Scientists have discovered a lonely orphan planet orbiting the Milky Way – without a parent star to guide it – a “rogue” planet, trapped in endless darkness, with no days, nights, or gravitational siblings.
These make it possible to fill the edge of our galaxy, But this is particularly unusual for a special reason: it is the smallest ever seen – smaller than Earth – with a mass similar to that of Mars.
Scientists have identified more than 4,000 “extrasolar” planets, They are planets orbiting a star other than the Sun. Many foreign flights – for example, where it is – There is no resemblance to the planets in our solar system, but they all have one thing in common: they all revolve around a star.
But a few years ago, astronomers in Poland discovered evidence of free-floating planets in the Milky Way galaxy that were not connected to gravity by a star. A New study, The same astronomers have now discovered such a tiny planet.
Exoplanets are difficult to detect, usually only by observing the light coming from their host stars. Since free-floating planets have no parent star and almost do not emit radiation, astronomers need to take a different approach to finding them.
As a result of Albert Einstein’s theory of general relativity, rough planets are found using gravity microlensing. In this case, the planet’s gravitational (lens) acts as a kind of magnifying glass that can bend the light of a bright star (source) behind it so that an observer on Earth can detect its presence.
“The observer measures the short brightness of the source star,” said Dr. Presmac Miros, a leading author and postgraduate scholar at the California Institute of Technology. News release Thursday. “The chances of observing microlensing are very slim, because the three objects, the source, the lens and the observer, must be almost exactly aligned. If we had only observed one source star, we would have had to wait almost a million years to see that the source is a microlens.”
Researchers looking for these phenomena are observing hundreds of millions of stars in the center of the galaxy, which offers greater opportunities for microlensing.
The Optical Gravity Lens Experiment Survey, led by astronomers at the University of Warsaw, is one of the largest and longest-running astronomical observations in more than 28 years. Using telescopes currently in the Los Campanos Laboratory in Chile, astronomers look for changes in the brightness of the stars on clear nights to center the galaxy.
This technique relies solely on the brightness of the source, not the lens, which allows astronomers to detect faint or dark objects – such as rough planets.
Measuring the duration of such an event, in addition to the shape of its light curve, can provide astronomers with an estimate for the mass of the object they are looking for. While most events caused by stars are over the past several days, the smaller planets offer only a few hour window.
In this case, OGLE-2016-BLG-1928, the shortest microlensing event ever recorded, lasted just 42 minutes. Based on the event, astronomers estimated that the planet had a mass similar to Mars and found it to be rugged.
“When we first discovered this phenomenon, it was clear that it must have been caused by a very small object,” said Dr. Radosla Boleski, associate professor at the Astronomical Laboratory at the University of Warsaw. “If the lens were orbiting a star, we would find its presence in the light curve of the event. We could dismiss a star-studded planet within about 8 astronomical units (the astronomical unit is the distance between the earth and the sun).”
It is not entirely clear why these rogue planets do not have parent stars, but scientists do not think they have said anything to the planets in this regard. Conversely, they may have originally formed “normal” planets – only to be expelled from their parent systems after gravitational exchanges with other planets.
NASA is currently building the Nancy Grace Roman Space Telescope, which is scheduled to be operational by the mid-2020s. Studying these free-floating planets will help astronomers better understand the unstable histories of young planetary systems, including our own solar system.