What if Mercury suddenly disappears?

“Dissolved into nothing!” The planet closest to our solar system has disappeared.

Scientists just made a planet disappear. According to a new study, Alpha Centauri Bb, previously known as a celestial body in a star system in our neighborhood, is simply a misinterpretation of measurement data.

The planet, whose mass should be roughly on the order of the earth, was called a "milestone" when it was first introduced in 2012 in the magazine "Nature". The discovery raised hopes in many people for a promising search for neighboring celestial bodies with forms of life in the Alpha Centauri system, 4.3 light years away - and home to science fiction characters such as the Transformers and the creatures from the film "Avatar" .

However, this alien celestial body would not have been a good place to search for life. Its distance from its star would have been only a tenth of the distance between Mercury and the sun. It would have had a scorching surface that would probably have been covered in molten rock.

It can now serve as a warning example for planet hunters, reminding us that small planets like Earth are difficult to find. Distinguishing imperceptible cues from background noise is extremely difficult, as shown by an article published on arXiv.org and also in the Monthly Notices of the Royal Astronomical Society.

Even the team that originally discovered the planet confirms what it said. "This is a very good contribution," says Xavier Dumusque of the Harvard-Smithsonian Center for Astrophysics. "We're not 100 percent sure, but this planet probably doesn't exist."


It is not the first celestial body to disappear. In 2005, Polish astronomer Maciej Konacki presented fascinating evidence that a gas planet resembling Jupiter resides inside HD 188753, a compact triple star system. The publication made waves in the astronomical research community: According to the generally accepted theories on the formation of planets, the gravitational fields of the triple star system should actually have prevented the formation of such a large planet. However, two years later it turned out that other researchers failed to confirm Konacki's observation. His discovery turned out to be a false positive.

Dumusque originally found the Alpha Centauri planet by observing the light from the star Alpha Centauri B. The spectrum of the light from this star shifted alternately to blue and red at regular intervals. A process that can be compared to the tone change of a siren, ever depending on whether it moves away from or towards a listener. The star seemed to move back and forth a bit every three days, as if it were under the influence of a small planet in its orbit.

Oscillating stars have been used as evidence for hundreds of other planets. However, these planets were all larger. Some researchers questioned the discovery, including the astronomer Artie Hatzes from the Friedrich Schiller University Jena, an early pioneer of the exoplanet research community. He published a skeptical analysis.

At the moment it looks as if the incompleteness of the measurement data is responsible for the “emergence” of the planet.

The idea of ​​a listener to a piano concerto who only hears every tenth note of the piece being played can help to understand what is happening. With such an experimental setup, it would not be surprising if he confused Bach with Beethoven. An astronomer who sees a star only at selected observation times, as was the case with the telescope images from which Bb was inferred, can be subject to similar deceptions.

Vinesh Rajpaul, an astrophysics graduate from the University of Oxford, showed that the finest patterns of light caused by phenomena that have nothing to do with a planet - for example, spots on the star's surface, electronic noise in observation devices or the gravitational pull of other stars - fake the existence of a planet.


To substantiate this thesis, Rajpaul created a computer simulation of a star without planets that is only observed sporadically.

"When evaluating our artificially generated data, the planet that we had not simulated at all reliably emerged," said Rajpaul.

According to Rajpaul, such a false trace is not a problem for the majority of the more than 5600 other planet candidates found so far, because most of the celestial bodies are considerably larger.

The Kepler space telescope has also found planets that are smaller than Earth. However, it continuously observes a certain region of the sky and uses a completely different method. It waits for planets that fly past their stars, and thereby slightly darken their light.

Aware of the challenges that existed, Dumusque recently challenged his colleagues to a planet-search competition. He made simulations of stars orbiting planets of different sizes - and simulations of stars without planets. Teams of experts looking for oscillations caused by larger planets came up with the correct result 90 percent of the time. With smaller planets, the best team was only right 10 percent of the time.

Correction: Artie Hatzes' name and place of work have been corrected.

With contributions by Michael Greshko.

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Article published in English on October 29, 2015