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--------------------- 2653 - STARS - interesting stars?
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- Some stars move so fast they may leave their galaxies entirely, while theoretical stars may exist that stretch the boundaries of known physics.
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- The Big Ones like the red hyper giant 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
100 times that of the Earth.
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- This big star lies some 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 explosion.
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- At roughly 315 solar masses, RMC 136a1 is the most massive star known. But despite its hulking mass, the star stretches just 30 times the radius of our Sun. This star is beyond red-hot and even blue-hot; at 50,000 kelvins it is 'purple hot' with its radiation output peaking in the extreme ultraviolet spectrum.
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- 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.
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- The tiny stars are just larger than the planet Saturn This tiny star 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 was identified as it passed in front of its much larger companion.
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- Hypervelocity stars are stars that are 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.
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- However, last year astronomers found a hypervelocity star, a pulsating blue star, one bright enough to be studied in detail. Its origin can be traced back to the disk of our Milky Way. And it was probably ejected from our galaxy’s Carina-Sagittarius spiral arm.
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- The astronomers think this fast star was accelerated to such phenomenal speeds after a companion star exploded in a core-collapse supernova.
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- 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.
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- Thorne-Zytkow objects (TZOs), 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 supergiants. And they have unusually strong heavy-element and Lithium lines present in their spectra.
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- First hypothesized to exist by theoretical physics TZOs are thought to come from a scenario wherein a star going supernova “kicks” its leftover core, now a neutron star, into another star.
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- Thus, TZOs, if they exist at all, are quite rare. Astronomers do have one candidate TZO located in the Small Magellanic Cloud some 200,000 light-years away in the southern constellation of Tucana.
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- Finally, our Sun itself qualifies as a bit strange, even though it’s long been billed as an ordinary yellow dwarf star.
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------------------------------------ Why is the Sun odd?
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- It’s oddly massive. Even though it's in the middle of the range of possible sizes for stars (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.
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- 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.
- “No planetary system with a structure similar to ours has been found orbiting a Sun-like star, so far.”
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- As for the extreme stars above?
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- They are theoretically interesting but very unlikely to currently support life as we know it. The most amazing thing is that you are here to read about this particularly unlikely scenario.
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- March 6, 2020 2653
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--------------------- Sunday, March 15, 2020 --------------------
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