The devil is in the distance

Article Abstract:

Research using the Hubble Space Telescope has identified 15 giant pulsating stars, known as Cepheids, in the galaxy NGC4258. It was possible to record variations in the brightness of these stars. The distance to the galaxy was found to be 8.1 plus or minus 0.4 Mpc, which is different by around 12% from the master distance. It was concluded that, if the master distance is accepted as the more accurate one, then the value of the Hubble constant obtained by the Hubble Space Telescope Key Project will have to be raised by 12%. This would cut the age of the Universe by 12% to around 12 billion years.

Author: Paczynski, Bohdan
Galaxies, Cosmology

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The first visible burst

Article Abstract:

Gamma ray bursts were first discovered in 1973 and were described as rapid, sporadic, on-off flashes of high energy photons in the sky lasting for about 5 milliseconds to a few hours. The origin of these bursts are still unknown however, in 1992 the Burst and Transient Source Experiment (BATSE) instrument satellite BeppoSAX can detect burst optical transient or x-ray afterglow which can be visible within 1-3 hours giving astronomers adequate time to study.

Author: Paczynski, Bohdan, Wijers, Ralph
Measurement, Gamma ray astronomy, Gamma rays, Astrophysics

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Planetary candidates

Article Abstract:

Issues are presented concerning the use of microlensing techniques to determine the existence of wandering planets which are free to move through interstellar space. The number of free-roaming planets which exist is discussed.

Author: Paczynski, Bohdan
Evaluation, Observations, Astronomical research, Optical properties, Planets, Interstellar matter, Interstellar medium

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Subjects list: Research
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