Category Archives: radio astronomy

astronomy, radio astronomy

The Radio Sky Through Human Eyes

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Check out the MWA Sky

The sky as seen by MWA
Title screen from a video about MWA.

Interested in the radio sky at low frequencies?  Then,check out the Murchison Wide-field Array (MWA). A few years ago, we worked on a video about the MWA, located in the outback of Western Australia. The video was created for the MIT Haystack Observatory, which was involved with the project. We interviewed Colin Lonsdale, who is director of Haystack, and created a short explainer about the observatory.  It was a fun project and I’ve kept tabs on the MWA’s progress ever since.

A Sky in Radio Technicolor

radio sky
The MWA sky, as seen by the GLEAM survey.

Recently the folks who run MWA released an image from a sky survey they’ve made called GLEAM (which stands for GaLactic and Extragalactic All-sky MWA). The combined MWA receivers scanned the sky at frequencies between 70 and 230 MHz. These are very low-frequency waves that can be easily disrupted by TV and radio signals (among others). So, MWA is located literally in the middle of nowhere with a fine view of the sky.  In the image they released, red denotes the lowest frequencies received, green is the middle of the range, and blue indicates the highest ones. This is what gives the image its ‘technicolor’ look. That works for our eyes, which can only see three primary colors.  MWA actually detects more than 20 colors.

What Does MWA “See”?

Among the objects that MWA can detect in its frequency bands are ancient supernova explosions and emissions from distant black holes. They are just a few of the types of celestial sites that lie in the 24,402 square degrees of sky that the MWA covered in the survey. In that region, there are more than 307,000 radio sources.   If you’re interested in the full paper from the survey team, it’s available here and gives all the details about the survey and data reduction.

MWA’s survey is part of the path to the final deployment of the low-frequency part of the Square Kilometre Array. Once built out, SKA will build on MWA’s work, further defining and refining the radio sky at radio frequencies well below what other arrays are detecting. In particular, the work will help astronomers dig further into the distant, early universe.  That’s still a largely unstudied realm of the cosmos, and astronomers are anxious to learn more about what happened way back then.

 

astronomy, Orion, planet-forming scenarios, planetary science, radio astronomy, star formation

Orion’s Pebbled Pathway to Stars and Planets

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Radio Astronomy Reveals a Long and Winding Road in Space

Radio/optical composite of the Orion Molecular Cloud Complex showing the OMC-2/3 star-forming filament. GBT data is shown in orange. Uncommonly large dust grains there may kick-start planet formation. Credit: S. Schnee, et al.; B. Saxton, B. Kent (NRAO/AUI/NSF); We acknowledge the use of NASA’s SkyView Facility located at NASA Goddard Space Flight Center.

Wow!  Check out this latest image of the Orion Nebula!

Just when you think astronomy can’t get any cooler, something like this comes out: radio astronomers using the Green Bank Telescope (a radio telescope in West Virginia) have found filaments of star-forming gas near the Orion Nebula. Embedded in those filaments are what they think could be large grains of rocky material, the building blocks of planets.

If this discovery is held up through further observations, it would be the first time large particles — perhaps the size of a Lego-type building block — have been detected in such a dense super-nurturing star- and planet-forming nursery. Prior to this, regions of star birth were understood to be thick with dust-sized grains.  The existence of larger grains could change the dynamic of planet formation in this and other regions where larger particles exist.

Scott Schnee, an astronomer at the National Radio Astronomy Observatory (NRAO) and lead on the team doing the work, pointed out that the availability of large-enough (pebble or Lego-sized) planetary building blocks would encourage the formation of planets around newborn stars in the region. “If you want to build a house, it’s best to start with bricks rather than gravel,” he said, implying that it would lead to faster building rates than normal.

Planet formation, similar to building a house, needs material to get started. Most planet nurseries start out with grains of material perhaps no larger than dust specks or maybe sand bits. Over time, those materials stick together to form larger and larger planetesimals, which collide to form planets. If you can start with bigger pieces, that might shorten the planet formation time.

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