How far away are the stars? Scientists still don't know (Synopsis)

“Scratch a cynic and you'll find a disappointed idealist.” -Jon F. Merz

The stars overhead might twinkle and cause us to wonder what they are, exactly, but perhaps a more important question is to wonder where they are. If we can determine the distances to the stars, and then use those known distances to measure the distances to other galaxies, we can not only determine how far away they are, but determine how the Universe has expanded over the course of its cosmic history.

The construction of the cosmic distance ladder involves going from our Solar System to the stars to nearby galaxies to distant ones. Each “step” carries along its own uncertainties. Image credit: NASA,ESA, A. Feild (STScI), and A. Riess (STScI/JHU). The construction of the cosmic distance ladder involves going from our Solar System to the stars to nearby galaxies to distant ones. Each “step” carries along its own uncertainties. Image credit: NASA,ESA, A. Feild (STScI), and A. Riess (STScI/JHU).

This concept, of the cosmic distance ladder, was one of the most important astrophysical advances of the 20th century. Yet our attempts to measure distances to all but the very nearest stars have been marred by errors of all sorts, including some that our present technology can’t do anything about. But with the advent of the ESA’s Gaia satellite, we just might be prepared to overcome them all, and figure out, at last, how far away the stars truly are.

The "real" motion of Vega, just 26 light years away, as made from three years of Hipparcos data. Image credit: Michael Richmond of RIT, under a creative commons license, via http://spiff.rit.edu/classes/phys301/lectures/parallax/parallax.html. The "real" motion of Vega, just 26 light years away, as made from three years of Hipparcos data. Image credit: Michael Richmond of RIT, under a creative commons license, via http://spiff.rit.edu/classes/phys301/lectures/parallax/parallax.html.

Come get the full story on why this is such a hard problem, and after hundreds of years, we’re finally poised to solve it!

Categories

More like this

“We can only see a short distance ahead, but we can see plenty there that needs to be done.” -Alan Turing The Cosmic Microwave Background data gave us an unprecedented picture of our Universe in terms of accuracy, with the latest Planck results showing us our Universe is 68% dark energy, 13.8…
“No matter what technique you use, you should get the same value for the expansion rate of the universe today.” -Ben Hoscheit When you think of the Universe on the largest scales, you likely think of galaxies grouped and clustered together in huge, massive collections, separated by enormous…
“There are in fact 100 billion galaxies, each of which contain something like a 100 billion stars. Think of how many stars, and planets, and kinds of life there may be in this vast and awesome universe.” -Carl Sagan And at long last, Carl Sagan's estimates are finally out of date. It's not ~100…
"Space is big. You just won't believe how vastly, hugely, mind- bogglingly big it is. I mean, you may think it's a long way down the road to the chemist's, but that's just peanuts to space." -Douglas Adams Well, maybe "peanuts" isn't going to do. When you look out at the night sky, all sorts of…

Yay, another page is about to be turned.

My first thought on seeing how messy that parallax data is why you'd only use one satellite.

Wouldn't two on opposite sides of the earth's orbit give you the full possible resolution of the telescope and take the proper motion out of the equation completely? Would that just be too expensive or is there another reason not to do that?