Going to the races like Dover Downs and Daytona 500 and others when I was a child was a thrill unlike many. Seeing racers jockeying for first in rusty junkers ramming into each other at demolition derbies, to the masterfully powerful Japanese street racers blasting through avenues and coastal highways, to the beautifully elegant and dangerous European racing tracks sporting jet-fueled aerodynamic cars.
Even hermit crab racing gets me in the racing-spirit cheer. There’s no adrenaline like it.
As a race fan, however, I have to say “Sorry, Dale Earnhardt and Mario Andretti!” These binary stars are the fastest ones yet.
Astronomers at the world-renowned Massachusetts Institute of Technology (MIT) have discovered a new and powerful revelation. ZTF J1813+4251 (we will call it/them “ZTF”) is the latest duo of race stars. Like light and shadow, one cannot be without the other in this galactic race to see who the winner will be, if any. ZTF is named for the observatory in which it was discovered, the Zwicky Transient Facility.
The orbit of ZTF is a heart-stopping 51 minutes, enough to send any referee or judge spinning, literally. Astronomers at MIT and elsewhere found the binary system after its incredibly short orbit finally blinked into attention like an SOS for the realm of astronomy. It is a rare class of binaries called a “cataclysmic variable.” This is when a star of similar mass to our Sun orbits like a bearhug around a white dwarf – the burnt-out core of a star.
Cataclysmic variables occur when two stars race very close to each other. Over the span of billions of years, the white dwarf saps the materials from the opposing racer star. The white dwarf is like Racer X contesting Speed Racer: eventually “Speed Racer” grows into an even more variable state as growth and decay occur between them.
As one star builds momentum and mass, the other drains it like a vampire. This constant neck-and-neck racing of the development of one star vs. the fading of another gives instability of a cataclysmic level.
The white dwarf is roughly 1/100th the size of our Sun and the orbiting star is about the size of Jupiter. A “small” and dense, dead star burnt out and yet still functional becoming centric for the orbit of a developing star usually dooms that orbiting star to a “failed career”. A “Failed career” in the sense that the orbiting star will never support life to the level our Sun can. Talk about washout syndrome.
Luckily, due to the elliptical orbit of the “Speed Racer” star of ZTF scientists were able to calculate and gather data on the pair. Tens of years ago researchers at MIT and abroad predicted that these cataclysmic variables would transition into these ultra-fast and tight orbits. For the first time, we finally see this in action.
“This is a rare case where we caught one of these systems in the act of switching from hydrogen to helium accretion,” says Kevin Burdge, a Pappalardo Fellow in MIT’s Department of Physics, in a statement. “People predicted these objects should transition to ultrashort orbits, and it was debated for a long time whether they could get short enough to emit detectable gravitational waves. This discovery puts that to rest.”
ZTF is unique as it gives us a track-side seat to watch the event. Much of the “Speed Racer” star’s nutrients will be absorbed by the “Racer X” star and over time “Speed Racer” will become a helium-rich and dense star.
“Gravitational waves are allowing us to study the universe in a totally new way,” says Burdge, who is scouring the sky for the sources of gravitational disturbances like this unique binary. “This thing popped up, where I saw an eclipse happening every 51 minutes, and I said, ok, this is definitely a binary,” he added further.
In another 70 million years, the stars should gravitate closer, locking wheels in a death-till-us-part, neck-and-neck race to see who outpaces who in longevity. This will bring the “Speed Racer” star into a mind-bending 18-minute orbit.
This orbit time is unconscionable to most of us; imagine racing a NASCAR or Grand Prix in only a few seconds or minutes versus a few hours or even days (days or weeks for desert/terrain races and other endurance races).
That means if we could sustain such a gravitational force and weren’t pancakes, we’d have weeks (or even years!) in those 18 minutes in comparison to Earth hours. Almost like slipping into a black star, or black hole.
“This is a special system,” Burdge says. “We got doubly lucky to find a system that answers a big open question, and is one of the most beautifully behaved cataclysmic variables known.”
Call that a day at the races and place your bets now, you only have 69 million years to do so.
The research is published in the journal Nature.