For the first time, astronomers detect regular pulses from chaotic stars

A class of stars emitting discordant frequencies across the galaxy has been unraveled. Using data collected by NASA's TESS space telescope, astronomers finally found a rhythm in the pulsations of strange young stars.

They are called variable stars delta Scutiand rotate so fast that the stars flatten slightly, stirring their patterns of pulsation and producing what appears to be chaos.

From this chaos, we now have order: regular high-frequency pulsation modes identified in 60 stars of the Scuti Delta of intermediate mass, varying from 1.5 to 2.5 times the mass of the Sun.

"The Delta Scuti stars clearly pulsate in an interesting way, but the patterns of these pulses have so far defied understanding." said astronomer Tim Bedding of the University of Sydney in Australia.

"To use a musical analogy, many stars pulse along simple chords, but the stars in the Scuti Delta are complex, with notes that seem to be mixed. TESS has shown us that this is not true for all. "

Stellar pulses are not an unusual phenomenon. Lots of stars maybe even all

– oscillate in rhythmic patterns, caused by sound waves bouncing off the star. These waves are thought to be created by star convection and magnetic fieldand cause a slight expansion and contraction of the star, like a heartbeat. This is detectable as small variations in the amount of light emitted by the star.

Just like earthquakes can be used to explore the bowels of the Earth, the oscillations of stars can reveal what's going on inside, which can be used to learn about properties such as their age, their composition and temperature, an area known as asteroseismology.

To collect asteroseismic data, you need to look at the stars long enough to collect complete information about their light variations. And because TESS was built exactly to look at many stars at once to detect variations in light, even from exoplanetary transits, rather than stellar oscillations, it turns out to be something like a champion of asteroseismology.

In addition to its large-scale observations of exoplanets, TESS has tracked nearly thousands of stars in the Scuti Delta. It was in these latest observations that the researchers detected something surprising: a subset of stars from the Scuti Delta that appeared to have regular pulse patterns.

Kepler also took observations of around 300 stars from the Scuti Delta over a period of four years, so the team added this data to its research. Using specially designed software, they analyzed 92,000 light curves, leading to the identification of 60 stars with regular pulses at high frequencies.

"NASA's TESS data has provided accurate detections on many more of these stars than before." said astronomer Daniel Huber of the University of Hawai & # 39;. "It finally cleared up the picture, and we were able to identify regular structures. It's like the notes of a song that finally fall into place to play a beautiful melody."

A more in-depth analysis of the properties of the regularly pulsed subset of the stars of the Delta Scuti is revealing: they are all younger than the stars of the Delta Scuti which continue to defy order.

This is consistent with our understanding of stellar evolution: that the pulsing spectra become more complex as the stars age. But it can also be used as a powerful tool.

"We can use the information on regular gaps in other stars in the Scuti Delta as an age diagnosis." explained astronomer Daniel Holdsworth of the University of Central Lancashire in the United Kingdom.

"The age of a star, or groups of stars, can be difficult to determine with results that differ by a factor of two. However, asteroseismology has the power to provide very precise ages, offering an opportunity to broaden our understanding of the galaxy around us. "

The data has already helped resolve a debate about the star age of the Scuti Delta named HD 31901, which belongs to the Fish-Eridanus Creek of stars near the solar district. Two previous calculations had appeared at very different ages: around a billion years, based on a red giant believed to be part of the stream; and 130 million years, based on the rotation of other stars in the current.

The asteroseismological data from HD 31901 suggests that it is around 150 million years old, supporting the young age of the current.

"It's really a breakthrough. We now have a regular series of pulses for these stars that we can understand and compare to the models." said astronomer Simon Murphy of the University of Sydney