Gamma-rays detected by Fermi's LAT show that the remnant of Tycho's supernova shines in the highest-energy form of light. 

This portrait of the shattered star includes gamma rays (magenta), X-rays (yellow, green, and blue), infrared (red) and optical data. (Credit: Gamma ray, NASA/DOE/Fermi LAT Collaboration; X-ray, NASA/CXC/SAO; Infrared, NASA/JPL-Caltech; Optical, MPIA, Calar Alto, O. Krause et al. and DSS).

In early November 1572, observers on Earth witnessed the appearance of a "new star" in the constellation Cassiopeia, an event now recognised as the brightest naked-eye supernova in more than 400 years.

It's often called "Tycho's supernova" after the great Danish astronomer Tycho Brahe, who gained renown for his extensive study of the object.

Now, years of data collected by NASA's Fermi Gamma-Ray Space Telescope reveal that the shattered star's remains shine in high-energy gamma rays.

The detection gives astronomers another clue in understanding the origin of cosmic rays, subatomic particles - mainly protons - that move through space at nearly the speed of light.

Exactly where and how these particles attain such incredible energies has been a long-standing mystery because charged particles speeding through the galaxy are easily deflected by interstellar magnetic fields. This makes it impossible to track cosmic rays back to their sources.

"Fortunately, high-energy gamma rays are produced when cosmic rays strike interstellar gas and starlight. These gamma rays come to Fermi straight from their sources," said Francesco Giordano at the University of Bari and the National Institute of Nuclear Physics in Italy. He is the lead author of a paper describing the findings in the Dec. 7 edition of The Astrophysical Journal Letters.

Better understanding the origins of cosmic rays is one of Fermi's key goals. Its Large Area Telescope (LAT) scans the entire sky every three hours, gradually building up an ever-deeper view of the gamma-ray sky. Because gamma rays are the most energetic and penetrating form of light, they serve as signposts for the particle acceleration that gives rise to cosmic rays.

"This detection gives us another piece of evidence supporting the notion that supernova remnants can accelerate cosmic rays," said co-author Stefan Funk, an astrophysicist at the Kavli Institute for Particle Astrophysics and Cosmology (KIPAC), jointly located at SLAC National Accelerator Laboratory and Stanford University, Calif.

In 1949, physicist Enrico Fermi - the satellite's namesake - suggested that the highest-energy cosmic rays were accelerated in the magnetic fields of interstellar gas clouds. In the decades that followed, astronomers showed that supernova remnants may be the galaxy's best candidate sites for this process.

NASA WISE: Soul Nebula in the constellation Cassiopeia

This WISE mosaic is of the Soul Nebula (a.k.a. the Embryo Nebula, IC 1848, or W5).

It is an open cluster of stars surrounded by a cloud of dust and gas over 150 light-years across and located about 6,500 light-years from Earth in the constellation Cassiopeia, near the Heart Nebula (partially seen in the WISE image of Maffei 1 & 2).

The cluster of stars, IC 1848, formed about a million years ago from the material of the nebula. Winds and ultraviolet light from these young stars are excavating a cavity in the cloud.

Parts of the cloud that are more dense than their surroundings are being eroded more slowly and form giant towers, or pillars of dust and gas, which all point toward the central star cluster. It’s reminiscent of the landscape of Badlands National Park in South Dakota.

Material at the interior edges of the cavity is also being compressed by the winds and radiation from the star cluster. This triggers new star formation in those areas. The pillars inside the Soul Nebula are each about 10 light-years tall and have stars forming at their tips.

All four infrared detectors aboard WISE were used to make this image. Color is representational: blue and cyan represent infrared light at wavelengths of 3.4 and 4.6 microns, which is primarily light from stars. Green and red represent light at 12 and 22 microns, which is primarily emission from warm dust.

A note about astronomical names: Many objects in the sky have common names that astronomers will use to reference them. However, many, many more objects in the sky do not have common names and only their entry name in an astronomical catalogue is used.

One of the most prominent astronomical catalogues is the New General Catalogue (NGC) of Nebulae and Clusters of Stars. It was published in the 1880s. So an object with a name like NGC 7380 means that it is the 7,380th entry in the NGC.

Two additional catalogues were published as addendums to the NGC called the Index Catalogues (IC) between 1896 and 1905. The designation of IC 1848 for the Soul Nebula means that it is the 1,848th entry in the Index Catalogues of the NGC.

There are many catalogues of astronomical objects, each with their own purpose, and objects can be listed in more than one catalogue. For example, Dutch Astronomer Gart Westerhout made a catalogue of radio sources in the sky. Entry number five in the catalogue, W5, corresponds to IC 1848, i.e. the Soul Nebula (sometimes called the Embryo Nebula).

Image Credit: NASA/JPL-Caltech/WISE Team