An international team of astronomers has discovered a massive cloud of gas and dust located in a little-known region of our Milky Way galaxy. The Giant Molecular Cloud (GMC) is about 60 parsecs — or 200 light years — long.
In a new study published in the Astrophysical Journal, researchers using the U.S. National Science Foundation Green Bank Telescope (NSF GBT) have peered into a molecular cloud known as M4.7-0.8, nicknamed the Midpoint cloud. Their observations have revealed a dynamic region bustling with activity, including potential sites of new star formation.
“One of the big discoveries of the paper was the GMC itself. No one had any idea this cloud existed until we looked at this location in the sky and found the dense gas. Through measurements of the size, mass, and density, we confirmed this was a giant molecular cloud,” shares Natalie Butterfield, an NSF National Radio Astronomy Observatory (NSF NRAO) scientist and lead author of this paper.
“These dust lanes are like hidden rivers of gas and dust that are carrying material into the center of our galaxy,” explained Butterfield. “The Midpoint cloud is a place where material from the galaxy’s disk is transitioning into the more extreme environment of the galactic center and provides a unique opportunity to study the initial gas conditions before accumulating in the center of our galaxy.”
The NSF GBT observations focused on molecules like ammonia (NH3) and cyanobutadiyne (HC5N), which are tracers of dense gas. Besides revealing the previously unknown Midpoint cloud in the Galaxy’s inward-bound dust lane, the data also showed:
- A New Maser: The team discovered a previously unknown “maser,” a natural source of intense microwave radiation, associated with ammonia gas. This is often a sign of active star formation.
- Potential Star Birth Sites: The cloud contains compact clumps of gas and dust that appear to be on the verge of forming new stars. One of these clumps, dubbed Knot E, might be a frEGG (free-floating evaporating gas globule) – a small, dense cloud being eroded by radiation from nearby stars.
- Evidence of Stellar Feedback: The team found a shell-like structure within the cloud, possibly created by the energy released from dying stars.
- Turbulent Gas: The gas within the cloud is highly turbulent, similar to what is seen in the galaxy’s central regions. This turbulence could be caused by the inflow of material along the dust lanes or by collisions with other clouds.
“Star formation in galactic bars is a bit of a puzzle,” said Larry Morgan, a scientist with the NSF Green Bank Observatory (NSF GBO), “The strong forces in these regions can actually suppress star formation. However, the leading edges of these bars, such as where the Midpoint is located, can accumulate dense gas and trigger new star formation.”
The team’s findings suggest that the Midpoint cloud is a crucial link in the flow of material from the Milky Way’s disk to its center. By studying this region, astronomers can learn more about how galaxies build their central structures and form new stars in extreme environments.
