JWST takes a look at a rogue planet (?) in the Sun’s back yard

WISE 0855 is the seventh closest object in interstellar space to the Sun

April 29, 2024 Issue #714

Something fun

Remember fun?

I’m pleased to let y’all know that the limited run comic series “Vampires on Mars” — for which I was a science consultant — made its funding goal! That means the books will become a reality, and you’ll get to read the story of a billionaire who will do anything to be the first to the Red Planet… and the science behind it via interviews with me. Yay!

Thanks to everyone who pitched in some cash after my exhortations. I hope you like the result.

Shameless Self-Promotion

Where I’ll be doing things you can watch and listen to or read about

I haven’t gone to any sort of scifi/nerd convention in a long time (before 2020, oddly enough) but I’ve been wanting to get involved with them again. So when my old astronomy and space science friend Laura Burns contacted me asking if I’d be a part of the Savage Geek Fest she was running, I was happy to say yes.

I’ll be the Science Guest of Honor (wow), too! I’ll be giving two talks (“Under Alien Skies”, about my book, and “Strange New Worlds”, about exoplanets) as well as participating in a few panels and such.

The con will be in Savage, Maryland on the weekend of May 4/5 (because of course it has to be on May the Fourth). The con is about STEM (Science, Tech, Engineering, and Math) as well as scifi, gaming, and more, and is hosted by Omnihedral, a gaming store in Savage.

Come check it out, here me talk, and have some geeky fun!

Astro Tidbit

A brief synopsis of some interesting astronomy/science news

JWST is providing a revolution in astronomy, for three basic reasons: 1) it has a huge mirror so it can see faint things, 2) it’s huge mirror means it can resolve fine details in objects, and 3) it’s tuned to the infrared, where we’ve never had a big sensitive telescope see before.

Together these mean it can see distant galaxies better, peer into dusty nebulae with keener vision, and overall just look at objects that are too faint in visible light to see. Like, say — and get this — rogue planets.

One of the nearest objects in space to the Sun is WISE J085510.83−071442.5 (or just WISE 0855 for short), which is so faint it wasn’t even discovered until 2013 despite being only 7.4 light-years from Earth (only three star systems with a total of six objects in them are closer that we know of). 

A black field with several small blobby stars, with a very faint one indicated by a white arrow.

WISE 0855 (arrowed) as seen by the WISE telescope. It’s faint. Credit: ALADIN Lite / Caltech

It’s not clear what to call it. A lot of astronomers call it a brown dwarf — an object more massive than a planet but less than a star — but honestly its mass is probably between 3 – 10 times Jupiter’s mass, which is below the lower limit for a brown dwarf. The IAU defines a planet in part as an object that orbits a star, and WISE 0855 is a loner in space, so in my opinion it’s a rogue planet. It may have formed directly from the collapse of a gas cloud like stars do (or some very low-mass objects seen recently in the Orion Nebula) but it may also have been a giant planet kicked out of its home solar system. We know planets can get ejected by close encounters with other planets, especially when planetary systems are very young, and there may be more rogue planets floating out there in the dark than there are planets orbiting stars!

Whatever we call it, WISE 0855 is the coldest object of its type known, with a cloud-top temperature of something like 260K, or -13°C! Brisk.

Its low temperature means it glows in the far infrared, perfect for JWST to take a peek. Astronomers did just that, and reported their results in The Astronomical Journal. They found their models give a temperature of 285K (+12°C, so sweater weather), but it’s not clear how accurate that is, since their models based on the observations give a smaller diameter for it than other models using more theoretical parameters. Either way, it’s not exactly blazing away like a star is. In fact, if you take the total energy it emits, what we call its luminosity, it glows only one-twenty-millionth as bright as the Sun!

Even that’s misleading; the Sun emits visible light, the kind we see. WISE 0855 is essentially black at those wavelengths, emitting only in infrared. If you on a moon orbiting it, say, it would be a huge black circle in the sky. Just a void, empty. Creepy.

There’s lots of science they could do, including looking for clouds in the data. Objects with clouds — condensed vapor or ice particles floating in the atmosphere — change the way light is emitted, and there were some earlier observations with other infrared telescopes indicating WISE 0855 might be cloudy, perhaps with water ice clouds. However, the JWST show no signs of them (though it’s possible their effects are too small to be easily seen in the observations).

There’s other stuff they found too, but I can’t get over just the idea of observing this object at all. It’s so faint and cold, so un-star-like. It’s not even brown-dwarf-like. 

And it makes me wonder… I used to speculate that there might be a brown dwarf closer to us in space than even the Alpha Centauri system, which is 4.34 light-years from us (Proxima Centauri, a low-mass red dwarf orbiting the brighter pair of Alpha is a bit closer at 4.25). That seems unlikely to me now, since we’ve had infrared surveys turn up nothing.

But WISE 0855 was barely detectable by WISE (the Wide-Field Survey Experiment, a space telescope that swept the sky looking in infrared), so now I wonder if maybe there’s a rogue planet out there, smaller and cooler, that is fainter and escaped our attention. It’s possible, I’d wager. JWST won’t find it, since it looks at a very narrow piece of sky, but future wider-field ‘scopes might have a shot.

And if they find it, well then, that would be literally cool.

Et alia

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