SharePARIS: Astronomers said Thursday they have spotted a hot bubble of gas spinning clockwise around the black hole at the center of our galaxy at "mind blowing" speeds. The detection of the bubble, which only survived for a few hours, is hoped to provide insight into how these invisible, insatiable, galactic monsters work. The supermassive black hole Sagittarius A* lurks in the middle of the Milky Way some 27,000 light years from Earth, and its immense pull gives our home galaxy its characteristic swirl.
The first-ever image of Sagittarius A* was revealed in May by the Event Horizon Telescope Collaboration, which links radio dishes around the world aiming to detect light as it disappears into the maw of black holes. One of those dishes, the ALMA radio telescope in Chile's Andes mountains, picked up something "really puzzling" in the Sagittarius A* data, said Maciek Wielgus, an astrophysicist at Germany's Max Planck Institute for Radio Astronomy.
Just minutes before ALMA's radio data collection began, the Chandra Space Telescope observed a "huge spike" in X-rays, Wielgus told AFP. This burst of energy, thought to be similar to solar flares on the Sun, sent a hot bubble of gas swirling around the black hole, according to a new study published in the journal Astronomy and Astrophysics. The gas bubble, also known as a hot spot, had an orbit similar to Mercury's trip around the Sun, the study's lead author Wielgus said.
But while it takes Mercury 88 days to make that trip, the bubble did it in just 70 minutes. That means it travelled at around 30 percent of the speed of light. "So it's an absolutely, ridiculously fast-spinning bubble," Wielgus said, calling it "mind blowing". The scientists were able to track the bubble through their data for around one and half hours - it was unlikely to have survived more than a couple of orbits before being destroyed. Wielgus said the observation supported a theory known as MAD. "MAD like crazy, but also MAD like magnetically arrested discs," he said.
The phenomenon is thought to happen when there is such a strong magnetic field at the mouth of a black hole that it stops material from being sucked inside. But the matter keeps piling up, building up to a "flux eruption", Wielgus said, which snaps the magnetic fields and causes a burst of energy. By learning how these magnetic fields work, scientists hope to build a model of the forces that control black holes, which remain shrouded in mystery.
The rings of Neptune and a series of bright spots in the southern hemisphere of the planet that represent high-altitude methane-ice clouds.Magnetic fields could also help indicate how fast black holes spin - which could be particularly interesting for Sagittarius A*. While Sagittarius A* is four million times the mass of our Sun, it only shines with the power of about 100 suns, "which is extremely unimpressive for a supermassive black hole, Wielgus said. "It's the weakest supermassive black hole that we've seen in the universe - we've only seen it because it is very close to us." But it is probably a good thing that our galaxy has a "starving black hole" at its center, Wielgus said. "Living next to a quasar," which can shine with the power of billions of suns, "would be a terrible thing," he added.
Meanwhile, the James Webb Space Telescope has turned its gaze away from the deep universe towards our home Solar System, capturing an image of a luminous Neptune and its delicate, dusty rings in detail not seen in decades, NASA said Wednesday. The last time astronomers had such a clear view of the farthest planet from the Sun was when NASA's Voyager 2 became the first and only space probe to fly past the ice giant for just a few hours in 1989.
Now Webb's unprecedented infrared imaging capabilities has provided a new glimpse into Neptune's atmosphere, said Mark McCaughrean, a senior advisor for science and exploration at the European Space Agency. The telescope "takes all that glare and background away" so that "we can start to tease out the atmospheric composition" of the planet, McCaughrean, who has worked on the Webb project for more than 20 years, told AFP.
Neptune appears as deep blue in previous images taken by the Hubble Space Telescope due to methane in its atmosphere. However the near-infrared wavelengths captured by Webb's primary imager NIRCam shows the planet as a greyish white, with icy clouds streaking the surface. "The rings are more reflective in the infrared," McCaughrean said, "so they're much easier to see".
The image also shows an "intriguing brightness" near the top of Neptune, NASA said in a statement. Because the planet is tilted away from Earth and takes 164 years to orbit the Sun, astronomers have not yet had a good look at its north pole. Webb also spotted seven of Neptune's 14 known moons. Looming over Neptune in a zoomed-out image is what appears to be a very bright spiky star, but is in fact Triton, Neptune's strange, huge moon haloed with Webb's famed diffraction spikes.
Triton, which is larger than dwarf planet Pluto, appears brighter than Neptune because it is covered in ice, which reflects light. Neptune meanwhile "absorbs most of the light falling on it", McCaughrean said. Because Triton orbits the wrong way around Neptune, it is believed to have once been an object from the nearby Kuiper belt which was captured in the planet's orbit. "So it's a pretty cool to go and have a look at," said McCaughrean.
As astronomers sweep the universe searching for other planets like our own, they have found that ice giants such as Neptune and Uranus are the most common in the Milky Way. "By being able to look at these ones in great detail, we can key into our observations of other" ice giants," McCaughrean said. Operational since July, Webb is the most powerful space telescope ever built, and has already unleashed a raft of unprecedented data. Scientists are hopeful it will herald a new era of discovery.
Research based on Webb's observations of both Neptune and Triton is expected in the next year. "The kind of astronomy we're seeing now was unimaginable five years ago," McCaughrean said. "Of course, we knew that it would do this, we built it to do this, it is exactly the machine we designed. "But to suddenly start seeing things in these longer wavelengths, which were impossible before... it's just absolutely remarkable." - AFP
