Exomoon
[7][8] In September 2019, astronomers reported that the observed dimmings of Tabby's Star may have been produced by fragments resulting from the disruption of an orphaned exomoon.
For extrasolar giant planets orbiting within their stellar habitable zone, there is the prospect that terrestrial planet-sized satellite may be capable of supporting life.
[14][15][clarification needed] In August 2019, astronomers reported that an exomoon in the WASP-49b exoplanet system may be volcanically active.
It showed the physical evolution of host planets (i.e. interior structure and size) plays a major role in their final fate: synchronous orbits can become transient states and moons are prone to be stalled in semi-asymptotic semimajor axes, or even ejected from the system, where other effects can appear.
[14] Despite the great successes of planet hunters with Doppler spectroscopy of the host star,[19] exomoons cannot be found with this technique.
This is because the resultant shifted stellar spectra due to the presence of a planet plus additional satellites would behave identically to a single point-mass moving in orbit of the host star.
During its orbit, Io's ionosphere interacts with Jupiter's magnetosphere, to create a frictional current that causes radio wave emissions.
M. Szabó published a research note titled 'Determination of the size, mass, and density of “exomoons” from photometric transit timing variations'.
[25] In 2009, David Kipping published a paper[3][26] outlining how by combining multiple observations of variations in the time of mid-transit (TTV, caused by the planet leading or trailing the planet–moon system's barycenter when the pair are oriented roughly perpendicular to the line of sight) with variations of the transit duration (TDV, caused by the planet moving along the direction path of transit relative to the planet–moon system's barycenter when the moon–planet axis lies roughly along the line of sight) a unique exomoon signature is produced.
In a later study, Kipping concluded that habitable zone exomoons could be detected by the Kepler Space Telescope[27] using the TTV and TDV effects.
If a planet and a moon pass in front of a host star, both objects should produce a dip in the observed light.
[29] Exomoons of directly imaged exoplanets and free-floating planets are predicted to have a high transit probability and occurrence rate.
The researchers conclude that oxygen, carbon or nitrogen atoms must have been subjected to MeV collisions with protons in order to create this excess of beryllium.
The strong magnetic field of such a giant planet accelerates stellar wind particles, such as protons, and directs them into the disk.
The accelerated proton collides with water ice in the disk, creating elements like beryllium, boron, and lithium in a spallation reaction.
In a second study, René Heller[38] then included the effect of eclipses into this concept as well as constraints from a satellite's orbital stability.
However, for any larger, Ganymede-sized moons venturing into its solar system's habitable zone, an atmosphere and surface water could be retained indefinitely.
An exomoon in an M-dwarf system does not face this challenge, as it is tidally locked to the planet and it would receive light for both hemispheres.
However, since the exomoon's primary is an exoplanet, it would continue to rotate relative to its star after becoming tidally locked, and thus would still experience a day/night cycle indefinitely.
The possible exomoon candidate transiting 2MASS J1119-1137AB lies in the habitable zone of its host (at least initially until the planet cools), but it is unlikely complex life has formed as the system is only 10 Myr old.
If confirmed, the exomoon may be similar to primordial earth and characterization of its atmosphere with the James Webb Space Telescope could perhaps place limits on the time scale for the formation of life.
