Dark matter makes up the vast majority of matter in the universe, but we can’t see it. At least, not directly. Whatever the dark matter is, it must interact with everything else in the universe through gravity, and astronomers have found that if too much dark matter collects inside of red giant stars, it can potentially cut their lifetimes in half.
When stars like our sun near the end of their lives, they stop fusing hydrogen in their cores. Instead, the fusion takes place in a shell surrounding a dense core of inert helium – the leftover ash from that nuclear reaction. Over the course of hundreds of millions of years, that core contracts (after all, there’s nothing inside of it generating energy to keep it inflated), heating it up.
Simultaneously, because of the increased core temperature, the rest of the star swells, ballooning to ridiculous proportions as a red giant star.
Astronomers can estimate the lifetimes of red giant stars by studying the complex physics of the core, tracing how long the helium can continue to heat until it reaches the critical threshold needed for it to undergo its own nuclear fusion, triggering the final end stages of the star.
It’s a pretty straightforward astrophysical calculation.
That is, it’s pretty straightforward unless something jams up the works.
A Dark Heart
Completely unrelated to red giants, astronomers are currently puzzling over the nature of dark matter, a substance that comprises roughly 80% of all the matter in the universe, yet is completely invisible. We’re not exactly sure what dark matter is, but we’re pretty confident that it is some sort of particle, as yet completely unknown to the standard model of particle physics.
Whatever the dark matter is made of, it must interact with normal matter through gravity, because that’s how we’ve been able to detect it so far. Beyond that, it may be possible for dark matter to form clumps, or regions of high density inside normal-matter objects like stars and planets.
Astronomers have already investigated the consequences of pooling dark matter into the hearts of normal stars, but new research has revealed what happens to red giant stars near the end of their lives.
Short version: it’s not pretty.
According to a paper recently appearing on the preprint journal arXiv, When too much dark matter sits inside a giant star, it causes the helium core to contract more than it normally would. That increased density raises the temperatures, which in turn raises the luminosity, which goes on to make the future evolution of the star that much shorter.
The effects are dramatic. If dark matter makes up a mere 10% of the mass of the red giant core, the temperatures jump by 10%, the luminosity doubles, and the lifetime of the red giant is cut in half.
We don’t know how much dark matter – if any – sits inside red giants, but future studies of this population of dying stars may reveal clues to one of the most enigmatic substances in the universe.
Water discovered on moon's sunlit surface – CityNews Toronto
NASA finds definitive evidence of water on moon’s surface – Global News
The moon lacks the bodies of liquid water that are a hallmark of Earth but scientists said on Monday lunar water is more widespread than previously known, with water molecules trapped within mineral grains on the surface and more water perhaps hidden in ice patches residing in permanent shadows.
While research 11 years ago indicated water was relatively widespread in small amounts on the moon, a team of scientists is now reporting the first unambiguous detection of water molecules on the lunar surface. At the same time, another team is reporting that the moon possesses roughly 15,000 square miles (40,000 square kilometers) of permanent shadows that potentially could harbor hidden pockets of water in the form of ice.
Water is a precious resource and a relatively plentiful lunar presence could prove important to future astronaut and robotic missions seeking to extract and utilize water for purposes such as a drinking supply or a fuel ingredient.
A team led by Casey Honniball of NASA’s Goddard Space Flight Center in Maryland detected molecular water on the lunar surface, trapped within natural glasses or between debris grains. Previous observations have suffered from ambiguity between water and its molecular cousin hydroxyl, but the new detection used a method that yielded unambiguous findings.
The only way for this water to survive on the sunlit lunar surfaces where it was observed was to be embedded within mineral grains, protecting it from the frigid and foreboding environment. The researchers used data from the SOFIA airborne observatory, a Boeing 747SP aircraft modified to carry a telescope.
“A lot of people think that the detection I’ve made is water ice, which is not true. It’s just the water molecules – because they’re so spread out they don’t interact with each other to form water ice or even liquid water,” Honniball said.
NASA spacecraft gets sample from nearby asteroid Bennu
The second study, also published in the journal Nature Astronomy, focused upon so-called cold traps on the moon, regions of its surface that exist in a state of perpetual darkness where temperatures are below about negative 260 degrees Fahrenheit (negative 163 degrees Celsius). That is cold enough that frozen water can remain stable for billions of years.
Using data from NASA’s Lunar Reconnaissance Orbiter spacecraft, researchers led by planetary scientist Paul Hayne of the University of Colorado, Boulder detected what may be tens of billions of small shadows, many no bigger than a small coin. Most are located in the polar regions.
“Our research shows that a multitude of previously unknown regions of the moon could harbor water ice,” Hayne said. “Our results suggest that water could be much more widespread in the moon’s polar regions than previously thought, making it easier to access, extract and analyze.”
NASA is planning a return of astronauts to the moon, a mission envisioned as paving the way for a later journey carrying a crew to Mars. Accessible sources where water can be harvested on the moon would beneficial to those endeavors.
“Water is not just constrained to the polar region. It’s more spread out than we thought it was,” Honniball said.
Another mystery that remains unsolved is the source of the lunar water.
“The origin of water on the moon is one of the big-picture questions we are trying to answer through this and other research,” Hayne said. “Currently, the major contenders are comets, asteroids or small interplanetary dust particles, the solar wind, and the moon itself through outgassing from volcanic eruptions.”
NASA aiming for 2024 Moon landing
Earth is a wet world, with vast salty oceans, large freshwater lakes and ice caps that serve as water reservoirs.
“As our closest planetary companion, understanding the origins of water on the moon can also shed light on the origins of Earth’s water – still an open question in planetary science,” Hayne added.
© 2020 Reuters
A Full Blue Moon Will Rise Over Metro Vancouver Skies This Halloween – 604 Now
Sky watchers can take in the incredible wonder of the Hunter’s Blue Moon, which will be making a rare appearance this Halloween.
The full blue moon will be visible over North American skies on Oct. 31st. The lunar event is even more special considering it means there are two full moons in October—the Harvest Moon at the beginning of the month and the Hunter’s Moon at the end.
Typically, there is only one full moon per month. And the second full moon in a month is even more magical—because it’s a blue moon.
According to the Old Farmer’s Almanac, the timing of the full blue moon rising on Halloween night is also extremely rare.
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“Despite all the creative Halloween full moon pictures, a full moon occurring on Halloween is not a common occurrence and only happens every 18 to 19 years,” the website reads.
The Hunter’s Blue Moon also rises right before the end of Daylight Saving Time.
It’s at the perfect timing—with Halloween landing on a Saturday this year and people getting an extra hour of sleep on Sunday, as we turn back the clocks.
Hunter’s Blue Moon
When: Visible across North American skies on Saturday, Oct. 31st, 2020
For more things to do and see in Metro Vancouver and beyond, check out our Travel & Outdoors section.
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