skytalk

Our sun’s celebrity pales compared to some stars


Largest known star (16,000 light years away) shows signs of imminent destruction. W26 is 3,000 times the diameter of our sun. (2,596 billion miles in diameter). A commercial jet flying at 600 miles per hour would cross its diameter in 493 years! Big week for dates with names; Halloween, followed by All Saints and All Souls day, then the time change of fall back one hour Sunday morning at 2 a.m.


October 28, 2013

[Dave Heller] The sky will be good and dark for trick or treaters Thursday, thanks to a waning crescent moon. Let’s scare ‘em up with Derrick Pitts, chief astronomer at the Franklin Institute. Derrick, many days of note this week, though Halloween’s the sweetest.

[Derrick Pitts] It is a really wonderful time to look at the night sky on Halloween because there’s a very thin, waning crescent moon that rises at about 4:15 in the morning and sets at about 4:00 in the afternoon. Maybe that’s better for ghouls and goblins?

How is it for saints and souls?

Actually it’s a bit better for saints and souls. It works out really well; it’s the next days after that, November 1 to November 2. And these all go together in a way that’s really interesting. First of all, Halloween is a cross-quarter day, All Saints and All Souls Day of course are religious observances, but they’re meant to follow on with this celebration of Halloween. Halloween is the time when we have the witches, the ghouls, the goblins — all of these spirits that are sort of loose in the world. And they really have until midnight to get themselves back into place. So they roam the planet, supposedly, for that evening, and a trick or treat might get you away from them. But certainly the next day all the saints and all the souls take care of everything and it’s all locked up again for another year. So these all roll together, and it’s interesting how the calendar fits itself with the cultural sort of expression, and in this case, the faith and religious expression that sort of ties it all together around an astronomical theme, because it is the halfway point between the first day of fall and the first day of winter, a cross-quarter day.

Let’s keep rolling. Thursday, Friday, Saturday: No religious significance, but there’s a secular date of note on Sunday.

Indeed there is. Saturday night, Sunday morning, however you’d like to cut it at 2:00 Sunday morning we turn our clocks back one hour. This is not true for every place in the continental United States, and certainly not true for every place around the world that this adjustment is made. But it’s actually made so that we can fit our world in with how the sun appears at what time during the course of the day, the amount of sunlight we have, and we sort of fit everything together to make it all work a little bit better.

Well wherever you are on this planet, our sun’s a star though its celebrity pales compared to southern constellation Ara.

When you look at our sun as a star, as we see it, compared to our planet, it certainly is enormous. 865,000 miles in diameter, it’s just GIGANTIC compared to our planet.

In context, what is the diameter of our little Earth?

The diameter of Earth is just under 8,000 miles. So the sun is about 100,000 times bigger. Amazing, isn’t it? Yes, well, if we compare it to other stars, we find out that maybe it’s not so big after all. Let’s look at the largest star that’s known these days; it’s a star called W26, as you said in the southern constellation Ara. It turns out that this star is 3,000 times larger than our star is. So that means its diameter is about 2.6 billion miles.

OK, take our sun out, plop that one in — how far would its reach go?

Its reach would go out past the orbit of Uranus. Here’s another way to compare it: If you could fly a commercial jet aircraft across the diameter of that star at 600 miles per hour, it would take a little over 493 years to cross the diameter of that star.


“If you could fly a commercial jet aircraft across the diameter of [W26] at 600 miles per hour, it would take a little over 493 years to cross the diameter of that star.”

Derrick Pitts


Was this star born that big, or did it have a robust adolescence?

This is one of the cool things about how phenomena can manifest things in the universe. The laws and principles of physics that we depend upon so much to understand how everything works can allow certain kinds of phenomena to manifest themselves here on this planet, here in this environment. But that doesn’t constrain what can happen in other environments. The same laws and principles can allow the birth of a star at that size. That’s not all together unusual. It might be rare to find a star that big, but we can certainly find stars that are under that size or working their way up toward that size. The one thing about a star like this though, and probably the reason why we don’t find so many of them, is because they live fast and they die young. A star like this can only last for a few million years and then it explodes in a tremendous supernova explosion. So we may not catch its life, because on the other side of the galaxy we may not be able to detect its existence because it is so short.



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