BRITE-Constellation (BRITE stands for BRight Target Explorer) will photometrically measure low-level oscillations and temperature variations in stars brighter than visual apparent magnitude about 4.0. These stars turn out, for the most part, to be among the most luminous – either massive stars during any of their evolutionary phases or medium-mass stars at the very end of their nuclear-burning phases. For all evolutionary stages of stars – condensation from the interstellar medium, ignition of hydrogen, evolution to supergiants/giants until their deaths – there is a strict rule:
More massive stars are hotter, evolve faster and die earlier. Intrinsically luminous stars dominate the ecology of the Universe: During their relatively brief lives and in their spectacular deaths as supernovae, massive stars inject enriched gas into the interstellar medium adding heavy elements critical to the formation of future stars, terrestrial planets and organics.
Medium-mass stars also do this, but without exploding as supernovae - rather by ejecting planetary nebulae at the end of their lives. Their individual modesty is compensated for by their large numbers.
Although the role of luminous stars in the Universe is so crucial and although they are the brightest stars in the night sky, they are still inadequately understood.
BRITE-Constellation will capture the light of these luminous stars and shed light on their structures and histories, uncovering unique clues to the origins of our own Sun and Earth. With these small space telescopes the role that stellar winds play in setting up future stellar life cycles will be investigated. The nano-satellites will measure stellar pulsations to probe the histories and ages of luminous stars through asteroseismology.
The figure shows a Hertzsprung Russel Diagram with luminosity, in solar units, plotted versus temperature or, equivalently, spectral type.
Furthermore, as tests with engineering models have demonstrated, it will likely be possible to perform photometry with reduced accuracy of many more stars down to as faint as magnitude 7, which opens a wide field of additional science research, among which are:
- Planet detection around a large sample of massive stars
- Study and discovery of more classical pulsating stars down to low amplitudes
- Study of stars in Clusters and Associations
- Investigation of large-scale structures (e.g., spots) on stars and their temporal evolution
- Unexpected events (e.g. bright comets, novae ....)
- Enlarging the base of proven constant stars, which can be used as photometric standards
- Granulation signature in the Hertzsprung Russel Diagram