July 8, 2014
Outburst From Second Brightest Star Modeled In Three Dimensions
[ Watch the Video: Creating The First 3d Model Of Eta Carinae Nebula ]
Gerard LeBlond for redOrbit.com - Your Universe Online
The study team consisted of Thomas Madura from NASA’s Goddard Space Flight Center in Greenbelt, Maryland; lead researcher Wolfgang Steffen from the National Autonomous University of Mexico; astronomer Jose Groh from Geneva University in Switzerland; and co-author Theodore Gull also from Goddard.
“Our model indicates that this vast shell of gas and dust has a more complex origin than is generally assumed. For the first time, we see evidence suggesting that intense interactions between the stars in the central binary played a significant role in sculpting the nebula we see today," Madura said.
In the southern constellation of Carina lies the star Eta Carinae. It is about 7,500 light-years away and one of the most massive binary systems. The smallest star in the system is about 30 times the mass of our sun and as much as one million times as luminous. The primary star emits five million times the energy as our sun and is about 90 times the mass. These two stars are destined to end their lives in massive supernova explosions.
Sometime between 1838 and 1845, Eta Carinae briefly outshone Canopus, which is the second brightest star in Carina. Astronomers are calling this event the “Great Eruption” in which a gaseous shell was emitted that held as much as 40 times the sun’s mass and blasted into space. The material formed a dust-filled cloud known as the Homunculus Nebula and is now about a light-year across and still expanding at about 1.3 million miles per hour.
In 2012, the team took near-infrared images of the nebula and used the information to produce a 3D model of the Homunculus Nebula. The model is published by the journal Monthly Notices of the Royal Astronomical Society.
“Our next step was to process all of this using 3-D modeling software I developed in collaboration with Nico Koning from the University of Calgary in Canada. The program is simply called 'Shape,' and it analyzes and models the three-dimensional motions and structure of nebulae in a way that can be compared directly with observations,” said Steffen.
The twin-lobed model confirms features from previous studies, including the holes located on the end of each lobe and the lack of molecular hydrogen emission from a dust skirt. New features include arm-like protrusions from each lobe located near the dust skirt and deep trenches along each lobe with irregular indentations on the side away from the Earth.
“One of the questions we set out to answer with this study is whether the Homunculus contains any imprint of the star's binary nature, since previous efforts to explain its shape have assumed that both lobes were more or less identical and symmetric around their long axis. The new features strongly suggest that interactions between Eta Carinae's stars helped mold the Homunculus,” said Groh.
Every 5.5 years the orbits of two stars are as close as the average distance from Mars to the sun, called periastron. These stars both create stellar winds of gaseous outflows that constantly interact, but are most impressive when the orbits are in periastron. The smaller star’s wind is faster creating a tunnel through the slower wind of the larger star. This closely matches the length and angles between the arm-like protrusions, suggesting that the Homunculus is continuing an impression from the “Great Eruption.”
After the model was created, it was converted into a format that could be used by 3D printers and the file was made available with the published paper.
“Now anyone with access to a 3-D printer can produce their own version of this incredible object. While 3-D-printed models will make a terrific visualization tool for anyone interested in astronomy, I see them as particularly valuable for the blind, who now will be able to compare embossed astronomical images with a scientifically accurate representation of the real thing,” said Gull.