Two new nearby brown dwarfs found

By Phil Plait | August 9, 2011 7:00 am

Astronomers recently discovered two brown dwarfs in our solar neighborhood, and they’re actually pretty close by: 15 and 18 light years away!

[Click to hugely unendwarfenate.]

The two objects were spotted in observations made by WISE, the Wide-field Infrared Survey Explorer, which recently finished its mission to observe the entire sky in infrared light. In the false color images from WISE, brown dwarfs tend to appear very green (fun details are in that link), making them somewhat easy to spot against full-blown stars which tend to appear blue — remember, this is false color!

Anyway, the astronomers were looking for nearby brown dwarfs (PDF), so they searched for green objects that had no obvious counterparts in older infrared surveys. All stars orbit the center of the Milky Way galaxy at different velocities, and over time that means they move across the sky. Nearby stars appear to move fastest (just like the nearby trees fly past you while driving, but distant mountains appear to move more slowly), so nearby brown dwarfs would have moved in the time separating the older surveys from that of WISE.

The astronomers actually found quite a few objects, most of which were known. But these two, called WISE J0254+0223 and WISE J1741+2553, were not previously known — in the picture above, their positions in the older survey from 2000 are labeled compared to their positions in the 2010 WISE images. Remarkably, only 39 star systems (I include multiple stars as one system here) are known to be closer to us than J1741 (which is 15 light years away), and only a handful of them are brown dwarfs (what are called T class objects).

Which, as always when we find new nearby stars, make me wonder: are there faint, cool brown dwarfs even closer to us? Is it possible that Proxima Centauri, a red dwarf 4.2 light years away, is not the closest star to the Sun?

Maybe. The WISE data used to find these two neighbors is not the full set taken by the spacecraft. There’s still quite a bit of data to sift through. Who knows, we may yet find out there’s a star or stars passing by still waiting to make our acquaintance.


Related posts:

WISE finds the coolest stars. Literally.
The galaxy may swarm with billions of wandering planets
Are we in danger from a rogue planet?
The case of the brown star that’s really red or possibly blue

MORE ABOUT: brown dwarfs, WISE

Comments (22)

  1. James

    Very interesting stuff. But it is sad that as soon as I saw this, I instantly thought “oh no, here come the Niburu crowd”. More “evidence” for those who aren’t able to explain what a light year is, or don’t believe scientists when they say it. I am so tired of these doom sayers, when will it all end? (pun intended)

  2. Which, as always when we find new nearby stars, make me wonder: are there faint, cool brown dwarfs even closer to us? Is it possible that Proxima Centauri, a red dwarf 4.2 light years away, is not the closest star to the Sun?

    It seems that for this purpose you are defining brown dwarfs as stars. Is this standard? My impression was that brown dwarfs were not normally included as stars because of the lack of fusion.

  3. Craig

    The next question I have is: what is the possibility that there are planets capable of supporting life around these stars? I realize one of the questions will be, did they form from supernova matter? If so, and these could have rocky planets in a habitable zone, then it would make life on them more likely.

  4. Owen

    Are brown dwarfs officially considered stars? I thought they were considered sub-stellar since they don’t have sustained fusion.

  5. Doug Little

    What Owen said.

  6. Messier Tidy Upper

    @ ^ & (#3) Owen : Brown dwarfs are sort of intermediate between stars and planets in many ways, as I understand it.

    Brown dwarfs cannot fuse hydrogen into helium but they can fuse deuterium for a brief time – exactly how long depending on the exact mass of the brown dwarf in question.

    There is also the matter of how brown dwarfs form – although this is, I think a lot muddier and less clear.

    If I understand right and am not mistaken, then Brown Dwarfs supposedly form like stars – from a Bok globule or star-forming cloud of gas and dust – rather than like planets – which form from protoplanetary disks around stars as a secondary product.

    However, there may be overlapping cases where brown dwarfs are the result of superjovian planets growing sufficently large to reach brown dwaf mass and status and also of star forming clouds (Bok globules) that are so lacking in mass or get so disturbed by neighbouring stars and other events that they only form (exo)planets directly rather than having enough mass to form even brown dwarf mass objects.

    ****

    Awesome news! Congrats to the WISE guys! :-)

    (Raises a beer or two to them and their new found, new neighbour brown dwarfs! :-) )

  7. Messier Tidy Upper

    For those who are curious to know more, here’s the wikipedia page :

    http://en.wikipedia.org/wiki/Brown_dwarfs

    plus this :

    http://stars.astro.illinois.edu/sow/star_intro.html#brown

    Via Jim Kaler’s marvellous Stars website plus see :

    http://stars.astro.illinois.edu/sow/epsind.html

    Kaler’s page for Epsilon Indi which is one of our nearest neighbours consisting of three stars – an orange dwarf and two tightly bound brown dwarfs. These binary brown dwarfs are the very nearest known examples or so I gather.

  8. Messier Tidy Upper

    See also :

    http://jumk.de/astronomie/near-stars/scr-1845-6357.shtml

    for info on the third closest known Brown Dwarf after those linked for Epsilon Indi) the companion to a dim nearby red dwarf SCR 1845-6357 loctaed just 12.7 ly away with the brown dwarf orbiting about 5 AU or Jupiters’s distance away.

    Oddly enough, these thee nearest brown dwarfs are all companions to other stars rather than individual ones.

    See too :

    http://blogs.discovermagazine.com/badastronomy/2008/06/02/welcome-our-tiny-family/

    via the BA blog a few years ago & :

    http://blogs.discovermagazine.com/badastronomy/2008/06/02/astronomers-weigh-in-on-teeny-stars/

    likewise. Hope these are interesting / useful / enjoyable for y’all. :-)

  9. Ray

    If they can control the colors, why are brown dwarfs represented as green blobs?

  10. Keith Bowden

    Dwarf stars are stars and dwarf planets are planets and dwarf people are people. (That might be considered a little un-PC, but I’m going for silly here to make the point.) :)

  11. jcj4972

    Even though brown dwarfs do not have sufficient mass to fuse atoms like in a star from what I understand they do radiate both heat and light. I’ve always wondered if there is a goldilocks zone around these objects. If a small planet or moon was close enough to a brown dwarf would it receive sufficient heat and light to possibly harbor life. If this somehow proved to be the case it would open a lot of other possibilities in the search for life…. I love astronomy!

  12. JGB

    Phil what do you suppose the maximum distance would be, if we were to find a star closer than Alpha Centauri that would allows us to design a mission to visit robotically in the near term (say 5-20 years)?

  13. Which, as always when we find new nearby stars, make me wonder: are there faint, cool brown dwarfs even closer to us? Is it possible that Proxima Centauri, a red dwarf 4.2 light years away, is not the closest star to the Sun?

    Shortly after WISE had been launched back in June 2009 I posted a poll asking that very question on the BAUT forum – click on my name to see via linkage.

    I asked there & percentage~wise got :

    ***

    1. WISE will find more than one brown dwarf or star closer than Proxima = 47.37%

    2. WISE will discover a brown dwarf closer to us than Proxima Centauri = 36.84%

    3. No, Proxima Centauri will keep its record & we won’t find anything nearer = 31.58%

    4. WISE will find an iceberg cold or colder brown dwarf closer than Proxima = 15.79%

    5. WISE will discover a red dwarf closer to us than Proxima Centauri = 5.26%

    ***

    Looks like the verdict is still uncertain years later which I must admit I hadn’t imagined would happen at all!

    Really looking forward to them finishing going through all the WISE data so we can say for sure one way or the other! :-)

  14. @11. jcj4972 :

    Even though brown dwarfs do not have sufficient mass to fuse atoms like in a star from what I understand they do radiate both heat and light. I’ve always wondered if there is a goldilocks zone around these objects. If a small planet or moon was close enough to a brown dwarf would it receive sufficient heat and light to possibly harbor life. If this somehow proved to be the case it would open a lot of other possibilities in the search for life…. I love astronomy!

    Me too! ;-)

    Sadly, I think that a brown dwarf having a habitable planet is probably really stretching plausibilities given how very small and close in that limited space will be.

    Someone who knows and is good at maths can no doubt calculate it but it may be that the habitable zone of a brown dwarf is actually inside the Roche limit where no planet or moon but only rings can exist. (click on my name for the wiki-basics of the Roche limit.)

    Mind you, I could be mistaken and if there is more than just the one star in the system – say a brown dwarf orbiting another brighter star, who knows? A brown dwarf may not make for a habitable planet on its own but in combination – perhaps?

  15. Messier Tidy Upper

    PS. Also they used to rule red dwarfs out as possible suns capable of hosting habitable exoplanets yet as this article :

    http://kencroswell.com/reddwarflife.html

    by Ken Croswell observes that’s no longer the case for them. So perhaps some similiar rethinking regarding brown dwarfs isn’t beyond the realm of the concievable.

    Croswell has also written interestingly on brown dwarfs here :

    http://kencroswell.com/100BillionBrownDwarfs.html

    & here :

    http://kencroswell.com/BrownDwarfLithium.html

    too which are perhaps worth reading in this context /thread.

  16. DigitalAxis

    @4 Owen and 6 Messier Tidier Upper:

    There are two different definitions for brown dwarfs: One defines a brown dwarf as an object that forms like a star but lacks the mass to sustain hydrogen fusion (but IS capable of limited hydrogen and deuterium fusion- it’s just that fusion never produces enough pressure to balance out gravitational contraction) The other definition basically leaves out the “forms like a star” part. Then there are other theories that say brown dwarfs form like brown dwarfs, and there’s some third mechanism…

    Theorists prefer the first definition; many observationalists prefer to ignore how it formed and just figure out what it is. I once went to a WISE talk about a brown dwarf with spectral class colder than T10, which they believed might be 5 Jupiter Masses. That sounds like a free-floating planet, but by their theoretical definition it’s a brown dwarf because it’s not orbiting a star and may have formed on its own, and they don’t actually KNOW its mass anyway. (In the talk, the WISE people said they preferred the term “object”).

    Ultimately, the problem is that all we know is the temperature, rotation, composition, and surface gravity of an object, which gives us very limited information about what’s going on at the core. Some of WISE’s brown dwarfs may actually be feeble stars, some of WISE’s red dwarfs may actually be massive brown dwarfs. We can speculate based on models of their interior physics, but there’s currently no known way of determining for certain if an object with a ~2000-degree upper atmosphere is a brown dwarf or a star.

    EDIT: Actually, the way to determine it would be to luck upon a relatively old nearly-equal-mass binary system where one of the objects was genuinely a lot cooler and dimmer than the other one (no dust obscuration). In that case, we could get the masses of the (bright) star and (dim) brown dwarf and figure out where the mass limit was, for that particular composition, magnetic activity, and rotational velocity.

  17. I remember that the first Brown Dwarfs discovered were companions to larger stars.

    Are these two new brown dwarfs actually *solitary* brown dwarfs, not part of a larger star system? Or are they merely orbiting the blue thingies shown in the pictures?

  18. Messier Tidy Upper

    @ ^ tracer : From reading the press release (first link above here) & after a quick scan through the PDF paper on their discovery from there, it seems these are both solitary objects with no mention of them orbiting any other stars.

    So I take it they are, indeed, solitary borwn dwarfs each wanderuing the cosmos on its own. Of course, they may or may not boast exoplanets and cometary clouds or asteroid belts – so much still remains to be discovered and hopefully follow up studies will be done.

    Which is somewhat unusual – given many of the nearby brown dwarfs do indeed appear to be companions tolarger stars – but isn’t unprecedented as othersolitary brown dwarfs are known.

  19. Messier Tidy Upper

    See :

    http://arxiv.org/PS_cache/arxiv/pdf/1105/1105.4059v2.pdf

    via :

    http://arxiv.org/abs/1105.4059

    via that first link posted in the Opening Post / article here.

    This interesting clip :

    http://www.space.com/9848-closest-star-wise-brown-dwarfs.html

    via space-dot-com is somewhat more “plain english” and less technical but also now rather less up to date. Alas my preliminary search couldn’t find any news items there on this latest brown dwarf duo discovery.

  20. Bill Loehr

    “unendwarfenate” – love it!

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