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

[LURCH]

Cool! I love it when I'm right.

Current estimates place the number of potentially deadly Near-Earth Objects (asteroids of 1km or larger who's orbit takes them close to Earth's orbital path) at around 1200. Approximately how many have been officially sighted and cataloged?

 

[schwarzchildradius]

Current estimates place the number of potentially deadly Near-Earth Objects (asteroids of 1km or larger who's orbit takes them close to Earth's orbital path) at around 1200. Approximately how many have been officially sighted and cataloged?

Nasa reports 2449 NEOs on 8/28/03 here.
The Planetary society reports 2,225 NEOs http://planetary.org/html/news/articlearchive/headlines/2003/neoworkshop.html from 2/19/03.
But objects with absolute magnitude of +18.5 have diameters of 1km or larger, and there are 662 of them by nasa's report, also indicated on this graph:
http://neo.jpl.nasa.gov/gif/web_total.gif
Thor's hammer was supposed to be made of a fallen meteorite.

 

[LURCH]

Originally posted by schwarzchildradius
...objects with absolute magnitude of +18.5 have diameters of 1km or larger, and there are 662 of them by nasa's report, also indicated on this graph:
http://neo.jpl.nasa.gov/gif/web_total.gif

Correct! The "1200" mentioned was originally at the high end of the estimates, but the rate at which new NEO's are being discovered indicates that the original estimates were low, and 1200 may even be an underestimate.

Ask away, Schwarzschild.

 

[schwarzchildradius]

ok, Thursday is obviously "thor's day" in Norse mythology. What planet and for ex. crd. Nordic God is represented by "Tuesday"

 

[chroot]

The saxon Tiu, god of War.

- Warren

 

[Labguy]

Originally posted by chroot
The saxon Tiu, god of War.

- Warren

But what is the planet, first point of the question?

 

[chroot]

God of War -> Mars, the Roman equivalent of the Saxon Tiu.

- Warren

 

[schwarzchildradius]

Yep. mars. I've also seen it spelled Tiw. I've got to find out what other days of the week represent planets in said culture.
Go!

 

[chroot]

What is the largest baseline optical interferometer currently in operation? What is its resolving ability?

- Warren

 

[Labguy]

Originally posted by chroot
What is the largest baseline optical interferometer currently in operation? What is its resolving ability?

- Warren

It is (I think) the Navy Prototype Optical Interferometer (NPOI).

Resolving ability is the same as could be obtained with a single 430 to 435 meter mirror, but I don't know what that is in arc seconds, since there are several different ways to figure potential resolving power. It is able to resolve the actual disks of some stars. Latest results I have heard were 9 milliarcseconds.

 

[chroot]

Hey Labguy,

Unfortunately it is not the NPOI, which has a maximum baseline of 437 meters. The longest baseline used to date at NPOI is only 64 meters.

There are interferometers with both larger maximum baselines, and larger in-use baselines. Would anyone like to give it a shot?

- Warren

 

[Labguy]

Originally posted by chroot
Hey Labguy,

Unfortunately it is not the NPOI, which has a maximum baseline of 437 meters. The longest baseline used to date at NPOI is only 64 meters.

There are interferometers with both larger maximum baselines, and larger in-use baselines. Would anyone like to give it a shot?

- Warren

Is the biggest one (correct answer) optical? Now I really want to know...

 

[chroot]

Labguy,

It is optical, indeed! :)

- Warren

 

[marcus]

Originally posted by chroot
Labguy,

It is optical, indeed! :)

- Warren

I believe CHARA on Mt Wilson is an opt. infer. array
with longest possible baseline 330 meters

 

[marcus]

Originally posted by chroot
Labguy,

It is optical, indeed! :)

- Warren

chara is indeed optical (as well as infrared)
and this Georgia State source
http://www.chara.gsu.edu/CHARA/array.html
gives the resolution as
200 micro-arcseconds


A strong contender would be European Southern's VLT
which is in operation in Chile, the results I have seen
from VLT were in the near infrared I believe, but will check
on the claimed resolution

 

[chroot]

marcus,

CHARA is correct, with a currently in-use baseline of 330 meters. This is also its maximum possible baseline.

In terms of maximum possible baseline, SUSI in Sydney, Australia is king with a possible 640 meter baseline. Only 140 meters have been used to date, however.

The NPOI is the first-born prince, with a maximum 437 meter baseline, 64 meters used to date.

Reference: Sky & Telescope magazine, May 2003.

marcus, your turn!

- Warren

 

[marcus]

OK I will ask. Since we are on optical inferometry, here's one:

The plan is to launch an optical interferometry instrument into space in 2009.

You have a lot of latitude in how you answer this question.

What is the name of the mission?

what is one other interesting detail about it? You might want
to pick one of the following suggestions:

1. what outfit is designing it
2. what is the intended orbit
3. how long is the main boom (this sort of determines max baseline)
4. how many interferometers are to be mounted on the boom
5. anything else especially interesting

No need to cover all these, I'm just looking for the name of the mission and some bit of detail about it

 

[chroot]

marcus,

It is called, quite creatively, the Space Interferometry Mission, or SIM.

It is being built by the JPL.

It will have a 10m baseline separating two 0.3m telescopes, and a maximum resolution of 1 microarcsecond.

The mission should be able to detect proper motion at a level of 2 microarcseconds per year, which corresponds to a movement of 10 m/s at a distance of 1000 pc!

From 10 pc away the Sun would appear to wobble 4.5 milliarcseconds, due mostly to the perturbations of Jupiter and Saturn. The SIM instrument will be able to detect wobbles 5,000 times smaller.

- Warren

 

[marcus]

Your go, Warren.


BTW what you say is exciting. I hope very much it is launched on schedule (2009) and works as designed.

The doppler exoplanet surveys measure RADIAL wobble speeds and this presumably measure up/down right/left wobble speeds and so one will get a much better grip on the masses of the
100 or so exoplanets found so far. Or so I would imagine.

Besides, one might be able to detect wobble due to smaller planets? I guess that is the idea

Ask one

Originally posted by chroot
marcus,

It is called, quite creatively, the Space Interferometry Mission, or SIM.

It is being built by the JPL.

It will have a 10m baseline separating two 0.3m telescopes, and a maximum resolution of 1 microarcsecond.

The mission should be able to detect proper motion at a level of 2 microarcseconds per year, which corresponds to a movement of 10 m/s at a distance of 1000 pc!

From 10 pc away the Sun would appear to wobble 4.5 milliarcseconds, due mostly to the perturbations of Jupiter and Saturn. The SIM instrument will be able to detect wobbles 5,000 times smaller.

- Warren

 

[marcus]

Nicool's 3 days have run out
Warren answered (with some nicely turned irony and
utter correctness) on 3 September
and I replied that it was his turn on 4 September
and it is now the 8th so it is incumbent on me to ask another Q



A Greek astronomer measured the distance to the moon (as a multiple of the Earth's diameter) with surprising accuracy

his measurement was much more accurate than the earlier one by Aristarchus (the first to propose the heliocentric model) and
indeed it was, I believe, accurate to within 5 percent!

Who was this Greek and roughly when did he live?

For extra credit, indicate how he is believed to have arrived at the ratio of lunar distance to Earth diameter.

If you know you are right, don't wait for confirmation, just go ahead and ask a question yourself

 

[bogdan]

It was Hipparchus...(190-120 BC)
He estimated the earth-moon distance at 250,000 miles, less than 5 percent off.
He used an astrolabe...

Astrolabe, instrument used for measuring the positions of heavenly bodies. It consists of a circle or section of a circle, marked off in degrees, with a movable arm pivoted at the center of the circle. When the zero point on the circle has been oriented with the horizon, the altitude or azimuth of any celestial object can be measured by sighting along the arm.

...see ya...

 

[marcus]

Originally posted by bogdan
It was Hipparchus...(190-120 BC)
He estimated the earth-moon distance at 250,000 miles, less than 5 percent off.

OK bogdan, that is right and it is your turn to ask us a question.
Please don't wait. Just ask, this keeps the game going fast
and makes it more interesting.

BTW I have read somewhere that Hipparchus estimated the earth-moon distance as 30 Earth diameters.
I do not know what that is in miles, but you are undoubtably right that it is around what you say and also that it is within a few percent of the true average distance.

I did not ask about his method (you say astrolabe) but some time we could investigate this. People may have different ideas.

Please ask!

 

[bogdan]

Which romanian scientist had his name assigned to a crater from the moon ?

 

[marcus]

Originally posted by bogdan
Which romanian scientist had his name assigned to a crater from the moon ?

So the person is a man and a scientist. Hmmmm

I know of a Romanian woman diplomat who has a crater on Venus
named for her-----Elena Vacarescu

Maybe someone else knows

edit: Venus not moon

 

[marcus]

Crater Spiru Haret on moon's backside

OK bogdan---the crater is named for the astronomer
Spiru Haret (1851 - 1912)

Now how would you like to ask a question that is more
about astronomical things (planets, stars, galaxies, CMB whatever you like) and less about names?

I would like to hear what question you think of.

I will give you my turn right now, if you ask something soon.

 

[bogdan]

The answer is correct...your turn...I don't know any other questions...

 

[marcus]

Question

Originally posted by bogdan
The answer is correct...your turn...I don't know any other questions...

Thanks bogdan, I'll take a turn.

as all here know, the bulk of the energy released in the sun's core results from fusing 4 protons into a helium nucleus

The question is: for each helium nucleus made, how many
neutrinos or antineutrinos are produced as a byproduct?


For extra credit: write down the series of reactions to show the stage in the process where neutrinos are produced

 

[Lonewolf]

OK, I'll have a go.

The standard three stage PP chain is what I'll assume you're looking for.

¹H + ¹H -> ²H + &nu; + e<sup>+

1</sup>H + ¹H -> ²H + &nu; + e<sup>+

2</sup>H + ¹H -> ³He + &gamma;

²H + ¹H -> ³He + &gamma;

³He + ³He -> ⁴He + ¹H + ¹H

So, there is one neutrino. &nu;, per helium nucleus. The answer is the same for the PPII and PPIII chains, although they have 2 neutrinos and 2 helium nuclei.

 

[marcus]

The standard three stage PP chain is what I'll assume you're looking for.

¹H + ¹H -> ²H + &nu; + e<sup>+

2</sup>H + ¹H -> ³He + &gamma;

³He + ³He -> ⁴He + ¹H + ¹H

So, there is one [correction TWO] neutrinos. &nu;, per helium-4 nucleus...

full credit if you make the indicated small correction to this otherwise correct answer

in the proton-proton chain the second reaction you list must happen twice (per helium nucleus formed)

so on a per-helium-nucleus-formed basis the first reaction also must occur twice

so TWO neutrinos are emitted for each ⁴He that is produced (reasonable since two protons changed to neutrons in the process)

You got the proton-proton chain, which is the main thing.

Take it as read that you have made that correction GO. It's your turn.
Dont even wait for confirmation.

 

[Lonewolf]

What name is given to the prototype stars thought to be the start of a main sequence star of around one solar mass?

 

[Shadow]

Is it "cheating" if I look the answer up? I know that I know it, I just can't think of it right now.

 

[Lonewolf]

I don't think it'd be cheating at all. How would we know if you had anyway?

 

[Nereid]

Originally posted by Lonewolf
What name is given to the prototype stars thought to be the start of a main sequence star of around one solar mass?

T-Tauri (and I didn't look it up!), after the archetype star, T-Tau(rus) [duh]

 

[Lonewolf]

It seems the thread has life again. Your turn, Nereid!

 

[chroot]

Originally posted by Nereid
T-Tauri (and I didn't look it up!), after the archetype star, T-Tau(rus) [duh]

I have to mention that the star's name is T Tauri, not T Taurus.

Name like Tauri, Orionis, Piscium, Andromedae and so on are Latin genitive (possessive) forms of the constellations' names. In other words, T Tauri means "the T star of Taurus."

You'll see a lot of different naming systems in use, like "52 Cygni" (Flamsteed numbers) and "delta Orionis" (Bayer designations) and "RR Lyrae" (variable-star designations) but they all use the Latin genitive name.

- Warren