Supernova Remnant in Technicolor

Take a look at this supernova remnant from radio waves to x-rays to see multiple features of its bubble-like expanding shock wave.

Supernova remnant in multiple wavelengths

This animated gif shows the supernova remnant, G352.7-0.1, in multiple wavelengths, including radio, infrared, visible, x-ray, and finally a composite image.
Radio: NRAO / VLA / Argentinian Institute of Radioastronomy / G.Dubner; Infrared: NASA / JPL-Caltech; Optical: DSS; X-ray: NASA / CXC / Morehead State Univ / T.Pannuti et al.

Supernovae — the dramatic explosions of massive stars ending their lives — can outshine their host galaxies for weeks, allowing them to be seen across millions of light-years of empty space. On a cosmic scale they’re pretty common; in the last couple of years amateur astronomers have been able to enjoy several of them in backyard scopes, such as the recent supernova in M82.

But we can only get a closer look at these enigmatic explosions when they happen in our Milky Way. (Unfortunately they likely occur only once or twice every century.) The remnants of these shattered stars remain long after the brilliant blast, providing beautiful waves of gas that astronomers can study thousands of years later.

The supernova remnant, G352.7–0.1, located 24,000 light-years away in the constellation Scorpius, is no exception. Data taken across a spectrum of wavelengths from an array of telescopes provide a unique peek into this supernova remnant’s past. Looking at the photons emitted across the spectrum of energies and wavelengths allows astronomers to understand the different physical processes at play. But let’s also take a look at what each wavelength range tells us.

Radio (in pink)

When a supernova explodes, the outer layers of the expanding material crash into nearby gas and dust, driving a tremendous shock wave. Electrons and other charged particles, accelerated in the rapidly expanding wave, emit a type of radio emission called synchrotron radiation. This shows up in the radio data taken by the Very Large Array.

Infrared (in orange)

The infrared emission, as seen by the Spitzer Space Telescope, is almost perfectly aligned with the radio emission. Its outline reveals the dust collected and warmed by the blast wave.

Visible (in white)

Don’t expect to see anything if you point your optical telescope toward this supernova remnant: it’s invisible in the visible. Why?

The optical light in a supernova remnant arises once the debris cools back down. So if something keeps the gas temperature elevated, the optical emission won’t form. The X-ray emission (described below) suggests this supernova remnant is dominated by extremely hot gas (about 30 million degrees Celsius).

Astronomers have also searched high and low for a neutron star, visible in the optical, but cannot find one. It may be too faint, or the supernova explosion may have left behind a black hole instead.

X-Ray (in blue)

Typically the expanding shock wave of a supernova explosion is hot enough to emit X-rays.

But G352.7–0.1 seems to be an exception to the rule. Here the high-energy X-ray emission (provided by NASA's Chandra X-Ray Observatory) fills in the center of the radio data, dominated by the hotter debris from the explosion rather than the surrounding material swept up by the expanding shock wave. While this helps to explain why the remnant is invisible in any visible wavelengths, astronomers remain unsure why it's still so hot thousands of years later.

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