How is star distance, brightness and mass calculated/measured?

Question

Hey. Tried searching for this but was unsuccessful.

Now, to preface this, I know absolutely nothing about science. I’ve watched a few documentaries, but that’s as far as my knowledge goes.

I have been wondering about something for a while but whenever I try looking it up, the answers are far too complex for me to understand.

So my question revolves around stars. First, how is distance to stars measured? How do we know that it is reasonably accurate, and not a situation where said star was smaller and closer or bigger and farther away than previously thought?

Second, how is the brightness measured? I’ve heard stuff like “this and that star shines 100x brighter than our sun”. How can that be reasonably accurately measured over the vast distances we’re talking about in space?

Third, how can we measure or calculate mass of a star, given the vast distances?

I suspect those 3 questions might be somewhat linked, so I thought I’d ask all 3 in the same thread.

Now keep in mind, I do not understand calculus or math above algebra, so if anything like that is needed to understand, please dumb it down as much as you reasonably can.

Thankful for any replies helping me wrap my head around these concepts. Thanks in advace!

In: 9

Answer 1

It’s a complex topic for exactly the reasons you brought up, and astronomers have a variety of different approaches depending on what the object is and how far away it is.

Things that are (relatively) close can be measured by parallax. As Earth moves around the sun, their position in the sky (relative to things that are very far away) moves too, and this depends on how far away it is from Earth. (This method also depends on how far Earth is from the sun, which we learned in the 18th century using the transit of Venus).

Moderate distances can be measured with a “standard candle.” An object that we think has a fixed luminosity based on what we know about its physical properties and similar objects within the useful range of parallax. We can then use that fixed luminosity to back out the distance to Earth.

Longer distances use a variety of techniques, collectively called the Cosmic Distance Ladder.