Advertisement

Y Dwarfs: The Challenge of Discovering the Coldest Substellar Population in the Solar Neighborhood

  • Sandy K. LeggettEmail author
Reference work entry

Abstract

Stars form in the Galaxy with a wide range in mass. If the mass is below 7% of the Sun’s, then the object does not become hot enough for stable hydrogen burning. These substellar objects are called brown dwarfs. Maps of the sky at infrared wavelengths have found large numbers of brown dwarfs. However only 24 objects have been found (as of April 2017) that are cold enough to be classified as “Y dwarfs”: these have atmospheres that are cooler than 500 K (or ∼200C, 400F) and have masses only 5–20 times that of Jupiter. The coolest Y dwarf currently known, discovered in 2014, has a temperature around freezing, has a mass of about 5 Jupiter masses, and is only 2 pc away from the Sun. These small and cold objects are faint and difficult to find. This chapter describes the discovery and characterization of the Y dwarfs. Finding more of these very cold planet-like brown dwarfs will require an as-yet unplanned space mission mapping large areas of sky at wavelengths around 5 μm.

References

  1. Ackerman AS, Marley MS (2001) Precipitating condensation clouds in substellar atmospheres. ApJ 556:872ADSCrossRefGoogle Scholar
  2. Baraffe I, Chabrier G, Allard F, Hauschildt PH (2002) Evolutionary models for low-mass stars and brown dwarfs: uncertainties and limits at very young ages. A&A 382:563ADSCrossRefGoogle Scholar
  3. Beamin JC, Ivanov VD, Bayo A et al (2014) Temperature constraints on the coldest brown dwarf known: WISE 0855-0714. A&A 570:L8ADSCrossRefGoogle Scholar
  4. Bowler BP, Hillenbrand LA (2015) Near-infrared spectroscopy of 2M0441+2301 AabBab: a quadruple system spanning the stellar to planetary mass regimes. ApJ 811:L30ADSCrossRefGoogle Scholar
  5. Burgasser AJ, Kirkpatrick JD, Brown ME et al (1999) Discovery of four field methane (T-type) dwarfs with the two micron all-sky survey. ApJ 522:L65ADSCrossRefGoogle Scholar
  6. Burrows A, Marley MS, Hubbard WB et al (1997) A nongray theory of extrasolar giant planets and brown dwarfs. ApJ 491:856ADSCrossRefGoogle Scholar
  7. Burrows A, Hubbard WB, Lunine JI, Liebert J (2001) The theory of brown dwarfs and extrasolar giant planets. RvMP 73:719ADSGoogle Scholar
  8. Burrows A, Sudarsky D, Lunine JI (2003) Beyond the T dwarfs: theoretical spectra, colors, and detectability of the coolest brown dwarfs. ApJ 596:587ADSCrossRefGoogle Scholar
  9. Cannon AJ, Pickering EC (1912) Classification of 1,477 stars by means of their photographic spectra. AnHar 56:65ADSGoogle Scholar
  10. Chabrier G (2003) Galactic stellar and substellar initial mass function. PASP 115:763ADSCrossRefGoogle Scholar
  11. Cushing MC, Kirkpatrick JD, Gelino CR et al (2011) The discovery of Y dwarfs using data from the wide-field infrared survey explorer (WISE). ApJ 743:50ADSCrossRefGoogle Scholar
  12. Cushing MC, Hardegree-Ullman KK, Trucks JL et al (2016) The first detection of photometric variability in a Y dwarf: WISE J140518.39+553421.3. ApJ 823:152ADSCrossRefGoogle Scholar
  13. Fazio GG, Hora JL, Allen LE et al (2004) The infrared array camera (IRAC) for the spitzer space telescope. ApJS 154:10ADSCrossRefGoogle Scholar
  14. Gehrels N, Spergel D, WFIRST SDT Project (2015) Wide-field infraRed survey telescope (WFIRST) mission and synergies with LISA and LIGO-virgo. J Phys Conf Ser 610:2007Google Scholar
  15. Greenhouse MA (2016) The JWST science instrument payload: mission context and status. SPIE 9904:6ADSGoogle Scholar
  16. Hayashi C, Nakano T (1963) Evolution of stars of small masses in the pre-main-sequence stages. Prog Theor Phys 30:460ADSCrossRefGoogle Scholar
  17. Kirkpatrick JD, Reid IN, Liebert J et al (1999) Dwarfs cooler than “M”: the definition of spectral type “L” using discoveries from the 2 micron all-sky survey (2MASS). ApJ 519:802ADSCrossRefGoogle Scholar
  18. Kirkpatrick JD, Gelino CR, Cushing MC et al (2012) Further defining spectral type “Y” and exploring the low-mass end of the field brown dwarf mass function. ApJ 753:156ADSCrossRefGoogle Scholar
  19. Kroupa P (2001) On the variation of the initial mass function. MNRAS 322:231ADSCrossRefGoogle Scholar
  20. Kumar SS (1967) On planets and black dwarfs. Icarus 6:136ADSCrossRefGoogle Scholar
  21. Leggett SK, Golimowski DA, Fan X et al (2002) Infrared photometry of late-M, L, and T dwarfs. ApJ 564:452ADSCrossRefGoogle Scholar
  22. Leggett SK, Morley CV, Marley et al (2013) A comparison of near-infrared photometry and spectra for Y dwarfs with a new generation of cool cloudy models. ApJ 763:130ADSCrossRefGoogle Scholar
  23. Leggett SK, Morley CV, Marley MS, Saumon D (2015) Near-infrared photometry of Y dwarfs: low ammonia abundance and the onset of water clouds. ApJ 799:37ADSCrossRefGoogle Scholar
  24. Leggett SK, Cushing MC, Hardegree-Ullman KK et al (2016) Observed variability at 1 and 4 μm in the Y0 brown dwarf WISEP J173835.52+273258.9. ApJ 830:141ADSCrossRefGoogle Scholar
  25. Leggett SK, Tremblin P, Esplin TL, Luhman KL, Morley CV (2017) The Y-type brown dwarfs: estimates of mass and age from new astrometry, homogenized photometry, and near-infrared spectroscopy. ApJ 842:118ADSCrossRefGoogle Scholar
  26. Li Y, Kouwenhoven MBN, Stamatellos D, Goodwin SP (2015) The dynamical evolution of low-mass hydrogen-burning stars, brown dwarfs, and planetary-mass objects formed through disk fragmentation. ApJ 805:116ADSCrossRefGoogle Scholar
  27. Lord SD (1992) A new software tool for computing Earth’s atmospheric transmission of near- and far-infrared radiation. NASA Tech Memo 103957Google Scholar
  28. Luhman KL (2014) Discovery of a ∼250 K brown dwarf at 2 pc from the sun. ApJ 786:L18ADSCrossRefGoogle Scholar
  29. Mainzer A, Cushing MC, Skrutskie M et al (2011) The first ultra-cool brown dwarf discovered by the wide-field infrared survey explorer. ApJ 726:30ADSCrossRefGoogle Scholar
  30. Masiero JR, Mainzer AK, Bauer JM, Grav T, Nugent CR, Stevenson R (2013) Asteroid family identification using the hierarchical clustering method and WISE/NEOWISE physical properties. ApJ 770:7ADSCrossRefGoogle Scholar
  31. Miller GE, Scalo JM (1979) The initial mass function and stellar birthrate in the solar neighborhood. ApJS 41:513ADSCrossRefGoogle Scholar
  32. Morgan WW, Keenan PC (1973) Spectral classification. ARA&A 11:29ADSCrossRefGoogle Scholar
  33. Morley CV, Fortney JJ, Marley MS et al (2012) Neglected clouds in T and Y dwarf atmospheres. ApJ 756:172ADSCrossRefGoogle Scholar
  34. Morley CV, Marley MS, Fortney JJ et al (2014) Water clouds in Y dwarfs and exoplanets. ApJ 787:78ADSCrossRefGoogle Scholar
  35. Racca GD, Laureijs R, Stagnaro L et al (2016) The Euclid mission design. SPIE 9904:23 pp.  https://doi.org/10.1117/12.2230762
  36. Salpeter EE (1955) The luminosity function and stellar evolution. ApJ 121:161ADSCrossRefGoogle Scholar
  37. Saumon D, Geballe TR, Leggett SK et al (2000) Molecular abundances in the atmosphere of the T dwarf GL 229B. ApJ 541:374ADSCrossRefGoogle Scholar
  38. Saumon D, Marley MS (2008) The evolution of L and T dwarfs in color-magnitude diagrams. ApJ 689:1327ADSCrossRefGoogle Scholar
  39. Saumon D, Marley MS, Abel M, Frommhold L, Freedman RS (2012) New H2 collision-induced absorption and NH3 opacity and the spectra of the coolest brown dwarfs. ApJ 750:74ADSCrossRefGoogle Scholar
  40. Schneider AC, Cushing MC, Kirkpatrick DJ, Gelino CR (2016) The collapse of the wien tail in the coldest brown dwarf? Hubble space telescope near-infrared photometry of WISE J085510.83-071442.5. ApJ 823:35ADSCrossRefGoogle Scholar
  41. Showman A, Kaspi Y (2013) Atmospheric dynamics of brown dwarfs and directly imaged giant planets. ApJ 776:85ADSCrossRefGoogle Scholar
  42. Spiegel DS, Burrows A (2012) Spectral and photometric diagnostics of giant planet formation scenarios. ApJ 745:174ADSCrossRefGoogle Scholar
  43. Stern D, Assef RJ, Benford DJ et al (2012) Mid-infrared selection of active galactic nuclei with the wide-field infrared survey explorer. I. Characterizing WISE-selected active galactic nuclei in COSMOS. ApJ 753:30ADSCrossRefGoogle Scholar
  44. Strauss MA, Fan X, Gunn JE et al (1999) The discovery of a field methane dwarf from sloan digital sky survey commissioning data. ApJ 522:L61ADSCrossRefGoogle Scholar
  45. Tremblin P, Amundsen DS, Mourier P et al (2015) Fingering convection and cloudless models for cool brown dwarf atmospheres. ApJ 804:L17 (T15)ADSCrossRefGoogle Scholar
  46. Tsuji T, Ohnaka K, Aoki W, Nakajima T (1996) Evolution of dusty photospheres through red to brown dwarfs: how dust forms in very low mass objects. A&A 308:L29ADSGoogle Scholar
  47. Warren SJ, Mortlock DJ, Leggett SK et al (2007) A very cool brown dwarf in UKIDSS DR1. MNRAS 381:1400ADSCrossRefGoogle Scholar
  48. Wright EL, Eisenhardt PRM, Mainzer AK et al (2010) The wide-field infrared survey explorer (WISE): mission description and initial on-orbit performance. AJ 140:1868ADSCrossRefGoogle Scholar
  49. Yurchenko SN, Barber RJ, Tennyson J (2011) A variationally computed line list for hot NH3. MNRAS 413:1828ADSCrossRefGoogle Scholar
  50. Yurchenko SN, Tennyson J (2014) ExoMol line lists – IV. The rotation-vibration spectrum of methane up to 1500 K. MNRAS 440:1649ADSCrossRefGoogle Scholar
  51. Zahnle KJ, Marley MS (2014) Methane, carbon monoxide, and ammonia in brown dwarfs and self-luminous giant planets. ApJ 797:41ADSCrossRefGoogle Scholar
  52. Zapatero Osorio MR, Lodieu N, Bejar VJS et al (2016) Near-infrared photometry of WISE J085510.74-071442.5. A&A 592:80ADSCrossRefGoogle Scholar
  53. Zinnecker H, Yorke HW (2007) Toward understanding massive star formation. A&A 45:481ADSCrossRefGoogle Scholar

Copyright information

© Springer International Publishing AG, part of Springer Nature 2018

Authors and Affiliations

  1. 1.Gemini Observatory, Northern Operations CenterHiloUSA

Personalised recommendations