Discussion in 'Science, Tech, & Space Exploration' started by nivek, Oct 26, 2017.
Which one is ‘Oumuamua’s home star? | EarthSky.org
Oumuamua’s Silence Actually Says a Lot
Another group of astronomers issued a new report saying they’ve been listening to it ever since and haven’t heard a thing.
“We were looking for a signal that would prove that this object incorporates some technology – that it was of artificial origin.”
Dr. Gerald Harp from the SETI Institute is the lead author of a paper – “Radio SETI observations of the interstellar object ′OUMUAMUA” published in the February edition of Acta Astronautica – which details work done by scientists using the Allen Telescope Array (ATA) in California to listen to ‘Oumuamua as it swung by at a distance of 170 million miles away or less than the diameter of Earth’s orbit.
“Observations were made at radio frequencies between 1 and 10 GHz using the Array’s correlator receiver with a channel bandwidth of 100 kHz. In frequency regions not corrupted by man-made interference, we find no signal flux with frequency-dependent lower limits of 0.01 Jy at 1 GHz and 0.1 Jy at 7 GHz. For a putative isotropic transmitter on the object, these limits correspond to transmitter powers of 30 mW and 300 mW, respectively.”
In astronomical terms, that’s like putting a glass up to the wall of your hotel room and listening to the guests next door. And?
“We didn’t find any such emissions, despite a quite sensitive search. While our observations don’t conclusively rule out a non-natural origin for ‘Oumuamua, they constitute important data in accessing its likely makeup.”
Despite high hopes that it might be an alien spacecraft or probe (like the Harvard scientists who still believe it was), Harp says all they heard was space crickets. Nothing. Not even the whoosh of slight acceleration that a light sail (the Harvard idea) might make as it sped up from being pushed by solar rays.
Does this mean they should pack up the Allen Telescope Array and go home?
“While no signals were found coming from ‘Oumuamua, the types of observations reported by SETI Institute scientists may have utility in constraining the nature of any interstellar objects detected in the future, or even the small, well-known objects in our own solar system.”
Of course not, say the scientists making sure they don’t jeopardize their future funding. This exercise will allow them to refine their listening when the next interstellar object flies by. In fact, those Harvard guys have identified some candidates already in the solar system.
Harvard prof doesn't back down from claims that alien spacecraft may be zipping past Jupiter orbit
The trouble with the idea of Ouamuamua being an alien spacecraft is that it is not moving very fast. Surely a race capable of launching an interstellar spacecraft would be able to make it go faster, around or one-tenth one-twentieth of the speed of light at least.
A contrary voice on Oumuamua.
This interstellar visitor was not an alien spacecraft, researchers say - CNN
But a new analysis of all the existing data about 'Oumuamua was published Monday in the journal Nature Astronomy. The research suggests that the interstellar object is natural in origin and not an alien spacecraft. CNN has reached out to Loeb and Bialy for comment.
"We have never seen anything like 'Oumuamua in our solar system. It's really a mystery still," said Matthew Knight, associate research scientist at the University of Maryland's Department of Astronomy. "But our preference is to stick with analogs we know, unless or until we find something unique. The alien spacecraft hypothesis is a fun idea, but our analysis suggests there is a whole host of natural phenomena that could explain it."
The technical article.
Still like this "artist rendering" of Oumuamua.
Mission to Catch ‘Oumuamua is Possible With Existing Technology
If you’re one of those who still believes or hopes that the strange cigar-shaped interstellar comet/asteroid/hybrid ‘Oumuamua is actually a spaceship … or if you wish we could have gotten a closer look at a visitor from another star while it was near Earth – you may be in luck. A scientific group that formed just two weeks after ‘Oumuamua was discovered in 2017 says it’s not too late. Project Lyra has issued a detailed paper describing how ‘Oumuamua can be caught and analyzed with existing technology and when the best time for a launch will be. Can it be done? Will the robotic crew on ‘Oumuamua see it fast approaching and hit the gas – or whatever might be powering it?
“We now know such a mission, at least in principle, is achievable. The possible scientific return would be tremendous and might fundamentally alter our understanding of our place in the universe.”
Software developer Adam Hibberd, a volunteer with the Initiative for Interstellar Studies who designed the software to determine the optimal dates and trajectory for the mission and is the lead author on the paper to be published in Acta Astronautica, described in Wired how this will be a “this changes everything” project. ‘Oumuamua is currently moving away from Earth at a speed of 26.33±0.01 km/s (16.36 miles/sec) or 500 million miles per year, which will have it crossing the boundary into interstellar space in the late 2030s.
A SpaceX Falcon Heavy rocket.
The Project Lyra model determined that a launched by the most powerful rocket — either SpaceX’s Falcon Heavy or NASA’s soon-to-be-available Space Launch System – would start the process. The spacecraft would have to be equipped with a booster rocket that would be fired as it makes its turn around the Sun – giving an extra boost to the Sun’s gravitational assist. It would then swing around Jupiter, getting another gravitational boost. That would give it enough speed to catch up to ‘Oumuamua. Since Falcon Heavy is ready, what are we waiting for?
“Unfortunately we can’t just launch any year we like. To make missions feasible using current technology, we are reliant on Jupiter taking up a certain point in its 12-year orbit around the sun, and so the opportunities follow approximately a 12-year cycle.”
Ah, yes. The limits of current technology – the bane of those raised on Star Trek. Because a conventional spacecraft needs a gravitational acceleration boost, the optimal launch date for the Project Lyra craft would be in 2033, putting its catch-‘Oumuamua date sometime in 2048. The good news is, that gives the Project Lyra team some time to find ‘Oumuamua in interstellar space – not a trivial task either.
If existing technology can catch ‘Oumuamua, why not use it to catch the next interstellar object that comes past Earth instead? Again, that requires finding them early enough – a task space scientists have not yet mastered with existing telescopes. This highlights the importance of space research and development that’s not tied to government budgets or private space company profit margins. If we’re serious about space exploration, learning more about the universe, searching for other life forms, chasing interstellar objects and the like, we need to see them and their costs as an investment in the future of humanity.
Sorry, E.T. seekers, Oumuamua doesn't appear to be artificial.
New 'Oumuamua Origin Theory Offered - Coast to Coast AM
Alas, a fresh look at 'Oumuamua would seem to squelch that alien speculation as researchers reportedly determined that the object is probably an active asteroid that was once a part of a planet or comet, but got flung out into space due to interaction between its proverbial homeworld and the star it orbited. This hypothesis, dubbed 'tidal fragmentation,' was derived by way of computer models which, when applied, showed that such a scenario could account for object's unique attributes, such as its shape, color, and the way in which it traveled through space.
Interstellar visitor ‘Oumuamua could still be alien technology
Did alien tech visit our solar system?
‘Oumuamua’ is a mysterious, interstellar object that crashed through our solar system two years ago. And a new study argues that it might in fact be alien technology, because an alternative, non-alien explanation might be fatally flawed.
But most scientists think the idea that we spotted alien technology in our solar system is a long shot.
In 2018, our solar system ran into an object lost in interstellar space. The cigar-shaped object was dubbed ‘Oumuamua.’ Then, close observations showed it was accelerating, as if something were pushing on it. Scientists still aren’t sure why.
One explanation: Alien propulsion
The object was propelled by an alien machine, such as a lightsail — a wide, millimeter-thin machine that accelerates as it’s pushed by solar radiation. The main proponent of this argument was Avi Loeb, a Harvard University astrophysicist.
Most scientists, however, think ‘Oumuamua’s wonky acceleration was likely due to a natural phenomenon. In June, a research team proposed that solid hydrogen was blasting invisibly off the interstellar object’s surface and causing it to speed up.
Now, in a new paper published on August 17, 2020, in The Astrophysical Journal Letters, Loeb and Thiem Hoang, an astrophysicist at the Korea Astronomy and Space Science Institute, argue that the hydrogen hypothesis couldn’t work in the real world — which would mean that there is still hope that our neck of space was once visited by advanced aliens — and that we actually spotted their presence at the time.
Here’s the problem with ‘Oumuamua’: It moved like a comet, but didn’t have the classic coma, or tail, of a comet, said astrophysicist Darryl Seligman, an author of the solid hydrogen hypothesis, who is starting a postdoctoral fellowship in astrophysics at the University of Chicago.
‘Oumuamua’ was the first object ever seen flying into our solar system and back out again. That’s opposed to most solar system objects that turn circles around the sun, never leaving the celestial neighborhood.
Its journey and the fact that it was accelerating suggested ‘Oumuamua’, which is estimated to be about 1,300 to 2,600 feet (400 to 800 meters) long, was a comet. And yet, there is no ‘coma’ or outgassing detected coming from the object as would normally be expected.
That outgassing changes how the comet moves through space, he said. It’s a bit like a very slow rocket engine: The sun strikes the comet, the warmest part of the comet bursts with gas, and that gas flowing away from the comet sends it tumbling faster and faster away from the sun.
The hydrogen body hypothesis and its problem
In a paper published June 9 in The Astrophysical Journal Letters, Seligman and Yale astrophysicist Gregory Laughlin proposed that the object was a comet made up partly or entirely of molecular hydrogen — lightweight molecules composed of two hydrogen atoms (H2).
H2 gas freezes into a puffy, low-density solid only when it’s very cold — minus 434.45 degrees Fahrenheit (minus 259.14 degrees Celsius, or just 14.01 degrees above absolute zero) in Earth’s atmosphere. Researchers had already proposed the existence of “hydrogen icebergs” out in the very cold reaches of space, Laughlin and Seligman wrote in the study. And outgassing hydrogen wouldn’t be visible from Earth — meaning it wouldn’t leave behind a visible comet tail.
The numbers worked out neatly; while a few other substances could potentially explain the coma-free acceleration, hydrogen was the best match for the data.
But in their new paper, Hoang and Loeb respond to this idea and argue that the hydrogen iceberg explanation has a basic problem: Comets form when icy grains of dust bump into each other in space and form clumps, and then those clumps attract more dust and other clumps. And comets are like snowmen: they survive only as long as they don’t melt.
The stickiness that helps form comets is similar to the stickiness of ice cubes coming straight out of a cold freezer. Leave an ice cube on the counter for a minute or two, let its surface warm up a bit, and it won’t feel sticky anymore. A thin film of liquid water on its surface makes it slippery.
Hoang and Loeb argued that even starlight in the coldest parts of space would warm up small chunks of solid hydrogen before they could clump together and form a comet of ‘Oumuamua’s large scale. And more importantly, the trek from the nearest “giant molecular cloud” — a dusty, gassy region of space where hydrogen icebergs are thought to form — is far too long. A hydrogen iceberg travelling hundreds of millions of years through interstellar space would have fallen apart, cooked by starlight.
Seligman said that Loeb’s analysis was correct that no hydrogen comet would survive such a long trip.”Hydrogen icebergs don’t live that long in the galaxy,” he said. “And you definitely don’t have time to get all the way from [the nearest] giant molecular cloud.“
The theory only works if ‘Oumuamua is just 40 million years old, he said. Over that time frame, outgassing could have molded the comet’s oblong shape without destroying it entirely.
‘Oumuamua origin unknown
He pointed to a paper published in April in The Astronomical Journal, which proposed a number of nearby origin points for ‘Oumuamua.
The paper’s authors didn’t nail down the comet’s home entirely, which would be impossible, they said. ‘Oumuamua was hardly moving when it arrived in our sun’s gravity well, which makes tracking the comet through space tricky. But the researchers looked at what else passed through the Milky Way neighborhood that our sun is now passing through in recent cosmic history. They landed on two groups of young stars, the Carina and Columba moving groups, said Tim Hallatt, a graduate student and astrophysicist at McGill University in Montreal, and lead author of the paper published in April.
They all formed around 30 million to 45 million years ago in a cloud of gas that then dispersed. That small, dissipated cloud of molecular gas, with just a few young stars, is one where hydrogen icebergs might form, Hallatt said
“There are many processes that can eject ‘Oumuamua-type objects from young stars in moving groups — like gravitational nudges between stars in the group, planet formation, or as Seligman and Laughlin 2020 argue, the molecular clouds that create the stars in the first place,” Hallatt told Live Science.Advertisement
All three papers fit neatly together if you assume ‘Oumuamua was a hydrogen iceberg that originated in Carina or Columba, Hallatt added.
“Seligman & Laughlin’s idea could work here because H2 objects should have a short lifetime in the galaxy (as Loeb correctly concludes), and an origin in Carina or Columba would make it young enough to survive its journey,” he said.
So what is ‘Oumuamua?
“Shortening the distance that H2 iceberg needs to travel does not solve the problems we outline in our paper, because the H2 iceberg would have formed when its parent planetary system formed, billions of years ago,” and in those eons, the iceberg would have evaporated, he told Live Science in an email.
Loeb also said that hydrogen icebergs are expected to come from giant molecular clouds, not parts of space like Carina or Columba. And he reiterated that no hydrogen iceberg could survive the trek from the nearest giant molecular cloud.
Asked if there is a clear leading candidate explanation for ‘Oumuamua’s acceleration, Loeb referred Live Science to a not-yet-released book he authored called “Extraterrestrial: The First Sign of Intelligent Life Beyond Earth,” due for publication in January.
‘Oumuamua is Not a Nitrogen Iceberg – So What is it?
The mysterious cigar-shaped interstellar object named ‘Oumuamua has baffled experts since it was first seen speeding through our Solar System back in October of 2017. There are numerous theories as to what it is, such as a comet, asteroid, dust bunny, alien technology, a hydrogen iceberg, and part of a Pluto-like planet.
In regards to the Pluto-like planet theory, researchers claimed that the mysterious object may have contained solid nitrogen because its body was shiny and reflective. Since Pluto and Saturn’s moon Titan both have some nitrogen ice, the experts theorized that ‘Oumuamua may have been a broken piece of a Pluto-like planet from a different solar system. But a new study by two astrophysicists seems to debunk that hypothesis.
According to Harvard astrophysicists Amir Siraj and Avi Loeb, based on the size of ‘Oumuamua, it couldn’t be a nitrogen iceberg as there isn’t enough nitrogen to make an object that large – it has an estimated length of between 1,300 and 2,600 feet (400 to 800 meters), and between 115 and 548 feet in width (35 to 167 meters).
In fact, they claim that there isn’t enough nitrogen ice in the entire universe to create an object the size of ‘Oumuamua. The astrophysicists even went a step further and calculated how much mass Pluto-like exoplanets would need to have in order to make a nitrogen iceberg the same size as ‘Oumuamua and they found that the planets would need to have a mass greater than their stars and over twice the mass that would be required to create all of the planets in our own Solar System. “But that’s crazy,” Siraj noted, adding, “It’s preposterous.”
Siraj and Loeb’s study was published in the journal New Astronomy where it can be read in full.
But Steven Desch and Alan Jackson, who are the two astrophysicists from Arizona State University’s School of Earth and Space Exploration who conducted the original study about the ‘Oumuamua coming from a piece of a Pluto-like planet, are not convinced that Siraj and Loeb debunked their theory.
‘Oumuamua (the dot in the middle) photographed on 28 October 2017 by the 4.2 meter William Herschel Telescope in the Canary Islands. (Via Wikipedia)
In an email to Live Science, Desch stated, “Siraj and Loeb did not find that we made a mistake, and so they should have accepted the numbers we got.” “Instead, they attempted their own back-of-the-envelope calculation and made a great number of approximations and estimates, and came up with different numbers that they say aren’t favorable.” “They are attempting to manufacture controversy when none exists.”
So, what exactly is ‘Oumuamua? The mystery regarding the unexplained interstellar object continues…