OrbitalHub

NASA dicit:

Using NASA’s Neil Gehrels Swift Observatory, which launched in 2004, scientists have discovered a black hole in a distant galaxy repeatedly nibbling on a Sun-like star. The object heralds a new era of Swift science made possible by a novel method for analyzing data from the satellite’s X-ray Telescope (XRT). When a star strays too close to a monster black hole, gravitational forces create intense tides that break the star apart into a stream of gas. The leading edge swings around the black hole, and the trailing edge escapes the system. These destructive episodes are called tidal disruption events. Astronomers see them as flares of multiwavelength light created when the debris collides with a disk of material already orbiting the black hole.

Recently, astronomers have been investigating variations on this phenomena, which they call partial or repeating tidal disruptions. During these events, every time an orbiting star passes close to a black hole, the star bulges outward and sheds material, but survives. The process repeats until the star looses too much gas and finally breaks apart. The characteristics of the individual star and black hole system determine what kind of emission scientists observe, creating a wide array of behaviors to categorize.

On June 22, 2022, XRT captured Swift J0230 for the first time. It lit up in a galaxy around 500 million light-years away in the northern constellation Triangulum. Swift’s XRT has observed nine additional outbursts from the same location roughly every few weeks. Scientists propose that Swift J0230 is a repeating tidal disruption of a Sun-like star orbiting a black hole with over 200,000 times the Sun’s mass. They estimate the star loses around three Earth masses of material on each pass. This system provides a bridge between other types of suspected repeating disruptions and allowed scientists to model how interactions between different star types and black hole sizes affect what we observe.

Swift J0230’s discovery was possible thanks to a new, automated search of XRT observations called the Swift X-ray Transient Detector. After the instrument observes a portion of the sky, the data is transmitted to the ground, and the program compares it to previous XRT snapshots of the same spot. If that portion of the X-ray sky has changed, scientists get an alert. In the case of Swift J0230, astronomers were able to rapidly coordinate additional observations of the region.

Video credit: NASA’s Goddard Space Flight Center/Producer: Sophia Roberts (AIMM)/Science writer: Jeanette Kazmierczak (University of Maryland College Park)/Editor: Sophia Roberts (AIMM)/Narrator: Sophia Roberts (AIMM)/Animator: Chris Smith (KBRwyle)/Project support: Scott Wiessinger (KBRwyle)

NASA dicit:

NASA’s Neil Gehrels Swift Observatory tallied the water lost from an interstellar comet as it approached and rounded the Sun. The object, 2I/Borisov, traveled through the solar system in late 2019.

Comets are frozen clumps of gases mixed with dust, often called “dirty snowballs.” As a one approaches the Sun, frozen material on its surface warms and converts to gas.

When sunlight breaks apart water molecules, one of the fragments is hydroxyl, a molecule composed of one oxygen and one hydrogen atom. Swift detects the fingerprint of ultraviolet light emitted by hydroxyl using its Ultraviolet/Optical Telescope (UVOT). Between September and February, Swift made six observations of Borisov with Swift. It saw a 50% increase in the amount of hydroxyl — and therefore water — Borisov produced between Nov. 1 and Dec. 1, which was just seven days from the comet’s closest brush with the Sun.

At peak activity, Borisov shed eight gallons (30 liters) of water per second, enough to fill a bathtub in about 10 seconds. During its trip through the solar system, the comet lost nearly 61 million gallons (230 million liters) of water — enough to fill over 92 Olympic-size swimming pools. As it moved away from the Sun, Borisov’s water loss dropped off — and did so more rapidly than any previously observed comet.

Swift’s water production measurements also helped show that Borisov’s minimum size is just under half a mile (0.74 kilometer) across. The team estimates at least 55% of Borisov’s surface was actively shedding material when it was closest to the Sun. That’s a large fraction compared to most observed solar system comets.

Video credit: NASA’s Goddard Space Flight Center/Scientific Visualization Studio/Scott Wiessinger (USRA): Lead Producer/Jeanette Kazmierczak (University of Maryland College Park): Lead Science Writer/Scott Wiessinger (USRA): Lead Animator/Dennis Bodewits (Auburn University): Scientist/Zexi Xing (University of Hong Kong): Scientist/Francis Reddy (University of Maryland College Park): Science Writer

NASA dixit:

“Observations by NASA’s Swift spacecraft, now renamed the Neil Gehrels Swift Observatory after the mission’s late principal investigator, have captured an unprecedented change in the rotation of a comet. Images taken in May 2017 reveal that comet 41P/Tuttle-Giacobini-Kresak — 41P for short — was spinning three times slower than it was in March, when it was observed by the Discovery Channel Telescope at Lowell Observatory in Arizona. The abrupt slowdown is the most dramatic change in a comet’s rotation ever seen.

Comet 41P orbits the Sun every 5.4 years. As a comet nears the Sun, increased heating causes its surface ice to change directly to a gas, producing jets that launch dust particles and icy grains into space. This material forms an extended atmosphere, called a coma.

Ground-based observations established the 41P’s initial rotational period at about 20 hours in early March 2017 and detected its slowdown later the same month. The comet passed 13.2 million miles (21.2 million km) from Earth on April 1, and eight days later made its closest approach to the Sun. Swift’s Ultraviolet/Optical Telescope imaged the comet from May 7 to 9, revealing brightness variations associated with material recently ejected into the coma. These slow changes indicated 41P’s rotation period had more than doubled, to between 46 and 60 hours.

UVOT-based estimates of 41P’s water production, coupled with the body’s small size, suggest that more than half of its surface area contains sunlight-activated jets. That’s a far greater fraction of active real estate than on most comets, which typically support jets over only about 3 percent of their surfaces. Astronomers suspect these active areas are favorably oriented to produce torques that slowed 41P’s spin.

Such a slow spin could make the comet’s rotation unstable, allowing it to begin tumbling with no fixed rotational axis. This would produce a dramatic change in the comet’s seasonal heating and may result in future outbursts of activity.”

Music credit: “Valley of Crystals” from Killer Tracks

Video credit: NASA’s Goddard Space Flight Center/Scott Wiessinger

NASA dixit:

“This artist’s rendering illustrates new findings about a star shredded by a black hole. When a star wanders too close to a black hole, intense tidal forces rip the star apart. In these events, called “tidal disruptions,” some of the stellar debris is flung outward at high speed while the rest falls toward the black hole. This causes a distinct X-ray flare that can last for a few years. NASA’s Chandra X-ray Observatory, Swift Gamma-ray Burst Explorer, and ESA/NASA’s XMM-Newton collected different pieces of this astronomical puzzle in a tidal disruption event called ASASSN-14li, which was found in an optical search by the All-Sky Automated Survey for Supernovae (ASAS-SN) in November 2014. The event occurred near a super-massive black hole estimated to weigh a few million times the mass of the sun in the center of PGC 043234, a galaxy that lies about 290 million light-years away. Astronomers hope to find more events like ASASSN-14li to test theoretical models about how black holes affect their environments.

During the tidal disruption event, filaments containing much of the star’s mass fall toward the black hole. Eventually these gaseous filaments merge into a smooth, hot disk glowing brightly in X-rays. As the disk forms, its central region heats up tremendously, which drives a flow of material, called a wind, away from the disk.”

Video credit: NASA’s Goddard Space Flight Center