Yes my friends we will now have a regular posting for the Talavera Space Hut as we affectionately call it. This is where citizen science is happening! The small 8 foot square roll-off which is located right in my backyard houses a 14” Celestron Schmidt Cassegrain reflector and an Lhires (Littrow high resolution) spectrograph. The spectrograph is the instrument that analyzes light coming from deep space objects and is able to record in high resolution the spectral emission or absorption lines produced. You can do a search on this site for “spectroscopy” and I am sure a hundred posts will come up on this topic. The main imaging camera here is an Atik 460EX and the guider is an ASI 174.
In this case we are typically looking at stars and specifically “variable” stars. These are stars that vary in brightness due to physical properties happening in the star or in its local environment. They are probably the most extensively studied objects in space. Amateurs are actively involved in this process and an entire organization, the AAVSO (American Association of Variable Star Observers) was established in 1911 to enable anyone, anywhere, to participate in scientific discovery through variable star astronomy. You and I, with fairly modest backyard equipment, can play a crucial role in real discovery even today! No joke. Let’s face it. There are a lot of stars out there. Professional astronomers do not have access to telescopes every clear night like we do. They have to apply months in advance for telescope time on the world’s largest telescopes just to get a few nights of observing time. The good news for them is that many of these stars do not require large optics to observe and our equipment these days is more than adequate to acquire data that is accurate enough for scientific publication. That is amazing!
The star gamma Cas or the third brightest star in the constellation Cassiopeia seems like a harmless pretty blue white twinkling star that is easy to spot. However it is hardly that. It is a specific type of variable star called a Be or B “emission” star belonging to the spectral class B being the second most luminous spectral type and these are typically stars 3-100 times as massive as the Sun and can be 5-10 times as large.
The subtype of Be is the most extensively studied because these stars are frequently not just one star but part of a binary system where the companion star is much smaller and can in many cases be close enough to the parent B star that gravity causes a transfer of mass between the 2. The smaller star is typically a white dwarf but could possibly be even a neutron star or a black hole! This mass transfer often creates a rotating shell of gas. We are able to learn more about the physical properties of these systems by observing their spectra. The gas shell emits light and as it changes shape and position the spectrum produced can also change over time. Gamma Cassiopeia was the first Be star discovered, in the 1860’s, and it is still extensively studied. In August of this year a sudden outburst of emission and variability in the helium line of the Gamma Cas spectrum was detected and the call was made for additional observations to be done over the next several months. The star is well positioned now for observations in the Northern Hemisphere and it is a very easy target since it so bright.
Three observations of the star were made from the end of September through the end of October. The 100 Angstrom region containing the helium 6678 line was targeted and you can see the results here:
There is predominantly a double peak emission in the region of the Helium line 6678 Angstroms (orange line). While the physics is obviously beyond the scope of this post, it is clear there is dynamic change happening even over the course of a month! The second or red emission peak is decreasing in intensity (arrow) I was very excited to be able to capture for the first time a spectral profile beyond the H-alpha region. The significance of these changes is currently under investigation so I cannot tell you exactly what this means yet!
Several observations have been submitted by amateurs of this phenomenon (shown above). The spectrum I captured is in yellow. The black arrow at the bottom is pointing to a possible developing flare within the red emission peak.
Alright folks, stay tuned for more on the gamma Cass helium emission phenomenon. What is actually happening there? Have we discovered a new stellar physical process happening within these circumstellar discs?
Thanks for reading!