From "influencer" black holes to cosmic fireworks A Hitchhiker's Guide to the Five Wonders of the Milky Way

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A Hitchhiker's Guide to the Five Wonders of the Galaxy

Over the past few decades, human eyes have swept over many of the wonders of the solar system: the crisscrossing rivers of Mars, the geysers of Enceladus that shoot into space, the cold icebergs of Pluto, and so on.

If you extend your horizon further, what surprises will you catch? In a recent report, the website of the British magazine "New Scientist" depicted an exhilarating journey through the most magnificent landscapes of the Milky Way: from an "Internet celebrity" black hole to a river of dark matter; From exoplanets habitable to humans to a grand cosmic firework...

S1 Stream: A "river" of stars carrying dark matter

The trip officially begins. The first step is to jump into a stellar "river" that runs through the entire Milky Way galaxy – the S1 stream. The sun is in it, like a grain of dust in the Sahara Desert.

To find the source of the S1 stream, we need to turn back the clock to 90 billion years ago, when the Milky Way was in a turbulent youth, and its gravitational pull dragged nearby dwarf galaxies apart, leaving only a pile of debris to form this fast-moving, star-like "river".

In 2017, astronomers used the European Space Agency's Gaia probe to confirm that the S1 stream was the stripped remains of an ancient dwarf galaxy.

Zhang Chengmin, a researcher at the National Astronomical Observatories of the Chinese Academy of Sciences, told Science and Technology Daily: "Measurements of stellar motion show that dwarf galaxies are rich in dark matter. Therefore, the S1 stream is primarily a stream of dark matter, and traveling along the S1 stream will give us the opportunity to solve one of the biggest mysteries in physics – the mystery of dark matter. ”

Proxima Centauri B: A habitable exoplanet

According to Zhang, scientists have so far discovered more than 5000,4 planets orbiting stars in the Milky Way, the most interesting of which is Proxima Centauri B, because it is the closest exoplanet to Earth, at a distance of about 22.<> light years. Scientists believe that Proxima Centauri B may be suitable for life to thrive.

Scientists speculate that Proxima Centauri b should be located in the habitable zone. Although Proxima Centauri b is only 0.05 astronomical units (solar-terrestrial distance) from its host star, its host star is a red dwarf star with a mass of only 12.3% of the mass of the Sun and a luminosity of only 1.55‰ of the Sun.

In addition, Proxima Centauri orbits its star every 11 days and is tidally locked. Thus, one side of Proxima Centauri B is forever in the day, while the other side is trapped in eternal night. Here you will see a real extraterrestrial spectacle: the sunset that hangs forever in the sky.

Betelgeuse: Enjoy the "curtain call" of a star

The next travel destination is a huge star, more than 10,<> times brighter than the Sun, located in the constellation Orion, which glows crimson during the cold winter months. The star, called Betelgeuse, is so "changeable" that it could explode into a supernova at any moment.

"Part of the reason it's so big is that it's born huge, but the main reason is that it's inflated into a super-red giant," Zhang explained. It depletes the hydrogen element that sustains nuclear combustion and is burning helium, which causes the star to constantly expand outward. ”

"The end is coming: Helium usually burns enough to last a star for a few million years, then the star frantically burns off the rest of the heavier elements, carbon for a few hundred years, then oxygen burns for six months, and on the last day of its life, the star burns silicon to iron." Zhang Chengmin described.

Magnetar SGR 1935+2154: Gaze at high-energy signals from deep space

Fast radio bursts (FRBs) have always bothered astronomers. In 2020, they discovered FRB for the first time in the Milky Way, from the magnetar SGR 1935+2154, which was also the next stop on the trip.

One should be wary of SGR 1935 + 2154, even at a distance of 1000 km from it, strong magnetism can tear atoms into a mist. But from a safe distance, you'll see strange flashes of light on its surface, as magnetars distort space-time around it, refracting light traveling nearby.

"A closer look at SGR 1935+2154 helps us figure out how FRB came about. One view is that a star wind of charged particles pours in from the north and south poles of the magnetar, hitting the magnetic field and causing radiation. Another view is that FRBs are caused by huge vibrations in the magnetar crust called 'starquakes'. Zhang Chengmin said.

Sagittarius A*: The black hole of the "Internet celebrity" with heavy responsibilities

"No trip to the galaxy without visiting the supermassive black hole Sagittarius A* at the center of the galaxy is incomplete, because not only will we see a fascinating light show, but we may even find key clues about the true nature of space-time," Zhang quipped. ”

Last year, the Event Vision Telescope team took the first image of Sagittarius A*, a blurry orange "doughnut" image that also dominated newspaper headlines around the world.

The edge of the black hole is called the event horizon, and anything that passes through the event horizon is swallowed by the black hole, but outside of the event horizon, the extreme distortion of space-time means that light can be pulled into an "endless circle". Light from all the stars inside and outside the Milky Way is trapped inside this "photon sphere". Here, there's a chance to see a truly unlimited cosmic movie released. (Science and Technology Daily reporter Liu Xia)