Jan 5, 2021 09:04 PM
(This post was last modified: Jan 6, 2021 05:01 PM by C C.)
This ‘Unusual Star’ Is Unlike Anything Astronomers Have Seen Before
https://gizmodo.com/this-unusual-star-is...1845994482
EXCERPT: Theoretical modeling suggests this object is the result of two white dwarfs coming together. The heavier white dwarf pulled matter away from the lighter companion, eventually triggering a supernova explosion—but one too weak to destroy the system entirely. At the same time, however, the explosion was still strong enough to eject significant amounts of material. Oskinova and her colleagues believe the neon-rich nebula is that ejected material, and that a cohesive object managed to survive the the weak supernova, allowing it to develop into the star we see today. At least, according to this scenario.
“IRAS 00500+6713 is a newly discovered type of celestial object. We are not aware of other objects with similar properties.” said Oskinova. “We can call it a very unusual star.” The team wasn’t able to determine the object’s mass, but its high luminosity is consistent with an object heavier than 1.4 solar masses, which is the upper limit for a white dwarf (any heavier and it transforms into a neutron star).
Schwab said the new X-ray data and subsequent analysis improves our knowledge of the object’s chemical composition. “The results suggest the involvement of an oxygen-neon white dwarf and the occurrence of carbon fusion, both of which strengthen the case that this particular object is a massive remnant of the merger of two white dwarfs,” he explained. Future work [...] will be required to fully understand the nature of the explosion that produced the unusual star... (MORE - details)
Is there more than one dark energy?
https://www.space.com/multiple-dark-ener...ing-theory
INTRO: We don't know what's behind dark energy, the name we give to the current era of accelerated expansion in the universe. Many theorists favor some sort of quantum field as the driver of dark energy, but these ideas are hard to reconcile with insights from string theory. But new research proposes a radical solution: What if there is more than one cosmological agent for dark energy? This mixture would have strange effects in our universe, making it potentially detectable with upcoming surveys... (MORE)
The Interior of Enceladus Looks Really Great for Supporting Life
https://www.universetoday.com/149496/the...ting-life/
INTRO: When NASA’s Voyager spacecraft visited Saturn’s moon Enceladus, they found a body with young, reflective, icy surface features. Some parts of the surface were older and marked with craters, but the rest had clearly been resurfaced. It was clear evidence that Enceladus was geologically active. The moon is also close to Saturn’s E-ring, and scientists think Enceladus might be the source of the material in that ring, further indicating geological activity.
Since then, we’ve learned a lot more about the frigid moon. It almost certainly has a warm and salty subsurface ocean below its icy exterior, making it a prime target in the search for life. The Cassini spacecraft detected molecular hydrogen—a potential food source for microbes—in plumes coming from Enceladus’ subsurface ocean, and that energized the conversation around the moon’s potential to host life.
Now a new paper uses modelling to understand Enceladus’ chemistry better. The team of researchers behind it says that the subsurface ocean may contain a variety of chemicals that could support a diverse community of microbes. As far as the search for life elsewhere in the Solar System goes, Enceladus checks many boxes. Saturn’s sixth-largest moon is about 500 km (310 mi) in diameter and seems to have a global ocean buried under a sheet of ice. And that ocean is likely warm and salty and contains some interesting chemicals. According to the new research, there are several pathways among these chemicals that could support life.
The title of the paper is Oxidation processes diversify the metabolic menu on Enceladus... (MORE)
Jupiter Is Bigger Than Some Stars, So Why Didn't We Get a Second Sun?
https://www.sciencealert.com/why-isn-t-jupiter-a-star
INTRO: The smallest known main-sequence star in the Milky Way galaxy is a real pixie of a thing. It's called EBLM J0555-57Ab, a red dwarf 600 light-years away. With a mean radius of around 59,000 kilometres, it's just a smidge bigger than Saturn. That makes it the tiniest known star to support hydrogen fusion in its core, the process that keeps stars burning until they run out of fuel.
In our Solar System, there are two objects larger than this teeny star. One is the Sun, obviously. The other is Jupiter, like a giant scoop of ice cream, coming in with a mean radius of 69,911 kilometres. So why is Jupiter a planet and not a star?
The short answer is simple: Jupiter doesn't have enough mass to fuse hydrogen into helium. EBLM J0555-57Ab is about 85 times the mass of Jupiter, about as light as a star can be - if it were any lower, it would not be able to fuse hydrogen either. But if our Solar System had been different, could Jupiter have ignited into a star?
Jupiter and the Sun are more alike than you know. The gas giant may not be a star, but Jupiter is still a Big Deal. Its mass is 2.5 times that of all the other planets combined. It's just that, being a gas giant, it has really low density: around 1.33 grams per cubic centimetre; Earth's density, at 5.51 grams per cubic centimetre, is just over four times higher than that of Jupiter.
But it's interesting to note the similarities between Jupiter and the Sun. The Sun's density is 1.41 grams per cubic centimetre. And the two objects are very compositionally similar. By mass, the Sun is about 71 percent hydrogen and 27 percent helium, with the rest being made up of trace amounts of other elements. Jupiter by mass is about 73 percent hydrogen and 24 percent helium.
It's for this reason that Jupiter is sometimes called a failed star. But it's still unlikely that, left to the Solar System's own devices, Jupiter would even become close to being a star. Stars and planets, you see, are born through two very different mechanisms... (MORE)
https://gizmodo.com/this-unusual-star-is...1845994482
EXCERPT: Theoretical modeling suggests this object is the result of two white dwarfs coming together. The heavier white dwarf pulled matter away from the lighter companion, eventually triggering a supernova explosion—but one too weak to destroy the system entirely. At the same time, however, the explosion was still strong enough to eject significant amounts of material. Oskinova and her colleagues believe the neon-rich nebula is that ejected material, and that a cohesive object managed to survive the the weak supernova, allowing it to develop into the star we see today. At least, according to this scenario.
“IRAS 00500+6713 is a newly discovered type of celestial object. We are not aware of other objects with similar properties.” said Oskinova. “We can call it a very unusual star.” The team wasn’t able to determine the object’s mass, but its high luminosity is consistent with an object heavier than 1.4 solar masses, which is the upper limit for a white dwarf (any heavier and it transforms into a neutron star).
Schwab said the new X-ray data and subsequent analysis improves our knowledge of the object’s chemical composition. “The results suggest the involvement of an oxygen-neon white dwarf and the occurrence of carbon fusion, both of which strengthen the case that this particular object is a massive remnant of the merger of two white dwarfs,” he explained. Future work [...] will be required to fully understand the nature of the explosion that produced the unusual star... (MORE - details)
Is there more than one dark energy?
https://www.space.com/multiple-dark-ener...ing-theory
INTRO: We don't know what's behind dark energy, the name we give to the current era of accelerated expansion in the universe. Many theorists favor some sort of quantum field as the driver of dark energy, but these ideas are hard to reconcile with insights from string theory. But new research proposes a radical solution: What if there is more than one cosmological agent for dark energy? This mixture would have strange effects in our universe, making it potentially detectable with upcoming surveys... (MORE)
The Interior of Enceladus Looks Really Great for Supporting Life
https://www.universetoday.com/149496/the...ting-life/
INTRO: When NASA’s Voyager spacecraft visited Saturn’s moon Enceladus, they found a body with young, reflective, icy surface features. Some parts of the surface were older and marked with craters, but the rest had clearly been resurfaced. It was clear evidence that Enceladus was geologically active. The moon is also close to Saturn’s E-ring, and scientists think Enceladus might be the source of the material in that ring, further indicating geological activity.
Since then, we’ve learned a lot more about the frigid moon. It almost certainly has a warm and salty subsurface ocean below its icy exterior, making it a prime target in the search for life. The Cassini spacecraft detected molecular hydrogen—a potential food source for microbes—in plumes coming from Enceladus’ subsurface ocean, and that energized the conversation around the moon’s potential to host life.
Now a new paper uses modelling to understand Enceladus’ chemistry better. The team of researchers behind it says that the subsurface ocean may contain a variety of chemicals that could support a diverse community of microbes. As far as the search for life elsewhere in the Solar System goes, Enceladus checks many boxes. Saturn’s sixth-largest moon is about 500 km (310 mi) in diameter and seems to have a global ocean buried under a sheet of ice. And that ocean is likely warm and salty and contains some interesting chemicals. According to the new research, there are several pathways among these chemicals that could support life.
The title of the paper is Oxidation processes diversify the metabolic menu on Enceladus... (MORE)
Jupiter Is Bigger Than Some Stars, So Why Didn't We Get a Second Sun?
https://www.sciencealert.com/why-isn-t-jupiter-a-star
INTRO: The smallest known main-sequence star in the Milky Way galaxy is a real pixie of a thing. It's called EBLM J0555-57Ab, a red dwarf 600 light-years away. With a mean radius of around 59,000 kilometres, it's just a smidge bigger than Saturn. That makes it the tiniest known star to support hydrogen fusion in its core, the process that keeps stars burning until they run out of fuel.
In our Solar System, there are two objects larger than this teeny star. One is the Sun, obviously. The other is Jupiter, like a giant scoop of ice cream, coming in with a mean radius of 69,911 kilometres. So why is Jupiter a planet and not a star?
The short answer is simple: Jupiter doesn't have enough mass to fuse hydrogen into helium. EBLM J0555-57Ab is about 85 times the mass of Jupiter, about as light as a star can be - if it were any lower, it would not be able to fuse hydrogen either. But if our Solar System had been different, could Jupiter have ignited into a star?
Jupiter and the Sun are more alike than you know. The gas giant may not be a star, but Jupiter is still a Big Deal. Its mass is 2.5 times that of all the other planets combined. It's just that, being a gas giant, it has really low density: around 1.33 grams per cubic centimetre; Earth's density, at 5.51 grams per cubic centimetre, is just over four times higher than that of Jupiter.
But it's interesting to note the similarities between Jupiter and the Sun. The Sun's density is 1.41 grams per cubic centimetre. And the two objects are very compositionally similar. By mass, the Sun is about 71 percent hydrogen and 27 percent helium, with the rest being made up of trace amounts of other elements. Jupiter by mass is about 73 percent hydrogen and 24 percent helium.
It's for this reason that Jupiter is sometimes called a failed star. But it's still unlikely that, left to the Solar System's own devices, Jupiter would even become close to being a star. Stars and planets, you see, are born through two very different mechanisms... (MORE)