The XDF is a small fraction of the angular diameter of the full moon. If the earth had no tilt, we would have no seasons. During summer and winter, the sun is shining on only one of the hemispheres. For example, the Moon, at its present distance from Earth, has an angular diameter of 0.5°, or 30'. What is the Sun's diameter in kilometers? A) Picture -Both galaxies are 1 cm in diameter, and 25 cm apart. Major levels of structure: planets, moon, asteroids and comets, the Sun= solar system, The Sun and all stars we can see make up the Milky-Way Galaxy (galaxy= a great island of stars in space, containing a few hundred million to a trillion or more stars), etc. If you could change the layout of the solar system, which of the following would cause a lunar eclipse to occur at least once every month in this hypothetical situation? The horizon is the boundary between the Earth and sky. A one-mile-long line painted on the face of the Moon would appear from Earth to … The tilt of Earth's axis causes different portions of the Earth to receive more or less direct sunlight at different times of year. Moon distances vary so diameter … • The Moon is about 380,000 km away but only 3,300 km diameter • The Sun is 150,000,000 km away and about 1,400,000 km diameter An object can achieve escape velocity if it gains enough orbital energy causing it to go from bound to an unbound orbit. The sun has a diameter of 1.4 million km. Longitude, however, does not vary. 3) The Moon has an angular size of 30 minutes and its distance from the Earth is about 240,000 miles. You should also make use of the small-angle approximations $\arctan(x)\approx x$ for small x in radians. Specifically, for small angles, it is the diameter divided by the distance. Precession is the gradual wobble that alters the orientation of the earths' axis in space. What is this in arcminutes? The variation in Earth-Sun distance over the course of each year has virtually no effect on the seasons. The exceptions are during its periods of apparent retrograde motion, when Mars appears to move __________ relative to the stars. (a) If the Moon’s diameter were doubled, going from an angular size of ½° to an angular size of 1°, there would be more total solar eclipses because the opportunity to cover the Sun’s disk would be increased. Which statement best describes how variation in the Earth-Sun distance affects the seasons? Without re-inputting, click "seconds" and then click "calculate". Each appears to be about ½° across from ground-based observers. - Speed - The distance an object travels per unit time. (Click "Show Moon with flat orbit" to see this situation.) We don't see an eclipse b/c the Earth, Moon, and the Sun aren't in line with each other on every new and full moon. The angular diameter depends on the distance between the two objects and the diameter of the object being viewed. Therefore, if we go back far enough, we'd reach the point where expansion began. Therefore, tonight's night sky in these two places: n winter, Earth's axis points toward the star Polaris. A week after full moon, the Moon's phase is: If there is going to be a total lunar eclipse tonight, then you know that: When we see Saturn going through a period of apparent retrograde motion, it means: Earth is passing Saturn in its orbit, with both planets on the same side of the Sun. No, b/c the moon would be behind the Earth at that time. What conditions must exist for a solar eclipse to occur? Basically, the tidal force stretches Earth to create one tidal force facing the Moon and one tidal force opposite of the moon. The zenith is the point directly overhead; the meridian is an imaginary half circle stretching from the horizon due south to the horizon due north, passing through the zenith. The phase of the Moon must be new and the Moon must be passing through Earth's orbital plane. Remember to show all of your work for every problem, and to write your final answers in complete English sentences.. Circumference = 2πr = 2π (6371 km) = 40000 km equator to pole distance = Circumference 4 =40000 km, 4 = 10000 km, Thus, 1◦ = 10000 km 90◦ = 111 km Each arcminute of latitude represents 1.85 … Means that it makes a half turn in half the orbit. Angular size has two measurements, the angular distance and the angular diameter. The Hubble Ultra Deep Field is an image of a small area of space in the constellation Fornax, created using Hubble Space Telescope data from 2003 and 2004. So what is the cause of the seasons? The fact that we always see the same face of the Moon tells us that: The Moon's rotation period is the same as its orbital period. A model in science is a conceptual representation whose purpose is to explain and predict observed phenomena. a) 0.5 b) 30 c) 50 d) 1800 e) 60.5 Synchronous rotation means that the Moon rotates on its axis in the same amount of time it takes for it to orbit Earth. The phase of the Moon must be full and the Moon must be passing through Earth's orbital plane. At most times, Mars appears to move __________ relative to the stars. Summer is northern. – From the information in the table, calculate the maximum and minimum angular size of each moon and object as viewed from Europa. For example, comets' orbits can change if they get too close to a planet. The average angular diameter of the Moon, as seen from the Earth, is about 31 arcminutes. We also know that the AU is about 390 times the average Earth-moon distance. Part 4: Computation. If we use the modern knowledge that the Moon is about 3,500 kilometers in diameter, we can estimate its distance just as we did for the friend's distance above. In reality, the Moon's orbit about Earth is tilted (by about 5°) with respect to Earth's orbit about the Sun. The Sun AND the Moon project an angular size of __ arc minutes on the sky. It is the sun's apparent location along the ecliptic that determines which constellations we see at night. No unit conversions are needed. (Hint: use the Moon data given in the previous question.) This difference is what causes the tidal forces, or "stretching forces." It's not a small effect. You use linear diameter when you order a 16-inch pizza—the pizza is 16 inches in diameter. Which of the following planets would you expect to have seasons most like Earth's? Astronomy had practical benefits for timekeeping, keeping track of seasonal changes, and navigation. Two stars that are in the same constellation: May actually be very far away from each other.