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A galaxy is a large, gravitationally bound system made up of stars, stellar remnants, an interstellar medium of gas and dust and dark matter. Galaxies can range from ten million stars to hundred trillion stars.

Within galaxies there can also be varying number of star systems, star clusters and types of interstellar clouds. In between celestial objects in galaxies are interstellar medium of gas, dust and cosmic rays. In the middle of all galaxies are supermassive black holes which are thought to be the primary driver of active galactic nuclei.

Galaxies are categorized according to their shape (visual morphology). Some common shapes are elliptical galaxies, spiral galaxies and irregular galaxies. Galaxies can also combine with nearby galaxies which increases incidents of star formations leading to starburst galaxies.

There are 170 billion galaxies observable in the universe. Intergalactic space is the space between galaxies which is filled with tenuous gas of average density, less than one atom per cubic meter. Galaxies are organized into hierarchy of associations. These are known as groups or clusters. These groups or clusters usually form larger superclusters. These superclusters will around into sheets and filaments which surround with immense voids.

Earth resides in the Milky Way galaxy. It is a spiral galaxy. There are approximately 100 – 40 billion stars with a mass of 1.0 – 1.5x1012 solar mass. It has a diameter of 100,000-120,000 light years. Most of the Milky Way is made up of dark matter. Which means it does no emit or absorb electromagnetic radiation. The Milky Way is part of the Local Group of galaxies which forms a subcomponent of the Virgo Supercluster.

Active Galaxies, Quasars, Collisions

1. What is the significance of studying active versus normal galaxies? Explain. 2. Do you think that our galaxy has ever been an active galaxy? Could it have hosted a quasar when it was young? 3. How can collisions affect the shape of galaxies? What evidence can you cite that galactic cannibalism really happens?

Galaxy distance questions

The Andromeda galaxy, also known as M31, is the nearest spiral galaxy to the Milky Way and the most distant object visible to the naked eye in the night sky. Andromeda is at a distance of 660 kpc from the Milky Way and it is moving towards the Milky Way at about 120 km s-1, with a collision and merger likely in about 4.5 billion

Samsung Galaxy S3 vs. iPhone 5

I need help creating a comparison between S3 and the new iPhone 5. Marketing Strategy! Which one is for you, the Samsung Galaxy S3 or new iPhone 5? Now that Apple's new iPhone has been announced, you may be dithering about whether to upgrade your current iPhone 4S or switch to another platform altogether--Android perhaps.

Need a Physics genius to help me out with this .

Suppose an airplane flew east along the equator from the Prime Meridian to the International Dateline; that is, exactly half way around the world. What is its final displacement? Is it the distance covered by its route of flight (12,450 miles) or the distance measured straight through the center of the earth (7,920 miles)? Suppo

Galaxy redshifts and distances away

See the attached file for clarity. Q1a) An astronomer observes two galaxies A and B which have redshifts of: Galaxy A = 0.08 and Galaxy B = 0.01 Which galaxy is closest to us and what is its distance away from us? You may assume that the hubble constant is H_0 = 75 km S^(-1) Mpc^(-1) and the speed of light is c= 3.0

Critical Thinking

Decide the type of claim that is made in the following statements, whether factual, verbal, interpretive, or evaluative: 1. One reading of people is that they always act out of self-interest and for their own advantage, although they sometimes try to disguise their actions as unselfish and altruistic. 2. Constantinople was


Suppose a blazar at z=1.00 goes through a fluctuation in brightness that lasts one week (168 hours) as seen from Earth. (a) At what speed does the blazar appear to be moving away from us? (b) Using the idea of time dilation, determine how long this fluctuation lasted as measured by the astronomer within the blazar?s hos

Distances to stars are determined.

How do we calculate or determine the distances to stars? What units do we use and what are the limitations (if any) of the method used for such calculations?

Red-Shift, Metrics, Light-Rays and Galaxies

Please answer the following (you will need to refer to the attachment for some of the questions): a) Describe what is meant by redshift and how spectroscopic observations of extragalactic objects may be used to deduce their redshifts. b) What is meant by the term metric? The Friedmann-Robertson-Walker metric for a homogeneou

Angular Variables and Tangential Variables

Our sun rotates in a circular orbit about the center of the Milky Way galaxy. The radius of the orbit is 2.2 1020 m, and the angular speed of the sun is 1.2 10-15 rad/s. (a) What is the tangential speed of the sun? (b) How long (in years) does it take for the sun to make one revolution around the center?

Black Hole

7. The Sun Rotates around the Milky Way Galaxy at a speed of a. 250 Km / sec and it makes an orbit in 20 Million years b. 20 Km / sec and it completes an orbit in 220 Million years c. 250 Km / sec and completes an orbit in 220 Million years d. 250 Km / sec but the time to complete an orbit can vary subs

Physics Problems: Black-Body

Question 2 Clearly show your working in any calculation and express your answers to an appropriate number of significant figures. (a) A proton of mass mp = 1.673 × 10−27 kg and electric charge e = 1.602 × 10-19 C, and an electron of mass me = 9.109 × 10-31 kg and electric charge −e = −1.602 × 10-19 C,

number of objects encountered as moving from the sun

As you move from the sun, how many of each object is encountered Ly=light-year Distance from sun Number of stars Number of dwarf galaxies Number of large galaxies Number of galaxy group Number of superclusters 1 ly 1 5 ly 3 12.5 ly 33 20 ly 83 50 ly 133 250 ly 260000 5,000 ly 600million

Several questions on relativistic mechanics

5-Three galaxies are aligned along an axis in order A, B, C. An observer in galaxy B is in the middle and observes that galaxies A and C are moving in opposite directions away from him, both with speeds 0.59c. What are the speeds of galaxies B and C as observed by someone in galaxy A? c (galaxy B) c (galaxy C) 6-A spacecr

Traveling Near the Speed of Light

There are a pair of identical twins. One remains on earth while the other goes on an extended trip through the galaxy. During this trip, the traveler averages a speed of 0.95 times the speed of light. If this trip lasts for a period of one year, as measured by the traveler, what is the age difference between the twins when th

Gravitation and Black Holes

At the Galaxy's Core. Astronomers have observed a small, massive object at the center of the Milky Way galaxy. A ring of material orbits this massive object; the ring has a diameter of about 17.0 light years and an orbital speed of about 130 km/s. (See attached file for full problem description) A) Determine the mass of the


1. Are the stars uniformly distributed in space? Please include references to support answer.

Velocity; Space; Direction etc ...

Please assist me with the attached questions. Thanks. Attached: 1) Galaxy A is found to be receding from us with a speed of 0.8c. Galaxy B I found to be receding from us with a speed of 0.4c. (a) What is our velocity as seen from galaxy A? (b) What is velocity of galaxy B as seen from galaxy A, if both are seen in the same

Calculating sidereal time

At what will the crab nebula cross the celestial median on March 12 and 13 2005. The right ascension is 05 31 30 and declination is 21 59 00.

Gravity and air resistance questions

Junior high studetn needs help with understanding concept behind grvaity. Help with following basic questions in simple terms please. 1. Imagine you started to walk towards the west. Imagine that you can walk forever and that you can even walk on water. If you walk in the same direction forever, what will happen? Where will y

6 Physics problems: Calculating ion field paths

1. A singly charged positive ion has a mass of 2.5*10^-26kg. After being accelerated through a potential difference of 250V, the ion enter a magnetic field of 0.50T, in a direction perpendicular to the field. Find the radius of the path of the ion in the field. 2. Two ions with masses of 5.1*10^-26kg move out of the slit of