstein called the assumption of static universe his biggest mistake. He went to Mount Read more…
Before the twentieth century, scientists didn’t know that our universe is expanding. The expansion of the universe has been discovered in 1920s and redshift played a key in this great discovery. I show you in this post what exactly redshift is by giving an example. But before explaining redshift, we Read more…