A helium-rich wind from the stars, which reaches our solar system from the Serpentine constellation. The Sun's gravity concentrates the material into a cone shape, which it passes through in the first weeks of December.
Amit Oren, Israeli Astronomical Society
Every year at the beginning of December, something happens that can depress your horoscope a little. The Sun enters the serpent-bearer group [Ophiuchus], the 13th lesser-known group of the zodiac.
You must have heard of the groups: Capricorn, Aquarius, Pisces, Aries, Taurus, Gemini, Cancer, Leo, Virgo, Libra, Scorpio and Sagittarius. The sun moves through these celestial groups throughout the year. These are the ancient signs of the zodiac.
But... a snake-bearer?!
A snake-themed group, as illustrated in the Sky catalog
Astronomers of our time do not divide the sky in the same way that astronomers of ancient peoples did. Apparently, in modern charts, the Sun passes through the 13th group, the serpent-bearer between November 30th and December 17th. And in astrological terms: if you were born between these two dates, you are not a Sagittarius, but an Ophiuchi! But, that's another story...
This article examines what really happens when the sun enters the thirteenth group: an interstellar wind hits our planet.
It is a helium-rich wind from the stars, which reaches our solar system from the Serpentine constellation. The Sun's gravity concentrates the material into a cone shape, which it passes through in the first weeks of December. We are in this cone at this very moment.
"There is no danger to anyone on Earth," says space physicist George Gloeckler of the University of
Maryland [University of Maryland]. "The helium breeze is 10 times less dense than the NASA atmosphere by a factor of 21 times, and therefore cannot penetrate the surface of the planet."
Nevertheless, astronomers are eager to study it.
The wind is a sign of what lies outside our solar system. Interstellar space, the "void" between the stars, is not really empty, but full of clouds of gas and dust. These clouds are the places where stars and planets are born; They are also remnants of stars that have ended their lives - exploded. Well, our solar system is moving towards such a cloud, which astronomers call the "Local Interstellar Cloud". The sun's magnetic field keeps most of the material coming from the cloud close to the sun, but some of the gas in the cloud manages to penetrate - and that's why the interstellar wind is created.
The sun's gravity diverts the breeze from its path and causes it to crystallize in the direction of its flow, thus the central cone is formed
ACE, NASA's spacecraft, which is now at the first Lagrange point [a point in space where two or more bodies are in equilibrium], is perfectly positioned to study the breeze. "As the Earth moves through the central cone (the area where the Sun's gravity concentrates the breeze), so does ACE," explains Glöckler, who is one of the lead researchers on the ACE team. "We have passed through this cone seven times since the spacecraft was launched in 1997."
ACE's mission is to study the solar wind - a warm breeze from our sun, so the spacecraft is equipped to study the interstellar wind as well. The SWICS instrument on board the spacecraft detects helium ions in the breeze, measures their density, temperature, and direction of flow. Using these measurements, and information from other spacecraft (mainly SOHO and Ulysses), Glockler and his teammates calculated the properties of the regional interstellar cloud.
Artisan perception - the regional interstellar cloud [Local Intersellar Cloud]
It is a hot cloud, the temperature of the gas is about 6,000 degrees, about the temperature on the surface of the sun. Also, the cloud is not particularly dense, with an average of 0.264 atoms per cubic cm. The Sun's magnetic field has trouble tilting this material before it crosses Pluto's orbit, but on average, a fraction of the material reaches the inner solar system region (0.015 atoms per cubic cm).
One day the solar system may collide with something even more massive. There are clouds in the galaxy that are a thousand times denser than the regional interstellar cloud. Priscilla Frisch, an astronomer at the University of Chicago, studied what might happen if we collided with one of these clouds. In an article she published in the "American Scientist" newspaper, she reports: "A cloud with a density of 1,000 atoms per centimeter can compress the sun's magnetic field by several astronomical units (astronomical unit - Astronomical Unit [AU] - the average distance between the sun and the Earth). Planets like Saturn, Uranus, Neptune and Pluto will be fully exposed to interstellar atoms and molecules. Interstellar gas will 'subdue' the solar wind at a distance of one astronomical unit," - and the entire space environment of our planet will be completely changed.
The first signs of such a change can be seen in a change or reduction in the direction of the flow of helium, as a harbinger of things to come.
ACE has detected changes. "We see strong gusts of wind and 'tidal' phenomena," says Glockler. "We doubt whether the source of these changes is extrasolar." Instead, the sun is probably responsible. The helium breeze is probably blowing through a much denser solar wind, which can drive the breeze around. Sunspots also affect the breeze. Ultraviolet radiation that shines from sunspots ionizes the breeze and makes it look different in devices like the SWICS.
ACE/SWICS measurements of helium flow in the breeze. "Peaks" indicate annual transitions through the central cone, you can click to see the full results [from 1997]
"What we are doing now," explains Glockler, "is to study how solar activity affects the breeze. Only if we can report on the sun reliably, in great detail, can we use these measurements to diagnose extrasolar space."
What's out there? what's coming The answer lies in the breeze from the stars of the 13th house.
