Course Work On Astronomy Questions

Published: 2021-06-22 08:30:06
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Category: Energy, Disaster, Pressure, Nuclear Weapon, Atomic Bomb, Stars, Density, Black Hole

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Question #1

Three main layers of the interior of the Sun are convection zone, radiation zone and the core.The central part of the Sun with a radius of about 150-175 thousand km (ie, 20-25% of the radius of the Sun), in which are thermonuclear reactions, called a solar core. The density of material in the core is about 150 000 kg / m ³ (150 times higher than the density of water and ~ 6.6 times higher than the density of the densest metal on the Earth - osmium), and the temperature in the center of the core is over 14 million K. A SOHO mission data analysis showed that the rate of rotation of the sun core around its axis is significantly higher than on the surface. At the core is the proton-proton fusion reaction, which resulted in four protons produced helium-4. Every second 4,260,000 tons of substance turns into the light, but this figure is negligible compared to the mass of the Sun - 2∙1027 tons. Power allocated from the different areas of the nucleus, depends on their distance to the center of the Sun. At the heart of it it reaches, according to theoretical estimates, 276.5 W / m ³. Thus, on the volume of a human (0.05m ³) is 285 kcal / day (1,192 kJ / day) to heat, which is much less than the specific heat of the living waking man. Specific heat is the total volume of the sun even two orders of magnitude smaller. So humble specific energy supplies "fuel" (hydrogen) is enough for a few billion years of the thermonuclear reaction.

Core is the only place in the Sun, in which the energy and heat are obtained from the fusion reaction, the rest of the star is heated by this energy. All core energy passes successively through the layers until the photosphere, which is emitted in the form of sunlight and kinetic energy.

At a distance of about 0.2-0.25 to 0.7 solar radius above the core, there is a zone of radiative transfer. In this zone, the energy transfer takes place mainly by radiation and absorption of photons. The direction of each individual photon emitted by the plasma layer does not depend on which the photons absorbed by the plasma, so as it can penetrate the plasma layer in the following radiant zone and move back into the lower layers. That’s why the time period of multiple emission of photons (originally arose in the core) reaches a convective zone may be measured in millions of years. The average this time for the Sun is 170 million years old.

The temperature difference in this zone is from 2 million K on a surface up to 7 million K in depth. The macroscopic motion convections is absent in this zone, which means that the adiabatic temperature gradient is greater than the gradient of radiative equilibrium. For comparison, the pressure in red dwarfs cannot prevent the mixing of the substance and the convection zone starts right from the core. The substance density in this zone ranges from 0.2 (at the surface) to 20 (in depth) water densities.

Closer to the Sun's surface, the temperature and the density of the material is not enough for a full transfer of energy by re-radiation. The vortex mixing of the plasma occurs and the transfer of energy to the surface (photosphere) is managed by primarily movements of the substance itself. On the one hand, the substance of the photosphere, cooled on a surface, is immersed deep into convective zone. On the other hand, the substance in the bottom area of ​​the radiation beam transport rises up; both processes proceed at a significant velocity. This method of energy transfer is called convection, and a subsurface layer of the sun (thickness is about 200 000 km), where it occurs - convective zone. As the surface temperature decreases to an average of 5800 K, and the gas density to less than 1/1000 of terrestrial air density.

According to current data, its role in the physics of solar processes is extremely high, as it is exactly in it the diverse movements of solar material arises. Thermals in the convection zone caused the granules on a surface (which in fact are the tops of thermals) and supergranulation. The flow rate is about 1-2 km / s, and its maximum value up to 6 km / s. Lifetime of the granules is 10-15 minutes, which is comparable with the period during which gas can go around once granules. Therefore, in the convection zone thermals are conditions drastically different from the conditions conducive to occurrence of Benard cells.

Question #2

Model of the Sun (Solar system) is a mechanical device that illustrates the relative positions and motions of the planets and their moons in the solar system in a heliocentric model. The device usually has a clockwork mechanism with a sphere, which represents the sun, in the center, and with the planets at the edges.
If we are saying about the standard model of the Sun, we have to notice, that it is a mathematical model, which models the basic physical processes in the Sun.

Question #3

The neutrino is a neutral fundamental particle with half-integer spin, participating only in weak and gravitational interactions, and related to the class of leptons. Low energy neutrinos interact extremely weakly with matter: for example, neutrinos with energies of 3-10 MeV are in the water the mean free path of the order of 1018m (about 100 St.. Years). We also know that every second across the landing on Earth in 1 cm ² goes around 6∙1010 neutrinos emitted by the Sun. However, no influence, such as the human body, they do not have. At the same time, high energy neutrinos successfully detected by their interaction with the target.

The neutrino mass is very small. Experimental evaluation of the upper sum of the masses of all types of neutrinos is only 0.28 eV. The difference of the squares of the neutrino masses of different generations, obtained from the oscillation experiments, does not exceed 2.7∙10-3 eV ².

The neutrino mass is important for the hypothesis to explain the phenomenon of dark matter in cosmology, because, despite its smallness, perhaps, the concentration of neutrinos in the universe is high enough to significantly affect the average density.

One of the possible applications of the neutrino is neutrino astronomy. It is known that the stars, except for the light from the large flux of neutrinos that arise in the process of nuclear reactions. Since the late stages of stellar evolution is carried away by the neutrinos to 90% of the radiated energy (neutrino cooling), the study of the properties of neutrinos (in particular - the energy spectrum of solar neutrinos) helps to better understand the dynamics of astrophysical processes. In addition, the absorption of neutrinos passes without great distances, allowing you to discover and explore more distant astronomical objects.

Question #4

The answer is “Distances” – C. This is one of the methods which astronomers usually use to measure distances from Earth to the stars.

Question #5

We know, that the distance and the apparent and absolute magnitude are related. We might measure the parallax for a nearby star. The formula is

Where M is a magnitude of an object, m is an apparent magnitude, is a luminosity distance.

Question #6

The relationship between the luminosity and the mass of a star, described by the equation, is called the mass-luminosity relation. The general equation is:
Where L⊙ and M⊙ are the mass and the luminosity of the Sun, 1
Question #7

The lowest mass that a star can have on the main sequence is 0.08 Mo. Everything which is lesser falls short to it. The pressure and a temperature depend on mass, and some certain values are necessary to fusion. Hence, stars must have some limit of mass to be joined in the main sequence.

Question #8

The Sun constantly synthesizing hydrogen into helium in the last 5 billion years. Astronomers predict that it will do the same the next 5 billion years, until all the hydrogen ends.
As soon develop into all of the hydrogen, helium core at the center of the Sun will start to shrink gradually warming up and sealed until suddenly will not start a second nuclear reaction, to make the atoms of helium into carbon and oxygen. At the same time, all the excess energy will push the outer layers of the Sun, so that it will increase its size by 250 times, becoming a red giant.

Question #9

The stars with mass < 0.4 Mo are very low mass stars. This stars are convective throughout. The helium, which is created at the core, has a certain distribution across the star. Thus an uniform atmosphere is produced and those stars have a proportionately higher lifespan of a main sequence.
The stars with mass > 0.4 Mo are resistant against the convection. This involves the buildup of a core helium-rich. This kind of stars can transport their energy by radiation.

Question #10

Most of the theoretical models of the white dwarf suggest that the oxygen-neon core is covered with a thick enough layer of carbon. It isolates the core and prevents the diffusion of appreciable amounts of oxygen to the surface. However, calculations show that the thickness of this layer is as smaller, as closer to the limit of the mass progenitor star was a white dwarf.

Question #11

Chandrasekhar limit is the upper limit of the mass at which the star can exist as a white dwarf. If the mass of the star exceeds this limit, it becomes a neutron star. Existence of the Indian astrophysicist has been proven Subramanyanom Chandrasekhar. The value is usually taken to 1.4 solar masses. Strictly speaking, the Chandrasekhar limit is the upper limit of the mass of cold non-rotating white dwarf is determined by the condition that the pressure forces of the electron gas and gravity.

In close binary systems are often one of the components is a white dwarf. If his partner in the process of evolution fills its Roche lobe, begins an intense accretion onto the white dwarf, in which they may be exceeded the Chandrasekhar limit, the consequence of which is the explosion of a supernova of type Ia. Because these supernovae are "calibrated by mass" Chandrasekhar limit, their energy release also proves to be "calibrated": the differences in their splendor are very small. Thanks to this particular Type Ia supernovae are used to determine distances to distant galaxies.

Question #12

White dwarfs are the the core of the star, which was prior to discharge to the outer layers of the branches of the supergiants. When the shell of a planetary nebula will dissipate, the core of the star, which was previously on the branch of the supergiants, will appear in the upper left corner of the graph GR. Cooling down, it will move into the top corner of the chart for white dwarfs. The core is hot, small and blue low-luminosity - that characterizes the star as a white dwarf.

White dwarfs composed of carbon and oxygen with small additions of hydrogen and helium, but in massive highly evolved star core can consist of oxygen, neon, or magnesium. White dwarfs Immersed extremely high density (106 g/cm3). Nuclear reactions in the white dwarf does not go The white dwarf is in a state of gravitational equilibrium and the pressure is determined by the pressure of a degenerate electron gas. The surface temperatures of the white dwarf high - from 100,000 to 200,000 K. The masses of white dwarfs order of the Sun (0.6 Msun - 1.44Msun). For white dwarfs, there is a relationship "weight range", and the greater the mass, the smaller the radius. There is a critical mass, the so-called Chandrasekhar limit, above which the pressure of the degenerate gas cannot resist the gravitational compression and collapse of a star occurs, ie, radius tends to zero. The radii of most white dwarfs are comparable to the radius of the Earth.

The neutron star is an astronomical object, which is one of the end products of stellar evolution, which consists mainly of the neutron core, covered with a relatively thin (~ 1 km) crust material in the form of heavy atomic nuclei and electrons. The masses of neutron stars are comparable to the mass of the Sun, but a typical radius are only 10-20 kilometers. Therefore, the average density of matter in such a star is several times greater than the density of an atomic core (which for heavy nuclei is an average of 2.8∙1017kg / m ³). Further gravitational contraction of the neutron star prevents the pressure of nuclear matter, arising from the interaction of neutrons. It is believed that neutron stars are born in supernova explosions.

That’s why more common are white dwarfs, because they have come from small stars.

Question #13

Supermassive black hole is a black hole with a mass of about 105-1010solar masses. Supermassive black holes found at the center of many galaxies, including the Milky Way

Supermassive black holes have unique properties that distinguish them from the smaller black holes:

Paradoxically, the average density of a supermassive black hole (calculated by dividing the mass of the black hole at its Schwarzschild volume) can be very small (even smaller than that of air). This is because the radius Schwarzschild directly proportional to the mass and density - is inversely proportional to the volume. As the volume of a spherical object (such as a non-rotating event horizon of a black hole) is directly proportional to the cube of the radius and the mass increases linearly, the value of the volume is increasing faster than the mass. Thus, the average density decreases with increasing radius of the black hole.

Question #14

It wouldn’t affect it, only the radiation pressure will gone. This is not a large change. As the black hole would have the mass of the Sun, the gravity will not change. Earth just will continue its orbiting around the black hole.

Sources

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- Burton, W. B. (1986). "Stellar parameters". Space Science Reviews 43 (3–4): 244–250.
- Seidelmann, P. K.; et al. (2000). "Report Of The IAU/IAG Working Group On Cartographic Coordinates And Rotational Elements Of The Planets And Satellites: 2000". Retrieved 2006-03-22.
- Emilio, Marcelo; Kuhn, Jeff R.; Bush, Rock I.; Scholl, Isabelle F. (March 5, 2012), "Measuring the Solar Radius from Space during the 2003 and 2006 Mercury Transits", arXiv, retrieved March 28, 2012
- Ziebarth, Kenneth (1970). "On the Upper Mass Limit for Main-Sequence Stars". Astrophysical Journal 162: 947–962.
- Richmond, Michael W. (2004-11-10). "Stellar evolution on the main sequence". Rochester Institute of Technology. Retrieved 2007-12-03.
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