The main sequence has a lower mass limit because stars below a certain mass, known as brown dwarfs, do not contain enough mass for hydrogen fusion to take place in their cores. Accordingly, these objects are not able to sustain the energy generation process necessary to exist as stars on the main sequence.
The lower mass limit is around 0. 08 solar masses, or approximately 80 times the mass of Jupiter.
In summary, the main sequence has a lower mass limit because, below that mass, the internal pressure and temperature necessary to sustain nuclear fusion of hydrogen in the star’s core cannot be achieved.
Why is there a lower limit to the mass of a main sequence star?
The lower limit to the mass of a main sequence star is due to a balance of several important elements in the star’s makeup. Every main sequence star needs enough mass and pressure inside it to overcome gravitational compression and initiate nuclear fusion.
The amount of mass and pressure required is dependent on the temperature at the core of the star. With too little mass, the temperature inside the star would be too low for nuclear fusion to begin.
In terms of temperature, there’s also a lower limit. If the temperature drops too low, then the energy created by nuclear fusion wouldn’t be enough to limit gravity’s collapse. The star would start to contract and become even denser and hotter.
At this stage, it would be recovering nuclear fuel with extreme efficiency, creating a star that’s too hot, too massive, and too luminous to remain on the main sequence.
Therefore, the lower limit to the mass of a main sequence star is critical in that it’s the amount of mass needed to maintain the perfect balance between the temperature of the star, the rate of nuclear fusion, and the gravitational compression exerted by its mass.
Without a minimum mass requirement, stars wouldn’t remain in the main sequence stage.
What determines the upper and lower mass limits of stars?
The upper and lower mass limits of stars are determined by a variety of factors. At the high end, the upper limit is determined by the amount of fuel a star can burn in its lifetime, which varies depending on the size of the star and the composition of its core.
The most massive stars will consume their fuel relatively quickly and will quickly evolve into very large and luminous stars, or even supernovae, before returning their material to the interstellar medium.
On the low end, the lower mass limit of stars is determined by the minimum amount of mass that is necessary to sustain nuclear fusion in the star’s core. Specifically, the star must be massive enough to sustain the temperature and pressure needed to overcome the Coulomb barrier, the energy required for two nuclei to fuse.
For stars of around 0. 08 solar masses, these energy conditions can no longer be met, resulting in the star ceasing to fuse, ending its life as a “brown dwarf. ”.
Why the main sequence can be considered a mass sequence?
The main sequence can be considered a mass sequence because stars that fall along the main sequence on a Hertzsprung-Russell diagram are essentially just different sized versions of the same thing — a star that is in hydrostatic equilibrium, burning hydrogen in its core to produce energy.
The bigger the star, the more mass it has, and therefore the more hydrogen it has to supply its core with; this means more energy is produced, and the star is seen as having a higher luminosity. Smaller stars with less mass have less hydrogen to supply their cores and therefore less energy produced, leading them to be seen as less luminous on the H-R diagram.
As such, the main sequence is widely considered to be a mass sequence.
How does mass vary along the main sequence?
Mass is one of the most important characteristics of a star as it directly affects its luminosity, temperature, and lifespan. Along the main sequence, it is usually assumed that the more massive the star, the brighter and hotter it will be, and vice versa.
However, the relationship between mass and luminosity along the main sequence is not as straightforward as it may appear.
In general, for stars of the same spectral type, heavier stars are more luminous than their lighter counterparts and, as a result, have shorter life expectancies. This is because their increased mass implies they consume more energy.
A more massive star is thus brighter and hotter than a less massive star, creating a ‘hill’ of maximum luminosity and temperature along the main sequence.
At the higher mass end, the stars shine more brightly and heat up more quickly and become redder in color as they move to the right toward the red giant region. Conversely, as the mass decreases toward the bottom of the main sequence, the stars become dimmer and cooler but still remain on the main sequence.
The lowest mass stars in the main sequence are faint, cool, and red (M-type stars) and are sometimes called red dwarfs.
In addition to the effect of mass on luminosity, temperature, and lifespan, mass can also affect the extent to which stars evolve during their life. In particular, more massive stars evolve more quickly, depleting their fuel at a faster rate, and spending less time along the main sequence.
This is because their larger gravitational fields cause nuclear fusion reactions to occur at a faster rate.
What will happen if a low mass main sequence star runs out of hydrogen fuel?
When a low mass main sequence star exhausts its hydrogen fuel, it will gradually contract and heat up, eventually triggering a series of nuclear fusion reactions that involve helium atoms. This process is known as the helium flash and it will cause the star to rapidly transform into a red giant star.
As the star expands, its outer layers will become much cooler, and its luminosity will increase dramatically. The star will then continue to burn through the helium at its core until it runs out.
At this point, the star will become a white dwarf. This is an incredibly dense object — roughly the size of planet Earth — composed mainly of carbon and oxygen. The white dwarf will slowly cool down and eventually become a black dwarf when all of its heat is gone.
In summary, a low mass main sequence star will eventually turn into a white dwarf when its supply of hydrogen fuel is depleted. This will involve a rapid transformation known as the helium flash, as well as an increase in luminosity and gradual cooling.
What will happen to very low mass stars as they begin to exhaust their hydrogen?
As very low mass stars begin to exhaust their hydrogen, they will enter into the red dwarf stage, which is the longest-lived stage of stellar evolution. This is because they initially lack enough mass and pressure to initiate the fusion of heavier elements.
Low mass stars will first use their initial supply of hydrogen via the proton-proton chain, converting the hydrogen into helium. When the hydrogen is exhausted, the core contracts and the temperature increases to the point of helium fusion, which begins the next stage of the star’s lifetime.
In this stage of a star’s life, it lessens the energy output and its color changes to a red or orange. During this extended period of helium burning, the star is referred to as a red dwarf or ‘main-sequence dwarf’.
This stage of a star’s life can last for up to 10 trillion years, much longer than several other stages of a stars lifetime. Eventually, the last stage of the star’s life occurs live the helium fusion stops and the star turns into a black dwarf, with no outward light or heat.
What happens to a low mass star after helium fusion begins?
When helium fusion begins in a low-mass star, it marks the start of the star’s red giant phase. During this phase, the star will become larger and cooler as the core temperature increases, resulting in the fusion of helium into carbon and oxygen.
As a result of the increased temperature, the star will start to swell up, increasing its size and luminosity. Eventually, the core will become so hot that the star will expel its outer layers of gas, creating a planetary nebula.
The remaining core will then become a white dwarf, and cool down as it radiates away its remaining energy. The star will gradually dim and eventually become hard to detect, as it will no longer emit enough energy or light to be visible in the night sky.
Why do we not find stars with mass less than 0.08 solar masses quizlet?
We do not find stars with mass less than 0. 08 solar masses because stars must have a minimum mass necessary to initiate nuclear fusion in their cores. This minimum mass is known as the Hayashi limit and is determined by numerous factors such as the temperature of a star and the content of light elements in its core.
If the mass of a star is below the minimum mass, the temperature of its core will not be sufficient to start or sustain hydrogen fusion. In addition, stars with masses lesser than the minimum have weak, almost non-existent stellar winds, which prevent the necessary heat generated by reactions from escaping the star, further decreasing the temperature of the core.
Consequently, stars with masses below 0. 08 solar masses are unable to carry out nuclear fusion and become what is known as a brown dwarf and cannot be classified as a star.
What is the minimum possible mass for a star quizlet?
The minimum possible mass for a star quizlet is known as the “chandrasekhar Limit” and is approximately 1. 4 solar masses. Stars may form with less mass, but cannot sustain themselves through nuclear fusion.
This limit was first proposed by Subrahmanyan Chandrasekhar in 1931, when he hypothesised that if a star’s mass is less than 1. 4 solar masses, it would be unable to form a stable nucleus. This limit applies to stars made up of mainly hydrogen and helium and prevents them from becoming too massive and collapsing, resulting in the formation of a black hole.
What is the lowest mass that an object can have and still be a star quizlet?
The lowest mass that an object can have and still be classified as a star is 0. 08 solar masses. This is referred to as the “zero-age main sequence,” or the theoretical lower limit at which a gaseous cloud can collapse and ignite nuclear fusion.
Particles with a mass below this threshold have insufficient gravitational force to initiate and maintain sustained nuclear fusion, and thus are not considered stars. Examples of these “failed stars” may include brown dwarfs, or objects of less than 8 percent of the Sun’s mass.
Why can t the lowest mass main sequence stars become giants?
The lowest mass main sequence stars, known as red dwarfs, cannot become giants because they do not have the energy or temperature necessary to undergo the nuclear fusion reaction necessary to become a giant star.
A star must reach a certain level of temperature and pressure in its core before it is able to fuse hydrogen into helium. Red dwarf stars simply do not have the amount of energy and temperature necessary to do this.
Additionally, even if they did, they would not become giants due to their relatively small mass. Larger stars with higher masses have greater gravitational forces at the center of their cores, allowing the hydrogen to fuse faster and the core to become even more temperature and pressure-filled.
Red dwarf stars simply do not have enough mass for this fusion to occur quickly enough for them to become giant stars.
Why is the minimum mass of a star approximately 0.08 times that of the Sun?
The minimum mass of a star is approximately 0. 08 times that of the Sun because, according to the International Astronomical Union, an object must be at least 80 times the mass of Jupiter to be classified as a star.
Since the mass of the Sun is about 333,000 times that of Jupiter, that set an effective minimum mass for a star of about 26,640 times the mass of Jupiter, or approximately 0. 08 times the mass of the Sun.
This is the lowest mass at which a star can remain in a stable form of nuclear fusion in its core and therefore remain classified as a star. Objects at lower masses are classified as brown dwarfs.
What is the lowest solar mass a star can have?
The lowest mass a star can have is around 0. 08 times the mass of our Sun, which is equivalent to 8% of the solar mass. This type of star is known as a brown dwarf, and it is not officially considered to be a star since it does not have enough pressure and temperature for nuclear fusion to occur in its core.
Brown dwarfs are smaller and dimmer than stars, and they emit infrared radiation instead of visible light. Despite their small size, brown dwarfs can be incredibly dense, and they are believed to be made up of heavier elements such as carbon and oxygen.
The reason why the smallest possible star is limited to around 0. 08 solar masses is because any star with a lower mass would not be able to generate the necessary energy and pressure in its core to maintain fusion and to keep itself from collapsing.
Why is there a lower mass limit of 0.08 solar masses for main sequence stars Group of answer choices?
The lower mass limit of 0. 08 solar masses for main sequence stars is due to the fact that stars below this mass cannot generate sufficient energy in the form of nuclear fusion for sustained self-activity.
Stars of this size, known as brown dwarfs, emit too little light to be easily detected and are therefore difficult to classify. In general, stars with masses below 0. 08 solar masses are not large enough to produce enough energy to enter the main sequence and instead will remain in a pre-main sequence phase for their entire lifetime without any sustained nuclear fusion activity.
This is why the lower mass limit for main sequence stars is 0. 08 solar masses.