Journal Article

Anthropic constraints on the cosmological constant from the Sun's motion through the Milky Way

L. Iorio

in Monthly Notices of the Royal Astronomical Society

Published on behalf of The Royal Astronomical Society

Volume 403, issue 3, pages 1469-1473
Published in print April 2010 | ISSN: 0035-8711
Published online April 2010 | e-ISSN: 1365-2966 | DOI: http://dx.doi.org/10.1111/j.1365-2966.2010.16212.x
Anthropic constraints on the cosmological constant from the Sun's motion through the Milky Way

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We tentatively look at anthropic constraints on the cosmological constant (CC) Λ at galactic scales by investigating its influence on the motion of the Sun throughout the Milky Way (MW) for −4.5 ≤t≤ 0 Gyr. In particular, we look at the Galactocentric distance to which the Sun is displaced at the end of the numerical integration of its equations of motion modified in order to include the effect of Λ. Values of Λ placing our star at its birth more than 10 kpc from the Galactic Centre (GC) are to be considered implausible, according to current views on the Galactic Habitable Zone (GHZ) on the metallicity level needed for the formation of stars. Values yielding approaches too close to the GC should also be excluded because of the risks to the evolution of life from too many nearby supernova explosions and gamma-ray bursts. We investigate the impact on our results of the uncertainties in both the MW model parameters and the Sun's initial conditions, in particular in the Hubble parameter H0 and the local standard of rest speed Θ0, accurate at levels of 2 and 6.2 per cent, respectively. Whereas H0= 70.1 km s−1 Mpc−1, Θ0= 254 km s−1 and Λ≤ 10−55 cm−2 locate the place of birth of the Sun at 19.6 kpc from the GC, the same values for H0 and Λ, and Θmax0= 270 km s−1 place it at the plausible Galactocentric distance of 8.5 kpc. Λ= 10−54 cm−2 and Λ= 10−53 cm−2 place the Sun at 10.6 kpc and 18.7 kpc, respectively.

Keywords: gravitation; Galaxy: general; Galaxy: solar neighbourhood; cosmological parameters

Journal Article.  3778 words.  Illustrated.

Subjects: Astronomy and Astrophysics

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