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Astronomers now know that Tycho's new star was not new at all. Rather it signaled the death of a star in a supernova, an explosion so bright that it can outshine the light from an entire galaxy. This particular supernova was a Type Ia, which occurs when a white dwarf
star pulls material from, or merges with, a nearby companion star until
a violent explosion is triggered. The white dwarf star is obliterated,
sending its debris hurtling into space.
As with many supernova remnants,
the Tycho supernova remnant, as it's known today (or "Tycho," for
short), glows brightly in X-ray light because shock waves — similar to sonic booms
from supersonic aircraft — generated by the stellar explosion heat the
stellar debris up to millions of degrees. In its two decades of
operation, NASA's Chandra X-ray Observatory has captured unparalleled X-ray images of many supernova remnants.
Chandra reveals an intriguing pattern of bright clumps and fainter
areas in Tycho. What caused this thicket of knots in the aftermath of
this explosion? Did the explosion itself cause this clumpiness, or was
it something that happened afterward?
This latest image of Tycho from Chandra is providing clues. To
emphasize the clumps in the image and the three-dimensional nature of
Tycho, scientists selected two narrow ranges of X-ray energies to
isolate material (silicon, colored red) moving away from Earth, and
moving towards us (also silicon, colored blue). The other colors in the
image (yellow, green, blue-green, orange and purple) show a broad range
of different energies and elements, and a mixture of directions of
motion. In this new composite image, Chandra's X-ray data have been combined with an optical image of the stars in the same field of view from the Digitized Sky Survey.
By comparing the Chandra image of Tycho to two different computer
simulations, researchers were able to test their ideas against actual
data. One of the simulations began with clumpy debris from the
explosion. The other started with smooth debris from the explosion and
then the clumpiness appeared afterwards as the supernova remnant evolved
and tiny irregularities were magnified.
A statistical analysis using a technique that is sensitive to the
number and size of clumps and holes in images was then used. Comparing
results for the Chandra and simulated images, scientists found that the
Tycho supernova remnant strongly resembles a scenario in which the
clumps came from the explosion itself. While scientists are not sure
how, one possibility is that star's explosion had multiple ignition
points, like dynamite sticks being set off simultaneously in different
locations.
Understanding the details of how these stars explode is important
because it may improve the reliability of the use of Type Ia supernovas
"standard candles" — that is, objects with known inherent brightness,
which scientists can use to determine their distance. This is very
important for studying the expansion of the universe. These supernovae
also sprinkle elements such as iron and silicon, that are essential for
life as we know it, into the next generation of stars and planets.
A paper describing these results appeared in the July 10th, 2019 issue of The Astrophysical Journal and is available online.
The authors are Toshiki Sato (RIKEN in Saitama, Japan, and NASA's
Goddard Space Flight Center in Greenbelt, Maryland), John (Jack) Hughes
(Rutgers University in Piscataway, New Jersey), Brian Williams, (NASA's
Goddard Space Flight Center), and Mikio Morii (The Institute of
Statistical Mathematics in Tokyo, Japan).
3D printed model of Tycho's Supernova Remnant
Credit: RIKEN/G. Ferrand, et al & NASA/CXC/SAO/A. Jubett, N. Wolk & K. Arcand
Another team of astronomers, led by Gilles Ferrand of RIKEN in
Saitama, Japan, has constructed their own three-dimensional computer
models of a Type Ia supernova remnant as it changes with time. Their work
shows that initial asymmetries in the simulated supernova explosion are
required so that the model of the ensuing supernova remnant closely
resembles the Chandra image of Tycho, at a similar age. This conclusion
is similar to that made by Sato and his team.
A paper describing the results by Ferrand and co-authors appeared in
the June 1st, 2019 issue of The Astrophysical Journal and is available online.
NASA's Marshall Space Flight Center manages the Chandra program. The
Smithsonian Astrophysical Observatory's Chandra X-ray Center controls
science and flight operations from Cambridge, Massachusetts.
Fast Facts for Tycho's Supernova Remnant:
Scale: Image is about 12 arcmin (45 light years) across.
Category: Supernovas & Supernova Remnants
Coordinates (J2000): RA 00h 25m 17s | Dec +64° 08' 37"
Constellation: Cassiopeia
Observation Date: 14 pointings between Oct 1, 2001 & April 22, 2016
Observation Time: 336 hours 2 minutes (14 days 0 hours 2 minutes)
Obs. ID: 115, 3837, 7539, 8551, 10093-10097; 10902-10904; 10906, 15998
Instrument: ACIS
Also Known As: G120.1+01.4, SN 1572
References: Sato, T. et al. 2019, ApJ, 879, 64; arXiv:1903.00764
Color Code: X-ray Broadband: Red: 0.3-1.2 keV, Yellow: 1.2-1.6 keV, Cyan: 1.6-2.26 keV, Navy: 2.2-4.1 keV, Purple: 4.4-6.1 keV; X-ray Motion Shift Orange: 1.7666-1.7812 keV, Blue: 1.9564-1.971 keV; Optical: Red, Blue
Distance Estimate: About 13,000 light years
Source: NASA’s Chandra X-ray Observatory
