This was my second spectrum accepted into the BeSS database. It is a high resolution spectrum I just obtained of the H alpha region of the Be star (B emission) HD43544. This is a 6th magnitude star in the well known Winter constellation Canis Major. Captured with the Lhires III spectrograph, C14, Atik 460EX, Paramount ME from Las Cruces, NM. Many B spectral type stars exhibit emission lines rather than absorption (meaning they spike upward , not downward ). These are actively researched now because it is believed that several, possibly most B stars, are actually part of close binary systems with a small “type O subdwarf” ,or white dwarf ( or in some cases neutron star or even black hole!) accounting for mass transfer between the 2 stars which gives rise to the rapid rotation of the B star and formation of a gaseous disc surrounding the star. This is the reason for the emission feature. Close analysis of the emission profile changes over time in the HA region or other regions can yield a solution for orbital parameters of a binary system, thus proving they exist! The peaked nature of the Ha emission is dependent on line of sight from earth as shown in this schematic:
Position ‘A’ viewed from Earth would be looking directly ‘above’ the star where we see only an emission peak. Position ‘B’ is an oblique view where we would see 2 peaks with central dip depending on degree of obliquity but this “dip” gradually increases in depth toward the “C” position where we see the full absorption component (peak pointing down) at the H alpha 6563 angstrom point when we are looking at the star edge on!
I think one of the compelling things about amateur spectroscopy is that this kind of data that I have shown here, despite being obtained with amateur equipment, is still highly sought after by professional researchers. Once these spectra are “validated” by the BeSS administrators then they are considered accurate enough to be used in astrophysical research. Remember that most astronomers do not have daily access to equipment like we do! They have to vie for telescope time with many others and perhaps they will get a day or a few days once every year or more, if they are lucky, on one of the big telescopes either on Earth or in space but this resource that we provide enables researchers to acquire data any time anywhere at will! Spectroscopy or the analysis of light from stars and other objects in space is the way that we have figured out how stars work and evolve over time as well as the large scale structure of the universe. It is also a very viable way that we amateurs, you and me , can still participate and be relevant in new discoveries out there in our universe! For more information on astronomical spectroscopy you can read my primer that I wrote for ‘Reflector” magazine in this post
Thanks for reading!
Dr Dave
