May or December?
Article Abstract:
The contradiction between spin periods and cooling time scale of a newly discovered binary pulsar has created confusion over the pulsar's age. Pulsar age can be calculated either by comparing currently observed spin periods to spin-down rates or by estimating the cooling time scale for the white dwarfs. D.R. Lorimer and colleagues have discovered a white dwarf in which these two measurements are very different. These observations raise questions about the development and number of pulsars.
Publication Name: Nature
Subject: Zoology and wildlife conservation
ISSN: 0028-0836
Year: 1995
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Conflict over the age of the universe
Article Abstract:
The age estimation of oldest stars in our galaxy by comparing stellar population in globular clusters to calibrated stellar models conflicts with the age of the Universe measured with the Hubble constant (Ho), the rate galaxies are receding from Earth and the cosmological Einstein-de Sitter model. The conflict arises because the estimated age of the oldest star in our galaxy is 16 Gyr which is significantly older than the Einstein-de Sitter age or current estimates of Ho.
Publication Name: Nature
Subject: Zoology and wildlife conservation
ISSN: 0028-0836
Year: 1995
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Dynamical evidence for a black hole in the eclipsing X-ray nova GRO J1655 - 40
Article Abstract:
The optical equivalent of a X-ray nova GRO J1655 - 40 with a black hole undergoes periodic eclipses. The consequent edge-on geometry of the nova is used to estimate the velocity of the companion star from where the black body attracts gases. The black hole has a mass of around 3.16 plus or minus 0.15 solar masses. This mass is obtained from the velocity curve of the companion star. The photometric data differ from theoretical estimates.
Publication Name: Nature
Subject: Zoology and wildlife conservation
ISSN: 0028-0836
Year: 1995
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