Astronomy & Space Exploration

Dumbstar said:
I just watched all of it. It was actually very enjoyable. However how much is science and how much is Isaac Asimov? Was this the atheist equivalent of reading/watching the Bible?
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It's definitely speculative, and partly based on this 1999 book:

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http://www.astronomy.ohio-state.edu/~gaudi/AST141/Unit5/lecture2.html

But still grounded in actual physics — at least as far as our rudimentary understanding of the theory of this universe goes, and the stuff we continue to learn at the Large Hadron Collider — which is presumably used to feed far future particular simulations. e.g. the time needed for an isolated supermassive black hole with a mass of 10^17 g to dissipate via Hawking Radiation: https://journals.aps.org/prd/abstract/10.1103/PhysRevD.13.198

Nothing we'll have to worry about anyhow...it will take like ~10000000000000000000000000000000000000000000000000000000000 x the time from the singularity of Big Bang to Current Universe for that that happen — everything is meaningless on that unnervingly vast scale, though still imagine how distant and desolate things will be as the universe continues to expand at an accelerated rate...

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https://www.forbes.com/sites/starts...n-how-big-will-the-universe-get/#3de48e5d1f52
 
Huge explosion on Jupiter that an amateur captured.



Considering how big Jupes is, it is really really huge

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Usually quite skeptical of these Jovian impact gifs because many aren't resolved properly, which makes it harder to ascertain the real-time size, but that does look pretty big — most likely an extinction level event on Earth. Probably a comet that collided head on, or perhaps one that was was captured and slowly dragged inwards — reminiscent of Shoemaker–Levy 9 (though that broke up within the Roche Limit and the subsequent series of impacts weren't as significant).

 
Ian Reus said:
Isn't Jupiter the solar system hoover as it sweeps up any loose debris floating close?
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Yes and no, we can't say for sure if it's a net positive in the grand scheme of things wrt. hoovering up stuff that could endanger Earth. Jupiter does alter the trajectories of meteors and comets that could be headed for Earth with its immense gravitational field, so it is in some ways a great vacuum cleaner. But it also destabilizes the trajectories of meteors and comets that are primarily orbiting the sun — flinging them towards the inner Solar System. Not to mention, it can also eject planetesimals from the asteroid belt — again, sending them on a collision course with Earth (it's suggested Chelyabinsk meteor that fragmented and created the Chelyabinsk meteorite was ejected out of the Flora family because of Jupiter).

 
Invictus said:
Yes and no, we can't say for sure if it's a net positive in the grand scheme of things wrt. hoovering up stuff that could endanger Earth. Jupiter does alter the trajectories of meteors and comets that could be headed for Earth with its immense gravitational field, so it is in some ways a great vacuum cleaner. But it also destabilizes the trajectories of meteors and comets that are primarily orbiting the sun — flinging them towards the inner Solar System. Not to mention, it can also eject planetesimals from the asteroid belt — again, sending them on a collision course with Earth (it's suggested Chelyabinsk meteor that fragmented and created the Chelyabinsk meteorite was ejected out of the Flora family because of Jupiter).

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Cheers for that.
 
Invictus said:
Usually quite skeptical of these Jovian impact gifs because many aren't resolved properly, which makes it harder to ascertain the real-time size, but that does look pretty big — most likely an extinction level event on Earth. Probably a comet that collided head on, or perhaps one that was was captured and slowly dragged inwards — reminiscent of Shoemaker–Levy 9 (though that broke up within the Roche Limit and the subsequent series of impacts weren't as significant).

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Surely we have professional astronomers watching Jupiter, who would see anything the size of Shoemaker-Levy impact? Or don't we?
 
Apparently big news coming from ALMA Observatory in Chile.

It seems the "EVENT HORIZON TELESCOPE" might have gotten the first images of the massive black hole at the centre of our galaxy. (or something like that)

The press conference will be on Wednesday.
 
niMic said:
Surely we have professional astronomers watching Jupiter, who would see anything the size of Shoemaker-Levy impact? Or don't we?
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As far as I know, we aren't watching any of the planets round-the-clock and a lot of the collisions or impact flashes are observed serendipitously. Constant monitoring would be too resource intensive because the process hasn't been automated yet, and Jupiter isn't remarkable enough for professional astronomers to dedicate valuable time to it — instead, you have a lot of volunteer/amateur astrophotographers who track/film it every so often in a coordinated way (with the help of softwares like DeTeCt or JID) and relay important events to the appropriate agencies (the gif posted by @VeevaVee was probably one such important event that an associated astrophotographer happenstanced upon).

Also, a lot of the official observations clubs are notoriously cliquish, and don't allow outsiders that haven't been approved — so their room for growth in terms of volunteer membership is very limited. e.g. restricted Yahoo group for DeTeCt:
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http://pvol2.ehu.eus/psws/jovian_impacts/

Elitist twits!
 
I see that the first pics of the black hole at the centre of our galaxy will be published on April 10th.

Years of processing petabytes of data around the world apparently.

I’m preparing to be utterly underwhelmed by it but I also can’t hide my excitement.
 
Camy89 said:
I see that the first pics of the black hole at the centre of our galaxy will be published on April 10th.

Years of processing petabytes of data around the world apparently.

I’m preparing to be utterly underwhelmed by it but I also can’t hide my excitement.
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Agreed. It may well be underwhelming because of the nature of a black hole; light cannot escape at the point of the event horizon.
And yet exciting as well because of the effects of a black hole.

They could be nothing more than cosmic vacuum cleaners or they could be a route to other Universes.
 
Camy89 said:
I see that the first pics of the black hole at the centre of our galaxy will be published on April 10th.

Years of processing petabytes of data around the world apparently.

I’m preparing to be utterly underwhelmed by it but I also can’t hide my excitement.
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Same. As @Buster15 points out, it may well be anticlimatic - but it's an achievement in itself.
 
Ian Reus said:
How can they take pictures of a black hole if it absorbs all light?
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They aren't directly photographing the actual singularity, that is physically impossible because it is an infinitesimally small sinkhole and propagates no data of its own. They are only tracing the filtered infrared/microwave emissions (which is less attenuated) from the supercharged and ultra-hot event horizon of Sgr A* (which is several million miles in diameter and has a glowing property as photons and plasma and gas swirl around emitting enormous amounts of X-ray flares and radio noise) — and then reconstructing the void at the center of it all (which stands out because there's a haunting absence of light or radio waves) to give you a vague idea of where the black hole's shadow is supposed to be. Basically like a negative-image.
 
Invictus said:
They aren't directly photographing the actual singularity, that is physically impossible because it is an infinitesimally small sinkhole and propagates no data of its own. They are only tracing the filtered infrared/microwave emissions (which is less attenuated) from the supercharged and ultra-hot event horizon of Sgr A* (which is several million miles in diameter and has a glowing property as photons and plasma and gas swirl around emitting enormous amounts of X-ray flares and radio noise) — and then reconstructing the void at the center of it all (which stands out because there's a haunting absence of light or radio waves) to give you a vague idea of where the black hole's shadow is supposed to be. Basically like a negative-image.
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Cheers.
I've seen the effects a black hole has on stars around it so thought that was already covered.
Will hopefully be interesting anyway.
We need something from up there for a bit of inspiration.
 


Livestream:

 
Camy89 said:
Why are they doing that?
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Discrete soil sampling, they want to collect a variety of sub-surface specimens by scooping up the loose debris from the resultant crater and sending them back to Earth (ETA December 2020). A mining apparatus would have been impractical and much more expensive in terms of initial payload.

On a side note, Israel could become the 4th country to soft-land on Moon next week...


Orbited the moon:
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Soft-landing on the moon:
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Soft-landing missions in progress:
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(launch 22 Feb 2019)
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(launch May 2019)
 
:lol:

Though on a sombre note, the “civilian space budget” for most countries is pretty limited so there's not a ton of money left for cosmetic extravagance and everything is pretty stripped-down. Israel's typical annual spending (excluding satellites and other significant expenses) is ~$100 million...compared with ~$21 billion for NASA, ~US$7 billion for ESA, etc. so compromises have to be made in non-essential departments. Malaysia is another country that tends to punch above its weight with a budget of just ~$10 million (like indigenous development of the NEO RazakSat for a total mission outlay of $50 million).

* This particular landing of Beresheet is privately funded by SpaceIL and powered by non-native SpaceX Falcon 9 rockets, so the spiel above is beside the point.
** If only we were a peaceful species and stupid military budgets were directed towards space exploration and related technological innovation... (ㄒoㄒ)
 
Don't Kill Bill said:
https://www.bbc.co.uk/news/science-environment-47832920


Now tested up to the same temperature range generated by the SR71 Blackbird Mach 3.3 and the pre cooler works, the testing moves on to hypersonic speeds Mach 5 next.
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The pre cooler is an astounding piece of engineering. My main concern is how it will cope with atmospheric pollution affecting airflow.
However, this engine is for high speed travel isn't it and not for space travel.
 
Buster15 said:
The pre cooler is an astounding piece of engineering. My main concern is how it will cope with atmospheric pollution affecting airflow.
However, this engine is for high speed travel isn't it and not for space travel.
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It's part of the Skylon space plane concept.

The idea is to create an engine to take a plane all the way into space by creating a hybrid jet/rocket engine. To do that you have to increase the speed attainable by the jet engine part in order to make the rocket efficient enough to prevent the need to use multiple stages.

Between Mach 3 and Mach 6 the jet engine becomes a ram jet burning the oxygen in air rather than having to carry oxidizer for the fuel.

Most of the weight of a rocket is fuel. If you save enough fuel during that part of the acceleration to negate the weight of the aircraft and engines then in theory you are more efficient than using just rockets to get into space.

The spin off benefit is the pre cooler used to get the jet engine past 3.3 is a game changing device for faster jet/missile engines with or without the space plane.

Again, I don't want to jinx the thing but it could be one of those moments when a vital tech advance brings many stalled ideas into feasibility.
 
Don't Kill Bill said:
It's part of the Skylon space plane concept.

The idea is to create an engine to take a plane all the way into space by creating a hybrid jet/rocket engine. To do that you have to increase the speed attainable by the jet engine part in order to make the rocket efficient enough to prevent the need to use multiple stages.

Between Mach 3 and Mach 6 the jet engine becomes a ram jet burning the oxygen in air rather than having to carry oxidizer for the fuel.

Most of the weight of a rocket is fuel. If you save enough fuel during that part of the acceleration to negate the weight of the aircraft and engines then in theory you are more efficient than using just rockets to get into space.

The spin off benefit is the pre cooler used to get the jet engine past 3.3 is a game changing device for faster jet/missile engines with or without the space plane.

Again, I don't want to jinx the thing but it could be one of those moments when a vital tech advance brings many stalled ideas into feasibility.
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Excellent. Appreciate your clarification.
 


Speaking of Interstellar, anyone else read The Science of Interstellar? It's written by Kip Throne, the astrophysicist who consulted (with high levels of involvement) on Interstellar. Very interesting, and only some of it went straight over my head.
 
niMic said:


Speaking of Interstellar, anyone else read The Science of Interstellar? It's written by Kip Throne, the astrophysicist who consulted (with high levels of involvement) on Interstellar. Very interesting, and only some of it went straight over my head.
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Yup, it's very good. Tesseracts still completely baffle me.
 
This is not specifically space exploration related, but @Invictus what's your take on this and in your opinion what's the likelihood or possibility of a natural nuclear reaction on Earth or Mars? The reactor found in Gabon in the 70s is the only known such reactor ever found on Earth it would appear. I know Brandenburg is not taken very seriously by the science community at large these days, just to put that out there.

https://www.theepochtimes.com/evide...xplosions-on-mars-says-scientist_1924819.html

Mars has a high concentration of the gas isotope Xenon 129 in its atmosphere. Xenon 129 is produced by nuclear reactions. The surface of the red planet also has an excess of uranium and thorium.

These conditions are likely the result of two large anomalous nuclear explosions on Mars in the past, argues propulsion scientist Dr. John Brandenburg in a 2014 paper, titled “Evidence of a Massive Thermonuclear Explosion on Mars in the Past.”

On Earth, in Oklo, Gabon, uranium was extracted in 1972 and found to have unusual properties. Natural uranium deposits all contain about 0.7 percent U235. The isotope U235 in the Oklo mine, however, showed at levels around 0.6 percent, suggesting the U235 had already been “burned.”

Dr. Francis Perrin, former chairman of the French High Commission for Atomic Energy, told the French Academy of Sciences on Sept. 25, 1972, that a nuclear reaction had taken place approximately 1.7 billion years ago.

While many scientists say the nuclear reactions on Earth and Mars could have occurred naturally, some scientists disagree. If the reactions weren’t natural, the implication is that intelligent beings—whether human or alien—artificially caused them.

A few other interesting links on the subject for those who care to see more

http://spsr.utsi.edu/articles/EvidenceforaLargeAnomalousNuclearExplosionsinMarsPast.pdf

https://www.foxnews.com/science/was-there-a-natural-nuclear-blast-on-mars
 
Natural thermonuclear explosion? That's just what they want you to believe, it's a relic of a nuclear war that took place there millenia ago between long extinct species.

Not a bad idea for fiction that.

...but seriously, I've always found the natural nuclear event theory fascinating.

Actually, I was joking but according to Reddit, Brandenburg did suggest it was an alien nuclear bomb. :wenger: I'm not entirely sure that's what he was getting at.
 
Loublaze said:
This is not specifically space exploration related, but @Invictus what's your take on this and in your opinion what's the likelihood or possibility of a natural nuclear reaction on Earth or Mars?
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You mean right now? Zero percent chance. There are a few important things to consider for “natural occurring nuclear reactors”...
  • It is only possible with fissile isotopes: Protactinium-230, Uranium-233, Neptunium-235, Uranium-235, Plutonium-239, Plutonium-241, Americium-243, or other intermediates.
  • All of them have decayed completely because they have short half lives (e.g. Plutonium-239 has a half life of ~20,000 years) or don't exist naturally altogether, apart from Uranium-235. The rest are all bred or artificially produced these days.
  • The ratio of Uranium-235 (fissile and with a half life of ~700 million years to the final Plumbum-204) to Uranium-238 (non-fissile with a half life of ~4.5 billion years) is 0.007 right now, so it is exceedingly rare (for reference, nuclear reactors typically operate in the .03 to .05 range), so the probability of it existing in sufficiently enriched forms in clustered shells that can sustain a reaction with even strong moderators (to sufficiently slow down the neutrons) is highly unlikely.
In the past? Maybe...
  • The Uranium-235 on Earth wasn't actually made on Earth, but naturally synthesized in a supernova (or perhaps a merger of neutron stars) in the distant past...and has always existed through the Earth's ~4.5 billion year span according to cosmochronological estimates (which were actually used to date the Earth).
  • Stands to reason that the concentrations would have been much higher in the past because a lot of the fissile substance wouldn't have decayed yet.
  • At some point you could have had concentrations that could sustain a reaction in the presence of moderators, yes. For reference, the ratio of Uranium-235 to Uranium-238 at the time of the supernova/merger that produced them is theorized to be ~1.5 — at some point, you could have had concentrations that could sustain a natural reactor in the presence of a suitable moderator because of the comparative abundance of fissile Uranium-235 vis-à-vis the current Cenozoic Era.
P.S. I'm not a nuclear physicist or geochemist, and this is only an educated guess on the basis of what I know (and could definitely be off the mark). For example, the event that created the Uranium-235 might not have been single stage (and it is entirely possible that it was deposited in shells over a vast period of time via several supernovae/mergers)! :lol:
 
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