The Milky Way’s Supermassive Black Hole May Be Aiming Radio Jets At Us

Milky Way’s Supermassive Black Hole
Image source: YouTube Video Screenshot

Scientists have been studying the Milky Way’s supermassive black hole using a powerful ALMA telescope connected to an array of telescopes. They learned that the radio jet emissions from the supermassive black hole referred to as Sagittarius A* appear to be aimed directly at our solar system.

The new study allowed scientists to see that the black hole lying at the heart of our galaxy is surrounded by a smaller area than was previously thought. The findings of the study led by Ph.D. student Sara Issaoun were published in The Astrophysical Journal.

Previous attempts to study the Milky Way’’s supermassive black hole weren’t as successful because it is surrounded by a foggy cloud of hot gas, which made scientists unable to see it clearly. However, by using the ALMA telescope in northern Chile and connecting it to a global network of radio telescopes, scientists were able to see through the fog. The black hole’s emission region is so small that the source of those emissions could be aimed at Earth.

“This may indicate that the radio emission is produced in a disk of infalling gas rather than by a radio jet,” Issaoun said in a statement. “However, that would make Sagittarius A* an exception compared to other radio-emitting black holes. The alternative could be that the radio jet is pointing almost at us.”

Issaoun has tested several computer models against the data. Her supervisor, radio astronomy professor Heino Falcke of Radboud University, called this event unusual, but he also confirmed the findings.

“Maybe this is true after all,”  Falcke said, “And we are looking at this beast from a very special vantage point.”

Sagittarius A* is the Milky Way’s supermassive black hole, and scientists estimate its weight at about 4 million solar masses and its size on the sky at less than 100-millionth of a degree. According to scientists, that size is comparable to the size of a tennis ball on the moon if it could be watched from Earth. Scientists had to use the VLBI technique to measure its size.

“Sagittarius A* is located in the southern sky, thus the participation of ALMA is important not only because of its sensitivity, but also because of its location in the southern hemisphere,” Ciriaco Goddi, from the European ALMA Regional Center node in the Netherlands said.

In addition to the powerful ALMA telescope, scientists also used 12 radio telescopes in North America and Europe as part of the network. Thanks to these connections, scientists managed to achieve a resolution twice as high as that of previous observations. In the future, the team plans to study different wavelengths, which they expect to shed more light on the emission source of Sagittarius A*. They believe the source also provides the key to understanding supermassive black holes.