Astronomers using ESO’s Very Large Telescope Interferometer (VLTI) in Chile have snapped the most detailed image ever of the Eta Carinae stellar system.
This mosaic shows the Carina Nebula (left part of the image), home of the Eta Carinae stellar system. This part was observed with the MPG/ESO 2.2-m telescope at ESO’s La Silla Observatory. The middle part shows the direct surrounding of the star system: the Homunculus Nebula, created by the ejected material from the Eta Carinae system. This image was taken with ESO’s Very Large Telescope. The right image shows the innermost part of the system as seen with ESO’s Very Large Telescope Interferometer/ It is the highest resolution image of Eta Carinae ever. Image credit: Gerd Weigelt / ESO.
Eta Carinae is a binary star system approximately 7,500 light-years away in the constellation Carina.
This system was first cataloged by the English astronomer Edmond Halley in 1677, as a star of fourth magnitude.
Also known as HD 93308 and Hen 3-481, Eta Carinae is actually situated in the star-forming Carina Nebula (NGC 3372) and will probably end its life in a supernova explosion within the next few 100,000 years.
According to astronomers, the system consists of two massive stars orbiting each other and is very active, producing stellar winds which travel at velocities of up to 6.2 million mph (10 million km per hour).
The zone between the two stars where the winds from each collide is very turbulent, but until now it could not be studied.
The power of Eta Carinae stellar components creates dramatic phenomena. A so-called ‘Great Eruption’ in the system was observed by astronomers in the 1830s.
Scientists now know that this was caused by the larger star of the pair expelling huge amounts of gas and dust in a short amount of time, which led to the distinctive lobes, known as the Homunculus Nebula.
The combined effect of the two stellar winds as they smash into each other at extreme speeds is to create temperatures of millions of degrees and intense deluges of X-ray radiation.
The central area where the winds collide is so comparatively tiny — a thousand times smaller than the Homunculus Nebula — that telescopes in space and on the ground so far have not been able to image them in detail.
An international team of astronomers led by Dr. Gerd Weigelt from the Max Planck Institute for Radio Astronomy in Germany have now utilized the powerful resolving ability of VLTI’s AMBER instrument to peer into this violent realm for the first time.
The new image clearly depicts the structure which exists between the two Eta Carinae stars.
An unexpected fan-shaped structure was observed where the raging wind from the smaller, hotter star crashes into the denser wind from the larger one.
“Our dreams came true, because we can now get extremely sharp images in the infrared,” Dr. Weigelt said.
“The VLTI provides us with a unique opportunity to improve our physical understanding of Eta Carinae and many other key objects.”
In addition to the imaging, the spectral observations of the collision zone made it possible to measure the velocities of the intense stellar winds.
Using these velocities, Dr. Weigelt and co-authors were able to produce more accurate computer models of the internal structure of Eta Carinae, which will help increase our understanding of how these kind of extremely high mass stars lose mass as they evolve.
The team’s findings were published online September 9, 2016 in the journal Astronomy & Astrophysics.
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G. Weigelt et al. VLTI-AMBER velocity-resolved aperture-synthesis imaging of Eta Carinae with a spectral resolution of 12 000. Studies of the primary star wind and innermost wind-wind collision zone. A&A, published online September 9, 2016; doi: 10.1051/0004-6361/201628832
