Starship Asterisk*

Ann wrote: ↑Fri Apr 26, 2019 5:23 pm
Theta has stolen a lot of mass from its hapless companion, and all that fresh hydrogen that has been dumped on Theta acts as a youth elixir that allows this brash star to pose as an energetic baby. And next time you read about an impossibly massive and hot star, ask yourself if this star couldn't be a blue straggler.

https://www.etymonline.com/word/straggle wrote:
<<straggle (v.) early 15c., "to wander from the proper path, stray, to rove from one's companions," perhaps from a Scandinavian source (compare dialectal Norwegian stragla "to walk laboriously"). Specifically of soldiers, "be dispersed, be apart from the main body," from 1520s.>>

NCTom wrote: ↑Fri Apr 26, 2019 12:02 pm Thanks, Ann, for the explanation. You definitely keep the science from getting boring!

Wikipedia wrote:

IC 2602 is likely about the same age as the open cluster IC 2391,[4] which has a lithium depletion boundary age of 50 million years old,[5] though the accepted age from its HR-Diagram is about 13.7 million years.

Wikipedia wrote:

Theta Carinae is a single-lined spectroscopic binary with a 2.2 day period

The estimated age of the pair is 4 million years

and it appears much younger than the surrounding IC 2602 cluster.

Jim Kaler wrote:

Theta Car is in fact TOO bright. Clusters, born with an intact mass sequence of hydrogen-burners, die from the top down, high mass stars going first. The top of IC 2602's is considerably less massive than Theta. From the maximum general mass remaining, the cluster's age is set at 34 million years. Yet Theta is anomalously dated to be just a couple million years old.

Jim Kaler wrote:

Algol is famed first as a prototype of the class of eclipsing double stars, of which thousands are known. (...) But Algol is equally famed for the "Algol paradox." The higher the mass of a star, the shorter its lifetime, as its fuel is used so much faster. The companion to Algol is the dying giant star. Yet carrying but 0.81 solar masses, it is the LESS massive of the two (the B star weighing in at 3.7 solar).

The only explanation is that the dim companion has lost a great deal of mass. The two stars are so close together, separated by only five percent the distance between the Earth and the Sun, that the brighter smaller star produces tides in the larger one. Matter then flows in from the large one (at a rate of around two hundred- millionths of a solar mass per year) to the small bright one, the effect directly observed through the stellar spectrum as the K giant is being stripped nearly to its core.

Wikipedia wrote about Theta Carina:

In this spectroscopic system, the primary star is probably a blue straggler, which is an unusual type of star created by merging or the interaction between two or more stars. The source of the mass transfer is likely to be the less massive secondary companion, and what is now is the primary star was probably originally the less massive component. The estimated age of the pair is 4 million years,[7] and it appears much younger than the surrounding IC 2602 cluster.[6]

The primary star is about 15 solar masses (M☉) and five solar radii (R☉).[6] Theta Carinae has an intensely hot outer radiating envelope with an effective surface temperature of 31,000 K.[9] Once the primary reaches around 11 million years old, the star will expand and will begin to transferring its outer surface mass back to its companion. Little is known about the companion star, but it is likely an F-type star with a luminosity less than 1% of the primary.

Ann wrote: ↑Fri Apr 26, 2019 8:04 am

Evolutionary path of a solar-mass star. Illustration: Lithopsian.

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The fascinating thing about Gacrux is that it is an M-class giant, not one of the dime-a-dozen K-class giants like Pollux or Dubhe, and not one of the brilliant M-class supergiants, like Betelgeuse or Antares.

When the Sun has reached the top of the red giant branch, its core has grown hot enough that it can start fusing its core helium into carbon and oxygen. When this happens, the Sun's outer layers shrink, and the Sun will descend from its beastly red glory into the red clump stage of its evolutionary path. The red clump is where you will find all these boring K-type giants. Look at this picture of the Beehive Cluster, M44, by Bob Franke. See those weakly colored pale, pale orange stars? They are the modest red clump K-type core helium burning stars. Yawn.

When the Sun has reached its red clump stage and started fusing helium to oxygen and carbon in its core, it is going to stay in the red clump region for a relatively long time. The fact that the helium fusion can be produced by modest stars like the Sun, and that it can keep going for a relatively long time, is the reason why we see so many K-class pale orange giants everywhere in the sky. Because the red clump stars are K-class stars, while (perhaps all) the red giant branch stars and all the AGB stars are M-class ones.

Right. But when the Sun has exhausted its core helium, it will begin its second ascent, on the Asymptotic Giant Branch, which will take it to even brighter and redder and more monstrously swollen heights. And after reaching the top of the AGB branch, the Sun will get the Mira hiccups. And then, planetary nebula and white dwarf death is near for the Sun.

https://en.wikipedia.org/wiki/Nutty_Professor_II:_The_Klumps wrote:

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<<After finding success with a DNA restructuring formula, Sherman Klump has created another formula which enables those who take it to find the Fountain of Youth. He has also met and fallen in love with a colleague, Denise Gaines, who has developed a method to isolate genetic material and later becomes his fiancée. Together, their work has enabled Wellman College to receive a $150 million award from a pharmaceutical firm to the excitement of Dean Richmond, who has grown to adore and respect Sherman. Despite his good fortune, Sherman has a major problem: the personality of his vanquished alter ego, Buddy Love, is still ingrained inside him and causes him to act out in the same crass manner Buddy does.

Sherman quickly works on a newer, much more potent formula while his mental faculties allow him to. Richmond confronts him about Buddy's actions, believing the two are working together. He leaves with Richmond and a tennis ball and head to the competing firm. Meanwhile, a worried Denise discovers what has happened and that Sherman's brain damage has progressed to almost eighty percent. Enlisting the help of Sherman's father Cletus, Denise goes after him. Sherman takes advantage of the canine DNA that crossed with Buddy's, and uses the tennis ball to play fetch. The ball is covered with the new formula, which takes Buddy back to an infantile state and eventually to a glowing mass of genetic material for Sherman to suck the genetic material back into his body through a straw, thus putting his DNA back together and returning him to normal. However, as Sherman chases what is left of Buddy, the glowing mass evaporates and thus Sherman cannot restore his intelligence.

Denise and Cletus arrive too late to save him, and seeing what has happened to Sherman, Denise breaks into tears. As they go to leave, Sherman takes a look at a fountain and remarks that it is "pretty". Seeing that the water is glowing, Denise realizes that the genetic material has reconstituted and that if Sherman drinks the water before it dissipates, he will be restored to normal. Sherman eventually drinks the water with the help of Denise and Cletus, and thus he is able to get his genetic makeup back in proper order.>>

Jim Kaler wrote about Gacrux:

Gacrux's evolutionary -- ageing -- status is uncertain. With a mass perhaps three times solar or less, it may well have given up not just hydrogen fusion in its core (which it must do to become a giant in the first place), but may also have gone through its core helium-fusion stage. If that is the case, Gacrux is in the process of becoming a "second-ascent" giant, one brightening into the ethereal realm of the giant stars for the second time, a speculation reinforced by its variability. Perhaps one day it will appear to us as a full-blown pulsating variable like Mira in Cetus.