Community hub
Recent from talks
Knowledge base stats:
Talk channels stats:
Members stats:
Molecular cloud
A molecular cloud—sometimes called a stellar nursery if star formation is occurring within—is a type of interstellar cloud of which the density and size permit absorption nebulae, the formation of molecules (most commonly molecular hydrogen, H2), and the formation of H II regions. This is in contrast to other areas of the interstellar medium that contain predominantly ionized gas.
Molecular hydrogen is difficult to detect by infrared and radio observations, so the molecule most often used to determine the presence of H2 is carbon monoxide (CO). The ratio between CO luminosity and H2 mass is thought to be constant, although there are reasons to doubt this assumption in observations of some other galaxies.
Within molecular clouds are regions with higher density, where much dust and many gas cores reside, called clumps. These clumps are the beginning of star formation if gravitational forces are sufficient to cause the dust and gas to collapse.
The history pertaining to the discovery of molecular clouds is closely related to the development of radio astronomy and astrochemistry. During World War II, at a small gathering of scientists, Henk van de Hulst first reported he had calculated the neutral hydrogen atom should transmit a detectable radio signal. This discovery was an important step towards the research that would eventually lead to the detection of molecular clouds.
Once the war ended, and aware of the pioneering radio astronomical observations performed by Jansky and Reber in the US, the Dutch astronomers repurposed the dish-shaped antennas running along the Dutch coastline that were once used by the Germans as a warning radar system and modified into radio telescopes, initiating the search for the hydrogen signature in the depths of space.
The neutral hydrogen atom consists of a proton with an electron in its orbit. Both the proton and the electron have a spin property. When the spin state flips from a parallel condition to antiparallel, which contains less energy, the atom gets rid of the excess energy by radiating a spectral line at a frequency of 1420.405 MHz.
This frequency is generally known as the 21 cm line, referring to its wavelength in the radio band. The 21 cm line is the signature of HI and makes the gas detectable to astronomers back on earth. The discovery of the 21 cm line was the first step towards the technology that would allow astronomers to detect compounds and molecules in interstellar space.
In 1951, two research groups nearly simultaneously discovered radio emission from interstellar neutral hydrogen. Ewen and Purcell reported the detection of the 21-cm line in March, 1951. Using the radio telescope at the Kootwijk Observatory, Muller and Oort reported the detection of the hydrogen emission line in May of that same year.
Hub AI
Molecular cloud AI simulator
(@Molecular cloud_simulator)
Molecular cloud
A molecular cloud—sometimes called a stellar nursery if star formation is occurring within—is a type of interstellar cloud of which the density and size permit absorption nebulae, the formation of molecules (most commonly molecular hydrogen, H2), and the formation of H II regions. This is in contrast to other areas of the interstellar medium that contain predominantly ionized gas.
Molecular hydrogen is difficult to detect by infrared and radio observations, so the molecule most often used to determine the presence of H2 is carbon monoxide (CO). The ratio between CO luminosity and H2 mass is thought to be constant, although there are reasons to doubt this assumption in observations of some other galaxies.
Within molecular clouds are regions with higher density, where much dust and many gas cores reside, called clumps. These clumps are the beginning of star formation if gravitational forces are sufficient to cause the dust and gas to collapse.
The history pertaining to the discovery of molecular clouds is closely related to the development of radio astronomy and astrochemistry. During World War II, at a small gathering of scientists, Henk van de Hulst first reported he had calculated the neutral hydrogen atom should transmit a detectable radio signal. This discovery was an important step towards the research that would eventually lead to the detection of molecular clouds.
Once the war ended, and aware of the pioneering radio astronomical observations performed by Jansky and Reber in the US, the Dutch astronomers repurposed the dish-shaped antennas running along the Dutch coastline that were once used by the Germans as a warning radar system and modified into radio telescopes, initiating the search for the hydrogen signature in the depths of space.
The neutral hydrogen atom consists of a proton with an electron in its orbit. Both the proton and the electron have a spin property. When the spin state flips from a parallel condition to antiparallel, which contains less energy, the atom gets rid of the excess energy by radiating a spectral line at a frequency of 1420.405 MHz.
This frequency is generally known as the 21 cm line, referring to its wavelength in the radio band. The 21 cm line is the signature of HI and makes the gas detectable to astronomers back on earth. The discovery of the 21 cm line was the first step towards the technology that would allow astronomers to detect compounds and molecules in interstellar space.
In 1951, two research groups nearly simultaneously discovered radio emission from interstellar neutral hydrogen. Ewen and Purcell reported the detection of the 21-cm line in March, 1951. Using the radio telescope at the Kootwijk Observatory, Muller and Oort reported the detection of the hydrogen emission line in May of that same year.