In addition, the stroke of the Earth around the Sun shows us a different portion of the sky depending on the time of year. The Sun, Moon, planets, have a perceptible movement over days or weeks to the background of stars while stars are so distant that they appear stationary in a human life.
It includes a rotating disc whose operation is exactly the same as the disc you see on this screen! It is therefore valid for all days of the year and all hours of the night. Stars spend 90 percent of their lives in their main sequence phase. Now around 4. As stars move toward the ends of their lives, much of their hydrogen has been converted to helium. Helium sinks to the star's core and raises the star's temperature—causing its outer shell of hot gases to expand.
These large, swelling stars are known as red giants. The red giant phase is actually a prelude to a star shedding its outer layers and becoming a small, dense body called a white dwarf.
White dwarfs cool for billions of years. Some, if they exist as part of a binary star system , may gather excess matter from their companion stars until their surfaces explode, triggering a bright nova.
Eventually all white dwarfs go dark and cease producing energy. At this point, which scientists have yet to observe, they become known as black dwarfs. Massive stars eschew this evolutionary path and instead go out with a bang—detonating as supernovae. While they may appear to be swelling red giants on the outside, their cores are actually contracting, eventually becoming so dense that they collapse, causing the star to explode.
These catastrophic bursts leave behind a small core that may become a neutron star or even, if the remnant is massive enough, a black hole. The familiar eyeball shape of the Helix Nebula shows only two dimensions of this complex celestial body.
But new observations suggest it may actually be composed of two gaseous disks nearly perpendicular to each other. In cities and other densely populated areas, light pollution makes it nearly impossible to stargaze.
By contrast, some parts of the world are so dark that looking up reveals the night sky in all its rich celestial glory. Ancient cultures looked to the sky for all sorts of reasons. By identifying different configurations of stars—known as constellations—and tracking their movements, they could follow the seasons for farming as well as chart courses across the seas.
There are dozens of constellations. Many are named for mythical figures, such as Cassiopeia and Orion the Hunter. Today astronomers use constellations as guideposts for naming newly discovered stars.
Constellations also continue to serve as navigational tools. In the Southern Hemisphere, for example, the famous Southern Cross constellation is used as a point of orientation. Meanwhile people in the north may rely on Polaris, or the North Star, for direction. Polaris is part of the well-known constellation Ursa Minor, which includes the famous star pattern known as the Little Dipper. All rights reserved. Neutron Star An artist's rendering shows a neutron star —located 50, light-years from Earth—that flared up so brightly in December that it temporarily blinded all the x-ray satellites in space and lit up the Earth's upper atmosphere.
A star is born The life cycle of a star spans billions of years. Use white hours when standard time is in effect and orange hours when clocks are set for daylight-saving summer time. The Star Wheel's large oval shows the whole sky, and the oval's curved edge represents the horizon you're facing.
Once outside, hold the Star Wheel out in front of you and look at the yellow "Facing" labels around the oval.
Turn the entire wheel so that the yellow label for the direction you're facing is on the bottom, with the lettering right-side up. If you're unsure of your directions, just remember where the Sun sets; that's west. Once you've set the date and time, turn the Star Wheel so the 'Facing' label at the bottom of the oval matches the direction in the sky you're looking.
Kelly Beatty Now the stars above the map's horizon should match the real stars in front of you. Remember that star patterns will look much larger in the sky than they do on the map. The farther up from the edge of the oval the stars appear, the higher up they'll be shining in your sky. Stars in the center of the oval will appear directly overhead.
If you'd like a more visual guide, watch our video on how to use a star wheel. It includes the names of the brightest stars and the most prominent constellations. Depending on how dark the sky is in your area, there may be more stars overhead than are shown on the map. Everyone's sky looks a little different. If there are fewer stars visible to you than appear on the Star Wheel, try to find an observing site that is not flooded by house or streetlight. Also, the longer you're outside, the better the chance that your eyes will adapt to the darkness and the more stars you'll be able to see.
By drawing a line through the 'pointer' stars at the end of the Big Dipper's bowl, you can easily find the North Star. Kelly Beatty Stars in the northern sky do not rise or set — instead, throughout the night they seem to slowly turn counterclockwise around Polaris, the North Star, which seems to stay in the same place in the sky no matter what time of night or season of the year.
So let's find the North Star! Begin by locating the Big Dipper. This giant spoon is actually part of a larger constellation called Ursa Major, the Great Bear. Find the two end stars in the Dipper's bowl — look opposite the handle. They're known as the "pointers. Because a line drawn between them and extended away from the bottom of the bowl leads you to Polaris, the North Star. Now that you know how find Polaris, you also know how to find due north no matter where you are in the Northern Hemisphere!
Planets aren't plotted on the Star Wheel, but they travel across the sky along an imaginary line called the ecliptic.
Kelly Beatty The Moon and planets aren't shown on the map because their day-to-day movements are more involved than the motions of the stars. However, the curved line coursing across the map is called the ecliptic. It represents the path in the sky that brightest planets follow. If you see a bright "star" shining with a steady glow on or near this curved line, and the object isn't plotted on the Star Wheel, you're looking at a planet.
The Moon likewise travels very near the ecliptic in its orbit around Earth.
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