A group of astronomers recently caught sight of one of the largest brown dwarfs known out there. Imagine something between 75 to 90 times the mass of Jupiter and blazing with an insanely hot temperature of 8,000 K (that’s 13,940° Fahrenheit, mind you).
Just for a little comparison, consider that the Sun’s surface heat is a mere 5,772 K (or 9,930° Fahrenheit). These sharp-eyed astronomers spotted this sizzling, super-sized brown dwarf back in 2019 and 2020 using the European Southern Observatory’s Very Large Telescope. They’ve just shared their discoveries in a recent publication in Nature Astronomy.
What is a brown dwarf?
Brown dwarfs are those peculiar objects that sit right in between planets and stars. They’re bigger than gas giants like Jupiter but smaller than small stars. Since they don’t quite hit the mass needed for stars to trigger hydrogen fusion, they’ve sometimes been dubbed “failed stars.”
This recent research bunch, however, took a more polite route, referring to this heavyweight as “WD 0032-317B” – an “irradiated-Jupiter analogue.” This dwarf is in the company of a white dwarf star, stationed a good 1,406 light-years from our humble Earth. These stargazers believe that the brown dwarf and its partner white dwarf were all cosy in a gas envelope up until about a million years ago.
The really cool part is that this dwarf’s got some serious heat. Generally, brown dwarfs are the chilliest and dimmest things on the Hertzsprung-Russell diagram that astronomers use to chart stars’ brightness and effective temperatures.
Stuck in space
This dwarf is kind of stuck in place. It’s what we call tidally locked, so its super-hot side is always facing the white dwarf companion, which, by the way, boasts a toasty surface temp of around 37,000 K (that’s 66,140° Fahrenheit). But don’t think the dwarf’s nightside is missing out – it’s still cooler than its star-facing side, lounging around 2,000 K (which is about 1,727° Fahrenheit).
Now, comparing these brown dwarfs to those sizzling-hot Jupiters, those exoplanets that snuggle up close to their host stars, isn’t a new idea. In fact, in 2021, astronomers found evidence of some pretty familiar features on brown dwarfs – stripes and storms akin to what we see on Jupiter.
Some brown dwarfs can actually be colder than the boiling point of water! The coldest one known even hits a freezing -10° Fahrenheit, which has led some to wonder if it’s more of a rogue exoplanet than a true brown dwarf.
More brown dwarfs discovered of late
Seeing more of these brown dwarfs might just clear up the puzzle of these super hot, supermassive objects. A fresh paper available on the preprint server arXiv has the scoop on a brown dwarf with an amazingly fast orbit of just two hours. Spotted by the Zwicky Transient Facility, this dwarf’s about 80 times the size of Jupiter and boasts an effective temperature of about 1,691 K (or 2,584° Fahrenheit).
And as if that wasn’t enough, last week another group of star enthusiasts showcased a cool GIF of an exoplanet in action. This exoplanet had the spotlight because it’s straddling the line between being a planet and a brown dwarf – at least according to Jason Wang, a sharp mind in the field.
Who knows? Maybe these astronomers will keep using the same trick to study brown dwarfs and really figure out what they’re all about. Or perhaps they’ll turn the watchful eyes of the Webb Space Telescope towards these irradiated-Jupiter lookalikes, just like they’ve done before with even fainter, farther, colder dwarfs than WD 0032-317B.
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