Study Findings: Discovery of a Star Sensitive to the Spin of Sagittarius A*

Posted on by onespaceman2000
Image (Credit): The Milky Way galaxy. (NASA)

Nature abstract of study findings:

Residing in the centre of the Milky Way, Sagittarius A* (Sgr A*) is the closest massive black hole1 (MBH). Its vicinity has allowed measuring individual stellar orbits around it. The stars act as test particles and probe the gravitational potential around the 4.3 × 106M⊙ MBH. These observations have determined the central mass to sub-per-cent precision, and the mildly relativistic motions of stars have given access to the dominant relativistic corrections, the gravitational redshift, the transverse Doppler effect and the prograde precession imposed by the Schwarzschild metric nature of the potential. These effects are of order β2 = (v/c)2 (for velocity v and speed of light c). The Kerr metric for a rotating black hole leads to corrections of order β3. Here, we report the discovery of a faint main-sequence star (mK = 19.3), S301, on an 8.7-year orbit and with small enough a pericentre distance, such that the peak velocity of the star reaches 25,000 km s−1. Within the measurement abilities of current near-infrared interferometry and future spectroscopy on an extremely large telescope, the motion of S301 is directly sensitive to the spin of Sgr A*. The high eccentricity of S301 suggests that it is the captured component of a binary that was torn apart by the Hills mechanism.

Citation:  Abd El Dayem, K., Abuter, R., Aimar, N. et al. Discovery of a star sensitive to the spin of Sagittarius A*. Nature 657, 359–363 (2026).

DOI: https://doi.org/10.1038/s41586-026-10894-w

Study-related stories:

Science News – “A Record-breaking Star Could Reveal How the Milky Way’s Giant Black Hole Spins”

Universe Today – “The Fastest Star in the Milky Way Will Test Relativity”

Sky & Telescope – “Star Feels Spin of Milky Way’s Black Hole”

Space Quote: A New Space Telescope is Being Planned

Posted on by onespaceman2000
Image (Credit): Artist’s rendering of the PRIMA space telescope. (NASA/JPL-Caltech)

“With our Webb and Roman space telescopes, we set a cadence of launching premiere-class missions in both halves of the decade. We’re going to keep that up and kick off the next decade with PRIMA, as part of a pipeline that will consistently have missions of this caliber ready to go.”

–Statement by Shawn Domagal-Goldman, director of the Astrophysics Division at NASA Headquarters, regarding the planned $1.2 billion PRobe far-Infrared Mission for Astrophysics (PRIMA) space telescope. The plan is to launch the space telescope in 2033 to conduct a five-year mission. The main mission of the space telescope will pertain to exoplanet origins, galaxy growth and black hole evolution. It is encouraging to hear about NASA planning these future missions with all the talk of program cuts from the White House. It is probably presumed that the Congress will keep the funding coming.

Space Stories: Dragon Delays, Odd Black Holes, and Surprising Martian Warmth

Posted on by onespaceman2000
Image (Credit): SpaceX Dragon capsule. (SpaceX)

Here are some recent space-related stories of interest.

—Space.com: “SpaceX, NASA Delay Next Astronaut Launch to ISS Due To Leak on Dragon Spacecraft”

SpaceX’s next astronaut mission to the International Space Station won’t launch on Sept. 12 after all. That flight, known as Crew-13, has been delayed due to an oxidizer leak in the propulsion system of SpaceX’s Dragon spacecraft, NASA announced on Saturday (Aug. 29). Joint NASA and SpaceX teams are performing additional tests and data review and will complete any necessary rework prior to launch,” NASA officials wrote in an update on Saturday. “A new target date will be announced once available.”

—Earth.com: “Giant Black Holes Appeared Too soon After the Big Bang, and Astronomers May Know Why“

Nearly every large galaxy keeps a giant black hole at its center. Some of those giants already weighed a billion Suns when the universe was less than 700 million years old. Astronomers have struggled for decades to explain how anything grew that heavy that fast. A new study built on James Webb Space Telescope observations suggests one possible answer. The researchers describe a young black hole wrapped in gas so dense that the whole object shines like a single enormous star. Astronomers call objects like it black hole stars. The light from this one has been traveling for 13 billion years, since a moment just 660 million years after the Big Bang, and no earlier example has been found.

—Caltech: “Thermal Anomaly Discovered Below Mars’s South Pole“

Based on gravitational measurements that give clues to the Red Planet’s interior structure, Mars’s interior southern hemisphere is around 200 to 400 degrees Celsius warmer than the northern half of the planet and partially molten. The surprising finding adds additional context to Martian history and the periods of time in which it may have hosted conditions favorable for life. The research was led by Caltech alumnus Alexander Berne (PhD ’26), who is now a postdoctoral associate at the University of Arizona. The findings are reported in a paper appearing in the journal Nature on August 27.

Note: Here is the podcast version of this post.

Pic of the Week: Galaxy M83

Posted on by onespaceman2000
Image (Credit): Galaxy M83 shown in both X-ray and Optical Light. (X-ray: NASA/CXC/SAO; Optical: NASA/ESA/AURA/STScI, Hubble Heritage Team, W. Blair (STScI/Johns Hopkins University) and R. O’Connell (University of Virginia); Image Processing: NASA/CXC/SAO/A. Jubett, L. Frattare and P. Edmonds)

This week’s image is from the Chandra X-ray Observatory. It shows galaxy Messier 83 (M83), which is located approximately 15 million light-years from Earth. It is part of a study analyzing Chandra data from 2000 to 2014.

NASA provides more information on a recent study involving supernova remnants being studied by astronomers:

In the composite image, Messier 83, or M83, is shown to have a spiral structure, viewed straight on. At the center is a brilliant white and yellow pool of light. From that light, spiral arms of hot pink cloud corkscrew out in wide, sweeping arches. The galaxy is covered in a faint grey haze, and flecked with red, green, blue, white, and yellow dots.

Over a 14-year period from 2000 to 2014, astronomers pointed NASA’s X-ray observatory at the M83 galaxy. They discovered that about half of the X-ray sources believed to be supernova remnants, the aftermath of stellar explosions, were exhibiting dramatic changes in brightness. This result was entirely unexpected.

Those changes in brightness are highlighted in the timelapse videos. In each video, a series of static images flashes by, focused on one of the two X-ray sources once believed to be supernova remnants. In the videos, the X-ray sources appear as bright blue blobs with glowing cores. But in each image, taken months or years apart, the shapes change, as does the intensity of the blue color, and the brightness of the core. By presenting the substantively different images of the same objects one after another in quick succession, short timelapse videos are created.

The most likely explanation for the changes in brightness is that the team has uncovered a population of stellar survivors, stars that lived through an orbiting partner’s destruction in a supernova explosion. Material is being pulled from the surviving star onto the black hole or neutron star that formed in the supernova, a process known to cause rapid changes in X-ray brightness.

Go to the NASA link for images of two supernova remnants within galaxy M83.

Space Stories: A Peruvian Solar Observatory, NASA Rocket Traffic, and a Reborn Back Hole

Posted on by onespaceman2000
Image (Credit): Aerial view of the fortress at Chankillo. (Servicio Aerofotográfico Nacional, Lima)

Here are some recent space-related stories of interest.

—Discover Magazine: “The Earliest-Known Astronomical Observatory in the Americas May Offer New Insights“

There was a time when Stonehenge was believed to be a kind of “Neolithic computer.” Archaeology has since corrected that misconception. Today, the evidence points strongly in another direction: to an arid hill in the Casma Valley on Peru’s northern coast, about 200 miles north of Lima. There stands Chankillo, a complex built around 250 B.C.E., considered the earliest known solar observatory in the Americas and the clearest known example of a monument designed to track the sun’s position throughout the entire year, according to a study in Science. Modest in appearance and largely absent from tourist posters and classic postcards, Chankillo has renewed attention as archaeologists report preliminary findings from ongoing excavations.

—CBS News: “NASA Juggling Piloted Moon Mission and Space Station Crew Replacement Flight“

With a space station medical evacuation safely completed, NASA is focused on two challenging missions proceeding in parallel: launching four astronauts on a flight around the moon, at the same time as the agency is planning to send four replacement astronauts to the International Space Station...The Artemis 2 mission and Crew 12’s planned space station flight present a unique challenge for NASA. The agency has not managed two piloted spacecraft at the same time since a pair of two-man Gemini capsules tested rendezvous procedures in low-Earth orbit in 1965. The agency has never flown a deep space mission amid another launch to Earth orbit.

—Royal Astronomical Society: “‘Reborn’ Black Hole Spotted ‘Erupting like Cosmic Volcano’“

One of the most vivid portraits of “reborn” black hole activity – likened to the eruption of a “cosmic volcano” spreading almost one million light-years across space – has been captured in a gigantic radio galaxy. The dramatic scene was uncovered when astronomers spotted the supermassive black hole at the heart of J1007+3540 restarting its jet emission after nearly 100 million years of silence.

Note: Please ignore the previous posting for today about the Apollo 17 mission. It’s a good story, but I will need to retell it at another time (that is, on December 19th).