Astronomy and Cosmology

Image Credit: NASA, Juno, SwRI, MSSS; Processing & License: Gerald Eichstädt & Sean Doran Explanation: What's that black spot on Jupiter? No one is sure. During the latest pass of NASA's Juno around Jupiter, the robotic spacecraft imaged an usually dark cloud feature informally dubbed the Abyss. Surrounding cloud patterns show the Abyss to be at the center of a vortex. Since dark features on Jupiter's atmosphere tend to run deeper than light features, the Abyss may really be the deep hole that it appears -- but without more evidence that remains conjecture. The Abyss is surrounded by a complex of meandering clouds and other swirling storm systems, some of whic…

This is something I've thought was true for along time- that if you were travelling at 99.9% the speed of light then from your perspective it would take you about 30 years to travel across the entire universe. If this is true then does this mean that travelling at half that speed would take 60 years? Or does it only take effect at a certain speed. Because if this was true wouldn't that mean that travelling to the nearest star at just say 10% the speed of light would take about a week if you were on the ship?

If space-time is infinite ,how gravity extends to infinity? we know infinity is unreachable because it continues forever and no-one reach a finite point.How gravity extends to infinite distances while infinity is unreachable? how gravity bends and curve space-time everywhere while space time end is unreachable? for gravity to bend space-time everywhere it should reach its end , how gravity bends space-time end while this end is unreachable?

How does Venus retain its atmosphere without a magnetosphere? If it can keep its atmosphere in its current orbit does it follow that it can in Mars's orbit? Or are other factors like tidal forces involved?

This seems to be a extremely popular topic (for reasons I cannot really understand) so here is a good article about the actual physics involved in how there could be multiple universes and whether that means there is another "you" out there - or even an infinite number. https://www.forbes.com/sites/startswithabang/2019/05/23/could-parallel-universes-be-physically-real/#de8c5cc4d3f6 Spoiler alert:

https://phys.org/news/2019-05-lunar-tunnel-moon-colonies.html Lunar tunnel engineers excited by boring Moon colonies: As space agencies prepare to return humans to the Moon, top engineers are racing to design a tunnel boring machine capable of digging underground colonies for the first lunar inhabitants. "Space is becoming a passion for a lot of people again. There are discussions about going back to the moon, this time to stay," US-Iranian expert Jamal Rostami told AFP at this year's World Tunnel Congress in Naples. The administration of US President Donald Trump wants NASA to put humans back on the Moon by 2024, and the agency is also drawing up plan…

Hello dear friends! Extreme interferometers like Ligo, Virgo, Leo600, Tama300 try to detect gravitational waves http://en.wikipedia.org/wiki/Gravitational-wave_detector and ground movements are one difficulty for them. The mirrors are suspended in several stages to insulate them, sometimes actively. In addition to suspension, I suggest to measure the ground's movements by other means, and identify by how much these movements transmit into the measure at all frequencies, then subtract this contribution as estimated from the measured ground movements and the transfer function. This so-called adaptive filter is commonly used in acoustics, one method being the Kálmán filter…

At the BIS Christmas lecture in December John Zarnecki spoke about how he and his team designed and built the Huygens probe for Titan from scratch. No wonder it took so long and was so expensive. Why can't someone design a generic spaceprobe which can be used anywhere and built on a production line like Boeing airliners? Has anyone tried this? Cheerz Gian☺

We cannot see the stars in midday because atmosphere is not transparent to our vision. How then the satellites make the pictures of Earth surface which is perfectly visible regardless the atmosphere?

In reference to the following article and paper at https://phys.org/news/2019-05-rare-earth-metals-atmosphere-glowing-hot-exoplanet.html and the paper at https://arxiv.org/abs/1905.02096v1 With regard to the extract in the article thus, "Therefore, its atmosphere reaches temperatures of around 4000 °C. In such heat, all elements are almost completely vaporized and molecules are broken apart into their constituent atoms" I find it rather difficult to imagine how any planet could form that close to its parent star and at such temperatures. Is this evidence for "planetary migration"? I also vaguely remember a proposition a few years ago, supporting the "planetary migrat…

I post a thread here in speculation proposing that gravity has a limited range I would like to ask some questions about the existing fact. My questions are : What does science think of infinite gravity " gravity being everywhere" ? How it is mathematically described "giving the idea that Newtonian gravitational law doesn't work for infinity distance" ? Is the idea of infinite gravity part of GR ? how it is described according to GR? Is there a proof for gravity being infinite in range ? Thanks,

I'm actually trying to find reasons why I was kicked out in an other forum a few years ago for asking a question. (the actual questions are numbered below) Heres what I was trying to ask in short: "the universe is expanding accelerating (galaxies are travelling away from each other at an accelerating speed). It has been suggested (or proven?) that this is caused by dark energy in the/our universe. In pop science, I've heard many times that: 'there must be something pushing this accelerating expansion and that something is dark energy' ". Ok, I have nothing against this idea, but what bothers me the most, is that I see there are two possibilities for the accelerating…

Is that because we analysed the mass of rotating matter around them, and extracted that they shall weight enough to attracted it, at a certain rotation speed? And after deduced from their looking size, by our observation, what density they should have? Where is the Science on that, and the part of relativity to it ?

Do we have any evidence that black holes actually emit radiation? If not, how can we prove it? If so, is Hawking radiation the best way we have to explain it?

In layman terms a horizon has a double characteristic: 1. it is a kind of limit to the observation, a surrounding circular line that defines the limit between the sky & the earth: what is observable & what is not 2. It is a boundary that is tied to the observer: you can walk toward a point of the horizon on Earth but you will never be able to reach it because the horizon is your particular horizon and it is moving with you. IOW the horizon is relative to the observer. Does an Event Horizon of a Black Hole follow the 2nd characteristic? And if not, why? I mean, if you try to approach the EH, will it go further the same amount as you have progres…

I know we are at the dawn of black hole exploration, but if (when) we advance at it, should we not be able to see if black holes can generate an Einstein-Rosen bridge? If such a bridge is possible, should we not one day be able to see matter jumping from hole to hole? Or would we have to test it ourselves, by visiting a black hole, and taking the leap?

If rockets use combustible fuel to generate lift, then is it possible to go all out electricity powered propulsion (to space) granted we have limitless energy.

https://phys.org/news/2019-04-tiny-fragment-comet-meteorite.html Tiny fragment of a comet found inside a meteorite: A tiny piece of the building blocks from which comets formed has been discovered inside a primitive meteorite. The discovery by a Carnegie Institution of Science-led team, including a researcher now at Arizona State University, was published April 15 in Nature Astronomy. The finding could offer clues to the formation, structure, and evolution of the solar system. "The meteorite is named LaPaz Icefield 02342," says research scientist Jemma Davidson of ASU's Center for Meteorite Studies in the School of Earth and Space Exploration. "The na…

My understanding is that observations supports that universe has a large scale structure consisting of large voids with lower density and filaments with higher density. How are the filaments affected by the expansion of the universe? My best guess is that the voids expand and the filaments stretch. This page forbes.com/startswithabang/cosmic-superclusters has a pretty good pop-sci explanation. Filaments stretching and dissolving can also be found for example here: medium.com/starts-with-a-bang. My reason for asking is that I’m somewhat confused by other descriptions where filaments consists of gravitationally bound matter, for instance wikipedia.org/Galaxy_fila…

can anyone or perhaps everyone explain to me why objects farther from the sun are colder in empty space? I understand that on Earth, in an atmosphere, that heat is dissipated as it is generated from a fire. However, ifn space with nothing to weaken and dissipate the infrared energy, it seems that distance from the sun wouldn't decrease the heat received as long as the object is in direct sunlight.

Here's a question related to the findings about black holes. The image released yesterday is of a black hole with a mass of 6.5 billion suns. That is apparently a mass sufficient to ensure that nothing, neither energy nor mass, can escape the black hole's gravitational pull. When the universe came into existence the total mass created was far greater than that of 6.5 billion suns. And the mass was concentrated in a volume as small or smaller than the volume of a black hole. So how could this mass overcome its mutual gravitational attraction to fly apart and create what we presently observe as the universe? There seems to be something of a conceptual contradiction he…

We know that the sphere inside the black hole itself is almost at absolute zero Kelvin. Totally cold. We also know that matter absorbed by the black hole is distributed equally on its surface. And we know it emits Hawking radiation when that happens. The theory is also that the temperature just beyond the event horizon (as I've understood it) is millions of degrees hot. But can we be sure of that? How do we know that there is heat around the hole? Could it not be that all the energy absorbed, escapes as Hawking radiation? (Sorry for any factual mistakes. I'm not a pro.)

In cosmological physics, and accordingly to inflation theory, what caused the field to expand ? I can understand the concept of quantum fluctuactions but i don't really understand how did the process of expansion started : "He found that if the universe contained a field in a positive-energy false vacuum state, then according to general relativity it would generate an exponential expansion of space."(Wikipedia). And why the expansion wasn't immediate but gave time to the Universe to become isotropic as shown in MWB ?

It is something I have always wondered about, since I was a child. What is there beyond spacetime? Back then I imagined a wall of rock, but I was only a kid, inspired by 70's sci-fi, so there you go... But what happens if a hypothetical spacecraft goes to the outer limits of space? Does it just stop or bounce back, because it is a part of spacetime and can't go beyond? Or does it continue into an endless empty void? Obviously nobody knows. But what does the theories predict?

We are just three months past the New Horizons' passage of Ultima Thule, but work from the earlier encounter at the Pluto-Charon continues. This article in Icarus is an example. "Charon displays extensive plains that cover the equatorial area and south to the terminator on the sub-Pluto hemisphere observed by New Horizons. We hypothesize that these plains are a result of Charon's global extension and early subsurface ocean yielding a large cryoflow that completely resurfaced this area leaving the plains and other features that we observe today. The cryoflow consisted of ammonia-rich material, and could have resurfaced this area either by cryovolcanic effusion similar…