The mysterious darkening of the four is due to stellar spots covering 70% of the surface

BEIJING, July 1 (Xinhua) — Astronomers say that earlier this year, the red superstar Satoshi IV began to darken, possibly due to the star spots covering 70 percent of its surface, according tomedia reports. Located in Orion, 500 light-years from Earth, it is one of the brightest stars in the night sky, but by April 2020 its brightness had dropped to 40% of normal, leading to speculation that it might turn into a supernova.

A supernova is a giant star that, when it enters the end of life, drains most of its mass into space, and the star’s gradual darkening is a sign that it may become a supernova. After April this year, the four-year-old began to brighten again, ruling out the possibility of becoming a supernova, so astronomers began looking for a new theory to explain the unusual phenomenon of star darkening.

A mainstream theory is that a huge cloud of dust and gas moves between Earth and The Four, obscuring part of the field of view of large-mass stars. This is not the case, according to staff at the Max Planck Institute, which is caused by a huge “cold star spot” that covers 70 percent of the star’s surface, reducing the temperature of the star.

Study author Thavisha Dharmawardena and colleagues point out that stellar spots are not uncommon on giant stars, but they are unusually large on the four spots. Red giants like Satoshi have experienced frequent brightness changes, which is why we spent months observing to make sure the event was unusual. Between October 2019 and April 2020, the light level of Sion IV plummeted to 40% of normal, surprising astronomers.

Scientists have come up with a number of solutions to explain changes in the brightness of the star, which is visible to the naked eye over a 500-light-years range. According to Thavisha Dharmawardena, the temperature change in the photosphere (the glowing surface of the star) causes the visible brightness of the four to drop, possibly from a giant cold star sunspot, similar to a sunspot, which covers 50-70% of the star’s surface.

“At the end of their lives, stars become red giants, and when they run out of fuel, the process by which stars release energy changes, and because of these changes in star expansion, the brightness of the stars fluctuates in an unstable and brightness over a period of several years,” said TharashDharmawardena. The four are red giants, about 20 times the mass of the sun and about 1,000 times the size of the sun. “

The mysterious darkening of the four is due to stellar spots covering 70% of the surface

If the four are located at the center of the solar system, its edges will reach Jupiter’s orbit, and because of its sheer size and the gravitational pull on the surface of the star is smaller than the same mass and smaller radius, stars like this could easily generate brightness pulses from the outer layers.

If the four are located at the center of the solar system, its edges will reach Jupiter’s orbit, and because of its sheer size and the gravitational pull on the surface of the star is smaller than the same mass and smaller radius, stars like this could easily generate brightness pulses from the outer layers.

When the released gas cools down, it forms what astronomers call a compound of interstellar dust, a heavier element of the universe that is the main source of star and planetary formation. Astronomers previously believed that sucking dust was the most likely cause of a sharp decline in star brightness.

To test this hypothesis, Thavisha Dharmawardena and colleagues evaluated the latest observations from the Atacama Pathfinder Experiment and the James Clark Maxwell Telescope, which measured submillimeter-wave radiation at wavelengths 1,000 times that of visible light.

Changes in star brightness are invisible to the human eye, and astronomers have been studying interstellar dust for some time using changes in stellar brightness, because cold dust emits light at a certain wavelength. Steve Mars, of the East Asia Observatory, said it was surprising that the four were 20 percent darker in the submillimeter wavelength range.

Experience has shown that the dimening of stars does not match the presence of interstellar dust, and in order to make a more accurate assessment, the team calculated the effect of dust on the measurements within that spectral range, and it turns out that the decrease in brightness in the submillimeter range cannot be attributed to the increase in interstellar dust.

The mysterious darkening of the four is due to stellar spots covering 70% of the surface

If the four are located at the center of the solar system, its edges will reach Jupiter’s orbit, and because of its sheer size and the gravitational pull on the surface of the star is smaller than the same mass and smaller radius, stars like this could easily generate brightness pulses from the outer layers.

Astronomers based on data on star brightness changes observed between October 2019 and April 2020 believe that changes in star brightness must have been caused by the star itself. The laws of physics tell us that the brightness of a star depends on the star’s diameter, especially the surface temperature, and that as long as the star is reduced in size, the luminosity decreases equally at all wavelengths.

However, the effect of changes in star temperature on electromagnetic spectral radiation is different. Scientists say the dimening of star brightness under visible light and submillimeter waves is evidence of a drop in the temperature of the four average surfaces.

Study co-author Peter Hickluna of the European Southern Observatory explained that asymmetric temperature distributions are more likely to occur, with high-resolution images from December 4, 2019 showing different brightness areas.

The combined results clearly show that giant star spots cover 50-70% of the star’s surface, at a lower temperature than the bright sphere of light. Star spots are common among giant stars, but there are size differences and little is known about stellar spots, but the theoretical models seem to calculate the duration of the drop in the brightness of the ginseng four.

It is well known that the change in the number of sunspots is a cycle of 11 years, whether the giant star has a similar mechanism is not clear, and the latest observations of The Ivy 4 may be the smallest amount of previous brightness. “Observations over the next few years will tell us whether the sharp decline in the brightness of The 4th is related to the blackspot cycle, and in any case, ginseng IV will remain an exciting target for astronomical observations in the future,” said Thaisha Dharmawardena. The latest study is published in the recently published Journal of Astrophysics. (Leaf Town)