Editing Cataclysmic variable star (section)

==Discovery==

Cataclysmic variables are among the classes of astronomical objects most commonly found by amateurs, since a cataclysmic variable in its outburst phase is bright enough to be detectable with very modest instruments, and the only celestial objects easily confused with them are bright [[asteroids]] whose movement from night to night is clear.

Verifying that an object is a cataclysmic variable is also fairly straightforward: they are usually quite blue objects, they exhibit rapid and strong variability, and they tend to have peculiar [[emission line]]s. They emit in the [[ultraviolet]] and [[X-ray]] ranges; they are expected also to emit gamma rays, from annihilation of positrons from proton-rich nuclei produced in the fusion explosion, but this has not yet been detected.<ref>{{cite journal|first1=F|last1=Senziani|first2=G.K.|last2=Skinner|first3=P.|last3=Jean|first4=M.|last4=Hernanz|title=Detectability of gamma-ray emission from classical novae with Swift/BAT|date=2008|doi=10.1051/0004-6361:200809863|journal=[[Astronomy and Astrophysics]]|volume=485|issue=1|pages=223–231|arxiv=0804.4791|bibcode=2008A&A...485..223S|s2cid=16650963}}</ref>

Around six [[Galactic astronomy|galactic]] novae (i.e. in [[Milky Way|our own galaxy]]) are discovered each year, whilst models based on observations in other galaxies suggest that the rate of occurrence ought to be between 20 and 50;<ref>{{cite journal|first1=M. J.|last1=Darnley|first2=M. F.|last2=Bode|first3=E.|last3=Kerins|first4=A. M.|last4=Newsam|first5=J.|last5=An|first6=P.|last6=Baillon|first7=V.|last7=Belokurov|first8=S.|last8=Calchi Novati|first9=B. J.|last9=Carr | first10 = M. | last10 = Creze|first11=N. W.|last11=Evans|first12=Y.|last12=Giraud-Heraud|first13=A.|last13=Gould|first14=P.|last14=Hewett|first15=Ph.|last15=Jetzer|first16=J.|last16=Kaplan|first17=S.|last17=Paulin-Henriksson|first18=S. J.|last18=Smartt|first19=Y.|last19=Tsapras | first20 = M. | last20 = Weston|title=Classical novae from the POINT-AGAPE microlensing survey of M31 -- II. Rate and statistical characteristics of the nova population|year=2006|doi=10.1111/j.1365-2966.2006.10297.x|journal=[[Monthly Notices of the Royal Astronomical Society]]|volume=369|issue=1|pages=257–271|doi-access=free |arxiv=astro-ph/0509493|bibcode=2006MNRAS.369..257D|s2cid=85510790}}</ref> this discrepancy is due partly to obscuration by interstellar dust, and partly to a lack of observers in the southern hemisphere and to the difficulties of observing while the Sun is up and at [[full moon]].