Tag: radio astronomy

Study identifies range of interference produced by Starlink satellites

8:58 am

In analyzing about 76 million radio images produced by the new Square Kilometer Array (SKA) in Australia scientists have found within them signals produced by SpaceX’s Starlink satellites.

PhD candidate and study lead Dylan Grigg said the team detected more than 112,000 radio emissions from 1806 Starlink satellites, making it the most comprehensive catalogue of satellite radio emissions at low frequencies to date. “Starlink is the most immediate and frequent source of potential interference for radio astronomy: it launched 477 satellites during this study’s four-month data collection period alone,” Mr Grigg said. “In some datasets, we found up to 30 per cent of our images showed interference from a Starlink satellite.”

Mr Grigg said the issue wasn’t just the number of satellites, but the strength of the signals and the frequencies they were visible at. “Some satellites were detected emitting in bands where no signals are supposed to be present at all, such as the 703 satellites we identified at 150.8 MHz, which is meant to be protected for radio astronomy,” Mr Grigg said. “Because they may come from components like onboard electronics and they’re not part of an intentional signal, astronomers can’t easily predict them or filter them out.”

The researchers were careful to note that SpaceX has been following all international regulations, and that these signals are not a violation of any law or regulation. Further, they emphasized that “Discussions we have had with SpaceX on the topic have been constructive.”

Because many other such constellations are now being launched — with several from China that normally does not negotiate these issues like SpaceX — the scientists want new international regulations imposed to protect their work.

More and more it seems astronomers should simply move their operations into space or the Moon, where such issues will not exist. Getting above the atmosphere and away from our modern technological society provides so many benefits for research the move should be a no-brainer. That it is now also much cheaper to do it (thanks to SpaceX) makes the move even more practical.

For some reason however the idea seems too difficult for many astronomers to fathom.

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Astronomers discover a perfect sphere in radio

1:20 pm

Radio object Teleios

Using the array of radio dishes dubbed the Australian Square Kilometre Array, astronomers have made the serendipitous discovery of what appears to be a perfect sphere of radio emissions tens of light years in diameter and tens of thousands of light years away and near the galactic center.

The scientists have dubbed the object Teleios, Greek for ‘complete’ or ‘perfect’. The image to the right is that radio image. Though the astronomers posit that it must have been formed from a supernova explosion, there are problems with that conclusion. From their paper [pdf]:

Unfortunately, all examined scenarios have their challenges, and no definitive Supernova origin type can be established at this stage. Remarkably, Teleios has retained its symmetrical shape as it aged even to such a diameter, suggesting expansion into a rarefied and isotropic ambient medium. The low radio surface brightness and the lack of pronounced polarisation can be explained by a high level of ambient rotation measure (RM), with the largest RM being observed at Teleios’s centre.

In other words, this object only emits in radio waves, is not visible in optical or other wavelengths as expected, and thus doesn’t really fit with any theories describing the evolution of supernova explosions. Yet its nature fits all other possible known space objects even less, such as planetary nebulae, nova remnants, Wolf-Rayet stars, or even super-bubbles of empty space (such as the Local Bubble the solar system is presently in).

Baffled, the scientists even considered the possibility that they had discovered an artificially built Dyson Sphere, but dismissed that idea because Teleios emits no infrared near its boundaries, as such a sphere is expected to do.

At present the best theory remains a supernova remnant, though this remains a poor solution at best.

Hat tip to reader (and my former editor at UPI) Phil Berardelli.

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Italy awards Italian company contract to design constellation of radio telescopes orbiting the Moon

8:45 am

Capitalism in space: The Italian Space Agency has awarded the Italian company Blue Skies Space a contract to design a constellation of radio telescopes orbiting the Moon and designed to map the universe’s earliest radio emissions.

The project, named RadioLuna, aims to uncover whether a fleet of small satellites in a lunar orbit could detect faint radio signals from the universe’s earliest days—signals that are nearly impossible to pick up on Earth due to man-made radio interference. These signals, in the FM radio range, come from a time before the first stars formed, when the universe was mostly hydrogen gas. By listening from the far side of the Moon, free from Earth’s radio noise, scientists could use the satellites to uncover a missing piece of the puzzle in our understanding of the cosmic “dark ages.”

The study will establish the viability of operating simple and cost-effective CubeSats equipped with commercial off-the-shelf (COTS) components orbiting the Moon and will be led by Blue Skies Space Italia S.r.l., a subsidiary of UK-based Blue Skies Space Ltd. Project partner OHB Italia will be responsible for the definition of a viable platform in a Moon orbit.

The contract is another example of Italy (and Europe) shifting to private enterprise in space. Rather than design this project in-house, its space agency is contracting it out to private companies.

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The uncertainty of science: New research suggests first image in ’22 of Milky Way’s central black hole is likely not accurate

10:25 am

Sagittarius A*
The original interpretation. Click for full image.

The new interpretaion
The new asymmetrical interpretation. Click for original image.

Surprise, surprise! A new analysis of the data behind the 2022 false-color radio image of the supermassive black hole at the center of the Milky Way, posted to the right, suggests that image was not accurately interpreted from the data.

Astronomers led by the National Astronomical Observatory of Japan (NAOJ) say their analysis points at Sagittarius A* having an elongated accretion disk, as opposed to the ring-like “doughnut” image released in 2022 by an international team called the Event Horizon Telescope (EHT) collaboration.

The EHT image shows a central dark region where the hole resides, circled by the light coming from super-heated gas accelerated by immense gravitational forces.

But a new paper published today in Monthly Notices of the Royal Astronomical Society suggests that part of this appearance may actually be an artefact because of the way the image was put together. … Assistant professor Miyoshi Makoto, of the NAOJ, said: “Our image is slightly elongated in the east-west direction, and the eastern half is brighter than the western half. We think this appearance means the accretion disk surrounding the black hole is rotating at about 60 per cent of the speed of light.” He added: “Why, then, did the ring-like image emerge? Well, no telescope can capture an astronomical image perfectly. We hypothesise that the ring image resulted from errors during EHT’s imaging analysis and that part of it was an artefact, rather than the actual astronomical structure.”

It must be noted that this false color radio image was assembled from eight different radio telescopes across the globe, and to bring the data together required a great deal of massaging. While most astronomers appear to favor the top picture, it is just as likely that the bottom picture is a better representation. Either way, both must be considered in any future studies of Sagittarius A*’s environment and structure.

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Using pulsars scientists detect background signal of the universe’s gravitational waves

10:07 am

The uncertainty of science: Using the variations in the precise radio pulses sent out by many pulsars over a fifteen year year astronomers think they have detected the background signal produced by many gravitational waves over time throughout the universe.

Astrophysicists using large radio telescopes to observe a collection of cosmic clocks in our Galaxy have found evidence for gravitational waves that oscillate with periods of years to decades, according to a set of papers published today in The Astrophysical Journal Letters. The gravitational-wave signal was observed in 15 years of data acquired by the North American Nanohertz Observatory for Gravitational Waves (NANOGrav) Physics Frontiers Center (PFC), a collaboration of more than 190 scientists from the US and Canada who use pulsars to search for gravitational waves. International collaborations using telescopes in Europe, India, Australia and China have independently reported similar results.

Imagine that each wave is a single wave on the ocean. This detection is the rough equivalent of looking at the ocean’s overall surface and measuring the general roughness of all the waves.

The press is making a big deal about this discovery. It is good science, and will over time provide valuable insights into evolution and merger of black holes, but it is not that big a deal, especially because this research carries with it many assumptions and uncertainties that good scientists recognize. They thus remain somewhat skeptical about the data. Mainstream journalists however consider gravitational waves cool, and so they hype any press release about them, sometimes to the point of absurdity.

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Astronomers discover 25 more repeating fast radio bursts, doubling the number known

10:18 am

Using a ground-based radio telescope in Canada that scans the northern sky each night, astronomers have discovered another 25 repeating fast radio bursts (FRBs), doubling the number that was previously known.

One surprising aspect of this new research is the discovery that many repeating FRBs are surprisingly inactive, producing under one burst per week during CHIME’s observing time. Pleunis believes that this could be because these FRBS haven’t yet been observed long enough for a second burst to be spotted.

The cause of FRBs still remains unsolved. The knowledge of specific repeating FRBs however will go a long way to figuring out this mystery, because other telescopes will be able to better observe later bursts, knowing when they are expected to occur.

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Astronomers form lobbying group to block development on Moon’s far side

9:14 am

Lunar zone reserved solely for astronomers
Lunar zone reserved exclusively for radio astronomers

In order to allow them to someday in the future maybe consider the idea of possibly building space-based radio telescopes on the Moon, astronomers have now formed a new lobbying group to advocate the creation of a zone more than a thousand miles wide on the Moon’s far side where all future development will be forbidden.

The new committee is chaired by Claudio Maccone, an Italian SETI (search for extraterrestrial intelligence) astronomer, space scientist and mathematician. Maccone supports creation of a Protected Antipode Circle or PAC, a large circular piece of lunar landscape about 1,130 miles (1,820 kilometers) wide that would become the most shielded area of the moon’s far side.

“PAC does not overlap with other areas of interest to human activity,” he said. “PAC is the only area of the far side that will never be reached by the radiation emitted by future space bases located at the L4 and L5 Lagrangian points of the Earth-moon system.”

In view of these unique features, Maccone believes the PAC should be officially recognized by the United Nations as an international protected area, where radio contamination by humans is curbed, now and into the future.

In other words, these astronomers want to be given, for free, full ownership of the region in the center circle on the graphic above for future radio telescopes, even though at present they have no plans or projects to build such things.

Though the idea of creating a region protected from radio signals so that good radio astronomy can be conducted has merit, no one should have the slightest sympathy for this request by astronomers. Why should anyone give them this vast amount of real estate when astronomers have shown so little interest in building any telescopes in space, anywhere?

Only after the astronomical community finally proposes an actual radio telescope for installation at this site should this request be given the slightest attention. Before that, it is merely a stupid power grab by elitists who deserve nothing from nobody.

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Radio astronomers claim negative impact from satellite constellations

10:35 am

Put them on the Moon! Radio astronomers have released a paper claiming that the coming large communication satellite constellations, such as Starlink and OneWeb, will seriously impact observations with the Square Kilometer Array (SKA) of radio telescopes being built in the remote western outback of Australia.

Saturation of the instruments: very strong interfering signals can saturate the receiver systems and thereby drown out all other signals seen by the Band 5b receivers. As a consequence, all data in that frequency band would be lost, rendering these receivers useless for a portion of the time. For the first phase of the constellation deployments (about 6,400 satellites in total), saturation is predicted to occur for a few percent of the time assuming there is no direct illumination of the dishes by the satellites. For significantly larger constellation sizes (up to more than 100,000 satellites), saturation would be essentially continuous without significant mitigation measures implemented by the satellite operators.

Based on this conclusion, the astronomers estimate that for observations in this particular band they will need to look about 70% longer to get the same data, thereby cutting the number of observations by about half.

The astronomers propose this solution:

One of these mitigation techniques is for the satellite transmitters not to point their beams near the SKAO dishes. SKAO would require operators to steer their satellites’ beams away from the telescope site, a measure which would require a simple software modification with no repercussion on the constellation’s deployment, positioning or hardware. While a cost-effective implementation of this solution does depend on the hardware and software deployed on the satellites, operators already use this technique to comply with international regulations when their satellites cross the path between geostationary satellites in higher orbit and their receiving ground stations, for example to avoid affecting telecommunications and TV transmissions.

This mitigation could reduce the impact on the SKA by a factor of 10 over that noted previously and result in a 7% increase of integration time for SKA observations within the satellite transmission range 4. While any loss of sensitivity is regrettable, SKAO recognises the need for compromise between the competing scientific and commercial drivers.

The solution seems reasonable, but in truth it is only a temporary one. The permanent and smart solution for the astronomical community is to move their telescopes, in all wavelengths, off the Earth. For radio astronomy the far side of the Moon would be ideal.

And with SpaceX now developing a reusable big rocket, Starship, to put such payloads in orbit at low cost, the astronomers need to start thinking about taking advantage of this engineering. The situation for ground-based astronomer will only get worse.

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The magnetic field of a spiral galaxy

9:05 am

Magnetic field of a spiral galaxy
Click for full image.

Using a variety of telescopes, especially the Jansky Very Large Array radio telescope, astronomers have successfully mapped the magnetic field lines of a spiral galaxy seen edge on and 67 million light years away.

The image to the right, cropped and reduced to post here, shows what they have found.

The magnetic field lines extend as much as 22,500 light-years beyond the galaxy’s disk. Scientists know that magnetic fields play an important role in many processes, such as star formation, within galaxies. However, it is not fully understood how such huge magnetic fields are generated and maintained. A leading explanation, called the dynamo theory, suggests that magnetic fields are generated by the motion of plasma within the galaxy’s disk. Ideas about the cause of the kinds of large vertical extensions seen in this image are more speculative, and astronomers hope that further observations and more analysis will answer some of the outstanding questions.

Our understanding of these kinds of gigantic magnetic fields is poor, to put it mildly. This data really only begins the research.

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China’s FAST radio telescope discovers 93 new pulsars

9:53 am

The research team running China’s FAST radio telescope, the largest single dish such telescope in the world, have announced that they have discovered 93 new pulsars since October 2017.

China might still be having trouble finding a big name astronomer to run the telescope, but in the meantime it looks like their own people are taking advantage of the situation to use the telescope establish their own names.

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Arecibo gets $12.3 million NSF grant

8:40 am

The National Science Foundation has awarded the Arecibo radio telescope in Puerto Rica a $12.3 million grant to pay for needed repairs and upgrades following the hurricane damage from 2017.

The money will pay for the following work:

  • Repairing one of the suspension cables holding the primary telescope platform, ensuring long-term structural integrity of one of the main structural elements of the telescope.
  • Recalibrating the primary reflector, which will restore the observatory’s sensitivity at higher frequencies.
  • Aligning the Gregorian Reflector, improving current calibration and pointing.
  • Installing a new control system for S band radar, which is part of the microwave band of the electromagnetic spectrum.
  • Replacing the modulator on the 430 MHz transmitter, increasing consistency of power output and data quality.
  • Improving the telescope’s pointing controls and data tracking systems.

Most of this looks to be very basic maintenance, which suggests the telescope is still very starved for funds.

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Fast radio bursts not detected at certain radio wavelengths

8:47 am

In observations by two different radio telescopes operating at different radio wavelengths but looking at the same part of the sky, astronomers have found that an observed fast radio burst was not detected by one of those telescopes.

The Curtin University-led Murchison Widefield Array (MWA) and CSIRO’s Australian SKA Pathfinder (ASKAP) telescopes were searching the sky for fast radio bursts, which are exceptionally bright flashes of energy coming from deep space. These extreme events last for only a millisecond but are so bright that many astronomers initially dismissed the first recorded fast radio burst as an observational error.

In research published in the Astrophysical Journal Letters, astronomers describe how ASKAP detected several extremely bright fast radio bursts, but the MWA—which scans the sky at lower frequencies—did not see anything, even though it was pointed at the same area of sky at the same time.

Lead author Dr Marcin Sokolowski, from the Curtin University node of the International Centre for Radio Astronomy Research (ICRAR), said the fact that the fast radio bursts were not observed at lower frequencies was highly significant. “When ASKAP sees these extremely bright events and the MWA doesn’t, that tells us something really unexpected is going on; either fast radio burst sources don’t emit at low frequencies, or the signals are blocked on their way to Earth,” Dr Sokolowski said.

If blocked at these lower frequencies, this tells theorists something about the environment where the burst occurred. If instead the burst does not emit in those lower frequencies, it tells them something about the burst itself.

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Radio telescope in Greenland sees first “light”

10:03 am

Astronomers have successfully initiated operations of a new radio telescope dish, the first ever located in Greenland.

The Greenland Telescope is a 12-meter radio antenna that was originally built as a prototype for the Atacama Large Millimeter/submillimeter Array (ALMA) North America. Once ALMA was operational in Chile, the telescope was repurposed to Greenland to take advantage of the near-ideal conditions of the Arctic to study the Universe at specific radio frequencies, collaborating with the National Radio Astronomy Observatory (NRAO) and MIT Haystack Observatory.

ASIAA led the effort to refurbish and rebuild the antenna to prepare it for the cold climate of Greenland’s ice sheet. In 2016, the telescope was shipped to the Thule Air Base in Greenland, 1,200 km inside the Arctic Circle, where it was reassembled at this coastal site. ASIAA also built receivers for the antenna. “It is extremely challenging to quickly and successfully set up a new telescope in such a cold environment, where temperatures fall below -30 degrees Celsius,” said Ming-Tang Chen from ASIAA and the Greenland Telescope project manager. “This is now one of the closest radio telescopes to the North Pole.”

They have also linked this radio telescope to others across the globe, helping to increase the resolution of any data these radio telescopes gather as a unit.

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First results from Breakthrough Listen’s search for alien radio signals

3:44 pm

Breakthrough Listen has released its first results from its search for extraterrestrial radio signals using the Greenbank Observatory in West Virginia.

Breakthrough Listen – the initiative to find signs of intelligent life in the universe – has released its 11 events ranked highest for significance as well as summary data analysis results. It is considered unlikely that any of these signals originate from artificial extraterrestrial sources, but the search continues. Further, Listen has submitted for publication (available April 20) in a leading astrophysics journal the analysis of 692 stars, comprising all spectral types, observed during its first year of observations with the Green Bank Telescope.

The press release tries to make a big deal about this data, but essentially what it boils down to is that so far they have found nothing that could indicate artificial radio signals coming from any of these stars.

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The National Radio Astronomy Observatory (NRAO) has renamed the thirty-one year old Very Large Array (VLA) after Karl Jansky, the man who invented radio astronomy.

10:16 pm

A fitting honor: The National Radio Astronomy Observatory (NRAO) has renamed the recently upgraded thirty-one year old Very Large Array (VLA) after Karl Jansky, the man who invented radio astronomy.

Karl Guthe Jansky joined Bell Telephone Laboratories in New Jersey in 1928, immediately after receiving his undergraduate degree in physics. He was assigned the task of studying radio waves that interfered with the recently-opened transatlantic radiotelephone service. After designing and building advanced, specialized equipment, he made observations over the entire year of 1932 that allowed him to identify thunderstorms as major sources of radio interference, along with a much weaker, unidentified radio source. Careful study of this “strange hiss-type static” led to the conclusion that the radio waves originated from beyond our Solar System, and indeed came from the center of our Milky Way Galaxy.

His discovery was reported on the front page of the New York Times on May 5, 1933, and published in professional journals. Jansky thus opened an entirely new “window” on the Universe. Astronomers previously had been confined to observing those wavelengths of light that our eyes can see. “This discovery was like suddenly being able to see green light for the first time when we could only see blue before,” said Lo.

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