July 26, 2017

Astro Video of the Week: White Dwarf, Brown Dwarf

+19th magnitude white dwarf WD 1202-024. (SDSS)

Wanna see a wacky planetary system? A recent discovery by MIT, Harvard/Smithsonian Center for Astrophysics and Bishop’s University researchers was announced at the 200th AAS meeting in Austin, Texas and made the news rounds last week, but I don’t think folks really got a good grasp on just how strange a binary system WD 1202-024 really is.

Let’s break it down. The primary component in the WD 1202-024 system is a white dwarf star about 40% the mass of our Sun, a degenerate star of compressed matter about the size of the Earth. Whizzing around that is a brown dwarf about 67 Jupiter masses and about the same diameter as Jove… much larger than the primary, but much less massive. And both are — get this — only 193,000 miles apart… about two thirds of the Earth -Moon distance. This means that the brown dwarf is hauling interplanetary butt around the primary once every 71 minutes (a shorter period than satellites in low Earth orbit) moving at 62 miles per second.

Located 270 light years distant in the constellation Virgo, WD 1202-024 was spotted by the Kepler Space Telescope on its extended K2 mission scanning the plane of the ecliptic. Kepler looks for transiting objects, or stars that dip in brightness as an unseen companion crosses in front of our line of sight, and the wacky worlds of WD 1202-024 certainly qualify.

I wouldn’t place too much stock in the statement proclaimed in many news articles that the brown dwarf companion was once in the atmosphere of the red giant star that became the current white dwarf. More likely, the brown dwarf migrated inward to its present orbit.

Both objects must dominate each others sky, as the white dwarf raises the daytime temperature of the brown dwarf to a blazing 5250 K or nearly 9,000 degrees Fahrenheit. It has a long scorching life ahead, as the white dwarf ember won’t cool down to a black dwarf cinder until a few trillion years from now, longer than the current age of the Universe.

It’s a bizarre Universe for sure. What other strange worlds await?

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