Sagittarius B2

Sagittarius B2, often called Sgr B2, is a massive molecular cloud. This cloud consists of gas and dust. It is located near the center of the Milky Way galaxy. It is the largest molecular cloud near the galactic core. It is also one of the largest clouds in our entire galaxy. This complex spans a region about 50 parsecs across. Its total mass is roughly 3 million times the mass of our Sun.

The cloud is much denser than most other clouds in space. Its mean hydrogen density is 3000 atoms per cubic centimeter. This is about 20 to 40 times denser than a typical molecular cloud. The internal structure is quite complex. It features many different temperatures and densities throughout. The cloud is divided into three primary cores. These are the north (N), middle or main (M), and south (S) cores. The middle and north cores are sites of prolific star formation.

Star formation occurs within specific regions of the cloud. Scientists have identified several H II regions within the cores. These are areas of ionized hydrogen. The first ten discovered were named A through J. Regions A through G, I, and J are located in the middle core. Region K is found in the north core. Region H is located in the south core. The star-forming core is about 5 parsecs wide. This specific area emits about 10 million times the luminosity of the Sun.

Chemistry in Sgr B2 is incredibly rich and complex. The cloud contains many different types of molecules. Scientists used a spectrograph to study its composition. They were specifically looking for amino acids. They discovered various alcohols, such as ethanol, vinyl alcohol, and methanol. They also found an ester called ethyl formate. This ester is a major precursor to amino acids. Ethyl formate is also the chemical responsible for the flavor of raspberries. Because of this, some articles suggest the cloud might smell like "raspberry rum."

Chemical reactions happen in a very specific way in this environment. The average temperature and pressure are quite low. Because of this, atoms do not interact directly very easily. Instead, the cloud contains many tiny, cold dust grains. Each grain has a silicon core. This core is surrounded by a mantle of water ice and carbon compounds. These grains act as a surface for chemical reactions. Molecules accrete, or stick, to the grain surfaces. Once they interact with neighboring compounds, they can evaporate. They then join the rest of the molecular cloud.

Many important astronomical discoveries have come from studying Sgr B2. About half of all known interstellar molecules were first found near this cloud. Nearly every other known molecule has also been detected here. In 2011, Japanese astronomers used the Suzaku satellite to study the Galactic Center. They found that the European Space Agency's INTEGRAL observatory saw gamma rays interacting with the cloud. This interaction caused X-ray emission. These rays were emitted about 350 years ago. The energy came from Sagittarius A*, the supermassive black hole at our galaxy's core. That outburst was an estimated million times stronger than the current output of the black hole.

Recent observations have provided even more detail about the cloud. The James Webb Space Telescope (JWST) has revealed new candidate H II regions. These were previously missed by radio observations. At 25 micrometers, researchers found infrared radiation escaping the Sgr B2 N protocluster. This radiation follows the path of a large-scale outflow. While some young stellar objects (YSOs) seen by ALMA are not detected by JWST, the telescope does see hot dust around their outflows. On the eastern side, the JWST has detected recent star formation. These findings help us understand how stars and molecules grow in the center of our galaxy.