Showing posts with label stars. Show all posts
Showing posts with label stars. Show all posts

May 10 - Happy Birthday, Cecilia Payne-Gaposchkin

   Posted on May 10, 2022

This is an update of my post published on May 10, 2011:




Don't you love it when someone reveals a whole new understanding of the universe?

And when that “someone” is a woman, you'd think she was unusual enough that we would have all heard of her! But I don't ever recall seeing this English-American astronomer's name before I first wrote about her in 2011!


Born on this day in 1900, Cecilia Payne studied botany, physics, and chemistry at Cambridge, in England. She completed her studies but didn't get a degree. You've probably already figured out it was because she was a woman—yep, Cambridge did not award degrees to women, back then!

While at Cambridge, Payne became fascinated by astronomy, and she went to the U.S. to study astronomy at Radcliffe (now part of Harvard). She was the first person to earn a PhD in astronomy at the college—and her paper (doctoral dissertation) was considered brilliant by at least some readers.

What Payne did was relate the type (spectral class) of stars to their actual temperatures, and she showed that the variation of the placement of the lines in a star's spectrum was caused by different temperatures, not just different amounts of the various elements.


At the time, people were sure that the Sun and other stars was made up of the same stuff as the Earth. That was what is called “the accepted wisdom” of the time. However, Payne's analysis indicated that the Sun had a lot more helium and a MILLION times more hydrogen than the Earth!

Unfortunately, Payne was just a student, and a more well-established astronomer named Henry Norris Russell persuaded her not to put forth that conclusion. Later, other evidence emerged showing that Payne, not “accepted wisdom,” was right.

And here's where science shines: Russell looked at the evidence, accepted the evidence, and changed his mind.

Here's where science doesn't always shine: once Russell, the older and more famous astronomer, changed his mind and accepted Payne's conclusion, many other scientists gave HIM, not her, the credit!

Aack!

Anyway, I have heard of Russell, because of the famous Hertzsprung-Russell diagram showing the different types of stars. 





 
(By the way, Payne later married and became Cecilia Payne-Gaposchkin).


For more...

Read about the life and death of an average star. 

Learn about different types of stars here. 

Here are printables you can use to learn more about stars.


 



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November 6 - A New Star!

Posted on November 6, 2021


This is an update of my post published on November 6, 2009:





NEWS FLASH, 1572: A new star appears!



On November 6, 1572, a new star appeared in the sky. It was hard to miss, because it was about as bright as Venus!


A new star in the sky? That shook up the astronomers. Since ancient times it had been thought that the universe beyond the moon was unchangeable. Most people still thought that Earth was the center of the universe and that the stars were fixed to the inside of a turning sphere that was a steady background across which the sun, moon, and planets moved as they made their closer orbits around us. If this were true, how did a new star suddenly appear on that sphere?



We now know that Earth circles the sun, the sun and all our familiar planets circle in an enormous disk of stars and gas that is our galaxy, and this galaxy, along with a small group of other galaxies, is rushing away from all the other galaxies at a tremendous speed left over from a Big Bang. The universe is much, much, much, much huger than anyone living in 1572 (let alone ancient times) thought. Observations of this new star, however, pushed us toward the modern view.

Many observers noticed the new star, but the one person whose name is attached to it (it is called both SN 1572 and Tycho's supernova), and who is generally credited with its discovery, didn't see it for five nights. Finally, on November 11, 1572, Tycho Brahe observed this wonder. Why did he, among so many observers and certainly not the first, get the credit?



First, Tycho Brahe was one of the few astronomers who made careful, systematic observations from steady locations. (He was motivated to do so partly because of this new star. He realized that others' measurements of the locations of stars and planets varied quite a bit.)




Also, Tycho gave the phenomenon the name that would eventually stick: he wrote about the new star in Latin, De stella nova. (The word nova simply means “new,” but we now know that Tycho's “new star,” now classified as a supernova, was an exploding—therefore dying—star. A supernova explodes in such a cataclysmic explosion that it can, for a short time, outshine an entire galaxy.)

Another very important point: Tycho published his observations. In 1573 he put out a book about the “new star”—De nova et nullius aevi memoria prius visa stella, or On the New and Never Previously Seen Star—in which he analyzed his own and others' observations of the phenomenon.

Finally, Tycho was one of the few who realized the importance of the sighting. Some people, clinging to the old way of looking at things, insisted that this new star was between the Earth and the moon, within the sphere that sees changes and variability. Tycho Brahe pointed out that such a close orbit would necessitate that the new star would have to shift when compared to the background of other stars—and he saw no such shift. He was so scornful of those who dismissed the importance of the (super)nova that he wrote in the preface of his book De stella nova, “Oh, thick wits. Oh, blind watchers of the sky.”



By the way...

You may be wondering if Tycho's supernova is still visible in our sky. Well, you can look at the general area where it appeared—in the constellation Cassiopeia—but it is no longer visible to the naked eye. As a matter of fact, it gradually faded away for two years and disappeared from sight in 1574. Since the star that exploded is about 7,500 light years away, it took until the 1960s for us to see the expanding shell of gas left over from the explosion.


To the left is the constellation of Casseopeia, and to the right is a 
photo of what Tycho's supernova looks like now, through a telescope.




You may be wondering where Tycho Brahe lived. He came from Scania, which was then part of Denmark but is now part of Sweden. He built a research institute on the island Hven but moved to Prague (now part of the Czech Republic) after a disagreement with the Danish king.

Weird...and weirder...

  • Brahe lost part of his nose in a duel (a swordfight), at age 20, and he wore a metal insert over the missing part for the rest of his life.

  • While he lived in Denmark, Tycho entertained large groups of people at his castle. He kept a dwarf named Jepp as a court jester—and kept him under the table during meals!

 

  • Tycho also kept a tame moose, but at some point the moose drank a lot of beer, fell down the stairs, and died.

          Gosh, I hate when that happens!


How about doing a little star watching tonight?

Thanks in part to Tycho Brahe—who not only built astronomical instruments, calibrated them, and made systematic nightly observations, but who also trained a new generation of astronomers—we now know a lot about the stars and gas clouds and galaxies in our universe. Tycho Brahe was the last major astronomer who had no telescope (which was invented several years after his death). On a clear night, in a place with little light pollution, you can see approximately what the world's best astronomer of the 1500s could see!

Can you see that some stars in the sky are slightly blue, and others are slightly red? The stars vary in color because they vary in temperature. This photo has magnified the stars in size so we can see their colors better:




Generally, the larger the star, the more gravity it has, 
and therefore the hotter it burns. Blue-ish and white
stars are the hottest, and reddish and orange stars
are the coolest. The in-between stars are medium size
and medium temperature (for a star!) - like our Sun!

But at the end of a star's life, it can swell up to be a
red giant - much huger than it was during the bulk of
its life, but also cooler.

Blue giants are super massive stars - and they burn
very quickly and change into something else - a
supernova, perhaps.


Here is a NASA page on supernovae.

Below is a photo of a supernova captured by the Hubble space telescope. It is brighter than 5 BILLION ordinary stars like our Sun!




For all sorts of hands-on astronomical fun, try this website.



Also on this date:




Constitution Day in the Dominican Republic 






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January 31 – A White Dwarf Is Discovered!

Posted on January 31, 2016



When I say white dwarf, I am not talking about a Little Person. Instead, I am talking about a certain kind of star.

Or, rather, I am talking about a certain part in the life cycle of some stars.

Sirius is the brightest star in the Earth's night sky. As a matter of fact, it is almost twice as bright as the next brightest star, Canopus. Naturally, it was seen by the earliest humans (and their not-yet-human ancestors), and later by ancient humans, and later still by medieval and then Renaissance humans...all the way up til now – BUT on this date in 1862, an American astronomer named Alvan Graham Clark spotted something nobody else had ever seen before:

Sirius has a much dimmer companion star!

So now, the thing we called Sirius pre-1862 now has to be called the Sirius star system, and we call the two different stars that make up that system Sirius A and Sirius B.

The Sirius star system seems bright in Earth's sky partly because it is pretty close – and getting closer! For the next 60 thousand years, Sirius will seem to get slightly brighter and brighter and brighter (after that, the distance between star systems will start to widen again, but Sirius will still be the brightest star in our sky for another couple of hundred thousand years!).

But the other reason Sirius seems so bright is because Sirius A is seriously large and seriously bright. It is about twice as massive as the Sun, and it is 25 times more luminous than the Sun. (There are stars in the universe even more massive and even more luminous than Sirius A, but they are farther away. Likewise, there are some stars that are closer, but they aren't as big and bright.)

What about Sirius B? It is much smaller than Sirius A, which is why it is called a dwarf; it is only about the size—or volume—of Earth, although it has almost as much stuff—mass—as the Sun! You have probably already guessed that Sirius B is much less luminous than Sirius A, as well – so faint that it took scientists a long time to spot it next to its brighter companion.

According to Wikipedia, Sirius B is a whopping ten thousand times less luminous than Sirius A, in visible light (although it does emit more X-rays than its companion). 

It wasn't always so. Millions and millions of years ago, both Sirius A and Sirius B were huge blue stars, burning hot and bright. Sirius B happened to be the more massive one, so it burned up its hydrogen more quickly, fusing it into helium at a much quicker rate. Once the fuel ran out, the star sort of imploded, collapsing in on itself. Once that happened, things heated up so much that helium was able to start fusing into carbon and oxygen. At that point, about 120 million years ago, Sirius B ballooned out to become a red giant. The more the star expanded, the less gravitational attraction the outer layers of the star had for the inner core, and those layers drifted away. Eventually, all that was left of Sirius B was that inner core, which is what we see. It is a very dense, very hot body is not undergoing fusion anymore. It will slowly cool off more and more and more, until it becomes a black dwarf.

This is all part of the normal life cycle of average stars, including our sun and even Sirius B.


 

  • Here is a zoom to see Sirius B next to its much larger companion. 




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