Burned Out Stars Do A Deadly Last Dance

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“Well, I don’t know, but I’ve been told… You never slow down, you never grow old.” Well, Tom Petty might not ever grow old, but stars do. In this case it’s a pair white dwarf stars and they’re locked in a death dance that has them spiraling around each other in just 13 minutes. Astronomers estimated that in about 900,000 years the pair will merge… and what a party that will be!

Traveling in an orbit that’s currently carrying them at 370 miles per second (600 km/s), these two burnt-out stellar cores are heading towards a supernova ending. Right now the brighter of the pair is about the size of Neptune and carries about one quarter of our Sun’s mass. Its companion contains twice as much mass and is about the size of Earth. What’s peculiar is the incredible speed at which they are converging.

“I nearly fell out of my chair at the telescope when I saw one star change its speed by a staggering 750 miles per second in just a few minutes,” said Smithsonian astronomer Warren Brown, lead author of the paper reporting the find.

Using the MMT telescope at the Whipple Observatory on Mt. Hopkins, Arizona, researchers have been looking for just such eclectic white dwarf pairings. Because of their close proximity, they can only be separated spectroscopically and their relative motions then determined. Fortunately, this unusual set are eclipsing, doing their two-step at a very predictable rate. “If there were aliens living on a planet around this star system, they would see one of their two suns disappear every 6 minutes – a fantastic light show.” said Smithsonian astronomer and co-author Mukremin Kilic.

What’s really cool about this observing project is its implications as related to Einstein’s theories. Their movements should create wrinkles in the fabric space-time. These gravitational waves pull away at the energy – allowing the pair to get closer at each pass and their orbits to accelerate.

“Though we have not yet directly measured gravitational waves with modern instruments, we can test their existence by measuring the change in the separation of these two stars,” said co-author J. J. Hermes, a graduate student at the University of Texas at Austin. “Because they don’t seem to be exchanging mass, this system is an exceptionally clean laboratory to perform such a test.”

Just as soon as the pair emerges from behind the Sun, observing will begin again. Some models predict merging white dwarf pairs of this type could be a rare class of unusually faint stellar explosions called underluminous supernovae – or just the source of many other kinds of supernovae. “If these systems are responsible for underluminous supernovae, we will detect these binary white dwarf systems with the same frequency that we see the supernovae. Our survey isn’t complete, but so far, the numbers agree,” said Brown.

What can we say besides, “Last dance with Mary Jane… One more time to kill the pain… I feel summer creepin’ in.”

Original Story Source: Harvard-Smithsonian Center for Astrophysics.