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Stars

A star is a large luminous sphere of plasma held together by gravity. The star that is most near the earth is the Sun. The Sun is the Earth’s main source of energy. Other stars are visible from the Earth in the night. Historically, the most prominent stars were grouped together into constellations and asterisms. Today extensive cataloged of stars have been assembled by astronomers. This provides standardized star designations.

The formation of a star begins with gravitational instability within a molecular cloud. This is caused by regions of higher density that triggered by shack waves from a nearby supernovae, the collision of different molecular clouds or the collision of galaxies. Once the region reaches Jeans instability, it begins to collapse under its own gravitational force. When the cloud collapses, individual conglomerations of dense dust and gas form Bok globules. The density increases and the gravitational energy is converted into heat. When the cloud has reached a stable condition of hydrostatic equilibrium, a protostar forms at the core.

Stars shine for a number of reasons. For a portion of their life stars shine due to thermonuclear fusion of hydrogen into helium in its core. It releases energy that traverses the star’s interior and radiated into outer space. Once the hydrogen is exhausted, all naturally occurring elements heavier than helium are created. This happens through stellar nucleosynthesis or by supernova nucleosynthesis. At the end of a star's life it contains a proportion of degenerate matter.

Binary and multi-star systems are systems of two or more stars that are gravitationally bound. They generally move around each other in stable orbits. Their gravitational interactions can have a significant impact on their evolution. These systems of stars can be part of a larger gravitationally bound structure like a star cluster or galaxy.

Historically, stars have played an important role to civilization throughout the world. Stars have been a part of religion, celestial navigation and orientation. Calendars and agricultural practices were also based on the motion of the sun against the background of the stars.

Categories within Stars

Lifetime

Postings: 6

The duration of a stars existence or usefulness.

Pulsars

Postings: 5

A pulsar is a magnetized, rotating neutron star that emits a beam of electromagnetic radiation.

Nebulae

Postings: 5

Nebulae is an interstellar cloud of dust, hydrogen, helium and other ionized gases.

Eratosthenes' Method

Drawing on Eratosthenes' method, if two observers are due north and south of each other and are separated by 400 km, what is the circumference of their spherical world if they see the same star on their meridian at altitudes of 23 degrees and 47 degrees respectively, and at the exact same time?

Physics: The Angular Speed of a Neutron Star

Under some circumstances, a star can collapse into an extremely dense object made mostly of neutrons and called a neutron star. The density of a neutron star is roughly 10^14 times as great as that of ordinary solid matter. Suppose we represent the star as a uniform, solid, rigid sphere, both before and after the collapse. The s

Space travel: How many years would it take to travel to a star?

Part 1 A certain star is 73.3 light-years away. How many years would it take a spacecraft traveling 0.959c to reach that star from Earth, as measured by observers on Earth? Part 2 How many years would it take to reach that star from Earth, as measured by observers on the spacecraft?

Light-years away, distance traveled in light years.

Part 1 A certain star is 73.3 light-years away. How many years would it take a spacecraft traveling 0.959c to reach that star from Earth, as measured by observers on Earth? Part 2 How many years would it take to reach that star from Earth, as measured by observers on the spacecraft? Part 3 What is the distance (

Truth Statements on Time Dilation

Which of the following statements are true about time dilation? 1. Time dilation suggests that an astronaut traveling to a distant star would actually age less than we would have measured at rest on Earth 2. Time dilation can be summarized by saying that a moving clock runs slower as compared to a clock at rest 3. Ti

Compute distance in meters, given 8.80 light years away

A star in our galaxy, Luyten, is 8.80 light-years away. That is, it takes 8.80 years for the light it emits to reach Earth. How far away is it in meters? Please solve and explain problem. If possible, please upload problem in pdf.

Schwarzschild radius

(a) Calculate the Schwarzschild radius of a supermassive black hole of mass 3.7 x 10^6 M., the estimated mass of the black hole at the galactic center. Give your answer in both kilometers and astronomical units. (b) What is the angular diameter of such a black hole as seen at a distance of 8 kpc, the distance from the Ear

North Star, frequency of light, radio waves, underwater sun

The distance to Polaris, the North Star, is approximately 6.44 x 10^18 m. If Polaris were to burn out today, how many years would it take to see it disappear? (b) How long does it take sunlight to reach Earth? (c) How long does it take a microwave signal to travel from Earth to the Moon and back? (The distance from Earth to the

Stars

1. In what order are the Bayer letters assigned to stars? 2. Is delta-Capricorni brighter than alpha-Capricorni? How do you know? 3. In what order are Flamsteed numbers assigned to stars? 4. How many nonstellar objects did Messier include in his catalog? 5. Why did Messier compile his list, and how were these obj

Five problems on velocity, acceleration, friction etc.

1)A coffee cup on the dashboard of a car slides forward on the dash when the driver decelerates from 42.7 km/hr to rest in 3.72s or less, but not if he decelerates in a longer time. What is the coefficient of static friction between the cup and the dash? 2)A chain consisting of five links, each of mass 0.180 kg, is lifted ve

Star's Temperature and Energy radiated by it

(a) A star's temperature is 6175 K. According to the Stefan-Boltzmann law, how much energy is radiated into space per second by each square meter of the star's surface ? 1..... J (b) If the star's radius is 605,000 km, what is the total power output of the star? 2 ...... W

Boltzman Law

The star Betelgeuse has a radius r=3.8 x 10^11m. Its surface temperature is 2800K (assume this is 1/2 of that of our Sun). Assuming Betelgeuse is a perfect emitter (e=1.0) what is its power output? What is the ratio of this power output to the power output of our Sun?

Cross section of a moving star

A star of radius R and mass M is moving with velocity v through a cloud of particles of density rho. If the particles that collide with the star are trapped by it, show that the mass of the star will increase at rate: dM/dt = Pi * rho * v * (R^2 +2GMR/v^2) Show how the cross sectional area compares with the geometric cros

Orbital Speed/Angular Diameter

Because of the presence of Jupiter, the Sun moves in a small orbit of radius 742,000 km with a period of 11.86 years. (a) Calculate the Sun's orbital speed in meters per second. (b) An astronomer on a hypothetical planet orbiting the star Vega, 25 light-years from the Sun, wants to use the astrometric method to search for plan

What is the name of a star that is a good example of a

Please see the attached file. QUESTIONS: 1. What is the name of a star that is a good example of a: a. cool main sequence star: ___________________ d. red supergiant: _____________________ b. hot main sequence star: ___________________ e. blue supergiant: ____________________ c. red giant:______________________________

Science of sunlight and stars

Here is what my team of 2 people need to do (A-F)and we don't know how to get it started. I only need help with Part A & D and then my partner and I will see how this is supposed to go. Please make Part A & D. a. The internal structure of the Sun and how astronomers learn about the Sun's interior (JUST EXPLAIN WHY & HOW) d

Momentum

See attached file for full problem description. 1. Thoroughbred horse are among the fastest horses in the world and are used in famous racing events such as the Kentucky Derby. The mass of a thoroughbred is about 500 kg. If a horse with this mass is galloping with a momentum of 8.22*10^3 kg.m/s, what is its speed? 2. A pitch

Network Topologies

Outline the three general network topologies (bus, ring, and star). Describe the components, devices, and arrangement of components and devices involved in each topology, as well as some of the pros and cons of each configuration.

Sun and Stars Compared

Compare the Sun with two other stars. Create a table comparing luminosity, distance from Earth, temperature, and mass. Based on this information state whether you think the comparison star is older, younger, or about the same ages as the Sun.

weight on the surface of a neutron star

Neutron stars, such as the one at the center of the Crab Nebula, have about the same mass as our sun but a much smaller diameter. If you weigh 655 N on the earth, what would you weigh when at the surface of a neutron star that has the same mass as our sun and a diameter of 16.0 km? Take the gravitational constant to be G =

Calculate energy and sketch spectrum

At the surface of a distant star, the temperature is approximately 6500 K. a) How much energy is contained in the electromagnetic radiation filling a cubic meter of space at the star's surface? b) Sketch the spectrum of this radiation as a function of photon energy. Mark the region of the spectrum that corresponds to vi