Showing all posts tagged: astronomy
Is an alien invasion of Earth imminent asks Kurzgesagt
12 April 2023
The latest feature from Kurzgesagt, those veritable video virtuosos of educational storytelling, explores the possibility of Earth being invaded by an advanced extra-terrestrial civilisation. While Kurzgesagt stresses much of what they present here is speculative, some of the points they raise are nonetheless fascinating.
While this video is based on scientific papers, we are presenting interesting ideas based on little data and lots of extrapolation, so take them with a grain of salt.
Kurzgesagt make the seemingly incredible suggestion that our galaxy, the Milky Way, may one day not be big enough to accommodate all the space faring civilisations that could potentially arise. The notion seems astonishing given the amount of space we’re talking about.
It would take one hundred thousand years to travel from end of the galaxy to the other, assuming we could do so at the speed of light — or who knows, less — if we could travel faster than the speed of light. Still, we’re talking about great volumes of space.
It is also possible humanity is the first technological civilisation to emerge in the Milky Way. This call is made on the basis that there is next to no evidence of the existence of other intelligent lifeforms in the galaxy. This thought is backed up by the Fermi paradox, which asks, if the galaxy is teeming with habitable planets, were are all the extra-terrestrials?
Sufficiently advanced extra-terrestrials would be relatively easy to detect, with the technologies we possess. Their Dyson swarms, their presence in numerous neighbouring star systems, would create blips on the radar, so to speak. That’s not to say there are no other technological civilisations in the galaxy, but if there were, they’re possibly at a similar level of development to ours at the moment.
But intelligent civilisations need significant amounts of time to evolve. The process has taken billions of years on Earth. So while the galaxy seems devoid of space faring civilisations at present, that may change in the next billion or so years, as currently in utero lifeforms grow. Intelligent civilisations also need a stable environment in which to germinate, which Earth, and the Sun, has given us, but some good fortune has been involved in our case.
Kurzgesagt suggests suitably located planets orbiting red dwarf, or M-type stars, which are abundant, provide an ideal environment for intelligent life to develop.
Most stars are red dwarfs that can sustain habitable planets for tens of trillions of years! Life on these planets has an incredibly long time window to appear and pass the hard steps.
Red dwarf stars live for trillions of years, as opposed to billions, for G-type stars such as the Sun. Intelligent life would therefore have more chance of taking hold, as it has plenty of time to do so. On Earth, intelligent life took five billion years to emerge, being half way through the Sun’s approximately ten-billion year lifespan.
But if the process had started any later, it may well have been too late. As the Sun ages, it is becoming warmer, and eventually Earth will be too hot to support life. Humanity, it seems, came along at the right moment. Seen in that context, planets hosted by red dwarfs appear to be the perfect incubator for intelligent life. But things are not that simple: red dwarfs pose their own problems for the emergence of life.
For one, any planets in a red dwarf’s habitable zone, a place where the environment is neither too hot nor too cold, would be tidally locked. This means one side of a planet would permanently face the star, and be exceedingly warm as a result. The other side, meanwhile, would always be shrouded in darkness, and likely too cold for life to thrive.
It has been suggested life could flourish on the day-night terminators of such planets, but this would make for an all too narrow habitable corridor. In addition, red dwarfs also emit radiation flares, which can have the effect of “sterilising” planets in their vicinity, rendering them uninhabitable. That’s not too good. Nor is it conducive for the prevalence of intelligent life.
Given life only spawns in what seems like an extremely slender set of circumstances, an extra-terrestrial invasion may be the one thing we don’t have to worry about. There’s simply no one else out there. Given humanity appears to ascendant then, we have the opportunity, as Kurzgesagt suggests, to carve out our own niche in the galaxy.
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Astronomy, Sky Country by Karlie Alinta Noon, Krystal De Napoli
14 February 2023
Image courtesy of Evgeni Tcherkasski.
“Aboriginal and Torres Strait Islander people are the oldest scientists in human history.”
Learning this may come as a surprise to readers of Astronomy, Sky Country, written by Karlie Alinta Noon and Krystal De Napoli, and published by Thames & Hudson, winner of the People’s Choice Award in the 2023 Victorian Premier’s Literary Awards.
Because, for instance, were not the Assyro-Babylonians, in Mesopotamia, in south west Asia, documenting their scientific and astronomical research, over three thousand years ago? They were, but Indigenous peoples living in Australia had been making, and recording, astronomical observations tens of thousands of year earlier.
Unlike the Assyro-Babylonians though, who inscribed their knowledge onto tablets and the walls of temples, First Nations Australians recorded information, including astronomical knowledge, differently. Knowledge and stories was passed from generation to generation through word of mouth, cultural rituals, and Songlines.
Songlines were memorised descriptions of pathways or tracks used by Indigenous Australians to guide them from one place to another across country, and included instructions on how to travel, and landmarks to guide their journey. Songlines also contained protocols to observe when crossing other Indigenous peoples’ lands, or country.
But far longer journeys, to destinations a great distance from country, and, on occasions, beyond the Australian continent, required different means of navigation. This is where Indigenous Australians looked to the sky and the stars. This meant travelling overnight when the stars were visible, and when it was also a little more comfortable than trekking through the heat of day.
Torres Strait Islanders, for instance, navigated by a large constellation named Tagai, one of the creator beings. The Tagai group of stars embodies the constellations of Scorpius, the Southern Cross, and Corvus. These three star groups can be seen in the lower left hand quadrant of this constellation map at Nature Noon.
But Tagai was not solely a navigation guide, the constellation also played a role as a timekeeper. Tagai’s movement across the sky as the year progressed, marked the passing of seasons, and acted as a calendar of sorts, indicating times to hunt for food, or harvest crops.
Planets also assisted some Indigenous Australians with navigation, including Venus. Venus was also a part of some Songlines containing cultural lessons and protocols.
Through Astronomy, Sky Country, Karlie Noon, a Gamilaraay astronomer and science communicator, and Krystal De Napoli, a Kamilaroi astrophysicist and educator, bring, through the lens of the cultures of Indigenous Australians, a new understanding to the science of astronomy.
Contemporary astronomical knowledge, for its importance, value, and indeed fascination, is analytical and systematic. Scientists and astronomers of recent centuries have been more concerned with comprehending, and classifying stars as mere stellar objects. Red giant star or red dwarf? What distance are they from Earth, and each other?
But stars are not mere points of light in the night sky. They are also entities that guide, teach, and tell stories. While Indigenous Australians are not the only early cultures to embed legends, stories, and knowledge, in the planets, stars, and constellations, they are among the first.
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astronomy, Australian literature, books, Indigenous literature, Karlie Noon, Krystal De Napoli
Poetry by American poet laureate Ada Limon headed for Jupiter
3 February 2023
Now if Australia had a poet laureate, which it will by 2025, perhaps their work would be winging its way through interplanetary space towards Jupiter. Instead, verse composed by American poet laureate Ada Limón, will be engraved on Europa Clipper, a NASA space probe scheduled for launch in October 2024, to study Europa, one of the giant planet’s largest moons.
The spacecraft is set to launch from NASA’s Kennedy Space Center in October 2024 and by 2030, it will be in orbit around the gas giant. It will conduct multiple flybys of Jupiter’s icy moon Europa, to gather detailed measurements and determine if the moon has conditions suitable for life. Europa is thought to contain a massive internal ocean and is considered one of the most promising habitable environments in our solar system, beyond Earth.
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Black hole stars, a weird cosmic entity and Soundgarden song
18 December 2022
Black hole stars, sometimes called quasi-stars, were a hypothetical star that may have existed in the earliest days of the universe, up to about half a billion years after the Big Bang.
They were larger — far larger — than any star known to be present in the universe today, and were capable of outshining entire galaxies. And, as the name suggests, they were part black hole. We know some stars become black holes at the end of their lives, but for the two to somehow co-exist, star and black hole, without one destroying the other? How can such a thing even happen?
In 1927, British-Indian scientist J. B. S. Haldane, in an essay titled Possible Worlds wrote the oft quoted sentence: “now, my own suspicion is that the universe is not only queerer than we suppose, but queerer than we can suppose.” It was Haldane’s way of saying we’re unlikely to ever make sense of the universe, no matter how much we learn about it. Black hole stars, in their bizarre weirdness, only add to the wonder.
And, as a bonus, American rock/grunge act Soundgarden’s 1994 track, Black Hole Sun, written by the late Chris Cornell, takes on a whole (er, no pun intended) new meaning in this context.
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astronomy, music, science, video
Could flight of the bird propulsion power deep space travel
11 December 2022
It may be possible to construct deep space vessels capable of (eventually) reaching speeds equal to two percent of the speed of light:
Scientists have proposed a dazzling new mission to travel to the stars that is inspired by the elegant flights of seabirds, such as albatrosses, reports a new study. The interstellar concept mission would harness shifting winds generated by the Sun in order to accelerate a spacecraft to as much as 2 percent the speed of light within two years, allowing it to soar into the vast expanse beyond our solar system.
But two percent the speed of light, a velocity that would take some time to attain anyway, isn’t all that speedy considering the vast distances between celestial objects, such as the Sun, and the nearest star to us, Proxima Centauri.
If we round off the speed of light at 300,000 kilometres (km) per second, two percent of that is six thousand km per second. That’s 360,000 km per minute, and 21,600,000 km per hour. 518,400,000 km per day. If my maths is on spec — not always guaranteed — the journey to Proxima Centauri, some 40,208,000,000,000 km distant, would take 77,561 days, or about 213 years.
On the other hand, if Pluto is an average of 5,300,000,000 km from Earth — sometimes it is closer, sometimes more distant — it would take about ten days to travel there. Assuming such speeds could be attained at relatively close proximity to the Sun, that is. This method of deep space travel seems reasonable for reaching points in and near the solar system, but might be out of the question for interstellar voyages carrying people.
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Alcyoneus a sixteen million light year long radio galaxy
4 December 2022
Image courtesy of A Owen.
Alcyoneus, a galaxy located some three and a half billion light years from Earth, at over sixteen million light years in length, is — without putting too finer a point on it — staggeringly huge. Our home galaxy, the Milky Way, at a mere one hundred thousand light years long, is positively minuscule in comparison.
But Alcyoneus isn’t a sixteen million light year long container of stars and whatever else fills a galaxy. Alcyoneus is what’s known as a radio galaxy, and the bulk of its length comes from radio lobes, which are a little like jets of radio energy, that fire out from opposite sides, into the surrounding space.
At its starry core Alcyoneus, which is likely an elliptical galaxy (unlike the image of the spiral type galaxy I’ve featured above), may not be all that much larger than the Milky Way. And that’s probably a relief for members of Alcyoneus’ galactic council, who only have to travel several hundred thousand light years to visit their constituents, rather than multiple millions.
If radio galaxies intrigue you though, Universe Guide has put together this explainer.
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The Sun will not go supernova but it may still drive us away
25 November 2022
In five billion years, hopefully long after a, hopefully, still extant humanity have departed the solar system for a new home somewhere among the stars, the Sun will become a red giant star. In this late phase of its life, the Sun will expand in size to engulf all the solar system’s inner planets.
While this part of the Sun’s lifecycle will be relatively short-lived — some estimates suggest a mere one billion years — our home planet will have well and truly been obliterated, by the time the Sun shrinks in size again. Unless of course any of our descendants, who stayed home, succeeded in moving Earth further out into the solar system.
The idea has been mooted previously. Even before the Sun becomes a red giant, its gradually increasing heat output, or luminosity, will, in time, make living on Earth ever more uncomfortable.
Such as undertaking will be quite the feat of astronomical engineering. Being able to move the planet will be an achievement in itself, to say nothing of navigating to a suitable spot elsewhere, clear of the larger outer planets. But what happens when the Sun shrinks and cools off again? Do we try and send Earth sunwards again? Perhaps our efforts would be better served finding a Earth-twin planet to live on, orbiting a younger star. And, while we’re at it, figuring out a way of reaching said location in a reasonable timeframe.
At least it’s not something we need concern ourselves with right this minute though. Likewise, the prospect of the Sun exploding as a supernova. It’s something that cannot happen. But what about another star — one in the approximate proximity of the solar system — going supernova? That could be a whole another story.
That’s the question the people at Kurzgesagt explore this month, in their latest video presentation. Again the prospect of a relatively nearby star exploding is not something that will occur any time soon. At present, IK Pegasi, a binary star some one hundred and fifty four light years away, is the nearest possibility, though by the time it is projected to explode, it will be more like five hundred light years distant.
Still as Kurzgesagt explains, risks remain, and even supernovas occurring at some distance could have an impact, no matter how minor, on Earth.
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Tune into the aftermath of the Big Bang on television
21 November 2022
If you’re still using an aerial (is that still a thing?) instead of cable (is that still a thing?) or internet, to watch TV, and — presumably — still possess an old school (think rabbit ears) TV, you may be able to pickup remnants of the Big Bang, the force of cosmic nature, that brought the universe into being.
Like COBE, WMAP scans the sky over and over again, soaking up the ancient light from the Big Bang known as the cosmic microwave background. Microwaves are a low-energy form of radiation but higher in energy than radio waves. The cosmic microwave background blankets the universe and is responsible for a sizeable amount of static on your television set–well, before the days of cable. Turn your television to an “in between” channel, and part of the static you’ll see is the afterglow of the big bang.
All you’d see is static, some of which may be post Big Bang microwaves bouncing around the cosmos, but it might be more interesting than some of what is broadcast on the terrestrial channels.
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astronomy, history, science, technology
If the International Space Station orbited at 3000 metres
9 November 2022
What if the International Space Station orbited at a height of just three thousand metres? Benjamin Granville decided to find out. The answer to many “what-if” questions are often perfectly implausible, but some sure are worth asking. The scenario makes for quite the ride for those aboard the station…
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DART helping to protect Earth from off planet threats
29 September 2022
It could be argued we’re not doing as much as we could to avert potential catastrophes on the planet. Climate change and global conflict would be two examples. When it comes countering possible threats from outside though, some progress is being made.
The test of an asteroid defence system, whereby a NASA probe was sent to collide with Dimorphos, a celestial object, to effect a change, albeit minor, in its trajectory, is one instance.
NASA did not send this probe to observe this asteroid or even scoop some samples from its surface to bring back to Earth, as other missions have done. The agency dispatched the spacecraft with the explicit hope of crashing it and changing the asteroid’s trajectory. This is a test run, but a future version of this mission could save Earth from a catastrophic impact by deflecting an asteroid on a collision course. A little bit of practice never hurts.
While Dimorphos does not pose a threat to Earth — at least not at the moment — another asteroid such as the one that brought about the demise of the dinosaurs, might in the future.
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