Astronomy Trivia Challenge: Can You Answer These Questions About the Night Sky?

[Labguy]

Originally posted by marcus
Nereid, there was a picture of it on the tapestry, was there not?
But I was just being goofy----its up to you to come up with a
serious answer if possible

This particular October 14th had direct implications on the advancement of spaceflight and, therefore, astronomy.

HINT:
Check between WWII and 1950! Anyone can "come up with the answer".

Labguy

 

[chroot]

Chuck Yeager broke the sound barrier on October 14, 1947. I found this within five minutes of searching history archives when you first posted your question, but I had no idea you were looking for this. I thought it was something directly relating to astronomical phenomena. Yes, I understand your point that breaking the sound barrier was important in the development of space technology and thus science equipment like Hubble, but I really feel it's better categorized as an achievement of engineering, not of astronomy...

- Warren

 

[marcus]

Originally posted by Labguy


Check between WWII and 1950! Anyone can "come up with the answer".

Labguy

Oh no, I fear you are mistaken! The battle of Hastings (which was when Halley's comet was seen) was in 1066! This is not between WWII and 1950 at all!

The periodic observation of Comet Halley, when Halley put two and two together and computed the orbit, was a great benefit to astronomy and helped to bring about a vast improvement in, as you so rightly say, "the accuracy of our observations".

Your only mistake, I feel, is about when the Battle of Hastings actually occurred!

 

[Labguy]

Originally posted by chroot
Chuck Yeager broke the sound barrier on October 14, 1947. I found this within five minutes of searching history archives when you first posted your question, but I had no idea you were looking for this. I thought it was something directly relating to astronomical phenomena. Yes, I understand your point that breaking the sound barrier was important in the development of space technology and thus science equipment like Hubble, but I really feel it's better categorized as an achievement of engineering, not of astronomy...

- Warren

That is the answer. I would think that this event led to the (more rapid) development of aircraft and space technology, let us develope orbital and launch capability, which then "put up" the HST, IRAS, COBE, Probes to the planets, Mars global surveyor, et al and on. Just the HST and IRAS alone "jumped" our astronomical knowledge way above anything we could have known by now from Earth-bases telescopes. Anyway, that was the question and thought behind it.

You ask next question.

Labber

 

[chroot]

What is the largest supernova remnant visible in the night sky, in terms of solid angle subtended?

- Warren

 

[Labguy]

Originally posted by chroot
What is the largest supernova remnant visible in the night sky, in terms of solid angle subtended?

- Warren

That should be the Vela SNR. It is described as a circle of ~8.3°, or 72 parsecs in diameter at its current distance measurement

Labguy

 

[chroot]

I sure hope I'm not misinterpreting anything I've read. The Vela SNR is not the largest. There's one much, much larger.

- Warren

 

[Labguy]

Originally posted by chroot
I sure hope I'm not misinterpreting anything I've read. The Vela SNR is not the largest. There's one much, much larger.

- Warren

I think you are right. It seems that "The Vela Supernova Remnant is just one part of the Gum Nebula (Gum 12), a complex shell of faint nebulous filaments. It is the largest object in the sky, apart from the Milky Way, and measures 36 degrees across! It is a half shell of filaments similar to the Veil Nebula in Cygnus, and was discovered by Australian Astronomer Colin S. Gum in 1952." I hope that GUM NEBULA is right. At 36 degrees, I can't imagine a larger one, in terms of angle subtended.

BUT, the same source says that the Vela SNR is a part of the Gum nebula, but that the Gum nebula itself is not a SNR. (?) It seems that the Vela SNR material collided with, and excited atoms in, an already existing large filament of dust and gas which, in itself, was not a SNR. So I'm confused a bit too. Is it Gum at 36 degrees or Vela at 8.3 degrees? I did find lists of much larger SNR's, but this was by size, and in other galaxies. Their angle subtended is less than 8.3*.

In other words, I have no idea!...

Labguy

 

[chroot]

To the best of my knowledge, Labguy, that's it. ;)

Your turn.

- Warren

 

[chroot]

Hmm Labguy do you have a copy of Burnham's or something authoritative about the Gum? The stuff I'm reading is all online, and it all seems to say that the Gum nebula is indeed an SNR.

- Warren

 

[Labguy]

Originally posted by chroot
Hmm Labguy do you have a copy of Burnham's or something authoritative about the Gum? The stuff I'm reading is all online, and it all seems to say that the Gum nebula is indeed an SNR.

- Warren

One source stated what I said in my last post, but others I can find by a search say that the Gum Nebula itself is indeed an "SNR" as you just stated. But, several sources said that the Gum nebula is not well understood, cannot find the date or ~time of "the" supernova. Others say that the Gum nebula is an SNR, but an accumulative SNR from many different supernovae occurring over thousands (many) of years. This might account for its huge size.(?)

In my last post I said: "So I'm confused a bit too. Is it Gum at 36 degrees or Vela at 8.3 degrees? I did find lists of much larger SNR's, but this was by size, and in other galaxies."

Either way, both were mentioned with information from several sources (now), so I'll have to say it is the Gum Nebula at 36-40 degrees subtended. Thanks for the exceedingly HUGE help-hint...

Labbby

 

[marcus]

Labguy's turn, what'll he ask?

Originally posted by chroot on October 16, 3:15 PM
To the best of my knowledge, Labguy, that's it. ;)

Your turn.

- Warren

 

[Labguy]

Marcus posted:

quote:
--------------------------------------------------------------------------------
Originally posted by chroot on October 16, 3:15 PM
To the best of my knowledge, Labguy, that's it. ;)

Your turn.

- Warren

Ok, I'll go since we danced around between both the Vela SNR and/or the Gum nebula.

Question:
I can show at least six (6) clear differences between "properties" of Galactic Clusters and Globular Clusters..

Name at least four (4) differences between these types of clusters. Obviously, any property of one needs to match the same property of the other, showing a difference. Example:

Galctic Cluster:
Property:
1. ------------------(property #1)
2. ------------------
3. ------------------
4. ------------------

Globular Cluster:
Property:
1. ------------------(#1, same as above, but different)
2. ------------------
3. ------------------
4. ------------------

Any other format is fine as long as it lists the same "property", but shows the difference. A "property" might be something like "Chemical composition", but that isn't on the list except as an explanation for a more significant difference.

Labguy

 

[Labguy]

Ok. Two days have come and gone, so here is the answer(s):

Galactic Clusters:
Clusters Located in the disk of our galaxy
Young stars (Population I)
~50 to 10000 stars per cluster
~10 pc in diameter
Star density ~ 0.1 to 10 stars/pc^3
Irregularly shaped
~1000 in the Galaxy
Examples: Pleiades, Hyades, Praesepe



Globular Clusters:
Clusters Located in the halo of our galaxy
Old stars (Population II)
~10^4 to 10^6 stars per cluster
~20-100 pc in diameter
Star density ~ 0.5 to 10^3 stars/pc^3
Roughly spherically shaped
~150 in the Galaxy
Examples: M3, M13 (Hercules), M15

Make it someone else's turn.

Labguy

 

[Nereid]

OK, my turn

What mystery about the solar system has the recent HST-based work on the EKB merely served to heighten?

For extra credit, why is Edgeworth's name usually left out when the EKB is mentioned in the popular press?
[edit: Edgeworth as the correct 'E']

 

[Labguy]

Originally posted by Nereid
What mystery about the solar system has the recent HST-based work on the EKB merely served to heighten?

For extra credit, why is Eddington's name usually left out when the EKB is mentioned in the popular press?

It took Hubble's ability to resolve as small as 40 milliarcseconds (nothing else can do that) to confirm the size of Quaoar, A KBO (Kuiper Belt Object). Quaoar is about 4 billion miles away from Earth, well over a billion miles farther away than Pluto.

In the mid of last century, the existence of a ring of small planetisemals was first suggested by the astronomers Kenneth Edgeworth (1880-1972) and Gerard P. Kuiper (1905-1973), but the first discovery of an Edgeworth-Kuiper belt object was not until 1992. By now, over 550 KBO's are known.

Hubble's resolution will help confirm the size/mass of more KBO's.

Labguy

 

[Nereid]

short period comet mystery

Hmm, this is a more difficult question than I'd expected, so here's the answer:

Six astronomers used the new ACS on Hubble to search for faint EKB objects in a small patch of sky, to get an estimate of the size-number distribution of such objects at sizes down to ~15 km. They found far fewer than expected from an extrapolation of the distribution at larger sizes, previously obtained from other studies. While they are careful to point out that their results constrain the size-distribution of the scattered disk (which they call the "excited" objects) only weakly, their finding deepens the mystery of the origin of short period comets*.

Oh, and by the way, Pluto is almost certainly the largest EKB object!

Here's a Hubble site link:
http://hubblesite.org/newscenter/archive/2003/25/

And an arXiv preprint (click on one of the Full-text links to get the full paper):
http://arxiv.org/abs/astro-ph/0308467

*"The KBO populations are far sparser than theoretical estimates of the required precursor population for short period comets." in their own words

Someone else's turn.

 

[Nereid]

OK, an easy one: what are the nearest (known) red dwarf and white dwarf stars?

Bonus question: approx how many red dwarf and white dwarf stars within 100 ly of us remain to be discovered?

 

[Shadow]

Proxima Centauri and Sirius B. Sirius being the white dwarf

 

[Nereid]

OK Shadow, your turn.

As you'll see by looking at earlier posts, the 'rules' are that you post an astronomy question, and the first person to get the answer gets a turn. Of course, as the person who posted the question, you get to decide if the answer is correct or not!

Happy posting!

 

[marcus]

Originally posted by Nereid
OK Shadow, your turn.

As you'll see by looking at earlier posts, the 'rules' are that you post an astronomy question, and the first person to get the answer gets a turn. Of course, as the person who posted the question, you get to decide if the answer is correct or not!

Happy posting!

there is also (see Nicool's original post) a kind of
vague "three-day rule"
which is that if it is somebody's turn and they don't take it
after a reasonable time like three days
then the last person active gets to go
and if they don't then its up for grabs

so if Shadow doesn't come up with a question in a day or so
then Nereid can pose another one
which, if Nereid doesnt, others can do also
but please folks one at a time

also if you happen to ask a question that is too hard for the
rest of the players and nobody answers
then not to worry because after a while (the "three day" idea again) you can just say what the
answer is and ask an easier one
or, if you dont, someone else can.

this means that its not the end of the world if someone asks something nobody can answer

Shadow yoohoo where are you?

 

[Shadow]

Oh wow i haven't been around and completely forgot about this. sorry!

ok here's the question

Give at least two ways (theories) on how to divert an asteroid on a collision course with earth.

 

[Phobos]

Originally posted by Shadow
Give at least two ways (theories) on how to divert an asteroid on a collision course with earth.

Get all the people in China to jump off a chair at the same time to move the Earth out of the way. kidding!

strategies: (thanks to Robert Burnham, Astronomy Mag. Dec 02)
(1) Nuke explosion next to or just below the surface to vaporize a portion. Offgases change the orbit.
(2) Direct impact with fast, massive, inert object to deflect its course.
(3) Use the Yarkovsky effect to generate thrust (one way is to dump lots of reflective material on one side (chalk, ice) and light-absorptive material on the other (charcoal, soot).
(4) If it has a high ice content...use giant mylar mirror to focus sunlight on it. Jetting vapors would alter the orbit.

Lots of lead time is the key to success.

 

[Shadow]

correct! I have to come here more often... seems like i missed quite a bit. Your turn Phobos!

 

[Phobos]

Where has my brain been the past few weeks? No wait...here's the question...

What was the nickname that Carl Sagan (et al.) gave to the solid hydrocarbon snow that is likely to be found on the surface of Saturn's moon Titan? (they recreated it in the lab by zapping a vessel with similar atmospheric gasses)

 

[cragwolf]

here is my guess: tholin

(my post has to be longer than ten words for some reason.)

 

[SchrodingersCat]

Titan tholins?

 

[schwarzchildradius]

Manna from Heaven?

 

[Phobos]

cragwolf got it first...your turn

(welcome to Physics Forums, SchrodingersCat!)

 

[cragwolf]

Cepheids

Here is my question (I hope it hasn't been asked before):

Cepheid variable stars pulsate in a very regular and stable manner. What causes this pulsation? Please include in your answer an explanation of why the Sun doesn't pulsate in this way.

 

[schwarzchildradius]

Here is my question (I hope it hasn't been asked before):

Cepheid variable stars pulsate in a very regular and stable manner. What causes this pulsation? Please include in your answer an explanation of why the Sun doesn't pulsate in this way.

Typically there's some Helium in the atmosphere of the star. As radiation ionizes the Helium, the atmosphere expands and the star brightens. The Helium cools and loses its ionization, falling back toward the center of the star, causing it to dim a bit. The correlation between the period of the brightening and the intrinsic brightness of the star allows you to estimate the absolute distance.

 

[cragwolf]

Typically there's some Helium in the atmosphere of the star. As radiation ionizes the Helium, the atmosphere expands and the star brightens. The Helium cools and loses its ionization, falling back toward the center of the star, causing it to dim a bit.

Assuming that's true ( ) , why does the atmosphere expand when the Helium ionizes (and contract when it recombines). Also why doesn't this happen to the Sun?

 

[schwarzchildradius]

When Helium is ionized it becomes opaque to radiation, the radiation causes the envelope of Helium to expand as it is heated. When the Helium de-ionizes it becomes transparent to radiation & contracts. The sunis not massive enough to be a Cepheid variable

 

[cragwolf]

Well done. Your turn to ask a question.

 

[schwarzchildradius]

Super! Here it is: What's the name of the Egyptian mathematician who first calculated that the world must be round, and what visible clue did he use to find this out? (If you've seen "Cosmos" by Sagan this one is easy)