In 1960, Freeman Dyson proposed how advanced civilizations could create megastructures that enclosed their system, allowing them to harness all of their star’s energy and multiplying the habitable space they could occupy. In 2015, the astronomical community was intrigued when the star KIC 8462852 (aka. Tabby’s Star) began to dim inexplicably. While an analysis of the star’s light curve in 2018 revealed that the dimming pattern was more characteristic of dust than a solid structure, Tabby’s Star focused attention on the concept of megastructures and their associated technosignatures.
Dyson’s ideas were proposed at a time when astronomers were unaware of the abundance of exoplanets in our galaxy. The first confirmed exoplanet was not discovered until 1992, and that number has now reached 5,514! With this in mind, a team of researchers from Bangalore, India, recently released a paper that presents an alternative to the whole megastructure concept. For advanced civilizations looking for more room to expand, taking planets within their system – or capturing free-floating planets (FFP) beyond – and transferring them into the star’s circumsolar habitable zone (HZ) is a much simpler and less destructive solution.
The research was led by Raghav Narasimha, a physics graduate student at Christ University in Bangalore, India. He was joined by Margarita Safonova and Chandra Sivaram, a Department of Science and Technology (DST) Woman Scientist and a professor of astrophysics (respectively) at the Indian Institute of Astrophysics (IIAP) in Bangalore, India. The preprint of their paper, “Making Habitable Worlds: Planets Versus Megastructures,” recently appeared online and is being reviewed for publication in Astrophysics and Space Science.
The Problem with Megastructures
The possibility of advanced civilizations building giant structures to harness the energy of their stars is time-honored, with examples going back to the early 20th century. The earliest examples include John Desmond Bernal’s “Bernal Sphere,” which he detailed in his 1929 work “The World, the Flesh & the Devil.” According to Bernal, the source of the material for building such structures “would only be in small part drawn from the Earth; for the great bulk of the structure would be made out of the substance of one or more smaller asteroids, rings of Saturn or other planetary detritus.”
Olaf Stapledon took things a step further in his science fiction novel “Star Maker,” where he described how a future advanced human civilization was “able to construct, out in space, artificial planets for permanent habitation. These great hollow globes of artificial super-metals and artificial transparent adamant, ranged in size from the earliest and smallest structures, which were no bigger than a very small asteroid, to spheres considerably larger than the Earth.” These sources may have been the source of inspiration for Dyson’s 1960 proposal paper.
In this seminal paper, “Search for Artificial Stellar Sources of Infrared Radiation,” Dyson reasoned that a civilization’s motivations for building an “artificial biosphere” (later dubbed a “Dyson Sphere” by Nikolai Kardashev) would include harnessing energy but also multiplying the amount of space they could inhabit. Beginning with the likely possibility that civilization observed at cosmic distances would be much older and more advanced than humanity, he argued that:
“[It is] a reasonable working hypothesis that their habitat will have been expanded to the limits set by Malthusian principles. We have no direct knowledge of the material conditions which these beings would encounter in their search for lebensraum… One should expect that, within a few thousand years of its entering the stage of industrial development, any intelligent species should be found occupying an artificial biosphere which completely surrounds its parent star.”
However, at the time of writing, Dyson was working with the limits of habitable space within our Solar System, which was confined to Earth. Nevertheless, the various bodies of the Solar System (particularly Jupiter and the gas giants) have a tremendous amount of material that could (in theory) be repurposed to create an artificial biosphere. Using Jupiter as an example, Dyson argued that the planet’s mass was sufficient to create a spherical shell around the Sun about 2 to 3 meters (6.5 to 10 ft) in thickness with a density of “200 grams per square centimeter.”
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Starship | Second Flight Test
On November 18, 2023, Starship successfully lifted off at 7:02 a.m. CT from Starbase on its second integrated flight test.
While it didn’t happen in a lab or on a test stand, it was absolutely a test. What we did with this second flight will provide invaluable data to continue rapidly developing Starship.
The test achieved a number of major milestones, helping us improve Starship’s reliability as SpaceX seeks to make life multiplanetary. The team at Starbase is already working final preparations on the vehicles slated for use in Starship’s third flight test.
Congratulations to the entire SpaceX team on an exciting second flight test of Starship!
Follow us on X.com/SpaceX for continued updates on Starship’s progress
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For its Final Trick, Chandrayaan-3 Brings its Propulsion Module to Earth Orbit
On August 23, ISRO’s Vikram lander detached from its propulsion module and made a soft landing near the Moon’s south pole region. The lander then deployed its Pragyan rover, and for two weeks the endearing little solar-powered rover performed marvelously, detecting water ice and characterizing the makeup of the lunar regolith before succumbing to the darkness and cold of the lunar night.
But since the rover mission ended, the propulsion module that brought it to the Moon has made a detour, performing a series of complex maneuvers that took it from a tight lunar orbit back to Earth orbit. This was possible because the module still had more than 100 kg of fuel, allowing scientists to conduct additional maneuvers and experiments.
Right now, the propulsion module (PM) is orbiting Earth at an altitude of 115,000 km (71,500 miles), well above geostationary orbit. ISRO said the mission team decided to use the available fuel in the propulsion module to derive additional information for future lunar missions. More specifically, this demonstration gave them the chance to test mission operation strategies for a future sample return mission.
A graphic of the Chandrayaan-3 lander separating from the propulsion module. Credit: ISRO.
The PM has had a busy and productive mission. While in lunar orbit for about a month, it wasn’t just taking it easy. After the separation of the lander, the PM operated an on-board experiment, the Spectro-polarimetry of HAbitable Planet Earth (SHAPE) payload, designed to observe the Earth. Specifically, this instrument also provided scientists and engineers experience for future missions and research as its purpose was to study habitable planet-like features of Earth. These observations will be used by ISRO for future studies of exoplanets. Additionally, there was a special operation of the SHAPE payload on October 28, 2023 during the solar eclipse.
But because the spacecraft had such a precise orbit injection and optimal burn maneuvers, the amount of leftover fuel meant the engineers could do even more with the PM than originally expected. The PM was commanded to execute an orbit-raising maneuver at the Moon and then perform a Trans-Earth injection burn, which placed the PM in an Earth-bound orbit.
ISRO said the first orbit raising maneuver at the Moon was performed on October 9, 2023 to raise apolune altitude to 5,112 km from 150 km. The Trans-Earth injection (TEI) maneuver was performed on October 13, 2023, and as its orbit was slowly raised, the PM made four Moon flybys before departing Moon on November 10.
Currently, propulsion module is orbiting Earth with an orbital period of nearly 13 days, at 27 degrees inclination. Because of this high orbit, ISRO said there is no threat of close approach with any operational Earth orbiting satellites.
ISRO said these extra operations allowed them to plan and execute trajectory maneuvers to return from Moon to Earth, as well as develop software to plan and validate the maneuvers. They also planned and executed a gravity assisted flyby between two celestial bodies and, most notably they avoided an uncontrolled crash into the Moon’s surface at the end of the life of PM, which met the requirements of creating no debris on the Moon.
Will its current high geostationary orbit be the Chandrayaan-3 PM’s final trick? Who knows? The resourceful engineers might figure out another way to make use of this multi-purpose spacecraft.
The post For its Final Trick, Chandrayaan-3 Brings its Propulsion Module to Earth Orbit appeared first on Universe Today.
In 1872, a Solar Storm Hit the Earth Generating Auroras from the Tropics to the Poles
Imagine a solar storm generating auroral displays across the entire sky. No, we haven’t quite seen them that strong in the current solar cycle. But, back in February 1872, people around the world reported seeing brilliant northern and southern lights. The culprit? A medium-sized sunspot group that unleased a torrent of charged particles in a coronal mass ejection directed toward Earth.
As with strong space weather storms today, the long-ago event not only sent aurorae dancing across most of Earth’s skies, but it disrupted technology. It affected telegraph communications on the submarine cable in the Indian Ocean between Bombay (Mumbai) and Aden for hours. Similar disturbances were reported on the landline between Cairo and Khartoum. That presaged the damage that such storms can do to today’s power grids and satellite communications.
Nowadays scientists know quite a bit more about the solar activity that causes these storms. Back in those days, however, solar science was still in its infancy. We didn’t have globe-girdling, interconnected communications systems. And, then as now, extremely strong solar storms were relatively rare, but they could still do damage. Today, we are well aware of the threat to modern technologies. Strong solar storms can shut down power stations, stop communications, threaten the world’s financial and trade systems, and harm life. “The longer the power supply could be cut off, the more society, especially those living in urban areas, will struggle to cope,” said Hisashi Hayakawa, the lead author of a group studying ancient solar storms. “Could we maintain our life without such infrastructure? Well, let us just say that it would be extremely challenging.”
Studying an Ancient Solar Storm
The 1872 solar event was named the Chapman-Silverman storm. Recently, an international team of 22 scientists, led by Hayakawa at Nagoya University in Japan, Edward Cliver at the US National Solar Observatory, and Frédéric Clette of the Royal Observatory of Belgium studied it in great detail. Their tools were historical records coupled with modern techniques to assess the Chapman-Silverman storm from its origins on the Sun to its impact on our planet.
Sketches by Italian astronomer Angelo Secchi (Pontifical Gregorian University). The top shows the disk of the Sun, and the lower images show the 1872 sunspot group in more detail. Courtesy Osservatorio Astronomico di Roma.
How do you go about finding records for a storm that far back? First, you look at sunspot records. People have long sketched sunspot groups and records go back quite far. The team scoured Belgian and Italian records of sunspots during the period. For terrestrial impacts, they used geomagnetic field measurements recorded in places as diverse as Bombay (Mumbai), Tiflis (Tbilisi), and Greenwich. Those gave them insight into the temporal evolution and intensity of the storm. Finally, they examined hundreds of accounts of visual aurorae caused by the storm, written in different languages.
A Japanese drawing of the aurorae triggered by the 1872 solar event. Courtesy Shounji Temple.
“Our findings confirm the Chapman-Silverman storm in February 1872 as one of the most extreme geomagnetic storms in recent history. Its size rivaled those of the Carrington storm in September 1859 and the NY Railroad storm in May 1921,” Hayakawa said. “This means that we now know that the world has seen at least three geomagnetic superstorms in the last two centuries.
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