Vocabulary - Properties Of Stars
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Vocabulary
STUDENT RESOURCE 7.1
INFORMATION SHEET
absolute magnitude the actual
Kelvin a temperature scale that begins at
brightness of a star
the coldest possible temperature, which
A very bright star that is far from
is absolute zero, or 0 K
Earth may appear dimmer than a
Scientists use the Kelvin scale for
less bright star that is closer to Earth.
describing extreme temperatures, such
Absolute magnitude describes how
as the temperatures of stars. On the
bright a star would be if all stars were
Kelvin scale, 0 K equals –273°C. The
the same distance from Earth.
degree symbol is not used with the
Kelvin scale.
apparent magnitude the brightness of a
star as viewed from Earth
light-year the distance light travels in
Apparent magnitude describes how
one year, or 9.5 trillion km (5.9 trillion
bright a star is in Earth’s night sky. The
miles)
brightest stars have the lowest numbers,
Light travels at a speed of 300,000
including negative numbers. A star with
km/s (186,000 mi/s). The distance to the
an apparent magnitude of 2 appears
next closest star, Centauri Proxima, is
dimmer than a star with an apparent
4.2 light-years. That means it takes
magnitude of 1. A star with an apparent
4.2 years for light from that star to
magnitude of –0.8 is brighter than one
reach Earth. For comparison, it takes
with an apparent magnitude of 0. The
8.5 minutes for light from the Sun to
Sun’s apparent magnitude is –26.5.
reach Earth. One light-year is equal to
about 9.5 trillion km, or 63,000 AU.
EXPLORING SPACE • SECTION 7 PROPERTIES OF STARS •
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