2 ms·

"Astronomers are making the first exact maps of the Milky Way: locations of stars in three dimensions..." I thought that "standard candles" were required to es

by chasil 3y ago

"Astronomers are making the first exact maps of the Milky Way: locations of stars in three dimensions..." I thought that "standard candles" were required to estimate the distance to any region of space? How can the distance to arbitrary stars be determined without these markers?

thatswrong0 3y ago
Gaia is orbiting around the L2 Lagrange point. As it traverses its orbit, the stars will appear to wiggle (relative to their previous recorded position) because of the stellar parallax effect. This (along with precisely knowing Gaia's orbit) enables scientists to accurately measure the distance to the star - if it wiggles more, it's closer. If it wiggles less, it's further away. There is a limit to this method of measurement, based on the accuracy of the telescope. For Gaia: > The European Space Agency's Gaia mission is expected to measure parallax angles to an accuracy of 10 microarcseconds for all moderately bright stars, thus mapping nearby stars (and potentially planets) up to a distance of tens of thousands of light-years from Earth. The Milky Way is about 100,000 light-years wide. So it is able to accurately measure the distance for a _lot_ of stars around us in our galaxy. This video probably explains it better: https://www.youtube.com/watch?v=Jdy09y0A4t0 https://www.youtube.com/watch?v=Jdy09y0A4t0
- vikingerik 3y ago
  To be clear (and the video isn't), the parallax is observed and calculated mostly from the diameter of Earth's orbit, with observations made six months apart. Gaia's L2 orbit is a much smaller factor, on the order of 1M km compared to Earth's orbital diameter of 300M km.
Vecr 3y ago
> Astronomers are making the first exact maps of the Milky Way: locations of stars in three dimensions Maybe science fiction authors can stop making up locations entirely now.

2 ms·

"Astronomers are making the first exact maps of the Milky Way: locations of stars in three dimensions..." I thought that "standard candles" were required to es

by chasil 3y ago

thatswrong0 3y ago
Gaia is orbiting around the L2 Lagrange point. As it traverses its orbit, the stars will appear to wiggle (relative to their previous recorded position) because of the stellar parallax effect. This (along with precisely knowing Gaia's orbit) enables scientists to accurately measure the distance to the star - if it wiggles more, it's closer. If it wiggles less, it's further away. There is a limit to this method of measurement, based on the accuracy of the telescope. For Gaia: > The European Space Agency's Gaia mission is expected to measure parallax angles to an accuracy of 10 microarcseconds for all moderately bright stars, thus mapping nearby stars (and potentially planets) up to a distance of tens of thousands of light-years from Earth. The Milky Way is about 100,000 light-years wide. So it is able to accurately measure the distance for a _lot_ of stars around us in our galaxy. This video probably explains it better: https://www.youtube.com/watch?v=Jdy09y0A4t0 https://www.youtube.com/watch?v=Jdy09y0A4t0
- vikingerik 3y ago
  To be clear (and the video isn't), the parallax is observed and calculated mostly from the diameter of Earth's orbit, with observations made six months apart. Gaia's L2 orbit is a much smaller factor, on the order of 1M km compared to Earth's orbital diameter of 300M km.
Vecr 3y ago
> Astronomers are making the first exact maps of the Milky Way: locations of stars in three dimensions Maybe science fiction authors can stop making up locations entirely now.