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.

Colliding universes?

We know we are part of a massive universe, and it is scientifically accepted our universe started (as it has become now at least) out of a big bang, and it has been expanding ever since.

An obvious question, unanswered by science, is that there may be multiple universes.

This seems logical – people thought that Earth was the planet at the centre everything with one moon and one sun and a lot of distance lights in the sky. But as knowledge grew the location of our existence grew, hugely.

Now scientists think one possible cause of a cosmic ‘cold spot’ may have a collision of another universe with ours. It’s far from certain but it’s kinda interesting.

The Telegraph: First evidence of the multiverse? Scientists think Cold Spot in space could be colliding universes

A curious chilly area of space may have been created when a parallel universe crashed into our own, scientists have suggested, the first evidence that we may be part of a multiverse.

In 2015, astrophysicists discovered a strange barren area of the universe which was much colder than the rest of space, and seemed to be missing 10,000 galaxies.


The map of the cosmic microwave background (CMB) sky produced by the Planck satellite. Red represents slightly warmer regions, and blue slightly cooler regions. The Cold Spot is shown in the inset. Credit: ESA/Durham University

The ‘Cold Spot’ which is 1.8 billion light-years across, is the largest known structure ever discovered, yet appeared to contain 20 per cent less matter than it should, and has baffled scientists since it was recorded.

But now experts Durham University have come up with a solution which is not only out of this world, but out of this universe.

They believe that a parallel universe crashed into ours, causing a shunting action much like in a traffic accident when cars pile up on the motorway. The impact was so extreme that it pushed energy out of huge area of space, creating the Cold Spot.

Scientists now believe that if our universe ‘ballooned up’ into a vacuum after The Big Bang, then trillions of others could also have formed in the same way, creating a multiverse of other universes beyond our own space-time.

The Cold Spot could be the first evidence of the multiverse.


It’s well known that things collide inside our solar system. Our planetary system was formed out of collisions, and they still occur.

It’s also known (or claimed by scientists) that stars capture each other and some get consumed, so solar systems collide and merge.

And galaxies collide. That’s on a much more massive scale.

So I think that it is very likely that on another level, a universe level, collisions can also happen. Just as there a massive number of solar systems and galaxies, the chances are high there is a massive number of universes as well.

I’m very confident this is so. If you disagree prove me wrong.

Professor Tom Shanks in Durham University’s Centre for Extragalactic Astronomy, said: “One explanation for the Cold Spot is that it might be the remnant signal of the collision of our Universe and one of the trillions of others.

“If further, more detailed, analysis proves this to be the case then the Cold Spot might be taken as the first evidence for the multiverse – and billions of other universes may exist like our own.”

They may or may not find definitive proof there are many universes in my lifetime, but there almost certainly must be.

Is the Universe infinite?

Someone mentioned here recently that the Universe was either finite or infinite, I can’t remember which. They may have been right. Or not.

Space.com asks How Big is the Universe?

As technology has evolved, astronomers are able to look back in time to the moments just after the Big Bang. This might seem to imply that the entire universe lies within our view. But the size of the universe depends on a number of things, including its shape and expansion. Just how big is the universe? The truth is, scientists can’t put a number on it.

And it doesn’t take much googling to find that scientists don’t seem to be able to decide for sure whether the universe is finite or infinite.

What they can tell us is that the observable universe is huge and expanding.

Astronomers have measured the age of the universe to be approximately 13.8 billion years old. Because of the connection between distance and the speed of light, this means they can look at a region of space that lies 13.8 billion light-years away. Like a ship in the empty ocean, astronomers on Earth can turn their telescopes to peer 13.8 billion light-years in every direction, which puts Earth inside of an observable sphere with a radius of 13.8 billion light-years. The word “observable” is key; the sphere limits what scientists can see but not what is there.

But though the sphere appears almost 28 billion light-years in diameter, it is far larger. Scientists know that the universe is expanding. Thus, while scientists might see a spot that lay 13.8 billion light-years from Earth at the time of the Big Bang, the universe has continued to expand over its lifetime. Today, that same spot is 46 billion light-years away, making the diameter of the observable universe a sphere around 92 billion light-years.

But beyond our own wee earth-world everything we see is history. It takes about 8 minutes twenty seconds for light to get from our own sun to us, so if we look at the sun we see it as it was over eight minutes ago.

The size of the universe or whether it is finite or not depends on it’s shape, apparently.

The size of the universe depends a great deal on its shape. Scientists have predicted the possibility that the universe might be closed like a sphere, infinite and negatively curved like a saddle, or flat and infinite.

Possible space curvatures of the universe: Closed, Flat, Open

Sphere, saddle or flat

A finite universe has a finite size that can be measured; this would be the case in a closed spherical universe. But an infinite universe has no size by definition.

According to NASA, scientists know that the universe is flat with only about a 0.4 percent margin of error (as of 2013). A flat universe is an infinite universe; thus the size of the universe is infinite.

So science currently suggests that we have a ‘flat’ universe and therefore an infinite universe, but puts a margin of error on that, and there’s possibly things they don’t know about how the size and shape of the universe works.

It wasn’t long ago (in the whole scheme of things) that humans thought the Earth was the centre of the universe and flat.

Perhaps the same people who faked the moon landings may have also faked an ‘earth is round’ illusion.

Infinite Universe? Explains the difference between an Open (saddle) Universe, Closed (sphere) Universe, and Flat Universe. Also discusses the expansion of space-time.

Does whether the Universe is infinite or not matter to us?

For all we know the universe has already started to contract and we just can’t see that happening yet.

Around what?

NASA discovered that there was a satellite rock orbiting the asteroid that passed close by Earth earlier this week.

NASA has discovered a tiny moon 70 meters (230 feet) in diameter circling the asteroid that passed very close to Earth earlier this week, a situation that occurs in just 16 percent of the cases of known asteroids.

The tiny moon is orbiting the asteroid, which itself is only 325 meters (about 1,060 feet) in diameter.

If this asteroid went close enough to the moon it could get trapped into orbit.

Then there would be a moon around a moon around the Moon.

Around Earth. Around the Sun. Around the Milky Way. Around the Universe.

Around what?