DOCSLIB.ORG

Evolution of Stars

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Evolution of Stars Evolution of Stars (Part I: Solar-type stars) 1 Death of the Sun Parts I and II 2 Learning goals: Be able to …. ! summarize the future of the Sun on a rough timescale; ! apply the basics of the conservation of energy and the battle between gravity and outward pressure to what “drives” a star to evolve at each major stage of evolution; ! explain what is meant by main sequence, subgiant, red giant branch, electron degeneracy, helium flash, horizontal branch, asymptotic giant branch, planetary nebula, white dwarf. 3 Be able to summarize the future of the Sun in a rough timescale. Apply the basics of the conservation of energy and the battle between gravely and pressure to what “drives” a star to evolve at each major stage of evolution. Explain what is meant by red giant branch, electron degeneracy, helium flash, horizontal branch, planetary nebula, white dwarf 4 5 http://chandra.harvard.edu/xray_sources/browndwarf_fg.html Brown Dwarf "In between a star and a planet "Jupiter < BD mass < 0.08 Sun "Radiates in infrared due to low temperature. "Mass too low to start fusion in core. "Slowly cools over trillions of years. 6 7 Core producing energy--Fusing H to He 8 A review of what we know the Sun is doing as a main-sequence star 9 Number of particles in core is decreasing. NET RESULT IN: 6 H OUT: 1 He + 2 H FUSION RATE MUST INCREASE TO OFFSET DECREASE IN PARTICLE PRESSURE! Sun is slowly becoming more and more luminous. 10 Explain how the Sun maintains a constant balance in its interior (solar thermostat) Part of the pressure depends on the number of particles Pressure decreases, core shrinks slightly, pressure evens out, fusion rate must increase to offset the smaller pressure provided by the number of particles present. Luminosity of the Sun must increase! Summary for #1 on flowchart Stars on the main sequence: What is happening in the core? How does the rest of the star support itself? Describe the interior of the star. 11 12 Expanding Subgiant 13 MS very stable long lasting stage but H can fuse only in very center of star Why does core have to contract? Why doesn’t it keep on contracting? GPE-->KE-->thermal energy Discuss shell fusion and luminosity generated 14 Summary for #2 on flowchart Stars on the sub giant branch: Core runs out of hydrogen to fuse. What is happening in the core? How does the rest of the star support itself? 15 16 Core collapse stops Surface of star very far away! H # He fusion shell Helium ash Electron Degenerate degeneracy He Core supports the core. [No two electrons can occupy identical states.] 17 Degeneracy is a strange state of material. The pressure in the core does not depend on temperature. The core cannot expand and cool. Neither can it shrink any more. “Human” (molecular?) “Degeneracy” 18 Explain degeneracy. Illustrate the core gaining mass. Summary: star changes dramatically! Future Sun Today’s Sun 19 “climbing the red giant branch” What’s happening in the star ? Source of luminosity causes star’s radius to increase. Because surface is so far away from source of luminosity and there is such a huge area over which radiation escapes, star’s surface is cool. 20 Summary for #3 on flowchart Stars going up the red giant branch: Core core stops contracting; no fusion is occurring. What supports the core? How does the rest of the star support itself? Are gravity and outward pressure balanced? 21 No support from fusion, the core contracts. Potential energy converted to thermal energy. Thermal energy released initiates shell fusion of H to He. Extreme luminosity expands the rest of star Outward pressure greater than inward pull of gravity Core continues to contract until electron degeneracy sets in. Rest of star supported by thermal pressure. Shell fusion dumps helium ash on core. 22 What initiates helium fusion? 4 Helium flash! Core does not expand and cool so nuclear runaway occurs - the fusion of 3He -> carbon begins. 23 Compare the sizes from main sequence star to red giant to horizontal branch star. 5 6 7 24 What is happening in the core? What supports the star now? Helium - to - carbon fusion (triple-alpha fusion) Only 2 gamma rays produced. Why does helium to carbon fusion have to have high temperatures and a high fusion rate? 25 Where is the star on HRD? 26 After He flash, temperature and luminosity depend on how much mass the star lost as it “climbed” the red giant branch Core gets enough mass that temperature reaches He fusion limit. Luminosity drops as equilibrium starts again. Core supported by He to C fusion. Rest of star supported by radiation and thermal pressure. Star is on horizontal branch; second longest stage of its life. 27 Summary for #5 on flowchart Stars is a horizontal branch star: What is happening in the core? Anything happening around the core? How does the rest of the star support itself? 28 5 6 7 29 Core runs out of helium. "Core: contracting until electron degeneracy sets in again; giving off energy GPE TE " Shells start fusion " H#He " He#C C 30 Fusion of He to c operates at very high Pressures and temps and in a much smaller volume than H to He. Eventually the supply gives out. Explain what happens in the core, shells, atmosphere, etc. Draw a diagram. 31 Summary for #6 on flowchart Star leaves the horizontal branch: Core runs out of helium. What happens in the core? What happens around the core? How does the rest of the star support itself? Are outward pressure and gravity balanced? 32 5 6 7 33 "Rest of star responding to huge luminosity coming from shell fusion " Outer parts of star start to reach escape velocity – star is unstable! 34 35 Summary for #7 on flowchart Star is at the tip of the “asymptotic” branch: Core stops contracting; no fusion is occurring. What supports the core? How does the rest of the star support itself? Are gravity and outward pressure balanced? 36 End of the road for Sun-like stars 8 37 Fusion stops at carbon for solar-mass stars; Atmosphere is not in gravitational equilibrium; ~ 30% of mass of the star gets expelled; Central remnant called a white dwarf -- size of the Earth -- EXTREMELY dense; Gaseous object called a Planetary nebula " White dwarf will 9 slowly cool to a cold, black carbon cinder of about 0.7 solar “WHITE DWARF” masses " “Mass sink” # . material does not go back into ISM. http://news.bbc.co.uk/2/hi/science/nature/3492919.stm 38 End of the road for our Sun and similar stars. Material does not go back into the ISM. Core contracts and heats up; thermal energy ignites shell fusion. Double-shell fusion is very unstable process. Rest of star expands enormously due to extreme luminosity. Thermal pulses give outer regions escape velocity. Carbon core eventually supported by electron degeneracy. Rest of star expands away into interstellar space. Fusion of sun-like stars stops with carbon. Core never gets hot enough to fuse carbon. Core turns becomes a white dwarf. White dwarfs cool over trillions of years. Evolution of the Sun Notice “rapid” increase in luminosity Trouble starts here! 39 Evolutionary tracks of the Sun SUMMARY 40 .
Load more

Recommended publications
  • The Variable Stars and Blue Horizontal Branch of the Metal-Rich Globular Cluster NGC 6441
    View metadata, citation and similar papers at core.ac.uk brought to you by CORE provided by CERN Document Server The Variable Stars and Blue Horizontal Branch of the Metal-Rich Globular Cluster NGC 6441 Andrew C. Layden1;2 Physics & Astronomy Dept., Bowling Green State Univ., Bowling Green, OH 43403, U.S.A. Laura A. Ritter Department of Astronomy, University of Michigan, Ann Arbor, MI 48109-1090, U.S.A. Douglas L. Welch1,TracyM.A.Webb1 Department of Physics & Astronomy, McMaster University, Hamilton, Ontario L8S 4M1, Canada ABSTRACT We present time-series VI photometry of the metal-rich ([Fe=H]= 0:53) globular − cluster NGC 6441. Our color-magnitude diagram shows that the extended blue horizontal branch seen in Hubble Space Telescope data exists in the outermost reaches of the cluster. About 17% of the horizontal branch stars lie blueward and brightward of the red clump. The red clump itself slopes nearly parallel to the reddening vector. A component of this slope is due to differential reddening, but part is intrinsic. The blue horizontal branch stars are more centrally concentrated than the red clump stars, suggesting mass segregation and a possible binary origin for the blue horizontal branch stars. We have discovered 50 new variable stars near NGC 6441, among ∼ them eight or more RR Lyrae stars which are highly-probable cluster members. Comprehensive period searches over the range 0.2–1.0 days yielded unusually long periods (0.5–0.9 days) for the fundamental pulsators compared with field RR Lyrae of the same metallicity. Three similar long-period RR Lyrae are known in other metal-rich globulars.
    [Show full text]
  • XIII Publications, Presentations
    XIII Publications, Presentations 1. Refereed Publications E., Kawamura, A., Nguyen Luong, Q., Sanhueza, P., Kurono, Y.: 2015, The 2014 ALMA Long Baseline Campaign: First Results from Aasi, J., et al. including Fujimoto, M.-K., Hayama, K., Kawamura, High Angular Resolution Observations toward the HL Tau Region, S., Mori, T., Nishida, E., Nishizawa, A.: 2015, Characterization of ApJ, 808, L3. the LIGO detectors during their sixth science run, Classical Quantum ALMA Partnership, et al. including Asaki, Y., Hirota, A., Nakanishi, Gravity, 32, 115012. K., Espada, D., Kameno, S., Sawada, T., Takahashi, S., Ao, Y., Abbott, B. P., et al. including Flaminio, R., LIGO Scientific Hatsukade, B., Matsuda, Y., Iono, D., Kurono, Y.: 2015, The 2014 Collaboration, Virgo Collaboration: 2016, Astrophysical Implications ALMA Long Baseline Campaign: Observations of the Strongly of the Binary Black Hole Merger GW150914, ApJ, 818, L22. Lensed Submillimeter Galaxy HATLAS J090311.6+003906 at z = Abbott, B. P., et al. including Flaminio, R., LIGO Scientific 3.042, ApJ, 808, L4. Collaboration, Virgo Collaboration: 2016, Observation of ALMA Partnership, et al. including Asaki, Y., Hirota, A., Nakanishi, Gravitational Waves from a Binary Black Hole Merger, Phys. Rev. K., Espada, D., Kameno, S., Sawada, T., Takahashi, S., Kurono, Lett., 116, 061102. Y., Tatematsu, K.: 2015, The 2014 ALMA Long Baseline Campaign: Abbott, B. P., et al. including Flaminio, R., LIGO Scientific Observations of Asteroid 3 Juno at 60 Kilometer Resolution, ApJ, Collaboration, Virgo Collaboration: 2016, GW150914: Implications 808, L2. for the Stochastic Gravitational-Wave Background from Binary Black Alonso-Herrero, A., et al. including Imanishi, M.: 2016, A mid-infrared Holes, Phys.
    [Show full text]
  • The Evolution of Helium White Dwarfs: Applications to Millisecond
    Pulsar Astronomy — 2000 and Beyond ASP Conference Series, Vol. 3 × 108, 1999 M. Kramer, N. Wex, and R. Wielebinski, eds. The evolution of helium white dwarfs: Applications for millisecond pulsars T. Driebe and T. Bl¨ocker Max-Planck-Institut f¨ur Radioastronomie, Bonn, Germany D. Sch¨onberner Astrophysikalisches Institut Potsdam, Potsdam, Germany 1. White Dwarf Evolution Low-mass white dwarfs with helium cores (He-WDs) are known to result from mass loss and/or exchange events in binary systems where the donor is a low mass star evolving along the red giant branch (RGB). Therefore, He-WDs are common components in binary systems with either two white dwarfs or with a white dwarf and a millisecond pulsar (MSP). If the cooling behaviour of He- WDs is known from theoretical studies (see Driebe et al. 1998, and references therein) the ages of MSP systems can be calculated independently of the pulsar properties provided the He-WD mass is known from spectroscopy. Driebe et al. (1998, 1999) investigated the evolution of He-WDs in the mass range 0.18 < MWD/M⊙ < 0.45 using the code of Bl¨ocker (1995). The evolution of a 1 M⊙-model was calculated up to the tip of the RGB. High mass loss termi- nated the RGB evolution at appropriate positions depending on the desired final white dwarf mass. When the model started to leave the RGB, mass loss was virtually switched off and the models evolved towards the white dwarf cooling branch. The applied procedure mimicks the mass transfer in binary systems. Contrary to the more massive C/O-WDs (MWD ∼> 0.5 M⊙, carbon/oxygen core), whose progenitors have also evolved through the asymptotic giant branch phase, He-WDs can continue to burn hydrogen via the pp cycle along the cooling branch arXiv:astro-ph/9910230v1 13 Oct 1999 down to very low effective temperatures, resulting in cooling ages of the order of Gyr, i.
    [Show full text]
  • Curriculum Vitae - 24 March 2020
    Dr. Eric E. Mamajek Curriculum Vitae - 24 March 2020 Jet Propulsion Laboratory Phone: (818) 354-2153 4800 Oak Grove Drive FAX: (818) 393-4950 MS 321-162 [email protected] Pasadena, CA 91109-8099 https://science.jpl.nasa.gov/people/Mamajek/ Positions 2020- Discipline Program Manager - Exoplanets, Astro. & Physics Directorate, JPL/Caltech 2016- Deputy Program Chief Scientist, NASA Exoplanet Exploration Program, JPL/Caltech 2017- Professor of Physics & Astronomy (Research), University of Rochester 2016-2017 Visiting Professor, Physics & Astronomy, University of Rochester 2016 Professor, Physics & Astronomy, University of Rochester 2013-2016 Associate Professor, Physics & Astronomy, University of Rochester 2011-2012 Associate Astronomer, NOAO, Cerro Tololo Inter-American Observatory 2008-2013 Assistant Professor, Physics & Astronomy, University of Rochester (on leave 2011-2012) 2004-2008 Clay Postdoctoral Fellow, Harvard-Smithsonian Center for Astrophysics 2000-2004 Graduate Research Assistant, University of Arizona, Astronomy 1999-2000 Graduate Teaching Assistant, University of Arizona, Astronomy 1998-1999 J. William Fulbright Fellow, Australia, ADFA/UNSW School of Physics Languages English (native), Spanish (advanced) Education 2004 Ph.D. The University of Arizona, Astronomy 2001 M.S. The University of Arizona, Astronomy 2000 M.Sc. The University of New South Wales, ADFA, Physics 1998 B.S. The Pennsylvania State University, Astronomy & Astrophysics, Physics 1993 H.S. Bethel Park High School Research Interests Formation and Evolution
    [Show full text]
  • (GK 1; Pr 1.1, 1.2; Po 1) What Is a Star?
    1) Observed properties of stars. (GK 1; Pr 1.1, 1.2; Po 1) What is a star? Why study stars? The sun Age of the sun Nearby stars and distribution in the galaxy Populations of stars Clusters of stars Distances and characterization of stars Luminosity and flux Magnitudes Parallax Standard candles Cepheid variables SN Ia 2) The HR diagram and stellar masses (GK 2; Pr 1.4; Po 1) Colors of stars B-V Blackbody emission HR Diagram Interpretation of HR diagram stellar radii kinds of stars red giants white dwarfs planetary nebulae AGB stars Cepheids Horizontal branch evolutionary sequence turn off mass and ages Masses from binaries Circular orbits solution General solution Spectroscopic binaries Eclipsing spectroscopic binaries Empirical mass luminosity relation 3) Spectroscopy and abundances (GK 1; Pr 2) Stellar spectra OBFGKM Atomic physics H atom others Spectral types Temperature and spectra Boltzmann equation for levels Saha equation for ionization ionization stages Rotation Stellar Abundances More about ionization stages, e.g. Ca and H Meteorite abundances Standard solar set Abundances in other stars and metallicity 4) Hydrostatic balance, Virial theorem, and time scales (GK 3,4; Pr 1.3, 2; Po 2,8) Assumptions - most of the time Fully ionized gas except very near surface where partially ionized Spherical symmetry Broken by e.g., convection, rotation, magnetic fields, explosion, instabilities, etc Makes equations a lot easier Limits on rotation and magnetic fields Homogeneous composition at birth Isolation (drop this later in course) Thermal
    [Show full text]
  • Brown Dwarf: White Dwarf: Hertzsprung -Russell Diagram (H-R
    Types of Stars Spectral Classifications: Based on the luminosity and effective temperature , the stars are categorized depending upon their positions in the HR diagram. Hertzsprung -Russell Diagram (H-R Diagram) : 1. The H-R Diagram is a graphical tool that astronomers use to classify stars according to their luminosity (i.e. brightness), spectral type, color, temperature and evolutionary stage. 2. HR diagram is a plot of luminosity of stars versus its effective temperature. 3. Most of the stars occupy the region in the diagram along the line called the main sequence. During that stage stars are fusing hydrogen in their cores. Various Types of Stars Brown Dwarf: White Dwarf: Brown dwarfs are sub-stellar objects After a star like the sun exhausts its nuclear that are not massive enough to sustain fuel, it loses its outer layer as a "planetary nuclear fusion processes. nebula" and leaves behind the remnant "white Since, comparatively they are very cold dwarf" core. objects, it is difficult to detect them. Stars with initial masses Now there are ongoing efforts to study M < 8Msun will end as white dwarfs. them in infrared wavelengths. A typical white dwarf is about the size of the This picture shows a brown dwarf around Earth. a star HD3651 located 36Ly away in It is very dense and hot. A spoonful of white constellation of Pisces. dwarf material on Earth would weigh as much as First directly detected Brown Dwarf HD 3651B. few tons. Image by: ESO The image is of Helix nebula towards constellation of Aquarius hosts a White Dwarf Helix Nebula 6500Ly away.
    [Show full text]
  • The Formation of Brown Dwarfs 459
    Whitworth et al.: The Formation of Brown Dwarfs 459 The Formation of Brown Dwarfs: Theory Anthony Whitworth Cardiff University Matthew R. Bate University of Exeter Åke Nordlund University of Copenhagen Bo Reipurth University of Hawaii Hans Zinnecker Astrophysikalisches Institut, Potsdam We review five mechanisms for forming brown dwarfs: (1) turbulent fragmentation of molec- ular clouds, producing very-low-mass prestellar cores by shock compression; (2) collapse and fragmentation of more massive prestellar cores; (3) disk fragmentation; (4) premature ejection of protostellar embryos from their natal cores; and (5) photoerosion of pre-existing cores over- run by HII regions. These mechanisms are not mutually exclusive. Their relative importance probably depends on environment, and should be judged by their ability to reproduce the brown dwarf IMF, the distribution and kinematics of newly formed brown dwarfs, the binary statis- tics of brown dwarfs, the ability of brown dwarfs to retain disks, and hence their ability to sustain accretion and outflows. This will require more sophisticated numerical modeling than is presently possible, in particular more realistic initial conditions and more realistic treatments of radiation transport, angular momentum transport, and magnetic fields. We discuss the mini- mum mass for brown dwarfs, and how brown dwarfs should be distinguished from planets. 1. INTRODUCTION form a smooth continuum with those of low-mass H-burn- ing stars. Understanding how brown dwarfs form is there- The existence of brown dwarfs was first proposed on the- fore the key to understanding what determines the minimum oretical grounds by Kumar (1963) and Hayashi and Nakano mass for star formation. In section 3 we review the basic (1963).
    [Show full text]
  • Reionization the End of the Universe
    Reionization The End of the Universe How will the Universe end? Is this the only Universe? What, if anything, will exist after the Universe ends? Universe started out very hot (Big Bang), then expanded: Some say the world will end in fire, Some say in ice. From what I’ve tasted of desire I hold with those who favor fire. But if I had to perish twice, I think I know enough of hate To know that for destruction ice is also great And would suffice. How it ends depends on the geometry of the Universe: Robert Frost 2) More like a saddle than a sphere, with curvature in the opposite The Geometry of Curved Space sense in different dimensions: "negative" curvature. Possibilities: Sum of the 1) Space curves back on itself (like a sphere). "Positive" curvature. Angles < 180 Sum of the Angles > 180 3) A more familiar flat geometry. Sum of the Angles = 180 1 The Geometry of the Universe determines its fate Case 1: high density Universe, spacetime is positively curved Result is “Big Crunch” Fire The Five Ages of the Universe Cases 2 or 3: open Universe (flat or negatively curved) 1) The Primordial Era 2) The Stelliferous Era 3) The Degenerate Era 4) The Black Hole Era Current measurements favor an open Universe 5) The Dark Era Result is infinite expansion Ice 1. The Primordial Era: 10-50 - 105 y The Early Universe Inflation Something triggers the Creation of the Universe at t=0 A problem with microwave background: Microwave background reaches us from all directions.
    [Show full text]
  • Hydrogen-Deficient Stars
    Hydrogen-Deficient Stars ASP Conference Series, Vol. 391, c 2008 K. Werner and T. Rauch, eds. Hydrogen-Deficient Stars: An Introduction C. Simon Jeffery Armagh Observatory, College Hill, Armagh BT61 9DG, N. Ireland, UK Abstract. We describe the discovery, classification and statistics of hydrogen- deficient stars in the Galaxy and beyond. The stars are divided into (i) massive / young star evolution, (ii) low-mass supergiants, (iii) hot subdwarfs, (iv) cen- tral stars of planetary nebulae, and (v) white dwarfs. We introduce some of the challenges presented by these stars for understanding stellar structure and evolution. 1. Beginning Our science begins with a young woman from Dundee in Scotland. The brilliant Williamina Fleming had found herself in the employment of Pickering at the Harvard Observatory where she noted that “the spectrum of υ Sgr is remarkable since the hydrogen lines are very faint and of the same intensity as the additional dark lines” (Fleming 1891). Other stars, well-known at the time, later turned out also to have an unusual hydrogen signature; the spectacular light variations of R CrB had been known for a century (Pigott 1797), while Wolf & Rayet (1867) had discovered their emission-line stars some forty years prior. It was fifteen years after Fleming’s discovery that Ludendorff (1906) observed Hγ to be completely absent from the spectrum of R CrB, while arguments about the hydrogen content of Wolf-Rayet stars continued late into the 20th century. Although these early observations pointed to something unusual in the spec- tra of a variety of stars, there was reluctance to accept (or even suggest) that hydrogen might be deficient.
    [Show full text]
  • The Deaths of Stars
    The Deaths of Stars 1 Guiding Questions 1. What kinds of nuclear reactions occur within a star like the Sun as it ages? 2. Where did the carbon atoms in our bodies come from? 3. What is a planetary nebula, and what does it have to do with planets? 4. What is a white dwarf star? 5. Why do high-mass stars go through more evolutionary stages than low-mass stars? 6. What happens within a high-mass star to turn it into a supernova? 7. Why was SN 1987A an unusual supernova? 8. What was learned by detecting neutrinos from SN 1987A? 9. How can a white dwarf star give rise to a type of supernova? 10.What remains after a supernova explosion? 2 Pathways of Stellar Evolution GOOD TO KNOW 3 Low-mass stars go through two distinct red-giant stages • A low-mass star becomes – a red giant when shell hydrogen fusion begins – a horizontal-branch star when core helium fusion begins – an asymptotic giant branch (AGB) star when the helium in the core is exhausted and shell helium fusion begins 4 5 6 7 Bringing the products of nuclear fusion to a giant star’s surface • As a low-mass star ages, convection occurs over a larger portion of its volume • This takes heavy elements formed in the star’s interior and distributes them throughout the star 8 9 Low-mass stars die by gently ejecting their outer layers, creating planetary nebulae • Helium shell flashes in an old, low-mass star produce thermal pulses during which more than half the star’s mass may be ejected into space • This exposes the hot carbon-oxygen core of the star • Ultraviolet radiation from the exposed
    [Show full text]
  • EVOLVED STARS a Vision of the Future Astron
    PUBLISHED: 04 JANUARY 2017 | VOLUME: 1 | ARTICLE NUMBER: 0021 research highlights EVOLVED STARS A vision of the future Astron. Astrophys. 596, A92 (2016) Loop Plume A B EDPS A nearby red giant star potentially hosts a planet with a mass of up to 12 times that of Jupiter. L2 Puppis, a solar analogue five billion years more evolved than the Sun, could give a hint to the future of the Solar System’s planets. Using ALMA, Pierre Kervella has observed L2 Puppis in molecular lines and continuum emission, finding a secondary source that is roughly 2 au away from the primary. This secondary source could be a giant planet or, alternatively, a brown dwarf as massive as 28 Jupiter masses. Further observations in ALMA bands 9 or 10 (λ ≈ 0.3–0.5 mm) can help to constrain the companion’s mass. If confirmed as a planet, it would be the first planet around an asymptotic giant branch star. L2 Puppis (A in the figure) is encircled by an edge-on circumstellar dust disk (inner disk shown in blue; surrounding dust in orange), which raises the question of whether the companion body is pre-existing, or if it has formed recently due to accretion processes within the disk. If pre-existing, the putative planet would have had an orbit similar in extent to that of Mars. Evolutionary models show that eventually this planet will be pulled inside the convective envelope of L2 Puppis by tidal forces. The companion’s interaction with the star’s circumstellar disk has invoked pronounced features above the disk: an extended loop of warm dusty material, and a visible plume, potentially launched by accretion onto a disk of material around the planet itself (B in the figure).
    [Show full text]
  • A Review on Substellar Objects Below the Deuterium Burning Mass Limit: Planets, Brown Dwarfs Or What?
    geosciences Review A Review on Substellar Objects below the Deuterium Burning Mass Limit: Planets, Brown Dwarfs or What? José A. Caballero Centro de Astrobiología (CSIC-INTA), ESAC, Camino Bajo del Castillo s/n, E-28692 Villanueva de la Cañada, Madrid, Spain; [email protected] Received: 23 August 2018; Accepted: 10 September 2018; Published: 28 September 2018 Abstract: “Free-floating, non-deuterium-burning, substellar objects” are isolated bodies of a few Jupiter masses found in very young open clusters and associations, nearby young moving groups, and in the immediate vicinity of the Sun. They are neither brown dwarfs nor planets. In this paper, their nomenclature, history of discovery, sites of detection, formation mechanisms, and future directions of research are reviewed. Most free-floating, non-deuterium-burning, substellar objects share the same formation mechanism as low-mass stars and brown dwarfs, but there are still a few caveats, such as the value of the opacity mass limit, the minimum mass at which an isolated body can form via turbulent fragmentation from a cloud. The least massive free-floating substellar objects found to date have masses of about 0.004 Msol, but current and future surveys should aim at breaking this record. For that, we may need LSST, Euclid and WFIRST. Keywords: planetary systems; stars: brown dwarfs; stars: low mass; galaxy: solar neighborhood; galaxy: open clusters and associations 1. Introduction I can’t answer why (I’m not a gangstar) But I can tell you how (I’m not a flam star) We were born upside-down (I’m a star’s star) Born the wrong way ’round (I’m not a white star) I’m a blackstar, I’m not a gangstar I’m a blackstar, I’m a blackstar I’m not a pornstar, I’m not a wandering star I’m a blackstar, I’m a blackstar Blackstar, F (2016), David Bowie The tenth star of George van Biesbroeck’s catalogue of high, common, proper motion companions, vB 10, was from the end of the Second World War to the early 1980s, and had an entry on the least massive star known [1–3].
    [Show full text]