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Joined 2026-09-21 Message
Incoming links: Maser
Galactic-centre stellar-orbit experiments 2026-10-18
Rainer Schödel, Reinhard Genzel and collaborators combined NTT imaging with VLT adaptive-optics infrared observations. Silicon-monoxide masers registered stellar images to the radio position of Sagittarius A*. Their 2002 observations included S2's closest approach; a fitted Kepler orbit constrained a concentrated central mass. Rejecting a particular extended cluster also required its density and survival assumptions.[ref]
Andrea Ghez and collaborators combined Keck speckle imaging and laser-guide-star adaptive optics with infrared spectra. Image fitting supplied angular positions; spectral lines supplied velocities. The 2008 analysis treated optical distortion, coordinate alignment and blended sources: a shifting photocentre can imitate motion. Joint angular and spectral fitting constrained both distance and mass, with assumptions about central radial motion affecting the result. Apparatus calibration and confusion tests are therefore part of the dynamical inference.[ref]
Measuring Distance and Properties of the Milky Way's Central Supermassive Black Hole with Stellar Orbits by Andrea M. Ghez and others. PDF §§2–4 and Appendices A–C: imaging, spectroscopy, source confusion and orbital fit
Hydrogen maser 2026-10-18
Nobel Prize in Physics in 1964 2026-10-18
One half went to Charles Hard Townes; the other half jointly to Nicolay Gennadiyevich Basov and Aleksandr Mikhailovich Prokhorov, for quantum-electronics work leading to oscillators and amplifiers using the maser-laser principle.[ref]
The Nobel Prize in Physics 1964 by Nobel Prize Outreach. Individual official award summary: Townes one-half; Basov and Prokhorov one-quarter each; common quantum-electronics motivation.
In 1965, Arno Penzias and Robert Woodrow Wilson reported measurements with a 20-foot horn-reflector antenna at . They manually switched a traveling-wave maser receiver between the horn and a helium-cooled reference. From zenith antenna temperature, atmospheric and antenna/ground contributions left an excess .[ref]
A Measurement of Excess Antenna Temperature at 4080 Mc per Second by Arno Allan Penzias and Robert Woodrow Wilson. pp.419–420: apparatus, temperature contributions and residual
Elevation scans estimated the atmospheric term. Taping horn seams produced no measurable change; a nearby transmitter tested ground response. These controls addressed distinct possible contaminations.[ref]
The comparison does not make all nuisance contributions disappear. A reference can establish a response scale, but atmospheric emission and pickup through unwanted antenna directions are also real incident radiation. In his later account, Robert Woodrow Wilson describes these competing contributions as central to a radio astronomy measurement.[ref]
The Cosmic Microwave Background Radiation by Robert Woodrow Wilson. 1978 lecture, introduction and sectionII: sky, ground, atmosphere and instrument contributions
The Princeton group proposed primordial thermal radiation as an interpretation and called for more wavelength measurements. Their separate radiometer had not yet produced results.[ref]
Cosmic Black-Body Radiation by R. H. Dicke and others. pp.415–416: interpretation, Princeton apparatus and need for further wavelengths
A single-frequency excess therefore does not by itself establish a complete Planck spectrum. Reproducibility across independent instruments, observing directions and frequencies tests the interpretation further.