A planet beyond the solar system that has been compared to Spock’s home world of Vulcan in the Star Trek series may be nothing more than an illusion caused by a strained star.
The extrasolar planet, or “exoplanet” (a term for a planet outside our solar system), is proposed to orbit a star called 40 Eridani A, or “Keid”, which is part of a triple star system located approximately 16.3 light-years from Earth. . In Star Trek, this star is also home to the planet Vulcan. The planet, which was first announced in 2018, made a lot of noise due to its similarities to Spock’s fictional home planet.
A team of scientists led by astronomer Abigail Burrows of Dartmouth College now thinks that the “wobble” of this planet’s parent star is not caused by an orbiting world pulling on it. Using a NASA instrument called NEID located at Kitt Peak National Observatory, Burrows and his colleagues discovered that the origin of this wobble was actually the “pulses and tremors” of Keid himself.
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The fictional version of Vulcan was first introduced during the seminal original series of Star Trek, mentioned in Gene Roddenberry’s unaired 1965 pilot episode “The Cage.” In the 2009 JJ Abrams-directed Star Trek reboot, Vulcan was destroyed by the time-traveling enemy of Kirk, Spock, and the rest of the Enterprise crew.
This new research on the real-life Vulcan, officially named HD 26965 b, shows that life sometimes imitates art.
Sorry Keid, you’re on your own…
There are several ways to detect exoplanets orbiting distant stars, but the two most successful techniques are the transit method and the radial velocity method. Both of these techniques take into account the impact of an orbiting planet on its star.
The transit method, used with great success by NASA’s Transiting Exoplanet Survey Satellite (TESS), measures the tiny dips in light caused by a planet as it passes across the face of its host star.
While the transit method is by far the more efficient of these two exoplanet detection methods, the radial velocity method is useful for detecting exoplanets that do not pass between the face of their star and our vantage point in the solar system.
The radial velocity method uses small shifts in the star’s light due to an orbiting planet gravitationally pulling on it. As a star moves further away from Earth, the wavelength of the light it emits is stretched, causing it to move toward the “red end” of the electromagnetic spectrum; This phenomenon is called “redshift”. The opposite occurs when the star is pulled towards the Earth, the wavelengths of light are compressed and the light “blueshifts” towards the “blue end” of the electromagnetic spectrum.
This is similar to the Doppler effect affecting sound waves on Earth. When an ambulance races towards us, the siren’s sound waves are compressed, causing it to sound higher pitched. When the ambulance speeds away, the sound waves become more spaced and the siren sounds lower.
The radial velocity method is best for detecting particularly large planets; because they exert a greater gravitational pull on their stars, thus creating a more pronounced shift in the starlight coming from that stellar body. But it is less robust at detecting planets with masses lower than that of Jupiter, the solar system’s largest planet.
When HD 26965 b was first potentially detected using the radial velocity method, its mass was estimated to be approximately 8 times greater than that of Earth but less than that of Neptune; This made it a planet called a “super Earth”. Pseudo-Vulcan was thought to orbit its parent star at a distance of about 22% of the distance between Earth and the sun, completing a year in about 42 Earth days.
But even the scientists who discovered this planet warned that this could be a misidentification caused by Keid’s innate nervousness. By 2023, researchers had raised great doubts about the existence of this exoplanet. These new high-precision radial velocity measurements, not yet available in 2018, are the final nail in the coffin of the Vulcan-like HD 26965 b.
The disappointing news for Star Trek fans came from NEID, whose name rhymes with the word “fluid”. NEID is an instrument that uses radial velocity to measure the motion of nearby stars with extreme precision.
NEID separated the suspected planet signal into component wavelengths that represent light emitted from various layers in the structure of Keid’s surface, or photosphere. This allowed the team to detect significant differences in individual wavelengths compared to the total combined signal.
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As a result, the signal implying the existence of HD 26965 b is actually the result of something vibrating on Keid’s surface approximately every 42 Earth days. This effect can also be created by warm and cold plasma rising and falling in Keid’s convection zone and interacting with surface features such as dark sunspot patches or bright, active regions called “beaches.”
While this discovery isn’t great news for Keid and his planetary prospects, or for Star Trek fans, it’s a positive step for exoplanet-hunting scientists.
This is because NEID’s fine-grained radial velocity measurements promise that in the future planetary signals can be more accurately separated and distinguished from the natural pulsations of stars.
The team’s research was published in The Astronomical Journal.