A full sky map made using the ESA Planck
satellite. Loop 1, marked by the dashed ellipse, is the yellow feature
above centre, shading to purple, and the purple arc below centre. The
colours represent the angle of the magnetic field and the brightness
represents the signal strength.
Credit: 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. Dr Mike Peel and Dr Paddy Leahy of the Jodrell
Bank Centre for Astrophysics (JCBA) presented the images today at the
National Astronomy Meeting (NAM 2015) at Venue Cymru, Llandudno, Wales.
The European Space Agency (ESA) Planck satellite, launched in 2009 to
study the ancient light of the Big Bang, has also given us maps of our
own Galaxy, the Milky Way, in microwaves (radiation at cm- to
mm-wavelengths). Microwaves are generated by electrons spiralling 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.
The relative strength of these processes changes with wavelength, and
are separated using multi-wavelength 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 1 cm. 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, discovered more than 50 years ago. Remarkably, astronomers are
still very 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.
This research was supported by an ERC Starting (Consolidator) Grant (no. 307209) and STFC Consolidated Grant (no. ST/L000768/1).
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