Dwarf Galaxy anyone? ;)
Astro-boffinry world rocked to its very core: Shock as Andromeda found to be not much bigger than Milky Way
The Andromeda galaxy is actually roughly the same size as the Milky Way, and may not engulf our galaxy when it is expected to collide in about four billion years time, according to new research. In other words, no, Andromeda is not the vastly larger sprawling galaxy we all thought it was. A paper published earlier this week …
COMMENTS
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Friday 16th February 2018 13:39 GMT Michael H.F. Wilkinson
Actually, the Andromeda Galaxy has two dwarf companions easily spotted with large binoculars, and can clearly be seen in an image I took with a 200mm telephoto (about 3 h total exposure time), as a fuzzy patches (one near circular, above and to the left of the core of M31, and one elliptical, below M31). Neither are called, Glod, I should add.
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Monday 19th February 2018 06:53 GMT Mark 85
Re: Nice photo!
How did you take a photo with 3 hours of exposure and not get the "arcs" you see when the earth rotates during that time?
They use what's called a clock drive to rotate the telescope/camera so that it cancels out the Earth's rotation. Here's link: https://en.wikipedia.org/wiki/Clock_drive
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Monday 19th February 2018 15:42 GMT dlc.usa
Re: Nice photo!
"They use what's called a clock drive to rotate the telescope/camera so that it cancels out the Earth's rotation."
Which is useless unless the instrument uses an equatorial mount to provide a suitable rotational axis, one parallel to the rotational axis of the Earth itself (https://en.wikipedia.org/wiki/Equatorial_mount)--portable telescopes can be tricky to set up with adequate alignment.
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Monday 19th February 2018 09:12 GMT Michael H.F. Wilkinson
Re: Nice photo!
Thanks everyone! I used a tracking mount to begin with, and this corrects for most of the earth's rotation. Without a so-called autoguider, there will be residual motion, so I combined 120 shots of 90 s exposure using so-called stacking software. I used a Canon EOS 550D with 200mm F/2.8 lens. Digital beats film by a mile for astrophotography, not just because it is much easier to combine multiple images, but also because a CMOS chip is far more sensitive to light. Film registers about 1% (at most!) of all photons hitting it, whereas a CMOS chip easily registers over 25%. Any dark current can be measured and subtracted too.
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Friday 16th February 2018 07:15 GMT Tom 7
Re: Films / TV-shows ever dramatize the collision of galaxies?
Even in galaxies things is mostly empty space. Take two galaxies and merger them and practically all the stars will miss each other. - our nearest neighbour is 4 light years away and the solar system up to Pluto is 0.0012 light years across. Things will get a lot brighter as gasses crash into each other and start new stars off. A few more comets and asteroids will be flung about but we are at far more risk from people who will start riots in the interstellar highways complaining about Andromeda's imperialistic intentions.
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Friday 16th February 2018 09:07 GMT fedoraman
Re: Films / TV-shows ever dramatize the collision of galaxies?
Yes, but...
You're right about there being very few stars smashing into each other, and the extra comets, and the hot gasses from dust and gas cloud collisions. But, depending on the geometry of the collision, one galaxy may be gravitationally disrupted - most of the stars in orbit around the central black hole will have their orbits radically altered by the approaching mass of the other galaxy. Many will end up being ejected from the galaxy collision altogether, though some do a quick out-and-back as they're recaptured by the new merged galaxies. There are some informative animations of this on YouTube. Highly speeded-up, of course ;-)
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Friday 16th February 2018 09:29 GMT kventin
Re: Films / TV-shows ever dramatize the collision of galaxies?
two questions:
1/ even though all stars will _miss_ each other, they will still _feel_ each other. in fact there's gonna be so much feeling, both galaxies will emerge profoundly changed. two stars don't have to hit it off, a close encounter is enough. also, massive black hole(s) in the centre? how close will they get?
2/ what about all the dark enigmatic stuff we're told is holding the galaxies together?
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Friday 16th February 2018 10:23 GMT Andy Non
Re: Films / TV-shows ever dramatize the collision of galaxies?
"we are at far more risk from people who will start riots in the interstellar highways complaining about Andromeda's imperialistic intentions."
On the plus side, the Vogons may have to re-route their hyperspace bypass away from Earth. Anyone checked on the planing permission status with our local office in Alpha Centauri?
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Sunday 18th February 2018 22:23 GMT Overcharged Aussie
Re: Films / TV-shows ever dramatize the collision of galaxies?
No they are all pretty much stupid and I mean all of them from all countries, especially the ones who think that islands will tip over from too many people and the others that think that there is a secure backdoor encryption system that IT people can just turn on.
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Friday 16th February 2018 08:51 GMT Anonymous Coward
Re: Films / TV-shows ever dramatize the collision of galaxies?
Well, there's the anime Gurren Lagann, in which giant (and I mean REALLY giant) robots use galaxies as weapons and throw them at each other in a fight that can be seen throughout the universe. Which violates more laws of physics than I want to think about.
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Friday 16th February 2018 09:29 GMT jake
Re: Films / TV-shows ever dramatize the collision of galaxies?
A '64 Ford Galaxy hit an old oak tree just up the road from here a year or so ago. Made a right proper mess, it did. The tree didn't survive, the car is still driveable. I wouldn't want to get hit with a Galaxy, regardless of what I was driving.
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Friday 16th February 2018 20:43 GMT jake
Re: @jake -- Films / TV-shows ever dramatize the collision of galaxies?
They don't merge. I drove in a Demolition Derby at the old Fremont Raceway Park once[0]. My Chrysler Imperial was the odds-on favorite to walk away with it, but I was knocked out early. The last two cars driving were Galaxys. They bashed each other for about another 20 minutes before settling on a draw ... And both drove down the street to the junkyard after the event.
The track is now a disused NOLF, and the former junkyard now houses several auto dealerships. And they wonder why so-called "sideshows" are such a problem in the East Bay ...
[0] I think this should be a requirement for receiving a license to drive. It's a real eye opener as to the laws of physics with regard to automobiles.
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Monday 19th February 2018 00:43 GMT Al Black
Re: 4 billion years...
The Sun will swell into a red giant, either swallowing Earth or at least completely scorching it, around five billion years from now. However, as the Sun grows gradually hotter (over millions of years), Earth may become too hot for life as early as one billion years from now. But Civilisation will be wiped out in less than 8000 years by the Y3K bug, assuming it cannot be averted by adopting a 5 or 6 digit Year....
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Friday 16th February 2018 08:32 GMT Duncan Macdonald
Re: If the mass is 800 vs 700...
The escape velocity depends on the size of an object as well as its mass. The black hole left after the collapse of a giant star is so much smaller than the original star that the escape velocity increases from a few hundred kilometres per second to the speed of light. Less dense objects have a lower escape velocity than dense objects of the same mass.
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Friday 16th February 2018 09:26 GMT IanRS
Re: If the mass is 800 vs 700...
Wrong. The escape velocity from a given body is sqrt(2GM/r), where M is the mass of the body you are trying to escape from, r is the distance from the centre of mass that you start at, and G is 6.67E-11. Density does not matter. Size does not matter other than letting you start from nearer the centre of gravity, but if you try and escape from two different size bodies with the same mass, starting at the same distance, then the escape velocity will be the same.
If you start at planetary orbit distances then the escape velocity required to get away from a black hole is the same as from a star of the same mass. It is only because the mass of a black hole is in such a small space that you can start closer which changes the escape velocity.
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Friday 16th February 2018 11:40 GMT Duncan Macdonald
Re: If the mass is 800 vs 700...
The escape velocity from an object is normally defined as the velocity required to escape starting from its surface. For two objects of the same mass but different densities, the denser one will be smaller so r in the term sqrt(2GM/r) will be less leading to a higher escape velocity.
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Friday 16th February 2018 11:41 GMT Anonymous Coward
Re: If the mass is 800 vs 700...
Wrong. The escape velocity from a given body is sqrt(2GM/r), where M is the mass of the body you are trying to escape from, r is the distance from the centre of mass that you start at, and G is 6.67E-11. Density does not matter.
Tell me about it. I find it impossible to get away when annoying fat colleagues start talking shit to me. Doesn't matter whether they extremely dense, or quite bright but exceptionally annoying, so density is not important. I can also confirm that it is more difficult to achieve escape velocity from those buggers who invade your personal space and poison your air, proving that distance is important.
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Sunday 18th February 2018 17:45 GMT Alan Brown
Re: If the mass is 800 vs 700...
"The black hole left after the collapse of a giant star is so much smaller than the original star that the escape velocity increases from a few hundred kilometres per second to the speed of light. Less dense objects have a lower escape velocity than dense objects of the same mass."
Wrong on a number of levels.
Firstly, only a small amount of the mass of the original star actually forms the black hole. The rest blows off into space.
Which means that anything orbiting will see its escape velocity _at that orbit_ decrease dramatically.
But if you setup shop in orbit close to the event horizon, then yes your escape velocity will be high. That orbit will be well inside the diameter of the original star. (gravity follows the inverse square law of distance)
Fun quiz for the day: If you were to go straight up from earth to the distance of the moon's orbit, then you'll experience a gravitational pull from the earth of about 1/3 G - and start coming straight down again as soon as you stop counteracting that pull and lose any outward momentum you had. It's a long way to fall. At times like this, how long will you have to consider all those things your mother told you before you discover if the ground will be friendly?
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Friday 16th February 2018 08:46 GMT Pascal Monett
"By measuring the escape velocity, scientists have recalculated the galaxy’s mass and size."
Um, I don't get it. How can they get a proper escape velocity measure if they've gotten the mass wrong in the first place ? Seems to me that those two things are related in a specific way. It's like throwing a ball four feet and then saying it was a bowling ball.
Doesn't make sense.
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Friday 16th February 2018 09:12 GMT fedoraman
Re: "By measuring the escape velocity, scientists have recalculated the galaxy’s mass and size."
I think it might have been a case of estimating the mass of Andromeda, from its brightness and assumed star population, and deriving an escape velocity from that. Now its a case of looking at high velocity stars in Andromeda (from the article), and seeing how their velocity distribution fits with the old and new escape velocity figure.
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Friday 16th February 2018 09:12 GMT S4qFBxkFFg
Re: "By measuring the escape velocity, scientists have recalculated the galaxy’s mass and size."
Assuming the object doing the escaping is much less massive than the object from which it's escaping, escape velocity is independent of the mass of the escaping object.
So, you can observe the speeds of stars that actually have escaped the galaxy, and those that haven't.
e.g. if star A is going at 1000km/s and has escaped, and star B is going at 500km/s and hasn't, you can say the escape velocity is between 500 and 1000km/s and therefore the galaxy's mass (strictly speaking it'll be a combination of mass and size/density) is between some two values.
Better explanations welcome.
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Friday 16th February 2018 17:33 GMT Tom 7
Re: "By measuring the escape velocity, scientists have recalculated the galaxy’s mass and size."
TBH the 'escape' velocity of a galaxy is probably not that easy to calculate - given the velocity of stars in galaxies has required the invention of dark matter to try and get the rotational velocities into some sort of agreement with Newton let alone Einstein.
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Friday 16th February 2018 13:21 GMT Doctor Syntax
Re: "By measuring the escape velocity, scientists have recalculated the galaxy’s mass and size."
"So, you can observe the speeds of stars that actually have escaped the galaxy, and those that haven't."
I'm not sure whether they'd spot the stars that have escaped but the maximum measured velocities of stars in the galaxy is likely to be just under escape velocity.
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Friday 16th February 2018 10:14 GMT steelpillow
"It completely transforms our understanding of the local group,"
And it will completely transform the mystery of Dark Matter. Up to now, only about a third of the calculated dark matter has been identified (gas, dust, rocks, rogue planetoids, etc). The remaining two-thirds is a topic of hot speculation about New Physics. Now, in Andromeda at least, that missing dark matter is, well... totally missing. There is no problem to solve. I wonder how other galaxies will now stack up.
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Friday 16th February 2018 19:00 GMT mr.K
Re: "By measuring the escape velocity, scientists have recalculated the galaxy’s mass and size."
I have no idea on what they actually did, but if you can determine the orbital speed you can also determine the escape velocity. This is since both only rely on the mass of what you orbit and the distance to the centre of it. You have to assume the orbit to be circular, or establish the entire orbit and with galactic years tending to be long years I don't think they have waited for that.
You also have the assumption that you orbit something where the mass is in the centre. Witch is of course not true for galaxies. The neat thing about calculating gravitational pull from within an object is that you can disregard all the mass situated further out from the centre than yourself, assuming the mass is symmetrically placed i.e. in rings or shells around the centre.* Thus when you start to escape you start to pass more and more of the mass further out to you that adds to the gravitational pull.
But I assume that if you manage to map the average orbital velocity on objects far enough out then you should be able to determine the entire mass. And if you map for enough orbits then you should be able to map the mass profile distribution. So easily I thought that I wonder why they either have gotten it wrong with that method or why they havn't done it before.
*Among other things enabling the fun fact that inside a hollow planet if it is a sphere you are weightless, regardless of where you are in it.
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Monday 19th February 2018 07:30 GMT The Oncoming Scorn
A lot of things totally destroy that episode to be fair (the opening few minutes & quelle surprise the opening few minutes of the space battle in Aftermath).
Somethings do make up for it however like.....
Technician: What is it?
Avon: Unfriendly. Which is fortunate, they'd be difficult to love.
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Friday 16th February 2018 09:52 GMT Anonymous Coward
What a waste of time and money
Get a grip guys and gals. 700, 800 times the number you first thought of.
WTF is the point in this Sh*t.
It's 4 billion years away and the politicians will probably destroy the planet within a 100 years. Isn't there something more useful that we can spend the money on?
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Friday 16th February 2018 14:12 GMT Hollerithevo
Re: What a waste of time and money
The point is that our monkey brains can actually understand and grasp entities so large that we can only use mathematics to understand the immensities. The point is that our minds can grapple with the universe. The point is that knowledge makes us more than beasts. The point is that we can, with our reason, go beyond the daily cares and understand a future we will not be part of. The point is that we love to stride across starry space and almost unfathomable energies, because we are human.
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Sunday 18th February 2018 17:56 GMT Alan Brown
Re: What a waste of time and money
Modified monkey brains
Which are modified insect eater mammilan brains
riding on reptile brains.
riding on fish brains.
And we're all riding on a large rock hurtling through the universe in in the general direction of the Great Attractor.
What that is, nobody knows. If we name it, do the stars start going out, silently, one by one?
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Friday 16th February 2018 14:34 GMT Doctor Syntax
Re: What a waste of time and money
"Isn't there something more useful that we can spend the money on?"
Back in the C17th people took to puzzling about these things. I suppose if you'd have been alive back then you'd have said much the same thing. It was one of the things which lead to our understanding of Newtonian mechanics which has served us well ever since.
People didn't stop thinking about such things and noticed a few discrepancies that didn't quite fit with the Newtonian view. Maybe if you'd been alive you'd have said the same thing then. Out of that came the theories of relativity and out of those came a whole lot of other stuff from nuclear energy to the clock corrections necessary for GPS to work.
But in your view it's still a waste of time and money. Me? I wonder what's the next lot of useful stuff that's going to come out of it.
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Saturday 17th February 2018 09:34 GMT Helena Handcart
Re: What a waste of time and money
Science was wrong, now it is less wrong. And will never be more wrong (or less right) than it is now. This is clearly A Good Thing.
As a bonus, the now less wrong science poses more questions; the answering of which will make science even less wrong as they get answered (wrongly or rightly).
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Sunday 18th February 2018 10:14 GMT Anonymous Coward
Re: What a waste of time and money
There is good science - like antibiotics, space probes to identify - and warn of - solar flares, cancer research, satellites to monitor the planet - and a thousand other branches.
And then there are the people who do completely pointless research into stuff that no one really has any interest in - except the other people doing the research into the same crap.
I'm not suggesting we don't expand our knowledge - I just don't see what the value is of knowing the weight of a galaxy that we will only ever encounter in episodes of Star Trek or Star Wars. Even with this latest announcement, the scientists aren't sure about the calculations - perhaps they are right, maybe, possibly - er, but it will definitely be worth investing another $50m to check. And it will keep them all in jobs for the next 20 years.
Now if someone has a specific scientific benefit that they can demonstrate from this research - I'm fully prepared to reconsider my view. Until then, all I can see is a couple of Bruce's with a cooler of stubbies sitting in Oz laughing at how easy it is to get money under the pretext of doing research. Bruce number 1 is in charge of Dark Matter research - he looks after the dunny, and Bruce number 2 looks after the light matter - the beer. Anyone for a Fosters (other beers are available).
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Sunday 18th February 2018 18:21 GMT jake
Re: What a waste of time and money
With that kind of attitude, humanity would still be hoping to find road-kill in East Africa ... and nipping back into the trees when the actual predator came back to recover the kill. For values of "living" that includes death before age 25, no need for a dunny, and a great fear of our their own shadow.
But you go ahead. Enjoy your beers, secure in the knowledge that you can find your dunny (hopefully!). The rest of humanity will continue to explore the horizon. It's one of the things that makes us human. Care to join us?
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Friday 16th February 2018 11:44 GMT JeffyPoooh
Science is proudly self-correcting
Science is proudly self-correcting, some fields much more often than others.
An extreme example is the ever-changing (nearly pseudo-science) field of Dietary-Health Advice. I once had to cough up some half-swallowed eggs in the middle of breakfast, because somebody had left the radio on, and The News mentioned that eggs had just been re-categorized as a carcinogen, again.
Astronomy has had its ^h Moments™. Remember Hubble (the person)? Crikey, he added orders of (numerical) magnitude to most of the basic assumptions.
An important conclusion is that the Scientific 'facts' du jour have a Half-Life. For eggs-as-food, it's about 18 months. Astronomy facts seem to typically last more than a decade.
This obvious conclusion has massive implications. It's horrifying when some people have too much 'Faith' in any particular Scientific result.
(Annoyingly necessary disclaimer: No, don't guess that I'm a Climate Skeptic. Wrong guess. Skeptic yes, on Climate not so much. That this disclaimer is necessary is actual a monumental problem with global impact.)
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Saturday 17th February 2018 22:51 GMT Yet Another Anonymous coward
Re: Science is proudly self-correcting
It's hardly a revolutionary reversal of a scientific fact.
A difficult to measure parameter of a distant object is 10% different from previous estimates.
If the depth of some part of the ocean was re-measured to be 10% different to what we have now - you wouldn't be running round saying water isn't real
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Friday 16th February 2018 14:05 GMT Ugotta B. Kiddingme
dodgy maths?
I generally suck at maths so I could be all wet, but it seems to me that there is a problem of accuracy in Kafle's statement.
Kafle FTA: "Our home galaxy, the Milky Way, is over a trillion times heavier than our tiny planet Earth..."
Space.com: "Recent measurements have weighed the galaxy at between 400 billion and 780 billion times the mass of the sun. "
Swinburne Uni: solar mass is "about 333,000 times the mass of the Earth."
quick back-of-the-napkin calc: Milky Way is roughly 1x10^17 Earth masses.
That makes the article statement off by several orders of magnitude. That scale of error is like saying "more than 1000 people live in China." It's technically true but not realistically close to accurate.UPDATE: Ah, I see my error now. Long form trillion, not "American trillion". See? Told you I suck at maths.
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Friday 16th February 2018 21:19 GMT jake
Re: dodgy maths?
I hear that a small percent of the folks living on a little group of islands in the North East Atlantic insist on using long trillions just to prove how superior they thought they were a century ago. These are the same people who invented Imperial Units, and then stole the Metric system from the French and try to lord it over those who choose not to.
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Friday 16th February 2018 18:21 GMT Kaltern
We're absolutely right. Until we're wrong.
Oh look, science people have once again had to admit they're wrong about things.
Now I absolutely respect science. And I respect that some things are more certain than others. However, I am still surprised when people adamantly refuse to accept that some things may be wrong, even after millennia of being shown otherwise.
Now, while I understand how peer review, scientific method and confirmation bias are all part of today's better way of sciencing. However, it's clearly evident that more and more scientists and other folks of reknown are always quick to belittle and outright deny the possibility of something being wrong. I wonder how much scoffing of the calculations for Andromeda's size is already happening, and how many are trying desperately to refute the proof?
It's small wonder us humans have come to an evolutionary stand still, when all that seems to matter is how much money we have, and how people cannot possibly be wrong.
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Saturday 17th February 2018 08:56 GMT Richard 12
Re: We're absolutely right. Until we're wrong.
Any new theory must be in agreement with all the observations recorded by humankind, as well as better predict observations at the edges of existing theories.
If the theory predicts that eggs fall upwards, it is wrong because they don't.
The reason why it is really hard to come up with a new theory of anything, is because we've made a rather large number of observations to a really high precision and accuracy over the last few decades.
Your new theory must predict that the measurement apparatus would give the same results that it actually did.
And again for all the other known experiments.
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Saturday 17th February 2018 13:30 GMT Destroy All Monsters
Re: We're absolutely right. Until we're wrong.
I wonder how much scoffing of the calculations for Andromeda's size is already happening, and how many are trying desperately to refute the proof?
Proofs exist only in completely made-up structures like mathematics and IT.
The world: not a video game where you can just query the mass of your opponent.
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Monday 19th February 2018 00:32 GMT Al Black
Super Galaxy Andromeda
but, but...97% of Astronomers agreed on the consensus that Andromeda was a Super-Galaxy! Does that mean scientific consensus is meaningless and actual data is required? That could be the start of a belated return to the Scientific Method and an acceptance that saying it in a Peer-reviewed magazine article doesn't necessarily make it so.