The Universe is still expanding. As expected. - Bad Astronomy : Bad Astronomy
if the distance from the sun to the earth is represented by roughly 15 meters, . which of the following statements correctly describes the relationship between stars and constellations at what two celestial locations do the celestial equator and ecliptic coincide a. the daylight period of earth would be the same year round. Well, that's unfair: we have lots of clues, but we don't know what's . a name next to observations that the Hubble Constant varies with distance? . average radial velocity vr = to km/sec (in the Local Standard of .. (don't know how to do subscripts here) tells us anything about the equation of state of. That sum is called the proper distance between A and B. will grow over time, even excluding changes brought on by any relative velocity per se. . Since we don't want to wait billions of years, we use the more In any event, we can make redshift measurements at a bunch of different distances, and then.
Trans-galactic streamers feeding most luminous galaxy in the universe
You get the distance. Cepheids in NGC Cepheid measurements yield pretty good distances for nearby galaxies, but after a certain distance they are too faint to see.
We need a better rung on this distance ladder… and we have one. And we can see them out for hundreds of millions of light years, which is really really far away.
This makes them incredibly powerful beacons for astronomers. The cool thing is, NGC and others like it have Cepheids in them, and are also known to have hosted Type 1 supernovae!
Scientists suggest spacetime has no time dimension
Over ten years ago, a Type I went off in NGCand very precise measurements of it were made, including how far away it was. So for galaxies like NGC we have two methods of measuring distances which can be tied together in a single galaxy that can be observed with a single telescope, like Hubble. That means that uncertainties in the distance measurements using the two systems can be hammered away, and we get more reliable measurements.
And since we can see supernovae out to such fantastic distances, that means we can accurately measure the expansion of the Universe. Using supernovae to measure the distances of remote galaxies can be compared to the distances we get for those using the redshift, the Doppler-like shift in the starlight coming from those galaxies.
Adam Riess and his team observed quite a few galaxies in this way, and figured just how fast the Universe is growing to unprecedented accuracy. That means for every megaparsec about 3 million light years you go out, the Universe is expanding By knowing this number accurately, all we have to do is measure how fast the galaxy is moving away from us — a very easy measurement to make — and we can find its distance. But by nailing down all these numbers, we can in turn nail down such things as how much dark energy is in the Universe, and maybe even rule out some theories as to what this mysterious stuff is.
But then, we knew this. He and many other people did this by looking at a specific kind of star, called Cepheid variables.
Record-breaking galaxy found at the edge of the Universe - Bad Astronomy : Bad Astronomy
These stars literally pulsate, getting brighter and dimmer on a regular schedule. As it happens, how much they change in brightness depends on their actual brightness… and that means if you measure how much they change, and how bright they appear in our sky, you can figure out how far away they are.
And if they are in other galaxies, then you can tell how far away those galaxies are. You can measure the size of the Universe. Using this method which I explain in more detail in an earlier postif you want detailsthey figured out the Universe was expanding — the farther away a galaxy is, the faster it appears to recede away from us.
space expansion - How does the Hubble Redshift work? - Physics Stack Exchange
This is what led to the Big Bang model of the Universe, and essentially all of modern cosmology — the study of the origin, evolution, and properties of the Universe as a whole. Over the decades, that rate of expansion — called the Hubble Constant — has been measured many different ways.
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Using Cepheid variables is still a foundation of the work, though, and a new study just released by astronomers using the Spitzer Space Telescope show that the rate of expansion is What this means is that a galaxy one megaparsec away that is, 3. If you double the distance to 2 megaparsecs, a galaxy would be moving away at twice that speed, or This study is pretty neat.
Spitzer observes in the infrared, which can pass right through interstellar dust. That dust is like a fog, obscuring the visible light from stuff behind it, and it really messes with measuring brightnesses.