An extrasolar planet that has been compared to Spock’s homeworld of Vulcan in the Star Trek franchise may have been nothing more than an illusion caused by a jittery star.
The extrasolar planet or ‘exoplanet’ (a term for a planet outside our solar system) was proposed to orbit a star called 40 Eridani A or ‘Keid’, which is part of a triple star system located at approximately is 16.3 light-years from Earth. . In Star Trek, this star is also home to the planet Vulcan. The planet was first announced in 2018 and caused quite a stir thanks to its similarities to Spock’s fictional home planet.
A team of scientists led by astronomer Abigail Burrows of Dartmouth College now think that the ‘wobble’ of this planet’s parent star is not at all the result of an orbiting world pulling on it. Burrows and colleagues, using a NASA instrument called NEID, located at Kitt Peak National Observatory, discovered that the origin of this wobble is actually “pulses and jitters” from Keid himself.
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The fictional version of Vulcan was first introduced during Gene Roddenberry’s groundbreaking original series Star Trek, mentioned in the 1965 unaired pilot episode “The Cage”. In the JJ Abrams-directed 2009 Star Trek reboot, Vulcan was destroyed by a time-traveling enemy of Kirk, Spock and the rest of the Enterprise crew.
By wiping out the real Vulcan, officially named HD 26965 b, this new study 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 techniques take into account the effect of a planet orbiting its star.
The transit method, used with great success by NASA’s Transiting Exoplanet Survey Satellite (TESS), measures the small dips in light caused by a planet as it crosses the surface of its host star.
While the transit method is by far the more fruitful of these two exoplanet detection methods, the radial velocity method is useful for detecting exoplanets that do not pass between the leading edge of their star and our vantage point in the Solar System.
The radial velocity method uses small shifts in a star’s light as an orbiting planet gravitationally pulls on it. When a star is pulled away from Earth, the wavelength of the light it emits is stretched, causing it to move toward the “red end” of the electromagnetic spectrum, a phenomenon called “redshift.” The reverse happens when the star is pulled towards Earth, the wavelengths of light are compressed and the light is ‘blue shifted’ towards the ‘blue end’ of the electromagnetic spectrum.
This is analogous to the Doppler effect, which affects sound waves on Earth. When an ambulance rushes towards us, the siren’s sound waves are compressed, making them higher pitched. When the ambulance drives away, the sound waves are further apart and the siren becomes lower.
The radial velocity method is best for detecting particularly massive planets because they exert a greater gravitational force on their stars, thus generating a more pronounced shift in the starlight from that star body. However, it is less robust for detecting planets with masses lower than Jupiter, the solar system’s most massive planet.
When HD 26965 b was possibly first detected using the radial velocity method, its mass was estimated to be about 8 times greater than that of Earth, but less than that of Neptune, making it a so-called “super-Earth” planet. The fake Vulcan was suspected to orbit its parent star at about 22% of the distance between Earth and the Sun, completing a year in about 42 Earth days.
Yet even the scientists who discovered this planet warned that it could be a false detection caused by Keid’s inherent nervousness. In 2023, researchers had expressed major doubts about the existence of this exoplanet. These new high-precision radial velocity measurements, which were 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 was delivered by NEID, whose name rhymes with “fluid.” NEID is an instrument that uses radial velocity to measure the motion of nearby stars with extreme precision.
NEID divided the putative planetary signal into its component wavelengths that represent light emitted from different layers in the structure of Keid’s surface, or photosphere. This allowed the team to detect significant differences in the individual wavelengths compared to the total combined signal.
As a result, the signal suggested that HD 26965 b is actually the result of something flickering on Keid’s surface about every 42 Earth days. This effect can also be created when warm and cold plasma rises and falls through Keid’s convective zone and interacts with surface features such as dark sunspots or bright, active areas called ‘plages’.
While this discovery isn’t great news for Keid and his planetary prospects, or for Star Trek fans, it is a positive step for scientists hunting exoplanets.
That’s because NEID’s finely tuned radial velocity measurements promise that in the future, planetary signals can be more accurately separated and distinguished from the natural vibrations of stars.
The team’s research has been published in The Astronomical Journal.