Category Archives: Astronomy

Astronomers Detect Non-Gaussian 4PCF for The First Time (Cosmology / Astronomy)

The detection of a non-Gaussian signature in the early Universe would be a smoking gun for many inflation models. Despite a number of searches, no evidence has been found for primordial non-Gaussianity in the Cosmic Microwave Background (CMB). Now, Oliver Philcox and colleagues for the first time reported the detection of the non-Gaussian 4 point-correlation function of Galaxies using the BOSS CMASS sample. Their study published in Arxiv on 3 Aug 2021.

Figure 1: PDFs of the test statistics, showing the significance of a detection of non-zero 4PCF in the BOSS CMASS dataset as a function of the number of basis vectors in the compression scheme, Neig. © Oliver Philcox et al.

What makes this detection possible, is the use of an estimator which was recently presented by Oliver Philcox et al. for computing the N-point galaxy correlation functions of Ng galaxies in O(Ng^2) time and a new modification to subtract the disconnected 4PCF contribution (arising from the product of two 2PCFs) at the estimator level.

“This is unlike previous works, and ensures that our measurement is specifically one of non-Gaussianity, rather than a recapitulation of known physics. The estimator is fast (scaling quadratically with the galaxy number density), corrected for the non-uniform survey geometry, and implemented in the public encore code. We verify its performance on a suite of lognormal simulations at high redshift, before applying it to the BOSS dataset and Patchy simulations.”

Additionally, analysis of the higher-point functions like 4PCF is hampered by their high dimension; so they have to implement a signal-to-noise-based compression scheme, which allows them to project the 4PCF into a set of ∼ 50 numbers with minimal impact on the detection significance.

“The compression has minimal impact on detection significance and facilitates traditional classical χ²-like analysis using a suite of mock catalogs”

Finally, by performing a classical χ²-like analysis in the compressed subspace they detected an 8.1σ of the non-Gaussian 4PCF.

“The detectability of the 4PCF in the quasi-linear regime implies that it will become a useful tool in constraining cosmological and galaxy formation parameters from upcoming spectroscopic surveys.”

— they concluded.

Analysis code for the BOSS Even-Parity 4PCF Analysis using encore is available at: https://github.com/oliverphilcox/Parity-Even-4PCF


References: (1) Oliver H. E. Philcox, Zachary Slepian, Jiamin Hou, Craig Warner, Robert N. Cahn, Daniel J. Eisenstein, “ENCORE: Estimating Galaxy N-point Correlation Functions in O(N2g) Time”, Arxiv, pp. 1-24, 2021. https://arxiv.org/abs/2105.08722 (2) Oliver H. E. Philcox, Jiamin Hou, and Zachary Slepian, “A First Detection of the Connected 4-Point Correlation Function of Galaxies Using the BOSS CMASS Sample”, Arxiv, pp. 1-26, 2021.
arXiv:2108.01670


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My Favorite Martian Image: Helicopter Scouts Ridge Area for Perseverance (Astronomy)

A member of the Perseverance rover’s science team explains why the aerial image offers science advantages over ground-level images.

Ask any space explorer, and they’ll have a favorite photo or two from their mission. For Kevin Hand, a scientist at NASA’s Jet Propulsion Laboratory in Southern California and co-lead of the Perseverance rover’s first science campaign, his latest favorite is a 3D image of low-lying wrinkles in the surface of Jezero Crater. The science team calls this area “Raised Ridges.” NASA’s Ingenuity Mars Helicopter captured the two shots for this stereo image on July 24 during its 10th flight.

“Ingenuity is allowing the Perseverance science team to be in two places at once,” said Hand. “Right now, we are at the ‘Crater Floor Fractured Rough,’ where the rover is preparing for the mission’s first sample acquisition on Mars. Yet at the same time, Ingenuity is providing a detailed preview of a potentially intriguing geologic features hundreds of meters away from us.”

The Return to Earth camera on NASA's Ingenuity Mars Helicopter snapped this picture of geologic feature the Mars Perseverance rover team calls "Raised Ridges" during its 10th flight at Mars, on July 24, 2021.
The Return to Earth camera on NASA’s Ingenuity Mars Helicopter snapped this picture of geologic feature the Mars Perseverance rover team calls “Raised Ridges” during its 10th flight at Mars, on July 24, 2021. Credit: NASA/JPL-Caltech

The Raised Ridges intrigue Hand and his colleagues because they consist of three distinct surface fractures that converge at a central point. On Earth, similar fractures in desert environments might be a clue to past liquid water activity and thus past habitability. The Perseverance science team wants to know if what is good for the third rock from the Sun is good for Mars – and if so, whether the Raised Ridges tell them something significant about Mars’ watery past.


“If you look closely, you can see some curious lines across the surfaces of several rocks.”Perseverance science team member Kevin Hand


Ingenuity captured the images during its most complex flight yet. After taking off from its seventh airfield, it climbed to a new record altitude of 40 feet (12 meters). The helicopter then made four heading changes and took 10 images with the rotorcraft’s color camera before landing at a new airfield. The 3D image was created by combining two of those images, offering the rover team a richer perspective as they plan the next steps in their science campaign.

“In 3D it almost feels like you can reach out and touch the Raised Ridges,” said Hand. “But along with its immersive beauty, the image provides great detail. If you look closely, you can see some curious lines across the surfaces of several rocks. Are these just made by eons of wind and dust blowing over the rocks, or might those features tell the story of water? We just don’t know yet.”

Those details are important. In their search for signs of ancient life on Mars, the team is considering drilling a rock or sediment sample in the Raised Ridges, which would take several Martian days, or sols, of driving to reach. With Ingenuity’s images, the rover team now has a much better idea of what to expect if they were to go there and the science value of doing so. In the weeks to come, the science team will pour over this and other 3D images from Ingenuity and debate the merits of such a visit.

“Since landing at Jezero Crater, it’s clear to all of us that there is an abundance of geologic riches for us to explore. It’s a good problem to have,” said Ken Williford, deputy project scientist for Perseverance at JPL. “These aerial previews from Ingenuity provide the kind of actionable data that allow us to whittle down our options and get on with the business of exploring our corner of Mars.”

More About the Mission

A key objective for Perseverance’s mission on Mars is astrobiology, including the search for signs of ancient microbial life. The rover will characterize the planet’s geology and past climate, pave the way for human exploration of the Red Planet, and be the first mission to collect and cache Martian rock and regolith (broken rock and dust).

Subsequent NASA missions, in cooperation with ESA (European Space Agency), would send spacecraft to Mars to collect these sealed samples from the surface and return them to Earth for in-depth analysis.

The Mars 2020 Perseverance mission is part of NASA’s Moon to Mars exploration approach, which includes Artemis missions to the Moon that will help prepare for human exploration of the Red Planet.

JPL, which is managed for NASA by Caltech in Pasadena, California, built and manages operations of the Perseverance rover.

For more about Perseverance:

mars.nasa.gov/mars2020/

nasa.gov/perseverance

Featured image: This 3D view of geologic feature the Mars Perseverance rover team calls Raised Ridges was generated from data collected by Ingenuity during its 10th flight at Mars, on July 24, 2021. Credit: NASA/JPL-Caltech


Provided by NASA JPL

Summer Stargazing Treat As Perseid Meteor Shower Reaches its Peak (Astronomy)

The Perseid meteor shower reaches its peak on the night of 11-12 August, giving skywatchers a potentially impressive summer treat. The meteors are best viewed from the northern hemisphere, and in ideal conditions with no clouds observers could see up to 50 an hour.

Meteors are the result of small particles entering the Earth’s atmosphere at high speed, typically around 60 km per second. The pieces of debris heat up due to friction with the air, and are usually destroyed in under a second at altitudes above 80 km. The superheated air around the meteor glows briefly, and is visible from the ground as a streak of light known as a ‘shooting star’.

Throughout the year up to six random ‘sporadic’ meteors are visible each hour. During a shower, the Earth passes through a cloud of debris left behind by comets, and so many more meteors are seen entering the atmosphere. The Perseids are associated with Comet 109/P Swift-Tuttle, which last passed near the Earth in 1992. The shower meteors are named for the point in the sky where they appear to originate – the so-called ‘radiant’ – located in the constellation of Perseus.

A Perseid meteor above Pembrokeshire in 2019, by astrophotographer Allan Trow
A cropped image of a Perseid meteor above Pembrokeshire in Wales in 2019, by astrophotographer Allan Trow. The meteor is visible on the right, and the band of the Milky Way is visible in the centre. © Allan Trow / Dark Sky Wales. Licence typeAttribution (CC BY 4.0)

This year the peak should be from the evening of 11 August through to the morning of 12 August. On this night the Moon will be a thin crescent, so moonlight will not interfere, and there is a real advantage to being in a dark sky site away from the lights of towns and cities.

In the evening the radiant is lower in the sky, so fewer meteors are seen. Those that do appear are ‘Earthgrazers’, where the incoming debris particles just skim the top of the Earth’s atmosphere and can leave long bright trails. Later on in the night numbers increase as the radiant rises higher in the sky, with the best view likely to be before 03:00 BST, when the sky will start to brighten before dawn.

Unlike many astronomical events, meteor showers are easy to watch and no special equipment is needed. A meteor shower is best observed with the naked eye, and a reclining chair and a blanket make viewing much more comfortable. If clouds do make viewing impossible on the peak night itself, the shower will continue for a few more days with reduced activity.

A bolide (very bright meteor) observed during the Perseid meteor shower
An animated gif, created by astrophotographer Serjio Lobourenko, of a very bright meteor (a fireball or bolide) observed during the Perseid meteor shower. Click to see the animation run.Serjio Lobourenko / Instagram and Twitter: @coolserjio / serjio.com/Licence typeAttribution (CC BY 4.0)

Featured image: A Perseid meteor in the same frame as the galaxy M31, in an image by astrophotographer Paul Sutherland. The stars of the constellation Perseus are on the left.CreditPaul Sutherland / Skymania.com


Provided by RAS

Astronomers Developed A New Web Based Tool To Determine Interstellar Extinction In The Milky Way (Astronomy)

Eduardo Amores and colleagues presented a new web-based tool called GALExtin, which can be used to determine the interstellar extinction in the milky way. Their study recently appeared in Arxiv.

In a broad range of astronomical research, estimates of interstellar extinction are essential. Several maps and models have been published of the large scale interstellar extinction in the Galaxy. However, these maps and models have been developed in different programming languages, with different user interfaces and input/output formats, which makes using and comparing results from these maps and models difficult.

Now, Eduardo B. Amôres and colleagues addressed this issue by developing a tool called GALExtin that estimates interstellar extinction based on both 3D models/maps and 2D maps available. The user only needs to provide a list with coordinates (and distance) and to choose a model/map. GALExtin will then provide an output list with extinction estimates. It can be implemented in any other portal or model that requires interstellar extinction estimates.

How it works?

GALExtin works with two layers. The first one is a client that provides a web form to be filled out by the users, e.g. data such as coordinates and distance for the 3D extinction. Alternatively, the user can insert a list of coordinates (Galactic or Equatorial) with distances. It is also necessary to select the coordinate system and the desired model/map.

In the HTML code, the embedded PHP program accesses an SQL table to attribute a number to the process, unique identification for each run of GALExtin, which is also used to assign and manipulate input and output files names.

Once PHP receives a process number and the information passed through HTML, it calls an IDL program that manages the extinction computation. It verifies the number of input lines. Its primary task consists of calling the routines that compute the interstellar extinction for each chosen model/map.

In the final step, the routine returns the extinction estimates to the main program. The output is displayed in the web form if a single direction is given, or written to a file if a file with coordinates was given. For either Galactic or Equatorial coordinates, the values must be given in decimal degrees.

Validation

They also validated their tool by comparing the results of GALExtin with the ones obtained with the original software of the models, dustmaps, as well as with the values obtained using the Vizier−CDS in the case of some maps. You can refer their paper to explore these details. They are also planning to include several other excellent extinction maps and models in GALExtin.

© Educardo Amores et al.

Reference: Eduardo B. Amores, Ricardo M. Jesus, Andre Moitinho, Vladan Arsenijevic, Ronaldo S. Levenhagen, Douglas J. Marshall, Leandro O. Kerber, Roseli Kunzel, Rodrigo A. Moura, “GALExtin: An alternative online tool to determine the interstellar extinction in the Milky Way”, Arxiv, pp. 1-12, 2021. https://arxiv.org/abs/2108.00561


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First Additively-manufacture Thermal Protection Shield is Going To Space (Astronomy)

A research team at Oak Ridge National Laboratory have 3D printed a thermal protection shield, or TPS, for a capsule that will launch with the Cygnus cargo spacecraft as part of the supply mission to the International Space Station. The launch will mark the first time an additively manufactured TPS has been sent to space.

Scientists worked with NASA to develop materials designed to withstand extreme temperatures encountered when objects reenter the atmosphere. The TPS protects a basketball-sized capsule that was developed by the University of Kentucky as a testbed for entry system technologies.

“This is an opportunity to gain flight experience on new materials,” ORNL’s Greg Larsen said. “Additive manufacturing enables automated, rapid production and opens up new design opportunities for using lightweight materials in spacecraft.”

Equipped with sensors that record and transmit data to monitor performance, the capsule is anticipated to return to earth before the end of 2021.

Featured image: A 3D printed thermal protection shield, produced by ORNL researchers for NASA, is part of a cargo spacecraft bound for the International Space Station. The shield was printed at the Department of Energy’s Manufacturing Demonstration Facility at ORNL. Credit: ORNL, U.S. Dept. of Energy


This science news has been confirmed by us from ORNL


Provided by ORNL

An (Almost) Alien Message For the INAF Antennas (Astronomy)

Last spring the Sardinia Radio Telescope inaugurated the observations dedicated to the Seti project. Today, July 30, 2021, some small antennas installed next to the large dish have picked up, together with an INAF antenna in Bologna, a simulated “alien” signal, launched by a satellite of the Italian company D-Orbit. The search for extraterrestrial life also passes through these experiments

We would have liked to surprise you with an Orson Welles-style message but, especially these days, we would have risked a complaint for alarm. Yet we are really working on receiving signals from alien intelligence, improving the technologies in the field from time to time.

For example, the Sardinia Radio Telescope ( Srt ) of San Basilio, one of the largest and most advanced radio telescopes in Europe, has finally entered full operation in the Seti (Search for Extra Terrestrial Intelligence) project. In fact, the first observations began last March, as scheduled, thanks to the tireless work of Andrea Melis, engineer technologist of INAF of Cagliari and member of the Seti committee within the International Academy of Astronautics (Iaa).

«In 2021», says Melis, «the Sardinia Radio Telescope became part of the telescope network of the Breakthrough Listen program . The main targets are the most promising exoplanets and the center of the Milky Way. The data analysis is already underway, about one hundred hours of dedicated observations, by colleagues from the University of Berkeley. After the Srt upgrade is completed, we will be able to expand the frequency range from the current 26 GHz to over 100 GHz, a unique feature for which Srt has been chosen to complement the Green Bank Telescope for the high frequency Seti. “.

But it is not only the Sardinia Radio Telescope that is involved in Seti observations. Alongside the 64-meter main dish, a series of small low-frequency omnidirectional antennas, called “ Vivaldi antennas ” , have been installed since 2016 , placed on the ground within a circle also 64 meters in diameter.

From left, Andrea Melis, Francesco Gaudiomonte and Adelaide Ladu, the team of INAF engineers who installed the antennas and monitored the experiment (click to enlarge). Credits: Paolo Soletta / Inaf Cagliari

This is the Saad (Sardinia Aperture Array Demonstrator) project, curated by the INAF of Cagliari in order to test the potential of the large networks of low-frequency telescopes of the future, such as the Ska project , still to be built, or the Dutch Lofar network , inaugurated in 2012.

And it is precisely some of these small antennas that recorded, on Friday 30 July 2021 at 15:55, a very particular signal launched by a satellite built and sent into orbit by the Italian aerospace company D-Orbit . This is the famous message of Arecibo , designed by astrophysicist Frank Drake and sent to deep space in 1974 by the Puerto Rican radio telescope unfortunately recently collapsed and consequently decommissioned. The intent, then, was to reach some form of intelligent life in the globular cluster of Hercules , an area rich in stars about 23,000 light years away from us.

Today, however, after almost half a century, the Arecibo message has been sent by the Italian satellite – called Ion ( In orbit now ) Scv Dauntless David – towards the Earth, and in particular towards the radio telescopes of the National Institute of Astrophysics. However, from a citizen science perspective , even amateur radio groups could be involved in this type of observations in the future.

On the left the signal received in Bologna, on the right the one received in San Basilio, Sardinia. For a few minutes, during its orbit around the Earth at about 500 km altitude, D-Orbit’s Ion Scv Dauntless David satellite launched an encrypted signal that has been successfully recorded by the INAF antennas but which must now be analyzed and decoded to understand the actual ability of our technology in the interpretation of possible alien electromagnetic signals. Credits: Inaf

The antennas of Bologna and Cagliari turned on to pick up the signal from D-Orbit which, in fact, simulated an alien source. The satellite began to be visible in radio waves at 15:55 and passed through for a few minutes until it disappeared a few seconds after 16:00.

The scenario, which in the next experiments will evolve towards increasingly complex tests, does not only contemplate the technical capacity of receiving a coded signal, but also the capacity for coordination and communication in case of reception of a real alien signal and all the implications of cultural and social character that this would entail.

Indeed, the interface between Seti, D-Orbit and Inaf was not a pool of astrophysicists or experts in satellite telecommunications, but an Italian artist who currently lives in the Netherlands: Daniela De Paulis , who has been working alongside and integrates her artistic activity with that of radio equipment and radio telescopes operator. De Paulis is also a member of the Seti committee of the Iaa, together with Andrea Melis, Stelio Montebugnoli of the INAF of Bologna and many other Italians, as can be read on the page dedicated to members from about fifteen countries. And it is precisely through Seti that the artist came into contact with the radio astronomers of INAF.

«The project», says De Paulis, «will last about two years: we will involve other scientific institutes and international radio telescopes, using messages made specifically with a group of specialists: philosophers, anthropologists, radio astronomers. The aim is to involve both the scientific community involved in SETI and the general public in receiving and interpreting a possible extraterrestrial signal, simulating in an experiential way a hypothetical scenario in which, as a human species, we are faced with the actual existence of a extraterrestrial intelligence. On an artistic level, it is a global performance, in which scientists and the public will interact via a digital platform, ideally crossing the terrestrial cultural barriers ».

The title of the project, A Sign in Space (a sign in space), is inspired, as in many of the artist’s works, by the title of the homonymous story in Italo Calvino’s Cosmicomics collection .

The reception of this signal by the two INAF radio telescopes is an important experimental verification of this project, which combines art and science in an unusual way and which does not stop there, rather it is only at the beginning.

“We have also decided to participate as a Medicine group”, adds Stelio Montebugnoli of the INAF of Bologna, “because in our country the Seti has historically started at the Medicine radio astronomy station in the early nineties – and interest is still very much alive for this very important program, for the scientific and even more philosophical aspect, for man. As Seti advisor to the scientific direction of INAF, I am very satisfied with this experiment, as it allows us to simulate the reception of a signal whose structure is not known (theoretically) – in practice, the modulation – and the real exercise will be that to extract some information from the received signal ».

Featured image: In the foreground on the right, the “Vivaldi” antenna which successfully picked up the signal sent by the Italian satellite of the D-Orbit. In the background the Sardinia Radio Telescope of San Basilio, near Cagliari. Credits: Paolo Soletta / Inaf Cagliari


Provided by INAF

Chinese Astronomers Develop Sky Model to Help Ultralong-wavelength Observations (Astronomy)

The radio sky at frequencies below ~30 MHz, particularly below ~10 MHz, is still largely unknown. Due to the absorption and distortion by the ionosphere, it is quite difficult to receive radio signal of such ultra-long wavelength by telescopes on Earth. 

Some future space projects have been proposed to map the ultra-long wavelength sky with unprecedented resolution, and help to study the astrophysics behind. 

To prepare for these upcoming projects, scientists from the National Astronomical Observatories of the Chinese Academy of Sciences (NAOC) recently developed a radio sky model that can be applied to this ultra-long wavelength band. 

The study was published in The Astrophysical Journal on June 23. 

Their sky map showed unique features at the ultralong wavelengths. They predicted the morphology of the radio sky down to ~1 MHz, which is very different from higher frequencies. For example, the high Galactic latitude regions are brighter while the Galactic plane is dark.  

Moreover, one can see clearly the shadows of Galactic spiral arms and the radio signal leaks from the gaps between arms. The model also provides interpretation for the observed global radio spectrum downturn at ~3-5 MHz. 

The model (including the data and maps) can be accessed at https://github.com/Yanping-Cong/ULSA. The model has been used for designing instruments, developing imaging algorithm and optimizing survey strategy in the DSL project.  

Featured image: The predicted sky maps, from left to right, at 10, 3 and 1 MHz. (Image by Cong et al. 2021)


Provided by Chinese Academy of Sciences

The Scientific Genius Who Eschewed Fame: Remembering Thomas Harriot, 400 Years On (Astronomy)

Four hundred years ago, on 2 July, 1621, a remarkable Englishman named Thomas Harriot died in London. He left behind some 8000 pages of scientific research, but it’s only in recent decades that scholars have uncovered their treasures.

And what they show is that Harriot independently made many significant discoveries now attributed to other, more famous scientists. Some scholars have called him “the English Galileo” and “the greatest British mathematical scientist before Newton”.

Yet Harriot died without publishing a single word of this extraordinary output. His tale reminds us that, while we may sometimes think science progresses through a series of renowned pioneers who single-handedly overturn entrenched beliefs, the story is rarely so simple.

What did Harriot discover?

For instance, we learn in school that Galileo Galilei initiated telescopic astronomy and discovered the law of falling motion. But Harriot independently did both of these things.

A pen and ink drawing of the surface of the Moon.
Thomas Harriot’s 1609 map of the Moon, drawn by observing through a telescope. Image: Wikimedia

He also deduced fledgling general laws governing the motion of everyday objects, again independently of Galileo, and before René Descartes. (Half a century later, Isaac Newton developed the definitive laws of motion.)

Harriot studied light, too, discovering the secret of colour and the nature of the rainbow before Newton, and finding the law of refraction (which we know today as Snell’s law) before the Dutch astronomer Willebrord Snell.

He also made a mathematical study of population growth before Thomas Malthus, developed a completely symbolic form of sophisticated algebra before Descartes, discovered binary arithmetic before Gottfried Leibniz, and took steps on the road to calculus with his work on infinite series.

The law of falling bodies

It wasn’t until 2008 that Harriot’s work on gravity was fully reconstructed, by the German scholar Matthias Schemmel.

As Schemmel pointed out, Harriot and his contemporary Galileo were heirs to essentially the same body of knowledge. It’s perhaps not so surprising, then, that they made some of the same breakthroughs. There are plenty of examples of independent co-discoveries in history, most famously that of calculus by Newton and Leibniz.

The law of falling motion says that without air resistance, all objects, no matter their size or mass, fall from the same height at the same rate.

Legend has it Galileo dropped balls from the Leaning Tower of Pisa to study how they fell. Nobody knows if this is true, but Harriot had the same idea – he recorded the time, in pulse beats, that it took for different objects falling from as high as 55½ feet (about 17 metres) to reach the ground.

Both Harriot and Galileo devised more accurate experiments, however, from which they derived a mathematical understanding of how things fall.

This combination of experiment and mathematics is now the accepted way to derive a law of nature. Quantifying observations means others can test the results, and use them to make useful predictions.

Harriot and Galileo weren’t the first to understand the role of observation and mathematics in this context, of course. But they were among the most successful of the pre-Newtonian pioneers.

Galileo didn’t publish his work on gravity until after Harriot had died, and there’s no evidence that the two men ever met or corresponded.

The law of refraction and the shape of the rainbow

The German astronomer Johannes Kepler, however, did correspond briefly with Harriot. Kepler had been working on the nature of light and vision when word reached him that Harriot had unravelled two mysteries – the law of refraction, and why the rainbow has its magical colours and unique shape.

The law of refraction describes how light bends when it passes from one medium into another, which explains how an image can be focused by a glass lens, or why your leg looks wobbly when you dip it in a swimming pool.

A diagram from Ibn Sahl’s 10th-century treatise on optics showing the path of light refracted by a lens. Image: Wikimedia

Harriot derived this law 20 years before Snell, but there’s a popular belief that the 10th-century Baghdad-based scholar Abū Saʿd al-ʿAlāʾ ibn Sahl beat even Harriot. This is not quite right – Ibn Sahl is a notable pioneer whose geometrical diagram of light focused by a lens gives, in hindsight, the correct refractive path. But there’s no evidence he deduced his result from experiment, or that he understood the general properties of refraction.

Judging from his surviving papers, even Snell failed to generalise his result, which he, like Ibn Sahl, never wrote as the neat trigonometric equation we use today. Harriot, by contrast, did. His derivation of the general law of refraction is another example of his rigorous blend of experiment and mathematics.

Harriot’s other adventures

If only Harriot had published! In the early stage of his career, though, he was bound by commercial secrecy, for his first patron was controversial statesman and entrepreneur Sir Walter Raleigh. Harriot was also busy dodging heretic hunters, and sailing the high seas as Raleigh’s navigational advisor.

A heavily decorated title page reading 'A briefe and true report of the new found land of Virginia'.
Thomas Harriot published only one work in his lifetime – a report on his stay in North America in the 1580s. Image: Wikimedia

Raleigh had delusions of empire and glory, and wanted to establish a trading colony in today’s US before the Spanish beat him to it. The one work Harriot did publish in his lifetime was “a brief and true report” on the economic potential of Raleigh’s chosen American site.

Harriot’s contribution to colonialism has justly attracted its share of criticism. Nonetheless, his report is still widely praised for its sympathetic depiction of the way of life of the North Carolina Algonquian people, as it was when Europeans first set foot on their land. Harriot learned the local language, and enjoyed much about the year he spent living with the Algonquians.

What he loved doing most, though, was mathematics and physics. He was neither flamboyant nor ambitious, and when he was wrongfully imprisoned through an unlucky connection with the Gunpowder Plot (a failed attempt to assassinate King James I), he told his jailers he just wanted …

“… to live a private life for the love of learning that I might study freely”.

Conclusion

In the late 1590s, Harriot had found a second patron, Henry Percy, the ninth earl of Northumberland. It was then that he was able to study the mysteries of nature and the marvels of mathematics for their own sakes, rather than the “applied” work he had done for Raleigh.

Having two generous patrons meant Harriot didn’t need to publicise his discoveries to attract funding, the way Galileo did. Nor did he care about fame, despite being urged by friends to claim his priority. His manuscripts do contain several almost-finished treatises, but it seems he was so busy doing science that he never managed to put his results together for the printer.

After his death, well-meaning scholars carved up his manuscripts in an attempt to study and publish them. In the process, however, all the papers disappeared, seemingly lost forever. Then, 150 years later, the Hungarian astronomer Franz Xaver Zach discovered them, locked safely away in Northumberland’s castle.

Most of the papers were then given to the British Museum. They’re now in the British Library, where I had the privilege of studying them. (They’re also available online.)

As for Harriot, no one knows much about him as a person – not even his birthday. Nevertheless, he’s fascinated scholars for the past half-century (as I discovered some years ago when I set out to bring his story to a wider, non-specialist readership).

That’s because despite the lack of biographical data, those precious manuscripts show that what mattered most to Harriot himself was mathematics and science. Four hundred years on, his mix of genius and dedication is something to honour.

Featured image: Rita Greer/FAL


Provided by Monash University

Astronomers Find One Group of Appearing and Disappearing Stars (Astronomy)

An international collaboration of astronomers has identified a curious occurrence of nine stars like objects that appeared and vanished in a small region within half an hour in an old photographic plate.

Astronomers collaborating across counties track vanishing and appearing celestial objects by comparing old images of the night sky with new modern one, register unnatural phenomena, and probe deep into such phenomena to record changes in the Universe.

Scientists from Sweden, Spain, USA, Ukraine, and India, including Dr. Alok C. Gupta, Scientist from ARIES, investigated early form of photography that used glass plates to capture images of the night sky from the 12th of April 1950, exposed at Palomar Observatory in California, USA and detected these transient stars which were not to be found in photographs half an hour later and not traced since then. Such a group of objects appearing and disappearing at the same time have been detected for the first time in the history of astronomy.

The astronomers have not found any explanation in well-established astrophysical phenomena like gravitational lensing, fast radio bursts, or any variable star that could be responsible for this cluster of fast changes in the sky.

Dr. Alok C. Gupta, Scientist from Aryabhatta Research Institute of Observational Sciences (ARIES), Nainital, an autonomous institution of the Department of Science and Technology (DST), Government of India, participated in this study which was recently published in Nature’s “Scientific Reports”. The study led by Dr. Beatriz Villarroel of Nordic Institute of Theoretical Physics, Stockholm, Sweden, and Spain’s Instituto de Astrofísica de Canarias, used the 10.4 m Gran Telescopio Canarias (the largest optical telescope around the world) at Canary Islands, Spain, to do deep second epoch observations. The team hoped to find a counterpart at the position of every object that had appeared and vanished on the plate. The counterparts found are not necessarily physically connected to the weird objects.

The scientists are still exploring the reasons behind the observation of these strange transient stars and are still not sure about what triggered their appearance and disappearance. “The only thing we can say with certainty is that these images contain star-like objects that should not be there. We do not know why they are there,” says Dr. Alok C. Gupta.

The astronomers are examining the possibility that the photographic plates were contaminated with radioactive particles causing false stars on the plates. But if the observation is proven to be real, another option is solar reflections from reflective, unnatural objects in orbit around Earth several years before the first human satellite was launched.

The astronomers who belong to the collaboration Vanishing & Appearing Sources during a Century of Observations (VASCO) have still not sorted out the root cause of the “nine simultaneous transients”. They are now eager to look for more signatures of solar reflections in these digitized data from the 1950s in a hope to find aliens.

Featured image: The same 10 x 10 arcmin field shown in POSS-1 and POSS-2 red bands. In the POSS-1 image, we see a number of objects that cannot be subsequently found, marked with green circles. Purple circles are artifacts during the scanning process. 9 objects are present in the POSS-I E image (left) from the 12th of April, but not in the POSS-2 image (right) from 1996. One slightly larger circle hosts two transients. The 9 transients are not caused by a difference in depth or spectral sensitivity. The images are based on the DSS digitizations of the Palomar plates. © Alok Chandra Gupta et al.


Publication link: Villarroel, B., Marcy, G.W., Geier, S. et al. Exploring nine simultaneously occurring transients on April 12th 1950. Sci Rep 11, 12794 (2021). https://doi.org/10.1038/s41598-021-92162-7 https://www.nature.com/articles/s41598-021-92162-7


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