Motion Of The Sky Name Location

Motion Of The Skyname Locati

Motion of the Sky Name: _________________________________________ Location: ______________________________________ First Observation Date:___________ Time: _______ Direction:_______ Phase:_____________________ Second Observation Date:___________ Time: _______ Direction:_______ Phase:____________________

ASTRO 112 Naked Eye Observing Project Note: This is a project that can be done with the naked eye under good weather and light conditions. The use of binoculars is optional but helpful. The Earth rotates about its axis once every 24 hours, causing the sky, Sun, Moon, and stars to appear to move across the sky. This rotation occurs counterclockwise when viewed from above the North Pole, making the eastern horizon appear to rise and the western horizon set with celestial objects.

For this project, select a constellation visible roughly one hour after sunset on the eastern horizon or, if not visible there, on the southern horizon. Ideal constellations for observation during late summer and early fall include Scorpius and Sagittarius, while Canis Major and Orion are suitable in late winter and early spring. Use a current northern hemisphere evening skymap to identify these constellations and their typical appearance around 8-9 PM.

Part I Procedure involves identifying a fixed reference point, drawing your initial constellation observation with key details, then revisiting the same location after about an hour to note the new position of the constellation. On a separate sheet, sketch a broader sky area including three additional constellations visible at the same time, noting your location, facing direction, and time. These observations help illustrate the apparent motion of celestial objects caused by Earth's rotation.

Questions related to Part I include estimating the angular displacement of your constellation from the horizon, calculating the time it takes for a star to set based on your observations, and explaining why telescopes reveal this motion more clearly, which is due to their ability to magnify apparent stellar motion.

Part II requires repeating the wide-area sky sketch several weeks later from the same location and similar time. It involves comparing initial and subsequent positions of the constellations, attributing shifts to Earth's orbit around the Sun, which causes stars to rise approximately four minutes earlier each day. Consider whether the constellations have moved closer to the eastern or western horizon and explain if this aligns with expectations based on Earth's orbital motion.

Additional questions include understanding why winter constellations are not visible during summer nights and locating them in the summer sky, estimating the fraction of the year between observations, and determining how much of the celestial sphere the constellations have traversed during this interval.

Paper For Above instruction

The Earth's rotation and orbit around the Sun create observable motions in the night sky, which can be explored through naked eye observations and simple sketches. Recognizing these motions helps deepen our understanding of celestial mechanics and Earth's position relative to other celestial objects. This observational project involves tracking the position of a chosen constellation over time to quantify its apparent movement due to Earth's rotation and revolution.

Initially, selecting a constellation visible on the eastern horizon about an hour after sunset provides an optimal vantage point. Constellations such as Scorpius and Sagittarius are ideal in late summer and early fall, while Canis Major and Orion are appropriate targets in late winter and early spring. Using a current evening skymap, observers can identify these constellations and their expected positions around 8-9 PM, serving as a reference point for measurements.

During the first observation, individuals are instructed to find a fixed terrestrial landmark—such as a building, mountain, or pole—and draw their initial view of the constellation relative to this point, noting the time and direction faced. After waiting approximately one to two hours, they revisit this spot to record the new position of the same constellation. Such repeat observations visually demonstrate the east-to-west motion of stars caused by Earth's rotation.

Analysis of this data involves estimating how far above the horizon the constellation is and how much it appears to have moved across the sky. Since the Earth completes a rotation every 24 hours, stars seem to set roughly 15 degrees per hour (360 degrees / 24 hours), although local horizon effects and atmospheric refraction can cause minor variations. From the observed displacement, one can approximate the time of sunset or star setting, based on how long it takes for the constellation to disappear from view.

Furthermore, telescopic observations reveal this apparent motion more dramatically due to the magnified view, allowing more precise tracking of a star’s position. Under a telescope, subtle movements in stellar positions become more apparent, illustrating the Earth's rotation with greater clarity, including drift and shift over short intervals. This also emphasizes how Earth's rotation causes the daily pattern of star rise and set, and how telescopes enhance our perception of these motions.

Several weeks after the initial observations, the same broad sky area is sketched again from the same location. Due to Earth's revolution around the Sun, constellations appear to shift slightly earlier in their rising and setting times. These shifts are approximately four minutes earlier each day, leading to notable positional changes over weeks. Comparing the initial and subsequent sky maps shows the gradual westward movement of the constellations relative to Earth's position in its orbit.

The observed shifts align with expectations, as the extra four-minute daily advance equates to a cumulative shift of about 2 hours and 20 minutes per month, resulting in notable displacement in the sky. This reinforces that Earth's orbital motion, combined with its axial rotation, shapes our apparent celestial motions.

Additionally, seasonal visibility of constellations explains why certain star groups are absent in summer skies. For example, winter constellations like Orion are prominent in winter nights but are located on the opposite side of Earth’s orbit during summer, making them invisible due to the Sun’s position in the sky during that season. Instead, in summer, the star groups visible are those aligned with Earth's seasonal positioning, corresponding to different parts of the celestial sphere.

The fraction of the year between observations, such as several weeks, corresponds to a specific portion of Earth's 365.25-day orbit. For example, a 4-week interval represents approximately 1/13 of the year (~0.19). During this period, the constellations will have moved across about 30-40 degrees of the sky, accounting for Earth's orbital motion and the consequent shift in the background stars' positions.

Overall, systematic naked eye observations offer compelling evidence of Earth's rotation and revolution, illustrating the dynamic nature of our night sky. These observations confirm theoretical models and provide experiential understanding of celestial mechanics, emphasizing the importance of repeated observations over time to grasp the complexity of lunar, solar, and stellar motions relative to our planet.

References

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