How do stars stay young?

The secret of young stars

Stars with planets continue to glow in X-rays, a sign that the star is young.

A hot Jupiter planet orbiting a star in a binary system.

(Image credit: NASA/CXC/M.Weiss)

Planets and stars are like parent and child, a new study suggests: The smaller bodies keep the larger ones active, which helps them stay young longer.

The study looked at several stars that are what astronomers call hot Jupiters, giant gas worlds about the size of our solar system's largest planet, Jupiter. Hot Jupiters orbit very close to their parent stars -- closer than our solar system's innermost planet, Mercury, orbits the sun. But because they are so large, the gravity of hot Jupiters tugs on the stars they orbit, causing them to spin faster. This extra motion causes the stars to crackle in X-rays, which is common for young, adult stars.

Scientists had seen hints of this phenomenon before, but were reluctant to draw any conclusions until they could observe it in a sufficient number of stellar parents and their hot Jupiter offspring. They have now managed to collect a satisfactory sample, thanks to observations by NASA's Chandra X-ray Observatory and the agency's XMM-Newton spacecraft.

"In medicine, you need a lot of patients in a study to know if the effects are real or just some kind of anomaly," lead author Nicoleta Ilic, an astronomer at the Leibniz Institute for Astrophysics in Potsdam, Germany, said in a NASA statement. "The same is true in astronomy, and this study gives us confidence that these hot Jupiters really make the stars they orbit younger than they really are."

Just like aging humans, stars tend to slow down as they age. They spin more slowly and flash less. But since stars don't have birth certificates to prove their age, Ilich and her colleagues had to find a more subtle way to show the effect of planet rejuvenation. They looked at binary stars, which orbit each other and formed at the same time, like human twins. The researchers looked for pairs of stars in which only one of the stars had hot Jupiter planets in orbit.

"It's almost like using twins in a study where one twin lives in a completely different neighborhood and this affects their health," co-author Katya Popensinger of the Institute of Physics said in the statement. "By comparing a star with a nearby planet to a twin without one, we can study how stars of the same age behave."

By looking at X-ray measurements, the researchers were able to clearly see that stars with planets give off more X-ray bursts than their childless siblings, a typical signature of young stars. The researchers observed this effect consistently in more than 30 pairs of stars, the researchers said in the statement. The final sample included 10 binary systems observed by Chandra and six by XMM-Newton.

Related knowledge

The Solar System is the gravitational system of the Sun and the objects that orbit it. It formed 4.6 billion years ago from the gravitational collapse of a large interstellar molecular cloud. The vast majority of the system's mass is in the Sun, with most of the remaining mass in Jupiter. The Solar System is the gravitationally bound system of the Sun and the objects that orbit it. It formed 4.6 billion years ago from the gravitational collapse of a large interstellar molecular cloud. The vast majority of the system's mass is in the Sun, with most of the remaining mass in Jupiter. The four inner planets, Mercury, Venus, Earth, and Mars, are terrestrial planets, composed mostly of rock and metal. The four giant planets in the outer system are much larger and more massive than Earth. Jupiter and Saturn are the two largest gas giants, composed mostly of hydrogen and helium; the next two, Uranus and Neptune, are ice giants, composed mostly of volatile substances that have relatively high melting points compared to hydrogen and helium, such as water, ammonia, and methane. The orbits of the eight planets are all nearly circular and lie near the plane of Earth's orbit, called the ecliptic.

A binary star is a system of two stars that are gravitationally bound together and orbit each other. Binary stars in the night sky that appear as a single object to the naked eye are usually resolved as separate stars with a telescope, in which case they are called visual binaries. Many visible binaries have orbital periods of hundreds or thousands of years, so their orbits are uncertain or poorly known. They can also be detected by indirect techniques, such as spectroscopy (spectroscopic binaries) or astrometry (astrometric binaries). If a binary star happens to orbit in a plane across our line of sight, its components can eclipse and transit each other; these binaries are called eclipsing binaries, or, along with other binaries that change brightness as they orbit, are called photometric binaries.

BY:Tereza Pultarova

FY: Free Addiction Girl

If there is any infringement of related content, please contact the author to delete it after the work is published.

Please obtain authorization for reprinting, and pay attention to maintaining integrity and indicating the source