REPUBLIKA.CO.ID, JAKARTA— Measuring age planet and stars help scientists understand when they form and how they change. In the case of planets, does life have time to evolve on them.
Unfortunately, the age of objects in space is difficult to measure. Stars like the sun maintain the same brightness, temperature and size for billions of years. Planetary properties such as temperature are often determined by the stars they orbit, not by their own age and evolution.
Fortunately, stars’ brightness and color change subtly over time. Reported SpaceTuesday (10/10/2023), Adam Burgasser, professor of astronomy & astrophysics at UC San Diego, and an observational astrophysicist who investigates the coolest stars, brown dwarfs, and extrasolar planets, wrote with very accurate measurements, the astronomer can compare measurements of a star with mathematical models that predict what happens to a star as it ages and estimate its age from there.
Stars not only shine, but also rotate. Over time, its rotation slows, similar to how a wheel slows down when it encounters friction. By comparing the rotation speeds of stars of different ages, astronomers have been able to create a mathematical relationship for the ages of stars. This method is known as gyrochronology.
The star’s spin also generates strong magnetic fields and produces magnetic activity, such as stellar flares—powerful bursts of energy and light that occur on the surface of a star. A star’s steady decline in magnetic activity can also help estimate its age.
A more sophisticated method for determining star age called asteroseismology, or star shaking. Astronomers study vibrations on a star’s surface caused by waves traveling through its interior.
Young stars have different vibration patterns than old stars. Using this method, astronomers estimate the age of the sun to be 4.58 billion years.
Meanwhile, Burgasser also wrote that in the solar system, radionuclides are the key to determining the age of planets. These are special atoms that release energy slowly over a long period of time. As natural clocks, radionuclides help scientists determine the age of all kinds of objects, from rocks to bones and pottery.
Using this method, scientists have determined that the oldest known meteorite is 4.57 billion years old, nearly identical to the Sun’s asteroseismological measurement of 4.58 billion years old. The oldest known rocks on Earth are slightly younger at 4.40 billion years old. Likewise, soil brought back from the Moon during the Apollo missions has a radionuclide age of up to 4.6 billion years.
While studying radionuclides is a powerful method for measuring the age of a planet, this usually requires having a rock on hand. Usually, astronomers only have an image of a planet to look at. Astronomers often determine the age of rocky celestial bodies such as Mars or the moon by counting their craters.
Older surfaces have more craters than younger surfaces. However, erosion caused by water, wind, cosmic rays, and lava flows from volcanoes can erase evidence of previous impacts.
Aging techniques don’t work for giant planets like Jupiter whose surfaces are deeply buried. However, astronomers can estimate their ages by counting craters on their moons or studying the distribution of certain classes of scattered meteorites, which is consistent with radionuclide methods and cratering on rocky planets. We cannot yet directly measure the ages of planets in the outer space of the solar system us with today’s technology.
The question is how accurate are these estimates? Our solar system provides the best check for accuracy, because astronomers can compare the radionuclide ages of rocks on Earth, the moon, or asteroids with the asteroseismological ages of the sun, and the two agree very well.
Stars in clusters such as the Pleiades or Omega Centauri are believed to have formed at about the same time, so the estimated age of each star in the cluster should be the same. For some stars, astronomers can detect radionuclides such as uranium—a heavy metal found in rocks and soil—in their atmospheres, which have been used to check their age through other methods.
Astronomers believe that planetary age is roughly the same as its host star, so improved methods for determining the age of stars also help determine the age of planets. By studying subtle clues, we can make an educated guess about a star’s steadfast age.
2023-10-09 22:06:26
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