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By NASA
Artist’s concept of a young, newly discovered planet, exposed to observation by a warped debris disk. Credit: Robert Hurt, Caltech-IPAC. The discovery
A huge planet with a long name – IRAS 04125+2902 b – is really just a baby: only 3 million years old. And because such infant worlds are usually hidden inside obscuring disks of debris, it is the youngest planet so far discovered using the dominant method of planet detection.
Key facts
The massive planet, likely still glowing from the heat of its formation, lies in the Taurus Molecular Cloud, an active stellar nursery with hundreds of newborn stars some 430 light-years away. The cloud’s relative closeness makes it a prime target for astronomers. But while the cloud offers deep insight into the formation and evolution of young stars, their planets are usually a closed book to telescopes like TESS, the Transiting Exoplanet Survey Satellite. These telescopes rely on the “transit method,” watching for the slight dip in starlight when a planet crosses the face of its host star. But such planetary systems must be edge-on, from Earth’s vantage point, for the transit method to work. Very young star systems are surrounded by disks of debris, however, blocking our view of any potentially transiting planets.
A research team has just reported an extraordinary stroke of luck. Somehow, the outer debris disk surrounding this newborn planet, IRAS 04125+2902 b, has been sharply warped, exposing the baby world to extensive transit observations by TESS.
Details
While the warped outer disk is a great coincidence, it’s also a great mystery. Possible explanations include a migration of the planet itself, moving closer to the star and, in the process, diverging from the orientation of the outer disk – so that, from Earth, the planet’s orbit is edge-on, crossing the face of the star, but the outer disk remains nearly face-on to us. One problem with this idea: Moving a planet so far out of alignment with its parent disk would likely require another (very large) object in this system. None has been detected so far.
The system’s sun happens to have a distant stellar companion, also a possible culprit in the warping of the outer disk. The angle of the orbit of the companion star, however, matches that of the planet and its parent star. Stars and planets tend to take the gravitational path of least resistance, so such an arrangement should push the disk into a closer alignment with the rest of the system – not into a radical departure.
Another way to get a “broken” outer disk, the study authors say, would not involve a companion star at all. Stellar nurseries like the Taurus Molecular Cloud can be densely packed, busy places. Computer simulations show that rains of infalling material from the surrounding star-forming region could be the cause of disk-warping. Neither simulations nor observations have so far settled the question of whether warped or broken disks are common or rare in such regions.
Fun facts
Combining TESS’s transit measurements with another way of observing planets yields more information about the planet itself. We might call this second approach the “wobble” method. The gravity of a planet tugs its star one way, then another, as the orbiting planet makes its way around the star. And that wobble can be detected by changes in the light from the star, picked up by specialized instruments on Earth. Such “radial velocity” measurements of this planet reveal that its mass, or heft, amounts to no more than about a third of our own Jupiter. But the transit data shows the planet’s diameter is about the same. That means the planet has a comparatively low density and, likely, an inflated atmosphere. So this world probably is not a gas giant like Jupiter. Instead, it could well be a planet whose atmosphere will shrink over time. When it finally settles down, it could become a gaseous “mini-Neptune” or even a rocky “super-Earth.” These are the two most common planet types in our galaxy – despite the fact that neither type can be found in our solar system.
The discoverers
A science team led by astronomer Madyson G. Barber of the University of North Carolina at Chapel Hill published the study, “A giant planet transiting a 3 Myr protostar with a misaligned disk,” in the journal Nature in November 2024.
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By European Space Agency
The two CubeSat passengers aboard ESA’s Hera mission for planetary defence have exchanged their first signals with Earth, confirming their nominal status. The pair were switched on to check out all their systems, marking the first operation of ESA CubeSats in deep space.
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By European Space Agency
ESA’s Hera mission for planetary defence has taken its first images using three of the instruments that will be used to explore and study the asteroids Dimorphos and Didymos.
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By European Space Agency
Image: On 20 September, the Copernicus Sentinel-2C satellite captured its first stunning image of the Moon, achieved by rolling the satellite sideways in a unique manoeuvre. Although Sentinel-2C is primarily designed for Earth observation, this image – intended for calibration and cross-mission comparisons – exceeded expectations. View the full article
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By NASA
Artist’s concept of a previously proposed possible planet, HD 26965 b – often compared to the fictional “Vulcan” in the Star Trek universe. Credit: JPL-Caltech The discovery
A planet thought to orbit the star 40 Eridani A – host to Mr. Spock’s fictional home planet, Vulcan, in the “Star Trek” universe – is really a kind of astronomical illusion caused by the pulses and jitters of the star itself, a new study shows.
Key facts
The possible detection of a planet orbiting a star that Star Trek made famous drew excitement and plenty of attention when it was announced in 2018. Only five years later, the planet appeared to be on shaky ground when other researchers questioned whether it was there at all. Now, precision measurements using a NASA-NSF instrument, installed a few years ago atop Kitt Peak in Arizona, seem to have returned the planet Vulcan even more definitively to the realm of science fiction.
Details
Two methods for detecting exoplanets – planets orbiting other stars – dominate all others in the continuing search for strange new worlds. The transit method, watching for the tiny dip in starlight as a planet crosses the face of its star, is responsible for the vast majority of detections. But the “radial velocity” method also has racked up a healthy share of exoplanet discoveries. This method is especially important for systems with planets that don’t, from Earth’s point of view, cross the faces of their stars. By tracking subtle shifts in starlight, scientists can measure “wobbles” in the star itself, as the gravity of an orbiting planet tugs it one way, then another. For very large planets, the radial velocity signal mostly leads to unambiguous planet detections. But not-so-large planets can be problematic.
Even the scientists who made the original, possible detection of planet HD 26965 b – almost immediately compared to the fictional Vulcan – cautioned that it could turn out to be messy stellar jitters masquerading as a planet. They reported evidence of a “super-Earth” – larger than Earth, smaller than Neptune – in a 42-day orbit around a Sun-like star about 16 light-years away. The new analysis, using high-precision radial velocity measurements not yet available in 2018, confirms that caution about the possible discovery was justified.
The bad news for Star Trek fans comes from an instrument known as NEID, a recent addition to the complex of telescopes at Kitt Peak National Observatory. NEID, like other radial velocity instruments, relies on the “Doppler” effect: shifts in the light spectrum of a star that reveal its wobbling motions. In this case, parsing out the supposed planet signal at various wavelengths of light, emitted from different levels of the star’s outer shell, or photosphere, revealed significant differences between individual wavelength measurements – their Doppler shifts – and the total signal when they were all combined. That means, in all likelihood, the planet signal is really the flickering of something on the star’s surface that coincides with a 42-day rotation – perhaps the roiling of hotter and cooler layers beneath the star’s surface, called convection, combined with stellar surface features such as spots and “plages,” which are bright, active regions. Both can alter a star’s radial velocity signals.
While the new finding, at least for now, robs star 40 Eridani A of its possible planet Vulcan, the news isn’t all bad. The demonstration of such finely tuned radial velocity measurements holds out the promise of making sharper observational distinctions between actual planets and the shakes and rattles on surfaces of distant stars.
Fun facts
Even the destruction of Vulcan has been anticipated in the Star Trek universe. Vulcan was first identified as Spock’s home planet in the original 1960s television series. But in the 2009 film, “Star Trek,” a Romulan villain named Nero employs an artificial black hole to blow Spock’s home world out of existence.
The discoverers
A science team led by astronomer Abigail Burrows of Dartmouth College, and previously of NASA’s Jet Propulsion Laboratory, published a paper describing the new result, “The death of Vulcan: NEID reveals the planet candidate orbiting HD 26965 is stellar activity,” in The Astronomical Journal in May 2024 (Note: HD 26965 is an alternate designation for the star, 40 Eridani A.)
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