In the 10th century, Abd al-Rahman al-Sufi carried out observations on the stars and described their positions, magnitudes and star color, and gave drawings for each constellation, in his Book of Fixed Stars.

The observations show that the cloud is asymmetrical and matches the pattern of X-ray binaries ( binary star systems containing black holes or neutron stars ), mostly on one side of the galactic center.

For stars, in the absence of extensive observations at many wavelengths, it usually must be computed assuming an effective temperature.

They do not rely on direct observations of the stars.

In astronomy, Celsius began a series of observations using colored glass plates to record the magnitude ( a measure of brightness ) of certain stars.

He made observations of eclipses and various astronomical objects and published catalogues of carefully determined magnitudes for some 300 stars using his own photometric system ( mean error = 0. 4 mag ).

Low surface brightness dwarf galaxies are important sources of information for studying dark matter, as they have an uncommonly low ratio of visible matter to dark matter, and have few bright stars at the center which would otherwise impair observations of the rotation curve of outlying stars.

Rubin's observations and calculations showed that most galaxies must contain about ten times as much “ dark ” mass as can be accounted for by the visible stars.

Full moons are generally a poor time to conduct astronomical observations, since the bright reflected sunlight from the moon overwhelms the dimmer light from stars.

There he worked on James Bradley's stellar observations to produce precise positions for some 3, 222 stars.

In these observations, he discovered a fourth body, and also observed that the four were not fixed stars, but rather were orbiting Jupiter.

The stars were first defined as a separate constellation by Petrus Plancius, who created twelve new constellations based on the observations of Pieter Dirkszoon Keyser and Frederick de Houtman.

* Coelum australe stelliferum ( 1763 ) ( edited by J. D. Maraldi ), giving zone observations of 10, 000 stars, and describing fourteen new constellations

Telescopic observations revealed two distinct types of clusters, one of which contained thousands of stars in a regular spherical distribution and was found all across the sky but preferentially towards the centre of the Milky Way.

Detailed observations of many binary star systems were collected by astronomers such as William Struve and S. W. Burnham, allowing the masses of stars to be determined from computation of the orbital elements.

The first solution to the problem of deriving an orbit of binary stars from telescope observations was made by Felix Savary in 1827.

Since the mid-1990s, starspot observations have been made using increasingly powerful techniques yielding more and more detail: photometry showed starspot growth and decay and showed cyclic behavior similar to the Sun's ; spectroscopy examined the structure of starspot regions by analyzing variations in spectral line splitting due to the Zeeman Effect ; Doppler imaging showed differential rotation of spots for several stars and distributions different from the Sun's ; spectral line analysis measured the temperature range of spots and the stellar surfaces.

Other famous Arabic star catalogues include Alfraganus ' A compendium of the science of stars ( 850 ) which corrected Ptolemy's Almagest ; and Azophi's Book of Fixed Stars ( 964 ) which described observations of the stars, their positions, magnitudes, brightness and colour, drawings for each constellation, and the first descriptions of Andromeda Galaxy and the Large Magellanic Cloud.

The observations made were made from the Paris Observatory and so it describes mostly northern stars.

Because the stars were all born at roughly the same time, the different properties of all the stars in a cluster are a function only of mass, and so stellar evolution theories rely on observations of open and globular clusters.

* The Ptolemaic model of planetary motion: Based on the geometrical model of Eudoxus of Cnidus, Ptolemy's Almagest, demonstrated that calculations could compute the exact positions of the Sun, Moon, stars, and planets in the future and in the past, and showed how these computational models were derived from astronomical observations.

However, unlike the backstaff, the sextant allows direct observations of stars.

Tombaugh noticed such a moving object in his search, near the place predicted by Lowell, and subsequent observations showed it to have an orbit beyond that of Neptune.

However, spectropolarimetric observations of SN 2009dc showed it had a polarization smaller than 0. 3, making the large asphericity theory unlikely.

Spencer Jones ' work of 1939 showed that the positions of the Sun actually observed, when compared with those obtained from Newcomb's formula, show the need for the following correction to the formula to represent the observations:

In 2007, observations showed a protoplanetary disc around the companion, Mira B.

Neptune's rings are very unusual in that they first appeared to be composed of incomplete arcs in Earth-based observations, but Voyager 2's images showed them to be complete rings with bright clumps.

The structure of Darwin's argument showed the influence of John Herschel, whose philosophy of science maintained that a mechanism could be called a vera causa ( true cause ) if three things could be demonstrated: its existence in nature, its ability to produce the effects of interest, and its ability to explain a wide range of observations.

The observations showed that the debris ring is smooth and symmetric.

Spectroscopic observations thus showed that nebulae were made of extremely rarefied gas.

Later observations ( by Hubble himself, among others ) showed Hubble's belief to be correct and the S0 class was included in the definitive exposition of the Hubble sequence by Allan Sandage.

Spacecraft observations showed that the gases ejected from the nucleus were 80 % water vapor, 17 % carbon monoxide and 3 – 4 % carbon dioxide, with traces of hydrocarbons although more recent sources give a value of 10 % for carbon monoxide and also include traces of methane and ammonia.

Subsequent observations showed Halley's deuterium ratio to be far higher than that in found in the Earth's oceans, making such comets unlikely sources for Earth's water.

The initial observations which showed its chaotic behaviour were made by Wiśniewski.

Emil Julius Gumbel ( 1958 ) showed that for any well-behaved initial distribution ( i. e., F ( x ) is continuous and has an inverse ), only a few models are needed, depending on whether you are interested in the maximum or the minimum, and also if the observations are bounded above or below.

These observations showed that the thickness of Titan's atmosphere is.

Extended Uhuru observations of Cygnus X-1 showed fluctuations in the X-ray intensity that occurs several times a second.

Since these observations agreed with theory for elastic waves, they showed that the Earth could be treated as elastic in studies of seismic waves.

The solar luminosity is about 0. 07 percent brighter during solar maximum than during solar minimum but observations from spacecraft in the 2000s showed that the ratio of ultraviolet to visible light is much more variable than previously thought.

Spectroscopic observations thus showed that planetary nebulae consisted largely of extremely rarefied ionised oxygen gas ( OIII ).

During the 20th century, observations showed that H II regions often contained hot, bright stars.