Falsifying a young Universe. (re: Supernova 1987A)

Brother by e-mail writes: Astronomers measure distances using several different sized yardsticks.You do begin with parallax - the diameter of the earth's orbit as the base of an extremely tall & thin triangle. This works for nearby stars.Then you start by correlating the Apparent Magnitude against what a similarly composed star might look like at the distance. If the spectral signature is a good match to some of the known nearby stars, then you can make a fairly good estimate of the mass. Once you have the mass, then you can estimate the Absolute Magnitude. Using Absolute/Apparent you get an estimate of the distance.This works for stars that fall well within a known type of spectral signature, so it isn't useful in general.Another way is to use eclipsing binaries, like Algol in Perseus. You can get the masses of the pair with the period and angular separation and get a distance that fits all the data. The eclipsing feature allows you to measure brightnesses individually for binaries that appear too close together for our telescopes. A binary that doesn't eclipse doesn't provide enough information to scale the distance well.So now you can measure distances to clusters in our galaxy and some of them have what are called Cepheid variables. Cepheid variables falls into 2 or 3 kinds, all characterized by a periodic brightening. Each kind has a mass-period relationship that is fairly consistent, if they are solidly within that kind of Cepheid.Cepheid variables were then detected in the Magellanic clouds and thus the distance to these clouds was well defined. Astronomers found Cepheids in other nearby galaxies and thus those distances could be determined.However, the further out the particular yardstick you are using, the greater the uncertainty of the measure.At the long end of the scale, astronomers are using Type Ia Supernovae in super-distant galaxies to fit the redshift data more accurately. These guys are the ones who helped cosmologists to think that the rate of the expansion of the universe has been increasing.See http://www.astro.ucla.edu/~wright/cosmolog.htm for a lot of stuff on this whole shebang, so to speak.

RAZD writes:did you read the article on the SN1987A calculation? uses trig based on the timed difference in observed (1987) light pulses from the star and from the ring to find the {real} diameter of the ring (as the distance light was known to travel in that interval in 1987), and then trig based on that and the apparent angle of the ring ... 168,000 LY

RAZD writes:what I am looking for is a measurement to that star that involves the speed of lightgot anything on that?

We have determined the distance to the SN 1987A by comparing the
angular size of its circumstellar ring measured from an HST (Hubble Space Telescope) image ... with its absolute size derived from an analysis of the light curves of narrow UV lines ... measured with IUE
(International Ultraviolet Explorer). Our analysis confirms that the observed elliptical structure is indeed a circular ring at an inclination of 42.8 2.6. and provides a determination of its absolute diameter (1.27 0.07) x 1018 cm. Its ratio to the angular diameter of 1.66" 0.03" ... gives an accurate determination of the distance to SN 1987A ... = 51.2 3.1 kpc.... This value agrees very well with the determinations obtained from light-curve analysis of variable stars.