Recent Starburst In The Milky Way Galaxy's Center Spotted

 

SOFIA/FORCAST mid-infrared image of the Milky Way galaxy’s nucleus showing the Circumnuclear Ring (CNR) of gas and dust clouds orbiting a central supermassive black hole. The bright Y-shaped feature is believed to be material falling from the ring toward the black hole that is located where the arms of the “Y” intersect. 

Credit:  NASA/SOFIA/FORCAST team/Lau et al. 

SOFIA is a highly modified Boeing 747SP aircraft carrying a telescope with an effective diameter of 100 inches (2.54 meters) to altitudes as high as 45,000 feet (13.7 kilometers).

The images were obtained during SOFIA flights in 2011 with the Faint Object Infrared Camera for the SOFIA Telescope (FORCAST) instrument built by a team with principal investigator Terry Herter of Cornell.

FORCAST offered astronomers the ability to see the CNR and QC regions and other exotic cosmic features whose light is obscured by water vapor in Earth’s atmosphere and interstellar dust clouds in the mid-plane of the Milky Way. Neither ground-based observatories on tall mountain peaks nor NASA’s orbiting Hubble and Spitzer space telescopes can see them.

Hubble Space Telescope/NICMOS near-infrared image showing the same field of view with the same scale and orientation as the image above. At this wavelength, opaque dust in the plane of the Milky Way hides features that are seen in the SOFIA image. 

Credit: NASA/STScI

Each image is a combination of multiple exposures at wavelengths of 20, 32, and 37 microns.

Figure 1a shows the CNR and Figure 2a shows the QC. The CNR and other exotic features revealed by SOFIA’s FORCAST camera are invisible to Hubble’s near-infrared camera, as shown for comparison in figures 1b and 2b. Figure 3 shows the two fields studied in these papers as square insets on a large-scale image of the galactic center made by the Spitzer Space Telescope at a wavelength of 8 microns.

“The focus of our study has been to determine the structure of the circumnuclear ring with the unprecedented precision possible with SOFIA” said Lau. “Using these data we can learn about the processes that accelerate and heat the ring.”

The nucleus of the Milky Way is inhabited by a black hole with 4 million times the mass of the sun and is orbited by a large disk of gas and dust. The ring seen in Figure 1a is the inner edge of that disk. The galactic center also hosts several exceptionally large star clusters containing some of the most luminous young stars in the galaxy, one of which is the Quintuplet Cluster seen in Figure 2. The combination of SOFIA’s airborne telescope with the FORCAST camera produced the sharpest images of those regions ever obtained at mid-infrared wavelengths, allowing discernment of new clues about what is happening near the central black hole.

SOFIA/FORCAST mid-infrared image of a region including the Quintuple Cluster (QC), a group of young stars near the left margin of the frame, located about 35 parsecs (100 light years) from the galaxy’s nucleus.

  
Credit: NASA/SOFIA/Hankins et al

“Something big happened in the Milky Way’s center within the past 4 million to 6 million years which resulted in several bursts of star formation, creating the Quintuplet Cluster, the Central Cluster, and one other massive star cluster.” said Hankins, lead author of the QC paper. “Many other galaxies also have so-called ‘starbursts’ in their central regions, some associated with central black holes, some not. The Milky Way’s center is much nearer than other galaxies, making it easier for us to explore possible connections between the starbursts and the black hole.”

SOFIA Chief Scientific Advisor Eric Becklin, who is working with the CNR group, determined the location of the galaxy’s nucleus as a graduate student in the 1960s by laboriously scanning a single-pixel infrared detector to map the central region.

 

 Credit:  NASA/STScI