An introduction to astronomy: designed as a text-book for the use of students in college. By Denison Olmsted ...

TEMPORARlt Y AN) VARIA;A,1 STAIRS,. 29.
M:any of tlhe doul>le stars are distinguislhed by) the col tponents exhibiting' different colors, often finely conltrasted witl
catch other t; as orange with blue or green, yellow witl blue,
anld wllite ith purple. Gatmma Alndrolledt is a close ldou1ble
star, thto componelnts of whlichl are both grtcc. InlSulate stars
of a red color, almost as deep as thlat of blood, occur in many
par)ts of the heavens, but no grenit or blue star of any dlecided
hue has ever ben noticed unassociated withl a comlpanlioll
brighlter tllan itsielf.'
4 22. T'r;MtoroAl Y S'TARS..'irCM!'OlIRTY STAlS are new sta'rs which have suddenly made
tlheir appearance, and after a certain interval, as sudtdenly disaplpelarc, and returtned ro more. It was thle appealrallce of a.
new star1 of this lkind, I 5 yearls bbefore the Christian eIra, thl'at
pronmptecd I ipparchus to form a catalopgu of tlhe stars, the firzst
on recorld. Such also was the star which sdd(lenly shone out,
A. 1). 389, in thle Eaglep, as brigttt as Venlus, and after remain.trig tlhree weeks, distappeared enttirely..A.t other periods, at
distal:t iltrltts, similar. 1phlenoimena h}tave presented t helnmscilve. Thulls te applearatnce of a new star in 1672 was so stlddcii, that Tychlo Iraelttlc, returntin"' home one0Ic evening, was stilr
pr'isdlt to find a, eollection of country people op illn at a starl
whtliclt }tc was sure t didt not exist; lalf an tour11 before. It \was8
thenl as brigh(pit ns Sirius, a1d ( oultinued to increase until it surpass-ed l Jupiter wh0etn bright,1ltcst, ar-nd was visible at mid-day. In
a iontloltl it lbe<1ga1t to (limiilnish, ai(i in three lmonths afterward
it, tladi entiicly disappeatred. Some stars are iow miissin w\liclh
were regtyistered in the older cataloguest. In one instance, at
least (tlhat of N'eptune), the supposed star ]has proved to have
been a planet.
423. VYARIAf,E: S'TAlS.'tix'.Ar~. S:u^l~s are those wllicht underfgo a )criodieal chlange
of bri;ghltness. Oi(e of the most remarkable is tIle star' /a, ill
tlle neck of the Wh\ale (Om'nictoOt- Ceit). It app)ears olce inl 11
montllls, rtmains at its greatest brigltlness (about a fortnight,
beinl'g tlholl on some occasiolls, equal to a star of thie second
"'riericIle.