“And no one showed us to the land
And no one knows the where’s or why’s
But something stirs and something tries
And starts to climb towards the light” -
Pink Floyd, Echoes

Image credit: NASA and The Hubble Heritage Team (STScI/AURA); Acknowledgment: R. Fesen (Dartmouth) and J. Morse (Univ. of Colorado).
Image credit: NASA, ESA, and the Hubble Heritage (STScI/AURA)-ESA/Hubble Collaboration; Acknowledgment: R. Fesen (Dartmouth College) and J. Long (ESA/Hubble).
Image credit: NASA, ESA, and the Hubble Heritage (STScI/AURA)-ESA/Hubble Collaboration; Acknowledgment: R. Fesen (Dartmouth College) and J. Long (ESA/Hubble).
Image credit: NASA, ESA, and the Hubble Heritage (STScI/AURA)-ESA/Hubble Collaboration; Acknowledgment: R. Fesen (Dartmouth College) and J. Long (ESA/Hubble).
Image credit: NASA, ESA, and the Hubble Heritage (STScI/AURA)-ESA/Hubble Collaboration; Acknowledgment: R. Fesen (Dartmouth College) and J. Long (ESA/Hubble).
Image credit: NASA, ESA, and the Hubble Heritage (STScI/AURA)-ESA/Hubble Collaboration; Acknowledgment: R. Fesen (Dartmouth College) and J. Long (ESA/Hubble).
Image credit: NASA/JPL-Caltech/L. Rudnick (University of Minnesota).
Image credit: NASA/CXC/SAO, via http://chandra.harvard.edu/photo/2013/casa/.
Image credit: NASA/JPL-Caltech/STScI/CXC/SAO, via http://www.nasa.gov/centers/goddard/news/topstory/2008/spitzer_infrared.html.

In 1947, a radio source towards the center of our galaxy was discovered: the strongest outside of the Solar System, Cassiopeia A. What caused it? A supernova dating back to the 17th century — the most recent one in our galaxy — with a massive black hole left behind. 11,000 light years distant, it was invisible from Earth due to its location in the galactic plane. Today, NASA’s great observatories, including Hubble (visible/near-IR), Chandra (X-ray) and Spitzer (infrared) have combined to showcase the fascinating, knotted structure of this ~340 year old stellar remnant.

Rich in not only elements like magnesium, phosphorous, silicon, sulphur, neon and argon, but in molecules like carbon monoxide, aluminum oxide and silicon dioxide, Cas A retains the onion-like structure of segregated elements that ultra-massive stars possess in their final stages. While the ejecta expand at speeds of 6,000 km/s up to 14,500 km/s (2–5% the speed of light), the gas-rich environment reflects the explosion’s light back towards us: a light-echo. Despite not seeing it until ~340 years later, we’ve determined the origin of the rare, Type IIb supernova itself: a red supergiant stripped of almost all of its hydrogen.


Mostly Mute Monday tells the story of a single object or phenomenon in images, videos and no more than 200 words.

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Starts With A Bang!

The Universe is out there, waiting for you to discover it.

Ethan Siegel

Written by

The Universe is: Expanding, cooling, and dark. It starts with a bang! #Cosmology Science writer, astrophysicist, science communicator & NASA columnist.

Starts With A Bang!

The Universe is out there, waiting for you to discover it.

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