Last year, we reported on how the supporters of the Roman Space Telescope hoped it would be able to detect winding planets using a technique called “microlensing”. Now a team led by Iain McDonald, then at the University of Manchester, beat them to punch by finding a few examples of Earth-sized villainous planets using data from an already aging space telescope – Kepler.
However, both the collection and analysis of the data used in the study were not easy. Kepler launched a two-month campaign in 2016 that made it look at millions of stars located near the center of the Milky Way every 30 minutes. Even with so much data, it was difficult to select the signal from noise.
They are difficult because microlensing is exhibited by small fluctuations in the light of stars when an object passes in front of them. According to Dr. McDonald’s is exposed to microlensing around every one in a million stars in the galaxy at any given time. So of the millions of stars toward the center of the Milky Way, several could undergo microlensing right now.
These events can last anywhere from minutes to days as it depends on the difference between the foreground object and background stars as well as the weight of the foreground object. Of the many microlensing events that take place toward the galactic core, only approx. 1% of them are caused by false planets, and the signals from these events are much smaller compared to microlenses caused by foreground stars.
Despite all the difficulties of collecting data with an old telescope, siphoning through all the extra data and background noise and trying to distinguish between events caused by stars and those caused by planets, Dr. McDonald and his co-author, Eamonn Kerins able to find 27 candidates for microlens events. Of these, four could potentially have been caused by villainous planets on Earth.
The duration of the events varied greatly – from an hour and ten days in length, and some had previously been detected using terrestrial observation. But the four that were indicative of Earth-sized exoplanets were brand new.
Most likely, these new potential rogue planets will be the beginning of a wave of new discoveries. Not only is Nancy Grace specifically designed to detect rogue planets using the technique in the paper (and which Kepler very clearly was not designed for), there is an ESA mission called Euclid that will hopefully start sometime next year, which is also tailored to search for microlending events.
Speculations about junk planets have been around for decades, and while we are finally getting to say that they exist, these microlensing events are only preliminary evidence. But if confirmed, they will have a dramatic impact on our understanding of both how planets are formed, but also our estimates of how many might be lurking in the great darkness between stars.
RAS – The Kepler telescope glimpses the population of free-floating planets
SciTechDaily – Mysterious Population of Rogue Planets Spotted Near the Center of Our Galaxy
Gizmodo – Astronomers find a party of villainous planets near the galactic core
Lead picture –
The artist’s perception of a rogue planet.
Credit – A. Stelter / Wikimedia Commons