Our Solar System’s Surprising Speed Through the Universe

Our Solar System orbits the galactic center at an estimated 792,000 kilometers per hour, taking 225 million Earth years to complete one galactic year. Meanwhile, the Milky Way as a whole is thought to be traveling about 2.1 million kilometers per hour.

While our star certainly isn’t lollygagging its way through the Universe, an analysis of radio galaxies by an international team of scientists suggests we may be moving even faster through the cosmos than anybody thought. A lot faster.

That would be noteworthy on its own, yet this contradiction also has “profound cosmological implications,” the researchers write, hinting at flaws in our current understanding of the Universe in a way that potentially challenges a longstanding principle that argues our position in space isn’t all that special.

Reevaluating Our Understanding of the Universe

“Our analysis shows that the Solar System is moving more than three times faster than current models predict,” says lead author Lukas Böhme, an astrophysicist from Bielefeld University in Germany. “This result clearly contradicts expectations based on standard cosmology and forces us to reconsider our previous assumptions.”

To reach this conclusion, Böhme and his colleagues analyzed the distribution of radio galaxies as seen from Earth. Radio galaxies are named for their emission of powerful radio waves, a type of electromagnetic radiation with low frequencies and long wavelengths.

Radio waves can pass through dust and gas that block visible light, thus carrying valuable clues about faraway galaxies we can’t see. Using radio telescopes, astronomers can study the vast, lobe-shaped regions of radio emission that characterize these galaxies.

Uncovering New Insights

With enough distant data points like these, it’s also possible to detect a faint bias resulting from our motion through the cosmos known as a source count dipole, which causes a few more radio galaxies to appear in our direction of travel than behind.

The effect is subtle, though, and requires highly sensitive measurements.

The new study offers an especially precise census of radio galaxies, the researchers explain, thanks to data from three radio telescopes, including the deepest wide-area radio survey to date, conducted with the Low-Frequency Array (LOFAR) radio telescope network in Europe.

The researchers also used a novel statistical approach to account for the multiple components of radio galaxies, whose complexity seems to be a key factor in precisely measuring what’s known as a cosmic radio dipole.

Combining data from all three telescopes, the researchers discovered a surprising degree of variability in the apparent distribution of radio galaxies.

Implications for Cosmology

The dipole they detected was 3.7 times more pronounced than what the standard model of the Universe predicts. The discrepancy exceeded five sigma, a statistical measure indicating high significance.

The standard model attempts to explain the history of the Universe since the Big Bang, and includes a fundamental assumption known as the cosmological principle, which states that matter is uniformly and homogeneously distributed when viewed at a large enough scale.

The new findings could be interpreted in more than one way, the researchers acknowledge, but they appear to be revelatory regardless.

“If our Solar System is indeed moving this fast, we need to question fundamental assumptions about the large-scale structure of the Universe,” says co-author Dominik J. Schwarz, a cosmologist at Bielefeld University.

“Alternatively, the distribution of radio galaxies itself may be less uniform than we have believed,” Schwarz says. “In either case, our current models are being put to the test.”

The study was published in Physical Review Letters.