ESO/HEIC: Spinning Black Hole Swallowing Star Explains Superluminous Event

[bystander]

Spinning Black Hole Swallowing Star Explains Superluminous Event
ESA Hubble | ESO | Science Release | 2016 Dec 12

ESO, Hubble help reinterpret brilliant explosion

[img3="Close-up of star near a supermassive black hole"]https://cdn.eso.org/images/screen/eso1644a.jpg[/img3][img3="Supermassive black hole with torn-apart star
Credits: ESO, ESA/Hubble, M. Kornmesser"]https://cdn.eso.org/images/screen/eso1644b.jpg[/img3][hr][/hr]

An extraordinarily brilliant point of light seen in a distant galaxy, and dubbed ASASSN-15lh, was thought to be the brightest supernova ever seen. But new observations from several observatories, including ESO and the NASA/ESA Hubble Space Telescope, have now cast doubt on this classification. Instead, a group of astronomers propose that the source was an even more extreme and rare event -- a rapidly spinning black hole ripping apart a passing star that came too close.

In 2015, the All Sky Automated Survey for SuperNovae (ASAS-SN) detected an event, named ASASSN-15lh, that was recorded as the brightest supernova ever — and categorised as a superluminous supernova, the explosion of an extremely massive star at the end of its life. It was twice as bright as the previous record holder, and at its peak was 20 times brighter than the total light output of the entire Milky Way.

An international team, led by Giorgos Leloudas at the Weizmann Institute of Science, Israel, and the Dark Cosmology Centre, Denmark, has now made additional observations of the distant galaxy, about 4 billion light-years from Earth, where the explosion took place and they have proposed a new explanation for this extraordinary event.

“We observed the source for 10 months following the event and have concluded that the explanation is unlikely to lie with an extraordinary bright supernova. Our results indicate that the event was probably caused by a rapidly spinning supermassive black hole as it destroyed a low-mass star,” explains Leloudas.

In this scenario, the extreme gravitational forces of a supermassive black hole, located in the centre of the host galaxy, ripped apart a Sun-like star that wandered too close — a so-called tidal disruption event, something so far only observed about 10 times. In the process, the star was “spaghettified” and shocks in the colliding debris as well as heat generated in accretion led to a burst of light. This gave the event the appearance of a very bright supernova explosion, even though the star would not have become a supernova on its own as it did not have enough mass.

The team based their new conclusions on observations from a selection of telescopes, both on the ground and in space. Among them was the Very Large Telescope at ESO’s Paranal Observatory, the New Technology Telescope at ESO’s La Silla Observatory and the NASA/ESA Hubble Space Telescope [1]. The observations with the NTT were made as part of the Public ESO Spectroscopic Survey of Transient Objects (PESSTO). ...

A New Light on Stellar Death
University of California, Santa Barbara | 2016 Dec 12

"Brightest Supernova” not a Supernova, but a Star Ripped Apart by a Spinning Black Hole
Las Cumbres Observatory | 2016 Dec 12

Brightest hypernova ever, found to be a rotating black hole ripping a star apart
Netherlands Institute for pace Research (SRON) | 2016 Dec 12

The Superluminous Transient ASASSN-15lh as a Tidal Disruption Event from a Kerr Black Hole - G. Leloudas et al

• Nature Astronomy 1:0002 (2017 Jan) DOI: 10.1038/s41550-016-0002
  arXiv.org > astro-ph > arXiv:1609.02927 > 09 Sep 2016

http://asterisk.apod.com/viewtopic.php?t=34972
http://asterisk.apod.com/viewtopic.php?t=35589

[Ann]

Click to view full size image

Artist's impression of a spinning black hole with an accretion disk.
Credit: ESO, ESA/Hubble, M. Kornmesser.

Astronomers have recently proposed that what looked like a super-duper bright supernova was instead a spinning black hole swallowing a star. Personally I find it fascinating that the obliteration of an ordinary, probably sunlike star, along with the super-heating of the accretion disk around the spinning black hole as the star was torn apart, could create a light-flash brighter than any supernova seen so far. It would seem that snacking on stars could lead to the most brilliant cosmic burps.

V838 Monocerotis and its light echo as imaged
by the Hubble Space Telescope on December 17, 2002.
Credit: NASA/ESA.

Which makes me think of a far less luminous but still extraordinary event in the Milky Way, the extreme brightening of the star now known as V838 Monocerotis.

Wikipedia wrote:

V838 Monocerotis (V838 Mon) is a red variable star in the constellation Monoceros about 20,000 light years (6 kpc) from the Sun.[5] The previously unknown star was observed in early 2002 experiencing a major outburst, and was possibly one of the largest known stars for a short period following the outburst. Originally believed to be a typical nova eruption, it was then realized to be something completely different. The reason for the outburst is still uncertain, but several conjectures have been put forward, including an eruption related to stellar death processes and a merger of a binary star or planets.
...
The star brightened to about a million times solar luminosity[7] and absolute magnitude of −9.8,[3] ensuring that at the time of maximum V838 Monocerotis was one of the most luminous stars in the Milky Way galaxy.

Wikpedia wrote:

Another possibility is that V838 Monocerotis may have swallowed its giant planets. If one of the planets entered into the atmosphere of the star, the stellar atmosphere would have begun slowing down the planet. As the planet penetrated deeper into the atmosphere, friction would become stronger and kinetic energy would be released into the star more rapidly. The star's envelope would then warm up enough to trigger deuterium fusion, which would lead to rapid expansion. The later peaks may then have occurred when two other planets entered into the expanded envelope. The authors of this model calculate that every year about 0.4 planetary capture events occur in Sun-like stars in the Milky Way galaxy, whereas for massive stars like V838 Monocerotis the rate is approximately 0.5–2.5 events per year.

Whatever happened to V838 Monocerotis, it became tremendously bright. To me, it is just fascinating to think that stars may eat their planets and black hole might eat stars, and in both cases incredibly luminous events would be triggered.

We are probably lucky that Jupiter orbits 5 AU from the Sun, and even Mercury is relatively far away from the solar "surface". Things will change when the Sun turns into a red giant... but by then we won't be here, fortunately.

Ann

[neufer]

• "The great Cronos swallowed as each came forth from the womb to his mother's knees with this intent, that no other of the proud sons of Heaven should hold the kingly office amongst the deathless gods. For he learned from Earth and starry Heaven that he was destined to be overcome by his own son, strong though he was, through the contriving of great Zeus." - Hesiod "Theogony".

[b][size=150]Saturn Devouring His Son was one of 6 works with which Goya decorated the dining room[/size][/b]

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<<Saturn Devouring His Son is the name given to a painting by Spanish artist Francisco Goya. According to the traditional interpretation, it depicts the Greek myth of the Titan Cronus (in the title Romanized to Saturn), who, fearing that he would be overthrown by one of his children, ate each one upon their birth. The work is one of the 14 Black Paintings that Goya painted directly onto the walls of his house sometime between 1819 and 1823. It was transferred to canvas after Goya's death and has since been held in the Museo del Prado in Madrid.

In 1819, Goya purchased a house on the banks of Manzanares near Madrid called Quinta del Sordo (Villa of the Deaf Man). It was a two-story house which was named after a previous occupant who had been deaf, although the name was fitting for Goya too, who had been left deaf after contracting a fever in 1792. Between 1819 and 1823, when he left the house to move to Bordeaux, Goya produced a series of 14 works, which he painted with oils directly onto the walls of the house. At the age of 73, and having survived two life-threatening illnesses, Goya was likely to have been concerned with his own mortality, and was increasingly embittered by the civil strife occurring in Spain. Although he initially decorated the rooms of the house with more inspiring images, in time he overpainted them all with the intense haunting pictures known today as the Black Paintings. Uncommissioned and never meant for public display, these pictures reflect his darkening mood with some intense scenes of malevolence and conflict.

Various interpretations of the meaning of the picture have been offered: the conflict between youth and old age, time as the devourer of all things, the wrath of God and an allegory of the situation in Spain, where the fatherland consumed its own children in wars and revolution. There have been explanations rooted in Goya's relationships with his own son, Xavier, the only of his six children to survive to adulthood, or with his live-in housekeeper and possible mistress, Leocadia Weiss; the sex of the body being consumed can not be determined with certainty. It has been said that the painting is "essential to our understanding of the human condition in modern times, just as Michelangelo's Sistine Chapel ceiling is essential to understanding the tenor of the 16th century".

Goya may have been inspired by Peter Paul Rubens' 1636 picture of the same name. Rubens' painting, also held at the Museo del Prado, is a brighter, more conventional treatment of the myth: his Saturn exhibits less of the cannibalistic ferocity portrayed in Goya's rendition. Goya had produced a chalk drawing of the same subject in 1796-7 that was closer in tone to Rubens' work: it showed a Saturn similar in appearance to that of Rubens', daintily biting on the leg of one of his sons while he holds another like a leg of chicken, with none of the gore or madness of the later work.

Although they were not meant to be seen by the public, the paintings remain important works in Goya's oeuvre. When Goya went into self-imposed exile in France in 1823, he passed Quinta del Sordo to his grandson, Mariano. After various changes of ownership, the house came into the possession of the Belgian Baron Emile d'Erlanger in 1874. After 70 years on the walls of Quinta del Sordo, the murals were deteriorating badly and, in order to preserve them, the new owner of the house had them transferred to canvas under the direction of Salvador Martinez Cubells, the chief art restorer at the Museo del Prado. After showing them at the Exposition Universelle of 1878 in Paris, d'Erlanger eventually donated them to the Spanish state. The effects of time on the murals, coupled with the inevitable damage caused by the delicate operation of mounting the crumbling plaster on canvas, meant that most of the murals required restoration work and some detail may have been lost.>>