Incredible Earthlike planet has the density of solid lead

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At first, the exoplanet 55 Cancri e didn't look all that impressive: just another large rocky planet circling its star every couple of days. But a recalculation of its orbit has revealed that it's the galaxy's densest known planet.

A couple days' difference in orbital time can make a massive difference, as it did with 55 Cancri e. Astronomers originally thought it took 2.8 days to complete one revolution. But a pair of astronomers reviewed the data and realized the orbital period is actually much closer to just 18 hours. Closer observation with Canada's MOST telescope reveals the orbit is precisely 17 hours and 41 minutes, and that the planet's passage across its Sun-like star dims the starlight by about 0.02%.

That information is enough to figure out the planet's volume, which is only about 60% greater than that of Earth. Astronomers have already figured out 55 Cancri e's mass is a whopping eight times that of Earth, which means its density is much, much greater than that of Earth, and roughly comparable to a planet made out solid lead, and only slightly less than the ultra-compact core of our planet.


That sort of density would make for a distinctly unpleasant experience for any humans planning a visit, although we probably would be skipping over 55 Cancri e anyway. Because the planet is so closer to its star, its temperatures could reach nearly 5000 degrees Fahrenheit, far too hot to support any sort of atmosphere. But if you did visit the planet, you'd experience some amazing things in that millisecond or so before you melted, as researcher Jaymie Matthews explains:

"On this world — the densest solid planet found anywhere so far, in the solar system or beyond — you would weigh three times heavier than you do on Earth. By day, the sun would look 60 times bigger and shine 3,600 times brighter in the sky.


And 55 Cancri e is more than just an exoplanet curiosity. Because it's only located 40 light-years away and it's so close to its star, this planet is ideal for a ton of experiments into the nature of what lead researcher Josh Winn describes as "planet formation, evolution and survival."

Via Image by Jason Rowe, NASA Ames and SETI Institute and Prof. Jaymie Matthews, University of British Columbia.