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Thread: The Astronomy Thread

  1. #81
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    Default Re: The Astronomy Thread

    Life could exist on planet orbiting 'white dwarf' star

    I find this article a bit confusing I have to say. As far as I can tell, a white dwarf is the remnant of red giant. It's surprising enough to find a planet survived that close to a red giant, but surely there won't be any water left, if there ever was any?
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    Default Re: The Astronomy Thread

    Yes those articles have very misleading titles, it's a common thing sadly (I mean astronomy articles for the big public are usually like that, meant just to attract the casual reader and have them look at the ADs).

    The article itself is pretty self-deprecating, to be honest, and that says it all. However, this whole "life could exist on this planet" crap is based on the infamous "Goldilocks zone", which I suppose you know what it is (it is also explained in the article itself); basically, for those who are not familiar, it refers to the "zone" around a star at which water could be find in liquid form on a rocky planet, this because of the average temperature on the planet itself being not cold enough to freeze water or hot enough to make it evaporate. That looks awesome, but it's a scam, basically. We do have the evidence of that close to us: both Mars and Venus do lie in the Goldilocks zone of the Sun, but neither of them have life or enough water on it (in whatever form). So there's much more than that of course (and IIRC we do have a few posts about that in the Mars vs Venus thread), but for the sake of completeness, a habitable planet would need at the least a stable atmosphere, a stable magnetic field, liquid water (or even liquid methane, possibly), seasons (probably), day/night cycle, etc. The list is partial but it gives the idea, saying that "life could exist on a planet because it's in the Goldilocks zone" is just like saying that I'm an immortal just because I haven't died yet.

    That being said, in this case the whole article is even more speculative, since:

    If confirmed, this would be the first time that a potentially life-supporting planet has been found orbiting such a star, called a "white dwarf".
    The possible planet, which is 117 light years away from Earth, is thought to be 60 times closer to the star than our planet is to the Sun
    Meaning like 2,5 MKm, I don't see how that could avoid being smashed by the star's magnetic field; Also, those stars do have a surface temperature of 150K at times, which means that it's bold to assume that you can have life at "only" 2,5 MKm from it (the Sun has a surface temp of about 5700 k, and it could literally burn everything at that distance). Totally speculative IMO.

    The research team do not have direct evidence of the planet's existence - but the movements of 65 Moon-sized structures orbiting the white dwarf's habitable zone, suggest it is there. The structures' distance in relation to each other does not change, suggesting that they are under the influence of the gravity of a planet in the vicinity.
    Again, absolutely speculative. They do not have any evidence of a planet being there, just a vague supposition.

    "Usually in astronomy, if we find one, it usually means that it's common," said Prof Farihi.
    this is just plain BS

    Now, to be fair to the astronomers who are behind the original discovery, I could say that finding "something, whatever it is" so close to a white dwarf is absolutely unexpected according to the traditional knowledge, hence why of the sensationalism around the news, but as far as my knowledge goes, there are more recent alternative theories which have been justified by the expanded understadning of the "Red Giant" state as we have it today. Basically:

    - the whole transformation process from a Yellow Dwarf into a Red Giant seems to be less traumatic and catastrofic that what we originally thought, in particular it seems to be involving much lower temperatures (in the order of less than 3.000 Kelvin) which means that a rocky planet would not be vaporized at those temperatures.
    - it is not excluded that a part of the original star material could remain, in form of gases, close to the newly formed White Dwarf, and in a relative short time it could accrete and form a "solid" body.

    So, if they actually find something (which has yet to be proven anyways) close to a White Dwarf, that would be something special for sure, but saying that "it could have life" when you didn't even know if its there and if it's a rocky planet, to BEGIN with, it's just one step below a plain lie and it's meant to attract attention and possibly funds, that is.
    Last edited by Flinn; February 16, 2022 at 03:34 AM. Reason: wrong calculation, reviewed
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  3. #83
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    Default Re: The Astronomy Thread

    Yeah, the article places too much importance on the location of the planet in the goldilocks' zone. Given its likely history, suggesting 'it could support life' is something that at least requires further explanation.
    "Lay these words to heart, Lucilius, that you may scorn the pleasure which comes from the applause of the majority. Many men praise you; but have you any reason for being pleased with yourself, if you are a person whom the many can understand?" - Lucius Annaeus Seneca -

  4. #84
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    Default Re: The Astronomy Thread

    Found this little gem today online, reportedly the most accurate depiction of how really crowded our system is.

    For a wider zoom, right click and open the image on a new tab
    Spoiler Alert, click show to read: 


    However, as you can see, the image is not really scaled on the size of planets and the Sun (for obvious reasons, if you scale everything to the Sun, either you need an image as large as a country, or you would not be able to see anything else than the Sun itself), but distances between the various orbits are indeed scaled.

    The image considers the whole bunch of objects which are 10 or more km wide, a total of 18.000 of them, but there are way more (in the order of millions of them) of smaller ones.
    However, the image is interesting because it gives a clear idea of how the Solar system is really structured. Basically, we have the area of the inner planets which is pretty much free from large debris; this is not only due to the Sun, but also, and primarily, because the rocky planets have absorbed most of the solid material which orbited in the inner part of the system.

    Then, just past Mars, we have a "tick" field of asteroids, the main belt, which in terms of mass is only 4% of the mass of the Moon, but that actually occupies the whole space, effectively making it a donut shaped structure. However, the image is of course misleading due to it being non-scaled, the real density is extremely low (just consider that plenty of probes have passed through it and none had even the slightest problem; as a matter of fact the probability of a probe/spacecraft hitting anything while passing there is so low that's is considered equivalent to zero).

    Past the Main belt there's the group of the giant gas planets, which again present a much less crowded area, with some distinctions, though. Jupiter has two groups of asteroids (the Greek ones and the Trojan ones) orbiting in its Lagrange points, basically preceding and following the planet. Besides, there's a large number of scattered objects which at times intersects the orbits of Neptune: one of this is Pluto, the well known dwarf planet, which in any case has zero changes of hitting Neptune, due to orbital resonances.

    Past this area, we have the Kuiper Belt, which has a even less dense population of objects, but with a much higher value in terms of mass (estimated 30 Earth masses in total) and with quite large objects such as Pluto, Eris, Haumea, etc.

    So as it is possible to see, the Solar system is very dynamic and complex and it's in constant evolution, and we are way far still from when we will be able to detect and monitor all the wandering and orbiting objects that inhabits it.
    Last edited by Flinn; February 25, 2022 at 09:24 AM.
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    Default Re: The Astronomy Thread

    I know I promised that I would have posted updates about the WEBB telescope, but I'm a busy dude and there are too many of them

    this one is a must see anyways, since it's a first hand comparison with what we have had so far



    The Large Magellanic cloud is at approx 160.000 light years from us, just saying ...

    for more info, link.
    Last edited by Flinn; May 04, 2022 at 05:31 AM.
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    Default Re: The Astronomy Thread

    A short video about the known star-sized black holes, pretty interesting IMO.

    Under the patronage of Finlander, patron of Lugotorix & Lifthrasir & joerock22 & Socrates1984 & Kilo11 & Vladyvid & Dick Cheney & phazer & Jake Armitage & webba 84 of the Imperial House of Hader

  7. #87
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    Default Re: The Astronomy Thread


    Supermassive black hole in Milky Way’s centre, Sagittarius A*, imaged for the first time

    If you are familiar whit the similar "picture" from the M87 Galaxy's supermassive black hole, you should know by now that what has been taken is not really a picture, but rather a radar image, taken on a specific wave length (it was 1 mm for the Sagittarius A*, IIRC).
    The reasons why we cannot observe directly a black hole are mainly because well, it's black (meaning that photons cannot escape its gravitational attraction, since the actual escape velocity is greater than the speed of light, the speed at which photons, the quantum of light, move across space) and because of all the matter (mostly dust and gases) who lies between those and the Earth. Distance could also play a major role, due to red shifting caused by distance.

    Anyways, what we can obtain is an image, an observation, of the ambient which is around those supermassive black holes, also known as accretion disk. In practice, as we said above, nothing can escape from a black hole, but at the same time the matter that is falling into the black hole (or better to say that passes through the events horizon) gets accelerated to very high speed (relativistic speed, actually) and thus its temperature rises to million of Kelvin degrees and starts to emit huge quantities of electromagnetic radiation (included light), that we could actually obverse.
    If you look at the image above, you can see the accretion disk that is surrounding the actual events horizon, the black area in the center.

    Why is it so important to study those supermassive black holes? Well, to begin with, the gravitational pull of those monsters is what makes galaxies rotate and consequently shapes them into spirals and thus influences every other aspect of their evolution, included single solar systems, how they form and how life can or cannot develop on them. Apart from this, the actual mechanics that regulate the physics of black holes are still largely speculative, we in fact call the "center" of the black hole a "singularity", which basically means that we don't know what that is, but only that the physics that we normally use (either Relativity/Gravity or Quantum Physics) do not apply there. As a matter of fact, many believe that to be the conjunction point of those two theories, and that should we understand them, we will unlock a whole new branch of the physics that will definitely give us the tools to efficiently travel the Space. The famous Nolan's movie, Interstellar is based specifically on this speculation.

    That being said, a few figures about "our" supermassive black hole, Sagittarius A*

    - 4.000.000 Sun masses (M87's one is way bigger, 4.000.000.000 Sun masses - for more details on M87 Galaxy and its supermassive black hole, follow this Link)
    - 44.000.000 km of diameter (accretion disk, approximately the same size of the orbit of Mercury around the Sun)
    - Rotational speed close to the maximum limit, speed of light (*see below)
    - Distance from Earth 26.000 light years (that is very close in terms of Space distances)

    * regarding the rotational speed of Sagittarius A*: this is what actually makes it very hard to "obtain an image". As a matter of fact the data of Sagittarius A* was taken before that of M87's, but since the latter rotates much slower (in the order of days, while the former rotates in the order of minutes) the matter that composes the accretion disk rotates mush slower as well, and thus it becomes easier to "spot it". Actually we did take much more pictures of Sagittarius A* than those of M87's (a dozen)


    Assembly of the images taken from Sagittarius A*

    Another peculiarity of Sagittarius A* seems to be that it actually rotates not on the same plane as the galactic plane, but almost at 90 and with one of the poles oriented towards the Earth. They have deducted this from the image of the accretion disk, but it's very controversial (and very counter intuitive) and still under hard debate.

    Another amazing fact about this study is the huge quantity of data necessary to obtain those images: the Event Horizon Telescope is what has been used, and data was so massive, that they could not send it via internet, but had to store them in special hard disks and physically assemble them all together at super computers. The joint effort has been immense, and that by itself is a big achievement for humanity at large.

    Some sources: Article 1, Article 2, Sagittarius A* wiki page.
    Last edited by Flinn; May 26, 2022 at 06:47 AM.
    Under the patronage of Finlander, patron of Lugotorix & Lifthrasir & joerock22 & Socrates1984 & Kilo11 & Vladyvid & Dick Cheney & phazer & Jake Armitage & webba 84 of the Imperial House of Hader

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