General astronomical terms Flashcards
(27 cards)
What is synoptic?
describes observations that give a broad view of a subject at a particular time
What is an asteroid ?
a rock in orbit, generally between Mars and Jupiter; fragments of a planet that never came together. Over the eons, because of collisions and gravitational jostling with neighbors, some asteroids have been ejected from the main belt and some are on trajectories that intersect with Earth’s orbit.
What is a comet ?
a chunk of ice and rock originating from the outer solar system. Some of them occasionally get gravitationally nudged so that they zoom toward the inner solar system, with the possibility of hitting Earth.
What is a meteor ?
the streak of light seen when a space rock — an asteroid or a comet — enters the atmosphere and starts burning up. It’s the scientific synonym for “falling star.”
What is a meteorite ?
If a meteor doesn’t entirely burn up, and crashes on Earth, a piece of space debris that lands on Earth is called a meteorite.
What is a meteoroid ?
Space rock that hasn’t impacted on Earth yet. (After it impacts, the result is called a meteorite.)
Size wise: bigger than a dust grain but smaller than an asteroid. The dividing line between asteroid and meteoroid is fuzzy, but generally, space rocks bigger than boulders are called asteroids. So a breadbox-size rock would be a meteoroid.
What is a bolide ?
A bolide is either an extraterrestrial body that collides with the Earth, or an exceptionally bright, fireball-like meteor regardless of whether it ultimately impacts the surface. A stronomers use the term to describe a bright fireball from an incoming meteor; geologists use it as a catch-all term for a comet or an asteroid that hits the Earth.
What is a blazar ?
A beamed active galactic nucleus (AGN), where we are looking into the relativistic jet; an AGN whose observed radiation is dominated by a relativistic jet pointing at us
What is an active galaxy?
A galaxy with an unusually luminous nucleus.
Seyfert and N galaxies, and also quasars, are examples (but there are others).
Often referred to as active galactic nuclei (AGNs) bc energy comes from the nucleus.
What are the celestial poles?
The points where Earth’s axis intersect the (fictious) celestial sphere. They are directly above the north and south poles.
What is the celestial equator ?
Midway between the north and south celestial poles, representing the intersection of Earth’s equatorial plane with the celestial sphere.
How many arc minutes are there in 1°?
60 arc minutes. Or in other words, 1/60 of a degree. The symbol is the single quote: 60’. The term arc is used to distinguish this angular unit from the unit of time.
What are arc seconds ?
Divisions of a minute: 60 arc seconds in an arc minute. 60”. Since an arc minute is 1/60 of a degree, an arc second is 1/3600 of a degree.
What is a sidereal day ?
A day measured by the stars, by which mean mean the time between a star reaching its zenith one night and reaching its next zenith the next night. Approx. 23 hrs 56 min 4 sec. The sidereal day is Earth’s true rotation period.
What is a solar day ?
The time from one noon to the next.
What is astrometric variability ?
Variability in position or motion as observed. Objects in our solar system display motions, while stars display parallax as well as proper motion changes.
aphelion
Farthest position of a planet from the Sun.
perihelion
Closest position of a planet from the Sun .
apogee
The position of the Moon farthest from Earth .
perigee
The position of the Moon closest from Earth.
elongation
the angle between the Sun and a planet as seen from Earth
opposition
position in the orbit of a planet when opposites the Sun as seen from Earth
conjunction
position in the orbit of a planet when appears closer to the Sun as seen from Earth .
occultation
When one object is hidden by another object that passes between it and the observer. Most often used to describe when the Moon occults or eclipses a planet or a star, but occultations can also happen when (eg) an asteroid passes in front of a star.
