colloquially known as the Little Dipper because its seven brightest
stars appear to form the shape of a ladle (diagram pictured). It was one
of the 48 constellations listed by the 2nd-century astronomer Ptolemy,
and it remains one of the 88 modern constellations. Polaris, its
brightest star, is currently less than one degree away from the north
celestial pole. Because this position stays nearly fixed as the Earth
rotates, the star has traditionally been important for navigation,
particularly by mariners. Polaris is a yellow-white supergiant and the
brightest Cepheid variable star in the night sky, ranging in apparent
magnitude from 1.97 to 2.00. Beta Ursae Minoris, also known as Kochab,
is an aging star that has swollen and cooled to become an orange giant
with an apparent magnitude of 2.08, only slightly fainter than Polaris.
The constellation also contains an isolated neutron star—Calvera—and
H1504+65, the hottest white dwarf yet discovered, with a surface
temperature of 200,000 degrees Kelvin. Planets have been detected
orbiting four of the constellation's stars, including Kochab.
Read more: <https://en.wikipedia.org/wiki/Ursa_Minor>
_______________________________
Today's selected anniversaries:
9:
The Western Han dynasty of China ended after the throne was
usurped by Wang Mang, who founded the Xin Dynasty.
<https://en.wikipedia.org/wiki/Han_dynasty>
236:
Pope Fabian, who is said to have been chosen by the Holy Spirit
by having a dove land on his head, began his papacy.
<https://en.wikipedia.org/wiki/Pope_Fabian>
1645:
William Laud, Archbishop of Canterbury and a fervent supporter
of King Charles I, was beheaded in the midst of the English Civil War.
<https://en.wikipedia.org/wiki/William_Laud>
1901:
The first great gusher of the Texas Oil Boom was discovered in
the Spindletop oil field near Beaumont, Texas, US.
<https://en.wikipedia.org/wiki/Spindletop>
1941:
Greco-Italian War: The Greek army captured the strategically
important Klisura Pass in Albania.
<https://en.wikipedia.org/wiki/Capture_of_Klisura_Pass>
1993:
The Braer Storm, the strongest extratropical cyclone ever
recorded in the North Atlantic, reached its peak intensity.
<https://en.wikipedia.org/wiki/Braer_Storm_of_January_1993>
_____________________________
Wiktionary's word of the day:
constraint:
1. Something that constrains; a restriction.
2. (mathematics) A condition that a solution to an optimization problem
must satisfy.
<https://en.wiktionary.org/wiki/constraint>
___________________________
Wikiquote quote of the day:
No obstacle has been so constant, or so difficult to overcome, as
uncertainty and confusion touching the nature of true liberty. If
hostile interests have wrought much injury, false ideas have wrought
still more; and its advance is recorded in the increase of knowledge, as
much as in the improvement of laws.
--John Dalberg-Acton, 1st Baron Acton
<https://en.wikiquote.org/wiki/John_Dalberg-Acton,_1st_Baron_Acton>
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