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Dec 23, 20231 min read
What is a Variable Star?
A variable star's apparent brightness changes over time as seen from Earth. There are 2 basic types: intrinsic variables whose luminosity...
Nov 10, 20231 min read
What is a Cepheid variable?
A Cepheid variable is a variable star that pulsates radially, varying in both diameter and temperature causing changes in brightness with...
Oct 13, 20231 min read
Ptolemy's original 48 constellations
The Greco-Roman Ptolemy listed 48 constellations after 150 AD. These were: Andromeda Ara Aries Aquarius Aquila Argo Auriga Boötes Cancer...
Oct 6, 20231 min read
What is a star?
A star is a luminous ball of gas (mostly hydrogen and helium) held together by its own gravity. Nuclear fusion reactions at its core...
Sep 28, 20234 min read
How are stars classified and what are stellar spectra?
Stellar classification is usually based on two classification schemes, based on the star's surface temperature (the Harvard system), and...
Sep 16, 20231 min read
Does the North Star Change?
Yes due to precession. About 12,000 BC Vega was the North Star, lying approximately at the north celestial pole, not Polaris, and in...
Jul 24, 20231 min read
What Is An Asterism?
An asterism is a small pattern or collection of stars that are not constellations, although they are often parts of a constellation: eg....
Jul 17, 20231 min read
Modern Constellations
The sky is divided into 88 sections, known as constellations, which astronomers use to locate and name celestial objects. Most of the...
Jul 7, 20231 min read
What Makes 'The Summer Triangle' ?
This is outlined by three stars: Vega, Deneb & Altair. The asterism 'The Northern Cross' (in the constellation Cygnus) is often used to...
May 19, 20231 min read
Star brightness
The brightness of stars appears to be different, because they give out different amounts of light and they lie at vastly different...
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