Rings and loops in the stars: Planck’s stunning new images

The new maps show regions of the sky that produce anomalous microwave emission.
By | Published: July 7, 2015 | Last updated on May 18, 2023
An image of the ring around the star Lambda Orionis, made with the ESA Planck satellite.
An image of the ring around the star Lambda Orionis, made with the ESA Planck satellite. The ring, here seen in pink, is around 200 light-years across. In the image, red represents the anomalous microwave emission (AME), green represents the emission from interstellar plasma, and the blue is emission arising from electrons moving in magnetic fields.
M. Peel/JCBA/Planck/ESA
A ring of dust 200 light-years across and a loop covering a third of the sky: two of the results in a new map from the Planck satellite. Mike Peel and Paddy Leahy of the Jodrell Bank Center for Astrophysics (JBCA) presented the images at the National Astronomy Meeting (NAM 2015) at Venue Cymru, Llandudno, Wales.

The European Space Agency’s (ESA) Planck satellite, launched in 2009 to study the ancient light of the Big Bang, has also given us maps of our Milky Way Galaxy in microwaves (radiation at centimeter to millimeter wavelengths). Microwaves are generated by electrons spiraling in the galaxy’s magnetic field at nearly the speed of light — the synchrotron process: by collisions in interstellar plasma, by thermal vibration of interstellar dust grains, and by “anomalous” microwave emission (AME), which may be from spinning dust grains.

A full sky map made using the ESA Planck satellite.
A full sky map made using the ESA Planck satellite. Loop 1, marked by the dashed ellipse, is the yellow feature above center, shading to purple, and the purple arc below center. The colors represent the angle of the magnetic field and the brightness represents the signal strength.
M. Peel/JCBA/Planck/ESA
The relative strength of these processes changes with wavelength and are separated using multiwavelength measurements from Planck, from NASA’s WMAP satellite, and from ground-based radio telescopes, giving maps of each component.

The new maps show regions covering huge areas of our sky that produce AME. This process, only discovered in 1997, could account for a large amount of galactic microwave emission with a wavelength near 0.4 inch (1 centimeter). One example where it is exceptionally bright is the 200-light-year-wide dust ring around the Lambda Orionis Nebula — the “head”’ of the familiar Orion constellation. This is the first time the ring has been seen in this way.

A wide-field map also shows synchrotron loops and spurs where charged particles spiral around magnetic fields, including the huge Loop 1 that was discovered more than 50 years ago. Remarkably, astronomers are still uncertain about its distance. It could be anywhere between 400 and 25,000 light-years away, and though it covers around a third of the sky, it is impossible to say exactly how big it is.