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How do we know the age of the planets and stars? – Swara D., age 13, Thane, India

Measuring the ages of planets and stars helps scientists understand when they formed and how they change – and, in the case of planets, if life has had time to have evolved on them.

Unfortunately, age is hard to measure for objects in space.

Stars like the Sun maintain the same brightness, temperature and size for billions of years. Planet properties like temperature are often set by the star they orbit rather than their own age and evolution.

Determining the age of a star or planet can be as hard as guessing the age of a person who looks exactly the same from childhood to retirement.

Sussing out a star’s age

Fortunately, stars change subtly in brightness and color over time. With very accurate measurements, astronomers can compare these measurements of a star to mathematical models that predict what happens to stars as they get older and estimate an age from there.

Stars don’t just glow, they also spin. Over time, their spinning slows down, similar to how a spinning wheel slows down when it encounters friction. By comparing the spin speeds of stars of different ages, astronomers have been able to create mathematical relationships for the ages of stars, a method known as gyrochronology.

A star’s spin also generates a strong magnetic field and produces magnetic activity, such as stellar flares – powerful bursts of energy and light that occur on stars’ surfaces. A steady decline in magnetic activity from a star can also help estimate its age.

A more advanced method for determining the ages of stars is called asteroseismology, or star shaking. Astronomers study vibrations on the surfaces of stars caused by waves that travel through their interiors. Young stars have different vibrational patterns than old stars. By using this method, astronomers have estimated the Sun to be 4.58 billion years old.

Piecing together a planet’s age

In the solar system, radionuclides are the key to dating planets. These are special atoms that slowly release energy over a long period of time. As natural clocks, radionuclides help scientists determine the ages of all kinds of things, from rocks to bones and pottery.

Using this method, scientists have determined that the oldest known meteorite is 4.57 billion years old, almost identical to the Sun’s asteroseismology measurement of 4.58 billion years. The oldest known rocks on Earth have slightly younger ages of 4.40 billion years. Similarly, soil brought back from the Moon during the Apollo missions had radionuclide ages of up to 4.6 billion years.

Although studying radionuclides is a powerful method for measuring the ages of planets, it usually requires having a rock in hand. Typically, astronomers only have a picture of a planet to go by. Astronomers often determine the ages of rocky space objects like Mars or the Moon by counting their craters. Older surfaces have more craters than younger surfaces. However, erosion from water, wind, cosmic rays and lava flow from volcanoes can wipe away evidence of earlier impacts.

Aging techniques don’t work for giant planets like Jupiter that have deeply buried surfaces. However, astronomers can estimate their ages by counting craters on their moons or studying the distribution of certain classes of meteorites scattered by them, which are consistent with radionuclide and cratering methods for rocky planets.

We cannot yet directly measure the ages of planets outside our solar system with current technology.

How accurate are these estimates?

Our own solar system provides the best check for accuracy, since astronomers can compare the radionuclide ages of rocks on the Earth, Moon, or asteroids to the asteroseismology age of the Sun, and these match very well.

Stars in clusters like the Pleiades or Omega Centauri are believed to have all formed at roughly the same time, so age estimates for individual stars in these clusters should be the same. In some stars, astronomers can detect radionuclides like uranium – a heavy metal found in rocks and soil – in their atmospheres, which have been used to check the ages from other methods.

Astronomers believe planets are roughly the same age as their host stars, so improving methods to determine a star’s age helps determine a planet’s age as well. By studying subtle clues, it’s possible to make an educated guess of the age of an otherwise steadfast star.

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Adam Burgasser, Professor of Astronomy & Astrophysics, University of California, San Diego

This article is republished from The Conversation under a Creative Commons license. Read the original article.

As the U.S. shifts away from fossil fuels to cleaner energy sources, thousands of coal, oil and gas workers will be looking for new jobs.

Many will have the skills to step into new jobs in the emerging clean energy industries, but the transition may not be as simple as it seems. New research published in the journal Nature Communications identifies a major barrier that is often overlooked in discussions of how to create a just transition for these workers: location.

We analyzed 14 years of fossil fuel employment and skills data and found that, while many fossil fuel workers could transfer their skills to green jobs, they historically have not relocated far when they changed jobs.

That suggests that it’s not enough to create green industry jobs. The jobs will have to be where the workers are, and most fossil fuel extraction workers are not in regions where green jobs are expected to grow.

Without careful planning and targeted policies, we estimate that only about 2% of fossil fuel workers involved in extraction are likely to transition to green jobs this decade. Fortunately, there are ways to help smooth the transition.

Many fossil fuel and green skills overlap

As of 2019, about 1.7 million people worked in jobs across the fossil fuels industry in the U.S., many of them in the regions from Texas and New Mexico to Montana and from Kentucky to Pennsylvania. As the country transitions from fossil fuel use to clean energy to protect the climate, many of those jobs will disappear.

Policymakers tend to focus on skills training when they talk about the importance of a just transition for these workers and their communities.

To see how fossil fuel workers’ skills might transfer to green jobs, we used occupation and skills data from the U.S. Bureau of Labor Statistics to compare them. These profiles provide information about the required workplace skills for over 750 occupations, including earth drillers, underground mining machine operators and other extraction occupations.

Overall, we found that many fossil fuel workers involved in extraction already have similar skills to those required in green occupations, as previous studies also found. In fact, their skills tend to be more closely matched to green industries than most other industries.

Job-to-job flow data from the U.S. Census Bureau showed that these workers historically tend to transition to other sectors with similar skills requirements. Thus, fossil fuel workers should be able to fill emerging green jobs with only minimal reskilling.

However, the data also shows that these fossil fuel workers typically do not travel far to fill employment opportunities.

The location problem

When we mapped the current locations of wind, solar, hydro and geothermal power plants using data from the U.S. Energy Information Administration, we found that these sites had little overlap with fossil fuel workers.

The U.S. Bureau of Labor Statistics’ projections for where green jobs are likely to emerge by 2029 also showed little overlap with the locations of today’s fossil fuel workers.

These results were consistent across several green employment projections and different definitions of “fossil fuel” occupations. That’s alarming for the prospects of a just transition.

How policymakers can intervene

Broadly, our findings point to two potential strategies for policymakers.

First, policymakers can explore incentives and programs that help fossil fuel workers relocate. However, as our analysis reveals, these populations have not historically exhibited geographic mobility.

Alternatively, policymakers could design incentives for green industry employers to build in fossil fuel communities. This might not be so simple. Green energy production often depends on where the wind blows strongest, solar power production is most effective and geothermal power or hydropower is available.

We simulated the creation of new green industry employment in two different ways, one targeting fossil fuel communities and the other spread uniformly across the U.S. according to population. The targeted efforts led to significantly more transitions from fossil fuel to green jobs. For example, we found that creating 1 million location-targeted jobs produced more transitions than the creation of 5 million jobs that don’t take workers’ locations into account.

Another solution doesn’t involve green jobs at all. A similar analysis in our study of other existing U.S. sectors revealed that construction and manufacturing employment are already co-located with fossil fuel workers and would require only limited reskilling. Supporting manufacturing expansion in these areas could be a simpler solution that could limit the number of new employers needed to support a just transition.

There are other questions that worry fossil fuel workers, such as whether new jobs will pay as well and last beyond construction. More research is needed to assess effective policy interventions, but overall our study highlights the need for a comprehensive approach to a just transition that takes into account the unique challenges faced by fossil fuel workers in different regions.

By responding to these barriers, the U.S. can help ensure that the transition to a green economy is not only environmentally sustainable but also socially just.

Morgan R. Frank, Assistant Professor of Informatics, University of Pittsburgh and Junghyun Lim, Assistant Professor of Political Science, University of North Carolina at Chapel Hill

This article is republished from The Conversation under a Creative Commons license. Read the original article.

Between the record-breaking global heat and extreme downpours, it’s hard to ignore that something unusual is going on with the weather in 2023.

People have been quick to blame climate change – and they’re right: human-caused global warming plays the biggest role. The weekslong heat wave that started in June 2023 in Texas, the U.S. Southwest and Mexico would have been virtually impossible without it, one study found.

However, the extremes this year are sharper than anthropogenic global warming alone would be expected to cause. September temperatures were far above any previous September, and around 3.1 degrees Fahrenheit (1.75 degrees Celsius) above the preindustrial average, according to the European Union’s earth observation program.

July was Earth’s hottest month on record, also by a large margin, with average global temperatures more than half a degree Fahrenheit (a third of a degree Celsius) above the previous record, set just a few years earlier in 2019.

Human activities have been increasing temperatures at an average of about 0.2 F (0.1 C) per decade. But this year, three additional natural factors are also helping drive up global temperatures and fuel disasters: El Niño, solar fluctuations and a massive underwater volcanic eruption.

Unfortunately, these factors are combining in a way that is exacerbating global warming. Still worse, we can expect unusually high temperatures to continue, which means even more extreme weather in the near future.

How El Niño is involved

El Niño is a climate phenomenon that occurs every few years when surface water in the tropical Pacific reverses direction and heats up. That warms the atmosphere above, which influences temperatures and weather patterns around the globe.

Essentially, the atmosphere borrows heat out of the Pacific, and global temperatures increase slightly. This happened in 2016, the time of the last strong El Niño. Global temperatures increased by about 0.25 F (0.14 C) on average, making 2016 the warmest year on record. A weak El Niño also occurred in 2019-2020, contributing to 2020 becoming the world’s second-warmest year.

El Niño’s opposite, La Niña, involves cooler-than-usual Pacific currents flowing westward, absorbing heat out of the atmosphere, which cools the globe. The world just came out of three straight years of La Niña, meaning we’re experiencing an even greater temperature swing.

Based on increasing Pacific sea surface temperatures in mid-2023, climate modeling now suggests a 90% chance that Earth is headed toward its first strong El Niño since 2016.

Combined with the steady human-induced warming, Earth may soon again be breaking its annual temperature records. June 2023 was the hottest in modern record. July saw global records for the hottest days and a large number of regional records, including an incomprehensible heat index of 152 F (67 C) in Iran.

Solar fluctuations

The Sun may seem to shine at a constant rate, but it is a seething, churning ball of plasma whose radiating energy changes over many different time scales.

The Sun is slowly heating up and in half a billion years will boil away Earth’s oceans. On human time scales, however, the Sun’s energy output varies only slightly, about 1 part in 1,000, over a repeating 11-year cycle. The peaks of this cycle are too small for us to notice at a daily level, but they affect Earth’s climate systems.

Rapid convection within the Sun both generates a strong magnetic field aligned with its spin axis and causes this field to fully flip and reverse every 11 years. This is what causes the 11-year cycle in emitted solar radiation.

Earth’s temperature increase during a solar maximum, compared with average solar output, is only about 0.09 F (0.05 C), roughly a third of a large El Niño. The opposite happens during a solar minimum. However, unlike the variable and unpredictable El Niño changes, the 11-year solar cycle is comparatively regular, consistent and predictable.

The last solar cycle hit its minimum in 2020, reducing the effect of the modest 2020 El Niño. The current solar cycle has already surpassed the peak of the relatively weak previous cycle (which was in 2014) and will peak in 2025, with the Sun’s energy output increasing until then.

A massive volcanic eruption

Volcanic eruptions can also significantly affect global climates. They usually do this by lowering global temperatures when erupted sulfate aerosols shield and block a portion of incoming sunlight – but not always.

In an unusual twist, the largest volcanic eruption of the 21st century so far, the 2022 eruption of Tonga’s Hunga Tonga-Hunga Ha’apai, is having a warming and not cooling effect.

The eruption released an unusually small amount of cooling sulfate aerosols but an enormous amount of water vapor. The molten magma exploded underwater, vaporizing a huge volume of ocean water that erupted like a geyser high into the atmosphere.

Water vapor is a powerful greenhouse gas, and the eruption may end up warming Earth’s surface by about 0.06 F (0.035 C), according to one estimate. Unlike the cooling sulfate aerosols, which are actually tiny droplets of sulfuric acid that fall out of the atmosphere within one to two years, water vapor is a gas that can stay in the atmosphere for many years. The warming impact of the Tonga volcano is expected to last for at least five years.

Underlying it all: Global warming

All of this comes on top of anthropogenic, or human-caused, global warming.

Humans have raised global average temperatures by about 2 F (1.1 C) since 1900 by releasing large volumes of greenhouse gases, particularly carbon dioxide, into the atmosphere. The amount of carbon dioxide in the atmosphere is up 50%, primarily from the combustion of fossil fuels in vehicles and power plants. The warming from greenhouse gases is actually greater than 2 F (1.1 C), but it has been masked by other human factors that have a cooling effect, such as air pollution.

If human impacts were the only factors, each successive year would set a new record as the hottest year ever, but that doesn’t happen. The year 2016 was the warmest in part because temperatures were boosted by the last large El Niño.

What does this mean for the future?

The next couple of years could be very rough.

If a strong El Niño develops over the coming months as forecasters expect, combined with the solar maximum and the effects of the Hunga Tonga-Hunga Ha’apai eruption, Earth’s temperatures will likely continue to soar.

As temperatures continue to increase, weather events get more extreme. The excess heat can mean more heat waves, forest fires, flash floods and other extreme events, climate models show.

In January 2023, scientists wrote that Earth’s temperature had a greater than 50% chance of reaching 2.7 F (1.5 C) above preindustrial era temperatures by the year 2028, at least temporarily, increasing the risk of triggering climate tipping points with even greater human impacts. Because of the unfortunate timing of several parts of the climate system, it seems the odds are not in our favor.

This article, originally published July 27, 2023, has been updated with September’s record heat.

Michael Wysession, Professor of Earth, Environmental, and Planetary Sciences, Arts & Sciences at Washington University in St. Louis

This article is republished from The Conversation under a Creative Commons license. Read the original article.