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Matthew Templeton
September 28, 2010 - 2:10pm

RR Tauri is an incredibly active young stellar object -- a star still in the process of forming.  RR Tau is an emission-line star belonging to the HAeBe class, which are stars with spectral types A or B, emission lines, and show signs of nearby nebulosity.  It is also a variable star...

Matthew Templeton
April 22, 2011 - 10:56am

RS Ophiuchi is one of the most famous of the recurrent novae, and AAVSO observers have been following this star since at least 1914.  It even got a mention in Leslie Peltier's memoir Starlight Nights (page 192 of the Harper & Row edition).  The first recorded...

Matthew Templeton
July 16, 2012 - 12:34pm

RU Herculis is another Mira with strongly varying cycle-to-cycle behavior.  It has a high amplitude, approaching nine magnitudes from peak to trough on some cycles, although six magnitudes is more typical.  As is often the case with large-amplitude stars, the light curves are...

Matthew Templeton
February 7, 2011 - 9:40am

RU Lupi is one of many T Tauri variables under observation by the amateur community.  These stars are young objects, still accreting matter from the dust and gas clouds from which they form.  In this case, RU Lup sits in the midst of a large dust cloud clearly visible against the...

Matthew Templeton
November 18, 2010 - 8:46am

RX Andromedae is an excellent example of the Z Camelopardalis class of dwarf novae, aka the "Z Cam stars".  These stars are like other dwarf novae in that they undergo outbursts of several magnitudes, lasting for days to a few weeks, caused by their disks rapidly increasing in...

Matthew Templeton
February 7, 2011 - 10:06am

RX Pup is a symbiotic star -- a binary star system composed of a giant star and a small companion onto which wind from the giant star accretes.  Their spectra are composite spectra, showing features typical of both cool, giant stars (the donor star), and of hot dwarf stars (the accreting...

Matthew Templeton
May 30, 2012 - 8:28am

RY Sagittarius is a fine R Coronae Borealis star coming back into easy view as we enter the Milky Way bulge season.  The R CrB stars are highly evolved objects whose origin remains somewhat mysterious.  They are perhaps the product of the merger of two white dwarf stars, or are...

Matthew Templeton
May 14, 2013 - 10:05am

RY UMa is a semiregular variable of type SRa, meaning it has reasonably stable pulsations over part of its history, but with lower amplitude than their Mira-type cousins.  In this case, RY UMa has a well-defined pulsation period around 310 days, but it also has a supercycle of several...

Matthew Templeton
November 6, 2012 - 11:51am

RZ Vul is an interesting RV Tauri star of the RVB subclass.  The RV Tauri stars are highly evolved giant stars that vary by pulsating.  The RVB stars are characterized by long supercycles where the mean magnitude drops by a magnitude or more while the star maintains its underlying...

Matthew Templeton
October 28, 2011 - 7:03am

S Cas is a well-observed Mira variable of the northern skies with a longer-than-average period over 600 days.  It currently has a range of over eight magnitudes, although that seems to have varied in the past; as recently as the 1970s S Cas seemed to have a series of faint maxima where...

Matthew Templeton
July 16, 2012 - 7:22am

S Cephei is a highly evolved carbon-type Mira variable with a period of about 485 days.  S Cep exhibits the large amplitude pulsations typical of Miras, but there is more irregularity present in the light curve than usual.  The shape and amplitude of each cycle vary from one to the...

Matthew Templeton
September 10, 2012 - 12:49pm

S Pav is a bright southern semiregular with a primary pulsation period near 400 days.  Over extended periods of time, the light curve shows clear evidence of variations in the light curve that may be due to secondary pulsation modes.  When multiple periods are present in a light...

Matthew Templeton
August 30, 2010 - 12:35pm

S Persei is one of the supergiant semiregular pulsating variables of type SRc.  These luminous stars, supergiants of the upper HR diagram, undergo a variety of different behaviors all caused by pulsation of one kind or another.  Some, like Betelgeuse, vary inconspicuously by no more...

Matthew Templeton
April 19, 2011 - 10:01am

S Serpentis is a fine example of a Mira variable with a bump in its light curve.  There are a number of Miras that show cycle-to-cycle variations in their light curves, and such variability is more common than not among the Mira class of stars.  The reasons why bumps or secondary...

Matthew Templeton
December 2, 2011 - 10:08am

Supernova 2011fe was detected in late August 2011 in the nearby galaxy M101, and has put on a beautiful show for northern skywatchers since.  SN 2011fe is a type-Ia supernova, which originate from accreting white dwarfs in binary star systems.  When the white dwarf reaches a critical...

Matthew Templeton
July 18, 2010 - 11:28am

SS Cygni is a dwarf nova -- a binary star system composed of a normal sunlike-star transferring matter onto a white dwarf companion star.  The matter being transferred forms an accretion disk around the white dwarf, and this disk sometimes goes into outburst, becoming hot and bright for a...

Matthew Templeton
January 31, 2012 - 2:11pm

SS Gem is a bright example of the RV Tauri class, and more specifically of the RVa subclass whose mean brightness remains relatively constant.  (The RVb class, of which a star like U Mon is an example, are characterized by long-period changes in brightness.)  They're...

Matthew Templeton
May 4, 2012 - 11:08am

SS Vir is a semiregular variable with an "inconvenient" period of 361 days, which is close enough to one year that we cover nearly the same phase range year after year.  This makes it challenging to understand the light curve without lots of data.  To make things even more...

Matthew Templeton
December 6, 2011 - 12:34pm

SU Tau is a well-observed R Coronae Borealis star.  Like the prototype of the class, SU Tau undergoes very dramatic fadings of several magnitudes that occur seemingly at random; the star may remain constant between 9th and 10th magnitude for several years, and then exhibit wild drops in...

Matthew Templeton
March 18, 2011 - 12:51pm

SX Herculis is a fine, bright semiregular variable with a period around 100 days.  Its light curve isn't too irregular, but it's clear that it undergoes changes in amplitude over time.  It is one of the prototypical SRd variables, classified by the GCVS as yellow...

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