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Starts With A Bang

See the Milky Way’s center as we’ve never seen it before

As viewed by the MeerKAT telescope, this radio view of the Milky Way blows away every other way we’ve ever seen our home galaxy.
Milky Way center
This unprecedented view of the galactic center comes from the MeerKAT radio array in South Africa, and highlights never-before seen features, including filaments, previously unseen bubbles, and potentially new supernova remnants and star-forming regions as well.
Credit: I. Heywood et al., 2022, ApJ
Key Takeaways
  • Although we’ve viewed our own galactic center in many wavelengths of light before, the newest high-resolution radio survey has revealed some surprises.
  • MeerKAT, the first step in ultimately constructing the Square Kilometer Array, has just revealed their first comprehensive map of the Milky Way’s central region.
  • Insie are non-thermal filaments, radio loops, and potential supernova remnants and/or star-forming regions we’ve never uncovered before. No matter how much we learn, more wonders always await us in the Universe.

The Milky Way’s center is one of nature’s longstanding mysteries.

The Milky Way, as seen at La Silla observatory, is a stunning, awe-inspiring sight to anyone, and offers a spectacular view of a great many stars in our galaxy. However, we cannot see what truly resides in the galactic center with visible light alone, as our eyes cannot penetrate the light-blocking dust that intervenes. (Credit: ESO/Håkon Dahle)

Human eyes, from ~26,000 light-years away, are hindered by light-blocking dust.

Milky Way center
This spectacular composite image, which combines X-ray, infrared, and optical light from NASA’s great observatories, was our best view of what’s going on in the galactic center as of 2009. Over the past ~13 years, however, we’ve taken data that has revealed novel features that, at present, have yet to be fully explained. (Credit: NASA/JPL-Caltech/ESA/CXC/STScI)

Other wavelengths of light, however, reveal enormously informative spectacles.

This 20-year time-lapse of stars near the center of our galaxy comes from the ESO, published in 2018. Note how the resolution and sensitivity of the features sharpen and improve toward the end, all orbiting our galaxy’s (invisible) central supermassive black hole. These observations required infrared light to see, as the optical part of the spectrum is obscure in the direction of the galactic plane. (Credit: ESO/MPE)

Gamma rays reveal pulsars and ancient supernovae.

Fermi’s view of the gamma-ray sky reveals the emission from our own galaxy, from extragalactic objects, from pulsars, and, as highlighted here, from supernova remnants as well. (Credit: NASA/DOE/Fermi LAT Collaboration)

Infrared observations show us hydrocarbons and warm dust.

This three-color composite shows the galactic center as imaged in three different wavelength bands by NASA’s Spitzer: the predecessor to the James Webb Space Telescope. Carbon-rich molecules, known as polycyclic aromatic hydrocarbons, show up in green, while stars and warm dust are also visible. (Credit: NASA/JPL-Caltech)

Optical and near-infrared views map out stars and gas.

Gaia’s all-sky view of our Milky Way Galaxy and neighbouring galaxies. The maps show the total brightness and colour of stars (top), the total density of stars (middle) and the interstellar dust that fills the Galaxy (bottom). (Credit: ESA/Gaia/DPAC)

Meanwhile, X-rays reveal black holes and superheated matter.

Black holes, pulsars, superheated gas, and magnetic fields can all be identified from their X-ray signatures in images of the galactic center. (Credit: NASA/CXC/UMass/Q.D. Wang)

Still, the first comprehensive, high-resolution radio map revealed unexpected, fantastical features.

Milky Way Center
This mosaic of MeerKAT data shows the central region of the galactic plane in 1.28 GHz radio frequencies. The galactic center is the brightest area, but the non-thermal radio filaments, as well as some newly discovered radio bubbles, still lack a comprehensive explanation. (Credit: I. Heywood et al., 2022, ApJ)

Conducted by MeerKAT, the first step toward the Square Kilometer Array‘s completion, our galaxy’s magnetism shines.

The MeerKAT array, the first step in the construction of the Square Kilometer Array, has already produced an unprecedented set of science images and data that takes us one step closer to understanding our galactic center. (Credit: South African Radio Astronomy Observatory)

Non-thermal radio filaments are ubiquitous, commonly stretching for hundreds of light-years.

Although there are numerous radio features that appear in the MeerKAT data that mapped our galactic center, like shells and double-lobed structures, the most poorly understood development has been the identification of numerous NTFs: non-thermal filaments, whose existence had been predicted but whose identified features now need to be analyzed in depth. (Credit: I. Heywood et al., 2022, ApJ)

They connect high-energy sources across the galaxy, like supernova remnants and star-forming regions.

Milky Way center
Although the galactic center appears striking at the lower-right of this image, much more puzzling are the “loopy” features seen, which are evidence for filamentary strands of galactic magnetism. These non-thermal filaments have been predicted theoretically, but MeerKAT has identified and imaged them with unexpected and never-before-seen properties. (Credit: I. Heywood et al., 2022, ApJ)

Sadly, galactic magnetism is still poorly understood.

This radio image, from MeerKAT, of the Sagittarius B region of the galactic center, showcases a complex magnetic structure and copious radio emissions. (Credit: I. Heywood et al., 2022, ApJ)

A radio cocoon surrounding our supermassive black hole is the Milky Way’s most energetic source.

This view of the cocoon surrounding the Milky Way’s galactic center is only ~10 light-years across, but contains and is possibly powered by our central, supermassive black hole that weighs in at ~4 million times the mass of our Sun! (Credit: I. Heywood et al., 2022, ApJ)

The quintuplet cluster and Pistol Star show radio signatures from stellar features.

This animation shows Hubble Space Telescope imaging of the Pistol Star and the surrounding region, while radio data, including these newly discovered non-thermal radio filaments, overlays it. This type of multiwavelength imaging can reveal connections between features that we cannot observe any other way. (Credit: I. Heywood et al., 2022, ApJ)

These radio filaments have an unknown origin.

Although nothing has photobombed this region of space, the “streaks” throughout make it look like something has caused them. These are real features in our galactic center, however, and they can stretch for hundreds of light-years. Highly magnetized, much remains to be untangled in the understanding of these non-thermal filaments. (Credit: I. Heywood et al., 2022, ApJ)

However, supernova remnants, such as SNR G0.33+0.04,

The region of space surrounding supernova remnant SNR G0.33+0.04 is littered with strong radio filaments, evidence for magnetic structures that connect various regions to one another. Our galaxy, overall, has ~microGauss magnetic fields throughout it, but they switch back on large-scales and are not coherent. Understanding their connection to supernova remnants may be the key to the nature of galactic magnetic fields. (Credit: I. Heywood et al., 2022, ApJ)

SNR G0.9+0.1,

This young, bright supernova remnant, SNR G0.9+0.1, has a series of cocoon-like radio structures surrounding it. One of the science lessons from MeerKAT data shows us how supernovae evolve in the radio as they age. (Credit: I. Heywood et al., 2022, ApJ)

and the newfound source G358.7+0.8,

This newly discovered radio bubble in the MeerKAT data, G358.7+0.8, could arise from either a supernova remnant or from an ionized star-forming region. The bubble is connected to a point source, at right (circled), but the nature of this magnetic connection is not understood. (Credit: I. Heywood et al., 2022, ApJ)

can potentially explain how galactic supernovae, and their evolution, create these radio features.

This two-panel animation shows the radio emissions of a low-surface brightness structure at G0.8-0.4 alongside it’s mid-infrared emissions as measured by NASA’s WISE spacecraft. It is unknown whether this is a supernova remnant or a shell driven by thermal winds from a region of ionized hydrogen. The solid-circled double-lobed structures are likely background radio galaxies. (Credit: I. Heywood et al., 2022, ApJ)

Much remains to discover, but this new view of the Milky Way only enhances its mystery and wonder.

This updated Radio/X-ray composite of the galactic center, featuring data from both MeerKAT and Chandra, showcases the new information that can be gleaned from stitching together multiple wavelengths of light. In the future, improved observations and superior observatories may help us solve the scientific mysteries that MeerKAT has recently revealed. (Credit: X-ray: NASA/CXC/UMass/Q.D. Wang; Radio: NRF/SARAO/MeerKAT)

Mostly Mute Monday tells an astronomical story in images, visuals, and no more than 200 words. Talk less; smile more.


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