1.7 billion star map from Gaia

European Space Agency’s Gaia mission has just released a star map that details about 1.7 billion stars, a huge number, but just a small fraction of the septillion (or quadrillion) estimated stars in the Universe.

Also measured are the position and trajectory of more than 14,000 objects within our own solar system (mostly asteroids).

ESA: Gaia Creates Richest Star Map of Our Galaxy – and Beyond

ESA’s Gaia mission has produced the richest star catalogue to date, including high-precision measurements of nearly 1.7 billion stars and revealing previously unseen details of our home Galaxy.

Gaia was launched in December 2013 and started science operations the following year. The first data release, based on just over one year of observations, was published in 2016; it contained distances and motions of two million stars.

The new data release, which covers the period between 25 July 2014 and 23 May 2016, pins down the positions of nearly 1.7 billion stars, and with a much greater precision.

The new catalogue lists the parallax and velocity across the sky, or proper motion, for more than 1.3 billion stars. From the most accurate parallax measurements, about ten per cent of the total, astronomers can directly estimate distances to individual stars.

As well as positions, the data include brightness information of all surveyed stars and colour measurements of nearly all, plus information on how the brightness and colour of half a million variable stars change over time. It also contains the velocities along the line of sight of a subset of seven million stars, the surface temperatures of about a hundred million and the effect of interstellar dust on 87 million.

Gaia closed in on the positions of half a million distant quasars, bright galaxies powered by the activity of the supermassive black holes at their cores.

Gaia data were used to derive the orbits of 75 globular clusters and 12 dwarf galaxies that revolve around the Milky Way, providing all-important information to study the past evolution of our Galaxy and its environment, the gravitational forces that are at play, and the distribution of the elusive dark matter that permeates galaxies.

And also of our solar system:

Gaia also observes objects in our Solar System: the second data release comprises the positions of more than 14 000 known asteroids, which allows precise determination of their orbits. A much larger asteroid sample will be compiled in Gaia’s future releases.

There are a lot of observations and  measurements, and major discoveries are expected as scientists explore the newly released data.

As impressive as this is it is only scratching the surface of the Universe.

Space.com:  How Many Stars Are In The Universe?

The first sticky part is trying to define what “universe” means, said David Kornreich, an assistant professor at Ithaca College in New York State.

“I don’t know [the answer] because I don’t know if the universe is infinitely large or not,” he said. The observable universe appears to go back in time by about 13.8 billion years, but beyond what we could see there could be much, much more. Some astronomers also think that we may live in a “multiverse” where there would be other universes like ours contained in some sort of larger entity.

That sounds quite feasible, the big bang of our Universe may have happened in a bigger space time continum – going by the numbers of stars and galaxies there could also be millions or billions of ‘universes’.

This would mean the term ‘universe’ would need revision

Kornreich used a very rough estimate of 10 trillion galaxies in the universe. Multiplying that by the Milky Way’s estimated 100 billion stars results in a large number indeed: 1,000,000,000,000,000,000,000,000 stars, or a “1” with 24 zeros after it (1 septillion in the American numbering system; 1 quadrillion in the European system).

Kornreich emphasized that number is likely a gross underestimation, as more detailed looks at the universe will show even more galaxies.

Gaia has mapped a few drops in a huge cosmic ocean- or oceans.

Wikipdeia: Universe

The physical Universe is defined as all of space and time[a] (collectively referred to as spacetime) and their contents.

Such contents encompass all of energy in its various forms, including electromagnetic radiation and matter, and therefore planets, moons, stars, galaxies, and the contents of intergalactic space.

The Universe is often defined as “the totality of existence”, or everything that exists, everything that has existed, and everything that will exist.

A ‘multiverse’ renders those definitions obsolete. Perhaps things would be better described as ‘observable Universe’ and a greater whole universe that we can only guess about.


  1. Zedd

     /  April 29, 2018

    welcome home 🙂

  2. Alan Wilkinson

     /  April 29, 2018

    Are we still worried about finite resources?

    • Gezza

       /  April 29, 2018

      I think we leave that up to the individual, Sir Alan.

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