There Might Be an Entire Orbit, Filled with Asteroids that Came from Outside the Solar System

An illustration of the orbit of a Centaur asteroid. Credit: Namouni and Morais, NASA

Aliens could be all around us. Lurking on the edge, waiting to invade our solar system. Not little green creatures, but asteroids from other stars. That’s the conclusion of a new study published in the Monthly Notices of the Royal Astronomical Society.

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Gamma-Ray Telescopes Can Measure the Diameters of Other Stars

The VERITAS array, an air Cherenkov telescope designed to detect low-energy cosmic rays. Credit: VERITAS

In astronomy, the sharpness of your image depends upon the size of your telescope. When Galileo and others began to view the heavens with telescopes centuries ago, it changed our understanding of the cosmos. Objects such as planets, seen as points of light with the naked eye, could now be seen as orbs with surface features. But even under these early telescopes, stars still appeared as a point of light. While Galileo could see Jupiter or Saturn’s size, he had no way to know the size of a star.

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A Black Hole Popping Out of a Traversable Wormhole Should Give Off a Very Specific Signal in Gravitational Waves

Artist view of colliding neutron stars. Credit: ESO/L. Calçada/M. Kornmesser

Gravitational wave astronomy has changed the way we view the cosmos. In only a few years we have observed the collisions of black holes and neutron stars, confirming our theoretical understanding of these strange objects. But as gravitational wave astronomy matures, it will allow us to probe the very nature of space and time itself. While that day is a long way off, it hasn’t stopped the theory folks from dreaming up new discoveries. For example, how it might look if a black hole and a wormhole interact.

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What Shuts Down a Galaxy’s Star Formation?

Artist impression of 14 galaxies detected by ALMA as they appear in the very early, very distant universe. These galaxies are in the process of merging and will eventually form the core of a massive galaxy cluster. Credit: NRAO/AUI/NSF; S. Dagnello

In the 1920s, Edwin Hubble studied hundreds of galaxies. He found that they tended to fall into a few broad types. Some contained elegant spirals of bright stars, while others were spherical or elliptical with little or no internal structure. In 1926 he developed a classification scheme for galaxies, now known as Hubble’s Tuning Fork.

Hubble’s tuning fork diagram for galaxies. Credit: Edwin Hubble

When you look at Hubble’s scheme, it suggests an evolution of galaxies, beginning as an elliptical galaxy, then flattening and shifting into a spiral galaxy. While many saw this as a reasonable model, Hubble cautioned against jumping to conclusions. We now know ellipticals do not evolve into spirals, and the evolution of galaxies is complex. But Hubble’s scheme marks the beginning of the attempt to understand how galaxies grow, live, and die.

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Stars Like Our Sun Become Lithium Factories as They Die

This artist’s impression shows the red supergiant star. Using ESO’s Very Large Telescope Interferometer, an international team of astronomers have constructed the most detailed image ever of this, or any star other than the Sun. Credit: ESO/M. Kornmesser

In the beginning, the big bang created three elements: hydrogen, helium, and lithium. But it only produced a trace of lithium. For every lithium atom created, the big bang produced about 10 billion hydrogen atoms, and 3 billion helium atoms. The ratio of primordial elements is one of the triumphs of the big bang model. It predicts the ratio of hydrogen (H) and helium (4He) perfectly, and even works for the ratios of other isotopes, such as deuterium (2H) and helium-3 (3He). But it doesn’t work for lithium, and we aren’t sure why.

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Earth’s Magnetic Field is Changing Surprisingly Quickly

Visual simulation of the Earth's magnetic field. Credit: NASA Goddard Space Flight Center

If you’ve ever used a compass, you know that the magnetic needle always points North. Well, almost North. If you just happen to be out camping for the weekend, the difference doesn’t matter. For scientists studying the Earth’s interior, the difference is important. How Earth’s magnetic field changes over time give us clues about how our planet generates a magnetic field in the first place.

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Amateur Astronomers Find a Brand New Storm on Jupiter

JunoCam took this image during its eleventh close flyby of Jupiter on February 7, 2018. Image credit: NASA / JPL / SwRI / MSSS / David Marriott.
JunoCam took this image during its eleventh close flyby of Jupiter on February 7, 2018. Image credit: NASA / JPL / SwRI / MSSS / David Marriott.

There’s a new storm brewing on Jupiter. The most famous storm on Jupiter is the Great Red Spot, which has been active since at least the time of Galileo. Most of Jupiter’s storms don’t last for hundreds of years. They grow and fade just as they do on Earth. This latest storm was discovered by amateur astronomer Clyde Foster.

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Astronomers Might Have Seen a Star Just Disappear. Turning Straight to a Black Hole Without a Supernova

This illustration shows what the luminous blue variable star in the Kinman Dwarf galaxy could have looked like before its mysterious disappearance. Credit: ESO/L. Calçada

Large stars have violent deaths. As they run out of hydrogen to fuse, the star’s weight squeezes its core to make it increasingly hot and dense. The star fuses heavier elements in a last-ditch effort to keep from collapsing. Carbon to Silicon to Iron, each step generating heat and pressure. But soon it’s not enough. The fusion even heavier elements don’t give the star more energy, and the core quickly collapses. The protons and neutrons of nuclei collide so violently that the resulting shock wave rips the star about. The outer layers of the star are thrown outward, becoming a brilliant supernova. For a brief time, the star shines brighter than its entire galaxy, and its core collapses into a neutron star or black hole. It was thought that all large stars end with a supernova, but new research finds that might not be the case.

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Astronomers Just Detected Either the Least Massive Black Hole, or a Strange and Massive Neutron Star

This graphic shows the latest merger compared to known black holes and neutron stars. Credit: LIGO-Virgo/ Frank Elavsky & Aaron Geller (Northwestern)

Black holes are the ultimate limit of gravitational collapse. Bring enough mass into a small enough volume, and its own weight will squeeze the mass into oblivion. All that remains is a warped pocket of space that it can trap anything that strays too close, even light.

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A Repeating Fast Radio Burst Has Been Found. It Flares for 4 Days and then Remains Silent for 12 Days

Artist’s impression of a fast radio burst traveling through space and reaching Earth. Credit: ESO/M. Kornmesser

Five hundred million light-years from Earth, there is a deeply unusual object. It is radio silent for 12 days, then erupts in bright radio bursts. These fast radio bursts occur randomly over four days, then the object goes silent for another 12 days. Astronomers have observed this object for 500 days, and the pattern always repeats, like clockwork. We still aren’t sure what the object is.

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