[HN Gopher] An Earth-sized rogue planet discovered in the Milky Way
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An Earth-sized rogue planet discovered in the Milky Way
Author : dnetesn
Score : 70 points
Date : 2020-10-30 10:20 UTC (1 days ago)
(HTM) web link (phys.org)
(TXT) w3m dump (phys.org)
| bookofjoe wrote:
| https://news.ycombinator.com/item?id=24946459
| 88840-8855 wrote:
| Earth-sized rogue planet number 3592 discovered. Wake me up when
| there is something exciting.
| lifeisstillgood wrote:
| It's a planet somewhere else in the galaxy. There are still
| people alive today who were born into a world where we thought
| there was just one galaxy, and only nine planets anywhere.
|
| We are like ants floating on a stick in the pacific, inferring
| New York's street plan from air currents.
|
| This shit is awesome.
|
| I don't believe you really are bored by this. Try affecting
| interest and enthusiasm - it generally works a lot better in
| life.
| nxmnxm99 wrote:
| More like ants in the pacific realizing there's another giant
| rock in the horizon they'll probably never reach, and likely
| has nothing worth looking at even if they do reach
| fuhrysteve wrote:
| If it's so uninteresting to you, why participate in the
| discussion?
| nxmnxm99 wrote:
| To comment on how uninteresting it is, obviously?
| mturmon wrote:
| We used to think the composition of the Sun would never be
| known because there was no way to take a sample. Now,
| because of spectroscopy, we know the composition of the Sun
| and all the planets. We're pretty clever when we put our
| minds to something.
| lifeisstillgood wrote:
| I don't understand that attitude - truly. Yes humanity
| might never get to another solar system, but then I am
| never going to walk on the Moon - it still looks beautiful
| in the night sky and the dream of getting there drove half
| of all science for centuries.
|
| We can make this ant colony better today.
| nxmnxm99 wrote:
| How does investing tons of valuable money and man hours
| into investigating said probably pointless rock make our
| any colony better today?
| lifeisstillgood wrote:
| >>> A rat done bit my sister Nell. (with Whitey on the
| moon) Her face and arms began to swell. (and Whitey's on
| the moon)
|
| Gil Scott-Heron is right - but also not. I was reminded
| of this watching First Man - and I realised that if 1960s
| USA had not funded a Moonshot, then would it have looked
| at itself and said "Hey our police force is used to keep
| 1/5th of our population in poverty through violence and
| our financial policies do the same. Let's fix that"?
|
| The thing about the space race was not how much money it
| got but how it was allowed to define problems using
| measurements to the millimetre and then solve them at the
| edge of what was technically possible.
|
| They were free of politics because no one had ever done
| it before.
|
| But politics is itself how we decide what the problem is.
|
| The concept that the US could have spent the moon money
| on fixing its self is ... a stretch.
|
| But to give in to that line of thinking is to abandon all
| hope.
|
| Not spending money on space is not the same as spending
| it on fixing our deepest problems.
|
| Until we can convincingly show we agree on what our
| problems actually are, I am reluctant to think we can
| spend billions fixing them.
|
| Instead let's fire spaghetti at the walls on local levels
| - maybe we can find solutions local interventions first.
| slg wrote:
| >There are still people alive today who were born into a
| world where we thought there was just one galaxy, and only
| nine planets anywhere.
|
| It might be a pedantic quibble, but you have the timeline of
| these discoveries a little messed up. There are people alive
| today who were born in a world in which we thought there was
| only one galaxy, but they also thought there were only 8
| planets at the time. Hubble proved there were other galaxies
| a few years before Pluto was discovered. You would have to go
| back to the 1850s to find anyone who thought there were more
| than 8 planets and only one galaxy. Back then dwarf planets
| and large asteroids were all categorized as planets which put
| us at over 20 planets before there was a reclassification.
| markkanof wrote:
| Are you sure about this? A google search indicates Pluto
| was discovered in 1930 and Hubble was launched in 1990.
| slg wrote:
| Sorry, I could have phrased that better to avoid the
| confusion. I was talking about Edwin Hubble the person
| who the telescope is named after. He showed that other
| galaxies existed in 1925. [1]
|
| [1] - https://www.discovermagazine.com/the-
| sciences/january-1-1925...
| lifeisstillgood wrote:
| Fantastic quibble - I stand corrected (I had Hubble in mind
| but did not know the 20+ planets part.)
|
| Perfect pedantry :-)
| slg wrote:
| It is always fun to bring up the 20 planets thing when
| people complain about Pluto not being a planet anymore.
| Lots of people have never even heard of fellow dwarf
| planet Ceres, but it spent almost as long as a full
| fledged planet as Pluto. The only reason most people
| defend Pluto's inclusion among planets and not Ceres is
| because Ceres was recategorized a century before most of
| us were born. It shows that the primary objection from
| laypeople is that we don't like when something we were
| taught as children changes.
| thaumasiotes wrote:
| I don't understand what the concept of a "rogue planet"
| is supposed to be. How do they differ from asteroids?
| lifeisstillgood wrote:
| >>> we don't like when something we were taught as
| children changes.
|
| The first rule of politics is don't take on any workers
| that appear in children's books (nurses, farmers, pigs
| that build straw houses etc). But it does remind me also
| of Hans Rosling explaining that the facts we learnt as
| kids (which countries were poor and starving) are today
| out dated.
|
| I guess if we can learn to let go of Pluto we can learn
| to accept the world as it really is.
| microtherion wrote:
| In the sense that it's detection of an object that's hard to
| detect, of which few are known, and that exists under unusual
| conditions, it's cool indeed.
|
| But from the point of view of people who find planets
| interesting primarily for their potential to harbor life, I
| would suspect that rogue planets are particularly
| inhospitable and thus not all that interesting.
| lifeisstillgood wrote:
| But ... Space 1999!!! :-)
| simlevesque wrote:
| Smallest one ever found.
| jcims wrote:
| That's no planet...
| hinkley wrote:
| Assuming we never crack FTL travel, I suspect rogue
| planets/planetoids will be part of our strategy to travel between
| the stars.
| Aerroon wrote:
| Finding and tracking these rogue planets today seems to be a
| bit like the astronomers of old figuring out the movement of
| planets in our solar system. It'll probably be very useful in
| the future. Maybe one day we might even be able to adjust the
| course of one of them.
|
| Related to this, I wonder what the minimum resources a rogue
| planet has to have for human habitation in the future.
| Obviously there won't be sunlight, which means that we will
| have to generate all of our energy in some other way. Nuclear
| fission? Fusion?
| has2k1 wrote:
| There is geothermal energy if it has a molten core.
| drevil-v2 wrote:
| To what purpose though? If you can steer a mass as big as a
| Earth sized planet then you might as well build a custom rig
| with all the trappings of First Class travel.
|
| Otherwise you are just a Hobo jumping on a passing train and
| hoping it ends up somewhere hospitable so that your great great
| great great great ... great... great... great... great
| grandchild, an lineage born and lived entirely on the train,
| has a place to call home.
| kadoban wrote:
| Depending on the tech, some mix of refueling station, colony
| or yeah passing train.
|
| Without FTL, to spread over the galaxy we'll need to adjust
| our thinking on long time-scales for any of it to make sense
| or be possible anyway. We'll be a different species really
| (or _several_ different species).
|
| If I were to bet, I'd say our more lasting contribution to
| the galaxy will more likely be mechanical (AI) descendants
| rather than ourselves, and next most likely would be barely
| recognizable biological dscendants (not necessarily that
| different from us physically, but in terms of society and
| mentality). That's all assuming we make it off of Earth and
| then away from Sol at all in any lasting way.
| carapace wrote:
| I think it's more likely that we "cure" aging and
| senescence than invent FTL.
|
| If you can live for 10,000 or 100,000 years then being
| limited to lightspeed isn't such a bummer. You can visit
| interesting places.
| HenryKissinger wrote:
| How far is it? The article doesn't say.
| ojnabieoot wrote:
| The distance is unknown[1] and if it were very far away, it
| actually could be a Jupiter-sized planet - I believe there was
| other circumstantial evidence that suggested this didn't "move"
| like a gas giant. I am not sure what a "Gaia proper motion
| measurement of the source" means [this is from the article] but
| I am not an astronomer and didn't read the whole article.
|
| Keep in mind how they detected this: they looked at the
| gravitational distortion of light caused by the planet's
| influence. We are used to seeing this gravitational lensing
| with black holes, which is visibly obvious even to an untrained
| human eye. The effect exists for every object with mass, but
| it's extremely tiny for planet-mass objects. For planet
| detection without a host star, it is the best measurement we
| have, but it's very finnicky and doesn't contain very much
| information compared to spectral analyses, motion around a host
| star, etc.
|
| From that paper's abstract:
|
| > Although in practice [rogue planets] do not emit any light,
| they may be detected using gravitational microlensing via their
| light-bending gravity. Microlensing events due to terrestrial-
| mass rogue planets are expected to have extremely small angular
| Einstein radii (~ 1 uas) and extremely short timescales (~ 0.1
| day). Here, we present the discovery of the shortest-timescale
| microlensing event, OGLE-2016-BLG-1928, identified to date (tE
| [?] 0.0288 day = 41.5 min). Thanks to the detection of finite-
| source effects in the light curve of the event, we were able to
| measure the angular Einstein radius of the lens thE = 0.842 +-
| 0.064 uas, making the event the most extreme short-timescale
| microlens discovered to date. Depending on its unknown
| distance, the lens may be a Mars- to Earth-mass object, with
| the former possibility favored by the Gaia proper motion
| measurement of the source. The planet may be orbiting a star
| but we rule out the presence of stellar companions up to the
| projected distance of ~ 8.0 au from the planet. Our discovery
| demonstrates that terrestrial-mass free-floating planets can be
| detected and characterized using microlensing.
|
| [1] https://arxiv.org/pdf/2009.12377.pdf
| azernik wrote:
| AFAIU, the star being lensed was within the Milky Way, so
| they could establish some limits on the size of the lensing
| planet. The upper size bound in the paper is 2 earth masses.
|
| (Jupiter mass does come up, but only in the context of a
| binary system - when ruling out that this planet is orbiting
| a star, they can only rule out a parent body larger than a
| few Jupiter masses.)
| ojnabieoot wrote:
| Thanks, I see that in the paper now - I didn't get further
| than the abstract :)
| part1of2 wrote:
| > However, theories of planet formation and evolution predict the
| existence of free-floating (rogue) planets, gravitationally
| unattached to any star.
|
| What's the theory that predicted this? After billions of years, I
| would expect all planets be attached (gravitationally) to a star,
| shouldn't they?
|
| > Indeed, a few years ago, Polish astronomers from the OGLE team
| from the Astronomical Observatory of the University of Warsaw
| provided the first evidence for the existence of such planets in
| the Milky Way.
|
| Wait. Evidence is not the theory. Did they predict this or
| discover it?
| ojnabieoot wrote:
| I don't quite understand why you're being so pedantic about
| this. The earliest reference I could find was from 1987,
| theorizing that proto-planetary objects could be ejected from a
| planetary disk and that this likely happened in our solar
| system due to sling-shotting from Jupiter[1]:
|
| > After Jupiter had accreted large amounts of nebular gas, it
| could have gravitationally scattered the planetesimals
| remaining nearby into orbits which led to escape from the Solar
| System.
|
| But this was purely speculative. It wasn't until many years
| later that the planet was actually observed.
|
| > After billions of years, I would expect all planets be
| attached (gravitationally) to a star, shouldn't they?
|
| I am not sure what you mean by that. All planets are formed in
| disks surrounding a star (or possibly a brown dwarf); rogue
| planets are planets that were able to escape the influence of
| that star. It might take billions of years before they get
| close enough to another star in the galaxy to fall into its
| influence.
|
| [1] https://ntrs.nasa.gov/citations/19870013947
| part1of2 wrote:
| The comment came off stronger than intended. It sounded like
| lazy journalism that made a claim, but then used a different
| conclusion. Thank you fr pointing me to the NASA site.
|
| > that were able to escape the influence of that star.
|
| What's the mechanism here? Is it something with greater mass
| that pulled it into an escape?
| Aerroon wrote:
| >> _that were able to escape the influence of that star._
|
| > _What 's the mechanism here? Is it something with greater
| mass that pulled it into an escape?_
|
| I'm a layman. Take what I say with skepticism, but I think
| in this case the parent poster was referring to any
| mechanism that ends up with a planet getting out of the
| orbit of the star. One such potential mechanism is
| gravitational slingshotting.
|
| Let's imagine you have a planet orbiting a star. A
| satellite flies in towards the planet. As the spacecraft
| passes by the planet, it gets some of the momentum of the
| planet as the planet is moving around the star. The planet
| loses that momentum. This increases the satellite's
| velocity in relation to the sun. The satellite can reach
| escape velocity and escape the influence of the star.
|
| Edit: alternatively to reading my explanation, you could
| read Wikipedia's:
| https://en.wikipedia.org/wiki/Gravity_assist#Explanation
|
| There's an amazing gif of Voyager 2's slingshots. Pay
| attention to the velocity as it passes planets: https://en.
| wikipedia.org/wiki/Gravity_assist#/media/File:Ani...
|
| I don't see why a similar thing couldn't happen to planets.
| simonh wrote:
| The down votes are a bit harsh. Theories of planet formation
| may be familiar to some of us but clearly not everyone, and if
| you aren't intimately familiar with orbital mechanics it might
| not be obvious that rouge planets are expected to be fairly
| common. We all get to be one of the lucky 10,000 from time to
| time.
|
| https://xkcd.com/1053/
| gpvos wrote:
| _> After billions of years, I would expect all planets be
| attached (gravitationally) to a star, shouldn 't they?_
|
| Planets are formed around stars, but some escape due to
| gravitational slingshotting etc.. Some of those might be caught
| again, but why would you think all are?
| canjobear wrote:
| The Founders
| awb wrote:
| Amazing discovery!
|
| On a related note, it's possible to have rogue solar systems as
| well: https://medium.com/starts-with-a-bang/ask-ethan-can-stars-
| es...
| netcan wrote:
| It's fascinating how fascinated we are with categories,
| typologies and their exceptions. It's like Sapiens crack,
| especially nerd sapiens.
|
| Here is is our linnaean classification of species. Look how
| these species are breaking the species barrier!
|
| Nature, meanwhile, isn't very fussy about the concept of
| species. It's not even strict about the concept of an
| organism.. even cells or any of the classifications we use to
| understand bundles of biology.
|
| A planet is a thing that orbits our sun. Hey, exoplanets! A
| planet is a thing that orbits a star. Hey, rogue planets. Hey,
| rogue solar system! Meanwhile, the universe isn't all that
| fussy about solar systems or galaxies.
| caryd wrote:
| I'm thinking the gravity would be too much, but it could be great
| for mining machines
| deepsun wrote:
| Can they compose dark matter?
| [deleted]
| hinkley wrote:
| The matter we can see only accounts for ~4% of the 'stuff' that
| orbital mechanics says is there, and the other stuff doesn't
| interact with light (so no clouds)
|
| There would have to be 25 times as many rogue planets as the
| mass of all systems, and most of the mass in a system is in its
| sun, so 25 Earths, Jupiters and Saturns are barely a blip.
| [deleted]
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