ASTR121 SPRING 2008 BULLETIN BOARD

MESSAGE #55. Sun May 18 0:32:26 2008 . Lauren Woolsey wrote:

Today's Astronomy Picture of the Day talks about gold and neutron star collisions among other things...hauntingly familiar topics!

MESSAGE #54. Fri May 16 17:30:43 2008 . Arriel Widdes wrote:

Check this out, very strange and interesting!: http://news.yahoo.com/s/space/20080516/sc_space/bizarrestargetsstranger

MESSAGE #53. Wed Apr 30 1:33:17 2008 . Lauren Woolsey wrote:

Look it's PERFECT: The APOD today is exactly what we learned in lecture yesterday.

It's two galaxies colliding and one is a regular spiral while the other is a barred spiral!

MESSAGE #52. Tue Apr 29 14:03:22 2008 . Anthony Burnetti wrote:

http://www.badastronomy.com/bablog/2008/04/29/young-massive-and-dense-is-no-way-to-go-through-life-son/

Some really weird galaxies discovered long ago and far away by Hubble and the Keck...

MESSAGE #51. Sat Apr 26 21:25:40 2008 . Erin Grand wrote:

For anyone who wants to know why Kate and I were silent on Friday, I figured I would explain. Every year, GLSEN hosts Day Of Silence. It is a national youth movement in attempt to bring attention to the silence faced by lesbian, gay, bisexual and transgender people and their allies. The silence from us echoes that silence, which is caused by anti-LGBT bullying, name-calling and harassment.

Bother me in class if you want more information.

(As to not plagiarize, I should say that most of that I took from the DOS website, feel free to check it out at www.dayofsilence.com)

MESSAGE #50. Thu Apr 24 0:59:24 2008 . Lauren Woolsey wrote:

Astronomy Picture of the Day is always awesome, but today's is really incredible.

They have a picture of the constellation of Cygnus looking for hydrogen, and they've taken all the stars out of the picture, until you slide your mouse over it. Check it out, it's awesome.

http://apod.nasa.gov/apod/ap080424.html

MESSAGE #49. Wed Apr 23 20:49:09 2008 . Erin Grand wrote:

I think you've got the right idea. All you need to do to use the face that density is mass / volume. You can use the the equation of the radius of the black hole as the radius in the volume equation.

Does that help?

MESSAGE #48. Sun Apr 13 20:56:27 2008 . Jaime Gomez wrote:

Does anyone know how to prove number 49 on the hw. I end up getting mass divided by volume=kg^3 which is false.

MESSAGE #47. Mon Apr 7 2:47:38 2008 . Katherine Krivjanik wrote:

Does anyone know what exactly we are supposed to plot for "Plot your result for a system with a velocity of 15 km/s at 1 pc from 0 to 20 pc"?

MESSAGE #46. Sun Apr 6 18:51:38 2008 . John Molineaux wrote:

Can anybody make any sense of the last two pre-lab qestions? There's clearly some kind of velocity in there, but velocity of what?

MESSAGE #45. Thu Apr 3 10:36:54 2008 . Kelly Colwell wrote:

Did anybody figure out question 47? I know that the star must have a starting mass of 8M(sun), but I can't find a value for the mass after solar winds have swept away most of it. Is it between .4M(sun) and 2M(sun)? I think my notes are just confusing. :(

MESSAGE #44. Wed Apr 2 19:26:35 2008 . Jason Schwankert wrote:

Thank you!

MESSAGE #43. Tue Apr 1 17:10:53 2008 . Eran Bar Noy wrote:

Jason: You use the equation m - M = 5 logd - 5. m they give you, and M you can find out using the hint in the question (M will be an estimate).

MESSAGE #42. Mon Mar 31 22:49:06 2008 . Jason Schwankert wrote:

Anyone understand how to find the distance from earth of a supernova based on its maximum magnitude or know a good explanation of it. I can't find it in the book or searching online.

MESSAGE #41. Mon Mar 31 18:07:49 2008 . Lev Nagdimunov wrote:

Somebody know what about the stars discovered here is new: http://researchnews.osu.edu/archive/superyellow.htm

It seems to be an overcontact eclipsing binary. Am I wrong or is it that and we just haven't seen many?

MESSAGE #40. Thu Mar 27 15:21:43 2008 . Kelly Colwell wrote:

That relativity site was great! I have made many attempts at trying to understand it, and although it is still confusing (it probably always will be), I think I made some headway! Haha

MESSAGE #39. Wed Mar 26 13:15:50 2008 . Anthony Burnetti wrote:

It looks as though Titan might have a subsurface water/ammonia ocean too! Looks like it's not just the Jovian satellites...

http://www.sciam.com/article.cfm?id=signs-of-hidden-ocean-under-titans-crust

http://www.sciencedaily.com/releases/2008/03/080320150828.htm

As near as I can tell from the press release the evidence comes from the surface of Titan having shifted several kilometers relative to its interior which is assumed to be tidally locked with Saturn over the time Cassini has been there. I don't know if they've done enough flybys to use the gravitational effects to get an idea as to the interior.

MESSAGE #38. Tue Mar 11 19:21:43 2008 . Richard O'Steen wrote:

NASA is having Cassini make a flyby through Enceladus' emission plumes tomorrow, sounds interesting:

http://news.bbc.co.uk/2/hi/science/nature/7289670.stm

MESSAGE #37. Thu Mar 6 3:50:51 2008 . William Updegraff wrote:

The Onion-Shaq Terrified Of Phoenix Suns After Reading About Supernovas

http://www.theonion.com/content/news/shaq_terrified_of_phoenix_suns

MESSAGE #36. Fri Feb 29 0:46:33 2008 . Joshua Dingott wrote:

We touched on relativity but never really talked to much about it. In case we do talk about it again or in case anyone is interested this entertaining interactive clip helps make understanding the concepts of relativity a little more manageable. Enjoy! http://www.onestick.com/relativity/

MESSAGE #35. Fri Feb 29 0:40:53 2008 . Eran Bar Noy wrote:

So for anyone who was with me at the observatory last semester or who happens to know about gravitational lensing, Hubble has recently seen a double Einstein Ring. The images can be seen at http://hubblesite.org/newscenter/archive/releases/exotic/2008/04/image/a/ and there is a link there to the rest of the story. For those who don't know, gravitational lensing is when some light emitting source is directly behind another, really massive one (as we see it). Really, these objects are very far apart, but since the front object is so massive, it even bends light, and it seems to us as if the back object is in more than one place all around the front object. If the two are perfectly lined up, an entire ring is formed, called an Einstein Ring. So here is a double!

MESSAGE #34. Wed Feb 27 12:01:53 2008 . Arriel Widdes wrote:

I made a picture to accompany last week's discussion activity: Located Here

I'm also working on ripping some relevant cartoon episodes (they'll be up by the end of the week, I think) ^^

MESSAGE #33. Sun Feb 17 22:13:31 2008 . Richard O'Steen wrote:

The copy of the book I have is only on the second part of the course and starts at chapter 18. Could someone tell me what the sections from 17 for lab tomorrow are about so I can find some other source? (Wikipedia ftw!)Thanks in advance -Ricky

MESSAGE #32. Sun Feb 17 17:22:29 2008 . Valerie Klavans wrote:

There is a new, interesting news release from NASA about the surface of Titan. Titan has a vast amount of hydrocarbons in liquid form which surpasses Earth's reserves by far. Since all life on Earth is carbon-based, data from Titan may hold many answers to the origins of life in the universe.

Here is the url to the news release:

http://www.nasa.gov/mission_pages/cassini/media/cassini-20080213.html

MESSAGE #31. Wed Feb 13 13:45:47 2008 . Kristin Rutkowski wrote:

Hi Kelly, I'm not sure if this will help, but a few times I had to go back to Y1 and enter in a smaller number, let the solver get that answer, then go back and try again the larger number in Y1. Then go back into the Solver and don't change anything (leave the domain the default -1e99 to 1e99, and leave the current value of X where it is). This seemed to fix any problems I had with it.

MESSAGE #30. Tue Feb 12 13:37:46 2008 . Kelly Colwell wrote:

Using the solver, I couldn't get answers for the 3rd equation for Galaxies that had a ∆λ/λ greater than 1. How did you guys do it?

MESSAGE #29. Tue Feb 12 12:28:45 2008 . Ian Mitchell wrote:

i too am having the same problem

MESSAGE #28. Mon Feb 11 22:41:40 2008 . Jason Schwankert wrote:

Is anyone else having trouble finding the resonances for the lab. I still can't figure out how to get them. My pre-lab isn't helping either.

MESSAGE #27. Mon Feb 11 21:43:56 2008 . Lauren Woolsey wrote:

So I totally forgot I had this, it's from my high school TechConnect club.

http://laurenwoolsey.com/

MESSAGE #26. Mon Feb 11 1:17:21 2008 . Erin Grand wrote:

You're welcome!

MESSAGE #25. Sun Feb 10 19:19:35 2008 . Kristin Rutkowski wrote:

Thanks for posting the help, Erin!

MESSAGE #24. Sun Feb 10 14:33:06 2008 . Erin Grand wrote:

Opps, I have a TI-83 calculator, not a TI-89. Sorry about that!

MESSAGE #23. Sun Feb 10 13:32:21 2008 . Erin Grand wrote:

For help solving for "v" in the 2nd and 3rd equations, use solver on a graphing calculator. I don't know if the steps would be the the same for other calculators but this is what I did on the TI-89.

Step 1. Set the equation equal to 0. Step 2. Type the equation into Y1. Step 3. Go to MATH and press 0 (or go to Solver). Step 4. Press the up arrow, and make sure that eqn: 0=Y1. Press enter. Step 5. Type in what you expect to get in x=. Step 6. With your cursor in x=, press alpha and then enter. What appears in x= should be your answer.

:) Let me know if this doesn't make sense or you need more help.

-Erin Grand

MESSAGE #22. Sun Feb 10 13:08:36 2008 . Katherine Krivjanik wrote:

I used the quadratic to solve for v in the second equation. I'm still not sure about how to solve for the third.

MESSAGE #21. Sun Feb 10 12:39:04 2008 . Jesus Careaga wrote:

heyy evryone this is kinda cool, some old astronomy history and a lunar eclipse is coming up in the US and Canada.

http://news.yahoo.com/s/space/20080208/sc_space/howalunareclipsesavedcolumbus.

yea i also have the same question as arriel, the first questions are easy for each galaxy, but the rest get a little complicated.

MESSAGE #20. Sun Feb 10 11:05:42 2008 . Arriel Widdes wrote:

does anyone have equations where its v = everything else? The first one is easy - v = /\lambda/lambda * c; however, I can't seem to get a similar v = for the second and third equations...

MESSAGE #19. Mon Feb 4 11:40:10 2008 . Katherine Krivjanik wrote:

Oops, that was what I meant to type, and the assumption that I did the work using. I must have just switched the signs.

MESSAGE #18. Mon Feb 4 10:30:56 2008 . Arriel Widdes wrote:

Kate, it's simple: re-assign your variables! make it so that M >> m, and then you just make the change in every piece of you equation.

MESSAGE #17. Sun Feb 3 17:28:38 2008 . Katherine Krivjanik wrote:

I have a general idea of where to go, the only problem is that I have m in the denominator of the final answer rather than M.

F = (M + m)a

Fg = G(Mm)/r^2 = (M + m)a

ag = G(Mm)/(M + m)r^2

If we assume that M << m: ag = G(Mm)/Mr^2 = Gm/r^2

ag = ac

ac = v^2/r

Gm/r^2 = v^2/r

Gm/r = v^2

v = 2(pi)r/P

Gm/r = [2(pi)r/P]^2 = 4[(pi)^2]r^2/p^2

p^2 = 4[(pi)^2]a^3/Gm

Can anyone find a way to get M into the denominator instead?

MESSAGE #16. Sun Feb 3 17:07:30 2008 . Erin Grand wrote:

The prelab is a bit confusing. I have a list of equations written out with the variables defined. However, I do not understand where to go from here. What is meant by "equate" and "find a relation"?

I'm currently trying to work backwards, knowing Newton's form of Kepler's Third Law and that's isn't working well either.

Does anyone have any help?

MESSAGE #15. Sat Feb 2 0:14:52 2008 . Lev Nagdimunov wrote:

Here is something I am thinking about attending, it should be interesting. Sent to me by my cousin who works as a contractor for IBM in Goddard. It's a symposium, here is a description as given by them (in an email to NASA employees):

The 46th Robert H. Goddard Memorial Symposium, "Exploration to Commercialization: Going to Work in Space," will be held on March 4-6, 2008 at the Greenbelt Marriott in Greenbelt, Md. The Symposium is an excellent opportunity for Goddard's civil servants and contractors to learn more about the history and current state of space exploration and commercialization, and collectively discuss new plans and prospects for the future of humanity in space.

This symposium, sponsored by the American Astronautical Society and supported by Goddard, brings together leaders in government, industry, academia, and entrepreneurs. Highlights include keynote talks by NASA's Administrator Michael Griffin, and NASA's Associate Administrator for Science Alan Stern. ---

It'll be held at 6400 Ivy Lane, which is 3 miles from campus. If I go, I am probably going to take the metro there because there is a stop nearby. Cost is $40 for students (and in the order of $400 for everyone else, sorry Professor?). Here is the program schedule:

http://www.astronautical.org/index.php?option=com_docman&task=doc_download&gid=70&Itemid=129

Here is the link to register:

http://www.astronautical.org/marchreg/register_march08.php

And more info available on http://astronautical.org

MESSAGE #14. Fri Feb 1 22:52:15 2008 . Arriel Widdes wrote:

Hi all. I'd like to recommend "Fabric of the Cosmos" by Brian Greene, for those who are interested in a very physical take on, well, the cosmos. :P It's a good read, I promise.

(I also have a copy if someone's bold enough to ask to borrow it...^_^ )

MESSAGE #13. Fri Feb 1 21:59:00 2008 . Matthew Moriarty wrote:

On Thursday, February 21st the Carnegie Institute for Science is hosting a lecture in DC entitled "Mysteries of the Dark Universe." The subject is the dark matter and dark energy that seem to compose an estimated 95% of the universe. Exactly how much there is is a *huge* question for cosmology because it will determine whether our universe will contine to expand or eventually collapse back in on itself. The lecturer is Edward "Rocky" Kolb from U of Chicago. I'm not sure exactly where the institute is but I know the closest metro stop is Dupont Circle. I'll post again when I find out real directions. Here's the link: http://www.ciw.edu/events/upcoming ~Matt Moriarty

MESSAGE #12. Fri Feb 1 12:30:48 2008 . Kristin Rutkowski wrote:

Here's the URL for the scientific notation page: http://janus.astro.umd.edu/cgi-bin/astro/scinote2.pl.

I know that the Physics department holds scientific colloquia, and that there are speeches at the observatory on open house nights, but there are also a few other places in the area that have lectures on space topics that are usually pretty interesting.

Up in Baltimore the STScI (Hubble place on Johns Hopkins campus) has a lecture the first Tuesday of every month. If the sky is clear, their observatory is also open afterwards (along with every Friday, same as the Maryland Science Center). The topic next Tuesday is "Quasars and Galaxies Over Cosmic Time". http://hubblesite.org/about_us/public-talks.shtml

And a few miles east on 193 at Goddard are scientific colloquia every Friday at 3:30. You have to email them ahead of time (the email link is on their page) to be added to the access list, though. http://scicolloq.gsfc.nasa.gov/ According to Dr. Hamilton's CV, he was invited to give a lecture there on Neptune's satellites, but I couldn't find it on their webpage.

I'll probably drive to Goddard after our discussion sections, if anyone wants to share a ride. (up to Hopkins, also)

MESSAGE #11. Thu Jan 31 20:08:32 2008 . Edgar Santillan wrote:

Hey everyone just wondering what scientific notation site we have to use because the website on the homework is not working for me so I went straight to the janus.umd.edu site where I found a scientific notation page. I'm just wondering if this one is it?

MESSAGE #10. Thu Jan 31 18:32:06 2008 . Ian Mitchell wrote:

here is an interesting site i found a few months ago:

http://telescope.org/index.php

it has a lot of information, but the part that i found to be of most interest is they run a robotic observatory in Tenerife that anyone can use for free. you just need to sign up, submit the coordinates and other camera settings like exposure or filters to be used. i have seen similar site, but they cost money for a membership or are charged per observing time. the downside is it takes a while for your pictures to get shot, as they monitor the sky for clouds and such and only shoot when its clear. the site seems to be getting popular, as it is taking longer and longer to complete requests. i believe the telescope is currently down for upgrading, but sign up now and check back latter.

MESSAGE #9. Thu Jan 31 14:47:21 2008 . Anthony Burnetti wrote:

http://webphysics.davidson.edu/alumni/MiLee/java/bb_mjl.htm

Here's a java applet that lets you adjust the temperature on the bar on the bottom, and it shows the blackbody radiation curve and the visual color that would be produced. Drag the curve with your mouse to get to temperatures further than the scroll bar lets you get to.

MESSAGE #8. Thu Jan 31 13:21:01 2008 . Prof. Doug Hamilton wrote:

Tomorrow morning, in the hours just before sunrise, look for the two brightest planets Jupiter and Venus just 1.2 degrees (2.5 Moon diameters) apart to the Southeast!

MESSAGE #5. Wed Jan 30 16:57:13 2008 . Lauren Woolsey wrote:

The news site digg.com is constantly updated, and has a whole section related to space. More diggs means a more popular story, so check it out!

MESSAGE #4. Tue Jan 29 23:54:32 2008 . William Updegraff wrote:

Here's that Powers of Ten video on youtube, in case anyone has a campiness craving:

http://www.youtube.com/watch?v=LnqXcK4YPM0

MESSAGE #3. Tue Jan 29 22:37:42 2008 . Scott Poese wrote:

Just thought I'd post a link to a picture of the Pic du Mundi observatory in France. How amazing would it be to work there? http://antwrp.gsfc.nasa.gov/apod/ap080125.html

MESSAGE #2. Tue Jan 29 13:09:33 2008 . Jason Schwankert wrote:

Interesting Book Recommendation: Death By Black Hole by Neil DeGrasse Tyson

MESSAGE #1. Thu Jan 31 10:11:31 2008 . Prof. Doug Hamilton wrote:

Welcome to ASTR121! I hope that you will find this bulletin board a useful place for discussion, for meeting classmates, and for sharing your ideas and excitement about astronomy! To get you started, post here by the end of February and receive two juicy bonus points!!*

* Offer void where prohibited by law, you must be enrolled in ASTR121 to participate, and bonus points have no cash value. Bonus points will be awarded in early March; please allow 6-8 additional days for delivery.

Return to the ASTR121 main page