EU satellite Gaia to refine measurements of scale of universe

Source: BBC News

BBC News reports on the first image sent back from EU satellite Gaia, also nicknamed the ‘billion star surveyor’.  The mission is to create, “A very precise 3-D map of our Milky Way galaxy,” report states.

Astronomers also seek to ‘refine’ measurements as to the actual scale of the universe, using ‘stellar parallax’ to measure distance to a nearby galaxy as part of its 3-D mapping equation.  BBC reports on this highly sophisticated satellite that was launched in December of 2013:

By repeatedly viewing its targets, it should get to know the brightest stars’ coordinates down to an error of just seven micro-arcseconds – an angle equivalent to a euro coin on the Moon being observed from Earth.

One of the benefits of such study will be to refine the distance “ladder” used to measure scale in the Universe.

This ladder describes a number of techniques that lean on each other in a stepwise fashion to calculate the separation between Earth and some of the most far flung objects in the cosmos.

To the bottom of this ladder is the trigonometric parallax technique that Gaia will employ to measure distances.

Traditionally, this has only worked with stars inside the Milky Way. But Gaia’s advanced optics will for the first time extend parallax to stars in the LMC.

The LMC or Large Magellanic Cloud is a ‘companion galaxy’ to the Milky Way, according to this report that includes quotes from lead investigator Prof. Gerry Gilmore of Cambridge University.  BBC continues:

In the past, the cloud’s position has been determined only indirectly by studying the next rung up – the characteristic pulsations of particular stars known as Cepheids.

Having some parallax measurements in the LMC instead will allow astronomers to better calibrate the ladder and its various techniques, such as Cepheid pulsations. And that should mean researchers having more confidence in the figures calculated for even greater distances.

Prof Gilmore said: “Currently, we have precision distances – i.e. to 1% accuracy – to only one Cepheid star, which is Polaris (the North Star). So the whole distance scale to the Magellanic clouds depends on very shaky foundations. Gaia will be the ‘sanity check’ on the distance ladder where all of our different methods overlap.

“But Gaia will do even more because until now the accuracy to which we could work meant that we had to assume the Large Magellanic Cloud was a single point at one distance. We’ve had to average out properties. With Gaia, we will resolve out the LMC in three dimensions and that will tell us far more about its structure, and that will really open it up to proper scientific study.”

Read the full report, click here.


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