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Quiz about An Astronomers Lexicon
Quiz about An Astronomers Lexicon

An Astronomer's Lexicon Trivia Quiz

Astronomical Terminology

We often hear astronomical terms bandied about, but which of these do we really understand on a technical level? Match these ten terms with their proper definitions.

A matching quiz by trident. Estimated time: 3 mins.
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Author
trident
Time
3 mins
Type
Match Quiz
Quiz #
418,741
Updated
Jan 04 25
# Qns
10
Difficulty
Very Easy
Avg Score
9 / 10
Plays
173
Last 3 plays: joecali (5/10), mfc (10/10), griller (10/10).
(a) Drag-and-drop from the right to the left, or (b) click on a right side answer box and then on a left side box to move it.
QuestionsChoices
1. The point in a planet's orbit where it is closest to the Sun  
  perihelion
2. An energetic galactic core powered by a supermassive black hole  
  pulsar
3. The partially shaded outer region of a shadow cast by a solid object  
  quasar
4. A unit of distance equal to about 3.26 light-years  
  parsec
5. The time when day and night are nearly equal  
  apogee
6. A rotating neutron star emitting beams of radiation in pulses  
  corona
7. The point in an orbit where an object is farthest from Earth  
  retrograde
8. The apparent motion of a planet moving backward in the sky  
  accretion
9. The outermost layer of a star's atmosphere  
  penumbra
10. The process where matter accumulates due to gravity  
  equinox





Select each answer

1. The point in a planet's orbit where it is closest to the Sun
2. An energetic galactic core powered by a supermassive black hole
3. The partially shaded outer region of a shadow cast by a solid object
4. A unit of distance equal to about 3.26 light-years
5. The time when day and night are nearly equal
6. A rotating neutron star emitting beams of radiation in pulses
7. The point in an orbit where an object is farthest from Earth
8. The apparent motion of a planet moving backward in the sky
9. The outermost layer of a star's atmosphere
10. The process where matter accumulates due to gravity

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Quiz Answer Key and Fun Facts
1. The point in a planet's orbit where it is closest to the Sun

Answer: perihelion

Perihelion is the point in the orbit of a planet or other celestial body where it is closest to the Sun. Since orbits are typically elliptical rather than perfectly circular, the distance between a planet and the Sun changes as the planet moves along its orbit.

At perihelion, the gravitational pull of the Sun is strongest, which causes the planet to travel faster compared to other parts of its orbit. Earth's perihelion occurs in early January, when it is about 147 million kilometers from the Sun, while its farthest point, called aphelion, happens in early July.
2. An energetic galactic core powered by a supermassive black hole

Answer: quasar

A quasar is a highly energetic and distant object in the universe that looks like a bright star when viewed through a telescope. However, unlike stars, quasars are powered by supermassive black holes at the centers of galaxies. As matter falls toward the black hole, it heats up and emits enormous amounts of light and other energy, making quasars some of the brightest objects in the universe.

Despite their intense brightness, quasars are usually billions of light-years away.
3. The partially shaded outer region of a shadow cast by a solid object

Answer: penumbra

The term "penumbra" refers to the outer part of a shadow where only part of the light source is blocked. It occurs when an object partially obstructs a light source, creating a region of partial shadow. Penumbras are commonly observed during eclipses.

For example, during a lunar eclipse, the Moon passes through Earth's penumbra before or after entering the darker, central part of the shadow called the umbra. In the penumbra, the light from the Sun is only partially blocked, resulting in a faint or partial dimming rather than complete darkness.
4. A unit of distance equal to about 3.26 light-years

Answer: parsec

A parsec is a unit of distance used in astronomy to measure large distances beyond our solar system. It stands for "parallax of one arcsecond" and is defined (in complex terms) as the distance at which an object would have a parallax angle of one arcsecond when viewed from opposite sides of Earth's orbit around the Sun. One parsec is roughly equal to 3.26 light-years, or about 31 trillion kilometers. Astronomers use parsecs because measuring the apparent shift (or parallax) of nearby stars helps determine their distance from Earth.
5. The time when day and night are nearly equal

Answer: equinox

An equinox is the moment when the Sun appears directly above Earth's equator, resulting in nearly equal lengths of day and night across the planet. This happens twice a year, around March 21 (the vernal or spring equinox) and September 23 (the autumnal or fall equinox). Equinoxes occur because of Earth's axial tilt, which causes different parts of the planet to receive varying amounts of sunlight throughout the year.

However, during an equinox, Earth's axis is neither tilted toward nor away from the Sun, so sunlight is distributed more evenly.
6. A rotating neutron star emitting beams of radiation in pulses

Answer: pulsar

A pulsar is a highly magnetized, rapidly spinning neutron star that emits intense beams of electromagnetic radiation from its magnetic poles. These beams are so regular that they seem to pulse as the star rotates, similar to a lighthouse beam sweeping across the ocean. Pulsars are formed when massive stars explode in supernovae, leaving behind a dense core that continues to spin very quickly.

Some pulsars rotate hundreds of times per second.
7. The point in an orbit where an object is farthest from Earth

Answer: apogee

Apogee is the point in the orbit of an object, such as a communications satellite or the Moon, where it is farthest from Earth. As most orbits are elliptical, the distance between the orbiting object and Earth changes as it travels around the planet. Apogee represents the maximum distance, while the closest point is called perigee. Objects at apogee move more slowly due to weaker gravitational pull compared to when they are closer to Earth. Concerning communications and navigational satellites orbiting Earth, this could lead to a weaker signal due to the longer distance or less reliable coverage due to the slower speed.
8. The apparent motion of a planet moving backward in the sky

Answer: retrograde

Retrograde motion refers to the apparent backward motion of a celestial object, such as a planet, as observed from Earth. This occurs because planets move at different speeds in their orbits around the Sun. When Earth overtakes a slower-moving outer planet, like Mars, that planet appears to move backward in the sky for a short period before resuming its normal forward motion.

This phenomenon is called apparent retrograde motion, as the planet isn't actually reversing its orbit. Johannes Kepler was the scientist who best explained retrograde motion with the heliocentric model by showing that planets travel in elliptical orbits.
9. The outermost layer of a star's atmosphere

Answer: corona

The term "corona" refers to the outermost part of a star's atmosphere, consisting of extremely hot, ionized gas called plasma. It extends far beyond the star's surface and is much hotter than the star's visible layers. The corona's extreme heat, which is millions of degrees hotter than the star's surface (photosphere), is counterintuitive because you would expect temperature to decrease as you move farther from the star's core, where nuclear fusion occurs.

However, the corona is hotter due to intense magnetic activity.
10. The process where matter accumulates due to gravity

Answer: accretion

Accretion is the process where matter collects and grows due to gravity. In space, this happens around massive objects like stars, black holes, or young stars. As gas and dust are pulled inward by gravity, they form a spinning disk called an accretion disk.

The material in the disk moves toward the center, heats up because of friction, and gives off energy as light and radiation. Accretion disks are often found around black holes, where the strong gravity makes them very hot and bright.
Source: Author trident

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