Star burst in 3D

New recording technique reveals asymmetry of star explosion SN1987A

SN 1987A: This reconstruction shows the two outer rings and the deformed inner area. ESO / L. Calada
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For the first time, astronomers reconstructed the matter distribution three-dimensionally during a star explosion. The image of the Supernova 1987A obtained with ESO's Very Large Telescope reveals very asymmetrically ejected material - a sign that the explosion must have been very turbulent, astronomers report in the journal "Astronomy and Astrophysics".

Unlike the sun, which will die a comparatively unspectacular death, a massive star explodes at the end of its short life in the form of a supernova, a massive star burst. Large quantities of matter are thrown outwards. Among the stellar explosions observed so far, the Supernova 1987A occupies a special position in the Large Magellanic Cloud: in 1987, it was the first supernova of the modern era that could be seen with the naked eye. Because of their relatively short distance, astronomers were able to investigate the explosion of a massive star and its effects in more detail than ever before.

First three-dimensional image of SN 1987A

Based on new observations with the SINFONI instrument (Spectrograph for Integral Field Observations in the Near Infrared) at ESO's Very Large Telescope (VLT), the knowledge of SN 1987A could be further enhanced: the spectrograph SINFONI detects the near-infrared wavelength range and makes it possible An additional module for adaptive optics, using the Doppler shift of the spectral lines to investigate the velocity of the material ejections spatially resolved in different areas of the supernova remnant. Calculating the velocities back to the point of explosion, the result is the three-dimensional structure of the spreading cloud of matter.

"We have determined the distribution of velocities in the innermost material ejections of the supernova 1987A, " explains Karina Kjær, the head of the scientists' team. "Exactly how a supernova explosion comes about is still not well understood, but the way the star exploded can be read from the innermost reaches of the explosion cloud."

SNC Hubble Space Telescope Image © NASA / ESA / Harvard-Smithsonian Center for Astrophysics

Material output asymmetric

Among other things, the new data reveal that the explosion was stronger and faster in some directions than in others. "We can see that the matter was not ejected evenly in all directions. Instead, there seems to be a bias that is different from what you would expect from the ring's position

This resulted in an irregular shape, through which some parts of the explosion cloud extend further into the room, says Kj r.

The material exploded in the explosion moved out at an incredible 100 million kilometers per hour, corresponding to about one tenth of the speed of light or one hundred thousand times the speed of a passenger plane. But even at this breakneck speed, it took ten years for the material to reach a ring of gas and dust ejected by the dying star before the explosion. The images also document another matter wave, which propagates at one-tenth of the said speed. It is heated up by radioactive elements generated during the explosion.

The asymmetric behavior of matter in the supernova has already been predicted by some recent computer models of supernova explosions. These models gave rise to great instability during the explosion. The new observations therefore provide the first direct confirmation of these models.

Only possible thanks to integral field spectroscopy

In order to enable the results that have now been published, the performance, in particular the spatial resolution of the SINFONI instrument, was absolutely necessary. It contains, on the one hand, a sophisticated system of adaptive optics, which counteracts the fuzziness caused by the earth's atmosphere. On the other hand, the instrument uses the technique of integral field spectroscopy to generate spatially resolved spectra. For example, astronomers can simultaneously examine different areas of the chaotic central area of ​​the supernova, which is a prerequisite for the now generated 3D view.

"Integral field spectroscopy is a special technique that allows us to extract information about the nature of the gas and its velocities from every pixel of the image, " adds Kj r. In addition to the normal image, for each point in the image, we also measure the speed along the line of sight toward or away from us. As the material spreads out unhindered and we know how much time has passed since the explosion, we can translate these velocities into distances to the center of explosion. So we see the ejected material once from the side and once from the front

(ESO, 05.08.2010 - NPO)