NatureVolve

Comparing the birth of a star to a human zygote

- By Isha Parlikar

Stars

are considered to be the building blocks of galaxies. Studying the life cycle of a celestial star is central to the field of astronomy. In a galaxy, the birth of a star takes place in clouds that are scattered with dust and gases, such as the Orion Nebula.

The giant cloud that is formed as a result of the explosion of a dying star is filled with gases and dust particles from the explosion. Hydrogen gas is one of the basic components of these clouds.

Basically, due to the gravity of hydrogen atoms, they start coming closer to each other. The atoms slowly move towards the center of mass of all the atoms.

As a result, the cloud starts getting denser, allowing hydrogen atoms to interact with each other, also causing a rise in temperatur­e. At this stage, the central core is called a protostar - the name given to a very young star that is still gaining mass from parent clouds.

The young protostar was a ball of hydrogen and helium not yet powered by fusion.

Over tens of millions of years, the temperatur­e and pressure of the material inside increased, providing the source of energy for the star, just like the fusion of hydrogen that drives our Sun today.

Gravity keeps gases and dust particles together. It keeps forcing energetic interactio­ns and igniting gaseous explosions around the central core that formed this protostar. As the size of the protostar gets smaller and density increases, spinning accelerate­s. The resulting orbitting material around a central body is called an accretion disk.

Accretion in astronomy is the growth of mass of any celestial object due to its gravitatio­n. In an accretion disk, gases, dust particles, and astronomic­al objects flow in a disk-like manner around a very strong gravitatio­nal field. It loses the energy and angular momentum as it slowly spirals inward. The formation of all stars and planets involve this accretion disk.

Let’s understand the birth of star with the help of a blackhole: When massive stars die, a supernova forms. The explosion of a star is called a supernova, it’s the largest explosion occurring in galaxies.

There are two types of supernovas:

1. Binary stars, two stars orbiting around the same orbit can cause a supernova.

2. When a star runs out of its fuel it cannot support itself, causing a big explosion known as a supernova.

A supernova expands and contracts, to result in the formation of black holes. The total mass of the star collapses to a very small space which is dense and has very strong gravitatio­nal forces. This appears to be smaller than the size of the star but has strong gravitatio­nal power. After the star collapse happens, the surface of the star becomes an imaginary surface called the “event horizon”. All the material crossing the event horizon disappears for the observer due to its strong gravitatio­n pull.

Black holes have a very strong gravitatio­nal field that we cannot observe. Although everything entering a black hole vanishes for the observer, a black hole is said to have the power to give birth to a new star or planet. The strong gravitatio­n pull, circular motion, nuclear fusion events and the high temperatur­e seems to set the scene for the birth of a star.

Comparison to a human zygote

Let’s compare this to a human zygote. This is first diploid cell which eventually develops into a human being. It is the first single cell after the fertilizat­ion and fusion of male sperm and the female oocyte.

A series of events begin as the sperm enters the oocyte.

After sperm fuses with the oocyte, a pro-nucleus forms, which then migrates towards the center of the oocyte.

Every cell has to have two centrioles. The sperm contribute­s its two centrioles to the zygote, which then guides the migration of pronuclei towards the center, but it is not known what guides the centriole. Recently, researcher­s from the UK and Mexico using 3D microscopy were able to mathematic­ally reconstruc­t the movement of a sperm tail. With the help of a very fast camera, they were able to record 55,000 images in one second. Sperm motility is an important considerat­ion for fertilizat­ion success. They observed that the sperm body and tail rotate around in a swimming direction.

If we draw an axis through the sperm head, it can be seen that sperm is spinning around itself and the tilted axis rotates around center. Entire motions of sperm are considered to have a drilling effect thought fluid to achieve the destinatio­n.

Authors find similariti­es of this process with the precession of the equinoxes. Taken together, this finding hints that circular motion is responsibl­e for the birth of a star in interstell­ar

space and zygote formation inside the female womb. That brings to mind a very similar creation process on a circulatin­g potter’s wheel, or when preparing a ball of dough.

What do you think about these interestin­g connection­s?

Is there a similar event happening inside the zygote, which has to do with the spinning motion of sperm?

Is the merging of black holes similar to the merging of two pronuclei?

Nature uses similar principles again and again.

These connection­s and similariti­es can help us to understand molecular evolution. To us, natural events can seem to be similar, irrespecti­ve of scale.

Here, the principle of circular motion and conservati­on of angular momentum seem to be miraculous and astonishin­g. Patterns observed on an astronomic­al scale can be applied to microscopi­c life, and vice versa.

This helps us understand scientific connection­s hidden in our natural world.

 ??  ?? Image above: Birth of a new planet inside a black hole. © Isha Parlikar 2020.
All rights reserved.
Image above: Birth of a new planet inside a black hole. © Isha Parlikar 2020. All rights reserved.
 ??  ?? Top: Sperm approachin­g oocyte.
Directly above: Centralize­d juxtaposed pronuclear morphology in zygote.
Both images: © Isha Parlikar 2020. All rights reserved.
Top: Sperm approachin­g oocyte. Directly above: Centralize­d juxtaposed pronuclear morphology in zygote. Both images: © Isha Parlikar 2020. All rights reserved.
 ??  ?? Above: Spiral motion inside a blackhole. Left: Sperm approachin­g egg in spinning motion.
Both images:
© Isha Parlikar 2020. All rights reserved.
Above: Spiral motion inside a blackhole. Left: Sperm approachin­g egg in spinning motion. Both images: © Isha Parlikar 2020. All rights reserved.

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