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'Ask a Spaceman' Seeks Out the Elusive Quark Star in Finale

After guiding us across the universe, astrophysicist and Space.com columnist Paul Sutter closes his basic astronomy series this week by looking at the arguments for and against the existence of quark stars.

In Episode 12 of the Facebook Watch series "Ask a Spaceman," Sutter continues to explore the topic of these stars, finishing a miniseries that began with Episode 10 and Episode 11. Scientists haven't observed quark stars yet, but the objects may exist. Such a star would be a leftover remnant of a star that exploded and would be packed even more densely than a neutron star; the quark star would have such strong gravity that fundamental particles in the core, such as protons and neutrons, would break down into their constituent parts, called quarks.

"Is there any astrophysical scenario at all that enables them [quark stars] to appear in our universe?" Sutter asks in the new episode. At first, he suggests there might be some things we categorized a dwarf stars that are more dense and massive than what physics would suggest. So, maybe we have seen quark stars, but we can't tell the difference between a quark star and a neutron star — they look too much alike, Sutter says. [Supernova Fail: Giant Dying Star Collapses Straight into Black Hole]

Or perhaps quark stars are "out there" but invisible for some reason, because there appears to be a gap between the most-massive neutron star we see and the least-massive black hole we observe. (The "sweet spot" for the existence of a quark star appears to be two to three times the mass of the sun, Sutter says.) Further, perhaps we haven't been doing telescopic astronomy long enough to see quark stars, which might be extremely rare, he says. 

It's also difficult to predict how to put a quark star together. As Sutter explained in Episode 11, quarks come in six "flavors": up, down, top, bottom, strange and charm. Protons and neutrons are made up of up and down quarks, but if you were to build a quark star out of these quarks, that star would be unstable. Quark stars would stabilize with the addition of strange quarks, but strange quarks are not very common in the universe. It's unclear if the universe has produced enough strange quarks to make quark stars possible, Sutter said.

Sutter closes the latest episode by suggesting about quark stars, "Maybe nature just doesn't make them, because nature isn't as interested as we are." To learn more about quark stars, you can check out Sutter's column about them.

To see all the episodes of the "Ask a Spaceman" Facebook Watch series, check out (and maybe "like") the Facebook page for the show. Sutter also responds to reader questions in every episode. Check the page to learn more about past topics the show has covered, such as the Big Bang, Pluto and galaxy collisions.

Sutter is a cosmologist at The Ohio State University and chief scientist at Columbus Ohio's Center of Science and Industry. He has a long-running podcast, also called "Ask a Spaceman." You can catch all past episodes of that podcast here.

Follow us on Twitter @Spacedotcom and on Facebook. Original article on Space.com.

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