October 18, 2017

22.01.11: A Quasar Campaign.

  Field for 3C 273. (Credit: Marcus Hauser Landessternwarte Heidelberg-Koenigstuhl)

   A call recently went out from the American Association of Variable Star Observers (AAVSO) that we thought was worth passing along. Specifically, Alert Notice 430 is calling for well-equipped and skilled observers to monitor to two exotic objects: Blazar-type quasars 3C 273 and 3C 279. If 3C 273 is sounding familiar, that’s because it was one of our astronomy challenges last year; at around magnitude +12.7, 3C 273 was the first quasar identified as such and is one of the brightest quasars in the sky. [Read more...]

25.04.10-First Extra-solar Magnetic Loop Recorded.

 

(Credit: Peterson, NRAO/NSF).

(Credit: Peterson, NRAO/NSF).

Artist’s conception of the radio flare superimposed over the Algol system.

   Radio-Interferometry has really shown its stuff as of late. Recently, astronomers have used a collaboration of radio telescopes based planet-wide to study a familiar variable star; Algol in the constellation Perseus. Known since Arabic times as “The Demon Star,” Algol is an eclipsing binary, where two stars are locked in a 5.8 million mile embrace and “eclipse” each other from our vantage point. This explanation has been known since 1889, but radio astronomers have added another unique feature to the pair; a long pair of magnetic loops connecting the two stars. “This is the first time we’ve seen a feature like this in the magnetic field of any star other than the Sun,” stated William Peterson of the University of Iowa. The scopes linked included the NSF’s Very Long Baseline Array, Green Bank, and the Effelsburg Radio telescope based in Germany.  Collectively, the setup is known as the High Sensitivity Array. Algol is about 93 light years distant, and is a variable star that can be easily monitored by even beginning amateurs with the naked eye.

10.04.10- Radio Astronomers Refine Celestial Grid.

(Credit: Image courtesy of NRAO/AUI and Earth image courtesy of the SeaWiFS Project NASA/GSFC and ORBIMAGE)

(Credit: Image courtesy of NRAO/AUI and Earth image courtesy of the SeaWiFS Project NASA/GSFC and ORBIMAGE)

 The VLBA family of radio telescopes!

   Getting a good fix on positions both on the Earth and in the sky is tougher than it may sound. Tectonic plates move. The Moon raises tides under our feet. The whole planet orbits our Sun, which is itself flying about the galaxy and getting jostled by other stars, as the galaxies themselves are flying apart. Last year, however, astronomers at the National Science Foundation’s Very Long Baseline Array of radio telescopes tackled the problem in a novel way. Using 35 radio telescopes worldwide, they monitored and measured the positions 243 quasars over a 24 hour period starting November 18th 2008. Quasars are ideal candidates for this kind of measurement because of their extreme distance. These high precession measurements break the old record for the most radio dishes employed, which stood at 23. The telescopes utilized a method known as Very Long Baseline Interferometry, which combines simultaneous signals collected over individually spaced telescopes to increase resolution power. Headquartered in Socorro, New Mexico, the VLA’s data will not only refine astronomical measurements, but increase the accuracy of geophysical science as well.

11.10.09: Zooming in on Blazars.

Astronomers have recently utilized an enormous radio telescope to examine some of the most exotic objects in the universe; active galactic nuclei. Sometimes called “Blazars”, these distant galaxies are spewing huge jets of particles at amazing relativistic speeds. These emit immense energy across the electromagnetic spectrum. NASA’s Fermi Gamma Ray Space Telescope has identified and monitored these sources since its launch in 2008 and now scientists at the Max Planck Institute for Radio Astronomy have used the National Science Foundation’s Very Long Baseline Array (VLBA) to map these jets with unprecedented accuracy. The VLBA is a series of 10 interlinked radio telescopes spanning an area from the Virgin Islands to Hawaii that utilize interferometry to produce an effective baseline of 5,300 miles and can resolve details less than 100 light years across at a distance of 7 billion light years. Fermi, the predecessor to the Compton Gamma Ray Observatory that was de-orbited in 2000, scans the entire sky once every three hours looking for gamma-ray bursts. First spotted in the early 70′s during global monitoring of nuclear weapons tests, pinning down gamma-ray bursts has been the name of the game in astrophysics over the past decades. The backup study proves the link between the gamma-ray emissions seen by Fermi and the energetic radio jets pinpointed by the VLBA… expect more high resolution radio maps to come!