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."

Comments

Just one problem

[Anonymous Coward]

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. 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. Verification is practically impossible.

Re:Just one problem

[Anonymous Coward]

I'm with you, but at least they are individually categorizing the data from each star right? Future models don't build themselves without big datasets, even if they are approximated. -xp64

Re: Just one problem

[Anonymous Coward]

Pointless comment. All measurements are indirect. The method which they calibrate against (rotational periods if binaries) looks pretty robust.

Re: Just one problem

[Tomahawk]

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.

Re:Just one problem

[ShanghaiBill]

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.

Re:Just one problem

[darenw]

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.

Two stars walk into a bar

[Powercntrl]

One says to the other "Does this dark matter make me look fat?"

Re:Two stars walk into a bar

[Anonymous Coward]

I can't see it but it's giving me a bit of a tug.

Re:Two stars walk into a bar

[Anonymous Coward]

You've never had a tug, miss bloke.

Re: Two stars walk into a bar

[Anonymous Coward]

...then the other star responds with a one line tweet, #DarkMatterMatters

And the whole universe proceeds to lose its shit.

Weigh?

[Anonymous Coward]

The weight of any star is 0 (in any units! :)

I'm glad the main article corrects this to "measuring the mass", though. But the headline should be updated to remove the word 'weigh'.

Re:Weigh?

[Anonymous Coward]

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.

Re:Weigh?

[Anonymous Coward]

Can I weigh in on this topic? The usage of "weight" is context sensitive, but the usage is abstractly the same. It weighs heavily on my heart that people so poorly understand English.

Re:Weigh?

[Anonymous Coward]

"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.

With this new technique

[Anonymous Coward]

They might be able to calculate your mom's mass.

Re:With this new technique

[Anonymous Coward]

That's flashing, not flickering...

Ok, you've got a star's mass, now what?

[Anonymous Coward]

What does this help us do? Detect anomalies?

Re:Mass

[Anonymous Coward]

Hmmm... I now see the Truth! I can now see that one can still get a Doctorate in Astrophysics from a box of Cracker Jacks.
I didn't know that.

What was the old way?

[Anonymous Coward]

Did they really retire the International Space Scale, or ISS?

I didn't know stars really twinkled!

[Anonymous Coward]

I was just yesterday teaching my daughter that the twinkling we see is either a physiological effect, or is added the atmospheric interference.

But the summary says the researchers are using the flickering and inferring gravitational magnitude from it. So the stars really do twinkle! I learned something inspiring today.

I thought you

[Anonymous Coward]

Could measure mass from temperature. The higher the temperature the higher the mass.

Devil's advocate

[Anonymous Coward]

This was covered in 2013. Gravitational lensing, which needs dark matter theory to be correct. The problem is, dark matter is just a theory to make up for what the math can't explain, which has never been proven. And then, supersymmetry is used to explain the "existence" of dark matter, which CERN has yet to find any evidence. I wish I could sign in for this, but I know that the "dazzle" vs. "baffle with bullshit" ratio is going to be too skewed to be worth it.

Re:Devil's advocate

[Anonymous Coward]

And why? Because space is fake. The Earth is flat. The eclipses prove it.

Take a good look at the winter Sun today and then explain it. You seem smart enough to see through BS, so when you think you have the answer, re-check. The tilt can't do it.

Re:Devil's advocate

[Anonymous Coward]

Everyone knows it's "turtles all the way down." There is no proof at all of dark matter and this form of measurement requires its existance.

Re:Mass

[Anonymous Coward]

Can I have some of those mushrooms you had before you wrote that?

"Truth observations"?

[sjbe]

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.

A more careful reading reveals the answer

[gerald.edward.butler]

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.

This Is A Big Advance

[careysub]

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!

Re: Mass

[Anonymous Coward]

Right on Step 1 you got it wrong, as "No Explanation" for the connection between EM and matter is wrong. QED governs this and has become one of the most accurate theories ever produced, making specific quantitative predictions that are accurate to levels smaller than parts per trillion.

Step 2 doesn't hold either, as there is extensive research into if particle masses are consistent and if counting particles gives a consistent mass, both because particle physics depends on such things and because there is interest in changing the mass definition to a count of particles. Physicists don't just make assumptions and move on forever, they remeasure these things whenever technology improves. Also, definitions of units don't change unless a lot of work has been done to show the new method is at least as consistent as previous methods (e.g. redefining electrical units has spawned a bunch of tests double checking fractional charges don't exist).

Step 3...the concept of binding and internal energy is already used in current theories and GR shows what momentum does to gravity (zero in simple cases, small in more complicated cases, e.g. with quadrupole moments... now backed up with direct measurements in experiment).

And the lameness filter seems to cut off a longer comment that points out errors in other steps. But it should suffice to say, if you make a fundamental mistake at every step of you logic and the premises are flat out wrong, you should take your own advice about re-evaluating your view of the universe.

Re:Mass

[Anonymous Coward]

Dark matter. Dark energy. Space is fake. Earth is flat.

If you watch corona lines during the solar eclipse, you would see that they appear to shift faster than the speed of light. But actually, they aren't hundreds of thousands of miles long, so they actually aren't moving that fast.

Einstein invented his theory to explain why the Michelson-Morley experiment detected no motion of the Earth through the aether. It took 18 years.

Re:Alternate hypothesis

[Anonymous Coward]

Stars are just lights. Space is fake. The Earth is flat.

Try explaining to your daughter why the winter Sun is weaker and yellower. It can't be explained by the tilt, or else the summer Sun would look like the winter Sun whenever it is low in the sky. We have sunrise and sunset every day, so there is nothing special about the tilt in that regard. It's the same atmosphere from the east as the south east.

Re: Mass

[Anonymous Coward]

The poster is either a troll or blind, so there is no re-evaluation of their view that is going to happen. For years they've posted as if photons made up of multiple parts based on the completely false premise that photons can only be measured via discrete electron transitions. No matter how much it is pointed out that there are a wide variety of ways to measure photons not based on that principle (most of which are simple enough to be available in an undergrad lab course...), they just parrot the same BS. Even here they repeat some of the same stuff that has been pointed out in detail to be wrong by people who should have known better than to be trolled.

Really puts a new twist on fat-shaming stars.

[Last_Available_Usern]

nt

but dark matter is definitely real, you guys

[slashmydots]

...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."

Re:but dark matter is definitely real, you guys

[Anonymous Coward]

...and not only real but it's Magic and there's zero proof of its existence

Even the flat earth BS has non-zero amounts of evidence, just in that case there is a fuckton of evidence pointing toward a round Earth. There is plenty of evidence of dark matter, in the same sense as any other field of science: it has predictive power and observations continue to match predictions. Competing theories have some evidence too, but not as much, requiring much more free parameters and only matching a small subset of data that dark matter can match.

missed a bunch of low density dust,

Do you know anything about what has been done to measure dust levels, and do you have anything in particular to dispute with estimates and error bars placed on those estimates?

do not know how gravity or black holes or universe expansion really works.

And yet every other case of testing GR has been producing amazing matches. Of course more data will be available soon with the continued work of LIGO and EHT coming soon.

But it's totally real and you should give scientists grant money to "study" it

Dark matter experiments don't get that much funding compared to other particle experiments. Even most the big ones that show up in the news are multipurpose experiments that got money to study a variety of things. And the scare quotes around "study" is absurd, as where the grant money goes (in the US at least) is public record

I use that term veeeeery generously considering it has never been detected

It has been detected a variety of ways on multiple macroscopic scales. It just has not been detected on a microscopic scale. Again, using absolutes like "never" is hyperbole at best.

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."

Science isn't built on faith. You're not asked to just trust that the dark matter is there. Papers have publicly available descriptions of methods, results, and how error bars were determined (especially in astrophysics that puts the vast majority of their work on ArXiV).

Regardless of your thoughts and problems, other scientists don't take it on faith as there are still multiple research groups working toward dark matter alternatives, including alternative gravity models and checking that the results of mass measurements are correction. In fact, TFA you are replying to one is exactly one such case.

At best, you've managed to make every single thing you said hyperbole, at worst every thing you've said is deliberate misrepresentation.

Re:Do the truffle-shuffle

[Anonymous Coward]

These are the same guys who can't get moon dust under their moon rockets.

Can't explain the winter Sun.

Can't explain the chromosphere light on the back of the moon during solar eclipse.

Can't explain the shadow on the moon spontaneously changing color during the lunar eclipse.

Can't explain why gyroscopes don't move to show the rotation of Earth.

But dark matter is totally real! And gravity! And Einstein's theories!

Re:Alternate hypothesis

[Anonymous Coward]

The better response is "Reality is fake".