This discovery marks a major milestone in the search for life on worlds beyond our solar system. A faint stream of helium escaping from a distant rocky world has revealed something astronomers had never clearly detected before: an atmosphere around an Earth-like planet in another star’s habitable zone. The result is the strongest evidence so [...]

The subject of this NASA/ESA Hubble Space Telescope image is a spiral galaxy struggling against titanic forces that appear on galactic scales in space. This is NGC 4654, an intermediate spiral galaxy in the constellation Virgo (the Maiden). It is classified as an “intermediate” because its overall shape lies between spiral galaxies that have a bar across their centers and those that don’t. NGC 4654 has a weak bar structure at its center and is located 72 million light-years from Earth in the Virgo Cluster, a particularly massive and populous galaxy cluster.

NGC 4654 is particularly asymmetric, with a rounded and clearly-defined edge on one side and a long tail of gas stretching out from the opposite side — outside the field of view captured in this image. This gaseous tail is the result of ram pressure stripping, a force that galaxies can experience as they plow through space. NGC 4654 moves with such high velocity that it sweeps up and rams through the hot, rarefied gas filling the space between the Virgo Cluster’s galaxies. This intracluster medium in turn exerts a “ram pressure” on the galaxy, compressing the galaxy’s leading edge and dragging its gas behind the galaxy, creating the elongated tail.

It’s not just the galaxy’s gas that is unevenly distributed: its stars are too, and this is more unusual for a spiral galaxy. While the spiral arm on its leading edge is rich with stars and gas, the opposite arm noticeably lacks stars, influencing the galaxy’s lopsided spiral shape. Astronomers think that ram pressure alone is unlikely to cause this effect. Rather, NGC 4654 was also subjected to the gravitational force of fellow Virgo Cluster galaxy NGC 4639. While the two galaxies are far apart now, it’s thought that a fly-by interaction between them around 500 million years ago ripped away NGC 4654’s gas along one side, limiting star formation there and creating the asymmetry in its shape.

Many galaxies that undergo ram pressure stripping suffer reduced star formation rates as the cold gas that collapses to form their stars is pulled away and lost. NGC 4654, however, is still forming nearly two Suns’ worth of stars every year, a rate comparable to other galaxies of similar size. The active star formation is visible in the latest Hubble data included in this image. The data picks up on a wavelength of red light emitted by the clouds of energized gas where newborn stars lurk. The bright pink bubbles that appear across NGC 4654 — from its forward spiral arm, to around its weak bar, and out to the edge of its disk — are areas where these newborn stars shine.

The data used in this image came from two observing programs (#15654, #17502) that aim to link the gas in galaxies with star formation. By observing many prominent galaxies in the vicinity of our own, researchers hope to better understand how gas moves in galaxies, where and when it collapses to form stars and star clusters, and what effect those new stars have on the gas around them.

Text Credit: ESA/Hubble

Media Contact:

Claire Andreoli
NASA’s Goddard Space Flight Center, Greenbelt, MD
claire.andreoli@nasa.gov

Webb found a hidden giant planet by detecting its atmospheric chemistry through a bright debris disk. For years, a third giant planet remained concealed within the bright dust surrounding Beta Pictoris, one of the most closely observed planetary systems in the Milky Way. NASA’s James Webb Space Telescope has now exposed the hidden world by [...]

Scientists have identified an accelerator that produces the highest-energy protons in our galaxy, a finding that could clarify the nature of the fast-moving particles filling the space between stars. Across the Milky Way, charged particles race through space with energies beyond the reach of even the most powerful accelerators built on Earth. Known as cosmic [...]

Around 4.6 billion years ago, an immense cloud of gas and dust in space collapsed in on itself. As it collapsed, gravity pulled most of the material toward several small points, one of which would eventually become our Sun. The other points formed other stars in what scientists call an open cluster. 

During this early stage of the Sun’s life, it was surrounded by a swirling disk of leftover material aligned with its equator, known as a protoplanetary disk. Eventually, this disk condensed to form the planets that make up our solar system. This process normally results in a system with a star at its center, and the planets orbiting the plane of the star’s equator. 

However, scientists have found that this scenario doesn’t quite hold for our solar system. The planets in our solar system orbit the Sun in a single plane offset from the Sun’s equator by approximately 6°. The fact that the planets are in the same orbital plane suggests that the protoplanetary disk model of solar system formation is correct, since the odds of the Sun capturing 8 rogue planets in this arrangement are astronomically low. So, what threw the planets in our solar system off-kilter?

To determine what caused the solar system to tilt, Daohai Li at Queen Mary University of London recently used the computer program NBODY6++ to model different versions of the open cluster from which the Sun came. In these simulations, he varied the number of stars in the cluster, from 500 to 2,000 to 8,000. He also varied the radius of the cluster, from 0.25 to 1 to 4 parsecs (8 to 30 to 100 trillion kilometers or 5 to 20 to 70 trillion miles). Finally, he varied the percentage of stars with a binary companion from 10% to 50% to 90%. Li assigned each star a randomly generated initial mass, starting position, and velocity, and simulated their interactions for 400 million years.

First, Li examined the simulations to identify stars with masses approximately equal to the Sun’s. From this group of solar-massed stars, Li found ones that left the cluster after 400 million years as a single star, after either forming alone or having lost a former companion star. He proposed that these stars were the most similar to the Sun and could thus host a simulated solar system.

Li then simulated the planets and their orbits as they would have formed on these potential host stars. To simplify this process, Li only simulated the 4 giant planets, Jupiter, Saturn, Uranus, and Neptune, which dominate planetary behavior in our solar system. He modeled these solar systems independently for 200 million years to ensure they would remain intact and used those that did for statistical analysis of the solar system’s past.

Overall, Li discovered 2 scenarios that could explain the solar system’s tilt. In the first, the primordial solar system was jostled by many distant neighboring stars in its cluster. This jostling tilts the planets’ orbits, but it does so randomly. Therefore, this scenario would make it unlikely for the planets to remain in the same orbital plane. It would also cause them to orbit the Sun faster and more chaotically than in our solar system.

In the second scenario, the Sun had a temporary companion star that it either formed with or briefly encountered before separating. When this occurred, the simulated planets’ orbits all tilted together. Stars that formed with a binary companion had a 10% chance of tilting their planets’ orbits by 6° or more, while stars that formed alone had a less than 0.1% chance. 

Li concluded that the solar system could have tilted as a result of interactions between the Sun and a temporary companion star within its parent cluster. However, he acknowledged that the model strongly depends on how closely a star passes by the Sun, since the closer a star passes, the more it disturbs the solar system. Despite this uncertainty, it’s possible that somewhere in space is the Sun’s twin or former neighbor that we haven’t seen in eons, and that’s what made our solar system crooked!

The post The Sun’s twin star may have tilted the planets’ orbits appeared first on Sciworthy.