Sakurai’s Object Evolution Witnessed in Real Time
Stellar lifetimes last billions of years. While we can observe slight changes in nebulae over time, the only appreciable stellar transformation that we are capable of witnessing during our relatively short lifetimes is a supernova. However, in 1996 an astronomer detected the blinding helium flash of the star as it swelled up and was reborn from a white dwarf to a (most likely) red giant star. The star, located in the constellation Sagittarius about 10,000 light years away, was named after its discoverer and was henceforth known as Sakurai’s Object.
A helium flash occurs in a small percentage of stars that are 0.5-2.5 solar masses at the end of their life. When these stars have used up their nuclear fuel, a white dwarf is all that remains. Every now and again, the hydrogen and helium in the burnt-out core are able to re-ignite and breathe new life into the star, though for only a short time. Sakurai’s Object is only the third star undergoing a final helium shell flash that has been observed.
Following the helium flash, an incredible amount of dust was generated, which prevented Sakurai’s Object from being observed with visible wavelengths. Infrared more readily cuts through stellar dust, so astronomers have been using that to monitor the star and look for signals that indicate the dust shield is beginning to dissipate.
Astronomers used a special tool on the Gemini North telescope, the Altair adaptive optics system, to image the shell. The team was able to get an unprecedented amount of detail, with a resolution of 0.04 arc second. Though the star itself is still heavily concealed by dust, they were able to make out a faint fuzzy object back in 2010. Recent observations show that Sakurai’s Object is forming a bipolar nebula, as gas appears to be moving away in either direction from the star in the middle.
Though the images they collected have not yet been released, the researchers note that the attached painting (used here as the header) is what the dust shell might look like around the star. They believe Sakurai’s Object might have a planetary system or possibly an accompanying star.
The recent research regarding Sakurai’s Object comes from lead author Kenneth Hinkle of the National Optical Astronomy Observatory and will be published in the Astrophysical Journal.
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