The ghostly lights from two dead stars have stories to tell.

Cosmic Hand

A purple skeletal hand reaches for an oval of pumpkin-colored blobs
The pulsar wind nebula known as MSH 15-52, or "the Hand" was imaged at X-ray frequencies by the Chandra X-ray Observatory and the Imaging X-ray Polarimetry Explorer (white and purple) as well as at infrared wavelengths by the Dark Energy Camera (orange)
X-ray: NASA / CXC / Stanford Univ. / R. Romani et al. (Chandra); NASA / MSFC (IXPE); Infared: NASA / JPL-Caltech / DECaPS; Image Processing: NASA / CXC / SAO / J. Schmidt

Is this skeletal hand grasping for something in space? Well no, but in reality it’s something just as creepy — the vapors of a dead star.

Known to astronomers as a pulsar wind nebula, the miasma of charged particles highlighted in this image come from the collapsed stellar core at the cloud’s center. That pulsar’s strong magnetic fields accelerate escaping particles to extremely high energies — up to tens of trillions of electron-volts, even faster than the fastest particles in the Large Hadron Collider.

As electrons and their antimatter counterparts, positrons, spiral around the embedded magnetic fields, they release X-rays in what’s called synchrotron radiation. The ordered magnetic fields orient the X-ray light, polarizing it, but the effect is difficult to detect. For the first time in a long time, NASA’s Imaging X-ray Polarimetry Explorer (IXPE) is giving astronomers a view of this type of information from the universe.

Where X-ray polarization is weak in this image, it’s because the magnetic fields are jumbled by turbulence. But where the magnetic fields are ordered, they imprint a strong polarization signature on the X-rays. That signature is quite strong — in some regions, it nears the theoretical limit. One example is in the jet that streams downward from the pulsar at the center of the “palm” toward the “wrist.” While the polarization at the base of the jet is weak, it becomes strong further down the jet, which the magnetic fields have lined up.

Sticks show weaker polarization at the center of the "palm," near the pulsar, and stronger polarization toward the "wrist" of the hand
In this image, X-ray polarization is shown using "sticks." In areas where the stick is short, the polarization is small due to turbulence that mixes up the fields. In regions with more ordered fields, polarization is stronger and the sticks are longer.
X-ray: NASA / CXC / Stanford Univ. / R. Romani et al. (Chandra); NASA / MSFC (IXPE); Infared: NASA / JPL-Caltech / DECaPS; Image Processing: NASA / CXC / SAO / J. Schmidt

“The IXPE data gives us the first map of the magnetic field in the ‘hand’,” said Roger Romani (Stanford University), who led the study. “The charged particles producing the X-rays travel along the magnetic field, determining the basic shape of the nebula, like the bones do in a person’s hand.”

This is the first time the bones of this particular skeleton have been revealed, though IXPE has imaged other pulsar wind nebulae and found similarly high levels of polarization. Studies of these types of objects help astronomers learn about the origin of some of the most energetic particles in the universe.

Read more in NASA’s press release and in the study just published in the Astrophysical Journal.

Creepy Crab

Though its name is less creepy, the Crab Nebula created by the pulsar at its core is no less ghostly, especially in light of this new image from the James Webb Space Telescope (JWST).

Crab Nebula with infrared light adding new details
Webb’s NIRCam (Near-Infrared Camera) and MIRI (Mid-Infrared Instrument) have revealed new details in the Crab Nebula. e remnant appears comprised of a crisp, cage-like structure of fluffy red-orange filaments of gas that trace doubly ionized sulfur (sulfur III). Among the remnant’s interior, yellow-white and green fluffy ridges form large-scale loop-like structures, which represent areas where dust particles reside. Within the nebula is the white light of synchrotron radiation, here imaged at infrared wavelengths.
NASA / ESA / CSA / STScI / Tea Temim (Princeton University)

While at first glance the image seems similar to the one the Hubble Space Telescope took in visible light in 2005, the devil’s in the details. The cage-like structure of gaseous filaments is the same, but JWST maps out the yellow and green tendrils of dust within for the first time. Infrared light also highlights the ghoulish glow of synchrotron radiation that comes from the spiraling electrons around the pulsar at center. (There's no polarization data to shed light on the magnetic field, however.)

A team led by Tea Temim (Princeton University) led the observations in a search for answers about the Crab Nebula’s origins. That work is ongoing.

Read more about the observations in the JWST press release. Additional information on the motivation for the observations is available in the proposal for time on JWST.




Image of Anthony-Mallama


November 1, 2023 at 10:12 am

I enjoyed reading this interesting account of two dead stars, and it was perfectly timed for Halloween!
The Crab Nebula has an amazing history all by itself. The supernova that created the nebula was seen in 1054 by Chinese and Japanese observers. The ‘new star’ was so bright it could be observed in daylight. The nebula was first identified in the eighteenth century and it was connected with the supernova event about 200 years later. Then in the 1960s the pulsar was discovered. Now we have these wonderful new findings made from space.
Best of all, the Crab is easy to see in a small telescope. Fall and winter are the best times to observe it.

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