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

[Nicool003]

Crag are you here? can you confirm the answers...?

 

[cragwolf]

labguy's answer is more or less correct. Mostly, astronomers speak of a bimodality in the metallicity distribution of globular clusters in our Galaxy (metallicity tends to scale roughly linearly (*) with colour, so the two terms tend to be interchangeably used). There appears to be two populations of globulars within the Milky Way: a metal-poor population ([Fe/H ~ -1.5] associated with the galactic halo, and a metal-rich population ([Fe/H] ~ -0.5) associated with either the galactic disk or bulge. The metal-rich globulars seem to be roughly 2 billion years younger (on average) than the metal-poor globulars (but note, this is roughly the same as the uncertainty in the ages of globular clusters). One theory of globular cluster formation is that the younger, metal-rich clusters were formed during a merging episode (i.e. when the host galaxy merged with another galaxy), and the older, metal-poor globulars formed during the formation of the host galaxy itself. Observations of mergers show very young globulars.

(*) But in recent years this assumption of linearity has been challenged.

 

[axeeonn]

Erm, I said metal.

 

[Labguy]

Erm, I said metal.

Yes, you did. But, you were also making the distinction between open and globular clusters, while the question was only about globulars.

I had a question, before the PF format changed, that I don't think was ever answered.(?)

QUESTION:
In the Crab Nebula (Supernova Remnant),
(1) What is particularly rare about the light that we can see?
(2) What causes this rare property?
(3) What is the name given to this type of light (EM radiation)?

 

[axeeonn]

The pulsar produces synchrotron radiation, which is what partially makes the nebula glow. This is caused when charged particles, I think deutrons, sprial around a magnetic field. The photons are then emitted from the poles of the mag field.

 

[Labguy]

The pulsar produces synchrotron radiation, which is what partially makes the nebula glow. This is caused when charged particles, I think deutrons, sprial around a magnetic field. The photons are then emitted from the poles of the mag field.

Synchrotron radiation is right for the name, but I need two more specific answers for the rest. Right track, though.

 

[J-Man]

Labguy asked:
QUESTION:
In the Crab Nebula (Supernova Remnant),
(1) What is particularly rare about the light that we can see?
(2) What causes this rare property?
(3) What is the name given to this type of light (EM radiation)?

(1) We see light in all known forms/frequencies and it does not follow the blackbody radiation curve, increasing toward lower frequencies rather than toward high. (It is said to be "nonthermal".)
(2) The fastest known Pulsar, near the middle of the nebula.
(3) Synchrotron Radiation.

 

[chroot]

1) It is polarized; different regions have different polarizations.
2) Electrons spiraling around regions of uniform magnetic field.
3) Synchrotron radiation.

- Warren

 

[Labguy]

Originally posted by chroot
1) It is polarized; different regions have different polarizations.
2) Electrons spiraling around regions of uniform magnetic field.
3) Synchrotron radiation.

- Warren

This one is correct. The main "property" I was looking for was that this type of EMR is polarized.

Your question, Chroot.

 

[chroot]

Hmmm... my turn... I got to think of a good one. :)

- Warren

 

[chroot]

1) What major astronomical event occurred in 1987? (Hint: Large Magellanic Cloud)

2) The event was observed by more than just optical means. A particularly weakly-interacting type of particle was implicated. What were the particles?

3) How were these particles thought to be formed?

4) How many were detected, and when? How does that evidence help us understand what happened?

- Warren

 

[Labguy]

Originally posted by chroot
1) What major astronomical event occurred in 1987? (Hint: Large Magellanic Cloud)

2) The event was observed by more than just optical means. A particularly weakly-interacting type of particle was implicated. What were the particles?

3) How were these particles thought to be formed?

4) How many were detected, and when? How does that evidence help us understand what happened?

- Warren

(1) Supernova 1987A, Type II Supernova.
(2) Neutrinos.
(3) A significant portion of the energy from the "rebound explosion" in a Type II supernova is in the form of Neutrinos.
http://www.solstation.com/x-objects/sn1987a.htm
(4) Detected 02/23/1987. Approximately 10^17 hit the detector and a total of 10 were detected, of ~10^58 estimated to be emitted. They were detected before the visable light reached the first sensors/cameras. The neutrino:light delay was ~2 to 3 hours. The amount (number) of neutrinos from a SN will tell us (a) the energy effenciency of different types of supernovae explosions, (b) which type of supernova was seen, (c) the different "rebound" energy effeciencies in supernovae from stars of different original chemical compositions (this "rebound" took ~2 hours to emit light in the visable after the neutrinos were produced in the explosion), and (d) lots of other neat stuff filling the book right beside my computer...

 

[chroot]

Labguy: You get a gold star. :) Your question?

- Warren

 

[Labguy]

Originally posted by chroot
Labguy: You get a gold star. :) Your question?

- Warren

Ok, thanks. We might as well stay on the supernova subject, in general. In SN 1987A (last question), we happened to be lucky enough to get the early neutrino detections, and source identification, about 2-3 hours before the visable light was detected. We also know that most of any supernova energy is released as neutrinos, the rest as various wavelengths of EM radiation. Assuming these facts:

QUESTION:
(A) For SN 1987A in particular, what could have, and did, make the visable light delay as long as 2-3 hours instead of a shorter time period?

(B) In any supernova, what would be the most likely reason (cause) for a longer or shorter delay between neutrinos reaching us versus the EM radiation reaching us? This is not the same, specific reason as for SN 1987A as above.

The question (A) above might be a tough one, but I know the answer is out on the web, and in books, somewhere. Leeway will be given for "close enough"..

 

[J-Man]

Labguy asked:
QUESTION:
(A) For SN 1987A in particular, what could have, and did, make the visable light delay as long as 2-3 hours instead of a shorter time period?

(B) In any supernova, what would be the most likely reason (cause) for a longer or shorter delay between neutrinos reaching us versus the EM radiation reaching us? This is not the same, specific reason as for SN 1987A as above.

(A) Calculations suggest that in SN 1987A the initial shock wave did not make it out of the core on its own. The core needed to contract even more before it could become a true neutron star. It did so by vast neutrino losses. The neutrinos were produced by the annihilation of electron-positron pairs made by the gamma rays. The total energy emitted in the 10-second neutrino burst was enormous, about 250 times the energy of the material explosion. It is believed that a small fraction of these neutrinos revived the stalled shock and powered the great explosion of the star. By heating and expanding the star and triggering a new flurry of nuclear reactions in its layered interior, the revived shock was responsible for the supernova's optical display. The effect was delayed by about 2 to 3 hours however: the shock had to traverse the entire star before any light made it out. The neutrinos from the collapsing core easily outraced the shock. Passing through the rest of the star very close to the speed of light, and so they were the first signal to leave the supernova.

(B) It depends on the progenitor star, but I'm not sure which characteristics specifically it depends on. All my googling turned up "since the neutrinos reach us before the visible light, we can use this as a detection system for SNs..." not one of them said why.

 

[Labguy]

If you will take it, I will call your answer correct, since on question "(A)" it was so accurate and complete. I had thought that the second question would be easier, and since it mentioned all supernovae in general, you are also correct.

I mentioned no specifics about a star in the second question, so the only reasonable answer left would have to be the MASS of the "progenitor" star. We all know that the neutrinos radiate first and unempeded, so they would always reach us first. In a star of large mass, the propogation of the reactions creating the EM radiation would take longer to complete and "reach the edge" from where we could see the radiation. The reverse would be the case for a star of smaller mass. SO, a long "neutrino-light" delay means a larger star exploding than one with a shorter "neutrino-light" delay.

Very imperssive answer!
Your Question:

 

[J-Man]

Excellent. (Sorry it took so long to get back. Spring fever...)

Today's topic is binary stars. Several questions, mostly in a multiple choice format.

1) Which of these is the best description of the orbital motion of a binary star system?
A) The less massive star orbits around the more massive one.
B) Both stars orbit around a common center of mass.
C) The dimmer star orbits around the brighter one.
D) Each star orbits around the other.

2) For visual binaries, which of these stars is usually designated the 'primary' component?
A) the heaviest
B) the most iron-rich
C) the dimmest
D) the brightest

3) Of the four main types of binary stars, which is detected by 'wobbles' in a point of light's motion across the sky?
A) eclipsing
B) visual
C) astrometric
D) spectroscopic

4) Of the four main types of binary stars, which can be 'resolved' into its separate components through a telescope?
A) astrometric
B) eclipsing
C) spectroscopic
D) visual

5) True or false: Planets can exist in stable orbits in a binary star system.

6) Observations of a visual double must record two characteristics: the angle orientation of the secondary with respect to the primary, and ... what?
A) angular separation between the two stars
B) parallax of each star
C) linear separation between the two stars
D) mean differences in the solar spectra

7) What astronomer coined the phrase 'binary star'?
A) Sir Edmond Halley
B) Sir William Herschel
C) Clyde Tombaugh
D) Asaph Hall
E) J-Man

 

[chroot]

Originally posted by J-Man
1) Which of these is the best description of the orbital motion of a binary star system?
A) The less massive star orbits around the more massive one.
B) Both stars orbit around a common center of mass.
C) The dimmer star orbits around the brighter one.
D) Each star orbits around the other.

B

2) For visual binaries, which of these stars is usually designated the 'primary' component?
A) the heaviest
B) the most iron-rich
C) the dimmest
D) the brightest

D

3) Of the four main types of binary stars, which is detected by 'wobbles' in a point of light's motion across the sky?
A) eclipsing
B) visual
C) astrometric
D) spectroscopic

C

4) Of the four main types of binary stars, which can be 'resolved' into its separate components through a telescope?
A) astrometric
B) eclipsing
C) spectroscopic
D) visual

D

5) True or false: Planets can exist in stable orbits in a binary star system.

A tentative true. In certain systems, resonances exist in which a planet could conceivably exist in a stable orbit. The vast majority of orbits in most binary systems, however, throw the planet into a star, or out into space.

6) Observations of a visual double must record two characteristics: the angle orientation of the secondary with respect to the primary, and ... what?
A) angular separation between the two stars
B) parallax of each star
C) linear separation between the two stars
D) mean differences in the solar spectra

A

7) What astronomer coined the phrase 'binary star'?
A) Sir Edmond Halley
B) Sir William Herschel
C) Clyde Tombaugh
D) Asaph Hall
E) J-Man

B

- Warren

 

[J-Man]

chroot answered:
1=B
2=D
3=C
4=D
5=true
6=A
7=B

Very good!
I would also have accepted "E" for question 7 even though it is completely wrong. I have a soft spot for brown-nosers.

It is now your turn for a question.

 

[chroot]

Since it's Messier marathon season, why don't we do a set of questions on the Messier catalogue? These questions can all be answered easily with the right references -- I have no idea if the information is on the web, though.

1) List the Messier catalogue objects which are thought to have been recorded erroneously. Extra points for describing which nearby objects are thought were intended.

2) List the Messier objects that were actually added to the catalogue by third parties long after both Messier and his assistant died.

- Warren

 

[J-Man]

Originally posted by chroot
1) List the Messier catalogue objects which are thought to have been recorded erroneously. Extra points for describing which nearby objects are thought were intended.

2) List the Messier objects that were actually added to the catalogue by third parties long after both Messier and his assistant died.

1) Most Messier objects are nebulae, star clusters or galaxies. There are 3 that are not.

i) M24 - A Milky Way star cloud which contains an 11th mag open cluster (NGC 6603). The NGC erroneously takes this cluster for M24, although Messier without doubt described the star cloud.
ii) M40 - Binary star system that Messier found and logged when looking for a (non-existant) nebula reported by 17th century observer Jan Hevelius.
iii) M73 - a group or an asterism of four 10th to 12th magnitude stars, which Messier measured at the same time when he determined M72's position.

Some versions of the Messier list omit some or all of these objects, though they are without doubt real objects, and their appearance was correctly described by Messier. However, these objects can be hardly classified as deep sky objects at all: M40 and M73 are multiple stars (or asterisms), while M24 is perhaps no object at all, but a "window in the dust" obscurring the Milky Way, and/or a larger portion of a spiral arm.

Missing objects: Of the 103 objects in the full printed version of Messier's catalog, only 99 show up as described at their position, while four objects are missing: M47, M48, M91, and M102. For at least three of these entries, the described objects exist, but Messier gave a wrong position, only the case of M102 is still controversially discussed.
-------------
2) Additional Messier objects:
7 objects were added to the Messier list by others; objects M104 to M110.
See this page for more info on these objects: http://www.maa.agleia.de/Messier/addition.html

 

[chroot]

J-Man,

Correct on all counts. Good job!

- Warren

 

[J-Man]

OK, let's think about asteroids for a bit. I'll use the multiple choice format again for several (loosely) related questions.

Question 1:
The first asteroid, 1 Ceres, was discovered on Jan 1, 1801, who discovered it?
A) WIlliam Hershel
B) Giuseppe Piazzi
C) Edwin Hubble
D) Issac Newton
------------------------------------
Question 2:
Asteroids that come within the orbit of the Earth at their perihelions (closest approach to the Sun) are known as ___________ asteroids.
A) Aten
B) Apollo
C) Trojan
D) Amors
------------------------------------
Question 3:
Asteroids that are always closer to the Sun than the Earth are called __________

asteroids.
A) Apollo
B) Amor
C) Trojan
D) Aten
------------------------------------
Question 4:
If all of the asteroids were lumped together, they would make a planet bigger than

Jupiter.
True or False
------------------------------------
Question 5:
What asteroid did the NEAR Shoemaker mission recently land on?
A) 243 Ida
B) 3 Juno
C) 433 Eros
D) 951 Gaspra
------------------------------------
Question 6:
The Galileo spacecraft had encounters with two asteroids while enroute to Jupiter, what are the names of the asteroids?
A) 2062 Aten and 4 Vesta
B) 243 Ida and 951 Gaspra
C) 2212 Hephaistos and 511 Davida
D) 52 Europa and 911 Agamemnon
------------------------------------
Question 7:
Which asteroid was discovered to have its own satellite?
A) 951 Gaspra
B) 243 Ida
C) 433 Eros
D) 3 Juno
------------------------------------
Question 8:
Between the main concentrations of asteroids in the main belt are relatively empty regions known as the _______________.
A) Kuiper belt
B) Cassini's division
C) Kirkwood gaps
D) Van Allen belts

 

[Nicool003]

J-man can we erm try to keep it 3 questions or below next time?

 

[J-Man]

I'm sorry. I guess I got carried away.
How about the 1st person to get half of em right gets the next question?

 

[axeeonn]

Question 1:
B) Giuseppe Piazzi

Question 2:
B) Apollo

Question 3:
D) Aten

Question 4:
False

Question 5:
C) 433 Eros

Question 6:
B) 243 Ida and 951 Gaspra

Question 7:
C) 433 Eros

Question 8:
B) Cassini's division

 

[J-Man]

axeeonn answered:
Question 1:
B) Giuseppe Piazzi

Question 2:
B) Apollo

Question 3:
D) Aten

Question 4:
False

Question 5:
C) 433 Eros

Question 6:
B) 243 Ida and 951 Gaspra

Question 7:
C) 433 Eros

Question 8:
B) Cassini's division

Numbers 1 through 6 are correct; numbers 7 & 8 were incorrect
The answer list is:
1=B
2=B
3=D
4=false
5=C
6=B
7=B
8=C

You got 6 out of 8, but you only needed 4 so your turn axeeonn.

 

[axeeonn]

Use Hubble's law to determine the age of the universe (assuming Ho is actually costant).

If you use Ho = 70km/s/MPc, you get... ?

 

[chroot]

The Hubble time (t_H, age of the universe) is defined as 1/H₀. In term of years,

t_H [yr] = 9.78 x 10¹¹ [yr km / s Mpc] / H₀ [km/s/Mpc]

If H₀ = 70 km/s/Mpc, then t_H = 13.97 Gyr.

- Warren

 

[cragwolf]

The Hubble time is not necessarily the age of the universe. Indeed, it's unlikely to be so. But it's close. The age of the universe, at least in the most successful model, depends on the mass/energy density, curvature and size of the cosmological constant. The actual formula for the age of the universe, as derived by the Friedman-Lemaitre model is given by:

Ht = [inte] dy / y(Ω_m y^3 + Ω_R y^2 + Ω_λ)^1/2

where the integral goes from y=1 to y=[oo], and

y = 1+z (where z is the redshift)
Ω_m is the mass/energy density term
Ω_R is the curvature term
Ω_λ) is the cosmological constant term
H is the current Hubble constant
t is the age of the universe

Current data seem to suggest:

Ω_m = 0.27
Ω_R = 0
Ω_λ = 0.73
H = 71 km/s/Mpc

Anyone care to try out the integral?