How do scientists know we’re approximately 300,000 light years away from the center of our galaxy and our galaxy is a spiral galaxy?
- Ronald 7Lv 72 months ago
By looking at it Skippy
- daniel gLv 72 months ago
Scientists don't even know where the center of the universe is,
Now our galaxy is a spiral,, a barred spiral.
Earth is near a half wáy out on the Orioñ arm, puts. Is just under 30,000 light years from the galactic barycenter.
- cosmoLv 72 months ago
Our knowledge of the Milky Way evolved in several steps:
1) more than 100 years ago, the Milky Way was thought to be only a few hundred lightyears across and we were in the center. This is because in blue visible light, the light from further stars was absorbed by dust, and this was not realized.
2) about 100 years ago, high-quality photographs showed that the dark regions in the Milky Way were actually dust obscured regions, and also high-quality images of "external" galaxies suggested that they were systems like the Milky Way, but at a distance.
3) about 90 years ago, it was realized that the motions of nearby stars were observed to be what you would expect if those stars and the Sun where all rotating around a distant center. Also, it was realized that the ensemble of Globular Clusters was centered on a region some tens of thousands of lightyears distant in the direction of Sagittarius.
4) sixty years ago: Once radio astronomy developed to the point of being able to observe the 21 cm line, the whole Milky Way could be seen. The development of infrared detectors allowed stars to be seen through the dust.
5) now: the GAIA satellite has given us accurate distances and velocities of about 2 billion stars in the Milky Way. The structure is therefore known with great accuracy.
- VelikovskyLv 72 months ago
We are 26,000 light years from the center of our galaxy, not 300,000.
- How do you think about the answers? You can sign in to vote the answer.
- RaymondLv 72 months ago
We can measure the position and relative motion of stars.
For that, we use the spectrum of each star (it gives us their composition, therefore their surface temperature, from which we calculate their luminosity - comparing that iwth their apparent brightness, we get their distance) and the shift in wavelength of key lines on the spectrum gives us their radial speed (relative to the direct line between us and them)
Using radioastronomy, we can do the same with the clouds - including the spiral arms that make up most of the galaxy. With baseline interferometry, radioastronomy has been able to get very precise positioning of discrete sources (the small clouds, the remnants of supernova stars, young cluster, etc.). Radiotelescopes can "see" through clouds and gasses, as well as detect transparent gases (it's a question of "tuning" to the appropriate frequencies - each type and temperature of gas has an optimum frequency to detect it)
Using this data, we can build a very good 3-D map of the Galaxy.
Then we look at all the galaxies we can see and note that the larger ones belong to three families, with roughly 3 to 5 types within each family (for example, tight spiral, loose spiral, barred spiral...).
We compare the 3-D map of our Galaxy with the types of galaxies we know, and the best match is a barred spiral galaxy with two long spirals arms (that start at each end of the bar) that wrap around roughly 270 degrees (three-quarters of the way around).
We are roughly 26,000 light-years from the centre.
- ZardozLv 72 months ago
As Morningfox said, not 300K. That being said, orbiting in the halo of our galaxy there are tight, gravitationally bound, spherical groups of thousands and even hundreds of thousands of stars known as globular clusters. We can measure the distance to them using the cepheid variables they house as a standard candle of distance. These clusters from a rough sphere around the center of our galaxy. We can calculate where that center is from knowing the radius of the ball.
We've developed more direct methods over the years, but I'm not familiar with them.Source(s): [n] = 10ⁿ
- MorningfoxLv 72 months ago
We are about 26,000 light years from the center, not 300,000 light years. The basic measurement methods are parallax, and the brightness of "standard candle" stars near the center. If we know the absolute brightness of a star, and the brightness as it appears to us, then we can figure the distance to the star.
- billrussell42Lv 72 months ago
it's not a simple answer, there are decades of observation and measurements behind this, but there is no doubt at this point.
go study astronomy for 10 years or so.
- JimLv 72 months ago
By taking measurements and doing calculations.