Smallest Ever Odd Radio Circle Creates a New Mystery
This video covers Odd Radio Circles (ORCs), a mysterious class of radio-only astronomical structures discovered via the ASKAP EMU survey starting in 2019, and a new tiny ORC called GA1248+4826 found with the LOFAR LoTSS survey. ORCs are enormous ring-shaped radio emissions invisible in optical, infrared, X-ray, and gamma-ray light, and their origin is still debated among competing explanations involving black hole jets, galactic mergers, and starburst-driven winds. The newly found small ORC differs sharply from typical ORCs in size and structure, suggesting scientists may be undercounting smaller, more compact examples. The discoveries matter because they reveal previously unknown mechanisms shaping galaxy evolution and the intergalactic medium.
[00:47] The discovery of the smallest ORC to date is reshaping understanding of what these circles mean for galaxy evolution
- [01:15] The story starts with the 2019 EMU survey using the ASKAP radio telescope, which mapped radio observations in unprecedented detail
- [02:24] The circles show no infrared or optical emissions, so scientists initially suspected they were telescope artifacts before confirming them as real
- [04:07] Some ORCs are several times larger than the Milky Way galaxy
- [04:43] The radio emissions are produced by synchrotron radiation, created when fast-moving electrons spiral around magnetic field lines
+ 7 more takeaways
- [06:39] A new circle, GA1248+4826, was found using the LOFAR 2m Sky Survey and is described as an oddball even among ORCs
- [07:18] Its ring radius is only about 30 kpc (100,000 light years), roughly the size of the Milky Way and at least 10 times smaller than other known ORCs
- [07:33] Unlike classical ORCs where the host galaxy sits centered, this galaxy is offset, sitting on the edge of the ring
- [08:46] Proposed explanations include supermassive black hole jets viewed head-on, or a plasma relic left behind after jets shut off
- [09:22] An alternative explanation is a starburst-driven galactic wind from intense star formation about a billion years ago, creating a shockwave ring when it hits thin intergalactic gas
- [11:09] Analysis of GA1248+4826 excludes an active black hole, jets, or a supernova as the cause, pointing instead to ancient plasma re-energized by merging galaxies in the group
- [13:34] Out of millions of surveyed galaxies, only about 30 ORCs have been confirmed so far