(ORDO NEWS) — A purported exoplanet orbiting a star in the constellation Eridani associated with Star Trek’s fictional Vulcan homeworld could just be a hoax in the star’s spectrum – a spectral ghost.
An analysis of discovery data from multiple exoplanets across the galaxy revealed that several of the detections were actually false positives: light fluctuations emitted by a single star, not an interaction with an exoplanet in orbit.
So hopes for a Vulcan planet – at least for now – have been shattered, but it’s a result that should lead to more reliable exoplanets in the future.
The results have been accepted by The Astronomical Journal and are available on the arXiv preprint server.
In 2018, the discovery of an exoplanet was announced: a world called 40 Eridani b orbiting the star 40 Eridani A, a rocky super-Earth orbiting the star once every 42 Earth days or so.
It was discovered based on a property known as radial velocity, nt push-pull, manifested by fluctuations in the wavelength of light coming from the star.
A star with planets around it is affected by the gravitational effects of planetary orbits. The bodies do not rotate one around the other, but both around a common center of gravity.
This means that the star seems to wobble slightly in place as the exoplanet moves around it; it can be detected by its light.
Any light emitted by a star or part of a star moving towards us is compressed slightly, shifting towards the blue end of the spectrum. The light emitted by something moving away from us is slightly lengthened, shifting towards red.
When caused by an exoplanet, it can be detected as the entire stellar spectrum moves back and forth slightly on normal time scales.
But it’s not always easy to get an exoplanet out of this apparent wobble. If there is any activity on the star’s surface – bright spots or star spots – they will also cause fluctuations in the spectrum with a periodicity corresponding to the rotation of the star as they appear and disappear from view.
And here we run into problems with 40 Eridani b.
The orbital period of the proposed exoplanet was very close to the star’s predicted rotation period, somewhere between 37 and 43 days.
At the time, the researchers said it was possible that what they interpreted as an exoplanet signal could be a rotation signal, but could not get the star’s exact rotation period.
Because then other astronomers took a closer look. A 2021 paper that used a newly developed pipeline to detect radial velocity signals found that the detection of 40 Eridani b was a false positive. The 2022 article failed to draw a conclusion.
Now a team led by Ohio State University physicist Katherine Laliotis has taken a closer look at 40 Eridani b and other stars identified based on radial velocity and found that a false signal is likely.
Several periodic signals that they have found around the star, they say, are fully consistent with stellar activity, such as magnetic cycles and stellar rotation, while others cannot be confirmed. because a region of stellar space cannot be observed during a large part of the earth’s year.
“Therefore,” they write in their paper, “we classify this as a false positive.”
They also discovered several other exoplanets that are also likely ghosts in the data. The radial velocity data interpreted to produce super-Earth exoplanets HD 20794 c and HD 85512 b were also false positives caused by stellar activity, the team says, and gas giant HD 114613 b also looks dubious.
On the other hand, on the other hand, the researchers were able to identify two new candidate exoplanets, followed by further observations and analysis to determine their nature.
So, swings and roundabouts; goodbye Vulcan, hello HD 192310 RV Signal IV and HD 146233 RV Signal III (they will probably come up with more catchy names later if the exoplanets are confirmed).
These results suggest that as we get more data and more detailed data, it’s worth going back to older, potentially ambiguous detections to clarify observed signals and make sure our detections of exoplanets are as clear as possible. In the process, we can also learn a lot about stellar activity.
“We anticipate that detecting and characterizing Earth-like planets will be an exceptionally challenging task due to issues related to observational limitations, instrument systematics, and, most importantly, the variability of the stars themselves,” the researchers wrote.
“Dedicated, high-frequency, high-precision radial velocity monitoring will allow characterization and potentially attenuation of signals of stellar variability over time. hours to years along with the discovery of additional, currently unknown planetary companions.
“Knowing how to properly model and remove both types of signals will be critical to any future effort to measure accurate terrestrial masses. planets.”
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