Astronomers find evidence of water clouds in first spectrum of coldest brown dwarf

Astronomers find evidence of water clouds in first spectrum of coldest brown dwarf
ARtist's rendering of WISE 0855 as it might appear if viewed up close in infrared light. Credit: Credit: Joy Pollard, Gemini Observatory/AURA

Since its detection in 2014, the brown dwarf known as WISE 0855 has fascinated astronomers. Only 7.2 light-years from Earth, it is the coldest known object outside of our solar system and is just barely visible at infrared wavelengths with the largest ground-based telescopes.

Now, a team led by astronomers at UC Santa Cruz has succeeded in obtaining an infrared of WISE 0855 using the Gemini North telescope in Hawaii, providing the first details of the object's composition and chemistry. Among the findings is strong evidence for the existence of clouds of water or water ice, the first such clouds detected outside of our solar system.

"We would expect an object that cold to have water clouds, and this is the best evidence that it does," said Andrew Skemer, assistant professor of astronomy and astrophysics at UC Santa Cruz. Skemer is first author of a paper on the new findings to be published in Astrophysical Journal Letters and currently available online.

A brown dwarf is essentially a failed star, having formed the way stars do through the gravitational collapse of a cloud of gas and dust, but without gaining enough mass to spark the that make stars shine. With about five times the mass of Jupiter, WISE 0855 resembles that in many respects. Its temperature is about 250 degrees Kelvin, or minus 10 degrees Fahrenheit, making it nearly as cold as Jupiter, which is 130 degrees Kelvin.

"WISE 0855 is our first opportunity to study an extrasolar planetary-mass object that is nearly as cold as our own gas giants," Skemer said.

Previous observations of the brown dwarf, published in 2014, provided tentative indications of water clouds based on very limited photometric data. Skemer, a coauthor of the earlier paper, said obtaining a spectrum (which separates the light from an object into its component wavelengths) is the only way to detect an object's molecular composition.

WISE 0855 is too faint for conventional spectroscopy at optical or near-infrared wavelengths, but thermal emission from the deep atmosphere at wavelengths in a narrow window around 5 microns offered an opportunity where spectroscopy would be "challenging but not impossible," he said.

The team used the Gemini-North telescope in Hawaii and the Gemini Near Infrared Spectrograph to observe WISE 0855 over 13 nights for a total of about 14 hours.

"It's five times fainter than any other object detected with ground-based spectroscopy at this wavelength," Skemer said. "Now that we have a spectrum, we can really start thinking about what's going on in this object. Our spectrum shows that WISE 0855 is dominated by and clouds, with an overall appearance that is strikingly similar to Jupiter."

The researchers developed atmospheric models of the equilibrium chemistry for a brown dwarf at 250 degrees Kelvin and calculated the resulting spectra under different assumptions, including cloudy and cloud-free models. The models predicted a spectrum dominated by features resulting from water vapor, and the cloudy model yielded the best fit to the features in the spectrum of WISE 0855.

Comparing the brown dwarf to Jupiter, the team found that their spectra are strikingly similar with respect to water absorption features. One significant difference is the abundance of phosphine in Jupiter's atmosphere. Phosphine forms in the hot interior of the planet and reacts to form other compounds in the cooler outer atmosphere, so its appearance in the spectrum is evidence of turbulent mixing in Jupiter's atmosphere. The absence of a strong phosphine signal in the spectrum of WISE 0855 implies that it has a less turbulent atmosphere.

"The spectrum allows us to investigate dynamical and chemical properties that have long been studied in Jupiter's atmosphere, but this time on an extrasolar world," Skemer said.


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Astronomers find evidence of water clouds in brown dwarf atmosphere

More information: "The First Spectrum of the Coldest Brown Dwarf," Andrew Skemer et al., 2016, Astrophysical Journal Letters, On Arxiv: arxiv.org/abs/1605.04902
Journal information: Astrophysical Journal Letters

Citation: Astronomers find evidence of water clouds in first spectrum of coldest brown dwarf (2016, July 6) retrieved 18 September 2019 from https://phys.org/news/2016-07-astronomers-evidence-clouds-spectrum-coldest.html
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Jul 06, 2016
This comment has been removed by a moderator.

Jul 06, 2016
waitaminit...
Average temp; -10F
Water freeze temp; 32F
Water vapor?!?

Jul 06, 2016
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Jul 06, 2016
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Jul 07, 2016
So, one guess would be, is an impurity lowering the freezing point? The observation has precedent. See: Faherty, Jacqueline K.; Tinney, C. G.; Skemer, Andrew; Monson, Andrew J. (August 2014). "Indications of Water Clouds in the Coldest Known Brown Dwarf". Astrophysical Journal Letters

Would be the only explanation... They should have been able to identify an impurity, tho...


Jul 07, 2016
If we leave out the definitions, WISE 0855 is fully in line with expectations (WD). Jupiter has a molten core (along, + tidal forces of the Sun), it is normal and for the larger body.
The existence of water vapor is not tied for average temperature, already geological activity (volcanoes) as a result of which leads to the evaporation.

As I wrote earlier, brown dwarfs with independent rotation have the highest probability for the existence of life.

Jul 07, 2016
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Jul 07, 2016
It is based within WD theory. Continuous increase in bodies and processes.

http://www.svemir...tml#Life part of "The Wrong Ideas About Life Creating Zones" ... "Since the Universe is vast, they are unable to keep seeing it as dynamic, constantly changing, with permanent processes that do not correlate the existence of life neither it nor zones to areas.
The objects keep growing all the time (they get bigger). When .. "
and
http://www.space....s=og.com

Jul 07, 2016
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Jul 07, 2016
Average temp; -10F
Water freeze temp; 32F
Water vapor?!?

Water freezes at one atmosphere pressure at 0°C. At different pressures you get different freezing points
http://cft.fis.uc...gram.jpg

The topmost layers (which is mostly where you get information from when you take spectrometric data) is not very dense. ...well...you can get arbitrarily low pressure the higher you get up in the atmosphere of this (failed) star.

Jul 08, 2016
@Chris_Reeve
Towards all criteria Earth is among the dwarves.
Molten core, average temperatures are above the Y dwarfs, dynamic geological processes and of course independent rotation that determines the type of atmosphere. Equally life no obstacle appear to dwarf who is he the central body (is independent). The existence of light due to the impact of radiation into the atmosphere (matter) is not a condition for the emergence of life (that we see here on Earth).

Jul 08, 2016
L-type brown dwarfs are possibly ideal incubators for life if the planet was to orbit within the stars tenuous illuminated envelope. In such a scenario, those planets would have water rain fall down upon the planet's surface, and the planet's entire surface would have a steady light which coincides with the frequencies that plants appear to prefer.

I've read the atmospheres of these stars may too be rich with life supporting materials which paired with the water raining down would equate to a sort of "manna from heaven". These conditions basically describes Eden. Hmmmm....

Jul 13, 2016
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Jul 13, 2016
And there you have the quality of thinking that leads to thinking EU is science. There really needs to be a category for it in the DSM.
There is.

http://dsm.psychi...96.dsm02

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