A study performed by scientists at NASA concluded that Neptune-mass planets are probably the most common kind of planets that make up the terrestrial content of the galaxy past the snow line.
How Do Researchers Detect Astronomical Objects In The Galaxy?
Researchers use the phenomenon of gravitational microlensing for detecting and studying the nature of remote astronomical objects. Microlensing is an astronomical occurrence that assists the study of sky-high objects that may or may not radiate light.
Based on Einstein's theory of relativity, this technique helps astronomers detect presence of objects ranging from mass of a planet to mass of a star. It is suitable for finding low-mass planets or planets in proximity with very remote or dimly lit stars.
The gravitational microlensing technique works when a remote background star, acting as the source, gets suitably in-line with a foreground star that acts as a lens in front of it. The light bends because of the presence of gravitational field, producing two deformed vague images which results in an evident magnification.
As the foreground star moves on its orbital path, the alignment changes over a period of time, varying the noticeable glow of the source object. These varying light patterns enable the astronomers to study the nature of the lensing star and the source star.
The Detection Of Planets Through Microlensing Technique At NASA
The study conducted by a group of scientists at NASA's Goddard Space Flight Center in Greenbelt, Maryland, inferred that cold Neptunes or Neptune-mass planets are possibly the most frequent planets that exist beyond the snow line.
"We've found the apparent sweet spot in the sizes of cold planets. Contrary to some theoretical predictions, we infer from current detections that the most numerous have masses similar to Neptune, and there doesn't seem to be the expected increase in number at lower masses," said scientist Daisuke Suzuki, in a press release. He further concluded that cold Neptunes in the external orbits are about 10 times more frequent than Jupiter-mass planets in Jupiter-like orbits.
Discovering The Galaxy Far And Beyond
With the help of microlensing technique, astronomers have been able to discover approximately 50 exoplanets. This technique can be efficiently used to identify planets situated farther away by hundreds of times, compared with other techniques, like radial velocity method or the fainting of a source star. The small mass exoplanets located at large distances from their host star, or the vagabond planets drifting through the galaxy on their own, can be easily detected using microlensing.
Moreover, microlensing mixed with other astronomical techniques can help astronomers put forward a much comprehensible image of the terrestrial construct of our galaxy.
The Microlensing Observations in Astrophysics group, which works as a partnership of scientists from Japan and New Zealand, has issued several observations in accordance with the microlensing events taking place between 2007 and 2012. They recognized 1,474 highly monitored microlensing events with 22 showing clear terrestrial signals. This comprises of four planets that were never found before.