Astronomy Reference Libraries

Page 2 of about 165 Articles
Radio Telescope
2010-10-08 17:45:24

Radio telescopes, used in tracking and collecting data from satellites and space probes, are a form of directional radio antenna used in radio astronomy. They operate on the radio frequency portion of the electromagnetic spectrum where they detect radio sources. Radio telescopes are large parabolic antennas used singly or in an array and are located far from major centers of population in...

2010-09-24 17:50:57

A telescope, designed to aid the observation of remote objects, collects some form of electromagnetic radiation (such as visible light). The Netherlands developed the first known practical telescope in the 17th century. The term "telescope" was termed in order to describe Galileo's instruments in 1611. However, Galileo was not the inventor of the telescope. It was Hans Lippershey, Zacharias...

2010-09-16 16:09:47

A planisphere is a star chart analog, adjustable to display the visible stars for any time or and date, consisting of two adjustable disks that rotate on a common pivot. The Planisphere was pre-dated by the astrolabe; however, the planisphere was first described in the 11th century by Abu Rayhan al-Biruni. The name planishphere was not coined until 1624 by Jacob Bartsch, Johannes Kepler's...

Virgo Cluster
2010-09-16 15:18:29

The Virgo Cluster consists of galaxies at a distance of around 59 Mly away in the constellation Virgo. Containing between 1300 to 2000 galaxies the Virgo Cluster is the heart of the Local Supercluster. Its mass is estimated at 1.2 × 1015 M☉ out to 8 degrees of the cluster's center or a radius of about 2.2 Mpc. Most of the brighter galaxies in the cluster were discovered by Charles...

Magellanic Clouds
2010-09-16 15:14:03

The two Magellanic Clouds (or Nubeculae Magellani), composed of the Large Megellanic Cloud and the Small Magellanic Cloud, are irregular dwarf galaxies visible in the southern hemisphere. They are members of our Local Group and orbit the Milky Way galaxy. Persian astronomer Al Sufi, in 964, was the first to have written anything about the Magellanic Clouds proving they have been known since...

NGC 5866 Group
2010-09-16 15:00:46

The NGC 5866, located in the Draco constellation, is named after the galaxy with the highest magnitude however some catalogs list NGC 5907 as the brightest member. The M51 Group and the M101 Group are NGC 5866 closest neighbor. The distances between these groups are similar which suggest the three groups are part of a single large, loose, elongated group. However, most identification methods...

M101 Group
2010-09-13 17:13:25

The M101 Group, one of many in the Virgo Supercluster, is located in Ursa Major and named after the brightest galaxy in the group, the Pinwheel Galaxy (M101). The group is composed mostly of members that are companions of the Pinwheel Galaxy. The M51 Group and the NGC 5866 Group are M101's closest neighbor. The distances between these groups are similar which suggest the three groups are...

M96 Group
2010-09-13 17:11:43

The M96 Group (also known as the Leo I Group), one of many in the Virgo Supercluster, is located within the Leo constellation and contains between 8 and 24 galaxies, including three Messier objects. The Leo Triplet, which is physically near M96 Group, and M96 may actually be separate parts of a much larger group.

M81 Group
2010-09-13 17:09:55

The M81 Group, containing the well known galaxies Messier 81 and Messier 82, is a group of galaxies within the constellation Ursa Major. Along with Messier 81 and 82 are several other galaxies with apparent brightness. The center, located at an approximate distance of 3.6 Mpc, is one of the nearest groups to the Local Group. The total estimated mass of the group is (1.03 ± 0.17) ×...

M51 Group
2010-09-13 17:07:12

The M51 Group, located in Canes Venatici, is named after the brightest galaxy in the group, the Whirlpool Galaxy (M51A). The few other notable members include the companion galaxy to the Whirlpool Galaxy (M51B) and the Sunflower Galaxy (M63).

Word of the Day
  • One of a religious order living in a convent or in community; a monk: opposed to anchoret or hermit (one who lives in solitude).
  • A social bee.
This word comes from the Latin 'coenobium,' convent, which comes from the Greek 'koinobios,' living in community.