Astronomy Unit 1

What is the meaning of the term 'astronomy'?

It comes from the Greek words 'astron' meaning 'star' and '-nomy' meaning 'law', hence it literally means 'law of the stars'.

What did prehistoric cultures contribute to astronomy?

They left behind astronomical artifacts such as Egyptian monuments and Stonehenge, and made methodical observations of the night sky.

What major invention was crucial for the development of modern astronomy?

The invention of the telescope.

Define observational astronomy.

Observational astronomy is focused on acquiring data from observations of celestial objects, which is analyzed using basic principles of physics.

How is theoretical astronomy different from observational astronomy?

Theoretical astronomy develops computer or analytical models to explain astronomical objects and phenomena.

What are the two branches of professional astronomy introduced in the 20th century?

Observational branches and theoretical branches.

How do theoretical and observational astronomy complement each other?

Theoretical astronomy seeks to explain observational results, and observations are used to test theoretical models.

What does the word 'astrology' mean in Greek?

Astrology comes from 'astron' meaning 'star' and '-logy' meaning 'to study', literally meaning 'to study the stars'.

What are constellations?

Constellations are patterns of stars that ancient cultures used to represent mythological figures.

What is a celestial map?

A representation of the stars and other celestial objects in the sky, often used in navigation and astronomy.

What causes stars to twinkle?

Starlight passes through air pockets of different density and humidity, which act like lenses focusing images of stars, causing them to twinkle.

What is the average angular resolution for a human with no vision problems?

About 1 arcminute, which is 1/60 of a degree.

What are the north and south celestial poles?

The north celestial pole is directly above Earth's North Pole, while the south celestial pole is above Earth's South Pole.

What is the celestial equator?

The celestial equator is the projection of Earth's equator onto the sky.

What is precession?

Precession is the wobbling of Earth's axis of rotation around the vertical, which takes about 26,000 years.

Why do seasons occur?

Seasons occur due to Earth's axial tilt of 23.5°, which affects how sunlight is distributed on Earth's surface.

What is a solar eclipse?

A solar eclipse occurs when the Moon passes between Earth and the Sun, blocking sunlight.

What is a lunar eclipse?

A lunar eclipse occurs when the Earth passes between the Sun and the Moon, causing Earth's shadow to fall on the Moon.

What phases can a lunar eclipse take?

Lunar eclipses can be penumbral, partial, or total.

What is the difference between a solar eclipse and a lunar eclipse regarding timing?

A solar eclipse happens at new moon, while a lunar eclipse happens at full moon.

What causes the tides?

Tides are caused by the gravitational forces exerted by the Moon and the Sun, combined with Earth's rotation.

What are spring and neap tides?

Spring tides occur near full and new moons when the gravitational forces combine, while neap tides occur near the first and third quarters when the forces are at right angles.

Why don't we have a solar eclipse at every new moon?

The Moon's orbit is tilted about 5.15° to the plane of Earth's orbit, so new moons do not always align perfectly with the Sun.

Why do we see only one side of the Moon from Earth?

Because of synchronous rotation; the Moon rotates once on its axis for every orbit around Earth.

What is the Saros cycle?

The Saros cycle is approximately an 18-year, 11 1/3-day cycle over which the pattern of eclipses repeats.

What is the significance of the ecliptic?

The ecliptic is the apparent path of the Sun across the celestial sphere, marking the zodiac constellations.

How does axial tilt affect the seasons?

The axial tilt causes the Sun's rays to hit different regions of Earth at various angles throughout the year, leading to seasonal variations.

What is the phase of the Moon during a solar eclipse?

The phase is New Moon.

What is the phase of the Moon during a lunar eclipse?

The phase is Full Moon.

What is the celestial sphere?

The celestial sphere is an imaginary sphere surrounding Earth onto which all celestial bodies can be projected.

What is the 'zenith' in astronomy?

The zenith is the point in the sky directly above an observer.

What are the primary colors scattered by Earth's atmosphere?

Nitrogen and oxygen molecules scatter blue and violet light more effectively than other colors, which makes the sky appear blue.

What is the role of the lunar nodes in eclipses?

Eclipses can only occur when the Moon is near a node, where its orbit crosses the ecliptic plane.

How can eclipses be predicted?

Eclipses can be predicted using the Saros cycle, which accounts for patterns in the positions of the Earth, Moon, and Sun.

Define 'solar atmosphere' in the context of a solar eclipse.

The solar atmosphere is revealed during a total solar eclipse, showing the Sun's corona and other layers not normally visible.

What is the 'diamond ring effect'?

A phenomenon seen during a total solar eclipse when the sunlight shines through the valleys along the Moon's silhouette.

List the three types of solar eclipses.

Total solar eclipse, partial solar eclipse, and annular solar eclipse.

Describe a penumbral lunar eclipse.

A penumbral lunar eclipse occurs when the Moon passes through Earth's penumbral shadow, leading to a subtle shading on the Moon's surface.

What causes a 'blood moon' during a lunar eclipse?

A blood moon occurs due to Earth's atmosphere scattering blue light, causing the Moon to take on a reddish hue.

What is the average distance Earth is from the Sun?

Approximately 1 astronomical unit (AU), which is about 150 million kilometers.

Why are the Moon's phases a consequence of its orbit?

Different portions of the Moon’s surface are illuminated by the Sun as it orbits Earth, leading to the observable phases.