LCO: A Star That Would Not Die

[bystander]

Astronomers Discover a Star That Would Not Die
Las Cumbres Observatory | 2017 Nov 08

Supernova Discovery Challenges Known Theories of the Death of Stars

iPTF14hls grew bright and dim again at least five times over two years. This behavior has never been seen in previous supernovae, which typically remain bright for approximately 100 days and then fade. Adapted from Arcavi et al. 2017, Nature. Credit: LCO/S. Wilkinson

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Supernovae, the explosions of stars, have been observed in the thousands and in all cases they marked the death of a star. Astronomers at Las Cumbres Observatory have discovered a remarkable exception - a star that exploded multiple times over a period of more than fifty years. Their observations are challenging existing theories on these cosmic catastrophes.

When the supernova, named iPTF14hls, was discovered in September of 2014 by the Palomar Transient Factory, it looked like an ordinary supernova. Several months later, LCO astronomers noticed something that they had never seen before - the supernova was growing brighter again after it had faded.

A normal supernova rises to peak brightness and fades over 100 days. Supernova iPTF14hls, on the other hand, grew brighter and dimmer at least five times over three years.

When astronomers went back and looked at archival data, they were astonished to find evidence of an explosion in 1954 at the same location. This star somehow survived that explosion and exploded again in 2014. ...

Astronomers Discover a Star That Would Not Die
W. M. Keck Observatory | 2017 Nov 08

A Star That Would Not Die
University of California, Santa Barbara | 2017 Nov 08

Star exploded, survived, and exploded again more than 50 years later
Carnegie Institution for Science | 2017 Nov 08

Energetic eruptions leading to a peculiar hydrogen-rich explosion of a massive star - Iair Arcavi et al

• Nature 551(7679):210 (09 Nov 2017) DOI: 10.1038/nature24030

[Ann]

This is incredibly interesting.

I just contacted two people behind this discovery, and one of them informed me that this amazing supernova resides in a dwarf irregular galaxy 500 million light-years away. The galaxy is similar to the Small Magellanic Cloud in mass. It has no designation. The galaxy is metal-poor, but not extremely so.

Incredibly interesting!

Ann

[neufer]

I just contacted two people behind this discovery, and one of them informed me that this amazing supernova resides in a dwarf irregular galaxy 500 light-years away. The galaxy is similar to the Small Magellanic Cloud in mass. it has no designation. The galaxy is metal-poor, but not extremely so.

A dwarf irregular galaxy 500,000(,000) light-years away

[Ann]

I just contacted two people behind this discovery, and one of them informed me that this amazing supernova resides in a dwarf irregular galaxy 500 light-years away. The galaxy is similar to the Small Magellanic Cloud in mass. it has no designation. The galaxy is metal-poor, but not extremely so.

A dwarf irregular galaxy 500,000(,000) light-years away

That is so true. I wrote my post when I was in a real hurry.

Ann

[neufer]

<<iPTF14hls [Distance: 509,456,262 ly] is an unusual supernova star that has erupted continuously for the last three years, and it may have exploded between two and five times since 1954.

The star iPTF14hls was discovered in September 2014 by the Intermediate Palomar Transient Factory, and astronomers identified it as an exploding star in January 2015. It was thought then that it was a single supernova event (Type II-P) that would dim in about 100 days, but instead, it continued its eruption for more than 600 days while fluctuating in brightness at least five times. The brightness varied by as much as 50% on an irregular timescale, as if it was exploding over and over again. Also, rather than cooling down as expected, the star maintained a near-constant temperature of about 5,970 K.

The host galaxy of iPTF14hls is a star-forming dwarf galaxy, implying low metal content1, and the weak iron-line absorption seen in the supernova spectra are consistent with a low metallicity progenitor. The researchers also remark that the debris expansion rate is slower than any other known supernova by a factor of 6, as if exploding in slow-motion. However, relativistic time dilation would cause the spectrum to be red-shifted by the same factor of 6, which is inconsistent with their observations.

Current theory predicts that the star would consume all its hydrogen in the first explosion, and depending on the initial size of the star, the remnants of the core should form a neutron star or a black hole, so it is thought that there is a novel unidentified phenomenon happening. There is no known theory that explains the observation. One hypothesis is that it could be the first example of an explosion that involves burning antimatter in a stellar core. That would cause the star to become extremely unstable, and undergo repeated bright eruptions over periods of years. Another hypothesis is the pulsational pair-instability supernova, a massive star that may lose about half its mass before a series of violent pulses begins. On every pulse, material rushing away from the star can catch up with earlier ejected material, producing bright flashes of light as it collides, simulating an additional explosion. But that explanation does not explain the continued presence of hydrogen or the energetics observed.>>

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