New Echoes of Eta Carinae Explosion Seen by Aborigines 150 Years Ago
More than 7,500 years ago Eta Carinae, one of the Milky Way’s most massive stars, belched 20 times the sun’s mass in what has come to be known as the Great Eruption. For 10 years it was among the brightest objects in the sky, its magnitude peaking in 1843, when its brilliance was second only to that of the star Sirius.
Now, scientists are getting a new look at an old flame. In a study published in the journal Nature this week, scientists determined that the light from the eruption, whose residue now forms the Homunculus Nebula, had bounced off other stellar phenomena and is now reaching Earth. What they’re seeing unfolds like a movie, and it plays like the denouement of this star-crossed tale: The star could go supernova any time, according to a new report in the journal Nature.
"We know it's close to the end of its life," said the lead author of the paper, astronomer Armin Rest of the Space Telescope Science Institute in Baltimore, to Time magazine. "It could explode in a thousand years, or it could happen tomorrow."
As is usual with the deep questions of life, the answers merely generate more questions. In Eta Carinae’s case the mystery presented is that the explosion was colder than anyone had previously thought, which adds intrigue as to the trigger, according to Space.com.
"Eta Carinae is probably the most studied object in our galaxy," Rest told Space.com.
Back in the 1800s, European scientists weren’t the only ones watching. The Boorong aboriginal people of northwestern Victoria, Australia, not only observed the Great Eruption of Eta (?) Carinae but also incorporated the event into their oral traditions, according to the findings in a study published in November 2010 in the Australian Journal for Astronomical History & Heritage.
“The observations by the Boorong represent the first and only definitive indigenous record of the Great Eruption of Eta Carinae identified in the literature to date,” wrote Duane W. Hamacher of the department of indigenous studies and David J. Frew of the department of physics and astronomy, both of Macquarie University in Sydney.
That catastrophic eruption cost Eta Carinae a good 10 percent of its substance, according to Space.com, and became known as a “supernova imposter”—the also-ran in the spectrum of stellar explosions. A supernova proper is when the entire star explodes, then collapses in on itself to become a black hole.
Eta Carinae settled down after the supernova imposter but now may be poised to undergo the real deal. As a luminous blue variable—the scientific term for a star whose light vacillates between bright and dim—its changes indicate internal instability that lead to a dramatic loss of mass after each cycle, Space.com said, calling the Great Eruption of Eta Carinae “an especially catastrophic event.”
Some of the light released from that event bounced off dust clouds in interstellar space, the study authors said, which delayed the light’s arrival to Earth. This “light echo” is only now arriving, but rather than being late to the party, it is coming just when we have instruments capable of translating it into a chronology of events.
Because the resulting light show played out over 20 years, modern astronomers can do the same, watching the show unfold year by year as the light arrives, Time said. Moreover, with light bouncing off a many dust clouds whose distances from the star vary, different phases are visible simultaneously, Time said.
"We took observations nine months ago," Rest told Time, "and we were looking at 1843. Now we're looking at 1844. It's like a movie."
The Boorong aboriginal people of northwestern Australia did not wait for fancy instruments. They merely incorporated the vision into their dreamtime and oral lore.
Using an 1858 paper by William Edward Stanbridge and matching it to early southern star catalogues, Hamacher and Frew identified a number of astronomical objects and events observed by the Boorong, who prided themselves on knowing more about astronomy than any other tribes, the study authors said.
“Aboriginal Australians had a significant understanding of the night sky and frequently incorporated celestial objects and transient celestial phenomena into their oral traditions, including the sun, moon, stars, planets, the Milky Way and Magellanic Clouds, eclipses, comets, meteors, and impact events,” Hamacher and Frew wrote. “This identification of a transient astronomical event supports the assertion that aboriginal oral traditions are dynamic and evolving, and not static.”