Radio telescopes have an advantage over optical telescopes, in that radio telescope can be used even in cloudy conditions here on Earth. That\u2019s because the longer wavelengths of radio waves can pass through clouds unhindered. However, some wavelengths are still partially obscured by portions of Earth\u2019s atmosphere, especially by the ionosphere which traps human-made Radio Frequency Interference (RFI). \u00a0<\/p>\n
Astronomers have developed a new calibration technique that allows them to take sharp images in low radio frequencies \u2014 between 16 and 30 MHz \u2014 for the first time, bypassing the influence of the ionosphere. The astronomers say this will allow them to study things like plasmas emanating from ancient black holes and perhaps even detect exoplanets that orbit small stars.<\/p>\n
<\/p>\n The technique was developed by an international team of researchers led by astronomers from Leiden University in the Netherlands.<\/p>\n \u201cIt\u2019s like putting on a pair of glasses for the first time and no longer seeing blurred,\u201d said Christian Groeneveld from Leiden University, who led the research.<\/p>\n The astronomers used the LOFAR telescope in Drenthe, the Netherlands, which is currently one of the best low-frequency radio telescopes in the world. They modified a calibration technique that has been used to improve observations for observing in radio at higher frequencies, around 150 MHz.<\/p>\n \u201cWe hoped that we could also extend this technique to lower frequencies, below 30 MHz,\u201d said, Reinout van Weeren, also from Leiden University, who came up with the idea. \u201cAnd we succeeded.\u201d<\/p>\n To test their technique, they studied several galaxy clusters that had previously only been studied in detail at higher frequencies.<\/p>\n \u201cOur observing strategy consisted of simultaneously observing a bright primary calibrator and the target fields,\u201d the team wrote in their paper. \u201cBy scheduling the observation after midnight, we minimized RFI caused by the internal reflection of terrestrial RFI by the ionosphere, which is significantly worse during the day, as ionizing radiation from the Sun increases the column density of ions in the ionosphere.\u201d<\/p>\n Then, they split up their field of view into several smaller \u201cfacets\u201d and self-calibrated each facet individually, against the calibrator object. \u201cThis yields an improved image and model of the sky, partly corrected for direction dependent effects,\u201d they wrote. They then repeated the calibrations three more times.<\/p>\n This was the first time radio images at frequencies between 16 and 30 MHz have been taken. Because of this data, the astronomers said that the radio emissions from these clusters is not evenly distributed across the entire cluster, but rather there is a spot pattern.<\/p>\n According to the researchers, the new calibration technique makes it possible to study radio phenomena in frequencies that were previously hidden.<\/p>\n \u201cThere is, of course, a chance that we will eventually discover something unexpected,\u201d said Groeneveld.<\/p>\n Read the press release from Astronomy Netherlands![\"\"](\"https:\/\/www.universetoday.com\/wp-content\/uploads\/2024\/06\/Oud-versus-nieuw-credit-LOFAR-Christian-Groeneveld-et-al-1-1024x477.jpg\")
Read the team\u2019s paper<\/p>\nLike this:<\/h3>\n