30 May 2023

a protostar is a celestial object in formation that precedes becoming a star. It is created from a collapsing molecular cloud, its evolution dependent on its mass and size. During its emergence, it is surrounded by a pocket of gas and dust, as it evolves, this cover disperses and the protostar becomes a star. Understanding these is important to understanding the creation of celestial bodies and planets in the universe.

In this article we will fully explain what a protostar is, how it is formed, how it is formed, its characteristics and more curiosities that are related to it.

Concept of a protostar

It is an early phase of the formation of a star. It is generated from a giant molecular cloud of gas and dust in space, which contracts under the force of gravity.

the protostar results from the contraction of the molecular cloud, which is caused by a large amount of heat and pressure in its core. This causes it to begin to shine and emit infrared radiation, although it has not yet reached the temperature and pressure necessary to begin nuclear fusion at its core and become a full star.

During this phase, the protostar it continues to contract and accumulate material. Which increases their degrees and internal tension. If the protostar is massive, it will reach the necessary temperature and pressure. In such a way that it will initiate nuclear fusion in its nucleus. This also happens in a similar way with planets, so stars and planets grow simultaneously.

How is a protostar formed?

His physical formation begins with a giant molecular cluster composed of gas and dust in interstellar space. These can be several light-years in size and have a volume thousands of times the mass of the Sun.

Gravity is the main factor that causes the contraction of the molecular cluster, which begins to collapse in on itself. As it contracts, its temperature increases due to increased pressure at the cloud’s core, which in turn increases the velocity of its component particles.

This shrinking process continues until a dense central structure is formed, called the protostellar nucleus, surrounded by a disk of material that rotates around its center. In this, the element begins to clump together into small particles that will come together to form planets.

The protostellar center is kept warm due to gravitational energy released by contraction and reaches several thousand degrees Celsius. This high temperature generates infrared radiation. That can be detected by telescopes and astronomical observatories.

During the formation phase of the protostar, the contraction of the molecular cloud equilibrates with thermal pressure generated by the heat of the protostellar core. This process can take up to several hundred thousand years, depending on the mass of the cluster and the rate of contraction.

How is a protostar formed?

It is created from a giant molecular clump of gas and dust in interstellar space. These are made up of molecular hydrogen. It also contains small amounts of other elements such as helium, carbon, oxygen and nitrogen, and dust particles.

The gas and dust in the molecular cloud begin to contract under the influence of gravity, forming a dense structure in the center that will become the protostellar nucleus. As the cluster contracts, its temperature increases due to increased pressure in the center of the cloud, which in turn increases the speed of the particles that compose it.

The material in the protoplanetary disk surrounding the protostellar nucleus It is made up of dust and ice. that is formed from the gas and agglutinate in larger and larger particles. These can come together to generate planets, moons, and other celestial bodies.

In addition to the items mentioned, molecular clouds they can also contain complex molecules. Like water, ammonia, methanol and carbon dioxide. They participate in the formation of planets and other celestial bodies, they are also detected by telescopes and astronomical observatories.

What is the difference between a protostar and a star?

The main variation is that the protostar hydrostatic equilibrium has not yet reached while a star has reached it.

The protostar is an early stage in the formation of a celestial body. During this phase, the giant molecular cloud that gave rise to the protostar has begun to contract under the influence of gravity, and a hot protostellar core has formed surrounded by a disk of material that It can lead to the formation of planets.

The protostar continues to contract and heat up. Until the temperatures and densities necessary for initiate nuclear fusion in its atomic nucleus.

On the other hand, a star is a sphere of gas in hydrostatic equilibrium, in which the gravitational force acting on the gas is balanced by the thermal pressure caused by nuclear fusion in its core. In a star, the fusion of hydrogen into helium creates energy that radiates into space as light and heat, keeping the celestial body warm and stable for long periods of time.

Another important difference is their brightness. A protostar emanates light in the infrared band due to its high temperature. Whereas a star emits light in a wide range of wavelengths. Also depending on their grades and chemical composition.

What are the characteristics of a protostar?

Scientists through DOI reports clarify that the characteristics may vary depending on their size, mass and other environmental conditions, but in general, a protostar is characterized by:

  • High temperature: It can reach several thousand degrees Celsius, due to the heat generated by the gravitational contraction of the molecular cloud.
  • Infrared Glow: The Protostar emits most of its energy in the form of infrared radiation, due to its high temperature. This is detected by specialized telescopes.
  • Protoplanetary disk formation: The protostar is surrounded by a disk of material which can lead to the creation of planets, satellites and other celestial bodies. These are formed by dust and ice, which clump together into larger and larger particles.
  • Gravitational contraction: It continues to contract under the influence of gravity. Increasing your concentration and degrees in the process.
  • Incipient nuclear fusion: In the advanced stages of formation, the temperature and density in its core can reach values ​​sufficient to start the nuclear fusion of hydrogen into helium. Generating the energy that will be emitted by the star.
  • High rate of matter accretion: The protostar continues attracting elements from the surrounding molecular cloud, increasing its volume and size. This can happen until the protostar reaches a critical mass and nuclear fusion begins.

How many types of protostars are there?

There are several categories, classified according to their emission spectrum and other observational features. The two main classes of protostars are:

  • Class 0 Protostars: They are the youngest and least evolved. They are characterized by having a very low luminosity, emitting at millimeter and submillimeter wavelengths, and being surrounded by a thick envelope of gas and dust. They are often associated with objects known as ‘protostar cores’, which are dense regions of gas and dust that contract under the influence of gravity.
  • Class I Protostars: They are more advanced protostars than the previous category, these have begun to clear their envelope of gas and dust as they continue to contract. They are characterized by greater luminosity, they emit in the infrared band and are surrounded by a protoplanetary disk. They are often called ‘Herbig Ae/Be objects’ for more massive stars, or ‘Class I protostars’ for lower mass celestial bodies.

In addition to these two categories, there are also some subclasses. Such as ‘transitional’ protostars that are in the process of transitioning from Class 0 to Class I. There are also ‘out-of-class’ protostars, which have atypical properties compared to Class 0 and I.

In general, its classification is based on its emission spectrum, luminosity, gas and dust envelope, and the presence of a protoplanetary disk. These characteristics help us to better understand the development of stars and the physical processes that are linked in the formation of planetary systems.

How is the evolution of protostars?

This depends on its mass, size and the environmental conditions in which it is found. In general, the evolution of a protostar It can be divided into several main stages:

  • Contraction stage: In this phase, a molecular cloud contracts under the influence of gravity forming a protostar at its center. The temperature and density at its core increase as it continues to contract.
  • Class 0 protostar stage: During this period, the protostar It is surrounded by a dense envelope of gas and dust. The luminosity of this is very low, since the energy released by the gravitational contraction is dissipated in the surrounding environment. The protostar emits radiation at millimeter and submillimeter wavelengths.
  • Class I protostar stage: As the protostar continues to contract, its envelope of gas and dust begins to disperse, allowing radiation to escape. This emits infrared radiation and is surrounded by a protoplanetary disk, from which planets and other celestial bodies can form.
  • Class II protostar stage: During this cycle, the protostar it has cleared most of its envelope of gas and dust. Its luminosity has increased considerably. The protostar emits radiation in the near infrared band and has become a pre-main sequence star.
  • Main Sequence Star Stage: Eventually, the protostar reaches a mass and temperature sufficient for nuclear hydrogen fusion to begin at its center. The star becomes a main sequence celestial body. in which nuclear fusion in the core keeps the star in hydrostatic equilibrium.

Examples of protostars

There are several known models that roam the entire universe. Here are some of the most popular and distinguished:

  • IRAS 16293-2422: It is located at a distance of 400 light years from Earth in the constellation Ophiuchus. It is known to be surrounded by a protoplanetary disk and is a very young object at the Class 0 stage.
  • HH 212: It is located about 1,300 light years away in the constellation Orion. It is characterized by its well-developed protoplanetary disk and by its jets of gas and dust emerging from the protostar. It is believed to be in the Class I stage.
  • L1527: It is located about 450 light years away in the constellation Perseus. It has a very well developed protoplanetary disk and is in the Class I stage.
  • TMC-1A: It is found in the Taurus molecular cloud, about 450 light years from Earth. It is characterized by its gas and dust envelope and is in the Class 0 stage.

These are just a few examples of known protostars in the universe. With the advancement of technology and observation techniques, many more are expected to be discovered in the future.

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