Intro to Astronomy

What is the primary goal of the astronomy course?

To preview topics covered this term and establish astronomy vocabulary for students with no prior familiarity.

Who is the author of the quote about Earth being a 'Pale Blue Dot'?

Carl Sagan

What analogy is used to describe the Solar System?

A neighborhood

What are the main components of the Solar System?

Sun, planets, moons, asteroids, meteoroids, comets, and some dust.

What is the Sun primarily composed of?

Hydrogen and Helium plasma.

How much of the Solar System's mass does the Sun comprise?

Approximately 99%.

What are the four terrestrial planets?

Mercury, Venus, Earth, and Mars.

What are the four Jovian planets?

Jupiter, Saturn, Uranus, and Neptune.

What distinguishes terrestrial planets from Jovian planets?

Terrestrial planets are rocky and closer to the Sun, while Jovian planets are gas giants and farther from the Sun.

What are 'major' moons?

Moons that are considered worlds in their own right.

What are asteroids primarily composed of?

Rock and metal, mostly found in a belt between Mars and Jupiter.

What is the difference between meteoroids, meteors, and meteorites?

Meteoroids are small rocks in space, meteors are meteoroids that burn up in the atmosphere, and meteorites are meteoroids that land on Earth.

What are comets primarily made of?

Ice and dust, often referred to as 'dirty snowballs'.

What happens to a comet's tail as it approaches the Sun?

The tail forms from vaporized ice and points away from the Sun.

Where do long-period comets originate?

From the Oort cloud.

Where do short-period comets originate?

From the Kuiper Belt.

Who discovered Pluto and when?

Clyde Tombaugh in 1930.

What was Pluto initially classified as?

The ninth planet of the Solar System.

What led to the reclassification debate of Pluto?

The discovery of Kuiper Belt Objects (KBOs) and Pluto's similarities to them.

What is the name of Pluto's largest moon?

Charon.

What was the public's reaction to the potential reclassification of Pluto?

Widespread outrage and petitions from schoolchildren to keep Pluto as a planet.

What is Eris and why is it significant?

Eris is a Kuiper Belt Object discovered in 2003, initially thought to be larger than Pluto.

What was the Titius-Bode Law?

A hypothesis that predicted the positions of planets in the Solar System, leading to the discovery of asteroids.

What is the significance of the blink comparator?

It was an invention used by Clyde Tombaugh to discover Pluto.

What is the orbital inclination of Pluto?

17 degrees, which causes it to cross Neptune's orbit.

What do astronomers consider when classifying a celestial body as a planet?

Criteria such as size, orbit, and composition.

What sparked the debate over Pluto's classification?

Astronomers considered reclassifying Pluto, leading to public outrage and petitions from schoolchildren.

What is Eris in relation to Pluto?

Eris is a Kuiper Belt Object (KBO) discovered in 2003, initially thought to be larger than Pluto but later found to be slightly smaller.

What was the central problem regarding the classification of planets?

There was no formal, agreed-upon definition for what constitutes a planet.

What criteria did the IAU initially propose for classifying a planet?

A planet must be a sphere and orbit the sun, ruling out moons and most asteroids.

What additional criterion did the IAU add to the definition of a planet?

A planet must have gravitationally 'cleared' its orbit.

What does the term 'planet' mean in ancient Greek?

'Wanderer' or 'wandering object'; historically, the sun and moon were also considered planets.

What event in 2015 reignited the debate over Pluto's status?

The New Horizons mission reached Pluto and provided the first close-up pictures.

What is an Astronomical Unit (AU)?

A unit of measurement used to describe distances in space, equivalent to the average distance from the Earth to the Sun.

How far is Pluto from the Sun in AU?

Pluto is about 40 AU from the Sun.

What is the Milky Way Galaxy?

A galaxy containing hundreds of billions of stars, including our Sun, located about 2/3 of the way out in one of its arms called the Orion Arm.

What is the approximate diameter of the Milky Way Galaxy?

The Milky Way is approximately 100,000 light-years across.

What is a light-year (ly)?

A unit of distance that light travels in one year, used for measuring astronomical distances.

What is the Local Group?

A cluster of galaxies that includes the Milky Way and about two dozen other galaxies, including the Andromeda Galaxy.

What is a supercluster in astronomy?

A large group of galaxies that cluster together, with the Local Supercluster being one example.

What was the IAU's final decision on Pluto's classification?

Pluto was reclassified as a dwarf planet due to its inability to clear its orbit.

What was the public reaction to the reclassification of Pluto?

There was widespread outrage, with many people, including schoolchildren, advocating for Pluto to remain a planet.

What is the significance of the term 'cleared its orbit' in planet classification?

It means that a planet must be gravitationally dominant in its orbital zone, which Pluto does not satisfy.

How did the IAU's definition of a planet affect the number of recognized planets?

The definition could potentially increase the number of recognized planets as more objects are discovered.

What was the outcome of the IAU committee's initial recommendations?

The IAU committee's recommendations were overridden, leading to the final definition that excluded Pluto.

What role did Henrietta Swan Leavitt and Edwin Hubble play in astronomy?

They contributed to the understanding that the Milky Way is part of a larger universe with multiple galaxies.

What is the relationship between the Milky Way and the Local Group?

The Milky Way is one of the galaxies in the Local Group, which contains about two dozen galaxies.

What is the significance of the spiral pattern in galaxies?

The spiral pattern is likely due to some kind of wave, and spiral galaxies contain a lot of dust and are relatively flat.

What is the purpose of using larger units like AU and light-years in astronomy?

Larger units help to describe vast distances in space more effectively than smaller units like miles or kilometers.

What was a concern regarding the increasing number of planets?

There was concern about how schoolchildren would memorize the names and order of the planets if the number kept increasing.

What does the term 'wandering object' refer to in ancient astronomy?

It referred to celestial bodies that moved against the backdrop of fixed stars, which included planets, the sun, and the moon.

What is the name of our supercluster of galaxies?

Laniakea, meaning 'Immense Heaven' in Hawaiian.

What significant discovery was made about the Laniakea Supercluster in 2014?

It is much larger than previously thought.

What is the distinction between the Observable Universe and the Universe?

The Observable Universe refers to what we can see from Earth, while the Universe includes everything beyond that.

What are the basic units of time derived from astronomy?

The day, the year, the month, and the week.

How long is a day based on Earth's rotation?

Roughly 24 hours.

What is a year based on?

Earth's revolution around the sun, approximately 365.25 days.

What problem arises from the 365.25 days in a year?

The calendar would go out of sync with the seasons if the extra quarter day is not accounted for.

What solution did Julius Caesar implement for the calendar?

He instituted 'Leap Day' to correct the drift of the calendar.

What reform did Pope Gregory XIII mandate for the calendar?

He fixed a 10-day error and established that century years would only be leap years if evenly divisible by 400.

What is the lunar month based on?

The cycle of the moon's phases, approximately 29.5 days.

What is a solar calendar?

A calendar that prioritizes the year based on Earth's movement around the sun.

What is a lunar calendar?

A calendar that prioritizes the moon's cycles.

Why is the week seven days long?

It corresponds to the seven naked-eye 'wanderers' or planets visible from Earth.

What are the names of the days of the week derived from Roman and Norse mythology?

Saturday (Saturn), Sunday (Sun), Monday (Moon), Tuesday (Tyr/Mars), Wednesday (Wotan/Mercury), Thursday (Thor/Jupiter), Friday (Frigga/Venus).

What was the significance of the term 'planet' in ancient astronomy?

It referred to 'wandering objects' that moved through constellations.

What is the main takeaway regarding the structure of the Universe?

The Universe has distinct levels of structure and is considered 'clumpy'.

What happens if we ignore the extra days in lunar calendars?

Some cultures may ignore them, while others may accumulate them for a 'leap month'.

What is the average number of visible stars from Earth?

About 5,000 lights in the sky.

How does the movement of the Earth-Moon system affect lunar calendars?

The Earth-Moon system's movement around the sun causes discrepancies in lunar months.

What is the historical significance of the Julian Calendar?

It was the first calendar to introduce Leap Day to correct seasonal drift.

What was the impact of the calendar reforms in the 1500s?

The Julian Calendar was corrected to align with the seasons, fixing a 10-day error.

What is the relationship between astronomical motions and calendar adjustments?

Each time unit is based on independent astronomical motions, requiring adjustments to maintain synchronization.

What is the average length of a lunar month?

Approximately 29.5 days.

What is the significance of Leap Year in the Gregorian calendar?

It corrects the drift caused by the extra quarter day in the calendar.

What does the term 'clumpy' refer to in the context of the Universe?

It describes the distinct levels of structure within the Universe.

What is the role of astronomy in defining our time units?

Astronomy provides the basis for our most fundamental units of time.