knowverseCan you find the zenith or tell a constellation from an asterism? Test your understanding of the imaginary reference points astronomers use to map the sky.
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The celestial sphere maps apparent directions. The stars themselves lie at different distances.
Astronomers expand this dome into a complete, imaginary bubble called the Celestial Sphere.
From the Knowverse course text.
The Zenith is the location in the sky situated directly above the observer's head.
To fix this, astronomers use a point called the Zenith, which is the location in the sky directly above your head.
From the Knowverse course text.
The visible upper arc of the local meridian runs from the north horizon through the zenith to the south horizon. The full meridian is a great circle.
The Meridian is a great circle that starts at the North point on your horizon, goes through your Zenith, and ends at the South point on your horizon.
From the Knowverse course text.
The Celestial Equator serves as the baseline for declination, giving it a value of 0 degrees.
It would be 0 degrees. This serves as the neutral baseline for the entire sky.
From the Knowverse course text.
Right ascension divides the full circle into 24 hours, with each hour corresponding to 15 degrees.
Since the Earth completes one full turn every 24 hours, the sky appears to do the same. Because of this, astronomers measure Right Ascension in hours, minutes, and seconds.
From the Knowverse course text.
Astronomers use the Vernal Equinox as the Zero Hour mark and measure Right Ascension eastward from it.
In the sky, we use a specific point in space called the Vernal Equinox. This point is our 'Zero Hour.' We start counting Right Ascension eastward from this location.
From the Knowverse course text.
The celestial sphere is divided into 88 official, non-overlapping regions.
To solve this problem, astronomers divided the entire sky into 88 official regions called constellations.
From the Knowverse course text.
The Big Dipper is an informal pattern called an asterism, which sits inside the official constellation Ursa Major.
While everyone knows the shape of the Big Dipper, it is actually just a small part of the constellation Ursa Major.
From the Knowverse course text.
Daily diurnal motion happens because Earth rotates from west to east, making stars appear to drift in the opposite direction.
Every night, the stars follow a very predictable path, rising in the East and setting in the West. This specific direction happens because the Earth actually rotates from West to East.
From the Knowverse course text.
A circumpolar star remains above that observer's horizon as it circles a celestial pole. Which stars qualify depends on the observer's latitude.
These special stars are known as Circumpolar Stars, and they appear to travel in a tight circle around the pole. Because they never 'set' below the ground, you can see them at any time of the night, all year round.
From the Knowverse course text.
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The celestial sphere is an imaginary surface used to map directions in the sky. Stars lie at different distances, but plotting their apparent positions on one sphere makes finding them easier. The model describes where to look. It does not put stars at the same physical distance from Earth.
The horizon marks the boundary of the visible sky. Your zenith is directly overhead, and your nadir points in the opposite direction. The local meridian crosses the sky through the north horizon point, zenith and south horizon point. These reference points depend on where the observer stands on Earth.
Astronomers expand this dome into a complete, imaginary bubble called the Celestial Sphere.
From the Knowverse course text.
Projecting Earth's equator into the sky gives the celestial equator. Declination measures angles north or south of it, with zero degrees on the equator. Right ascension measures eastward from the vernal equinox, using hours, minutes and seconds. Its full circle has 24 hours, providing a second coordinate for locating objects.
The sky has 88 official constellation regions. An asterism is a recognizable pattern, such as the Big Dipper within Ursa Major. Earth's rotation makes stars appear to move across the sky. At a given observing location, circumpolar stars stay above the horizon as they circle the celestial pole.
To solve this problem, astronomers divided the entire sky into 88 official regions called constellations.
From the Knowverse course text.
Sources: Mapping the Night Sky. Each question or step includes an excerpt from the course.
