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

[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?

 

[axeeonn]

Hmmm, I think I will pass on that integral. ;)

chroot, you're up.

 

[cragwolf]

[zz)]

Hey chroot!

CHROOT!



Sorry to wake you up, but it's your turn to ask a question.

 

[marcus]

Originally posted by 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?

This is out of order---a question concerning the integral. There is a related formula for the age of the universe. Does anyone have an online source for it? The formula might result from cragwolf's integral.

To make writing it easier let S = Ω_λ^1/2
so that if Ω_λ = 0.73, S will be 0.84.

age = (2/3H) (1/2S) ln [(1+S)/(1-S)]

I came across this online and have lost the URL. Can anyone supply a reference? Don't want to interrupt the game, but would appreciate any help.

 

[chroot]

Originally posted by cragwolf
[zz)]

Hey chroot!

CHROOT!



Sorry to wake you up, but it's your turn to ask a question.

Sorry folks. I have been asked to leave this forum by Greg Bernhardt, the owner.

- Warren

 

[Labguy]

Originally posted by chroot
Sorry folks. I have been asked to leave this forum by Greg Bernhardt, the owner.

- Warren

Why?

 

[Greg Bernhardt]

Please use the PM system for personal and off-topic questions.

Thanks

 

[Nicool003]

Hey guys sorry I haven't been around this thread much! I will be though! To get back on topic how about the person that asked the question to ask another one...

 

[marcus]

Axeeonn's turn to ask

Originally posted by Nicool003
Hey guys sorry I haven't been around this thread much! I will be though! To get back on topic how about the person that asked the question to ask another one...

That would be axeeonn who asked, on 5April:

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

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

This was the most recent question asked, so you are inviting
axeeonn to pose another.

[Long pause...]

I hope that, one way or another, you get the game started back up because from what I've read it is phenomenal----really interesting stuff

 

[axeeonn]

Ok, let's try to get this rolling agian...

How many kilograms of hydrogen is converted to He in our sun per second?

 

[damgo]

6e11 kg/s.

 

[Labguy]

Originally posted by axeeonn
Ok, let's try to get this rolling agian...

How many kilograms of hydrogen is converted to He in our sun per second?

~700 million tons of hydrogen.

http://www.seds.org/billa/tnp/sol.html

Should be ~6.35e11 Kg. H converted to He.

 

[axeeonn]

Damgo's turn, go go go!

 

[damgo]

Cool. Okay, the LIGO project is designed to detect gravitational waves from space by measuring the change in distance between two objects -- a laser and a far-away mirror -- as the gravitational wave passes by.

1) For an expected incoming gravitational wave, by what percentage will it alter distances as it passes by? (order of magnitude)

2) How long are the LIGO interferometer arms? (distance from laser to mirror)

3) So what amount of change in distance must LIGO be sensitive to, in order to detect gravitation waves?

 

[marcus]

Originally posted by damgo
Cool. Okay, the LIGO project is designed to detect gravitational waves from space by measuring the change in distance between two objects -- a laser and a far-away mirror -- as the gravitational wave passes by.

1) For an expected incoming gravitational wave, by what percentage will it alter distances as it passes by? (order of magnitude)

*An E-18 meter change over a length of 4000 meters. The fraction is 0.25 x 10^-21. This is 0.25 x 10^-19 percent.*


2) How long are the LIGO interferometer arms? (distance from laser to mirror)

*4000 meters*

3) So what amount of change in distance must LIGO be sensitive to, in order to detect gravitation waves?

E-18 meter


http://www.nature.com/nsu/nsu_pf/991111/991111-3.html

I am just copying what the guy in Nature Science Update said.
He said the expected change is E-15 millimeter over a length of 4000 meters, approximately. One arm stretches out while the other arm perpendicular to it gets shrunk by the same amount.
****added later****
Here's another web-reference, an excellent article inPhysics Today
from October 1999 by the director of LIGO Barry Barish

http://www.aip.org/web2/aiphome/pt/vol-55/iss-5/pdf/vol52no10p44-50.pdf[/URL]

He confirms that the fractional change in length that they expect to be sensitive to is on the order of 10^-21.

This would be 4E-18 meter in the arm length of 4000 meter.

 

[damgo]

^^^ yup... it's pretty amazing, no? Your go!