As we have already discusses about the universe in our previous blog. If you haven’t read about it then you can click on below link to read that blog. We are now going to talk about the galaxy in this blog. Galaxy is nothing but the group of the stars, planets, gases, matter or anti matter etc. which are bounded by the powerful and dominating fundamental force i.e. Gravitational force.
The total number of galaxies present in the universe…….
Talking about the above line, we can say that the universe is very vast and there may be millions of trillions galaxies present in it. In the observable universe there are an approximate of 200 million to 2 trillion galaxies estimated up to recent studies. The galaxies are classified according to the visual properties such as elliptical, spiral or irregular. Various galaxies are considered to have huge black hole as its active center. Most of the galaxies have diameter in the range of 3000 to 30,000 light years.
More information on galaxies…
The space found between the galaxies are filled with the gas which has an average density of less than one atom per cubic centimeter. There are various galaxies known but among them all we are very familiar to one which is milky may. Various galaxies are bounded by the gravitational force and some are bounded by the external unknown forces. The diameter of the Milky Way is about 100,000 light years. The nearest neighbor of our galaxy is the Andromeda galaxy which is about 2.5 million light years.
1. Milky Way
|Fig: Milky Way|
The Milky Way is the galaxy in which our solar system is located. It is the second largest galaxy in the local group. However, Milky Way Galaxy looks like a disc shaped structure when viewed from inside, thus appearing as a band in the universe. It is estimated to contain approximate amount of 100-400 billion stars. The galactic center, in an instance is known as Sagittarius A, which is an intense radio source.
The solar system is located within the oval-shaped disk of about 26,500 light years from the galactic center. However, the rotation of the Milky Way is constant which is the contradiction to the Keplerian Dynamics. Certainly, most of the Milky Way mass does not emit or absorb electromagnetic radiation. The rotational period of the Milky Way is about 240 million years at the position of the Sun. The oldest star in the Milky Way is same as the age of the universe itself which are assumed to be formed shortly after the big bang.
More on Milky Way
As viewed the Milky Way from earth, it is observed that we are having 30 constellation which are occupying space in the galactic plane. The galactic center lies in the Sagittarius direction, at which the Milky Way seems to be brightest.
A hazy band of white light appears to pass around to the galactic anti center in Auriga, from Sagittarius. The band then continues and divides the sky into two roughly equal hemispheres, turning back to Sagittarius from the rest of the sky.
Milky Way contains nearly 300 to 400 billion stars and at least 110 planets.
|Fig: Andromeda galaxy|
It is the nearest galaxy from our galaxy which is approximately 2.5 million light years away from us. The 2006 observation made through the Spitzer space telescope tells that there are about 1 trillion stars in the Andromeda galaxy, which is more than twice of the Milky Way galaxy. However ,iIts mass is also 1.5 times the Milky Way mass, which is obvious as with the increase in the stars.
3. The Cigar galaxy (Messier 82)
Its distance is about 12 million light years from the Ursa Major Constellation. It is about 5 times more luminous than our milky way galaxy. It was first discovered by the Johann Elbert Bode on 31 December 1774.
4. The Pinwheel Galaxy
It is a spiral shaped galaxy having a distance of approximately 21 million light years from the Earth. It was first discovered on March 27, 1781 by Pierre Mechain. A very detailed image of pinwheel galaxy was released by the NASA and the European Space Agency on 28 February, 2006. It was the largest and the detailed photograph obtained by the Hubble Space Telescope at that time.
5. The Sombrero Galaxy
Firstly, It is a spiral galaxy located in the constellation Virgo which is at a distance of approximately 31 billion light years from the Earth. Secondly, the diameter of Sombrero Galaxy is about 50,000 light years, which is 30% size of the Milky Way. The Sombrero Galaxy was discovered by Pierre Mechain on May 11, 1781.
6. The Whirlpool Galaxy
The distance of the Whirlpool Galaxy is estimated to be 30 to 35 billion light years from the Milky Way. However this galaxy is located within the Canes Venatici constellation. It was founded by the Charles Messier on 13 October, 1773.
7. NGC 1300
It has an approximate distance of about 60 million light years from the Earth. However, it is located in Eridanus Constellation and was founded by John Herschel in 1835. But its size is equal to the size of the Milky Way.
8. The Tadpole Galaxy
It is located in the northern constellation Draco and is about 420 million light years away from Earth.
9. Hoag’s Object
Hoag’s object is a type of ring galaxy. It was discovered by the Arthur Hoag in 1950. Thus its name was given As the Hoag’s Object. It approximately contains about 8 billion stars in it.
That’s all for this blog. Further observations are performed on finding the other galaxies.
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