Posted on by Tammy Plotner

WISE Discovers Some Really “Cool” Stars!

[/caption]What would you say if I told you there are stars with a temperature close to that of a human body? Before you have me committed, there really is such a thing. These “cool” stars belong to the brown dwarf family and are termed Y dwarfs. For over ten years astronomers have been hunting for these dark little beasties with no success. Now infrared data from NASA’s Wide-field Infrared Survey Explorer (WISE) has turned up six of them – and they’re less than 40 light years away!

“WISE scanned the entire sky for these and other objects, and was able to spot their feeble light with its highly sensitive infrared vision,” said Jon Morse, Astrophysics Division director at NASA Headquarters in Washington. “They are 5,000 times brighter at the longer infrared wavelengths WISE observed from space than those observable from the ground.”

Often referred to as “failed stars”, the Y-class suns are simply too low mass to ignite the fusion process which makes other stars shine in visible light. As they age, they fade away – their only signature is what can be spotted in infrared. The brown dwarfs are of great interest to astronomers because we can gain a better understanding as to stellar natures and how planetary atmospheres form and evolve. Because they are alone in space, it’s much easier to study these Jupiter-like suns… without being blinded by a parent star.

“Brown dwarfs are like planets in some ways, but they are in isolation,” said astronomer Daniel Stern, co-author of the Spitzer paper at JPL. “This makes them exciting for astronomers — they are the perfect laboratories to study bodies with planetary masses.”

The WISE mission has been extremely productive – turning up more than 100 brown dwarf candidates. Scientists are hopeful that even more will emerge as huge amounts of data are processed from the most advanced survey of the sky at infrared wavelengths to date. Just imagine how much information was gathered from January 2010 to February 2011 as the telescope scanned the entire sky about 1.5 times! One of the Y dwarfs, called WISE 1828+2650, is the record holder for the coldest brown dwarf, with an estimated atmospheric temperature cooler than room temperature, or less than about 80 degrees Fahrenheit (25 degrees Celsius).

“The brown dwarfs we were turning up before this discovery were more like the temperature of your oven,” said Davy Kirkpatrick, a WISE science team member at the Infrared Processing and Analysis Center at the California Institute of Technology in Pasadena, Calif. “With the discovery of Y dwarfs, we’ve moved out of the kitchen and into the cooler parts of the house.”

Kirkpatrick is the lead author of a paper appearing in the Astrophysical Journal Supplement Series, describing the 100 confirmed brown dwarfs. Michael Cushing, a WISE team member at NASA’s Jet Propulsion Laboratory in Pasadena, California, is lead author of a paper describing the Y dwarfs in the Astrophysical Journal.

“Finding brown dwarfs near our Sun is like discovering there’s a hidden house on your block that you didn’t know about,” Cushing said. “It’s thrilling to me to know we’ve got neighbors out there yet to be discovered. With WISE, we may even find a brown dwarf closer to us than our closest known star.”

Given the nature of the Y-class stars, positively identifying these special brown dwarfs wasn’t an easy task. For that, the WISE team employed the aid of the Spitzer Space Telescope to refine the hunt. From there the team used the most powerful telescopes on Earth – NASA Infrared Telescope Facility atop Mauna Kea, Hawaii; Caltech’s Palomar Observatory near San Diego; the W.M. Keck Observatory atop Mauna Kea, Hawaii; and the Magellan Telescopes at Las Campanas Observatory, Chile, and others – to look for signs of methane, water and even ammonia. For the very coldest of the new Y dwarfs, the team used NASA’s Hubble Space Telescope. Their final answer came when changes in spectra indicated a low temperature atmosphere – and a Y-class signature.

“WISE is looking everywhere, so the coolest brown dwarfs are going to pop up all around us,” said Peter Eisenhardt, the WISE project scientist at NASA’s Jet Propulsion Laboratory, Pasadena, California, and lead author of a recent paper in the Astronomical Journal on the Spitzer discoveries. “We might even find a cool brown dwarf that is closer to us than Proxima Centauri, the closest known star.”

How cool is that?!

Original Story Source: JPL News Release.

16 Replies to “WISE Discovers Some Really “Cool” Stars!”

  2. “Finding brown dwarfs near our Sun is like discovering there’s a hidden house on your block that you didn’t know about,” Cushing said. “It’s thrilling to me to know we’ve got neighbors out there yet to be discovered. With WISE, we may even find a brown dwarf closer to us than our closest known star.”

    There goes the neighborhood!

  4. What are the mass ranges to be still called a brown dwarf?

    Also what compositions can such a dwarf have?
    Could we still detect such brown dwarfs if it was lit by a nearby star in a double star system visually just like Jupiter is reflecting light?

    1. To answer that I think astronomers have to sort out the birth processes and/or compositions of both stars and planets. If brown dwarfs are the runts of stars, they would be collapse objects of gas clouds.

      But there are hypotheses that giant planets can be born in a similar way. They may, or may not, have solid cores. Would we know which is which in all cases? Should we care about differences?

      So when we see a star + brown dwarf or a brown dwarf + brown dwarf system, how do we distinguish that from a star + giant planet or a brown dwarf + giant planet system?

      If we can’t separate out these populations, I am not sure these questions have a ready answer. But I am no astronomer, so I don’t know the status here.

      1. I think composition would be sufficient. A key distinction is that brown dwarfs have fully convective interiors as opposed to differentiated interiors of the largest gas giants.

        This distinction is driven by mass regardless of whether the dwarf originally formed via core accretion, disk instability or the collapse of a molecular cloud.

      2. I think composition would be sufficient. A key distinction is that brown dwarfs have fully convective interiors as opposed to differentiated interiors of the largest gas giants.

        This distinction is driven by mass regardless of whether the dwarf originally formed via core accretion, disk instability or the collapse of a molecular cloud.

      3. So you could have a brown dwarf with any colour of the rainbow because of its composition. Blue like Uranus, brown like Jupiter and yellow like Saturn, depending on the composition.

        It is only called brown because it emits not much light but could reflect the sunlight of a nearby star and get very bright and blue.

        Would it have bands like Jupiter? Or would the convection generate an even distribution of the materials?

      4. Question. At what distance could WISE find a 25 Jupiter mass planet? I’m thinking there may be more of these type objects in interstellar space than there are red or brown dwarf stars.

      5. It seems like the convection would work against atmospheric effects like that. It probably depends more on the temperature of the planet in the outer layers more than anything else. If it was cool enough so that radiative pressure was sufficient, then we would expect atmospheric effects.

  5. i cant help but immediately be drawn to the thought that life could be possible within the atmospheres of such bodies, especially at these temperatures – but hotter brown dwarfs intrigue me greatly as well, due to to prospect of close in orbiting terrestrial planets which may harbor an atmosphere. this is really interesting stuff

  6. Did WISE also CONFIRM the Y dwarf candidate orbiting a white dwarf that showed up a few months ago? That’s the one whose temperature is supposedly only a few degrees warmer than WISE 1828-2650’s I think the distance of this previous discovery is a little further than 40 light years, so WISE may not be sensitive enough to pick that one up

  7. Yeah, I wonder if some type of organism could live in the atmospheres of these. Liquid water could be present in clouds, so it may be possible that some type of microorganism could develop.

    I wonder what would happen if two 10-jupiter-mass planets merged. Would a brown dwarf be the result? What if they both had rocky/metallic cores? Is a brown dwarf really just an extremely massive gas giant planet? These are questions that I hope can be answered with new data and theory revisions.

  8. What is the approximate mass of WISE 1828+2650 ? I knows its alone in space but is it just larger than Jupiter or just smaller than the sun?

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