Intro to Astronomy and Scale
What is astronomy?
The scientific study of objects and phenomena beyond Earth's atmosphere
What is Earth's rotation?
The cause of day and night on Earth
What is the Nebular Hypothesis?
The hypothesis that explains how the solar system formed about 4.6 billion years ago from a collapsing cloud of gas and dust
What is a spiral galaxy?
The galaxy type characterized by a flat disk, spiral arms, and active star formation, like our own Milky Way
What is the event horizon?
The boundary of a black hole beyond which nothing, not even light, can escape
What is an Astronomical Unit (AU)?
The average Earth-to-Sun distance, equal to about 1.496 × 10⁸ km
What is 23.5 degrees?
The degree of Earth's axial tilt, which is the true cause of the seasons
What are Mercury, Venus, Earth, and Mars?
The four inner, rocky planets of the solar system
What is a dirty snowball?
A comet is sometimes nicknamed this because its nucleus is a porous mixture of ice and dust
What is time dilation (the clock runs slow)?
According to special relativity, this happens to time on a clock that is moving at high-speed relative to an observer
What is a light-year?
The distance light travels in one year, approximately 9.46 × 10¹² km
What is approximately June 21?
The date around which the Summer Solstice occurs in the Northern Hemisphere, marking the longest day of the year
What is Venus (hint the fun fact that was given about it)?
This planet has a runaway greenhouse effect, sulfuric acid clouds, and a surface temperature of about 465°C
What is the Kuiper Belt?
The region of the solar system that is the source of short-period comets, located beyond Neptune
What are GPS satellites?
Real-world technology that requires relativistic time corrections every day due to both special and general relativity
What is a parsec?
The professional astronomy unit equal to about 3.26 light-years, based on a one-arcsecond parallax
What is waxing?
The term for the growing phase of the Moon as it moves from New Moon toward Full Moon
What is Saturn (hint the fun fact that was given about it)?
The average density of gas giants is so low that this planet would literally float in water
What is the Chicxulub impactor?
The ~10 km impactor 66 million years ago whose crater in Mexico is linked to the mass extinction of non-avian dinosaurs
What is exotic matter?
The hypothetical material with negative energy density required to keep a traversable wormhole open
What is 30 kpc (kiloparsecs)?
The approximate diameter of the Milky Way galaxy in kiloparsecs
What is Earth's shadow falling on the Moon?
The actual cause of lunar eclipses, NOT what causes Moon phases.
What is the frost line?
The boundary in the solar system beyond which temperatures were cold enough for ices to form, allowing gas giants to rapidly capture gas and grow large
What is the DART mission?
NASA's 2022 mission that successfully proved the kinetic impactor concept for planetary defense by changing an asteroid's orbit
What are perchlorates?
The major challenge for terraforming Mars related to its soil chemistry that makes it toxic to most life