I have a few pet objects in astronomy that fascinate me endlessly. One of these is brown dwarfs, objects that are bigger than planets, but too small to be bona fide stars. They are much cooler and fainter even than dinky red dwarfs, making them very difficult to find… unless you are WISE:
[Click to embiggen.]
See that pale green dot in the middle? That’s a brown dwarf! I know, it’s not brown, it’s green, but that’s kosher since brown dwarfs are really magenta.
OK, hang on a sec. I’ll explain that in a minute.
The important thing is that this image shows a very nearby brown dwarf, maybe 18 – 30 light years away (the distance is hard to determine, but observations taken over the next year or so should pin it down). That’s really close! The nearest known star, Proxima Centauri (a faint red dwarf) is 4.2 light years away, and only a few hundred stars are within 30 light years. That makes this brown dwarf, named WISEPC J045853.90+643451.9 (after its location in the sky), one of the closest stars known.
You’d think think we’d have a pretty good idea of all the stars near us, since they’d be among the brightest in the sky. But in fact brown dwarfs are so faint that to optical telescopes they can escape detection even if they’re our cosmic neighbors. WISE, however, looks in the infrared, where brown dwarfs glow considerably brighter.
And that brings me to the weird colorful adjectives we use for these objects.
The color of a star depends mostly on its temperature (and the way our eyes see the mixed colors from stars, which is complicated, and I will ignore here). Very hot stars are blue, middlin’ hot are white (like the Sun), cooler ones are orange, and very cool ones are red. Brown dwarfs are even milder than red dwarfs, and their spectrum actually peaks in the infrared.
But it’s a bit more complicated than that. Brown dwarfs are so cool that actual molecules can exist in their atmosphere, like water (well, steam), titanium oxide, ammonia, even hydrogen sulfide (which makes eggs smell rotten). These molecules absorb light at certain colors, and that absorption can really mess with a brown dwarf’s color. Sometimes, a cooler brown dwarf can actually be more blue than a warmer one, because those molecules absorb the redder light the object emits. It’s weird. So a lot of these brown dwarfs actually would appear to be magenta to the eye.
So why are they called brown dwarfs? Blame SETI’s Jill Tarter. She just wanted a name for the critters, and compromised on a color between red and black. Stars can’t be brown, really, but the name stuck.
Anyway, if they’re magenta and not brown, why does that one look green in the WISE picture? It’s because WISE look in the infrared, which our eyes can’t perceive. So when they make pictures form the data, astronomers use false colors; they let blue represent the shortest IR wavelength WISE sees, green the intermediate, and red the longest wavelength — this corresponds to visible light, with wavelength getting longer from blue to green to red. It’s a shorthand that astronomers use that makes images like this easier to interpret.
As it happens, brown dwarfs at a certain temperature emit very strongly in the infrared wavelength astronomers code as green in the WISE images. So finding brown dwarfs is actually not too hard: just look for green stars! Those are really the magenta brown dwarfs.
See?
Anyway, I for one welcome WISEPC J045853.90+643451.9 to our little clan of nearby stars, and hope we find more. For quite a long time I’ve wondered if Proxima Cen really is the closest object to the Sun, or if there might be a faint brown dwarf even closer. Since brown dwarfs aren’t considered stars, Proxima may yet hold on to the title of "nearest star". But if we ever do find something even closer, it would literally be very cool.
Related posts:
- Two nearby galaxies peek out through the dust
- A WISE flower blooms in space
- The seven WISE sisters
- Three views to a comet
- I Spy With My Little Eye… [Last Updated On: November 7th, 2009] [Originally Added On: November 7th, 2009]
- A Crack Opens in the Ethiopian Landscape, Preparing the Way for a New Sea | 80beats [Last Updated On: November 8th, 2009] [Originally Added On: November 8th, 2009]
- The Politics of Addiction | The Intersection [Last Updated On: November 8th, 2009] [Originally Added On: November 8th, 2009]
- Finally! An iPhone App That Lets You Track Your Bathroom Habits | Discoblog [Last Updated On: November 8th, 2009] [Originally Added On: November 8th, 2009]
- Don’t Pack Your Bags Yet—New Planet-Finder Hobbled by Electronic Glitch | 80beats [Last Updated On: November 8th, 2009] [Originally Added On: November 8th, 2009]
- In Controversial Scent Lineups, a Dog’s Nose Picks Out the Perp | 80beats [Last Updated On: November 8th, 2009] [Originally Added On: November 8th, 2009]
- Are You a Cognitive Miser? | Cosmic Variance [Last Updated On: November 8th, 2009] [Originally Added On: November 8th, 2009]
- The Secret Lives and Loves of Great White Sharks | 80beats [Last Updated On: November 8th, 2009] [Originally Added On: November 8th, 2009]
- Britain’s New Protected Minority: Tree-Huggers | Discoblog [Last Updated On: November 8th, 2009] [Originally Added On: November 8th, 2009]
- Inspired by Maple Seeds, a Robotic Whirligig Takes To The Skies | Discoblog [Last Updated On: November 8th, 2009] [Originally Added On: November 8th, 2009]
- New Statesman on Accommodationism | The Intersection [Last Updated On: November 8th, 2009] [Originally Added On: November 8th, 2009]
- Laser-Powered Robot Climbs to Victory in the Space-Elevator Contest | 80beats [Last Updated On: November 8th, 2009] [Originally Added On: November 8th, 2009]
- Checking Back In With SEAPLEX | The Intersection [Last Updated On: November 8th, 2009] [Originally Added On: November 8th, 2009]
- Podcast: An Embarrassment of Genomes | The Loom [Last Updated On: November 8th, 2009] [Originally Added On: November 8th, 2009]
- A Baby Neutron Star, Swaddled in a Carbon Atmosphere | 80beats [Last Updated On: November 8th, 2009] [Originally Added On: November 8th, 2009]
- Butterfliiiies… iiinnnn… SPPPAAAAACCCCEEEEE! | Bad Astronomy [Last Updated On: November 8th, 2009] [Originally Added On: November 8th, 2009]
- My Slate Dialogue with Michael Specter Begins | The Intersection [Last Updated On: November 8th, 2009] [Originally Added On: November 8th, 2009]
- Musical, Fahrvergnügen-Inspired Staircase Makes Commuters Less Lazy | Discoblog [Last Updated On: November 8th, 2009] [Originally Added On: November 8th, 2009]
- Laser-Etched Fruit Is an Answer in Search of a Problem | Discoblog [Last Updated On: November 8th, 2009] [Originally Added On: November 8th, 2009]
- Ares and the carnivals | Bad Astronomy [Last Updated On: November 8th, 2009] [Originally Added On: November 8th, 2009]
- Toddler Gets a Telescoping, Prosthetic Arm Bone That Grows With Him | 80beats [Last Updated On: November 8th, 2009] [Originally Added On: November 8th, 2009]
- Neutered HIV Virus Delivers Treatment to Fatally Ill Boys | 80beats [Last Updated On: November 8th, 2009] [Originally Added On: November 8th, 2009]
- Specter’s First Reply: Denialism Kills People | The Intersection [Last Updated On: November 8th, 2009] [Originally Added On: November 8th, 2009]
- LRO sees a Moonslide | Bad Astronomy [Last Updated On: November 8th, 2009] [Originally Added On: November 8th, 2009]
- Al Gore’s New Book: A Focus on Solutions | The Intersection [Last Updated On: November 8th, 2009] [Originally Added On: November 8th, 2009]
- The Universe Has Us in Its Crosshairs | Bad Astronomy [Last Updated On: November 8th, 2009] [Originally Added On: November 8th, 2009]
- Makers of Universes | Cosmic Variance [Last Updated On: November 8th, 2009] [Originally Added On: November 8th, 2009]
- Can Your Pet Catch & Spread Swine Flu? Yes, If Your Pet’s a Ferret | 80beats [Last Updated On: November 8th, 2009] [Originally Added On: November 8th, 2009]
- Droid 2.0 Vs iPhone | The Intersection [Last Updated On: November 8th, 2009] [Originally Added On: November 8th, 2009]
- Tangled Bank News: An Excerpt and More | The Loom [Last Updated On: November 8th, 2009] [Originally Added On: November 8th, 2009]
- LHC Shut Down By Wayward Baguette, Dropped by Bird Saboteur | Discoblog [Last Updated On: November 8th, 2009] [Originally Added On: November 8th, 2009]
- Careidolia | Bad Astronomy [Last Updated On: November 8th, 2009] [Originally Added On: November 8th, 2009]
- Slate Reply to Specter Up–We Need a National Dialogue on Synthetic Biology | The Intersection [Last Updated On: November 8th, 2009] [Originally Added On: November 8th, 2009]
- Pray this doesn’t get passed | Bad Astronomy [Last Updated On: November 8th, 2009] [Originally Added On: November 8th, 2009]
- You Can’t Make This Stuff Up | Cosmic Variance [Last Updated On: November 8th, 2009] [Originally Added On: November 8th, 2009]
- Mother Tongue, Indeed: Newborn’s Cries Mimic Mama’s Accent | 80beats [Last Updated On: November 8th, 2009] [Originally Added On: November 8th, 2009]
- Ripped From the Journals: The Biggest Discoveries of the Week | 80beats [Last Updated On: November 8th, 2009] [Originally Added On: November 8th, 2009]
- Alternative Landscapes | The Loom [Last Updated On: November 8th, 2009] [Originally Added On: November 8th, 2009]
- Can an iPhone App Decipher Your Baby’s Cries? | Discoblog [Last Updated On: November 8th, 2009] [Originally Added On: November 8th, 2009]
- Reminder: Carl Sagan Day | Bad Astronomy [Last Updated On: November 8th, 2009] [Originally Added On: November 8th, 2009]
- Are There Pesticides in Your Soup? Dunk a Pollution Dipstick to Find Out. | 80beats [Last Updated On: November 8th, 2009] [Originally Added On: November 8th, 2009]
- Log in and Join the Conference [Last Updated On: November 8th, 2009] [Originally Added On: November 8th, 2009]
- Conference Ends [Last Updated On: November 8th, 2009] [Originally Added On: November 8th, 2009]
- Conference Archive Opens [Last Updated On: November 8th, 2009] [Originally Added On: November 8th, 2009]
- Galaxy Zoo [Last Updated On: November 8th, 2009] [Originally Added On: November 8th, 2009]
- .Astronomy 2009 Dates [Last Updated On: November 8th, 2009] [Originally Added On: November 8th, 2009]
- .Astronomy 2009: Programme and venue details [Last Updated On: November 8th, 2009] [Originally Added On: November 8th, 2009]
- .Astronomy Gets Some IYA Love [Last Updated On: November 8th, 2009] [Originally Added On: November 8th, 2009]
- 2009 Posters and Imagery [Last Updated On: November 8th, 2009] [Originally Added On: November 8th, 2009]
- 2009 Sponsors [Last Updated On: November 8th, 2009] [Originally Added On: November 8th, 2009]
- When in Holland… [Last Updated On: November 8th, 2009] [Originally Added On: November 8th, 2009]
- The WHAT Cloud? [Last Updated On: November 8th, 2009] [Originally Added On: November 8th, 2009]
- The Jewel Box [Last Updated On: November 8th, 2009] [Originally Added On: November 8th, 2009]
- Happy Halloween! [Last Updated On: November 8th, 2009] [Originally Added On: November 8th, 2009]
- Ares 1-X Launch [Last Updated On: November 8th, 2009] [Originally Added On: November 8th, 2009]
- Confessions of an Alien Hunter [Last Updated On: November 8th, 2009] [Originally Added On: November 8th, 2009]
- LRO Spies Apollo 17 Site [Last Updated On: November 8th, 2009] [Originally Added On: November 8th, 2009]
- Mercury in Color [Last Updated On: November 8th, 2009] [Originally Added On: November 8th, 2009]
- Hubble and M83 [Last Updated On: November 8th, 2009] [Originally Added On: November 8th, 2009]
- Cassini Flyby of Enceladus [Last Updated On: November 8th, 2009] [Originally Added On: November 8th, 2009]
- Preserving A Moth [Science Tattoo] | The Loom [Last Updated On: December 12th, 2009] [Originally Added On: December 12th, 2009]
- Another Russian rocket spiral lights up the sky | Bad Astronomy [Last Updated On: December 12th, 2009] [Originally Added On: December 12th, 2009]
- A (Very Gentle) Riddle to Complete Your Saturday [Last Updated On: December 12th, 2009] [Originally Added On: December 12th, 2009]
- Darwin Gets Swine Flu: The YouTube Edition | The Loom [Last Updated On: December 12th, 2009] [Originally Added On: December 12th, 2009]
- Happy Slothy Holidays | The Loom [Last Updated On: December 12th, 2009] [Originally Added On: December 12th, 2009]
- Jetting to Copenhagen | The Intersection [Last Updated On: December 12th, 2009] [Originally Added On: December 12th, 2009]
- Michael Gerson Attempts Thoughtfulness on “ClimateGate,” Then Gives it Up | The Intersection [Last Updated On: December 13th, 2009] [Originally Added On: December 13th, 2009]
- Incredible VISTA of the cosmos | Bad Astronomy [Last Updated On: December 13th, 2009] [Originally Added On: December 13th, 2009]
- Bundle up Sunday Night to Watch the Geminid Meteor Shower | 80beats [Last Updated On: December 13th, 2009] [Originally Added On: December 13th, 2009]
- “ClimateGate” a PR Disaster That Will Be “Taught in University Communications Courses” | The Intersection [Last Updated On: December 13th, 2009] [Originally Added On: December 13th, 2009]
- Is Google the Guardian Angel of Rainforests? | 80beats [Last Updated On: December 13th, 2009] [Originally Added On: December 13th, 2009]
- La ciencia es importante. Una vez mas. | Bad Astronomy [Last Updated On: December 13th, 2009] [Originally Added On: December 13th, 2009]
- Sensenbrenner Pulls an Inhofe, Asserts Global Warming is an “International Conspiracy” | The Intersection [Last Updated On: December 13th, 2009] [Originally Added On: December 13th, 2009]
- Let Kids Eat Dirt: Over-Cleanliness Linked to Heart Disease | 80beats [Last Updated On: December 13th, 2009] [Originally Added On: December 13th, 2009]
- What Are The Best Science Papers Of The Past Decade? | The Intersection [Last Updated On: December 13th, 2009] [Originally Added On: December 13th, 2009]
- Finally! Math Shows How to Cut Evenly Sized Pizza Slices | Discoblog [Last Updated On: December 13th, 2009] [Originally Added On: December 13th, 2009]
- Half-baked math | Bad Astronomy [Last Updated On: December 13th, 2009] [Originally Added On: December 13th, 2009]
- Can “Biological Passports” Save Sports From Doping? | 80beats [Last Updated On: December 13th, 2009] [Originally Added On: December 13th, 2009]
- Aiiiieeee! Slow down! | Bad Astronomy [Last Updated On: December 13th, 2009] [Originally Added On: December 13th, 2009]
- Weekly News Roundup: Bad Headlines, Martian moons, and Rotating Houses | Discoblog [Last Updated On: December 13th, 2009] [Originally Added On: December 13th, 2009]