Cassiopeia A Comes Alive in 3-D Movies

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Want to know what it’s like to fly through a supernova remnant? Then, THIS, you have to see. You’ll be able to experience SNR Cassiopeia A (Cas A) as never before, and see it across both time and space. Another time lapse animation shows the remnant’s expansion and changes over time, and still another provides a 3-D model of Cas A. Almost ten years ago, Chandra’s “First Light” image of Cas A revealed previously unseen structures and detail, and now, after eight years of observation, scientists have been able to construct these incredible animations which were presented at today’s American Astronomical Society meeting in Long Beach, California.

The fly-through movie is based on data from Chandra, NASA’s Spitzer Space Telescope, and ground-based optical telescopes. “We have always wanted to know how the pieces we see in two dimensions fit together with each other in real life,” said Tracey Delaney of the Massachusetts Institute of Technology. “Now we can see for ourselves with this ‘hologram’ of supernova debris.”

Delaney said there are two components to the explosion, a spherical component from the outer layers of the star and a flattened component from the inner layers of the star. Most intriguing, said Delaney is that the jets of the explosion are not all over the place but came out of the same plane in the supernova. Plumes, or jets, of silicon appear in the northeast and southwest, while plumes of iron are seen in the southeast and north. Astronomers had known about the plumes and jets before, but did not know that they all came out in a broad, disk-like structure.

The time-lapse animation tracks the remnant’s expansion and changes over time, measuring the expansion velocity of features in Cas A. “With Chandra, we have watched Cas A over a relatively small amount of its life, but so far the show has been amazing,” said Daniel Patnaude of the Smithsonian Astrophysical Observatory in Cambridge, Mass. “And, we can use this to learn more about the aftermath of the star’s explosion.”

Using estimates of the properties of the supernova explosion, including its energy and dynamics, Patnaude’s group show that about 30% of the energy in this supernova has gone into accelerating cosmic rays, energetic particles that are generated, in part, by supernova remnants and constantly bombard the Earth’s atmosphere. The flickering in the movie provides valuable new information about where the acceleration of these particles occurs.

The researchers found the expansion is slower than expected based on current theoretical models. Patnaude thinks the explanation for this mysterious loss of energy is cosmic ray acceleration.

The 3-D model of Cas A was made possible through a collaboration with the Astronomical Medicine project based at Harvard. The goal of this project is to bring together the best techniques from two very different fields, astronomy and medical imaging.

“Right now, we are focusing on improving three-dimensional visualization in both astronomy and medicine,”said Harvard’s Alyssa Goodman who heads the Astronomical Medicine project. “This project with Cas A is exactly what we have hoped would come out of it.”

3-D visualization and the 3-D expansion model provide researchers with a unique ability to study this remnant. The implication of this work is that astronomers who build models of supernova explosions must now consider that the outer layers of the star come off spherically, but the inner layers come out more disk like with high-velocity jets in multiple directions.

Cassiopeia A is the remains of a star thought to have exploded about 330 years ago, and is one of the youngest remnants in the Milky Way galaxy. The study of Cas A and remnants like it help astronomers better understand how the explosions that generate them seed interstellar gas with heavy elements, heat it with the energy of their radiation, and trigger blast waves from which new stars form.

Source: Chandra site