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

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.