Midterm Crossword Concepts — Astronomy
Timekeeping, orbits, and angular measures
Solar day (24 hours): The day is 24 hours long; defined as the time for the Sun to return to the same meridian. Represented as . Note the difference from a sidereal day (the rotation period relative to the fixed stars), which is about .
Meridional alignment during lunar phases: Waxing phases show the illuminated portion on the right (as seen from the Northern Hemisphere, e.g., Fort Collins). This corresponds to the Moon bright on the right as it moves from New toward Full.
Angular size and the “degree”: The width of a pinky at arm’s length is roughly . Degrees are the basic angular units used to measure positions and apparent sizes in the sky.
Moon phases and key terms
Waxing: The illuminated portion of the Moon is increasing.
Waning: The illuminated portion of the Moon is decreasing.
Full Moon: The Moon is opposite the Sun in the sky; the full Moon is on the local meridian at or around midnight.
New Moon: The near side of the Moon is dark; the far side is fully lit. This is the phase when the Moon lies roughly between the Earth and Sun.
Perigee and Apogee (relevant during eclipses):
Apogee = point in the Moon’s orbit farthest from Earth; during an annular solar eclipse, the Moon is near apogee and too distant to fully cover the Sun.
Perigee = point in the Moon’s orbit closest to Earth; more commonly associated with total eclipses when the Moon appears larger than the Sun.
6) Full Moon on the meridian at midnight: The Full Moon is typically highest in the sky around local midnight (a practical rule of thumb for observer planning).
12) Apogee: The Moon is near this point during an annular solar eclipse.
13) Partial lunar/solar eclipse terminology: When observers are in the Moon’s penumbra, the solar eclipse seen is Partial (only part of the Sun is obscured).
Celestial coordinates, direction, and navigation
Altitude and latitude: The altitude of Polaris (the North Star) above the horizon approximately equals the observer’s latitude in the Northern Hemisphere. So, for an observer at latitude , the altitude of Polaris is ≈ degrees above the northern horizon.
Zenith: The point directly overhead (90° above the observer’s position).
Azimuth: An angular coordinate that tells the cardinal direction of a star or object, usually measured from due north along the horizon toward the east. Represented as ; common convention places 0° at due north, increasing eastward.
15) Azimuth: The angular coordinate giving the cardinal direction of a star.
The Sun, stars, and the zodiac
Zodiac: The Sun “lives in” 13 constellations along the ecliptic; these are the zodiac constellations (the traditional twelve plus Ophiuchus in some accounts).
17) The Sun lives in these 13 constellations: Zodiac.
18) Lunar phase with far side fully bright: New Moon (the far side of the Moon is illuminated while the near side is dark).
9) Zenith: The point directly overhead of an observer.
7) Asterism: Any recognizable pattern of stars within a larger constellation (e.g., the Big Dipper is an asterism within Ursa Major).
Solar system, historical astronomy, and planetary references
10) Uranus: Historically not recognized by ancient observers as a planet because it moves very slowly along the ecliptic relative to the fixed stars.
11) Zero longitude reference: The Prime Meridian is the zero-point of longitude, defined by the Greenwich Observatory in England.
14) The month corresponding to the Moon’s orbital period: Sidereal month (the time for the Moon to complete one orbit relative to the background stars).
16) A modern planet without a weekday named after it: Earth (weekdays derive from Sun, Moon, and the classical planets; Earth itself does not have a weekday named after it).
19) 48 ancient constellations and the Almagest: Ptolemy is the author/compiler of the Almagest, which catalogs a large set of constellations and celestial coordinates.
21) Conjunction: The configuration when the Sun, Moon, and Earth align, as in a solar eclipse where the Sun and Moon are in conjunction along the line of sight.
20) Reflecting telescope: A telescope that uses a mirror to gather and focus light (as opposed to a refractor that uses lenses).
1) Solar: A solar day is the 24-hour day used in civil time; contrasts with sidereal time and orbital mechanics.
2) Waxing: The Moon’s illuminated portion grows during waxing phases, with right-hand illumination in the Northern Hemisphere.
3) Polaris: The North Star; its altitude gives the observer’s latitude in the Northern Hemisphere.
4) Solstice: The solstices mark the extremes of the Sun’s declination, the first day of summer and winter.
5) Degree: A unit of angular measure; 1 degree corresponds approximately to the width of a finger at arm’s length.
6) Full: The Full Moon; the phase where the Moon is fully illuminated and typically highest around midnight.
8) Waning: The Moon’s illuminated portion decreases after a Full Moon.
9) Zenith: The point directly overhead.
12) Apogee: The farthest point in the Moon’s orbit around Earth; relevant to eclipse types.
13) Partial: A partial eclipse is observed when only part of the Sun (or Moon) is obscured due to the geometry of the shadow (penumbra).
15) Azimuth: The direction angle along the horizon relative to due north.
17) Zodiac: The belt of constellations around the ecliptic; the Sun traverses these over a year.
18) New: The lunar phase where the far side is fully illuminated and the near side is dark.
19) Ptolemy: The ancient astronomer who documented 48 constellations and numerous celestial relations in the Almagest.
20) Reflecting telescope: A telescope using mirrors to gather light; important in modern astronomy.
21) Conjunction: Sun–Moon–Earth alignment during a solar eclipse.
Quick reference: crossword-style answers (mapped from transcript)
1: Solar day → "Solar" (Solar day; 24 h length)
2: Waxing (Moon brighter on the right in NH during Waxing phases)
3: Polaris (Altitude equals latitude)
4: Solstice (First day of summer or winter)
5: Degree (Angular size; pinky width ≈ 1°)
6: Full (Lunar phase on the meridian at midnight)
7: Asterism (Pattern in the sky)
8: Waning (Illuminated portion shrinking)
9: Zenith (Point directly overhead)
10: Uranus (Slow-moving planet not recognized by ancient Greeks)
11: Prime Meridian / Greenwich (Zero longitude)
12: Apogee (Moon near apogee during annular eclipse)
13: Partial (Type of solar eclipse seen in Moon’s penumbra)
14: Sidereal month (Moon’s orbital period relative to stars)
15: Azimuth (Compass direction angle)
16: Earth (Planet with no weekday name)
17: Zodiac (Sun’s constellations along the ecliptic)
18: New (Far side of Moon fully lit)
19: Ptolemy (Almagest author)
20: Reflecting (Telescope type using mirrors)
21: Conjunction (Sun–Moon–Earth alignment during solar eclipse)