Often astronomers can detect the presence of a star in a binary system without seeing it, they can tell it is there by observing the effect of its gravity on the second star Sometimes with binary stars, one star blocks the light from the other star and the system is called an eclipsing binary.
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More than half of all stars are members of star systems ( groups
of two or more stars). Our sun is not. Star systems with two stars
are called double stars or binary stars. Star systems with three
stars are called triple stars. Often astronomers can detect the
presence of a star in a binary system without seeing it, they can
tell it is there by observing the effect of its gravity on the
second star Sometimes with binary stars, one star blocks the light
from the other star and the system is called an eclipsing binary.
Scientists have discovered planets around stars by observing how a
star wobbles very slightly back and forth Over 300 extrasolar
planets have been found according to Space.com Most of the
extrasolar planets found so far are massive gas giants with large
influence on their stars gravity. First ever photo of an extrasolar
planet, a Jupiter-sized gas giant. The so-called "habitable zone"
around a star is a belt in which liquid water could exist on the
surface in lakes, rivers or oceans. Too close to its stellar parent
and a planet would be too hot, while an orbit too far out would
yield only a frozen world, NASA scientists have said. Quote from
Galaxies are giant structures that contain hundreds of billions of
stars, Oh, by the wayThere are billions of galaxies in the universe
Galaxies contain single stars, double stars, star systems and lots
of gas and dust between the stars. Astronomers classify most
galaxies into three main categories: spiral galaxies, elliptical
galaxies, irregular galaxies Spiral galaxies have arms that spiral
outward, like
pinwheelstutorial/example_face_on_spiral.jpgHubbleBeauty/NGC1512BarredSpiralGalaxy.jpg
Our solar system exists in the Milky Way galaxy, and is about
25,000 light-years away from the center of the Milky Way Our solar
system is about two-thirds of the way out on one of the spiral arms
of the Milky Way We cant see the center of the Milky Way due to the
massive cloud of gas and dust between the sun and the center
Elliptical galaxies look like flattened balls Have little gas and
dust between the stars so new stars can not form Ellliptical
galaxies only contain old starsjpegMod/PIA08696_modest.jpg Some
galaxies dont have a regular shape, they are called irregular
galaxies The Large Magellanic Cloud is an irregular galaxy
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