Month: October 2024

Remember the amazing “first image” of the Sagittarius A* (Sgr A) black hole at the heart of the Milky Way? It may not be entirely accurate, according to researchers at the National Astronomical Observatory of Japan (NAOJ). Instead, the accretion disk around Sgr A* may be more elongated than the circular shape we first saw in 2022.

Scientists at NAOJ applied various analysis methods to the Sgr A* data first captured by the Event Horizon Telescope (EHT) team. The EHT data came from a network of eight ground-based radio telescopes. The original analysis showed a bright ring structure surrounding a dark central region. The reanalysis, which results in a different shape, reveals something about the movements and distribution of matter in the disk.

To be fair to both teams, analyzing radio interferometry data is notoriously complex. According to NAOJ astronomer Miyoshi Mikato, the rounded appearance could be due to the way the image was created. “We suspect that the ring image was due to errors in EHT's image analysis and that part of it was an artifact rather than the actual astronomical structure,” Miyoshi suggested.

This is the first image of Sgr A*, the supermassive black hole at the center of our galaxy. A reanalysis of the EHT data by NAOJ scientists suggests that the accretion disk may be elongated rather than circular. Photo credit: EHT

Explaining the appearance of a black hole

What does Sgr A* look like in the NAOJ reanalysis? “Our image is slightly elongated in the east-west direction and the eastern half is brighter than the western half,” Miyoshi said. “We think this phenomenon means that the accretion disk surrounding the black hole is rotating at about 60 percent of the speed of light.”

The accretion disk is filled with superheated material that “circles the drain,” so to speak. It flows into the black hole with a mass of 4 million solar masses. As it passes through the accretion disk, the material is heated by friction and the effect of magnetic fields. This means that it shines primarily in X-ray and visible light and also emits radio emissions.

Various factors also influence the shape of the accretion disk, including the spin of the black hole itself. In addition, the accretion rate (i.e. how much material falls into the disk) as well as the angular momentum of the material influence the shape. The black hole's gravitational pull also distorts our view of the accretion disk. This type of “funhouse mirror” distortion makes it incredibly difficult to image. As it turns out, either view of the disk's actual shape – the original “circular” EHT view or the extended NAOJ view – could be correct.

So why the different views of the black hole?

How did the teams arrive at two slightly different views of Sgr A* using the same data? “No telescope can capture an astronomical image perfectly,” emphasized Miyoshi. The EHT observations show that interferometric data from the widely networked telescopes can have gaps. When analyzing data, scientists must use specialized techniques to create a complete picture. This is what the EHT team did and this is how the image of the “round black hole” was created.

Miyoshi's team published a paper describing their findings. In it, they suggest that the “ring” structure in the 2022 image released by EHT is an artifact caused by the bumpy point spread function (PSF) of the EHT data. The PSF describes how an imaging system handles a point source in the region under consideration. It helps determine the amount of blur that occurs due to imperfections in the optics (or in this case the gaps in the interferometric data). In other words, there were problems “filling” the gaps.

The NAOJ team reanalyzed the data and used a different mapping method to compensate for the gaps in the data. This resulted in an elongated shape of the Sgr A* accretion disk. One half of the disk is brighter and they suspect this is due to Doppler enhancement as the disk is spinning rapidly. They suggest that the reanalyzed data and the extended image show a portion of the disk located a few Schwarzschild radii from the black hole, rotating extremely quickly and viewed from an angle of 40° to 45°.

What's next?

This re-analysis is intended to provide a better understanding of what the Sgr A* accretion disk actually looks like. The EHT study of Sgr A*, which led to the image release in 2022, was the first detailed attempt to map the region around the black hole. The EHT consortium is working on improvements to produce better and more detailed interferometry images of this and other black holes. Ultimately this should lead to more accurate views. Follow-up studies should help close any gaps in the observations of the accretion disk. In addition, detailed studies of the black hole's immediate surroundings should provide further clues about the black hole hidden in the disk. I

More information

First image of black hole in Milky Way may not be accurate
An independent hybrid imaging of Sgr A* from the EHT 2017 observation data

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By Nate Scherer

The fight against climate change is increasingly characterized by feel-good attempts by lawmakers to save the planet by issuing top-down regulations that do nothing to meaningfully lower global temperatures or reduce pollution. However, these “feel-good” regulations have a well-known habit of harming consumers by eliminating popular goods and services or making them more expensive.

The most recent example of such a regulation comes from California, where lawmakers recently passed a second ban on plastic grocery bags after the first attempt failed. The first ban, SB 270, which took effect in 2014, banned grocery stores from handing out single-use plastic bags at checkout. It was designed to reduce plastic waste and encourage consumers to use reusable bags.

However, a recent study published by California consumer advocacy group CALPIRG found that the ban may have inadvertently led to a 47% increase in plastic bag waste between 2014 and 2022, as consumers tend to throw away thicker reusable plastic bags after a single use. That means SB 270 didn't reduce plastic waste, but rather produced more of it, while simultaneously charging consumers 10 cents per reusable bag. Plastic bag bans in other states have produced similar results, such as in New Jersey, which found that plastic consumption tripled after the ban went into effect.

While California politicians now hope to close this glaring loophole by banning grocery stores from selling thicker plastic bags and requiring them to offer only recycled paper bags at checkout, it's not hard to imagine other unintended consequences. Policymakers attempt to control consumers' subjective behavior and preferences – a strategy that rarely, if ever, works.

Other notable examples of failures in environmental regulations include bans on plastic straws. Motivated by clichéd slogans like “The Last Plastic Straw Campaign,” which rely on viral turtle videos to garner public support, policymakers in states and cities across the country have enacted bans on plastic straws. Proponents argue that such bans reduce plastic waste – some of which ends up in rivers and landfills – while encouraging consumers to use reusable or paper straws. However, the success of such bans is questionable at best, as plastic straws make up a negligible proportion of plastic waste. In addition, supposedly green alternatives such as paper straws have been found to pose their own environmental problems, for example because they consist of large amounts of water-resistant chemicals that are slow to biodegrade.

Bans on gas appliances also appear to be a fan favorite of policymakers who see connecting natural gas and fossil fuels as antithetical to a carbon-free future. Cities such as Los Angeles, Seattle and San Francisco have recently implemented such bans on new construction, as has New York state. While policymakers say such bans are necessary to curb greenhouse gas emissions, they require residents to make unnecessary sacrifices, such as using less popular appliances like gas stoves that heat up more slowly, allow for less precise temperature control and often impose higher monthly bills pull yourself.

It's also worth noting that eliminating gas appliances has little impact on reducing carbon emissions if the city or state gets its electricity from oil or natural gas. According to the U.S. Energy Information Administration, 60% of U.S. electricity generation still comes from fossil fuels, and no state relies entirely on renewable energy. Likewise, most large population centers rely on many different forms of energy to meet their needs. Bans on gas appliances, straws and plastic bags will not change consumer preferences, but they will take away their choice.

There are countless other feel-good attempts at environmental regulation by policymakers seeking to combat climate change, and many exact a similar toll on consumers, be it water-saving faucet requirements that reduce flow rates, bans on light bulbs, or restrictions on the type of garden a homeowner can have can have. While not all such regulations are bad or overly burdensome, they add up quickly and have the cumulative effect of restricting people's freedom to choose which good or service is best for them. While some Americans see these limits as a necessary sacrifice to help save the planet, chances are most would not feel that way if they knew that few would make a meaningful contribution to mitigating climate change or reducing waste .

Nate Scherer is a policy analyst at the American Consumer Institute, a nonprofit education and research organization. For more information about the Institute, visit us at www.TheAmericanConsumer.Org or follow us on X @ConsumerPal

This article was originally published by RealClearEnergy and made available via RealClearWire.

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