Somewhere in the Milky Way, a massive old star is about to die a spectacular death.
As its nuclear fuel runs out, the star begins to collapse under its own tremendous weight. Crushing pressure triggers new nuclear reactions,
setting the stage for a terrifying blast. And then... nothing happens.
At least that's what supercomputers have been telling astrophysicists for decades.
Many of the best computer models of supernovas fail to produce an explosion. At the end of the simulation, gravity wins the day and the star simply collapses.
Clearly, physicists are missing something.
"We don't fully understand how supernovas of massive stars work yet," says Fiona Harrison, an astrophysicist at the California Institute of Technology.
To figure out what’s going on, Harrison and colleagues would like to examine the inside of a real supernova while it's exploding.
That's not possible, so they're doing the next best thing.
Launched over the Pacific Ocean on June 13, 2012, by a Pegasus XL rocket, NuSTAR is the first space telescope that can focus very
high-energy X-rays, producing images roughly 100 times sharper than those possible with previous high-energy X-ray telescopes.
When NuSTAR finishes its check-out and becomes fully operational, scientists will use it to scan supernovas for clues etched into the pattern of elements
spread throughout the explosion's debris.
"The distribution of the material in a supernova remnant tells you a lot about the original explosion,” says Harrison.
An element of particular interest is titanium-44. Creating this isotope of titanium through nuclear fusion requires a certain combination of energy,
pressure, and raw materials.
Inside the collapsing star, that combination occurs at a depth that's very special.
Everything below that depth succumbs to gravity and collapses inward to form a black hole.
Everything above that depth will be blown outward in the explosion. Titanium-44 is created right at the cusp.
So the pattern of how titanium-44 is spread throughout a supernova remnant can reveal a lot about what happened at that crucial threshold during the
explosion. And with that information, scientists might be able to figure out what's wrong with their computer simulations.
A supercomputer model of a spinning core-collapse supernova.
NuSTAR observations of actual supernova remnants will provide vital data for such models. Credit: Fiona Harrison
Some scientists believe the computer models are too symmetrical. Until recently, even with powerful supercomputers, scientists have
only been able to simulate a one-dimensional sliver of the star. Scientists just assume that the rest of the star behaves similarly, making the simulated implosion the same in all radial directions.
But what if that assumption is wrong?
"Asymmetries could be the key," Harrison says. In an asymmetrical collapse, outward forces could break through in some places even
if the crush of gravity is overpowering in others. Indeed, more recent, two-dimensional simulations suggest that asymmetries could help solve the mystery of the "non-exploding supernova."
If NuSTAR finds that titanium-44 is spread unevenly, it would be evidence that the explosions themselves were also asymmetrical, Harrison explains.
Cassiopeia A Light Echoes in Infrared Credit: O. Krause (Steward Obs.) et al., SSC, JPL, Caltech, NASA
To detect titanium-44, NuSTAR needs to be able to focus very high energy X-rays. Titanium-44 is radioactive, and when it decays
it releases photons with an energy of 68 thousand electron volts. Existing X-ray space telescopes, such as
NASA's Chandra X-Ray Observatory, can focus X-rays only up to about 15 thousand electron volts.
Normal lenses can't focus X-rays at all. Glass bends X-rays only a miniscule amount—not enough to form an image.
X-ray telescopes use an entirely different kind of "lens" consisting of many concentric shells. They look a bit like the layers
of a cylindrical onion.
Incoming X-rays pass between these layers, which guide the X-rays to the focal surface. It's not a lens, strictly speaking,
because the X-rays reflect off the surfaces of the shells instead of passing through them, but the end result is the same.
The NuSTAR team has spent years perfecting delicate manufacturing techniques required to make high-precision X-ray optics for
NuSTAR that work at energies as high as 79 thousand electron volts.
Their efforts could end up answering the question, "Why won't the supernova explode?"
Can Parallel Universes Explain The Déjà Vu Phenomenon?
Have you ever had a déjà vu experience? It's the feeling, or impression that you have already witnessed or experienced a current situation.
The term déjà vu is French and means, literally, "already seen."
It is a rather common, yet little understood phenomenon...
Earth-Like Alien Worlds Can Be Much Older Than Previously Expected
Building a terrestrial planet requires raw materials that weren't available in the early history of the universe.
The Big Bang filled space with hydrogen and helium. Chemical elements like silicon and oxygen - key components of rocks - had to be cooked up over time by stars.
But how long did that take? How many of such heavy elements do you need to form planets?
Spectacular Planetary System -
Alien Worlds Orbiting Closer Than Any Yet Discovered
One is a rocky planet 1.5 times the size of Earth. The other is a gaseous world nearly four times Earth's size.
Together they form a spectacular system in which two planets orbit closer to each other than any yet discovered.
"We've never known of planets like this...
If you were on the smaller planet looking up, the larger planet would seem more than twice the size of Earth's full moon. It would be jaw-dropping..."
Last Breaths Of Dying Star Captured
Last breaths of dying sun-like star have been captured by scientists using NASA's Stratospheric Observatory for Infrared Astronomy (SOFIA).
The object observed by SOFIA, planetary nebula Minkowski 2-9, or M2-9 for short, is seen in this three-color composite image.
The SOFIA observations were made at the mid-infrared wavelengths of 20, 24, and 37 microns.
Though the universe is filled with billions upon billions of stars, the discovery of a single variable star in 1923 altered the
course of modern astronomy. And, at least one famous astronomer of the time lamented that the discovery had shattered his world view.