Signals from 19 distant stars reveal the possibility of hidden planets orbiting around them, according to astronomers using the world’s most powerful radio antenna.
All signals come from red dwarf stars about 165 light-years from Earth, and four of the signals are best explained by the presence of planets, according to a team from the University of Queensland.
The team, which includes experts from the Dutch National Observatory, used the powerful Netherlands-based Low Frequency Array (LOFAR) radio telescope.
From observations in our solar system, astronomers know that planets emit powerful radio waves as their magnetic fields interact with the solar wind.
This is the first time astronomers have been able to detect radio waves likely from an exoplanet, the team said, an “important step for radio astronomy”.
They cannot tell the size of the suspected planets or whether they are habitable, as the signals are similar to those seen when Jupiter interacts with the solar wind.
The study’s lead author, Dr. Benjamin Pope, said their findings could lead to new techniques in the search for worlds orbiting stars other than our own.
Previously, astronomers were only able to detect the closest stars in constant radio emissions, such as Proxima Centauri, which is just over four light-years away. Everything else in the radio sky was interstellar gas, or strange like black holes.
But the discovery of radio signals from distant stars opens up radio astronomy as a way to find planets orbiting those stars, according to the team.
The researchers focused on red dwarf stars, which are much smaller than the Sun and are known to have intense magnetic activity that drives stellar flares and radio emissions.
However, some older stars that are not magnetically active have also appeared, posing a challenge to conventional understanding.
Dr Joseph Callingham, from Leiden University, said the team is confident that these signals come from magnetic communication of unseen stars and planets in orbits, similar to the interaction between Jupiter and its moon, Io.
He said: “Our Earth has auroras, known here as the northern and southern lights, which also emit powerful radio waves – this is caused by the interaction of the planet’s magnetic field with the solar wind. But in the case of Jupiter’s auroras, they are much more powerful as its moon Io spews material out into space, filling Jupiter’s environment with particles that drive unusually strong auroras. Our model for this radio emission from our stars is an extended version of Jupiter and Io, with a planet encased in a star’s magnetic field, feeding material into massive currents that similarly generate bright auroras. It is a scene that caught our attention light years ago.”
The research team now wants to confirm the existence of the proposed planets, and they will follow up on observations with other types of telescopes.
Dr Pope said: ‘We can’t be 100% sure that the four stars we think have planets are indeed planet hosts, but we can say that the interaction between planets and a star is the best explanation for what we’re seeing. Follow-up observations have ruled out the existence of planets larger than Earth, but there is no telling that a smaller planet would not.”
LOFAR is built by ASTRON in the Netherlands, but has stations across Europe, from the UK to Italy working in collaboration to get a single, larger signal. With the Square Kilometer Array Radio Telescope in Australia and South Africa finally under construction and hopefully operational in 2029, the team expects to be able to see hundreds of related stars to much greater distances.
The research was published in a journal Nature Astronomy.
Source: Daily Mail