red giant pulsations

A lighthouse that blinks not every second but once every few minutes or even hours. That is exactly how long-period radio transients behave — cosmic sources discovered only recently.

A red giant in a globular cluster is a star in retirement. It has burned up the hydrogen in its core and now lives off fusion in a thin shell around a helium ash core.

Betelgeuse, the red supergiant familiar from Orion's shoulder, keeps surprising us. After the mysterious Great Dimming of 2019–2020, when the star suddenly dimmed, it didn't just recover; it changed its ways.

The Sun is constantly struck by blows — magnetic reconnection in the plasma releases energy, making the corona flare up. After each such blow, magnetohydrodynamic waves linger in the plasma loops, like the fading ring of a bell.

Night on La Palma. The 4.2-meter William Herschel Telescope is aimed at Venus. At the focus is the experimental polarimeter ExPo, designed to catch the ghostly light of exoplanets.

For over a century, astronomers puzzled over the capricious behavior of RR Lyrae stars: their brightness periodically waxed and waned with unpredictable amplitude, like a lighthouse with a faulty mechanism. The Blazhko effect, discovered in 1907, taunted scientists for decades.

A pendulum swings on its own, but sometimes it suddenly starts swinging so violently that it nearly breaks free from its mount. That's roughly how the white dwarf GD 1212 behaves — a star the size of Earth but with a mass almost like the Sun's.

Strike a bell, and it hums at a single pitch. But if you place a second clapper inside, and they ring without touching each other, the sound becomes more complex. That's roughly how the neutron star from the new study is built. It's not just a hot sphere: inside, two immiscible fluids can flow — for instance, superfluid neutrons and ordinary plasma.

A star weighing a hundred thousand Suns lives bright and brief. Its finale is a rapid collapse into a black hole. But just before the end, it manages to wrap itself in a dense gas cocoon.

Eight red giants — bloated old stars like the future Sun — are not behaving by the book. Their surfaces oscillate steadily, like a bell, but within this chime there are glitches: some tones are missing, and the rhythm breaks. Scientists suspected an invisible hand inside — a magnetic field — and tried to calculate its strength.

Some red giants (huge, old stars) change brightness very slowly: one cycle can last more than a year. Astronomers have long been puzzled about why. One idea: an invisible companion orbits nearby, periodically blocking part of the light. Another: the star itself pulsates, like a heart, but very leisurely: its outer layers alternately contract and expand.

A red giant is a star that has swelled up, cooled on the outside, and become hundreds of times larger than the Sun. Inside, it's far from calm: layers of gas oscillate like a giant bell, causing its brightness to flicker slightly. Astronomers pick up these oscillations to probe what's happening deep within.

The night sky looks still, but many stars tremble like a drum after a strike. For seven straight years, the TESS satellite stared at the same patches of sky and caught this trembling in 19,151 red giants — old, bloated stars. Previously, far fewer of these 'singing' giants were known, and now the list has grown by 80%.

The standard cosmological model describes the birth of the universe as an explosion from a singularity — a point of infinite density and spacetime curvature.

The lighthouse stays silent most of the time, but occasionally it emits a flare so bright it can be seen from hundreds of thousands of kilometers away. That's exactly how the magnetar XTE J1810-197 behaves — an ultra-dense star with a monstrous magnetic field.

In 2019, gravitational-wave detectors caught a signal from the merger of distant objects. One was a black hole of 23 solar masses. The other weighed just 2.5 solar masses — and that's weird. Usually, neutron stars don't get heavier than two solar masses: beyond that, they collapse into a black hole.

A kitchen timer ticks once a second. The neutron star SRGA J144459.2-604207 ticks 448 times a second: that's its own rotation, and it shows up in X-ray bursts. In 2024, the star woke up and started throwing thermonuclear explosions on its surface, like a bubbling pot of boiling water.

Long before stars appeared, the universe was filled with cold hydrogen. This gas can 'sing'—emitting radio waves with a wavelength of 21 centimeters. When the first stars and galaxies ignited, their ultraviolet light began to strip electrons from hydrogen atoms, turning neutral gas into ionized gas.

A star like the Sun hums like a bell: sound waves inside make its surface tremble ever so slightly. From this trembling, astronomers, like doctors reading a pulse, infer the star's temperature, density, and age. But the Kepler telescope spotted an oddity: many stars that spin fast and are covered in spots show no trembling at all. It's as if they've lost their voice.

A red giant in the constellation Cygnus has swelled so much that its outer layers are spilling onto a small but heavy neighbor — a white dwarf. The gas swirls around the dwarf like water down a bathtub drain, falling onto it. But in CH Cygni, this flow is not calm: every 682.5 seconds, the X-ray emission flares and fades.

The neutron star 1E 161348-5055 in the supernova remnant RCW 103 pulses with a period of 6.67 hours. That's very slow for such a compact object, and astronomers long puzzled over what was going on.

For twelve years, astronomers at the LPA radio telescope in Pushchino have been listening to the same patch of sky — the direction of the galaxy 3C 33. In that time, they caught just six short radio signals, each lasting from one to four minutes.

A pulsar is a dead star spinning at breakneck speed, sending out radio pulses like a lighthouse. Usually these pulses arrive right on schedule, but occasionally there are true monsters among them — giant pulses that are thousands of times brighter than normal.

Light from quasar PS J2305+3714 has been traveling toward us for more than eleven billion years. On its way, it passes near a massive galaxy whose gravity bends its path, like a heavy ball denting a stretched sheet. Through a telescope, we see not one quasar but two images — two points of light that are actually the same distant object.