Apertif discovers rare twinkling radio sources

Astronomers have discovered 11 new Intra-Hour Variable (IHV) sources, arguably among the rarest objects in the sky. IHVs are distant, compact radio sources whose radiation is made to twinkle on timescales of minutes, in a similar way as stars twinkle in the night sky. The cause is nearby Galactic plasma clouds that are in between the radio source and Earth. They offer a unique view of the very nearby interstellar medium.

The discovery was made using the Apertif (APERture Tile In Focus) observing system of the Westerbork Synthesis Radio Telescope (WSRT), operated by ASTRON in the Netherlands. This is the first imaging result of the Apertif survey that started in 2019 and will continue into next year.

Apertif, a technology pathfinder for the SKA, is a type of receiver called a phased array feed, which significantly expands WSRT’s field of view and survey speed, enabling new, innovative types of astronomical research.

For the last 30 to 40 years, no more than a handful of IHVs were discovered, but Apertif has found a further 11 in just one year. The researchers have described the finding of the first of these objects in the journal Astronomy & Astrophysics.

The search for these IHVs yielded an interesting find. The twinkling is caused by radio waves, emitted by these objects, traveling through plasma clouds situated somewhere between the IHVs and Earth.

Using Apertif, the scientists found that these plasma clouds are not uniformly spread across the galaxy, but are clustered, and that one is located extremely near to, or perhaps even within our own solar system.

“We think it lies more or less within the Oort Cloud,” says Prof. Tom Oosterloo, senior scientist at ASTRON and first author of the paper.

If that is indeed the case, that would be a find of great scientific significance. It could point to a new component in our solar system, possibly tied to its origin.

“Combining these findings with observations from the Karl G. Jansky Very Large Array radio telescope in New Mexico (USA), we can learn more about the properties of these plasma clouds,” Prof. Oosterloo explains.

Schematic of radio waves from a quasar traveling through a plasma cloud and arriving at Apertif.

ASTRON/Studio Eigen Merk

Source: ASTRON