What is a main sequence star for kids?
Main-sequence stars are stars similar to our Sun. They convert hydrogen to helium in their cores, and the majority of the stars are in this classification, including dwarf stars, yellow dwarf stars, and red dwarf stars.
The main sequence is the stage where a star spends most of its existence. Relative to other stages in a star's "life" it is extremely long; our Sun took about 20 million years to form but will spend about 10 billion years (1 × 1010 years) as a main sequence star before evolving into a red giant.
Notable examples of main sequence stars are the Sun, Sirius A, Achernar, Alpha Centauri, and Altair.
When the protostar starts fusing hydrogen, it enters the "main sequence" phase of its life. Stars on the main sequence are those that are fusing hydrogen into helium in their cores. The radiation and heat from this reaction keep the force of gravity from collapsing the star during this phase of the star's life.
Definition of main sequence
: the group of stars that on a graph of spectrum versus luminosity forms a band comprising 90 percent of stellar types and that includes stars representative of the stages a normal star passes through during the majority of its lifetime.
A star is a luminous ball of gas, mostly hydrogen and helium, held together by its own gravity. Nuclear fusion reactions in its core support the star against gravity and produce photons and heat, as well as small amounts of heavier elements. The Sun is the closest star to Earth.
Most main sequence stars are nearly completely composed of hydrogen and helium. Some have a small percentage of heavier elements, such as carbon or oxygen. Scientists can analyze the composition of a main sequence star by studying the light that they emit.
For most of a star's life, hydrogen atoms fuse to form helium atoms. A star like this is a main sequence star. The hotter a main sequence star is, the brighter it is. A star remains on the main sequence as long as it is fusing hydrogen to form helium.
Less massive stars burn cooler and dimmer. Temperature translates to color, and this relationship between color and brightness (luminosity) for hydrogen-burning stars is called the main sequence. Massive hydrogen-burning stars are blue-white, the Sun is yellow, and low-mass stars are orange and red.
In astronomy, the main sequence is a continuous and distinctive band of stars that appears on plots of stellar color versus brightness. These color-magnitude plots are known as Hertzsprung–Russell diagrams after their co-developers, Ejnar Hertzsprung and Henry Norris Russell.
What is a main sequence star GCSE?
For most of its lifetime, a star is a main sequence star. It is stable, with balanced forces keeping it the same size all the time. During this period: gravitational attraction tends to collapse the star. radiation pressure from the fusion reactions tends to expand the star.
The lifetimes of main sequence stars therefore range from a million years for a 40 solar mass O-type star, to 560 billion years for a 0.2 solar mass M-type star.
Stars in the main-sequence stage give out energy as light and heat. This energy is released by nuclear fusion reactions deep in their cores. The reactions fuse hydrogen nuclei to create helium. Stars spend about 90% of their lives in this stage.
Explanation: Fusion reactions which fuse 4 hydrogen nuclei into a helium nucleus generates the energy in main sequence stars.
A star is an exploding ball of burning gas held together by gravity. Our sun is a star! It produces great amounts of energy in the form of light and heat that provide the perfect conditions for life on Earth.
A star is a large ball of burning gas in space. Stars appear to us as small points of light in the sky on clear nights. The night was dark, the stars hidden behind cloud. 2. See also morning star, shooting star.
Stars are celestial objects that can produce their own light. They are extremely hot and extremely large. They are mostly made up of hydrogen gas with a little helium in them.
Stars in the main sequence have achieved a state of equilibrium, which means that the forces pushing in and the forces pushing out are equal and balance each other out. As long as the star has enough fuel in its core to continue its fusion reaction, the star will maintain equilibrium and stay a main sequence star.
G-type main-sequence star.
The largest known star is UY Scuti, a hypergiant with a radius somewhere around 1,700 times larger than the sun. Its mass, however, is only 30 times that of our nearest star.
What happens after main sequence star?
When stars run out of hydrogen, they begin to fuse helium in their cores. This is when they leave the main sequence. High-mass stars become red supergiants, and then evolve to become blue supergiants. It's fusing helium into carbon and oxygen.
O stars are the least common and M are the most common found in the main sequence of stars. Stars near the beginning or end of their lives are not part of this classification. The new system of classification was published in the 1920s and included 225,300 stars.
Stars are hot. Astronomers have found the coolest star – temperature-wise, that is – although some would argue it should not be called a star.
Most of them look white, but some are distinctly red in color while others are blue. A star's color tells us about its temperature and mass, and blue stars are the hottest and most massive of all. Any star that has three or more times as much mass as the sun will tend to look blue to our eyes.
A red giant forms after a star has run out of hydrogen fuel for nuclear fusion, and has begun the process of dying. A star maintains its stability through a fine balance between its own gravity, which holds it together, and the outwards pressure from ongoing thermonuclear fusion processes taking place at its core.
The most massive stars have the shortest lifetimes. Because they have most fuel, they burn it so prodigously that their lifetimes are very short. A stars time on the main sequence varies from a few million to 2x1011. As we will see later, the way in which a star evolves depends on its mass.
Zero Age Main Sequence (ZAMS) is the time when a star first joins the main sequence on the Hertzsprung-Russell diagram (HR diagram) by burning hydrogen in its core through fusion reactions.
A star is born when atoms of light elements are squeezed under enough pressure for their nuclei to undergo fusion. All stars are the result of a balance of forces: the force of gravity compresses atoms in interstellar gas until the fusion reactions begin.
A star is formed when it is hot enough for the hydrogen nuclei to fuse together to make helium. The fusion process releases energy, which keeps the core of the star hot.
The Star remains the longest in the stage when it is burning Hydrogen into Helium. For our Sun this is called the main sequence stage which will last for about 4.5 Billion years more , this depends on how fast the star is burning up fuel. For more massive stars this stage lasts for a few hundred million years.
What stage is our Sun?
Right now, our Sun is in a stage called yellow dwarf. It is about 4.5 billion years old. In another 5 billion years the Sun will become a big, cool star called a red giant. A few billion years after that, it will become a small white dwarf star.
The main sequence stretches from the top left corner (hot, luminous stars) to the bottom right corner (cool, faint stars) in the H-R diagram.
Once there is no fuel left, the star collapses and the outer layers explode as a 'supernova'. What's left over after a supernova explosion is a 'neutron star' – the collapsed core of the star – or, if there's sufficient mass, a black hole.
Generally, the more massive the star, the faster it burns up its fuel supply, and the shorter its life. The most massive stars can burn out and explode in a supernova after only a few million years of fusion. A star with a mass like the Sun, on the other hand, can continue fusing hydrogen for about 10 billion years.
For most of a star's life, hydrogen atoms fuse to form helium atoms. A star like this is a main sequence star. The hotter a main sequence star is, the brighter it is. A star remains on the main sequence as long as it is fusing hydrogen to form helium.
Just 8.6 light-years away, Sirius is already the brightest nighttime star. It is double: a bright A-type main-sequence star and a faint white dwarf — the closest white dwarf to Earth.
A main sequence star will get its energy from nuclear fusion reactions, which is the conversion of hydrogen in a star's center into helium. Such a process converts four hydrogen into a lighter helium nucleus. The change in mass is what produces a sun's energy and, thus, its starlight.
Temperature translates to color, and this relationship between color and brightness (luminosity) for hydrogen-burning stars is called the main sequence. Massive hydrogen-burning stars are blue-white, the Sun is yellow, and low-mass stars are orange and red.
Main Sequence Stars
Stars are fueled by the nuclear fusion of hydrogen to form helium deep in their interiors. The outflow of energy from the central regions of the star provides the pressure necessary to keep the star from collapsing under its own weight, and the energy by which it shines.
The lifetimes of main sequence stars therefore range from a million years for a 40 solar mass O-type star, to 560 billion years for a 0.2 solar mass M-type star.
What is the largest main sequence star?
The largest known star is UY Scuti, a hypergiant with a radius somewhere around 1,700 times larger than the sun. Its mass, however, is only 30 times that of our nearest star.
Venus shines so brightly that it is the first “star” to appear in the sky after the Sun sets, or the last to disappear before the Sun rises. Its orbital position changes, thus causing it to appear at different times of the night throughout the year.
| Latin Name | English Name or Description |
|---|---|
| Triangulum Australe | Southern triangle |
| Tucana | Toucan |
| Ursa Major | Big bear |
| Ursa Minor | Little bear |
Sirius in history
Today, Sirius is nicknamed the "Dog Star" because it is part of the constellation Canis Major, Latin for "the greater dog." The expression "dog days" refers to the period from July 3 through Aug. 11, when Sirius rises in conjunction with the sun, Space.com previously reported.
After the star's outer layer has escaped, the much smaller inner layer collapses into a white dwarf. This star, which is hotter and brighter than the red giant it came from, illuminates and warms the escaped gas, until the gas starts glowing by itself – and we see a planetary nebula.
Stars spend most of their lives on the Main Sequence with fusion in the core providing the energy they need to sustain their structure. There is a price for this. As a star burns hydrogen (H) into helium (He), the internal chemical composition changes and this affects the structure and physical appearance of the star.
G-type main-sequence star.