From White Dwarfs to Dark Matter Clouds, the Universe May Have Many Homes for Habitable Planets
What’s the News: While the Kepler spacecraft is busy finding solar system-loads of new planets, other astronomers are expanding our idea where planets could potentially be found. One astronomer wants to look for habitable planets around white dwarfs, arguing that any water-bearing exoplanets orbiting these tiny, dim stars would be much easier to find than those around main-sequence stars like our Sun. Another team dispenses with stars altogether and speculates that dark matter explosions inside a planet could hypothetically make it warm enough to be habitable, even without a star. â€œThis is a fascinating, and highly original idea,â€ MIT exoplanet expert Sara Seager told Wired, referring to the dark matter hypothesis. â€œOriginal ideas are becoming more and more rare in exoplanet theory.â€
How the Heck:
- Because white dwarfs are much smaller than our Sun, an Earth-sized planet that crossed in front of it would block more of its light, which should make these planets easier to spot. So astronomer Eric Agol suggests survey the 20,000 white dwarfs closest to Earth with relatively meager 1-meter ground telescopes.
- And because white dwarfs are so cool, a planet in a white dwarfs habitable zone would be very close, meaning its transit would happen very fast. Agol says weâ€™d only need to watch a star for 32 hours to pick up on any transiting, habitable planets.
- One leading theory about dark matter is that it’s made of theoretical particles called WIMPS (weakly interacting massive particles). Itâ€™s thought that when WIMPs collide (if, of course, they exist), they would explode. Astronomers think that these WIMP explosions could possibly heat a planet enough to make it habitable.
- There are no immediate plans to test the dark matter hypothesis, which is quite theoretical, and any plan to find dark matter-fueled planets would need to look far from here: our part of the universe doesnâ€™t have nearly enough dark matter to bring a planet to habitability.
What’s the Context:
- In other white dwarf news, astronomers have discovered a red dwarf in an extremely tight orbit with a white dwarf.
- And others are still wrangling over what dark matter really is.
- As for exoplanets, astronomers have actually seen one—as in, with visible light—orbiting its star.
Not So Fast:
- It’s not at all clear if white dwarfs have any planets, and if so, whether any of them could possibly support water or life as we know it. For one thing, planets in the habitable zone would be tidally locked with the star—permanent scalding daylight on one side; permanent frozen nighttime on the other.
- Taking 32 hours to find a planet orbiting a white dwarf may seem like a short time, but when you’re looking at tens of thousands of stars, it adds up. Agol told UW Today, â€œThis could take a huge amount of time, even with [a network of telescopes].â€
- And just like star-orbiting planets have their Goldilocks zones (not to hot or too cold), dark matter-containing planets would need the right amount of dark matter to be habitable. â€œItâ€™s not something thatâ€™s likely to produce a lot of habitable planets,â€ Fermilab researcher Dan Hooper told Wired. â€œBut in very special places and in very special models, it could do the trick.â€Â
References: Eric Agol. “TRANSIT SURVEYS FOR EARTHS IN THE HABITABLE ZONES OF WHITE DWARFS.” doi: 10.1088/2041-8205/731/2/L31
Dan Hooper and Jason H. Steffen. “Dark Matter And The Habitability of Planets.” arXiv:1103.5086v1
Image: NASA/European Space Agency