Astronomers Have Come Up With a Better Way To Weigh Millions of Solitary Stars (vanderbilt.edu) 43
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."
Re: Just one problem (Score:2, Insightful)
Pointless comment. All measurements are indirect. The method which they calibrate against (rotational periods if binaries) looks pretty robust.
Re: Just one problem (Score:5, Informative)
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 (Score:5, Informative)
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.
"Truth observations"? (Score:2)
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
A more careful reading reveals the answer (Score:1)
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.
Re: (Score:2)
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 (Score:1)
One says to the other "Does this dark matter make me look fat?"
Re: (Score:1)
I can't see it but it's giving me a bit of a tug.
Re: (Score:1)
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 determ
Re: (Score:1, Interesting)
"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
This Is A Big Advance (Score:2)
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!
Really puts a new twist on fat-shaming stars. (Score:1)
but dark matter is definitely real, you guys (Score:2)