Haha 3 billion years ago, I never listen to anyone starting off with that because they are only guessing
You think?
LIGO operates two gravitational wave observatories in unison: the LIGO Livingston Observatory (30°33′46.42″N 90°46′27.27″W) in Livingston, Louisiana, and the LIGO Hanford Observatory, on the DOE Hanford Site (46°27′18.52″N 119°24′27.56″W), located near Richland, Washington. These sites are separated by 3,002 kilometers (1,865 miles). Since gravitational waves are expected to travel at the speed of light, this distance corresponds to a difference in gravitational wave arrival times of up to ten milliseconds. Through the use of trilateration, the difference in arrival times helps to determine the source of the wave.
As first pointed out by [159, 160], by measuring the gravitational waveform during the inspiral and merger of a binary it is possible to make a direct and absolute measurement of the luminosity distance to a source. This is because the physics underlying the inspiral of a binary due to GW emission is well described and understood in general relativity. These sources thus offer an entirely independent and complementary way to measure the evolution history of our Universe. Standard sirens are physical, not astrophysical, measures of distance.
How do we know the distances across space? Astronomers start with an actual measurement of nearby stars via stellar parallax and use a stepping stone method to estimate the vast distances beyond the closest stars. It’s impressive, but the method is full of guesstimates, and thus cosmic distances are known to be uncertain. Now researchers from the Niels Bohr Institute at the University of Copenhagen say they’ve demonstrated that precise distances can be measured using supermassive black holes. The scientific journal Nature published their results, which they announced today (November 26, 2014).
To probe the usefulness of this method, the researchers used the central region of an active galaxy called NGC 4151. Its central region is the famous Eye of Sauron – not the one from Lord of the Rings, but a realm of space surely as formidable: a supermassive black hole at the center of NGC 4151, which we – at our great distance across space – see as still active. IN other words, unlike the dormant supermassive black hole at the center of our own Milky Way galaxy, the supermassive black hole in NGC 4151 still accretes – or accumulate – matter via gas clouds surrounding it. The researchers say it’s this process of accretion that makes it possible to measure the distance to the galaxy.
Darach Watson of the Dark Cosmology Center at the Niels Bohr Institute and study leader Sebastian Hönig, who now works at the University of Southampton in the U.K., worked together to obtain these results. Watson explained:
When the gas falls in towards the black hole, it is heated up and emits ultraviolet radiation. The ultraviolet radiation heats a ring of dust, which orbits the black hole at a large distance, and this heats the dust causing it to emit infrared radiation.
Using telescopes on Earth, we can now measure the time delay between the ultraviolet light from the black hole and the subsequent infrared radiation emitted from the dust cloud. The time difference is about 30 days, and because we know the speed of light, we can calculate the real physical distance between the black hole and the encircling dust.
He said that by combining the light from the two 10-meter Keck telescopes on Mauna Kea on Hawaii using a method called interferometry, his team was able make the two Keck telescopes act in a way that was equivalent to one telescope with a perfect 85-meter diameter mirror. According to their press release, that gave the two Keck telescopes:
… a hundred times better resolution than the Hubble Space Telescope — and allows them to measure the angle the dust ring makes in the sky, (about twelve millionth of a degree).
Then the researchers combined data about the angular size of the dust ring on the sky’s dome with the physical size of 30 light-days, to find the distance to the supermassive black hole in NGC 4151. Watson said:
We calculated the distance to be 62 million light-years. The previous calculations based on redshift (a change in the wavelength of the light due to the velocity of the object away from us) were between 13 million and 95 million light-years, so we have gone from a great deal of uncertainty to now being able to determine the precise distance. This is very significant for astronomical calculations of cosmic scale distances.
