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

[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

 

[Nereid]

Where in the universe?

Is Alpha, Beta, and Maxwell (all three)?
Hint: these three are different from the rest.

Bonus question: why are they different?

 

[Jeebus]

Originally posted by Nereid
Is Alpha, Beta, and Maxwell (all three)?
Hint: these three are different from the rest.

Bonus question: why are they different?

No idea, Nereid, nice question. There not all rays? :) I dunno...

 

[Lonewolf]

Would they be on Venus, and the only features on the planet not named after a female? Maxwell Montes being the only feature named after a male.

 

[Nereid]

Correct Lonewolf!

Want to try to bonus question? To re-state a little more clearly: Why were Alpha Regio, Beta Regio, and Maxwell Montes NOT given female names?

Anyway, it's your turn.

 

[Lonewolf]

Hmm, Alpha Regio and Beta Regio were already there before. Maxwell Montes was named after James Maxwell. I'm not sure were Alpha and Beta weren't changed, or why Maxwell is the only male on a feminine planet. Perhaps you'd like to explain?

Anyway, question time, sticking to a Venus theme. Earth and Venus are very similar in mass and radius, and other features. Why is it then that their atmospheres are dramatically different?

 

[Nereid]

Features on the surface of Venus

Maxwell is the most prominent feature on Venus, as seen in radar. Venus was the first target for radar astronomers (after the Moon), starting in 1961. The Alpha and Beta regions were also observed, and confirmed early.

When the IAU got around to formalising the process of assigning names to solar system objects (1973?), they decided to give only female names to features on Venus (and there are other rules too, see the link). However, they made an exception for Maxwell, Alpha, and Beta, because these were already established.
http://astrogeology.usgs.gov/Projects/PlanetaryMapping/VenusMappers/AppendC.html

 

[Labguy]

Originally posted by Lonewolf
Hmm, Alpha Regio and Beta Regio were already there before. Maxwell Montes was named after James Maxwell. I'm not sure were Alpha and Beta weren't changed, or why Maxwell is the only male on a feminine planet. Perhaps you'd like to explain?

Anyway, question time, sticking to a Venus theme. Earth and Venus are very similar in mass and radius, and other features. Why is it then that their atmospheres are dramatically different?

The lighter gasses (originally) were lost due to higher temperatures because of proximity to the sun. This left the more dense gasses, leading to higher densities and the start of the (increasing) "greenhouse effect". The pressure of Venus' atmosphere at the surface is `90 atmospheres. It is composed mostly of carbon dioxide. There are several layers of clouds many kilometers thick composed of sulfuric acid. This dense atmosphere produces a run-away greenhouse effect that raises Venus' surface temperature by about 400 degrees to over 740 K (hot enough to melt lead). Venus' surface is actually hotter than Mercury's despite being nearly twice as far from the Sun.

(Answer stolen from internet, just to get specifics right)...

 

[Lonewolf]

Cool, thanks Nereid. Labguy, you got the question right, so ask away!

 

[Labguy]

Originally posted by Lonewolf
Cool, thanks Nereid. Labguy, you got the question right, so ask away!

Ok, thanks.

Question(s):

(1)What is the name given to very large wisps of dust which cannot be seen in visible light, and are only ~15-30 K?

(2) Where are they found?

(3) What's the energy source of the (very low) tempreature?

 

[Labguy]

Originally posted by Labguy
Ok, thanks.

Question(s):

(1)What is the name given to very large wisps of dust which cannot be seen in visible light, and are only ~15-30 K?

(2) Where are they found?

(3) What's the energy source of the (very low) tempreature?

Ok, guys. You'll find the answer in the same subject/page as the "T-Tauri" answer at the top of this page!

 

[marcus]

Originally posted by Labguy
Ok, thanks.

Question(s):

(1)What is the name given to very large wisps of dust which cannot be seen in visible light, and are only ~15-30 K?

(2) Where are they found?

(3) What's the energy source of the (very low) tempreature?

(1) dust disks
(2) found around stars (e.g. T Tauri stars)
(3) the starlight heats them to the (very low) temperature

 

[Labguy]

Originally posted by marcus
(1) dust disks
(2) found around stars (e.g. T Tauri stars)
(3) the starlight heats them to the (very low) temperature

Close, but only #3 is correct.

 

[marcus]

Originally posted by Labguy
Close, but only #3 is correct.

well, there are "twisters"

?

 

[Nereid]

1) interstellar cirrus
2) just about everywhere, but they're particularly noticable above the galactic plane
3) the ambient radiation, from stars, keeps them warmer than 2.7^oK. As they're more or less transparent, they don't get a chance to cool down below this temperature, and they do absorb starlight, so they are warmer than the CMB.

They were first found (convincingly) by IRAS, and caused astronomers to go back and re-do an awful lot of 'absorption' calculations; previously interstellar absortion was assumed to be more or less uniform; the cirrus showed that is was highly irregular and patchy.

 

[Labguy]

Originally posted by Nereid
1) interstellar cirrus
2) just about everywhere, but they're particularly noticable above the galactic plane
3) the ambient radiation, from stars, keeps them warmer than 2.7^oK. As they're more or less transparent, they don't get a chance to cool down below this temperature, and they do absorb starlight, so they are warmer than the CMB.

They were first found (convincingly) by IRAS, and caused astronomers to go back and re-do an awful lot of 'absorption' calculations; previously interstellar absortion was assumed to be more or less uniform; the cirrus showed that is was highly irregular and patchy.

That's right on all three points. It was an IRAS site I found this on, several years ago.

That makes it your question!

 

[Nereid]

missing mass

We've all read about the 'missing mass' or 'dark matter' which is supposed to exist in the galactic halo and bulge.

Red dwarf stars have been observed for a long time (the closest star - apart from the Sun - to us is a red dwarf); more recently even fainter stars - brown dwarfs - have been discovered. There must also be even smaller objects alone out in interstellar space, formed independently or ejected from a nascent planetary system.

How can we be so sure that these isolated faint objects - and others such as cold white dwarfs, neutron stars, even stellar-mass black holes - cannot comprise more than a small fraction of the halo or bulge missing mass?

 

[Labguy]

Originally posted by Nereid
We've all read about the 'missing mass' or 'dark matter' which is supposed to exist in the galactic halo and bulge.

Red dwarf stars have been observed for a long time (the closest star - apart from the Sun - to us is a red dwarf); more recently even fainter stars - brown dwarfs - have been discovered. There must also be even smaller objects alone out in interstellar space, formed independently or ejected from a nascent planetary system.

How can we be so sure that these isolated faint objects - and others such as cold white dwarfs, neutron stars, even stellar-mass black holes - cannot comprise more than a small fraction of the halo or bulge missing mass?

I would have to guess that you are looking for "galactic rotation rates", without a website to quote.

If you limit your question as asked, galactic bulge and halo, then any more significant (missing) mass in the bulge would cause stars, and spiral arms such as ours, to rotate faster than observed and faster than the "known mass" formulae would predict. If the halo had significantly more (missing) mass, and the bulge remained as observed, then (1) rotation would be slower than observed and (2) there would be more unstability and disruption in the disk-shaped spiral arms, in the case of a spiral galaxy.

In Elliptical galaxies the same would be true for rotation rates, without a central "bulge". As of now, the only increased rotation rates seen, in most galaxies, is the rapid increase near the cores indicating a massive BH in the center. M-87 is calculated to have a Billion Ms BH in the core, ours (Milky Way Galaxy) is ~1 million Ms.

 

[Nereid]

Only the Milky Way

These are all good points Labguy.

My fault for not asking the question sufficiently clearly.

First, I am only asking about the Milky Way halo and bulge, not other galaxies.

Next, you're right; it is the rotation curves which provide clear indications that the amount of mass is greater than what can be observed as luminous stars, gas, and dust.

What is the missing mass? There are good reasons for thinking it cannot be faint, unobserved objects such as (distant) red dwarfs, brown dwarfs, isolated planets, etc. I'm not counting rocks, pebbles, even smallish asteroid-sized bodies in this; nor 'big dust'.

My question is: why are we confident that these faint objects (brown dwarfs etc) cannot comprise more than a small fraction of the missing mass?

 

[Labguy]

Brown Dwarfs; From a stellar formation graph and formula page:

These so- called "aborted stars" have a mass around .08Ms, and can't convert hydrogen into helium (Their cores never reach the threshold temperature for hydrogen burning.). The only energy radiated is due to gravitational contraction (Kelvin-Helmholtz contraction), which is why they are difficult to detect unless they are located near us. To determine if brown dwarfs contribute substantially to the dark matter mass, we need to estimate their number. We can use the Stellar Mass Function, F(M) (proportional to M-2.33), to extrapolate the number of brown dwarfs from the numbers of more massive stars. If F(M)dM = the number of stars with mass between M and M+dM, then the total mass contribution from brown dwarfs can be written as (M)(F(M))dM. The question is, how does F(M) behave for very low M? F(M) is proportional to M-2.33 only for main sequence stars, not for brown dwarfs. In general, giant clouds of gas and dust collapse, then fragment. The smaller fragments, which become K and M stars, are more abundant then the larger fragments, which become O and B stars. However, the amount of small fragments drops off right near the size needed to make brown dwarfs, limiting the number of brown dwarfs that could exist, and also providing an uncertainty as to that number.

If all the dark matter is composed of brown dwarfs, we would need one brown dwarf every 30 cubic ly of space, many trillions over the entire Milky Way. The number of known brown dwarfs and brown dwarf candidates in our section of the galaxy are exceedingly slim, however, making it unlikely that the density of the galaxy's brown dwarf population accounts for significant dark matter.

(Some original, some stolen text)

 

[Nereid]

Extrapolating the SMF suggests that there would be too few such low mass objects.

What observations have been made that show there are insufficient non-luminous (or low-luminosity) massive objects to account for the missing mass?

 

[Labguy]

Originally posted by Nereid
Extrapolating the SMF suggests that there would be too few such low mass objects.

What observations have been made that show there are insufficient non-luminous (or low-luminosity) massive objects to account for the missing mass?

Is this an additional question, or required as an answer to your last question? It wasn't specified.

 

[marcus]

Here is the original question:

Originally posted by Nereid

...How can we be so sure that these isolated faint objects - and others such as cold white dwarfs, neutron stars, even stellar-mass black holes - cannot comprise more than a small fraction of the halo or bulge missing mass?

"be so sure" suggests that N. is looking for observational evidence, does it not? The model of stellar formation predicts mass distributions, but is a model---it might even have to be modified some day, who knows? Here is the same question rephrased:

Originally posted by Nereid

...What observations have been made that show there are insufficient non-luminous (or low-luminosity) massive objects to account for the missing mass?

This is a really interesting question which I don't think has been addressed yet in this thread. How come we're so sure---on the grounds of what observational evidence? How did we "see" the absence of billions of invisible small-size stars? Someone knows the answer here, I expect (besides Nereid, I mean). Let's hear from some of you others!

 

[Labguy]

Originally posted by marcus
Here is the original question:



"be so sure" suggests that N. is looking for observational evidence, does it not? The model of stellar formation predicts mass distributions, but is a model---it might even have to be modified some day, who knows? Here is the same question rephrased:



This is a really interesting question which I don't think has been addressed yet in this thread. How come we're so sure---on the grounds of what observational evidence? How did we "see" the absence of billions of invisible small-size stars? Someone knows the answer here, I expect (besides Nereid, I mean). Let's hear from some of you others!

Ok, then someone else can answer what Nereid "might have thought" instead of answering the question as I did.

I think questions, like my last 3-parter, should all be asked at one time instead of "comebacks" saying that "you're right, but now add more". I can't guess ahead as to what someone "might have meant", just answer the question as asked.

 

[Nereid]

The original question again

How can we be so sure that these isolated faint objects - and others such as cold white dwarfs, neutron stars, even stellar-mass black holes - cannot comprise more than a small fraction of the [clarification: Milky Way] halo or bulge missing mass?

Galaxy rotation curves - including those of the Milky Way - are strong observational evidence that there is missing mass; they don't give any clues as to what it is, or is not.

Extrapolation of the SMF suggests that lower mass compact objects may not make up very much of the missing mass; it's not enough to give much confidence (as marcus correctly noted). It also doesn't address "cold white dwarfs, neutron stars, even stellar-mass black holes"

Hint: evidence for the existence of (non- or sub-)luminous massive, compact, halo objects

 

[Labguy]

Originally posted by Nereid
Galaxy rotation curves - including those of the Milky Way - are strong observational evidence that there is missing mass; they don't give any clues as to what it is, or is not.

Extrapolation of the SMF suggests that lower mass compact objects may not make up very much of the missing mass; it's not enough to give much confidence (as marcus correctly noted). It also doesn't address "cold white dwarfs, neutron stars, even stellar-mass black holes"

Hint: evidence for the existence of (non- or sub-)luminous massive, compact, halo objects

Originally posted by nightbat on the stellar astrophysics page; many observations:

Here are a few:

http://spaceflightnow.com/news/n0308/11halo/
http://arxiv.org/abs/astro-ph/0206126
http://aanda.u-strasbg.fr:2002/arti...092/aa1092.html
http://www.strw.leidenuniv.nl/information/normgal.html
http://xxx.lanl.gov/abs/astro-ph/9501068
http://www.star.bris.ac.uk/nam/abs_galaxy_dynamics.html
http://www.blackwell-synergy.com/li...03.06680.x/abs/

You will find many more on the internet.

If that's enough, give the credit to nightbat, and notify him that he answered the question here. Emphasis on "You will find many more on the internet."

 

[marcus]

Originally posted by Nereid
We've all read about the 'missing mass' or 'dark matter' which is supposed to exist in the galactic halo and bulge.

Red dwarf stars have been observed for a long time (the closest star - apart from the Sun - to us is a red dwarf); more recently even fainter stars - brown dwarfs - have been discovered. There must also be even smaller objects alone out in interstellar space, formed independently or ejected from a nascent planetary system.

How can we be so sure that these isolated faint objects - and others such as cold white dwarfs, neutron stars, even stellar-mass black holes - cannot comprise more than a small fraction of the halo or bulge missing mass?

I'll hazard a guess: by "microlensing" observations----which yield an upper bound on the abundance of massive dark objects

the original question is pretty clear---we take for granted that much of the Milkyway mass is dark in the sense that we can't detect radiation from it-----either it is stuff that shines too faintly to detect or that doesn't shine at all. That is not at issue here.

The question is, how do we know (based on what observations do we know) that this invisible mass does not consist of objects in the large-planet-to-small-star range?

The stellar-mass-distribution function is just an empirically arrived at thing with limited predictive power so we can't use it to exclude the possibility that at some time in Milkyway history a lot of un-shining massive objects formed (Nereid mentioned stellar-mass black holes, cold white dwarfs etc)

But people can actually see invisible massive objects by their gravitational-lens effect as they pass in the foreground of visible objects----microlensing. So they have been able to estimate how many dark massive objects there are.

 

[Nereid]

MACHO

Yep, marcus is right.

Nearly a decade ago now several long term research projects got underway to detect gravitational lensing of background stars. They had several objectives, one of which was to estimate the space density of MAC(H)Os - massive compact (halo) objects. As one of these passes between the line of sight between us and a distant star, it lenses the star's light, and we see a characteristic brightening then fading.

Although it's no longer maintained, the MACHO consortium's homepage (http://wwwmacho.mcmaster.ca/) has good background (including a photo of the Mt Stromlo observatory, now destroyed ). To read a particular paper - from the publications list - copy and paste the title into Google; to look up the results from other lensing projecs (e.g. OGLE), type the project name into Google.

There have also been dedicated HST searches for red dwarfs in the halo - far fewer were found than would be needed to comprise a significant fraction of the missing mass.

(you can do a simple calculation for yourself - given proxima centuri, distance ~ 4 ly, mag ~11, the nearest red dwarf - how far away would a similar red dwarf be if its observed mag were 25?)

Your turn marcus.

 

[marcus]

Originally posted by Nereid

Your turn marcus.

Sure. What is the name of Siobahn Morgan's dog?


[prof Morgan was the first person I know of to post an online
cosmology calculator that actually gives the recession speed
of an object of known redshift at the time it emitted the light
we are receiving from it.

http://www.earth.uni.edu/~morgan/ajjar/Cosmology/cosmos.html

be sure to put in 0.27 for matter density and 0.73 for Lambda or cosmological constant, then it will compute recession speeds and distances from whatever redshift you give it

Siobahn's homepage is
http://www.earth.uni.edu/smm.html ]

For extra credit, name 3 of Siobahn's favorite superhero comic book characters.

For optional, entirely voluntary additional extra credit: a quasar has been observed at redshift 6.4---with what speed was the quasar receding from us when it emitted the light?

 

[Labguy]

Originally posted by marcus
Sure. What is the name of Siobahn Morgan's dog?


[prof Morgan was the first person I know of to post an online
cosmology calculator that actually gives the recession speed
of an object of known redshift at the time it emitted the light
we are receiving from it.

http://www.earth.uni.edu/~morgan/ajjar/Cosmology/cosmos.html

be sure to put in 0.27 for matter density and 0.73 for Lambda or cosmological constant, then it will compute recession speeds and distances from whatever redshift you give it

Siobahn's homepage is
http://www.earth.uni.edu/smm.html ]

For extra credit, name 3 of Siobahn's favorite superhero comic book characters.

For optional, entirely voluntary additional extra credit: a quasar has been observed at redshift 6.4---with what speed was the quasar receding from us when it emitted the light?

Millie

Batman
Green Lantern
Aquaman

I have no "direct observations" to back this up.

 

[marcus]

Originally posted by Labguy
Millie

Batman
Green Lantern
Aquaman

I have no "direct observations" to back this up.

Your go, Labguy, right on all counts

I see you did not opt for the additional extra credit---a redshift 6.4 quasar was receding at 3 times c when it emitted the light we receive from it----or more accurately, by Siobahn's calculator, 2.88 c.