A New Class of ExoPlanet

Artist's illustration of a half-rock, half-water world orbiting a red dwarf star. 

(Image credit: Pilar Montañés (@pilar.monro))

A new type of exoplanet — one made half of rock and half of water — has been discovered around the most common stars in the universe, which may have great consequences in the search for life in the cosmos, researchers say.


Red dwarfs are the most common type of star, making up more than 70% of the universe's stellar population. These stars are small and cold, typically about one-fifth as massive as the sun and up to 50 times dimmer.

The fact that red dwarfs are so very common has made scientists wonder if they might be the best chance for discovering planets that can possess life as we know it on Earth. For example, in 2020, astronomers that discovered Gliese 887, the brightest red dwarf in our sky at visible wavelengths of light, may host a planet within its habitable zone, where surface temperatures are suitable to host liquid water.

However, whether the worlds orbiting red dwarfs are potentially habitable remains unclear, in part because of the lack of understanding that researchers have about these worlds' composition. Previous research suggested that small exoplanets — ones less than four times Earth's diameter — orbiting sun-like stars are generally either rocky or gassy, possessing either a thin or thick atmosphere of hydrogen and helium.


In the new study, astrophysicists sought to examine the compositions of exoplanets around red dwarfs. 

They focused on small worlds found around closer — and thus brighter and easier to inspect — red dwarfs observed by NASA's Transiting Exoplanet Survey Satellite (TESS).  READ MORE...

Backwards in Time

A wild new theory suggests there may be another "anti-universe," running backward in time prior to the Big Bang.  The idea assumes that the early universe was small, hot and dense — and so uniform that time looks symmetric going backward and forward.

If true, the new theory means that dark matter isn't so mysterious; it's just a new flavor of a ghostly particle called a neutrino that can only exist in this kind of universe. And the theory implies there would be no need for a period of "inflation" that rapidly expanded the size of the young cosmos soon after the Big Bang.

If true, then future experiments to hunt for gravitational waves, or to pin down the mass of neutrinos, could answer once and for all whether this mirror anti-universe exists.

Preserving symmetry
Physicists have identified a set of fundamental symmetries in nature. The three most important symmetries are: charge (if you flip the charges of all the particles involved in an interaction to their opposite charge, you'll get the same interaction); parity (if you look at the mirror image of an interaction, you get the same result); and time (if you run an interaction backward in time, it looks the same).

Physical interactions obey most of these symmetries most of the time, which means that there are sometimes violations. But physicists have never observed a violation of a combination of all three symmetries at the same time. If you take every single interaction observed in nature and flip the charges, take the mirror image, and run it backward in time, those interactions behave exactly the same.

This fundamental symmetry is given a name: CPT symmetry, for charge (C), parity (P) and time (T).

In a new paper recently accepted for publication in the journal Annals of Physics, scientists propose extending this combined symmetry. Usually this symmetry only applies to interactions — the forces and fields that make up the physics of the cosmos. But perhaps, if this is such an incredibly important symmetry, it applies to the whole entire universe itself. In other words, this idea extends this symmetry from applying to just the "actors" of the universe (forces and fields) to the "stage" itself, the entire physical object of the universe.

Creating dark matter
We live in an expanding universe. This universe is filled with lots of particles doing lots of interesting things, and the evolution of the universe moves forward in time. If we extend the concept of CPT symmetry to our entire cosmos, then our view of the universe can't be the entire picture.

Instead, there must be more. To preserve the CPT symmetry throughout the cosmos, there must be a mirror-image cosmos that balances out our own. This cosmos would have all opposite charges than we have, be flipped in the mirror, and run backward in time. Our universe is just one of a twin. Taken together, the two universes obey CPT symmetry.

The study researchers next asked what the consequences of such a universe would be.  They found many wonderful things.  READ MORE...

Universe Expanding Faster Than Expected

This image from the Hubble Space Telescope features the spiral galaxy Markarian 1337, which is roughly 120 million light-years away from Earth. In 2006, astronomers saw a certain kind of supernova explode in this galaxy, providing researchers with some of the data nee...IMAGE BY ESA/HUBBLE & NASA, A. RIESS ET AL.

The latest measurements with the Hubble Space Telescope suggest the universe is expanding faster than scientists' models predict—a hint that some unknown ingredient could be at work in the cosmos.

It’s one of the biggest puzzles in modern astronomy: Based on multiple observations of stars and galaxies, the universe seems to be flying apart faster than our best models of the cosmos predict it should. Evidence of this conundrum has been accumulating for years, causing some researchers to call it a looming crisis in cosmology.

Now a group of researchers using the Hubble Space Telescope has compiled a massive new dataset, and they’ve found a-million-to-one odds that the discrepancy is a statistical fluke. In other words, it’s looking even more likely that there’s some fundamental ingredient of the cosmos—or some unexpected effect of the known ingredients—that astronomers have yet to pin down.

“The universe seems to throw a lot of surprises at us, and that’s a good thing, because it helps us learn,” says Adam Riess, an astronomer at Johns Hopkins University who led the latest effort to test the anomaly.

The conundrum is known as the Hubble tension, after astronomer Edwin Hubble. In 1929 he observed that the farther a galaxy is from us, the faster it recedes—an observation that helped pave the way toward our current notion of the universe starting with the big bang and expanding ever since.

Researchers have tried to measure the universe’s current rate of expansion in two primary ways: by measuring distances to nearby stars, and by mapping a faint glow dating back to the infant universe. These dual approaches provide a way to test our understanding of the universe across more than 13 billion years of cosmic history. The research has also uncovered some key cosmic ingredients, such as “dark energy,” the mysterious force thought to be driving the universe’s accelerating expansion.

But these two methods disagree on the universe’s current expansion rate by about 8 percent. That difference might not sound like much, but if this discrepancy is real, it means the universe is now expanding faster than even dark energy can explain—implying some breakdown in our accounting of the cosmos.  READ MORE...