Direct imaging of 14 Herculis c by the James Webb Space Telescope.

The planet 14 Herculis c was discovered by the ELODIE Planet Search Survey in 2005, using the radial velocity method, which it was detected by the gravitational effect it has on its host star, 14 Herculis A, as these cause the star to wobble slightly on its axis. 14 Herculis is the outermost of two known planets in the 14 Herculis system, the other being 14 Herculis b. The star 14 Herculis A is a K-type orange dwarf star, slightly smaller than the Sun, 58.4 light years from our Solar System in the constellation of Hercules. The planet 14 Herculis c orbits this star at about 20 AU (i.e. about 20 times the average distance between the Earth and the Sun), with a orbital period of 152.8 years. It is estimated to be about the same size as Jupiter, but much more massive. This is due to the distance at which it orbits its star, which makes it much cooler than Jupiter, making the gasses from which it is made more dense.

Although several subsequent studies have confirmed the existence of 14 Herculis c, the planet had never been directly imaged. This changed in 2025, when the James Webb Space Telescope's Near Infrared Camera was trained upon the 14 Herculis system. The Webb study also enabled the direct measurement of the planet's temperature for the first time, showing that it's average surface temperature may be around -3°C.

14 Herculis c. The view is mostly black, with very faint red splotches in the central region of the image. At the center of the image, there is a black circle, and in the center of that, there is a star symbol representing a real star. This black circle blocks the light from the host star. To the lower right of the circle is a fuzzy bright orange circle, which is the exoplanet. NASA/ESA/CSA/STScl/William Balmer/Daniella Bardalez Gagliuffi.

14 Herculis c was imaged at 4.44 microns, an infrared wavelength equivalent to a temperature of -3°C. Although this was the predicted temperature for the exoplanet, it was found to be much dimmer than expected. This is theorized to indicate a much more active atmosphere than predicted, with warmer gas molecules from the planet's interior being brought to the surface rapidly due to internal churning.

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Direct imaging of a possible planet orbiting the fast moving star HIP 36277.

In the past three decades almost six thousand exoplanets (planets orbititing stars other than our Sun) have been detected, using a variety of methods. Direct imaging has proven to be a useful technique for detecting planets with masses greater-than-or-equal-to that of Jupiter at distances of more than 10 AU from their host stars (i.e. more than ten times as far from their host stars as the Earth is from the Sun). Notable planets discovered in this way include 51 Eridani b, which has a mass 2.6 times that of Jupiter and orbits a star 96 light years from Earth in the constellation of Eridanus at a distance of 11.1 AU, HIP 65426 b (formally named Najsakopajk), which has a mass 7.1 times that of Jupiter, and orbits a star 385 light years from Earth in the constellation of Centaurus at a distance of 87 AU, and PDS 70 b and PDS 70 c, which have masses of 3.2 and 7.5 times that of Jupiter, and orbit a star 370 light years from Earth in the constellation of Centaurus at distances of 20.8 and 34.3 AU, respectively.

However, large planets at large separations from their host stars are relatively rare, which means that a large number of stellar systems have to be surveyed in this way in order to detect a few planets. Most giant planets known orbit their host stars at distances of 1-3 AU, which would make direct imaging them with current technology impossible if they are more than about 50 parsecs (163.1 light years) away from us. 

The radial velocity method uses the movement of stars to detect to infer the presence of companions. This has proven very effective as a  way to detect very large planets close to stars, such as Beta Pictoris c, which has a mass about nine times that of Jupiter, and orbits a star 63 light years from Earth in the constellation of Pictor at a distance of about 2.7 AU, or HD206893 c, which has a mass about 12.7 times that of Jupiter, and orbits a star 125 light years from  Earth in the constellation of Capricornus,  at a distance of 3.53 AU.

The proper motion anomaly method can identify potential companions to stars by measuring their parallax (the amount they move in a year because we are observing them from different points on the Earth's orbit) over several years; if the star moves more than predicted (i.e. anomalously), then this is likely to be because of an unseen companion moving the star. This method has been used to identify several potential planets which have subsequently been directly imaged. These include HIP 99770 b, which has a mass of about 16 times that of Jupiter, and which orbits a star 133 light years from Earth in the constellation of Cygnus at a distance of 17 AU, AF Leporis b, which is 2-5 times the mass of Jupiter and orbits a star 87.5 light years from Earth in the constellationof Lepus, as well as the brown dwarf HD21152 B, which has a mass 22-36 times that of Jupiter, and which orbits a star 150 light years from Earth in the constellation of Taurus at a distance of about 18 AU.

In a paper published in the Monthly Notices of the Royal Astronomical Society on 9 December 2024, a team of astronomers led by Dino Mesa of the Osservatorio Astronomico di Padova present the results of a study which targeted three stars in the Hipparcos-Gaia PMa catalogue identified as having proper motion anomalies with the SHARK-NIR coronagraphic camera and LMIRCam camera and coronagraph of the Large Binocular Telescope in Arizona. 

Because they were interested in planetary-sized companion bodies, rather than secondary stars, Mesa et al. looked for stars which showed small proper motion anomalies, and because they wished to be able to image bodies within 10 AU of their host star, they restricted themselves to objects within 50 parsecs (163 light years) of the Earth.

The first star selected, HIP 11696 A (also known as HD 15407 A) is an F-type (yellow-white dwarf) star with a mass about 1.40 times that of our Sun, 49.3 parsecs (160.8 light years) from Earth in the constellation of Persius. HIP 11696 is a young star, which has been estimated to be about 80 million years old, although it is also thought likely to be a member of the AAB Doradus Moving Group, which would make it between 125 and 149 million years old. Mesa et al. use an intermediate age of 137 million years for their calculations in their study.

HIP 11696 A has a companion star, HIP 1696 B, which is a K-type (orange dwarf) star with about 80% of the mass of our Sun, separated by about 1000 AU - far enough to be excluded from the field of view of the SHARK-NIR instrument. HIP 11696 A appears to be producing an unusual amount of light in the mid-infrared range, which may be indicative of a recent collision between rocky planets of planetary embryos in the inner part of the system. A debris disk has been detected at a distance of 0.6-1.0 AU from the star, which makes it unlikely that there are any massive planets orbiting close to the star. Nevertheless, an anomaly in the motion of HIP 11696 A which could not be explained by the presence of HIP 11969 B was detected. It has been suggested that this might be caused by a planet with a mass about 6.39 times that of Jupiter orbiting at 3 AU from HIP 11696 A, or a planet with a mass about 16.6 times that of Jupiter orbiting at about 30 AU from the star.

HIP 11696 A was observed with the SHARK-NIR and LMIRCam instrument on the night of 28 October 2023. Mesa et al. detected a bright object to the southeast of the star at a distance of 1.5" (1.5 arc seconds; the sky can be imagined as a sphere surrounding the Earth, divided into 360 degrees (°), with each degree divided into 60 arc minutes (') and each arc minute divided into 60 arc seconds (")). However, this object was also imaged previously by the Keck II telescope in November 2009, and the Gemini North Telescope in August 2013, with no movement relative to HIP 11696 A between these images, leading Mesa et al. to conclude that this is in fact a background object rather than a planetary companion to the star. Based upon this inability to image a planet close to the star, Mesa et al. calculate that if a planet is responsible for the observed wobble in HIP 11696 A's orbit, then this is likely to be between 2.5 and 28 AU from the star, and have a mass 4-16 times that of Jupiter.

(Top) Final image obtained for HIP 11696 using SHARK-NIR data. This image was obtained by applying a PCA method subtracting 5 principal components. (Bottom) Final image obtained for HIP 11696 using LMIRCam data. In this case, a PCA method subtracting 10 principal components was applied. In both cases, a bright candidate companion is visible South-East from the star. Because the image is looking up, the positions of east and west are reversed. Mesa et al. (2024).

The second star identified, HIP 47110 A (also known as HD 82939 A) is a G-type (yellow dwarf) star with about 98% of the mass of our Sun, 38.7 parsecs (126.2 light years) from Earth in the constellation of Leo Minor. HIP 47110 A has been identified as a possible member of the Pleiades Moving group, with an age of approximately 112 million years.

HIP 47110 A has a companion star, HIP 47110 B, which is a M-type (red dwarf) star with a separation of larger than 162" (interpreted to be more than 6280 AU), enabling it to be excluded from the field of vision. Again, there is an anomaly in the motion of HIP 47110 A which cannot be explained by the presence of HIP 447110 B, and which has been hypothesized to be caused by a planet. It has been suggested that this might be caused by a planet with a mass about 2.5 times that of Jupiter orbiting at between 5 and 10 AU from HIP 47110 A, or a planet with a mass about 11.35 times that of Jupiter orbiting at about 30 AU from the star.

HIP 47110 A was observed on the night of 20 February 2024, but no potential companion was observed. Based upon this, Mesa et al. exclude the possibility of a planet close to star, calculating that the observed orbitary wobble must be caused by a planet between 3 and 30 AU from the star with a mass of between 2 and 10 times that of Jupiter.

The third star in the study, HIP 36277, is a K-type (orange dwarf) star with a mass 0.67 times that of our Sun, located 46.3 parsecs (151 light years) from the Earth in the constellation of Dorado. HIP 36277 was identified as a young runaway star (star which has been ejected from the star cluster which birthed it, and which is therefore travelling at a high speed in a distance at odds with galactic rotation) with an age of about 41.2 million years. However, spectrographic analysis of the star has suggested a much older age, most probably more than a billion years old and possibly more than 10 billion years. 

An anomaly on the motion of HIP 36277, which has been interpreted as potentially due to a planet with a mass 2.3 times that of Jupiter at a distance of 5 AU from the star, 2.64 times that of Jupiter at 10 AU from the star, or 15.18 times the mass of Jupiter at 30 AU from the star.

HIP 36277 was observed on the night of 21 February 2024, with a bright object observed to the southeast of the star in both SHARK-NIR and LMIRCam images. This body could also be identified in images from the Gaia space telescope, with similar parallax and proper motion values, which demonstrates physical association with the star. The object is separated from the star by 1.9". The precise size of this object is difficult to calculate, given the uncertainty of the age of the star, but Mesa et al. calculate that if the star is 41 million years old, then it would have a mass of between 16.2 and 73.9 times that of Jupiter (with a median value of 37.8 Jupiter masses), making it most likely a brown dwarf companion to the star (brown dwarfs are objects intermediate to stars and planets in size; they are not large enough to fuse ordinary hydrogen in their cores, but are large enough to fuse the heavier isotope deuterium). However, if the star is about five billion years old, then the body is likely to have a mass about 0.1 times that of our Sun, making it a small M-type (red dwarf) star. 

A second object was also visible in the SHARK-NIR data, but not observed by LMIRCam. This object is to the south of the star, and separated by about 0.0625", which Mesa et al. calculate to be equivalent to about 28.9 AU. Again, the mass of such an object would be dependent on its age, with a 41-million-year-old object having a mass about 7.6 times that of Jupiter, making it a large planet, while at 5 billion years old it would have a mass between 65.9 and 72.1 times that of Jupiter, again indicative of a brown dwarf.

(Top) Final image obtained for HIP 36277 using SHARK-NIR data. This image was obtained by applying a PCA method subtracting 5 principal components. (Bottom) Final image obtained for HIP 36277 using LMIRCam data. In this case, a PCA method subtracting 10 principal components was applied. In both cases, a bright candidate companion is visible southeast from the star. Furthermore, in the SHARK-NIR image, a possible fainter object is visible just south of the star. Mesa et al. (2024).

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A new image of the Beta Pictoris system.

The European Space Agency has released a new image of the Beta Pictoris, as seen by the James Webb Space Telescope, in a press release issued on 10 January 2024. The image shows the two main debris disks of the system, which are offset from one another by about 5°, as well as a new and previously unseen feature, which has been named the 'Cat's Tail'.

The Beta Pictoris System. European Space Agency.

Debris disks are rings of dust, rock and icy material left surrounding stars after planet formation has occurred (unlike protoplanetary disks, which are present around very young stars only, and which are thought to be largely consumed by planetary formation). Our Solar System has two such debris disks, the Asteroid Belt and the Kuiper Belt, and in recent years improved telescope technology has allowed astronomers to detect debris disks around about 80 of other stars. Most of these disks have been detected only at infrared wavelengths; imaging disks at visual wavelengths enables astronomers to study the morphology and composition of such disks in far greater detail, enabling them to predict the presence of planets that cannot be directly detected and better understand planetary formation around other stars.

Beta Pictoris is a young star 62.4 light years from Earth in the constellation Pictor. Although it is thought to be only 20-25 million years old, it is 1.75 times as massive as the Sun, and therefore 8.7 times as luminous. 

The main debris disk of Beta Pictoris was discovered in 1983 by the Infrared Astronomical Satellite, one of the first extra-Solar debris disks ever discovered. This disk is seen edge-on from the Earth, and extends about 1835 from the star (i.e 1835 times as far from the star as the Earth is from the Sun), with the northeast arm rotating towards us and the southwest arm rotating away.

In 2006 the Hubble Space Telescope discovered as much fainter secondary debris disk around Beta Pictoris, offset by about 5° from the main disk. This secondary disk extends about 130 AU from the star, and is thought to be caused by a massive planet deflecting material from the main disk onto an orbit aligned with its own. 

The precise nature of the Cat's Tail is unclear, but in 2014 the Atacama Large Millimeter/submillimeter Array detected a clump of carbon monoxide at a similar location. The high levels of radiation emitted by the star should break down carbon monoxide quite quickly, suggesting that the gas was a result of a recent event. The Cat's Tail is thought to be comprised of dusty material, with an equivalent mass similar to that of a large body in the Main Asteroid Belt of our Solar System, spread our over a distance of about 16 billion km (107 AU). This is probably only offset from the main debris disk by about 5°, but appears curved because of the rotation of the system. It is likely that the dust of the Cat's Tail and the carbon monoxide clump detected by the Atacama Large Millimeter/submillimeter Array are the result of a single, catastrophic event.

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Using lab-based experiments to estimate the composition of the HR 4796 debris disk.

The appearence of debris disks is an important stage in the evolution of young planetary systems, occurring after the dissipation of the gas-rich protoplanetary disk has left an optically thin disk of planetesimals that are the leftovers from the planetary formation. This disk in turn depletes with time, as the number of planitesimals declines, which 75% of young stars in the 18-million-year-old β Pictoris moving group having a detectable debris disk, compared to 20% of billion-year-old stars. Debris disks can be detected through their infrared emmissions, which are in excess of those produced by the stellar photosphere.

The A-type star HR 4796 is 231 light years from our Solar System in the constelation of Centurus. It is estimated to be 10 million years old, and has one of the best known debris disks, which has been studied with numerous different instruments. The ring is about 80 AU from the star (i.e. 80 times as far from the star as the Earth is from the Sun) and extends for about 10 AU. 

In a paper posted on the Arxiv database at Cornell University on 4 December 2023, Julien Milli and Olivier Poch of the Université Grenoble Alpes, Jean-Baptiste Renard of the Université d'Orléans, Jean-Charles Augereau and Pierre Beck, also of the Université Grenoble Alpes, Elodie Choquet and Jean-Michel Geffrin of Aix Marseille Université, Edith Hadamcik of Sorbonne Université, Jérémie Lasue of the Université de Toulouse, François Ménard and Arthur Péronne, again of the Université Grenoble Alpes, Clément Baruteau, also of the Université de Toulouse, and Ryo Tazaki and Vanesa Tobon Valencia, once again of the Université Grenoble Alpes, present the results of a laboratory experiment intended to use dust analogues, to determine the nature of the material in the debris disk of HR 4796.

Examination of the HR 4796 system with the SPHERE instrument at the European Southern Observatory and the GPI instrument at the International Gemini Observatory has enabled polemetric analysis of the brightness of the ring at almost all azimuth angles. Every point on the ring forms a distinct angle between the light source (i.e. the star at the centre of the system) and the viewer, giving a different light scattering angle. The ring is angles at 76.5° to the star from our perspective, giving it minor axes (shortest apparent circumferances) with scattering angles of  13.5° to the northwest (brightest point) and 166.5° to the southeast (faintest point).

The HR 4796 disc at various wavelengths. The semi-major axis of the disc is roughly 1”. North is up, East to the left. Milli et al. (2023).

Most models of debris disks have assumed that they are made up of compact spheres of material similar to that found in comets, i.e. silicates, amorphous carbon, water ice and pore spaces. However, such models cannot reproduce the refractive properties of the HR 4796 disk. Changing the model to assume that the disk contained a high volume of metalic iron, as well as amorphous carbon and silicates, can reproduce the light scattering of the debris disk, but not the degree of polarisation. This suggests that either the particles in the disk are not spheres, or that the presumed size distribution of those spheres is very wrong. For most possible compositions of material, the degree of polarisation could be achieved only with milimetre sized particles, while the spectral energy distribution requires micron-scale particles.

The PROGRA² instrument is dedicated to the study of light scattered by solid particles deposited on a surface or lifted in clouds in microgravity conditions during parabolic flights that took place between 2018 and 2021. Samples were contained in a vial, and targetted with laser light; the scattered light produced by the particles was then split using a polarised beam splitter in two channels, and measured by two different detectors. 

Examination of the database of results produced by this experiment revealed that the iron sulphide mineral pyrrhotite produced a degree of polarisation similar to that seen in the HR 4796 debris disk with particle sizes in the 1-200 µm range. The experiment did not record the degree of light scattering in the near infra-red, which would be necessary for a rigorous comparison, but the scattering at visible wavelengths was a good match for the HR 4796 disk.

Milli et al. postulate that pyrrhotite is an interesting candidate for the material of the HR 4796 debris disk. Because the data comes from an archived result from an experiment not designed to model the disk, it was not adjusted to try to gat a better fit. Nevertheless, it does appear that a cloud of pyrrhotite particles dominated by particles smaller than 100 µm, would produce a good match for the optical properties of the HR 4796 disk. Iron sulphide minerals are an unsurprising component for a circumstellar dust ring. Stratospheric dust particles, Antarctic Micro-Meteorites, and sampled material from Comet Wild 2 have all produced iron sulphide minerals, and comet 67P/Churyumov-Gerasimenko has been shown to contain about 7.5% iron, probably in the form of iron sulphides or iron-nickel alloys. These are dark minerals, responsible for the dark reflectance at optical and near infrared wavelengths from  cometary and primitive asteroids surfaces, and would therefore be plausible components of the HR 4796 debris disk. 

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Looking for close encounters between the Sun and other stars.

Close encounters between stars have the potential to alter the evolution of planetary systems. This is particularly true in the early stages of their development, when planets are forming from circumstellar discs, a process which could easily be disrupted by an encounter with another star, but still applies later in a system's history, as most stars are thought to be surrounded by a loosely bound body of comets similar to our Oort Cloud, from which bodies could be disrupted sending them into the inner stellar system, potentially leading to impacts on the surface of planets, with a profound impact on any life their. A close star could also potentially go supernova, with even more devastating effect.

Clearly this makes close encounters between the Sun and other stars of great interest to scientists studying the history of the Solar System, who have speculated about such encounters for many years. Serious attempts at calculating the frequency of such close encounters has been possible only since 1997, when the Hipparcos star catalogue was produced, which for the first time included the parallaxes of over 118 000 stars. Two decades this became a much more realistic task with the production of the much more detailed Gaia catalogue, the development of software capable of analysing such large amounts of data, and the wider availability of computers capable of running such software.

Since its original release Gaia has been updated twice, with the current catalogue containing information on the movements of about 34 million bright stars.

In a paper published on the arXiv database at Cornell University on 14 July 2022, and accepted for publication in The Astrophysical Journal Letters, Coryn Bailer-Jones of the Max Planck Institute for Astronomy uses data from the latest version of the Gaia catalogue to produce a list of stars likely to have passed within 1 parsec (3.26 light years) of the Sun within about 6 million years of the current date. 

Bailer-Jones notes that some previous attempts at producing lists of close encounters have used limits greater than 1 parsec, but considers that since our current closest neighbour, the Alpha Centauri system, is only 1.3 parsecs (4.24 light years) away, 1 parsec seems a more useful upper limit. The Oort Cloud is currently thought extend to somewhere between 0.25 and 0.5 parsecs (0.82 and 1.63 light years) from the Sun, so stars coming closer than 1 parsec might be presumed to be starting to have some impact upon this cloud. The degree of error present in the Gaia catalogue makes calculation of encounters more than 6 million years into the past or future unreliable. Finally, the Gaia catalogue only includes stellar bodies larger than 0.12 times the mass of the Sun, so it is likely that other encounters with smaller stars (which are numerous) will have been missed.

Bailer-Jones's eventual list includes 61 stars, all currently within 380 parsecs (1329 light years) of the Sun, and with an average distance of 100 parsecs (326 light years), although he notes that this cannot be seen as a definitive list, and is likely to contain inaccuracies, particularly in the case of binary stars, which tend to have more complicated movement patterns, harder to calculate, and White Dwarf stars, which are notoriously hard to track. The list also includes two very young pre-main sequence stars, which may not have existed at all at the times when they theoretically came close to the Sun. 

Perihelion (encounter) times and distances for the 61 stars that have a median perihelion distance below 1 parsec. Negative times indicate past encounters, positive times future ones. The circles/squares show the median of the perihelion time and distance distributions computed from the 1000 data resamples (surrogates); the error bars show the 5th and 95th percentiles. Circles denote good encounters; squares denote the questionable encounters. The colour of each point indicates the median encounter velocity; those faster than 100 km per second are white. Bailer-Jones (2022).

Of the 61 stars for which an encounter closer than 1 parsec could be predicted, only 13 are predicted to come within 0.5 parsecs (1.63 light years).

The first star on Bailer-Jones's list is Gliese 710 (DR3 4270814637616488064 on the Gaia catalogue, and HIP 89825 on the Hipparcos catalogue). Gliese 710 is a K Class Orange Dwarf Star with approximately 70% of the Sun's mass, currently 19.1 parsecs (62.3 light years) from our Solar System in the constellation of Serpens. This star was first identified as likely to have a future close encounter with our Solar System in 1999, when it was calculated that it could potentially reach 0.34 parsecs from the Sun in 1.36 million years time. Since this first analysis Gliese 710 has been the subject of considerable interest to astronomers, and the time and distance of such a close encounter has been revisited several times. Bailer-Jones's new analysis is the most detailed yet, and calculates that the star may come to 0.064 parsecs (0.21 light years, or 13 200 astronomical units) in 1.29 million years. This is too distant to have any significant effect on the orbit of Pluto, but could potentially influence comets in the outer Oort Cloud quite severely. 

The second star on the list is HD 7977 (DR3 510911618569239040 on the Gaia catalogue), a G Class Yellow Dwarf Star with about 1.2 times the mass of the Sun, currently 75.6 parsecs (246.7 light years) from the Solar System in the constellation of Cassiopeia. This was first identified as likely to have a close encounter with the Sun by Bailer-Jones in 2018, when he calculated that it reached 0.43 parsecs (1.4 light years) from the Sun about 2.76 million years ago. The new data lowers this distance considerably, to 0.064 parsecs (0.21 light years).

The third star on the list is UPM J0812-3529 (DR3 5544743925212648320 on the Gaia catalogue), which was first identified as a nearby White Dwarf Star in 2018, but which has not previously been included in any study of potential close encounters. Bailer-Jones calculates that this star could reach 0.11 parsecs (0.36 light years) from the Sun in 29 000 years time. However, as previously noted, the distance and velocity of White Dwarf stars is notoriously hard to calculate, and the assumed timing and distance of approach for UPM J0812-3529 is based on current estimates that the star is 11.2 parsecs (36.5 light years) away, and travelling at a speed relative to the Sun of 374 km per second, both of which are uncertain, with the later being suspiciously large. This said, Bailer-Jones points out that a lower relative speed could lead to a closer encounter.

The fourth star on the list is UCAC4 689-035468 (DR3 213090546082530816 on the Gaia catalogue), another star identified as likely to have a close encounter with the Sun by Bailer-Jones in 2018, but for which the distance of this approach has been considerably reduced, from 1.44 parsecs (4.7 light years) in 2018 to 0.248 parsecs (0.81 light years) now, with such an encounter happening in 8.3 million years.

The fifth star on the list is identified on the Gaia catalogue as DR3 5571232118090082816, and is predicted to have come to 0.26 parsecs (0.85 light years) from the Sun 1.16 million years ago.

The sixth star on the list CD-25 8217 (DR3 5469802896279029504 on the Gaia catalogue), is also the latest possible encounter on the list, potentially reaching 0.35 parsecs (1.14 light years) from the Sun in 11.12 million years time. This is also predicted to be the slowest encounter on the list, both factors arising from its low relative velocity, approaching the Sun at only 3.2 km per second.

The seventh star on the list, identified as DR3 3372104035275483392 in the Gaia catalogue, is predicted to reach 0.36 parsecs (1.17 light years) from the Sun in 1.71 million years time.

The eighth star on the list, identified on the Gaia catalogue as DR3 3207963476278403200 is predicted to have reached 0.36 parsecs from the Sun 514 000 years ago, although Bailer-Jones identifies this as somewhat suspicious; the star is apparently above the main sequence, with a suspiciously high relative velocity and a fainter star behind it. This may in fact be a pre-main sequence star with a close companion, in which case the assumptions about it's movement would be quite wrong.

The ninth star on the list, identified as DR3 3106500096597409792 on the Gaia catalogue, is predicted to have reached 0.37 parsecs (1.19 light years) from the Sun 8.7 million years ago.

The tenth star on the list, DR3 4763293626627587840 is predicted to reach 0.45 parsecs (1.47 light years) from the Sun in 1.54 million years time.

The eleventh star on the list, DR3 929788371508812288 is predicted to have come to 0.46 parsecs (1.51 light years) of the Sun 364 000 light years ago.

The twelfth star on the list, DR3 6913732624445112832 is predicted will reach 0.46 parsecs from the Sun in 2.9 million years.

The thirteenth star on the list, DR3 3118526069444386944 is a young stellar object previously calculated to have reached 1.03 parsecs (3.36 light years) from the Sun, a distance now reduced to 0.49 parsecs (1.6 light years). However, this body is now considered to be a close binary star, and Bailer-Jones considers that this makes calculations of its velocity highly unreliable.

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Does the Nebra Disc represent a Bronze Age supernova?

Discovered with a hoard of Bronze Aged weapons in 1999 by two metal-detectorists in a prehistoric enclosure in the Ziegelroda Forest, 60 km west of Leipzig in the German State of Saxony-Anhalt, and subsequently traded several times on the black market before coming to the notice of archaeologists, the Nebra Disc is now considered to be one of the oldest known depictions of celestial objects. 

The disc depicts a cluster of stars, which can be confidently identified as the Pleiades flanked by a disc interpreted as the Sun and a crescent interpreted as a waning Moon, against a starry background with a blue-green patina. Additional arcs are present on two edges of the disc, although these are now thought to have been added later. Organic material found with the disc has been carbon dated to 1600-2000 BC, while material adhered to one of the swords found with it has been dated to between 1600 and 1560 BC. This gives an estimated burial time for the object, although the disc is likely to be older. Its style of manufacture has been linked to the Unetice Culture, which was found in Central Europe between about 2300 and 1600 BC. 

X-ray fluorescence trace element analysis of the metals used in the disc has suggested that the copper used in its manufacture originated from  Bischofshofen in Austria, the gold of the outer crescents (thought to have been added later) probably came from the Carpathian Mountains, while the gold of the original stars and discs probably came from Cornwall. 

The disc was clearly a high value object, with considerable effort and resources going into its manufacture, and therefore is likely to have had specific meaning for its makers, but that meaning remains obscure to us today. The objects at its centre have clearly been chosen carefully, yet their conjunction is highly unlikely. A waning Moon would not occur close to a Sun-disc in nature; the Moon does occasionally pass close to, or even in front of, the Sun, but is always in the New Moon (invisible) phase, as all the phases of the Moon are driven by reflected sunlight. This has led to the conclusion that the selection of objects is purely symbolic in nature, not directly related to a specific observation.

In a paper published in the Journal of Anthropological and Archaeological Sciences on 24 March 2022, Rosario Gianluca Pizzone and Roberta Spartá of the Laboratori Nazionali del Sud at the Istituto nazionale di fisica nucleare, make the proposal that the large disc seen on the Nabra Disc does not in fact represent the Sun, but is instead a depiction of a supernova explosion.

The Nebra disc as it appears now (on display in Halle Museum of Prehistory). The Pleiades cluster shows up in the top part, amid the golden disc and the waning Moon. The solar arcs on the right and bottom of the picture were added in a post-construction phase (see text for details). Pizzone & Spartá (2022).

Pizzone and Spartá note that the large gold disc is depicted in a part of the sky (the Auriga-Taurus astersim) known to be very active in terms of stellar formation and supernova explosions (the two are connected, with the largest stars, which are the ones that undergo such explosions, having very short lives). This area contains a number of supernova remnants, and is home to the only historically recorded supernova explosion, which led to the formation of the Crab Nebula in 1054 and was recorded by Chinese scholars.

Armed with this knowledge, Pizzone and Spartá conducted a survey of the Auriga-Taurus asterism, looking for young supernova remnants which might be associated with the event depicted on the Nebra Disc. This survey uncovered five such young supernovae. The first of these, SH2 224, is estimated to be between 13 000 and 24 000 years old, and is located 4500 parsecs (1470 light years) from our Solar System. The second, SH2 221 (HB9) is estimated to be 4000-6600 years old and is roughly 800 parsecs (2600 light years) away. The third, Semeis 147, is thought to be 30 000-40 000 years old and is 1200-1500 parsecs (3900-4500 light years away). The fourth, the Crab Nebula, can be precisely dated at 966 years old, and is 2000 parsecs (6500 light years) away. The final object, IC443, is between 3000 and 30 000 years old, and located 1500 parsecs (4500 light years) from us.

Pizzone and Spartá observe that one of these supernovae, SH2 221 (HB9) has a lower age range which coincides roughly with the possible creation of the Nebra Disc. They estimate, from the size of this object and its estimated distance, that at its peak this explosion would have been as bright as the Full Moon, a striking event which would likely have been seen as being of great importance to any Bronze Age European observers. 

They further note that several stone carvings, of roughly the same age, in the Burzahom archaeological site in Srinagar, Jammu and Kashmir, India, depict stick figures observing two light-emitting objects in the sky. The precise meaning of these has also been debated, with the objects possibly being the Sun and Moon or two stars, but could also conceivably represent a supernova explosion close in the sky to the Moon.

Photograph of a stone carving from Burzahom, and drawing of the same. Joglekar et al. (2007).

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