Twenty-one years of observations by the Chandra X-ray Observatory have been compiled to produce a film about Eta Carinae. The film traces the after-effects of an explosion so large that we lack adjectives to express its magnitude.
For 18 years in the mid-19th century, the leaderboard of brightest stars was turned upside down when the fainter star Eta Carinae entered the charts, peaking several times at No. 2, behind only Sirius. The world hasn’t seen anything like this since Kepler’s supernova exploded in 1604, and Eta Carinae has been shining bright for much longer. The star responsible is now surrounded by dust emitted by the event, frustrating optical astronomers in their quest to understand what happened, but instruments working in other parts of the spectrum, such as X-rays, have had greater success.
Dust wasn’t the only thing that hampered observing Eta Carinae. It lies so far south that none of the largest telescopes of the era could see it. Only in recent decades, when pioneering instruments were built high in the Andes and space telescopes became able to see the entire sky, did astronomers begin to catch up.
Eta Carinae are actually two big stars. The smallest one has a mass of about 30-80 times the mass of the Sun. The largest mass is currently believed to be around 90-100 solar masses. This makes it among the most massive stars in our region of the galaxy, but 200 years ago it was still more massive. The so-called “super eruption” that produced the extra brightness ejected between 10 and 45 times the mass of the Sun, explaining why we need instruments like Chandra to see inside.
Even Chandra lacks the resolution needed to see the two stars separately, but the distorted ring of detectable X-ray emissions has given astronomers a lot of knowledge about their behavior.
These observations reveal that the material thrown up in the Big Bang is expanding at a tremendous speed of 7 million kilometers per hour (4.5 million miles per hour). At this speed, it will reach from the Sun to the Earth in less than one day.
The cloud of material surrounding Eta Carinae, which was erupted during the great eruption and previous events, is known as the Dwarf Nebula. The first X-ray telescopes revealed a bright ring of sources within. However, astronomers have only now discovered a secondary shell that produces X-rays three times larger.
“We interpret this faint X-ray shell as a blast wave from the Big Bang of the 1840s,” NASA’s Dr. Michael Corcoran said in an article. statement. “It tells an important part of Eta Carinae’s backstory that we wouldn’t have known otherwise.”
Eta Carinae’s complex ocean reveals interactions between the legacies of at least two volcanic eruptions
Image credit: NASA/SAO/GSFC/M. Corcoran et al.
The similarity in shell shape to the Homunculus led Corcoran and his colleagues to conclude that they were both products of the same event. They believe that the Big Bang preceded another event between 800 and 220 years ago. The low-density gas from this event is moving incredibly fast by human standards, but it’s still slow enough. Material from the great eruption catches up, creating a shock wave reaching millions of degrees and emitting X-rays that Chandra sees. The visible matter in the Homunculus lags behind, moving at about a third of its speed.
“The shape of this faint X-ray shell is a development in my mind,” said Dr. Kenji Hamaguchi of the University of Maryland. “It shows us that the dim crust, the dwarf, and the bright inner ring are all likely generated by explosions from the star system.”
Eventually, Eta Carinae will become a supernova, closer in brightness to a full moon than the brightest star, but the question of when we can expect that remains unanswered.
The study is open access in Astrophysical Journal.
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