Skip to main content

Galaxy


A galaxy is a gravitationally bound system of stars, stellar remnants, interstellar gas, dust, and dark matter.The word galaxy is derived from the Greek galaxias (γαλαξίας), literally "milky", a reference to the Milky Way. Galaxies range in size from dwarfs with just a few thousand (103) stars to giants with one hundred trillion (1014) stars,each orbiting their galaxy's own center of mass. Galaxies are categorized according to their visual morphology, including elliptical,spiral, and irregular.Many galaxies are thought to have black holes at their active centers. The Milky Way's central black hole, known as Sagittarius A*, has a mass four million times greater than our own Sun.As of July 2015, EGSY8p7 is the oldest and most distant galaxy with a light travel distance of 13.2 billion light-years from Earth, and observed as it existed 570 million years after the Big Bang. Previously, as of May 2015, EGS-zs8-1 was the most distant known galaxy, estimated to have a light travel distance of 13.1 billion light-years away and to have 15% of the mass of the Milky Way.

Approximately 170 billion (1.7 × 1011) to 200 billion (2.0 × 1011) galaxies exist in the observable universe. Most of the galaxies are 1,000 to 100,000 parsecs in diameter and usually separated by distances on the order of millions of parsecs (or megaparsecs). The space between galaxies is filled with a tenuous gas with an average density less than one atom per cubic meter. The majority of galaxies are gravitationally organized into associations known as galaxy groups, clusters, and superclusters. At the largest scale, these associations are generally arranged into sheets and filaments that are surrounded by immense voids.

Comments

Post a Comment

Popular posts from this blog

Sardar Hari singh Nalwa

Sardar Hari Singh Nalwa (1791–1837) was Commander-in-chief of the Khalsa, the army of the Sikh Empire. He is known for his role in the conquests of Kasur, Sialkot, Attock, Multan, Kashmir, Peshawar and Jamrud.He is also a founder Haripur, Pakistan city. Hari Singh Nalwa was responsible for expanding the frontier of Sikh Empire to beyond the Indus River right up to the mouth of the Khyber Pass. In 1831, he opposed moves by Ranjit Singh to appoint Kharak Singh as his successor as Maharaja of the Sikh Empire.[citation needed] At the time of his death, the western boundary of the empire was Jamrud. He served as governor of Kashmir, Peshawar and Hazara. He established a mint on behalf of the Sikh Empire to facilitate revenue collection in Kashmir and Peshawar. Hari Singh Nalwa was born in Gujranwala, Punjab to Gurdial Singh and Dharam Kaur, who were Uppal , Khatri by caste. After his father died in 1798, he was raised by his mother. In 1801, at age ten, he took Amrit Sanchar and w...
Post a Comment
Read more

Let's Football

Football refers to a number of sports that involve, to varying degrees, kicking a ball with the foot to score a goal. Unqualified, the word football is understood to refer to whichever form of football is the most popular in the regional context in which the word appears: association football (known as soccer in some countries) in the United Kingdom; gridiron football (specifically American football or Canadian football) in the United States and Canada; Australian rules football or rugby league in different areas of Australia; Gaelic football in Ireland; and rugby football (specifically rugby union) in New Zealand. These different variations of football are known as football codes. Various forms of football can be identified in history, often as popular peasant games. Contemporary codes of football can be traced back to the codification of these games at English public schools in the eighteenth and nineteenth centuries. The expanse of the British Empire allowed these rules of foo...
Post a Comment
Read more

Starting Mobile Phones

A mobile phone (also known as a cellular phone, cell phone, hand phone, or simply a phone) is a  phone  that can make and receive  telephone calls  over a  radio link  while moving around a wide geographic area. It does so by connecting to a  cellular network  provided by a  mobile phone operator , allowing access to the  public telephone network . By contrast, a  cordless telephone  is used only within the short range of a single, private base station. In addition to telephony, modern mobile phones also support a wide variety of other  services  such as  text messaging ,  MMS ,  email , Internet access, short-range wireless communications ( infrared ,  Bluetooth ), business applications, gaming, and photography. Mobile phones that offer these and more general computing capabilities are referred to as  smartphones . The first hand-held cell phone was demonst...
Post a Comment
Read more