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#200 Spodcast 200



This week we say goodbye to Jamie as regular cohost for a while, while he concentrates on his solo album "Iron fluff". The Spodcats join Matt in seeing Jamie off in our 200th Episode. 'Oumuamua flys through the fluff and a surprise victory all served with Asparagus and Mustard oh yeah baby Space.


Keep your ’lectric eye on me babe Put your ray gun to my head Press your space face close to mine, love Freak out in a moonage daydream, oh yeah

Bowie



28th August 1993 – The Galileo spacecraft discovers the moon Dactyl, around 243 Ida, the first known asteroid moon. Discovery made by mission member Ann Harch

Named after the Dactyls, creatures which inhabited Mount Ida in Greek mythology.


Dactyl is only 1.4 kilometres diameter, about 1/20 the size of Ida which is about 59.8 × 25.4 × 18.6 km. Unlike the much much bigger Ceres it is not rounded, not even as rounded as the much bigger Vesta, Ida was the second \steroid to be visited by a spacecraft after 2 years earlier 951 Gaspra on 29 October 1991




‘Oumuamua might be Alien after all. ( it isn’t though)


Remember the cigar-shaped object, our first interstellar visitor back in 2017!. Discovered by the Canadian Robert Weryk from his Haleakala Observatory, Hawaii, on 19 October.


We’ve discussed it quite a few times and I still think the most incredible fact is that it seems to be stationary and it’s our solar system that went whizzing past it!

Many papers have been written since the first few discussing the possible shape of ‘Oumuamua. Now we’ve all seen the beautiful pictures, but of course, they are artist impressions, mainly by artist M. Kornmesser, or derivations of their work, shortened or reddened.



From Observations, it seems that the object is much thinner than it is long, so cigar-shaped, that is is between 100 and 1000 m long, and 35 to 167m wide.

It was first looked at after it had looped in around the sun and was 33 million km away from us. It could be loose rubble or could be solid, it could be rotating or it could be tumbling. It may have come from the Oort cloud?


Is the elongation caused by ablation from interstellar dust, was it mechanical torques from the rotation, was it planetesimal collisions, tidal disruptions from a dwarf star?

Sergey Marchenko in 2019 released a paper that suggested that ‘Oumuamua was probably slab-shaped (more disc-shaped than 2001 sentinel)


Another crazy thing about ‘oumuamua is the acceleration, that is put down to outgassing despite the fact that no outgassing was seen by space telescopes, which led some to suggest it was a n alien light sail. Also wouldn’t the outgassing effect the rotation etc.


A very recent paper suggested that the visitor was made of Hydrogen Ice, forged in a giant molecular cloud, or GMC. very specifically this cloud was 5 kpc away and the journey had been 100 million years. The outgassing of the hydrogen ice would cause acceleration.

This is where this paper comes in, Thiem Hoang and of course Abraham Loeb question whether the Hydrogen Ice entity could make across the Interstellar medium (ISM) intact. The problem being space isn’t empty, it would be under attack from gas, dust, radiation, cosmic rays, starlight. The paper even questions the formation of large hydrogen Ice objects in GMC int eh first place, arguing that the objects can’t form due to the heat of collisions and so they can never actually seed.


Basically, if ‘oumuamua was to survive the 10 Myr journey it would have to start off as 5km in size. Papers as far back as 1969, argue that large Hydrogen Ice objects are highly unlikely to form in GMCs


So basically ‘oumuamua behaved like a comet in that it seems to have acceleration, but unlike a comet, there was no visible coma or tail relating to the required outgassing. Thi led Loeb to suggest it was a light sail. But another paper suggested it was, in fact, a Hydrogen Ice object and the outgassing of Hydrogen would be undetectable from our viewpoint, but Loeb has now put doubt that such an object, a giant space iceberg, could exist. Meaning that his alien light sail hypothesis isn’t quite dead.


However, the hydrogen icey object could have been forged in a nearer place, say 40million year travel away.


One thing for certain is that ‘oumuamua was a really fascinating object, but we need to see more of this type of object and closer up. The fact that we saw such an object actually does suggest that they are quite common, or the path of this one really was very peculiar or statistically very flukey!!



For the last 33,000 years, the solar system with Spaceship Earth has been moving through the cloud of a giant nuclear explosion.

PNAS - Fe60 deposit during the late Pleistocene and the Holocene echoes past supernova activity


Estimates vary of how much cosmic dust and meteorites enter Earth's atmosphere each day, but range anywhere from 5 to 300 metric tons, so roughly 40,000 metric tons of interplanetary matter strike Earth's atmosphere every year. Only a few meteorites, about five or six objects of over 1kg will hit an area the size of Texas each year.


However, earth has been filling up with this space dust and falling to the ocean bed. Sometimes in this dust is an Isotope of Iron called Iron 60, which is created inside large stars and released into the universe through supernovae. With a half-life period of 2.6 million years, it only lasts about 15 million years, so it didn’t come as part of the original Earth ingredients. It must come from space dust.


Deposits have been found from 2.6 and 6 million years ago in the ocean, but more incredible lying on the top of the antarctic snow is a freshly fallen Iron60 “dusting” probably less than 20 years old. It’s also been detected in space by … the Advanced Composition Explorer, yes you heard me correct NASA put the ACE into Space back in August 25, 1997. And it’s still in a Lissajous orbit close to the L1 Lagrangian point

Scientists have now looked at deep-sea sediment samples from the last 33.000 years and did single-atom counting of Iron 60 atoms. Mindboggling! They detected 19 atoms, which is in line with previous, older levels of Iron 60.


Earth is moving through the Local Interstellar Cloud, a hot plasma, dusty gasey cloud.



So there is a little mystery is the Local Interstellar Cloud caused by a supernova (a viable factory of Iron-60) if that was the case the Iron60 deposits would be fainter in the older samples as the Earth probably only entered the cloud in the last 33,000 years. But that is not what we see. So this finding suggests that the Local Cloud actually itself has stumbled into a larger and far more ancient Supernova cloud.


Before scientists can be sure they need to find more of the Iron60 and check to see if there is more from recent times or more back in the million-year past.





Space Fact or Fiction

Fact 1

The Super massive black Hole at the centre of the Galaxy Sgr A*.

Roughly 4 million times more massive than the sun!! And has an event horizon that would contain the solar system all the way out to Pluto

Wrong

event horizon radius of “only” 17 times that of the sun!!!

12,000,000km not even out as far as the 56,000,000 Km of Mercury



Fact 2

If the Sun was the size of a football, Earth would be little more than a coarse grain of sand and orbit about 24m away! Pluto would be in orbit just under 1km away and be smaller than a grain of flour.



Fact 3

If the space shuttle was used to get to the nearest star using its fabulous RS-25 Engine (being used on SLS because they are soooo good, with a Specific Impulse of 452 Seconds!!! In less than 80 years, a human lifetime, the fuel tank would need to be bigger than the observable universe.









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