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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Felis chaus: Observations of the Jungle Cat in by the lower reaches of the Jordan River, Jordan.

The Jungle Cat, Felis chaus, is a medium-sized Felid found in wetlands across the Middle East, Caucasus region, South and Southeast Asia, and southern China. It is not currently considered globally threatened, but is known to be in decline across its range due to the ongoing loss of wetland habitats. In Jordan the species is currently considered to be Critically Endangered, with the last known record of the species being two dead specimens found in February 1998, on Al–Baqurah Island in the Yarmouk River Valley. However, much of the key environment for the species is found along the Jordan Valley, much of which has been designated a military zone with very limited access.

In a paper published in the Journal of Threatened Taxa on 26 July 2024, freelance conservationists Ehab Eid and Mohammed Farid Alayyan of Amman in Jordan present new evidence for the presence of the Jungle Cat in the Jordan Valley of Jordan, based upon camara trap evidence gathered during a survey targeting the Golden Jackal, Canis aureus.

The camera traps were placed on a private farm growing Citrus fruit at Sheikh Hussein, in the north of the Ghor region, between the Sea of Galilee and the Dead Sea. The boundaries of the farm extend to the Jordan River, where there is an area of wetlands dominated by Common Reeds Phragmites communis, Cattails, Typha domingensis, and Athel Trees, Tamarix aphylla. The area is also home to other wetland Plants, including Sieber’s Wormwood, Artemisia sieberi, Christ’s Thorn Jujube, Ziziphus spina-christi,  Arabian  Fagonia, Fagonia  arabica,  and  Common  Mallow, Malva sylvestris. The area is an important refuge for migratory Birds such as Ducks, Herons, Egrets, and Storks, but is not subject to any form of protection, with the water being affected by herbicide and fertilizer run-off from local farms, and Reed-beds subjected to frequent clearing by farmers who perceive them as a fire-hazard.

Eid and Alayyan placed four camera traps in the Reed beds between June 2020 and 28 February 2022. There were mounted between 40 and 50 cm above the ground, and faced both north and south, to avoid false records during  sunrise  and  sunset. No bait was placed, and the cameras were checked monthly.

During this period, five observations of Jungle Cats were made, with all four cameras making observations. The first observation was made on 12 January 2021 at 12.58 in the afternoon, the second on 17 January 2021 at 9.33 in the evening, the third on 11 April 2021 at 21.35 in the evening, the forth on 3 September 2021 at 10.41 in the evening, and the final observation on 30 January 2022 at 2.12 in the morning.

Jungle Cats photographed in the study area between 12 January 2021 and 30 January 2022. Ehab Eid in Eid & Alayyan (2024).

The camera traps also imaged several other species, including Golden Jackal, Canis aureus, Egyptian Mongoose, Herpestes ichneumon, Wild Boar, Sus scrofa, Red Fox, Vulpes vulpes, and numerous Rodents and Birds, as well as four feral Dogs living on the farm.

To the best of Eid and Alayyan's knowledge, this is the first camera trap survey carried out in the Jordan Valley, and has established the presence of the Jungle Cat in Jordan 22 years after the previous  record, of dead Animals, although the data gathered was not sufficient to determine the number of Cats in the area.

Despite the heavy agricultural activity in the area, it appears to remain a suitable environment for Jungle Cats, with dense vegetation along riverbeds and an abundant supply of Rodents, the favoured prey of Cats.

Jungle Cats were only observed a very limited time, despite the long duration of the study, although this is at least in part due to the dense vegetation in the study area, which proved a general hindrance to observations, interfering with observations of Animals and producing numerous observations of swaying Plants. However, Eid and Alayyan suggest that it is this dense vegetation which makes the environment suitable for Jungle Cats, which are known to be averse to encounters with Humans. 

While Jungle Cats are still persisting in the Jordan Valley, their habitat is threatened by Human activities, with agricultural expansion altering the environment, causing the Reed-beds to fragment and degrade. 

During the time when the study was being carried out, a Jungle Cat was also recorded at Al-Mashare’e, about 6 km to the south of the study area, where it became entangled in a Chicken-protection net, being videoed before escaping. Based upon this, Eid and Alayyan propose that a citizen-science approach, in which residents of the Jordan Valley are encouraged to report sightings of Jungle Cats, may reveal more about the presence of, and threats faced by, the species in the region.

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Fireball over northern Portugal.

Witnesses across Portugal, Spain, and France have reported observing a bright fireball meteor slightly before 11.50 pm local time Saturday 18 May 2024 (slightly before 10.50 pm on Saturday 4 May, GMT). The fireball is described as having moved from southeast to northwest, appearing to the northwest of Columbus and disappearing to the east of Fort Wayne. A fireball is defined as a meteor (shooting star) brighter than the planet Venus. These are typically caused by pieces of rock burning up in the atmosphere, but can be the result of man-made space-junk burning up on re-entry.

The 18 May 2024 fireball seen from Cáceres in Spain by a camera operated by the European Space Agency's Planetary Defence Office, which forms part of the AllSky7 Fireball Network. European Space Agency.

On this occasion the fireball was also observed from space, by a Meteosat Third Generation weather satellite in a geostationary orbit 35 000 km above the Earth. The satellite imaged the meteorite with its Lightening Imager, which is usually used (as its name suggests) to detect lightning, but which was able to track the meteor as a series of bright flashes, as the surface of the body ablated away, due to the high speed (about 160 000 km per hour) at which it was passing through the atmosphere.

The 18 May 2024 fireball meteor as seen by a Meteosat Third Generation weather satellite. European Space Agency.

Objects of this size probably enter the Earth's atmosphere several times a year, though unless they do so over populated areas they are unlikely to be noticed. They are officially described as fireballs if they produce a light brighter than the planet Venus. The brightness of a meteor is caused by friction with the Earth's atmosphere, which is typically far greater than that caused by simple falling, due to the initial trajectory of the object. Such objects typically eventually explode in an airburst called by the friction, causing them to vanish as a luminous object. However, this is not the end of the story as such explosions result in the production of a number of smaller objects, which fall to the ground under the influence of gravity (which does not cause the luminescence associated with friction-induced heating).

Heat map showing areas where sightings of the meteor were reported (warmer colours indicate more sightings), and the apparent path of the object (blue arrow). American Meteor Society.

These 'dark objects' do not continue along the path of the original bolide, but neither do they fall directly to the ground, but rather follow a course determined by the atmospheric currents (winds) through which the objects pass. Scientists are able to calculate potential trajectories for hypothetical dark objects derived from meteors using data from weather monitoring services.

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Former eastern branch of the Nile discovered in Egypt.

From the End of the Pleistocene to about 5000 years ago, much of the Sahara is thought to have been covered by a lush green savannah, with numerous, now dry, lakes and rivers, providing a home to large Human and Animal populations. During this time the Nile was a much more substantial waterway, wider and deeper than it is today, prone to major flood events, and surrounded by extensive marshes and wetlands, making the Nile Valley a difficult environment for the hunter-gatherers of the period, and it appears to have been largely uninhabited. 

From around 5500 years ago the climate of the Sahara began to dry out, with the lush grasslands that had covered much of the area slowly disappearing, while the Nile Valley became a habitable refugia, attracting people to settle in the area, settle and begin farming. This environment enabled a great cultural flourishing, and eventually the formation of one of the word's first centralized states, the Old Kingdom of Egypt, which formed around 2686 BC. The Old Kingdom quickly established a culture of monumental agriculture, which most notably manifested as the great pyramids of the period. 

At this time the discharge of the Nile was still much higher than it is today, and multiple branches of the river are thought to have been present at any time, meandering across the floodplains of Sudan and Egypt. Since this time the Nile Valley in Egypt has undergone significant changes, due to the decline in water flow over the past four-and-a-half millennia, and the building of the Aswan High Dam in the 1960s, which made the Nile Valley in Egypt a much more controlled and predictable environment.

To the Ancient Egyptians the Nile was a vital resource, providing regular floods which kept the fields irrigated and fertile, and a ready-made transport network which enabled them to move food, manufactured goods, and building materials, to wherever they were needed. However, they had much less control of this resource than modern Egyptians, and it was prone to migrating laterally across the desert, leaving settlements and building projects cut off from water resources and easy transport. The location of many ancient sites, far from the current course of the river, provides a testament to the movement of the river, but the exact course of the river in ancient times is less clear, difficult to map due to modern farms and settlements covering the floodplain. Thus, we remain uncertain where the ancient courses of the river ran, nor if more than one branch was active at any given time. 

The pyramids and great temples of the Old Kingdom, which logically would have been constructed close to a navigable waterway, area arranged in a roughly linear pattern, running parallel to the Nile from Lisht in the south to Giza in the north.

In a paper published in the journal Communications Earth and Environment on 16 May 2024, Eman Ghoneim of the Department of Earth and Ocean Sciences at the University of North Carolina Wilmington, Timothy Ralph of the School of Natural Sciences at Macquarie University, Suzanne Onstine of the Department of History at  the University of Memphis, Raghda El-Behaedi of Near Eastern Languages and Civilizations at the University of Chicago, Gad El-Qady of the Egyptian National Research Institute of Astronomy and Geophysics, Amr Fahil of the Geology Department at Tanta University, Mahfooz Hafez, Magdy Atya, Mohamed Ebrahim, and Ashraf Khozym, also of the Egyptian National Research Institute of Astronomy and Geophysics, and Mohamed Fathy, also of the Geology Department at Tanta University, present the results of a study which used remote sensing, geomorphological, soil coring and geophysical evidence to map the Western Desert between Lisht and Giza, demonstrating the presence of a lost river branch running along this course. 

Ghoneim et al. used Synthetic Aperture Radar to create a three dimensional map of the Nile Floodplain and the surrounding desert, finding evidence of a former river channel between Lisht and Giza, which would have been navigable during the Old Kingdom, and until the Second Intermediate Period, passing by 31 pyramids from the Third to Thirteenth Dynasties. They name this the Ahramat Branch, from the Arabic 'al'ahramat' (الأهرامات), meaning 'pyramids'. This branch is largely covered by fields on the modern Nile Floodplain, making it invisible in visual satellite images, but can be traced on the ground surface by TanDEM-X satellite radar imagary and Topographic Position Index functions on Geographical Information Systems  software. This channel lies between 2.5 and 10.25 km to the west of the modern course of the Nile River. This channel appears to have been about 64 km in length, between 200 and 700 km wide, and between two and eight metres deep. The size of this waterway, combined with its course directly past the pyramids and other works of monumental architecture now marooned in the desert, implies that it was of great functional importance to the early Ancient Egyptians.

The water course of the ancient Ahramat Branch. (a) Shows the Ahramat Branch borders a large number of pyramids dating from the Old Kingdom to the 2nd Intermediate Period and spanning between Dynasties 3 and 13. (b) Shows Bahr el-Libeini Canal and remnant of abandoned channel visible in a 1911 historical map (Egyptian Survey Department scale 1:50,000). (c) Bahr el-Libeini Canal and the abandoned channel are overlain on satellite basemap. Bahr el-Libeini is possibly the last remnant of the Ahramat Branch before it migrated eastward. (d) A visible segment of the Ahramat Branch in TanDEM-X satellite radar imagary is now partially occupied by the modern Bahr el-Libeini Canal. (e)  A major segment of the Ahramat Branch, approximately 20 km long and 0.5 km wide, can be traced in the floodplain along the Western Desert Plateau south of the town of Jirza. Location of (e) is marked in white a box in (a). Ghoneim et al. (2024).

A survey carried out using Ground Penetrating Radar and Electromagnetic Tomography found a former river channel was buried beneath 1-1.5 m of modern cultivated sediment, which matched the position of the channel observed in the satellite radar imagery. The sediments within this channel are different to both the overlying silt deposits of the modern floodplain and the sandy sediments on either side of the channel. At the site where the ground survey was carried out, the riverbed sediments were approximately 400 m wide and 25 m deep (the depth of riverbed sediments implies the presence of a river for a long period of time, rather than relating to the depth of the river).

Two sediment cores were taken in this area. The first of these, Core A, was taken between the centre of the channel and the left bank, and reached a depth of 13 m. This core had an upper layer of sandy brown mud which reached down to about 2.7 m. Beneath this was a layer containing limestone and chert fragments, a reddish sandy mud layer with gravel and handmade material inclusions, then from about 3 m to about 5.8 m, another reddish sandy mud layer with gravel and Freshwater Mussel shells, followed by another layer of limestone and chert fragments, a reddish sandy mud layer with gravel and handmade material inclusions, then a black sandy mud from 6 m to 6.8 m, which graded into a well sorted medium sand; this was clean of mud by about 8 m, and persisted till about 13 m. The second core, Core B, was taken on the right bank of the branch, and reached a depth of 20 m. Here, recent brown sandy muds reached a depth of 1.5, beneath which alternating brown and gray layers of silty and sandy mud down to about 4 m. This was followed by a black sandy mud layer from 4 m to 4.9 m, then another reddish sandy mud layer with gravel and freshwater mussel shells till about 5 m. From 5 m to 20 m the profile was dominated by a clean, well sorted, medium sand. In both cores the sand layers contained groundwater, suggesting that the former Ahramat Branch of the Nile still serves as a conduit for subsurface water flow within the Nile Floodplain.

Deep sediment cores from the southern segment of the Ahramat Branch. It shows two-soil cores, core A and core B, with soil profile descriptions, graphic core logs, sediment grain size charts, and example photographs. Ghoneim et al. (2024).

The pyramids of Ancient Egypt were not isolated buildings. Each formed part of a temple complex, which also included a mortuary temple, which stood next to the pyramid, and a valley temple, beside the waterway and some distance from the pyramid and mortuary temple. All of these were connected by causeway (raised walkway), which provided a path to the pyramid complex. Many of the causeways associated with pyramids on the Ahramat Branch have causeways arranged at right angles to the course of the waterway, and end where the riverbank would have been.

The valley temples of Ancient Egyptian pyramid complexes served as disembarkation points for visitors arriving by river. Many of these valley temples have never been found, and are presumed either to have been totally plundered for their stone or to be buried beneath the desert sands or agricultural lands of the modern Nile Valley. Five valley temples are still at least partially present on the Ahramat Branch. These are associated with the Fourth Dynasty Bent Pyramid, Pyramid of Khafre, and Pyramid of Menkaure, the Fifth Dynasty Pyramid of Sahure, and the Sixth Dynasty Pyramid of Pepi II, all of which date from the Old Kingdom. All of these valley temples are adjacent to the Ahramat Branch waterway, indicating that this branch of the Nile was a navigable waterway during the Old Kingdom.

Ghoneim et al. use the positions of the pyramids arranged along the Ahramat Branch to reconstruct a history of the waterway. They conclude that the waters of were highest during the Fourth Dynasty, with pyramids from this time placed on high elevations far from the waterway. The water appears to have been much lower during the Fifth Dynasty, with pyramids consequently placed at much lower elevations, closer to the floodplain. The waters appear to have begun to rise again during the reign of Unas, the last Pharaoh of the Fifth Dynasty, and to have continued to rise during the Sixth Dynasty, with the pyramids of Pepi II and Merenre located deep into the desert.

The pyramid of the Eighth Dynasty Qakare Ibi is again located low and close to the riverbed, suggesting that waters had again fallen by this time. Qakare Ibi lived during the First Intermediate Period, after the fall of the Old Kingdom, which is known to have been associated with a significant drought, during which the annual flood on the Nile failed to appear for between 30 and 40 years. Sediment cores takin in Memphis, the capital of the Old Kingdom, have shown the city to have been covered by about 3 m of windblown sands. The Ahramat Branch seems to have shifted significantly to the east during the First Intermediate Period, then continued to drift eastwards during the Middle Kingdom, before effectively drying up during the Second Intermediate Period.

Sentinal 1 radar images show a number of apparent channels running from the Western Desert Plateau to the Ahramat Branch, suggesting tributaries to the river. All of these are now covered by sand, and therefore invisible in spectrographic images, but appear dark in the radar images, suggesting fluvial sediments beneath thr surface. Notably, the Sentinal 1 radar system, which can penetrate about 50 cm of dry sediment, is incapable of seeing the main path of the Ahramat Branch, which is largely covered by floodplain farmland. The inlets were visible in TanDEM-X satellite radar imagary, which suggested an extensive network of waterways in this area.

Using Radar and the Topographic Position Index for mapping major channels (inlets) connected to the Ahramat Branch. (a) Conceptual sketch of the dependence of surface roughness on the sensor wavelength λ. (b) Expected backscatter characteristics in sandy desert areas with buried dry riverbeds. (c) Dry channels/inlets masked by desert sand in the Dahshur area. (d) The channels’ courses were extracted using Topographic Position Index. Negative Topographic Position Index values highlight the courses of the channels while positive Topographic Position Index signify their banks. Ghoneim et al. (2024).

Several pyramids from the Fourth and Sixth dynasties appear to have causeways that connect to these inlets, rather than the main Ahramat Branch waterway.  Thes include the Bent Pyramid in the royal necropolis of Dahshur, the first of three pyramids built by Sneferu, the first Pharaoh of the Fourth Dynasty, and one of the largest and oldest pre-Giza pyramids. The location of this pyramid has long been a mystery, as it is deep within the Eastern Desert, far from the modern Nile Floodplain. The Bent Pyramid has an impressive 700 m limestone block causeway, connecting it to a valley temple, which until now has been mysteriously distant from any body of water, facing onto the dry Wadi al-Taflah. Ghoneim et al.'s reconstruction places the causeway on an inlet of the Ahramat Branch, which they name the Dahshur Inlet, and which would itself have been more than 200 m wide. Ghoneim et al. reason that this inlet would still have been flooded during the reign of Sneferu, and that it would have played a major role in the movement of the materials used to construct the temple complex. The inlet could also have been used to move materials for the construction of the Red Pyramid (Sneferu's second), which is also in the Dashur area, although no trace of a causeway or valley temple associated with this pyramid remain. Several Middle Kingdom pyramids are also found in this area, including the Black Pyramid of Amenemhat III, the White Pyramid of Amenemhat II, and the Pyramid of Senusret III, although these are all at least a kilometre to the east of the Old Kingdom pyramids, lending support to the idea that the Ahramat Branch migrated eastward over time.

The Sakkara and Dahshur inlets are connected to the Ahramat Branch. (a) The two inlets are presently covered by sand, thus invisible in optical satellite imagery. (b) Radar data, and (c) TanDEM-X topographic data reveal the riverbed of the Sakkara Inlet due to radar signals penetration capability in dry sand. (b) and (c) show the causeways of Pepi II and Merenre Pyramids, from Dynasty 6, leading to the Saqqara Inlet. The Valley Temple of Pepi II Pyramid overlooks the inlet riverbank, which indicates that the inlet, and thus Ahramat Branch, were active during Dynasty 6. (d) Radar data, and (e) TanDEM-X topographic data, reveal the riverbed of the Dahshur Inlet with the Bent Pyramid’s causeway of Dynasty 4 leading to the Inlet. The Valley Temple of the Bent Pyramid overlooks the riverbank of the Dahshur Inlet, which indicates that the inlet and the Ahramat Branch were active during Dynasty 4 of the Old Kingdom. Ghoneim et al. (2024).

The satellite radar data suggests another inlet is located about 6 km to the north of the Dashur and to the west of the ciry of Memphis, which Ghoneim et al. refer to as the Sakkara Inlet. This is interpreted as a broad river, which would have been 600 m wide where it met the Ahramat Branch. The causeways of the Sixth Dynasty pyramids of Pepi II and Merenre, both part of the Sakkara Necropolis, have causeways which lead to the Sakkara Inlet. The causeway of Pepi II's pyramid runs northeast from the pyramid, across the Sakkara Plataeu to reach a valley temple located on the south bank of the Sakkara Inlet. The causeway of the Merenre Pyramid runs 350 m southeast from the pyramid, reaching the north bank of the Sakkara Inlet. Together these pyramids indicate that the waters of the Ahramat Branch were high enough during the Sixth Dynasty to flood at least the lower parts of the western inlets, enabling their use as waterways for the shipping of building materials. However, no Fifth Dynansty pyramids are located on the inlets, suggesting that the waters were lower during this interval.

Ghoneim et al.'s data set also indicates the Fourth Dynasty pyramids of Khafre, Menkaure, and Khentkaus, located on the Giza Plateau, had causeways leading to a smaller, but clearly still significant, inlet of the Ahramat Branch, which they term the Giza Inlet. The Khufu Pyramid (the largest of the Egyptian pyramids), appears to have been connected to the main Ahramat Branch. The locations of these pyramids and their causeways offer further proof that the Ahramat Branch and its eastern inlets were active waterways during the Fourth Dynasty, and fits with previous studies which have found evidence for marshy or riverine environments on the floodplains to the east of the Giza Pyramids during the Old Kingdom.

TanDEM-X data shows, in 3D, a clear topographic expression of a segment of the former Ahramat Branch in the Nile floodplain in close proximity to the Giza Plateau. The causeways of the four Pyramids lead to an inlet, which is named the Giza Inlet, that connects from the west with the Ahramat Branch. These causeways connect the pyramids with valley temples which acted as river harbours in antiquity. These river segments are invisible in optical satellite imagery since they are masked by the cultivated lands of the Nile floodplain. The photo shows the valley temple of Khafre Pyramid. Ghoneim et al. (2024).

Ghoneim et al.'s findings suggest that water levels in the Ahramat Branch were high during the Old Kingdom of Egypt, and particularly high during the Fourth Dynasty, after which they began to decline. This correlates with previous studies which have found that the discharge from the Nile into the Mediterranean was particularly high during the Fourth Dynasty, but decreased significantly afterwards, with the lowest output of the entire Pharaonic period seen during the Fifth and Sixth dynasties. Water levels in the Ahramat Branch appear to have been much lower during the Middle Kingdom, with structures assumed to have been built close to water much further to the east than in the Old Kingdom. This is at odds with previous studies of the hydrology of the Middle Kingdom, which have suggested a predominantly wet climate, with sporadic severe droughts. Ghoneim et al. explain this discrepancy as being due to the Ahramat Branch migrating laterally to the east, rather than simply containing less water, as in the Fifth Dynasty, though with a similar result as the building of new structures migrated eastwards.

Ghoneim et al. suggest that the eastward migration and then failure of the Ahramat Branch of the Nile may have been due to tectonic activity, as the Nile Delta and floodplain slowly tilted to the northeast, causing the western part of the floodplain to become elevated. This would lead the Ahramat Branch to migrate to the east, and eventually fail as the upper portion of the Branch fused with the main Nile channel. This eastern movement would also lead to the western portion of the floodplain to become more arid, enabling the sands of the Western Desert to intrude into the area, which would in turn lead to a higher sedimentation rate within the river, and a tendency to silt up during intervals of lower flow. 

During the First Intermediate Period, which separates the Old Kingdom from the Middle Kingdom, Egypt experienced a prolonged drought, with settlements which had been prosperous during the Old Kingdom being engulfed by sands from the Western Desert. The Ahramat Branch seems to have significantly silted up during this interval, causing it to migrate further eastwards when wetter conditions returned prior to the rise of the Middle Kingdom.

During the Old Kingdom the Ahramat Branch was still connected to a number of inlets from the west, which were likely remnants of active drainage systems in the Tertiary or Pleistocene, when the Sahara was green and rainfall abundant across the region. These inlets would most probably have been fed from the Ahramat Branch rather than have carried water into it by the Old Kingdom, providing sheltered areas where the water would have been predicably calm, ideal for unloading materials for major construction materials, but would have dried up as the climate become more arid and the river shifted to the east.

Both of the sediment cores show an abrupt shift from well sorted medium sands to a more variable system with layers of gravel, fine sand, shell and other material, which Ghoneim et al. interpret as a sign of a shift from a constant, high-energy system within a deep, strongly-flowing river, to a more variable environment with a typical weaker flow, but periodic flood events. Two cores with similar profiles were previously drilled close to Giza, where they were interpreted as evidence for a Late Holocene floodplain palaeo-environment, utilised by people and prone to flood events. Further coring is likely to determine more features of the Ahramat Branch and the wider Nile floodplain.

Ghoneim et al. suggest a connection between the Ahramat Branch and the Bahr Yusef, a heavily canalized waterway connecting the Fayum Oasis to the Nile. It is likely that this waterway originally flowed northward before turning west and flowing into the Fayum Depression; the waterway currently bends very sharply westwards into the depression, possibly as a result of Human interference. The British Egyptologist John Römer has suggested that during the Middle Kingdom a dam was constructed which prevented the Bahr Yusef from flowing further to the north when its sluices were closed. Such a structure would have enabled the Egyptians of the Middle Kingdom to control the flow of the Ahramat Branch, or store water in the Fayum Depression. 

Ghoneim et al. believe their evidence demonstrates the presence of a major former channel of the Nile, which they term the Ahramat Branch, which ran past the foothills of the Western Desert Plateau, the area where the majority of the Ancient Egyptian pyramids are found. The scale of this waterway, its proximity to the pyramids, and the numerous pyramid causeways which terminate at its banks, all strongly imply the branch was active during the Old and Middle Kingdoms, and was used as a navigable waterway, used to shift materials by the people of the period. Such a waterway would have provided an important transport link to the Ancient Egyptians, connecting towns and religious centres which have hitherto appeared disconnected. The eastward migration and eventual disappearance of this waterway, was driven by a combination of tectonic movements and the incursion of wind-blown sand from the Western Desert, combined with increasing desertification within the Great Sahara region, and the Nile Valley towards the end of the Old Kingdom.

The study shows the value of combining data from satellite imagary with drilled cores, the combination of which enabled the discovery of a significant waterway, which would have played a major role in the lives of the ancient inhabitants of the region.

This discovery will enable archaeologists to gain a much better understanding of the placement of settlements and temple complexes in Ancient Egypt, potentially leading to the discovery of new sites, and providing an opportunity to protect these sites from spreading urbanization in the region. 

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Looking for the Chinguetti Meteorite.

In 1916 a young French army officer called Captain Gaston Ripert reported being taken to see a giant meteorite in the Mauritanian desert, south of Chinguetti. The story is a strange one, with Ripert claiming he was taken blindfolded, at night, on a ten hour Camel ride into the desert, where he observed a huge iron structure 100 m long and 40 m wide, recovering a smaller, 4.5 kg meteorite from its surface. Shortly after returning to Chinguetti, where he was commander of the local Camel corps, Ripert reported that his guide, a local chief, was poisoned, leaving him unable to relocate the site.

The eccentric nature of this story led many people to dismiss it out of hand. It was not unusual for western travellers of the time to make up tales of wild adventure; some even paid ghostwriters to create particularly entertaining tales. However, officers in colonial armies were supposed to refrain from such nonsense, and some aspects of Ripert's story were hard to rectify with the story being complete fiction. 

During the past century a number of expeditions have sought to locate Ripert's meteorite, with the first in 1924, although by this time Ripert was stationed in Cameroon, and could only be communicated with by letters. This meant that the early searches concentrated on the area to the southwest of Chinguetti, although Ripert later clarified that the area he was taken to was probably to the southeast. The French naturalist and explorer Théodore Monod mounted a number of expeditions to find the meteorite, starting in 1934, but was unable to locate it. In the 1950s an expedition by the French army used a declinometer  (instrument for measuring magnetic declination) in a search for the meteorite, without success, and in the 1990s a team from the British TV station Channel 4 used a magnetometer during a search for the meteorite, but took only a few measurements.

Despite all this, there are a number of elements of the story suggest that it was not complete fiction, not the least of this being Ripert's willingness to talk to experts about his journey for the rest of his life. The smaller rock which Ripert recovered did prove to be a meteorite, albeit one which, when subjected to radionuclide analysis in 2001 was shown not to have been part of a larger body (radionuclides form near the surface of asteroids due to a constant bombardment by cosmic rays, but these can only penetrate a little way, so the radionuclides they form are absent from the interior of large bodies). Finally, Ripert reported observing metallic needles protruding from the large meteorite, which he tried unsuccessfully to break off, finding that they were too ductile (able to be deformed without losing toughness) for the tools he had at hand). In 2003, the American geologist and meteorite specialist William Cassidy reported similar ductile metal needles protruding from nickel-rich zones of iron meteorites, but this was clearly unknown to science in 1916.

A fragment of the smaller meteorite brought back by Gaston Ripert in the collection of the Smithsonian National Museum of Natural History. Wikimedia Commons.

In a paper published on the arXiv database at Cornell University on 21 February 2024, Robert Warren  of Salisbury in England, Stephen Warren of the Astrophysics Group at Imperial College London, and Ekaterini Protopapa of the Department of Physics at the University of Oxford, describe the results of a more recent search for the Chinguetti Meteorite, and the prospects for either discovering its existence or proving its non-existence in the future.

Warren et al. began by collating remote-sensing data covering the region from multiple sources; they are reasonably confident that other researchers will have searched Google Earth for signs of the meteorite,  but they also accessed data from other sources, including the Shuttle Radar Topography Mission, the Advanced Land Observing Satellite (ALOS), and Landsat.

Using the reasoning that the only way a 40 m high meteorite could have disappeared in the deserts of Mauritania is for it to have been covered by a sand dune, Warren et al. began by searching for a region of high dunes which could be reached from Chinguetti by Camel in under 10 hours. There are two bands of dunes close to Chinguetti; the Les Boucles field, most of which is within 20 km of the city, and the Batraz field, which is between 40 and 60 km to the southeast. Much of the intervening area is also covered by sand dunes, but these are not large enough to describe an object as that described by Ripert.

Map showing the high sand dunes, greater than 30 m height, to the south of Chinguetti. Warren et al. (2024).

Warren et al. made two trips into the desert from Chinguetta, in the company of experienced local chameliers, one lasting eleven days and one lasting six. They found that Camels typically travel at speeds of between 2.0 and 3.6 km per hour, assuming good terrain, with the maximum speed achieved by unburdened Camels being about 5.0 km per hour. 

However, even assuming that Ripert and his guide were riding Camels unburdened by anything other than themselves, it is unlikely that this maximum speed would have been achieved for 10 hours, because the primary concern of the chameliers is for the welfare of their Camels, which are not only the most important assets they own, but also their only way of getting back to safety should a problem arise. This meant that if Warren et al.'s chameliers expected a journey to take four hours, they would travel for two hours, then give the Camels a three hour break to rest and feed, before completing the journey, something they were quite inflexible about. Neither would they travel in a straight line on anything other than the flattest terrain, but instead would zig-zag to avoid taking the Camels over steps and ledges, and would never take their Camels over the tops of dunes.

Ripert himself mentioned taking several detours during his journey, which makes a journey 50 km in a straight line from Chinguetta even less plausible. However, for the sake of convenience, Warren et al. take the area within 50 km of the city as a search area. This includes the more distant Batraz Dune Field, which Warren et al. consider unlikely, although they do concede that there is a route along a dry river bey which could bring a determined Camel rider this far in 10 hours if breaks were neglected. They also rule out the area of the Les Boucles Dune Field which lies within 10 km of the city, reasoning that Ripert, who was in charge of the local Camel Corps, would have recognised a location in this area. 

A sand dune in the Les Boucles Dune Field to the south of Chinguetta. Bruno Locatelli/Google Maps.

Having defined their search area, Warren et al. then searched their dataset for dunes large enough to have covered the meteorite described by Ripert. According to Ripert's description, the northeastern side of the meteorite was already covered by a dune at the time when he visited. The area is noted for its strong, prevailing winds, which blow northeast to southwest more-or-less constantly all year round, causing sand dunes to migrate in the same direction, and Ripert stated in 1932 that he thought it possible that the meteorite would already have been covered by the dune. Taking Ripert's estimate that the meteorite was 40 m high, it would require a dune more than 40 m high to cover it.

Sand dunes in a desert do not typically stack up against one-another; instead, they are usually discrete structures, with flat spaces between them. Warren et al. identified dunes higher than 30 m high in their remote sensing dataset, in order to give an error of margin, creating a map showing dunes which meet this criterion within the two dune fields. Since dunes are unlikely to have moved more than 100  m since 1916, the meteorite, if buried, must be within 100 m of the western edge of the dune covering it. 

Since a height of 30-40 m is reached within 300-400 m of the western flank of the dunes, it would in theory be possibly for a walk along the western flank of the dunes with a magnetometer (a passive instrument that measures changes in the Earth's magnetic field), and be confident of passing within 500 m of the meteorite, a distance at which it ought to be highly detectable.

Warren et al. also not that a magnetic survey of the area has been carried out by aircraft on behalf of the Mauritanian Ministry of Petroleum Energy and Mines by the Fugro geological surveying company, using funds provided by the World Bank, and this data has subsequently been made available to teams of scientists working on other projects. With this in mind, Warren et al. wrote to the Ministry requesting access to the data, but have yet to receive an answer.

Between 13 and 17 December 2022 Warren et al. carried out a magnetometer survey of the eastern part of the Les Boucles Dune Field on foot, covering the western edges of six large dunes, based upon which they are confident that the presence of a large iron meteorite beneath these dunes can be ruled out. Based upon the time this took, they estimate that a survey of all the potential dunes would require an expedition lasting three weeks. 

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