Four small planets discovered around one of the closest stars to Earth – experts explain what we know

Bernard’s star is a small, dim star of what astronomers call the Red Dwarves. As a result, it is too faint for naked eye to see, so that it only takes six years for its light to reach here, despite being one of the closest stars to Earth. Now we know that four small planets orbit the stars. Teams in the US and Europe achieved this challenging detection by leveraging precision instruments on the world’s largest telescope.

The smaller Bernard star is closer to Jupiter than the Sun. Only the three stars that make up the Alpha Centauri system are close to us.

How were newly discovered planets around Bernard’s star discovered as they are too faint to be seen directly? The answer lies in the effects of gravity on the stars. The appeal of mutual gravity not only puts the planet in orbit, but also pulls the star and moves it with a rhythmic dance that can be detected by a sensitive spectrograph instrument. The spectrograph divides the light of a star into the wavelengths of the component. You can use them to measure the movement of stars.

However, the important challenge for detection is the actions of the stars themselves. Stars are liquids, and nuclear reactors are in core-driven driving motions that generate magnetic fields (just as the stirring of Earth’s melting cores produces Earth’s magnetic fields). The surface of the red star is filled with magnetic storms. This activity can mimic the signature of a planet.

The task of finding a planet in this way begins with the construction of a highly sensitive spectroscopic instrument. They are mounted on telescopes large enough to capture enough light from the stars. The light is then sent to the spectrograph that records the data. Astronomers then observe the stars for months or years. After carefully calibrating the resulting data, explaining the magnetic activity of the star, you can scrutinize the data of the small signal revealing the orbiting planet.

In 2024, a team led by Jonay González Hernández of the Astrophysics Institute in the Canary Islands reported that they monitored Bernard’s star for four years with spectroscopic armor from the espresso of a very large telescope at Chile’s southern European observatory. They found one distinct planet and reported a preliminary signal indicating three more planets.

The team, currently led by Ritvik Basant at the University of Chicago, has added three years of surveillance on the Gemini North telescope’s Maroon-X instrument in a paper that just appeared in the Astrophysical Journal Letters. Analyzing the data confirmed the existence of three out of four planets, and by combining both datasets, we found that all four planets were authentic.

In many cases, if detection pushes the limits of current capabilities, the reliability of the findings needs to be considered. Are there any fake equipment effects that the team hasn’t explained? Therefore, it is reassuring when independent teams arrive at the same conclusion, using different telescopes, instruments and computer codes.

The planets form a tightly packed, densely packed system with short orbital periods of Earth Days of 2-7 days (for comparison, the closest planet of the Sun, mercury, orbital in 88 days). They could all have fewer masses than Earth. They are probably rocky planets, with bare rock surfaces being blown up by the radiation of their stars. They would be too hot to hold liquid water, and any atmosphere could have been stripped away.

The team searched for a longer period of planet in the star’s habitable zone, but found nothing. I don’t know much else about the new planet, such as estimated size. The best way to understand that is to monitor the transit when a planet passes in front of a star and measures the amount of starlight it blocks. However, Bernard’s planet is not directed in a way that looks at the “rim” from our perspective. This means that the planets will not pass through and it will become difficult to study.

Nevertheless, Bernard’s planet tells us about the planetary layer. They are formed from protranetary discs of material that swirled around the stars when they were young. The dust particles get stuck together and gradually accumulate in rocks aggregated on planets. The Red Dwarf is the most common type of star, and most of them seem to have planets. Whenever there is sufficient observation of such a star, we find planets, so there are likely to be far more planets in a galaxy than stars.

Most of the discovered planets are located near the stars and within habitable zones (liquid water can survive on the planet’s surface), but this is mainly because their proximity makes them much easier to find. Being close means there is a greater gravitational pull, which means they have a shorter orbital period (so there is no need to monitor the stars for a long time). It also increases the likelihood of passing and is therefore discovered in transport investigations.

The European Space Agency’s Plato mission began in 2026 and is designed to find more planets from the stars. This should produce more planets in habitable zones and start telling us whether our own solar system, which has no nearby planets, is unusual.

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