PHOTOS OF THE SOLAR SYSTEM AND THE UNIVERSE FROM MY BACKYARD
Variable Stars
A variable star is one that exhibits changes to it brightness or size over time. All stars are variable in nature to some degree as they evolve in the course of consuming their mass through thermonuclear reactions. The rate and magnitude of this variability can range from almost imperceptable changes over long time spans to cataclysmic events that release unimaginable amounts of energy in a blink of the eye.
The study, observation and measurement of variable stars has been a a popular pursuit of both professional and amateur astronomers for hundreds of years and is too extensive a topic to be covered in detail here. The best source to learn about variable stars and how to observe them is to visit the website of “The American Association of Variable Star Observers” (AAVSO).
“Intrinsic Variable Stars“: where the variability stems from changes in the physical properties or processes occurring within the star itself and are general subdivided in two main subtypes:
Pulsating Variables where the luminosity of the star changes due to the expansion or contraction of the outer layers of the star.
Erupitve or Cataclysmic Variables such as Novae and Supernova. I have devoted an entire webpage on the Novae that I have observed which can be found on the Main Menu.
“Extrinsic Variable Stars“: where the changes in brightness of the star are due to external bodies periodically blocking the light reaching us.
A type of Extrinsic Variable is a “Eclipsing Variable Star”, where an unseen companion star or planet passes in front of the primary star and blocks part of its light for a period of time.
Another type of Extrinsic Variable is a “Rotating Variable Star”, one that has large sunspots or imperfections on its surface such that as it rotates, the light that reaches us varies as the sunspots rotate into our field of view.
Over the years I have routinely observed and measured the magnitudes of a number of Pulsating Variable stars. Below are some of the results of my observations.
SZ Cephei: M 8.7-16.0 328 days
One of the variable stars I have been following is SZ Cephei, a Mira type variable Star. On the right is a copy of the “Variable Star Index” Sheet (VSX) published by the AAVSO which lists the basic location data and the observational history for this variable. Click HERE to see a video I put together showing the dramatic 6 magnitude swing in brightness of this star.
The left-hand image is a light curve plot of my photometric measurements taken over a four year period that I submitted to the AAVSO. The Right-Hand image is a light curve plot of my measures along with the measures from other observers from around the world. The green points represent magnitude measures made using photographic techniques while the open circles are “Visual” (naked eye) magnitude estimates. Click on the frames for a larger view. * * *Just to its left of SZ Cephei is another variable star, GSC 04589-02354 which is classified as a slow irregular variable star (Type L) which exhibit very poor or no periodicity. The light curve plot of GSC 04589-02354 over the same four year period as SZ Cephei clearly shows the very irregular brightness fluctuations for this star but with a much smaller (~1 magnitude) swing in brightness. On the right is the VSX sheet for this star. Click on the frames for a larger view. * * *
T Draconis: M 7.2-13.5 433 Days
I like to refer to the Red Variable star T Draconis as “The Beating Heart of the Dragon” due to its location near the head of the constellation of Draco. T Draconis is a Mira type pulsating variable star with magnitude swings of over 2 magnitudes over a period of 13.6 months. Its close neighbor, UY Draconis, though it has a has a variable star designation is in fact non-variable. The T Dra -UY Dra pair also has the the Double Star designation of ES20 but in fact the attractive Red & White pair are not physically related.
The light curve for T Draconis (2000-2024). While the period appears to be rather constant over time there does appears too be some variability in the maxima and minima values from cycle to cycle.
The Light curve of T Draconis based on my measurements (2020-2024). From my measures the the current range of variability is approximately 2.5 magnitudes with the maxima and minima for the star values slowly creeping upward over the last few cycles. * * *
UX Cassiopeia: M 9.5-10.5 360 Days
Another variable star that I have been following is UX Cassiopeia, a Variable Carbon Star. On the right is a copy of the “Variable Star Index” Sheet (VSX) published by the AAVSO which contains the basic location data and observational history for this variable.A Light Curve of the pulsating variable star UX Cassiopeia showing my measurements of its changing magnitude over the course of four years. From the VSX sheet, this star is classified as a SRB variable (Semi-Regular variable) which means it has an poorly defined period which as can be seen is indeed the case when compared that of SZ Cephei or T Draconis above. Though the VSX sheet shows up to a ~2.0 magnitude swing in brightness, my measures over this time period record a change of only ~0.5 magnitude. * * *
Chi Cygni: M 3.3-14.2 408 Days
Chi Cygni is a Mira type variable star with a very large swing in magnitude – one of the largest of any variable star. At its brightest it can be an easy naked-eye star but it soon fades to magnitudes that require a small telescope to resolve. At its faintest it can be a challenging object to visually observe even in medium sized amateur scopes. The photos above show just how extreme the the change in brightness can be. * * *
The light curve above is from the AAVSO and shows the measurements of the fluctuating brightness of Chi Cygni submitted by observers from all over the world for the past 9 years. The green makers are photometric measures of the brightness based on photographs, while the open-circles are visual estimates. * * *
Supernova 2022hrs – Eruptive Variable
My photo of the “Galactic Supernova” SN-2020hrs, an example of a cataclysmic variable star located in the distant galaxy NGC 4647 in the constellation of Virgo. Supernova are cataclysmic variable stars that end their existence in a final massive gravitational collapse which produces such a prodigious amount of energy that they nearly outshine the total luminosity of its home galaxy. In the upper-left of the photo is a reference image showing the galaxy as it appeared before the eruption of the supernova. The other individual stars in the photo are foreground stars that are members of our own “Milky Way” Galaxy.
The light curve for SN 2022hrs shows the rapid rise in brightness due to the cataclysmic gravitational collapse and resulting obliteration of the star and then the slow fading of the remains. I submitted four measures of the brightness to the AAVSO which are the brown data points on the chart and are in good agreement with the values submitted by other observers. It should be kept in mind that this galaxy and supernova is 56 million light years distant. Only now in 2022, 56 million years after the event, is the light from this explosion reaching us ! * * *
Extrinsic Variables
X (Chi) Trianguli (J 3257) is an example of an Extrinsic Variable Star”. At first glance it appears to be a binary pair but is actually a triple star. It has a third unseen stellar companion (B) that orbits around X Tri with a period of 0.95 days. Its orbit is such that it passes in front of the main star blocking a portion of the light that reaches our eyes causing a 2 magnitude dimming of the main star – from magnitude ~9.0 down to magnitude ~11.0 and back up again over a four hour period. A video of this event that I put together can be found on the Videos page.
Views from Whitby Observatory 