Doomsday

Dr Klaus­Peter Schröder UGTO, Departamento de Astronomia / IFUG, Mexico Doomsday ­ will we once be at the mercy of neutrinos?! Workshop „From neutrinos to dark matter“, IFUG, Leon, 25.8. 2006
Dr. Klaus­Peter Schröder, UGTO The astrophysical „doomsday“ scenario : Will a supergiant Sun, in the distant future of about 7.5 billion years, finally swallow Earth?!
Dr. Klaus­Peter Schröder, UGTO The conventional solar evolution model, w/o mass loss: log R / R(sun,today) !! Orbit of Earth 1. 2. Core­He burning H­shell­burning, degenerate He­core => He­flash 1.: first giant stadium, (RGB giant) 2.: second giant stadium, (AGB giant)
Dr. Klaus­Peter Schröder, UGTO „There is always hope“ 1) : Solar evolution with mass loss ! Earth orbit expands!! (2) e.g., Schröder et al. 2001, Astron.&Geophys. 42, 26
RGB AGB (1) Aragon, in: „Lord of the Rings“ Dr. Klaus­Peter Schröder, UGTO But no reason to rejoice: It´ll be HOT !! L­Sun ~ 2000 to 6000x of L­today!!
Dr. Klaus­Peter Schröder, UGTO Another „myth“: Will the Sun really form a Planetary Nebula at the end ?! dM/dt final ~30,000 yrs: a dust­driven „Superwind“ (3) Schröder et al.., A&A 349 (1999): needs critical L > 6000L­sun tip­AGB evolution in the HRD Lc
M initial = 2.65 M Sun , Z=0.02 Planetary Nebula Dr. Klaus­Peter Schröder, UGTO Close escape for „us“, but not for Venus and Mercury ! Radius / AU
>0.25 AU ! Orbit of Earth Orbit of Venus Radius of RGB­Sun, evolution model with mass loss Final 10 Million years of the Sun as RGB giant Dr. Klaus­Peter Schröder, UGTO But how do we know the exact mass loss by cool winds ? 4)
for 30 years (!): Reimers´ relation : dM /dt = h L R / M ....used a lot, but was not derived from physics (4) Reimers 1977, A&A 61, 217 Dr. Klaus­Peter Schröder, UGTO 5) So, if we use characteristic chromospheric properties (instead of photospheric L, R) then: dM/dt = [ h L R / M ] x 3.5 (Teff /4000K) x ( 1 + (gsun /4300 gstar)) .......and the calibration ?? (5) Schröder & Cuntz 2005, ApJL 630,L73
Dr. Klaus­Peter Schröder, Astronomy Centre Idea: Use HB stars in Globular Clusters!
Dr. Klaus­Peter Schröder, Astronomy Centre Idea: Use HB stars in Globular Clusters! ­ gives a well­defined total RGB mass­loss ­ avoids variability by probing long time span
Dr. Klaus­Peter Schröder, UGTO Test, e.g., w/ NGC 5904: Z = 0.0009, Mi = 0.86 Mo Colour­Magnitude Diagramme from HST­data (indicative of temperature)
Dr. Klaus­Peter Schröder, UGTO 6) BUT: it all depends on neutrinos, too ! ­ Raffelt´s idea : The cooling­rate of degenerate He­cores (& WDs) depends on the neutrino magnetic dipole moment, µ Neutrino cooling delays He­flash and increases maximum RGB He­core mass, Mc, and, consequently, L(tip­RGB) Raffelt & Weiss 1992: µ < 3 E­12 µB, if dMc<0.025Msun w/ todays stellar models: L(tip­RGB) should tell Mc even better .....so, what is L(tip­RGB), and what to expect for the RGB Sun? (6) Raffelt 1996, in: „Stars as Laboratories for Fundamental Physics“, University of Chicago Press
Dr. Klaus­Peter Schröder, UGTO L(tip­RGB) ?? ­ Again, Globular Clusters can tell us ! i.e., NGC 5927, with near (~1/2) solar metal abundances: L(tip­RGB) ......hence, future work will soon give a revised upper limit on the neutrino magnetic dipole moment
Dr. Klaus­Peter Schröder, UGTO Conclusions : The mass loss of the solar giant will, most likely, save planet Earth from the doomsday scenario ! A large neutrino dipole moment µ would lead to a larger­than­critical solar RGB giant, but astrophyiscal evidence speaks against it. Improved observations of RGB giants in Globular Clusters and better stellar models (i.e., with mass­loss) allow us to give a better upper limit on µ, soon. <watch this space>
Dr. Klaus­Peter Schröder, UGTO NGC 5927: Z = 0.01, Mi(HB/KGC) = 0.99 Mo
Dr. Klaus­Peter Schröder, UGTO RGB­ML yields in comparison: using the well constrained masses of blue­end HB­stars s(M) ~ 0.02...0.04 Msun => s(h) ~ 10%....20%
Z Mi(HB) M(HB) DMRGB h
hR *) NGC 5904 0.0009 0.86 0.60 0.26 0.8E­13 2.4E­13 NGC 5927 0.01 0.99 0.71 0.28 0.8E­13 2.0E­13 *) The old Reimers relation cannot do both mass loss yields with the same h ! Dr Klaus­Peter Schröder UGTO, Departamento de Astronomia, Mexico The „Doomsday“ scenario: At the mercy of a supergiant Sun and its mass­loss ( ......in about 7.5 billion years from now)