Hubble image of stars near the center of 47 Tuc
The second brightest globular cluster in the sky, after Omega Centauri. To the unaided eye it looks like a misty star.
galaxy A vast assemblage of stars, nebulae, etc., composing an island universe separated from other such assemblages by great distances. The sun and its family of planets is part of a galaxy commonly called the Milky Way.
Cluster Color-Magnitude Diagrams and the Age of Stars provides colour indices and magnitude data for the Pleiades and 47 Tuc, a globular cluster so that you can plot colour-magnitude diagrams and determine cluster ages.
How old is Sunlight?
Galaxy: A large assemblage of stars (and sometimes interstellar gas and dust), typically containing millions to hundreds of billions of member stars.
It turns out that we can, in fact, tell the age of stars. There are different classes of stars, not surprisingly called spectral classes. These are, from the most massive to the least, O, B, A, F, G, K, M and the newly discovered L class.
A Hubble Space Telescope image of stars in the globular cluster M22.
Click on image for full size
NASA, ESA, and K. Sahu (STScI)
The pinpoints of light that you see in the night sky are stars.
In 1979 an engineer responsible for navigation of the Voyager I spacecraft noticed a strange mushroom-like object on the limb of Io, in an image of stars used to check the positioning of the spacecraft.
Recent research suggests that a large percentage of stars are part of systems with at least two stars. Binary star systems are very important in astrophysics, because observing their mutual orbits allows their mass to be determined.
The percentage of stars with such anomalies is of the order of 4%. Spite and Spite (1986) have shown that, in these stars, Li behaves normally as in other halo dwarfs.
In telescopes, turbulence produces a very wide range of effects on the image of stars and planets that has been variously described as "boiling", "churning", "wavering", "wobbling" or "shimmering".
Novas are less spectacular and more common; they increase in brightness only by a few thousand times, and several occur in our galaxy every year. Supernovas can occur in that small percentage of stars having a mass greater than 8 to 10 times the ...
Color filters were used to sample light emitted by sulfur ([S II]), oxygen ([O III]), and hydrogen (H-α). The color image has been superimposed on a black and white image of stars in the same field also taken with the HST.
 See also: Nebula, Star, Earth, Giant, Cluster
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