Actually, you cannot even believe stars to be what they look like. An ultimate example is Eta Carinae, a difficult system thought to be a supernova in the 19th century but later found to be faking it. And now, a new study proposes that it has been faking it for a long time. American scientists have wisely analyzed images of Eta Carinae, a system pretending of two large stars encircled by a nebula, and revealed that the “Great Eruption” of the mid-1800s was just one of at least three mass discharges that have been happening in the last 7 hundred years. Lead author Megan Kiminki, a doctoral student from the University of Arizona said, in a statement, "Eta Carinae is what we call a supernova pretender. The star happened to be very bright as it blew off a lot of solid, but it was still there."
Natural color image of Eta Carinae and the gas that surrounds it. HST/NASA/ESA
In a paper, obtainable online and soon to be written in the Monthly Notices of the Royal Astronomical Society, the researchers aligned pictures of the binary star-system taken over many years and recognized that Eta Carinae was bounded by more than 800 gas blobs. By guessing their velocities, the scientists derived that this material was ejected by the star in two separate outbreaks in the mid-13th and mid-16th centuries, making it "faked" a supernova at least three times.
Kiminki added, "We do not actually know what is going on with Eta Carinae. But knowing that Eta Carinae exploded at least three times tells us that whatsoever causes those eruptions must be a periodic process because it would not be probably that each eruption is initiated by a unique mechanism."
One of the stars in the system is approaching the end of its life, meaning it might quickly become a real supernova. Since Eta Carinae is about 7,000 light years from Earth, it might previously have occurred and we are yet to see it.
Co-author Nathan Smith, also from the University of Arizona said, "Even though we still have not figured out the fundamental physical mechanism that caused the 19th-century eruption, we now know that it is not a one-time occasion. That makes it tougher to understand, but it is also a serious piece of the puzzle of how huge stars die. Stars like Eta Carinae apparently refuse to go quietly into the night."