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Astronomers Have Come Up With a Better Way To Weigh Millions of Solitary Stars (vanderbilt.edu)
Science_afficionado writes: By measuring the flicker pattern of light from distant stars, astronomers have developed a new and improved method for measuring the masses of millions of solitary stars, especially those hosting exoplanets. Stevenson Professor of Physics and Astronomy Keivan Stassun says, "First, we use the total light from the star and its parallax to infer its diameter. Next, we analyze the way in which the light from the star flickers, which provides us with a measure of its surface gravity. Then we combine the two to get the star's total mass." Stassun and his colleagues describe the method and demonstrate its accuracy using 675 stars of known mass in an article titled "Empirical, accurate masses and radii of single stars with TESS and GAIA" accepted for publication in the Astronomical Journal.
David Salisbury via Vanderbilt University explains the other methods of determining the mass of distant stars, and why they aren't always the most accurate: "Traditionally, the most accurate method for determining the mass of distant stars is to measure the orbits of double star systems, called binaries. Newton's laws of motion allow astronomers to calculate the masses of both stars by measuring their orbits with considerable accuracy. However, fewer than half of the star systems in the galaxy are binaries, and binaries make up only about one-fifth of red dwarf stars that have become prized hunting grounds for exoplanets, so astronomers have come up with a variety of other methods for estimating the masses of solitary stars. The photometric method that classifies stars by color and brightness is the most general, but it isn't very accurate. Asteroseismology, which measures light fluctuations caused by sound pulses that travel through a star's interior, is highly accurate but only works on several thousand of the closest, brightest stars." Stassun says his method "can measure the mass of a large number of stars with an accuracy of 10 to 25 percent," which is "far more accurate than is possible with other available methods, and importantly it can be applied to solitary stars so we aren't limited to binaries."
David Salisbury via Vanderbilt University explains the other methods of determining the mass of distant stars, and why they aren't always the most accurate: "Traditionally, the most accurate method for determining the mass of distant stars is to measure the orbits of double star systems, called binaries. Newton's laws of motion allow astronomers to calculate the masses of both stars by measuring their orbits with considerable accuracy. However, fewer than half of the star systems in the galaxy are binaries, and binaries make up only about one-fifth of red dwarf stars that have become prized hunting grounds for exoplanets, so astronomers have come up with a variety of other methods for estimating the masses of solitary stars. The photometric method that classifies stars by color and brightness is the most general, but it isn't very accurate. Asteroseismology, which measures light fluctuations caused by sound pulses that travel through a star's interior, is highly accurate but only works on several thousand of the closest, brightest stars." Stassun says his method "can measure the mass of a large number of stars with an accuracy of 10 to 25 percent," which is "far more accurate than is possible with other available methods, and importantly it can be applied to solitary stars so we aren't limited to binaries."
Pointless comment. All measurements are indirect. The method which they calibrate against (rotational periods if binaries) looks pretty robust.
One says to the other "Does this dark matter make me look fat?"
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DRM is like antifreeze, to the MPAA/RIAA it's sweet, to the consumers it's poison.
Indeed. They can accurately measure the mass of 2 binaries by their orbits (that was stated), so for every pair of binaries they have 2 stars they can look at to calibrate the technique.
This is basically guessing that one approach is better than the other, because there's no way to directly measure the mass of those stars.
Not true. You can accurately measure the mass of stars in binary and planetary systems by the orbital radius and orbital period.
Then you take these stars of accurately known mass and calculate their mass again using the "flicker" method and the "brightness" method. The flicker method works better.
So how do you know that binary stars flicker the same way that solitary stars flicker? Simple: If binary stars differed in their flickering behavior, then binaries with close and/or massive partners would be much more affected than a binary with a distant red dwarf partner orbiting at 1000 AUs. But they aren't. Ergo, flickering is an accurate way to measure stellar mass.
If I may weigh in here; a subtle distinction: Weighing is not bound by Earth's Gravity. Your Mass of 100Kg may Weigh "100Kg" on Earth, but only ~"16Kg" on the Moon. They are using the verb form here, and it is correctly used, even if it appears intuitively wrong. "Of Measuring the Mass" is awkward, and "Massing" is something unpleasant people do in preparation for an attack.
"To Weigh" actually has several related meanings, diverse enough to allow some latitude; for instance, one Weighs Anchors not to determine Mass, but to get the ruddy things off of the bottom. "To Weigh" also means to make a judgement: "Astronomers have weighed in with a better way to measure the mass of solitary stars." is perfectly fine; it is both alliterative and slightly punny.
I'm just glad that they didn't find a weigh to put that godawful Butthead Astronomer term in, the Parsec, a term derived solely to make some basic Maths simpler for Butthead Astronomers decades ago. Light Year is perfectly fine, it is based on a Fundamental Constant, the Speed of Light, and an agreed upon Constant, the Second, and was in use decades before Parsecs were.
Without a set of truth observations to evaluate the technique, there actually isn't a way to know that one method produces better results than another.
Not true at all. First off the methods used are actually based on evidence and methods we actually understand quite well. Second, when you have multiple methods you can compare them and when multiple methods give similar answers you gain confidence in the results. There are some logical inferences at times but always based on observations. Astrophysicists aren't idiots making stuff up out of thin air.
Verification is practically impossible.
You seem to be under the misapprehension that you need to be able to put something on a scale to know it's actual weight. Fortunately physics provides quite a lot more tools than that and some people much smarter than you or I understand how to use them.
Today, they can measure EXTREMELY ACCURATELY the mass of stars in binary systems. You can use this method on those same stars and get an idea of how accurate this method is. So, you validate this method using stars that you already know the mass for using the binary system method. Then, once you've validated the method, you can use it reliably on stars not in a binary system.
"The usage of "weight" is context sensitive, but the usage is abstractly the same."
Oh, this is fun! Let us now consider the Pound Cake, and Charlemagne.
Any good cook knows that the Pound Cake follows a strange Recipe, a quite old Recipe. A Pound each of Flour, Sugar, Butter, and Eggs. Most recipes might go four Eggs, three cups of Flour, two cups of Sugar, and four sticks of Butter, and that is the Way most Recipes still go. But the Pound Cake Weigh is different.
Charlemagne in taking Europe off of the Gold Standard and onto Silver had a problem: How to make sure Silver had the same value from Constantinople to Britain? Instead of doing the obvious thing, setting up arbitrary Values, he took a very small value, the weight of a Roman Denarii; about two grams. 240 of these Coins made up what was called a Pound or Livre, and the value of an Ounce of Gold, now a Currency of Account and not of Trade, was made equal to this value of 240 Denarii, which through corruption became the Penny. The Penny was the Standard of Weight, and it survives in the term "Pennyweight". Note that the weight of a Silver Shilling or Sou was derived from this as well, and made equal to the equivalent weight of the Gold Ounce.
Charlemagne, not singlehandedly, invented the concept of Standard Weights and Measures, and if a Pound was a good enough weight for Silver, it was a good enough weight for anything else, like Grains and liquids. A Pint's A Pound the World Around is an old saying, and the word Pint is derived from pound. (So is Punt, the Irish word for Pound.)
So a pound of Flour weighed the same as pint of Ale, and this was true from Constantinople to Britain. (Actually it wasn't, humans being the Scoundrels that they were and are...) BTW, another Standard came about- Ale.
Scales back then were of a Balance type, put a Pound Weight, referenced to a Standard Weight, on one side, and what ever balances on the other side, whatever weighs in, is also a Pound. So instead of measuring out doubtful cups of Flour and counting out Eggs, simply weigh the proportions, and so one of the earliest Standardized Recipes came to be, sometime in the 14th Century- The Pound Cake. Ale was the same; One weighed measure of Grain to eight weighed measures of Water. The value then of Bread to Ale was fixed as equal: The same amount of Grain went into a Pound Loaf of Bread as went into a Gallon of Ale.
Now the neat thing about this is that the Baked Pound Cake pretty much always turns out the same, and it doesn't matter much what the measuring weight actually is- the proportions are always the same. This is quite Modern thinking.
Given all that has happened in the last 1200 years, the Modern American Pound only weighs roughly 6% less than the Carolingian Pound. Oh there were Weighing variations along the way, like the London Pound vs. the Paris Pound, but over time, they tended to cancel out.
But Currencies were another matter.
Gold to Silver to Grain values remained roughly the same for over five centuries, but Currencies went to hell , and we can even pin the year down with accuracy. 1492
The Spanish Crown, in kicking the Moslems, (And Jews, again...), out of Spain, were sorely in need of funds. They engaged an itinerant Italian Captain to sail West to the Orient, a supposedly quicker route than overland East, in search of Trade. (Everybody who thought about it knew the World was a Globe; the only disputes were concerning the size.)
Spanish Ships started returning with Gold and Silver, (And slaves...), and threw Europe into a devastating Inflation, from which it never truly recovered.
And just about the only reminder that we have left of the brilliant Carolingian Weigh is the Pound Cake.
This is a very impressive advance in astronomy since now we can "weight" all main sequence stars, not just the ones in binary systems (although this is fair proportion of them).
And gravity wave astronomy is becoming routine now - in a few years the detectors will be making daily stellar merger events, and likely events that are a complete surprise to us.
The Twenty First Century is going to be an amazing period for understanding the Universe!
Starships were meant to fly, Hands up and touch the sky - Nicky Minaj
...and not only real but it's Magic and there's zero proof of its existence other than the fact that we didn't and likely still don't know how to measure stars' masses, missed a bunch of low density dust, and clearly do not know how gravity or black holes or universe expansion really works. But it's totally real and you should give scientists grant money to "study" it, and I use that term veeeeery generously considering it has never been detected. I cannot stand how scientists are always like "the total mass of the universe doesn't add up but rest assured, we know we're measuring it accurately and by the way we don't know how many planets are in our solar system."
How does one moderate a comment as "anti-insightful"?
You calibrate your fancy new method by applying it to stars that can also be measured by whatever is, at the time, the most trustworthy and accurate method known.
Sure, there's never any direct measurement of mass. Lots of things in science aren't measured directly, but are measured anyway, maybe to high accuracy, by having to be consistent with whatever we can measure directly.