diminishes in size and brightness and eventually becomes lost
to sight.

A record has been kept of about twenty temporary stars that have been
observed at various periods since the time that reliable data of those
objects have been published. Pliny mentions the appearance of a new star
in the time of Hipparchus (134 B.C.); it was seen in the constellation
of the Scorpion, and it is said that it was the apparition of this star
which induced the celebrated astronomer to construct what is known as
the earliest star catalogue. A new star is said to have become visible
when the Emperor Honorius ruled, and another during the reign of the
Emperor Otho, about 945 A.D. In May 1012 a new star appeared in Aries,
and in July 1203 another was observed in Scorpio, which resembled
Saturn. The most remarkable star of this kind was one observed by Tycho
Brahe, which appeared in the constellation Cassiopeia. He first
perceived it on November 11, 1572. In lustre it equalled Jupiter, and
when at its brightest rivalled Venus; it was visible at noonday, and at
night its light could be perceived through strata of cloud which
rendered all other stars invisible. The star maintained its brilliancy
for three weeks, when it became of a yellowish colour and perceptibly
decreased in size; it afterwards assumed a ruddy hue resembling
Aldebaran, and, diminishing gradually in magnitude and brightness,
ceased to be visible in March 1574. It twinkled more than the other
stars, and during the time it could be perceived its position remained
unchanged. In 1604 a conspicuous new star burst forth in Ophiuchus. It
surpassed in brilliancy stars of the first magnitude, and outshone the
planet Jupiter, which was in its proximity. Kepler observed this star,
and described it as 'sparkling like a diamond with prismatic tints.' It
soon began to decline after its appearance; in March 1605 it had shrunk
to the dimensions of a third-magnitude star, and in a year later it
became entirely lost to view. Other stars of the same class, though of a
less conspicuous character, have been observed at occasional times.
Anthelme, a Carthusian monk, discovered one near Beta Cygni in 1670;
another appeared in Ophiuchus in 1848; one in Scorpio in 1860; one in
Corona Borealis in 1866; in Cygnus in 1876; in Andromeda in 1885; and in
Auriga in 1892.

Various theories have been advanced in order to account for the sudden
outbursts of those stars, the light from which has probably occup