Miscellaneous astronomy factoids

Question 1

diameter of the earth at the equator and the poles?

Answer 1

equator: 12,756.1 km (7926.28 miles) poles: 12,713.5 km (7899.80 miles)

Question 2

earth’s circumference at the equator?

Answer 2

40,008 km (24,859.82 mi)

Question 3

average distance from earth to sun

Answer 3

149,669,180 km (93,020,000 mi) This is also the astronomical unit.

Question 4

average distance from earth to moon

Answer 4

384,403.1 km (238,857 mi)

Question 5

what is the Earth’s gravity?

Answer 5

“Earth’s gravity” refers to the acceleration that the Earth imparts to objects on or near its surface. The rate is 9.80665 m/s². This quantity is informally known as little g (contrasted with G, the gravitational constant, known as big G).

Question 6

What is the “gravitational constant”?

Answer 6

The gravitational constant, denoted G, is an empirical physical constant involved in the calculation of the gravitational attraction between objects with mass. It appears in Newton’s law of universal gravitation and in Einstein’s theory of general relativity. It is also known as the universal gravitational constant, Newton’s constant, and colloquially Big G.

Question 7

How fast does Earth rotate?

Answer 7

23 hr 56 min 4.09053 sec, but it takes an additional 4 minutes for Earth to revolve to the same position relative to the sun as the day before, thus leading to approx. 24 hrs.

Question 8

How long is Earth revolution around the sun?

Answer 8

365.2425 days

Question 9

How can you estimate time to sunset w/ your hand?

Answer 9

15 minutes per finger

Question 10

When did Sputnik fly?

Answer 10

The world’s first artificial satellite, Sputnik on 4 October 1957

Question 11

how many degrees of arc does the moon subtend in the sky

Answer 11

The angular diameter of the moon is about 30 arc-seconds , or 1/2 a degree, or 1/720 of a full circle.

Question 12

why does the length of moonset vary by date?

Answer 12

The length of the sunset/moonset depends on the date and latitude of observation for the same reason that daylight hours for a day vary depending on date and latitude. On the solstice, for example, the moon will be setting the maximum distance north or south of west. Thus, the moon sets at the shallowest possible angle giving the slowest moon set.

Question 13

How do telescopes take color photos?

Answer 13

To retain as much detail as possible, telescopes operate only in black and white. Astronomers take multiple photos using different filters that collect light from the entire range of the spectrum, including areas undetectable to the human eye. “In general, we boost the colors quite a bit to bring out the features we’re seeking,” Mr. Levay said. “But we don’t make this stuff up — the colors are real.”

Question 14

How long does light take to travel from the sun to earth?

Answer 14

About 8 min 20 sec

Question 15

What is the sun’s composition?

Answer 15

About 70% hydrogen, 28% helium, 2% remaining elements incl oxygen, carbon, neon, iron, others.

Question 16

How many of our solar system’s planets ate terrestrial (rocky bodies)?

Answer 16

4: earth, mercury, Venus, mars

Question 17

What is special about Polaris?

Answer 17

Known as the Pole Star and the North Star , it lies almost directly above Earth’s North pole.

Question 18

What are two constellations near the equator?

Answer 18

https://classconnection.s3.amazonaws.com/803/flashcards/1494803/jpg/celestialsphintro_231x261-14389530D48320EA847.jpg

Question 19

How is Earth inclined from the Ecliptic?

Answer 19

23.5 deg to the celestial equator.

Question 20

Which plants have rings?

Answer 20

All four of the gas giants: Jupiter, Saturn, Uranus and Neptune

Question 21

How many rings does Jupiter have?

Answer 21

Currently known to have 4 main components. The ring system is faint and consists mainly of dust.

Question 22

How many rings does Saturn have?

Answer 22

It used to be that people said 12 rings, but closer observations have led people to think of the rings as an annular disk with local maxima and minima in density and brightness.

Question 23

How many rings does Uranus have?

Answer 23

13 rings have been found so far

Question 24

How many rings does Neptune have?

Answer 24

6 have been discovered so far.

Question 25

What is the angular size of the sun in the sky?

Answer 25

Approx. 30 arc minutes (half a degree), which happens to be the same as the moon.

Question 26

What is the angular width of your little finger at arm's length?

Answer 26

Approx. 30-40'

Question 27

What leads to the difference between the sidereal day and the solar day?

Answer 27

For a solar day, the Earth has to rotate to aim at the sun. But the Earth is moving around the sun in orbit, so the position of the sun relative to the stars changes. The angular difference between one night and the next is 360°/365 = 0.986°. Given the Earth's rotation of of 15°/hr, it takes approx. 3.9 min to rotate the additional 0.986° to point back to the sun. So, the solar day is longer by this 3.9 min.

Question 28

How quickly does the moon move across the sky?

Answer 28

Approx 12°/day.

Question 29

How long does the moon's cycle of phases take?

Answer 29

Approx 29.5 days. This is the synodic month .

Question 30

How long is the sidereal month ?

Answer 30

In 27.3 days, the moon completes one revolution and returns to its starting point on the celestial sphere.

Question 31

What is the ecliptic ?

Answer 31

The 12 constellations through which the Sun passes as it moves along the ecliptic.

Question 32

What are the 12 constellations of the astrological zodiac?

Answer 32

Aquarius         Libra Aries               Pisces Capricornus     Sagittarius Cancer             Scorpio Gemini             Taurus Leo                   Virgo

Question 33

What is the summer solstice ?

Answer 33

The point on the ecliptic where the Sun is at its northernmost point about the celestial equator. It represents the location in Earth's orbit where our planet's North Pole comes closest to pointing in the direction of the Sun.

Question 34

When does the summer solstice occur?

Answer 34

One or near June 21.

Question 35

When does the winter solstice occur?

Answer 35

6 months after the summer solstice: on or near December 21.

Question 36

Why do the solstices not occur at exactly the same day year to year?

Answer 36

Because the actual length of a year is not a whole number of days.

Question 37

What is the length of the day on the summer solstices?

Answer 37

In the Northern Hemisphere, it is the longest day; in the Southern Hemisphere, it's the shortest.

Question 38

Is the Earth's orbit elliptical?

Answer 38

It is actually almost a perfect circle, varying in distance from the Sun only by about 3% over the course of a year.

Question 39

Is it coldest when the Earth is farthest from the Sun?

Answer 39

Actually, the Earth is closest in early January, which is when it is coldest in the Northern Hemisphere.

Question 40

What is the equinox ?

Answer 40

The 2 points where the ecliptic intersects the celestial equator are when the Earth's rotation axis is perpendicular to the line joining the Earth and Sun. These are the equinoxes.

Question 41

How long is the Earth's precession cycle?

Answer 41

Approx 26,000 years.

Question 42

How long is the sidereal year ?

Answer 42

365.256 solar days.

Question 43

Why is the sidereal year 20 minutes longer than the tropical year?

Answer 43

Because of the effects of precession in Earth's spin.

Question 44

What is the length of the day on the equinox?

Answer 44

The center of the Sun spends a roughly equal amount of time above and below the horizon at every location on Earth, so day and night are about the same duration. However, in practical terms, day is longer, because when the Sun is below the horizon, its edge is still visible (not the center) and the atmosphere refracts light, which make daylight visible for a longer time.

Question 45

What is a tropical year ?

Answer 45

= solar year. | The time interval between vernal equinoxes in successive years.

Question 46

What causes the longer length of a sidereal year?

Answer 46

This is due to precession: the equinox position changes from year to year by approx 20 min 24 sec per year. The Earth's rotation axis changes orientation w.r.t. the Sun slightly from year to year, and the instance when the axis is perpendicular to the line from Earth to Sun occurs slightly sooner than we would expect in the absence of precession.

Question 47

How quickly does the sidereal year drift ouf sync with the seasons measured by a tropical year?

Answer 47

Approx 1 day every 72 yrs.

Question 48

How long does it take for your eyes to adapt to the dark?

Answer 48

Assume at least 20 min.