Team Brahmanda’s Journey at Incubate Nepal

Image: Cool pose of team Brahmanda. Top left to Bottom corner: Aabiskar Thapa Kshetri, Bibek Pandit, Priya Shrestha, Mahesh Yadav, Anupa Khanal, Anish Giri

The Big Picture

The Universe is simply everything we can feel, sense, or detect, including us, other living beings, planets, stars, galaxies, and all the different forms of matter and energy. It began to expand 13.8 billion years ago and has continued to expand ever since.

Universe: a balloon

Universe expands like a balloon. Each point on the universe is moving away from each other like in the balloon.

You can’t see me!

So, what’s the matter with dark matter? The Universe is full of exhilarating mysteries, and ‘Dark Matter’ is no stranger to it. Dark matter is the term given to non-luminous mass whose presence is presumed from the gravitational effects. By non-luminous, it means something that does not interact with electromagnetic radiation making it “invisible”. The story of Dark matter started when a Swiss astronomer, Fritz Zwicky, detected a phenomenon, which would later change how we see the Universe. In 1933, while trying to calculate the mass of the Coma cluster using two methods: rotation curves and mass-luminosity ratio, he found that the average mass of the cluster measured from rotational curves was about 100 times more than the expected mass calculated from Mass-light ratio. Staggering, isn’t it? Thus, he termed the phenomenon as ‘Dunkle Materie’, a German word later translated as ‘dark matter’.

Hold on my beer! I am the cause.

Dark energy is the name given to the cause of a bizarre phenomenon accelerating the Universe’s expansion. So hypothetically, it is some sort of energy intrinsic to space which has anti-gravitational effects. Since we don’t know much about it, there are different assumptions regarding the obsolete expansion of the Universe. The idea of the cosmological constant is one hypothesis, while there are lots and lots of speculations on this. Some even argue that it might be some property of the space itself caused by the outward pressure caused during vacuum field fluctuation. On the one hand, these mysteries are so distressing; on the other hand, these are the frontier of cosmology. There are so many things about the scaffolds of these peculiar things yet to be unveiled. It makes young physics enthusiasts, like us, fascinated by these sorts of mysteries.

I decide the Universe’s fate!

Friedmann’s equation without cosmological constant
Tug war between expansion and gravity

How can you forget me? I am omnipresent.

Cosmic Microwave Background Radiation

Our earlier expectations

After we spent the first few weeks learning equations and understanding the concepts, we had to search for the exact data to estimate the density of dark matter. We chose to study M31 (Andromeda galaxy) in-depth to understand the distribution of dark matter throughout its volume and generalise later to the whole universe. We had expected that the statistical dispersion of the velocities of the mean velocities of star clusters in the galaxy can help us derive the mass of the cluster using the Virial theorem. The virial theorem relates the total kinetic energy with the potential energy of a system. To make our research accurate, we also decided to follow X-ray emission methods.

Our current work in brief

Since the method we chose didn’t seem to work out, we did a review of research works that does the study of the density profile in the andromeda galaxy. Yet again, we had to go through bulks of paper and, at the same time, work on the data extraction and plotting. So, we divided our tasks according to our knowledge and skills in different fields. It helped us achieve more in a shorter time. We extracted data from those papers and plotted the graph of mass VS radius and velocity VS radius graph. We also plotted a new density profile graph of both luminous and non-luminous matter with the help of the mass-radius profile we obtained. We then hypothesized a ratio of stellar mass and non-luminous mass of M31 to assume a general ratio of densities of observable and non-observable matter throughout the universe. We are working to create a review research paper that sums up all the things we have done in this project.

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