Hubble Pinpoints Supernova Blast


The NASA/ESA Hubble Space Telescope has observed the supernova remnant named 1E 0102.2-7219. Researchers are using Hubble’s imagery of the remnant object to wind back the clock on the expanding remains of this exploded star in the hope of understanding the supernova event that caused it 1700 years ago.

The featured star that exploded long ago belongs to the Small Magellanic Cloud, a satellite galaxy of our Milky Way located roughly 200 000 light-years away. The doomed star left behind an expanding, gaseous corpse — a supernova remnant — known as 1E 0102.2-7219.

Because the gaseous knots in this supernova remnant are moving at different speeds and directions from the supernova explosion, those moving toward Earth are colored blue in this composition and the ones moving away are shown in red. This new Hubble image shows these ribbons of gas speeding away from the explosion site at an average speed of 3.2 million kilometers per hour. At that speed, you could travel to the Moon and back in 15 minutes.

Researchers have studied the Hubble archive looking for visible-light images of the supernova remnant and they have analysed the data to calculate a more accurate estimate of the age and centre of the supernova blast.

Hubble’s Distant View of the Supernova Remnant 1E 0102.2-7219 in 2006
In the wake of Independence Day festivities surrounding the U.S. July 4th holiday, astronomers and image processors at the Space Telescope Science Institute are releasing the Hubble Space Telescope image of a cosmic explosion that is quite similar to fireworks on Earth. In the nearby galaxy, the Small Magellanic Cloud, a massive star has exploded as a supernova, and begun to dissipate its interior into a spectacular display of colorful filaments. The supernova remnant (SNR), known as “E0102” for short, is the greenish-blue shell of debris just below the center of the Hubble image. Its name is derived from its cataloged placement (or coordinates) in the celestial sphere. More formally known as 1E0102.2-7219, it is located almost 50 light-years (15 parsecs) away from of the edge of the massive star-forming region, N 76, also known as Henize 1956 in the Small Magellanic Cloud. This delicate structure glowing a multitude of lavenders and peach hues, resides in the upper right of the image. The composition and thus, the coloring, of the diffuse remnant in comparison to its star-forming neighbor is due to the presence of very large quantities of oxygen compared to hydrogen. E0102 is a member of the oxygen-rich class of SNRs showing strong oxygen and other more metal-like abundances in its optical and X-ray spectra, and an absence of hydrogen and helium. N 76 in contrast is made up primarily of glowing hydrogen emission. One explanation for the abundance of oxygen in the SNR is that the parent star was very large and old, and had blown away most its hydrogen as stellar wind before it exploded. It is surmised that the progenitor star that caused the supernova explosion may have been a Wolf-Rayet. These stars, which can be upward of 20 times the mass of the sun and tens of thousands times more luminous, are famous for having a strong stellar wind throughout their lifetime. This stellar wind carried off material from the outer-most shells of the star (the hydrogen and helium shells), leaving the next most abundant element, oxygen, as a visible signature after the star exploded as a supernova. Determined to be only about 2000 years old, E0102 is relatively young on astronomical scales and is just beginning its interactions with the nearby interstellar medium. Young supernova remnants like E0102 allow astronomers to examine material from the cores of massive stars directly. This in turn gives insight on how stars form, their composition, and the chemical enrichment of the surrounding area. As well, young remnants are a great learning tool to better understand the physics of supernova explosions. E0102 was observed in 2003 with the Hubble Advanced Camera for Surveys. Four filters that isolate light from blue, visible, and infrared wavelengths and hydrogen emission were combined with oxygen emission images of the SNR taken with the Wide Field Planetary Camera 2 in 1995. The Small Magellanic Cloud is a nearby dwarf galaxy to our own Milky Way. It is visible in the Southern Hemisphere, in the direction of the constellation Tucana, and lies roughly 210,000 light-years (65 000 parsecs) distant. Credit: NASA, ESA and the Hubble Heritage Team (STScI/AURA)

According to their new estimates, light from this blast arrived at Earth 1700 years ago, during the decline of the Roman Empire. This supernova would only have been visible to inhabitants of Earth’s southern hemisphere. Unfortunately, there are no known records of this titanic event. Earlier studies proposed explosion dates of 2000 and 1000 years ago, but this new analysis is believed to be more robust.

To pinpoint when the explosion occurred, researchers studied the tadpole-shaped, oxygen-rich clumps of ejecta flung out by this supernova blast. Ionised oxygen is an excellent tracer because it glows brightest in visible light. By using Hubble’s powerful resolution to identify the 22 fastest moving ejecta clumps, or knots, the researchers determined that these targets were the least likely to have been slowed down by passage through interstellar material. They then traced the knots’ motion backward until the ejecta coalesced at one point, identifying the explosion site. Once that was known, they could calculate how long it took the speedy knots to travel from the explosion centre to their current location.

Hubble also measured the speed of a suspected neutron star — the crushed core of the doomed star — that was ejected from the blast. Based on the researchers’ estimates, itmust be moving at more than 3 million kilometres per hour from the centre of the explosion to have arrived at its current position. The suspected neutron star was identified in observations with the European Southern Observatory’s Very Large Telescope in Chile, in combination with data from NASA’s Chandra X-ray Observatory.

Journal Reference
  1. The Center of Expansion and Age of the Oxygen-rich Supernova Remnant 1E 0102.2-7219


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