-
------------------------ 2601 - ASTRONOMY - extremes noted in 2020?
-
- Astronomy finds that 70 percent of all stars in the universe are tiny red dwarfs, so faint and so dim they are hard to find. But this “average star” lies in the middle of a true breadth and sheer weirdness of the universe’s stellar extremes.
-
- The red hypergiant star “UY Scuti” is the largest star known. It has a radius about 1,700 times larger than the Sun. For comparison, the Sun has a radius about 110 times that of Earth. This hyper star lies 5,100 light-years away in the small southern constellation of Scutum. It’s much like the red supergiant Betelgeuse but some three times larger and, like Betelgeuse, it’s expected to end life as a supernova.
-
- RMC 136a1, the most massive star known. It is 315 solar masses. But despite its hulking mass, the star stretches just 30 times the radius of our Sun. It’s part of a cluster of very hot, bright stars at the center of R136, the central concentration of stars in NGC 2070, a star cluster in the Large Magellanic Cloud’s Tarantula Nebula.
-
- This massive star is beyond red-hot and even blue-hot; at 50,000 Kelvin it is 'purple hot' with its radiation output peaking in the extreme ultraviolet spectrum. Its future is as a likely supernova although one of sufficient progenitor mass that it will leave behind a black hole rather than a neutron star.
-
- The smallest star is just larger than the planet Saturn. “EBLM J0555-57Ab” has just enough mass to enable the fusion of hydrogen nuclei into helium. Located about 600 light-years away and part of a binary star system, 57 Ab was identified as it passed in front of its much larger companion.
-
- The Fastest stars are the hypervelocity stars speeding through our galaxy at such a high rate of speed that most will eventually break free from the Milky Way. Until recently, scientists thought the only way stars could reach such speeds was through the interaction of a binary star system with the supermassive black hole at the center of our galaxy.
-
- The hypervelocity star “PG 1610+062” was accelerated to such phenomenal speeds after a companion star exploded in a core-collapse supernova. Alternatively, the binary pair could have gained its velocity from gravitational interactions with young and dense stellar clusters. In such scenarios where two stars are locked in orbit around each other, their interaction with other stars in dense clusters can catapult the less massive star in the binary system into a hypervelocity trajectory.
-
- The “Thorne-Zytkow objects’ ,“TZO stars“, which exist only in theory thus far, are thought to form when a compact neutron star is surrounded by a large, diffuse envelope of hydrogen gas. Supergiant TZOs are predicted to be almost identical in appearance to red super giants. And they have unusually strong heavy-element and Lithium lines present in their spectra.
-
- First hypothesized to exist by theoretical physicists TZOs are thought to come from a scenario wherein a star going supernova “kicks” its leftover core, now a neutron star, into another star. Astronomers do have one candidate TZO, called “HV2112“, located in the Small Magellanic Cloud some 200,000 light-years away in the southern constellation of Tucany.
-
- Finally our Sun itself, which we sometimes forget is a star, qualifies as a bit strange, even though it’s long been billed as an ordinary yellow dwarf star. Why is the Sun odd? It’s oddly massive. Even though it's in the middle of the range of possible sizes for stars Star’s range is sizes from roughly an eighth of a solar mass to some 100 solar masses. More than three quarters of all stars are less massive than our Sun.
-
- And although half of all solar-type stars are thought to have a companion, our Sun apparently never did. In comparison to other stars in its spectral range, the Sun is photo -metrically pretty stable. That means the Sun’s brightness doesn't vary by much ,perhaps one factor key to the evolution of life on Earth.
-
- So far no planetary system with a structure similar to ours has been found orbiting a Sun-like star. So, maybe that is an extreme case in its own rite. How rare is it that you are even here and reading this? You can your lucky stars you got this one.
-
- January 31, 2020 2601
----------------------------------------------------------------------------------------
----- Comments appreciated and Pass it on to whomever is interested. ----
--- Some reviews are at: -------------- http://jdetrick.blogspot.com -----
-- email feedback, corrections, request for copies or Index of all reviews
--- to: ------ jamesdetrick@comcast.net ------ “Jim Detrick” -----------
- https://plus.google.com/u/0/ -- www.facebook.com -- www.twitter.com
--------------------- Friday, January 31, 2020 --------------------
-----------------------------------------------------------------------------------------
No comments:
Post a Comment