Status Report

Sagittarius A* Rivaled the Sun in the Ancient X-ray Sky

By SpaceRef Editor
January 30, 2015
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Xian Chen, Pau Amaro-Seoane

(Submitted on 17 Dec 2014)

Sagittarius A*, lying the Galactic Center 8 kpc from Earth, hosts the closest supermassive black hole known to us. It is now inactive, but there are evidences indicating that about six million years ago it underwent a powerful outburst where the luminosity could have approached the Eddington limit. Motivated by the fact that in extragalaxies the supermassive black holes with similar masses and near-Eddington luminosities are usually strong X-ray emitters, we calculate here the X-ray luminosity of Sagittarius A*, assuming that the outburst was due to accretion of gas or tidal disruption of stars, both scenarios having been considered to trigger the previous outburst. We show that in both cases Sagittarius A* could precipitate on Earth an X-ray (h>2 keV) irradiance comparable to that from the current quiescent sun.

The irradiance in harder energy band 20 keV < h<100 keV, however, surpasses that from an X-class solar flare, and the irradiation timescale is also much longer, ranging from weeks to 105 years depending on the outburst scenario. This level of radiation would disturb the ozone and ionosphere around the ancient earth, and affect the abundance of organic molecules in dense interstellar environments around the solar neighbourhood, but these prospects have not been adequately explored so far. Our results indicate that the activity of supermassive black hole and the origin and evolution of life may be more closely linked than previously has been thought.

Comments: Submitted. Comments welcome. Both authors contributed equally to this research project. Correspondence and requests for materials should be addressed to

Subjects: High Energy Astrophysical Phenomena (astro-ph.HE); Cosmology and Nongalactic Astrophysics (astro-ph.CO); General Relativity and Quantum Cosmology (gr-qc)

Cite as: arXiv:1412.5592 [astro-ph.HE] (or arXiv:1412.5592v1 [astro-ph.HE] for this version)

Submission history

From: Pau Amaro-Seoane 

[v1] Wed, 17 Dec 2014 21:00:12 GMT (66kb,D)


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