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Stars, Galaxies & Exoplanets

149 cards · 🇺🇸 English

Star classification and evolution, galaxies and planets beyond our solar system.

astronomystarsgalaxiesexoplanets

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1Star
A luminous spheroid of plasma held together by self-gravity
2Nearest star to Earth
The Sun
3How many stars are estimated in the observable universe?
10²² to 10²⁴ stars
4How many stars are visible to the naked eye?
Only about 4,000 stars, all within the Milky Way galaxy
5How does a star's life begin?
With the gravitational collapse of a gaseous nebula of material largely comprising hydrogen, helium, and traces of heavier elements
6What determines a star's evolution and eventual fate?
Its total mass
7Why does a star shine during most of its active life?
Due to the thermonuclear fusion of hydrogen into helium in its core
8What happens at the end of a star's lifetime?
Fusion ceases and its core becomes a stellar remnant: a white dwarf, neutron star, or (if sufficiently massive) a black hole
9What creates almost all naturally occurring chemical elements heavier than lithium?
Stellar nucleosynthesis in stars or their remnants
10How are elements recycled into new stars?
Through stellar mass loss or supernova explosions that return chemically enriched material to the interstellar medium
11What stellar properties can astronomers determine?
Mass, age, metallicity, variability, distance, and motion through space by observing brightness, spectrum, and positional changes
12Etymology of the word 'star'
From Proto-Indo-European *h₂stḗr, analyzable as *h₂eh₁s- 'to burn' plus *-tēr (agentive suffix)
13Cognates of 'star' in other languages
Latin stella, Greek aster, German Stern; English cognates include asterisk, asteroid, astral, and constellation
14What distinction did early astronomers recognize?
Between 'fixed stars' (whose position on the celestial sphere doesn't change) and 'wandering stars' (planets)
15How many stars did Hipparchus's star catalogue include?
1,020 stars in the 2nd century BC, used to assemble Ptolemy's star catalogue
16Hipparchus known for discovering
The first recorded nova (new star)
17First observed and recorded supernova
SN 185, observed by Chinese astronomers in 185 AD
18Brightest stellar event in recorded history
The SN 1006 supernova, observed in 1006 by Ali ibn Ridwan and several Chinese astronomers
19What supernova gave birth to the Crab Nebula?
SN 1054, observed by Chinese and Islamic astronomers
20Book of Fixed Stars
A work written in 964 by Persian astronomer Abd al-Rahman al-Sufi, observing stars, clusters, and galaxies including the Andromeda Galaxy
21What did William Herschel discover about binary stars?
That some stars do not merely lie along the same line of sight, but are physical companions that form binary star systems
22Bayer designation
A system created by Johann Bayer around 1600, applying Greek letters to stars in each constellation
23Flamsteed designation
A numbering system based on a star's right ascension, added to John Flamsteed's star catalogue in 1712
24What authority names celestial bodies?
The International Astronomical Union (IAU)
25What does the IAU's Working Group on Star Names do?
Catalogs and standardizes proper names for stars
26Nominal solar mass parameter defined by the IAU
GM☉ = 1.3271244×10²⁰ m³/s², combining the Newtonian constant of gravitation and solar mass
27Approximate solar mass
Approximately 1.9885×10³⁰ kg
28Astronomical unit
Approximately the mean distance between Earth and the Sun, defined as exactly 149,597,870,700 m
29Where do stars condense from?
Regions of space of higher matter density called molecular clouds, consisting mostly of hydrogen (70-72%) with about 23-28% helium
30Example of a star-forming region
The Orion Nebula