Using a 3D printer to make key fobs and automatic pistols is old hat. The latest thing is a 3D-printed model stellar nebulae. Using new telescopic observations, NASA has created a 3D model of the Homunculus Nebula that isn't just a string of mathematical equations, but a printable plan for a physical representation of an exploding star system. It’s intended to give astronomers a better understanding of the nature of the stars, but can also be downloaded and printed out by the public using a 3D printer.

The Homunculus Nebula surrounds the Eta Carinae star system, located in the southern constellation of Carina about 7,500 light-years from Earth. It was first cataloged in 1677, and is known as a variable star that changes its brightness dramatically over the course of decades. Between the years 1838 and 1845, the star system grew in brightness in what astronomers call a "supernova impostor" as gases amounting to between 10 and 40 times the mass of the Sun blasted into space, forming the Homunculus Nebula that surrounds the star system. Seen from Earth, Eta Carinae was brighter than Canopus, and the episode is called the Great Expansion by astronomers.


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Despite this long and prominent history, Eta Carinae was only discovered to be a binary in 2005. In fact, it’s one of the most massive binary star systems that is available for study by astronomers. It consists of two stars – a primary that is 90 times more massive than the Sun and generates five million times as much energy, and a smaller one that has is 30 times as massive as the Sun and is a million times as luminous. These stars are so heavy that instead of one day burning out, they will each end as exploding supernovae.

Now NASA has created a new computer model of the Homunculus Nebula that has the added advantage anyone with access to a 3D printer can turn it into solid form. The space agency used new observations from the European Southern Observatory's Very Large Telescope and its X-Shooter spectrograph taken over the course of two nights in March 2012. Images were taken using near-infrared, visible and ultraviolet wavelengths, producing what NASA says is the most complete spectral map to date.

Once the observations were recorded, calculations were made based on a single molecular hydrogen gas emission line of near-infrared light. This wavelength shifts slightly with the speed and direction of the gas, which allowed the team to see areas masked by dust or on the side of the nebula away from Earth.

With these calculations, NASA created the first high-resolution, fully 3D model of the Homunculus Nebula. It was produced by feeding the observation data into a computer program called Shape, which was designed by NASA and the University of Calgary. The program turned the data into a 3D model while allowing the scientists to compare it directly with the observations. This also formed the basis for further research.

"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," says team member Jose Groh, an astronomer at Geneva University in Switzerland. "The new features strongly suggest that interactions between Eta Carinae's stars helped mold the Homunculus."

Far from being a neat hourglass shape formed by a pair of expanding gas jets, the nebula is marked by protrusions, trenches and holes gouged in the surface, and the expected dust skirt in the center of the nebula was absent. Also, the model showed how the nebula is shaped by the two stars that make up the system as they approach each other at their closest every 5.5 years, which brings them to a distance equivalent to that of the Sun and Mars.

As the stars approach, their stellar winds press against one another and, since those of the smaller star are faster, they carve into those of the larger star, which pressed and gouged at the nebula as it first expanded, forming trenches and protrusions that date back to the time of the Great Expansion.

Printable model

You can take make your own model of the Homunculus Nebula by downloading a zip file and using it with a 3D printer to make your own. It may not produce any cosmic insights, but it could be used as an interstellar desk ornament.

"Now anyone with access to a 3D printer can produce their own version of this incredible object," says Goddard astrophysicist Theodore Gull. "While 3D-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."

The team’s findings were published in the Monthly Notices of the Royal Astronomical Society.

The video below discusses the science behind the Eta Carinae model.

Source: NASA

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