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Discovery Alert: Spock’s Home Planet Goes ‘Poof’

An artist’s conception of a previously proposed possible planet, HD 26965 b – often compared to the fictional “Vulcan” from the Star Trek universe.

Source: JPL-Caltech

Discovery

The planet that likely orbits the star 40 Eridani A – which hosts Mr. Spock’s fictional home planet, Vulcan, in the “Star Trek” universe – is actually a type of astronomical illusion caused by the pulsations and vibrations of the star itself, new research shows.

Key facts

The possibility of detecting a planet orbiting the star made famous by “Star Trek” generated excitement and a lot of attention when it was announced in 2018. Just five years later, the planet seemed to be on shaky ground as other researchers questioned its existence. Precision measurements made by the NASA-NSF instrument installed a few years ago atop Arizona’s Kitt Peak seem to have brought the planet Vulcan even more decisively into the realm of science fiction.

Details

Two methods for detecting exoplanets – planets orbiting other stars – dominate all others in the ongoing search for strange new worlds. The transit method, which involves observing a slight drop in a star’s light as a planet crosses the face of its star, is responsible for the vast majority of discoveries. However, the “radial velocity” method has also produced a significant share of exoplanet discoveries. This method is especially important for systems with planets that, from the Earth’s point of view, do not intersect the disks of their stars. By tracking subtle changes in starlight, scientists can measure the “wobbles” of the star itself as the gravity of the planet orbiting it tilts it this way and that. For very large planets, the radial velocity signal will mostly lead to an unambiguous detection of the planets. But not very large planets can be problematic.

Even the scientists who made the original possible detection of the planet HD 26965 b – almost immediately compared to the fictional Vulcan – warned that it could turn out to be chaotic oscillations of stars masquerading as a planet. They noted evidence of a “super-Earth” – larger than Earth, smaller than Neptune – moving in a 42-day orbit around a Sun-like star about 16 light-years away. The new analysis, using very precise radial velocity measurements that were not yet available in 2018, confirms that caution about a possible discovery was warranted.

Bad news for Star Trek fans comes from an instrument known as NEID, which recently joined the telescope complex at Kitt Peak National Observatory. NEID, like other radial velocity instruments, relies on the “Doppler” effect: shifts in a star’s light spectrum that reveal its wobbly motions. In this case, analysis of the planet’s alleged signal of different wavelengths of light emitted from different levels of the star’s outer shell, the photosphere, revealed significant differences between the measurements of individual wavelengths – their Doppler shifts – and the total signal when combined. This means that most likely the planet’s signal is actually the flickering of something on the star’s surface that coincides with the 42-day rotation – perhaps the swirling of warmer and cooler layers beneath the star’s surface, called convection, combined with features of the star’s surface such as sunspots and ” beaches” which are bright, active areas. Both can change the star’s radial velocity signals.

Although the new discovery, at least for now, robs the star 40 Eridani A of its possible planet Vulcan, the news is not all bad. The demonstration of such finely tuned radial velocity measurements holds the promise of making sharper observational distinctions between real planets and the vibrations and rattles on the surfaces of distant stars.

Fun facts

In the Star Trek universe, the destruction of Vulcan was even predicted. Vulcan was first identified as Spock’s home planet in the original 1960s television series. However, in the 2009 film “Star Trek,” a Romulan villain named Nero uses an artificial black hole to blow up Spock’s home world.

Explorers

A research team led by astronomer Abigail Burrows of Dartmouth College and formerly of NASA’s Jet Propulsion Laboratory published a paper describing the new result: “The death of Vulcan: NEID reveals that the planetary candidate orbiting HD 26965 is stellar activity” in the journal The Astronomical Journal in May 2024 (Note: HD 26965 is an alternative designation for the star 40 Eridani A.)

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