## Astronomy C

andrewbji
Member
Posts: 18
Joined: September 19th, 2009, 9:20 pm
Division: C
State: IL

### Re: Astronomy C

Out of curiosity, do you think there will be a lot on the physics portion on black holes? I'm thinking that they might ask something about the Schwarzchild Radius, but I can't think of other stuff. Is it possible to find the mass of a black hole (I thought it was infinite since it has the singularity, so just infinity)?
Also, I read from a book that black holes can change into a neutron star, is that true? I was kind of confused, because I thought once a black hole, always a black hole.

Finally, I got this question, does anyone have any ideas on how you figure it out: In the absence of extinction an O5 star has colors U-B=-1.1 and B-V=-0.3. Its absolute magnitude is MV=-5.6. Interstellar extinction has extinction ration A(B)/A(V)=1.34 and A(U)/A(V)=1.57. An O5 star is about 105 times more luminous than the Sun and has a radius that is 10 times larger than that of the Sun. What U-B and B-V colors would an O5 star be if detected behind a molecular cloud with extinction in V band of A(V)=3.0
Last edited by andrewbji on February 27th, 2010, 1:16 pm, edited 1 time in total.
2011 Scioly. Game on.

naureeng309
Member
Posts: 3
Joined: February 27th, 2010, 8:08 am
Division: C
State: NY

### Re: Astronomy C

Hello everyone !

I'm planning on doing the Astronomy event. I took it this year at Regionals and I did not do well =( There was a lot of conceptual stuff I didn't know. The calculations weren't too bad.

I want to do a lot better next year. What books and sites did you guys use to study astronomy? Any good links =]? Also, how did you guys study the deep sky objects? I have trouble identifying them based on images (I'm a total newbie lol). So any tips on how to get started ?

walkingstyx
Member
Posts: 61
Joined: December 8th, 2008, 10:22 pm
State: TX
Location: LASA

### Re: Astronomy C

Finally, I got this question, does anyone have any ideas on how you figure it out: In the absence of extinction an O5 star has colors U-B=-1.1 and B-V=-0.3. Its absolute magnitude is MV=-5.6. Interstellar extinction has extinction ration A(B)/A(V)=1.34 and A(U)/A(V)=1.57. An O5 star is about 105 times more luminous than the Sun and has a radius that is 10 times larger than that of the Sun. What U-B and B-V colors would an O5 star be if detected behind a molecular cloud with extinction in V band of A(V)=3.0
This question relates to color and dimming. The u-b and b-v values tell you what the color of the star is if there is nothing between it and you, but there is a molecular cloud, which obscures a lot of the light in the visible (v) range, but not much in the b or u ranges. This makes your value for v decrease by three. Then you use the ratios to figure how much you lose in the the other bands, i.e.. in the b band you lose 3*1.34 or a little less than 4.5, and in the u band you lose 3*1.57 or a little more than 4.5. You then use these to find the net change in the values, e.g. change in b-v= change in b minus change in v, and add them to the original values.

You will probably never see a question relating to color on the nationals test, so don't worry if you're a little confused. Also, I don't think you understood the idea of a singularity properly. It means that a blackhole has no volume, and thus has infinite density, despite having a finite mass. In fact you use this mass to calculate the swarzchild radius (which is the radius of the event horizon, not the blackhole itself). I would be surprised if you did not see anything relating to blackholes on the physics portion of the test. Also, I don't think blackholes can change into neutrons stars. They can decay, but I think they just slowly disappear rather than turn into neutron stars.

Naureeng390: have you checked the nationals website? It has excellent resources, including an online textbook, and lots of other helpful things. Use the powerpoint from the coaches clinic (http://www.tufts.edu/as/wright_center/p ... linic.html) as a starting point for assembling your collection of star pictures.
Nationals 2010- Astronomy: 4, Physics Lab: 4, Picture This: 4, It's About Time: 10, Optics: 2
Nationals 2009- Picture This: 4, It's About Time: 8, Astronomy: 9
Nationals 2008- Picture This: 2, Boomilever: 14

saturnian
Member
Posts: 40
Joined: January 5th, 2009, 5:14 am
Division: C

### Re: Astronomy C

Member
Posts: 1
Joined: February 24th, 2010, 12:44 pm
Division: C
State: TX

### Re: Astronomy C

its my school 4th time but riverwood allways wins eveytime we go

smarticle13
Member
Posts: 237
Joined: September 5th, 2009, 7:54 am
Division: B
State: TX
Location: if I told you, I would have to kill you

### Re: Astronomy C

is astronomy for division C like solar system for division B, except harder?
13 Medals:
Dynamic Planet (2nd place and 3rd place)
Elevated Bridge (3rd place)
Meteorology (1st place, 2nd place, 3rd place, 3rd place and another one at State!)
Shock Value (3rd place)
Solar System (1st place, 4th place)
We've Got Your Number (1st place)

rfscoach
Coach
Posts: 589
Joined: July 7th, 2008, 4:58 pm
Division: B
State: GA

### Re: Astronomy C

No. Closer to Reach for the Stars only more focused on a topic - currently galaxies, previously variable stars- and much more math. Physics based Astronomy rather than Observational Astronomy.
I am the Lorax. I speak for the trees. I speak for the trees, for the trees have no tongues.

wyu1229
Member
Posts: 13
Joined: January 26th, 2008, 1:37 pm

### Re: Astronomy C

Can anyone explain to me how to locate lyman, balmer and paschen absorption lines on a chart of stellar spectra and how you determine the strongest to weakest line? Essentially, its quesiton number 64 on 2002 Delaware Nationals; here's the link to the tests:
http://www.tufts.edu/as/wright_center/p ... astro.html
and can anyone explain to me what average rate of expansion is? and is there a formula for it? Thanks

wyu1229
Member
Posts: 13
Joined: January 26th, 2008, 1:37 pm

### Re: Astronomy C

Also, can someone post an exam that tests on all the 2010 DSO's? My team needs some practice problems on DSO's I have a lot of previous exams, but the DSO's change every year, I believe

smarticle13
Member
Posts: 237
Joined: September 5th, 2009, 7:54 am
Division: B
State: TX
Location: if I told you, I would have to kill you

### Re: Astronomy C

can someone give me some good sites for the absorption and emission spectrum?
13 Medals:
Dynamic Planet (2nd place and 3rd place)
Elevated Bridge (3rd place)
Meteorology (1st place, 2nd place, 3rd place, 3rd place and another one at State!)
Shock Value (3rd place)
Solar System (1st place, 4th place)
We've Got Your Number (1st place)

TheBalticSea
Member
Posts: 23
Joined: March 8th, 2009, 2:12 pm
State: NY
Location: W. Long Island --> Princeton

### Re: Astronomy C

I did astronomy at the western long island regionals and now my team is going to NY states, so i was just wondering how the two tests are different. Is the states test much harder? More physics? Is there a stellarium involved? (<-- i thought i heard someone mention something about that)
Thanks!
"Duct tape is like the force. It has a light side, a dark side, and it holds the universe together."
2012: Astro, Dynamic Planet, Optics, Remote Sensing
2011: Astro, Dynamic Planet, R.I.P. Picture This
2010: Astro, Picture This, Dynamic Planet, Write It Do It

gogofofo
Member
Posts: 14
Joined: April 26th, 2009, 9:09 am
Division: C
State: IL

### Re: Astronomy C

Can anyone explain to me how to locate lyman, balmer and paschen absorption lines on a chart of stellar spectra and how you determine the strongest to weakest line? Essentially, its quesiton number 64 on 2002 Delaware Nationals; here's the link to the tests:
http://www.tufts.edu/as/wright_center/p ... astro.html
and can anyone explain to me what average rate of expansion is? and is there a formula for it? Thanks
The average rate of expansion is given by Hubble's constant and is usually given in km/sec/Mpc. It is calculated, then, by dividing the recessional velocity of an object by its distance from us.
State
2009: 1st Forensics, 1st Astronomy, 3rd Remote Sensing
2010: 1st Forensics, 1st Astro
2011: 1st Forensics, 2nd Astro, 1st TPS

Nationals
2009: 10th Forensics, 3rd Astronomy, 11th Remote Sensing
2010: 1st Forensics, 9th Astronomy
2011: 2nd Forensics, 8th Astronomy, 10th TPS

TheBalticSea
Member
Posts: 23
Joined: March 8th, 2009, 2:12 pm
State: NY
Location: W. Long Island --> Princeton

### Re: Astronomy C

Can anyone explain to me how to locate lyman, balmer and paschen absorption lines on a chart of stellar spectra and how you determine the strongest to weakest line? Essentially, its quesiton number 64 on 2002 Delaware Nationals; here's the link to the tests:
http://www.tufts.edu/as/wright_center/p ... astro.html
and can anyone explain to me what average rate of expansion is? and is there a formula for it? Thanks
the formula is v= (Ho)(d)
^ that's supposed to be H sub o, or H naught (sorry! don't know how to use LaTeX)
H naught is roughly 71 km/sec/Mpc
This holds true for all galaxies that are redshifted.. which is pretty much all of them except the two nearest, M33 and M31.
"Duct tape is like the force. It has a light side, a dark side, and it holds the universe together."
2012: Astro, Dynamic Planet, Optics, Remote Sensing
2011: Astro, Dynamic Planet, R.I.P. Picture This
2010: Astro, Picture This, Dynamic Planet, Write It Do It

TheBalticSea
Member
Posts: 23
Joined: March 8th, 2009, 2:12 pm
State: NY
Location: W. Long Island --> Princeton

### Re: Astronomy C

Hello everyone !

I'm planning on doing the Astronomy event. I took it this year at Regionals and I did not do well =( There was a lot of conceptual stuff I didn't know. The calculations weren't too bad.

I want to do a lot better next year. What books and sites did you guys use to study astronomy? Any good links =]? Also, how did you guys study the deep sky objects? I have trouble identifying them based on images (I'm a total newbie lol). So any tips on how to get started ?
Space.com is a really good resource for general info. Also, I see you live in NY, so if you live within 70 miles (at least I think it's 70...) you might want to consider Columbia's science honors program, which is held on saturday mornings. They offer a lot of great science classes, many of them in astronomy and physics. Plus, it's free
and Brian Greene came to speak today!! that was pretty cool
"Duct tape is like the force. It has a light side, a dark side, and it holds the universe together."
2012: Astro, Dynamic Planet, Optics, Remote Sensing
2011: Astro, Dynamic Planet, R.I.P. Picture This
2010: Astro, Picture This, Dynamic Planet, Write It Do It

Oglop_Master
Member
Posts: 2
Joined: March 17th, 2010, 4:39 pm
Division: C
State: NC

### Re: Astronomy C

Hey... This seems like an odd question, but if you have a laptop that you bring in, is it legal to save websites that you can open without being connected to the Internet to use? So while I may be using my Internet browser to view the page, I won't be connected to the Internet.