Where Are We in Space? Astronomers Update Their Celestial Frame of Reference

Simulation of the Universe’s structure
Simulation of the Universe’s structure
Illustration: Illustris Collaboration

How do you know where anything is in space? Sure, you can say, “Oh, that star, it’s the one in the middle of the Big Dipper,” but that’s not very useful in an era of incredible telescopes peeping at galaxies billions of light-years away. On January 1, 2019, scientists will adopt the newest, internationally standardized frame of reference to help locate things in space.


The third edition of the International Celestial Reference Frame, or ICRF-3, is the most up-to-date version of the International Astronomy Union’s standardized reference frame. Imagine the universe as a graph from geometry—scientists need a place to put the origin and axes.

“Nitty-gritty stuff like this is super important when you’re sitting on an Earth moving 70,000 mph around a star that is moving 450,000 mph around a galaxy center,” Grant Tremblay, astrophysicist at the Harvard-Smithsonian Center for Astrophysics, told Gizmodo.

Every physics problem starts with an innate step you might not realize: determining where the problem is taking place and the coordinates you’ll use to watch the physics happen. Astronomers need to do this, too, like drawing a graph in space.

The ICRF-3 is the latest update to our reference frame, following ICRF-1 from 1998 and ICRF-2 from 2009. It places the center of the reference frame at the Solar System’s center of mass, and is oriented based on the position of distant bright radio sources called quasars. Those measurements were made using Very Long Baseline Interferometry (VLBI), essentially a method of using the entire Earth as a telescope, collecting data from multiple radio telescopes and combining them to get the highest-resolution image possible.

This most recent frame derives from measurements of 4,536 quasars, all between 100 million and 10 billion light-years away. At these distances, they’re basically stationary. The most recent edition also takes the motion of our own Milky Way galaxy into account for the first time, according to a press release from the Helmholtz Centre Potsdam.

So, now we can determine where we are, more precisely than before, in the incomprehensibly vast cosmos. I hope this offers some comfort.


Former Gizmodo physics writer and founder of Birdmodo, now a science communicator specializing in quantum computing and birds


Dr Emilio Lizardo

Or you could just use this little rhyme:

Just remember that you’re standing on a planet that’s evolving
And revolving at 900 miles an hour.
It’s orbiting at 19 miles a second, so it’s reckoned,
The sun that is the source of all our power.
Now the sun, and you and me, and all the stars that we can see,
Are moving at a million miles a day,
In the outer spiral arm, at 40, 000 miles an hour,
Of a galaxy we call the Milky Way.

Our galaxy itself contains a hundred billion stars;
It’s a hundred thousand light-years side to side;
It bulges in the middle sixteen thousand light-years thick,
But out by us it’s just three thousand light-years wide.
We’re thirty thousand light-years from Galactic Central Point,
We go ‘round every two hundred million years;
And our galaxy itself is one of millions of billions
In this amazing and expanding universe.

Our universe itself keeps on expanding and expanding,
In all of the directions it can whiz;
As fast as it can go, at the speed of light, you know,
Twelve million miles a minute and that’s the fastest speed there is.
So remember, when you’re feeling very small and insecure,
How amazingly unlikely is your birth;
And pray that there’s intelligent life somewhere out in space,
‘Cause there’s bugger all down here on Earth!