From European Southern Observatory: “Cosmic Serpent”

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From European Southern Observatory

19 November 2018
Joseph Callingham
Postdoctoral Research Fellow
Netherlands Institute for Radio Astronomy (ASTRON)
Dwingeloo, The Netherlands
+31 6 2929 7915
callingham@astron.nl

Calum Turner
ESO Public Information Officer
Garching bei München, Germany
+49 89 3200 6670
pio@eso.org

Coils of Apep
1
The VISIR instrument on ESO’s Very Large Telescope has captured this stunning image of a newly discovered massive triple star system. Nicknamed Apep after an ancient Egyptian deity, this may be the first ever gamma-ray burst progenitor found.

ESO/VISIR on UT3 of the VLT

This serpentine swirl, captured by the VISIR instrument on ESO’s Very Large Telescope (VLT)[see VLT below], has an explosive future ahead of it; it is a Wolf-Rayet star system, and a likely source of one of the most energetic phenomena in the Universe — a long-duration gamma-ray burst (GRB).

“This is the first such system to be discovered in our own galaxy,” explains Joseph Callingham of the Netherlands Institute for Radio Astronomy (ASTRON), lead author of the study [Nature Astronomy] reporting this system. “We never expected to find such a system in our own backyard” [1].


ESOcast 185 Light: Cosmic Serpent

The system, which comprises a nest of massive stars surrounded by a “pinwheel” of dust, is officially known only by unwieldy catalogue references like 2XMM J160050.7-514245. However, the astronomers chose to give this fascinating object a catchier moniker — “Apep”.

Apep got its nickname for its sinuous shape, reminiscent of a snake coiled around the central stars. Its namesake was an ancient Egyptian deity, a gargantuan serpent embodying chaos — fitting for such a violent system. It was believed that Ra, the Sun god, would battle with Apep every night; prayer and worship ensured Ra’s victory and the return of the Sun.

GRBs are among the most powerful explosions in the Universe. Lasting between a few thousandths of a second and a few hours, they can release as much energy as the Sun will output over its entire lifetime. Long-duration GRBs — those which last for longer than 2 seconds — are believed to be caused by the supernova explosions of rapidly-rotating Wolf-Rayet stars.

Some of the most massive stars evolve into Wolf-Rayet stars towards the end of their lives. This stage is short-lived, and Wolf-Rayets survive in this state for only a few hundred thousand years — the blink of an eye in cosmological terms. In that time, they throw out huge amounts of material in the form of a powerful stellar wind, hurling matter outwards at millions of kilometres per hour; Apep’s stellar winds were measured to travel at an astonishing 12 million km/h.

These stellar winds have created the elaborate plumes surrounding the triple star system — which consists of a binary star system and a companion single star bound together by gravity. Though only two star-like objects are visible in the image, the lower source is in fact an unresolved binary Wolf-Rayet star. This binary is responsible for sculpting the serpentine swirls surrounding Apep, which are formed in the wake of the colliding stellar winds from the two Wolf-Rayet stars.

Compared to the extraordinary speed of Apep’s winds, the dust pinwheel itself swirls outwards at a leisurely pace, “crawling” along at less than 2 million km/h. The wild discrepancy between the speed of Apep’s rapid stellar winds and that of the unhurried dust pinwheel is thought to result from one of the stars in the binary launching both a fast and a slow wind — in different directions.

This would imply that the star is undergoing near-critical rotation — that is, rotating so fast that it is nearly ripping itself apart. A Wolf-Rayet star with such rapid rotation is believed to produce a long-duration GRB when its core collapses at the end of its life.

Notes

[1] Callingham, now at the Netherlands Institute for Radio Astronomy (ASTRON), did part of this research while at the University of Sydney working with research team leader Peter Tuthill. In addition to observations from ESO telescopes, the team also used the Anglo-Australian Telescope at Siding Spring Observatory, Australia.


AAO Anglo Australian Telescope near Siding Spring, New South Wales, Australia, Altitude 1,100 m (3,600 ft)

Siding Spring Mountain with Anglo-Australian Telescope dome visible near centre of image at an altitude of 1,165 m (3,822 ft)

The team was composed of: J. R. Callingham (ASTRON, Dwingeloo, the Netherlands), P. G. Tuthill (Sydney Institute for Astronomy [SIfA], University of Sydney, Australia), B. J. S. Pope (SIfA; Center for Cosmology and Particle Physics, New York University, USA; NASA Sagan Fellow), P. M. Williams (Institute for Astronomy, University of Edinburgh, UK), P. A. Crowther (Department of Physics & Astronomy, University of Sheffield, UK), M. Edwards (SIfA), B. Norris (SIfA), and L. Kedziora-Chudczer (School of Physics, University of New South Wales, Australia).

See the full article here .


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ESO is the foremost intergovernmental astronomy organisation in Europe and the world’s most productive ground-based astronomical observatory by far. It is supported by 16 countries: Austria, Belgium, Brazil, the Czech Republic, Denmark, France, Finland, Germany, Italy, the Netherlands, Poland, Portugal, Spain, Sweden, Switzerland and the United Kingdom, along with the host state of Chile. ESO carries out an ambitious programme focused on the design, construction and operation of powerful ground-based observing facilities enabling astronomers to make important scientific discoveries. ESO also plays a leading role in promoting and organising cooperation in astronomical research. ESO operates three unique world-class observing sites in Chile: La Silla, Paranal and Chajnantor. At Paranal, ESO operates the Very Large Telescope, the world’s most advanced visible-light astronomical observatory and two survey telescopes. VISTA works in the infrared and is the world’s largest survey telescope and the VLT Survey Telescope is the largest telescope designed to exclusively survey the skies in visible light. ESO is a major partner in ALMA, the largest astronomical project in existence. And on Cerro Armazones, close to Paranal, ESO is building the 39-metre EEuropean Extremely Large Telescope, the E-ELT, which will become “the world’s biggest eye on the sky”.

ESO La Silla HELIOS (HARPS Experiment for Light Integrated Over the Sun)

ESO/HARPS at La Silla

ESO 3.6m telescope & HARPS at Cerro LaSilla, Chile, 600 km north of Santiago de Chile at an altitude of 2400 metres.

ESO 2.2 meter telescope at La Silla, 600 km north of Santiago de Chile at an altitude of 2400 metres.

ESO/Cerro LaSilla, 600 km north of Santiago de Chile at an altitude of 2400 metres.

ESO VLT Platform at Cerro Paranal elevation 2,635 m (8,645 ft)


ESO VLT 4 lasers on Yepun

Glistening against the awesome backdrop of the night sky above ESO_s Paranal Observatory, four laser beams project out into the darkness from Unit Telescope 4 UT4 of the VLT.

ESO/NTT at Cerro La Silla, Chile, at an altitude of 2400 metres



ESO/Vista Telescope at Cerro Paranal, with an elevation of 2,635 metres (8,645 ft) above sea level

ESO/NRAO/NAOJ ALMA Array in Chile in the Atacama at Chajnantor plateau, at 5,000 metres

ESO/E-ELT,to be on top of Cerro Armazones in the Atacama Desert of northern Chile. located at the summit of the mountain at an altitude of 3,060 metres (10,040 ft).

ESO/APEX high on the Chajnantor plateau in Chile’s Atacama region, at an altitude of over 4,800 m (15,700 ft)

Leiden MASCARA instrument, La Silla, located in the southern Atacama Desert 600 kilometres (370 mi) north of Santiago de Chile at an altitude of 2,400 metres (7,900 ft)

Leiden MASCARA cabinet at ESO Cerro la Silla located in the southern Atacama Desert 600 kilometres (370 mi) north of Santiago de Chile at an altitude of 2,400 metres (7,900 ft)

ESO Next Generation Transit Survey at Cerro Paranel, 2,635 metres (8,645 ft) above sea level

SPECULOOS four 1m-diameter robotic telescopes 2016 in the ESO Paranal Observatory, 2,635 metres (8,645 ft) above sea level

ESO TAROT telescope at Paranal, 2,635 metres (8,645 ft) above sea level

ESO ExTrA telescopes at Cerro LaSilla at an altitude of 2400 metres