One Astronomer's Noise

Entries from March 2010

Telescopes from Space!

March 31, 2010 · Leave a Comment

Soichi Noguchi, an astronaut currently living aboard the International Space Station as part of Expedition 23, loves sending back gorgeous pictures of the Earth and Moon via his Twitter feed, astro_soichi. This morning, I woke up to a lovely picture of the Atacama Desert, complete with a from-orbit view of the ALMA OSF:

Click a twitpic!

Don’t yet know your radio astronomy alphabet soup? ALMA is the Atacama Large Millimeter/Submillimeter Array, a really powerful radio interferometer that will probe the sky with much higher sensitivity in the millimeter and submillimeter wavelengths than ever before. Astronomers will be able to do groundbreaking research in star formation, planet formation, galaxy evolution, and more. Yeah, it’s a big deal. The telescope itself is being constructed at the “high site” of 16,000 ft (5000 m) called the AOS, or Array Operations Site. That’s a wee bit high for we oxygen breathing humans to work comfortably every day, so the base of operations is the OSF, or Operations Support Facility, at an altitude of “just” 9,500 ft (2900 m). The OSF is what was captured by the orbiting astronaut. Cool.

Get more of your weekly space fix at the Carnival of Space #147 at WeirdSciences!

Categories: astronomy
Tagged: , , ,

AstroJargon of the Week: HI

March 27, 2010 · 2 Comments

For this week’s (late) AstroJargon, I’d like to point out a bit of jargon I used in my Ada Lovelace post the other day. I talked all about HI (the letter “H” and the Roman numeral one) studies, and before posting, I quickly inserted “neutral hydrogen” as a definition. But why is that important anyway?

We know that the universe is mostly made of hydrogen. But unless it is creating energy by fusion in the core of a star, we can’t really see it in visible light. However, a neutral hydrogen atom floating about on its own can give off some light, though very rarely and with very low energy. The simplest hydrogen atom consists of one proton and one electron, and each particle has a property called “spin.” (They aren’t really spinning like planets, but it can be useful to think of it that way.) The spins of the particles can be aligned or anti-aligned, and each configuration is a slightly different energy. When the electron “flips” from the higher state to the lower state, a bit of energy, in the form of a photon of light, is given off. It’s a teeny, tiny bit of energy, not enough to be visible or even infrared. This light is given off in the radio regime with a wavelength of 21 centimeters, or 1.4 GHz. (The wavelengths of visible light range between 400 and 700 nanometers!)

Click to go to animation! Courtesy NRAO/AUI

When this was theorized and then discovered, it became an rich area of study for the newborn field of radio astronomy. After all, hydrogen gas is EVERYWHERE, and now we can see it! With hydrogen, we could finally peer through the dust of our own galaxy and determine its spiral shape.

From here.

We’ve been able to map the gas in spiral galaxies, further out than the stars, and make rotation curves that tell us that there’s some dark matter we don’t see.

M33 in atomic hydrogen, where colors indicate the Doppler shift, or velocity. With this information, astronomers can map out how much mass there is in the galaxy. Image courtesy NRAO/AUI

We can detect interactions between galaxies that seem fairly normal in visible light.

Visible light is on the left, radio HI is on the right, same scale. Courtesy of NRAO/AUI.

And by detecting HI from the very early universe, we will be able to observationally probe how the very first stars and galaxies were forming in the first billion years of the universe’s history! That elusive signal is called the “epoch of reionization” which I discuss a bit more in my first 365 Days of Astronomy podcast, and in an earlier post.

So, I hope you see that HI is pretty cool, and everywhere, and it’s one of the cool things that radio astronomy has to offer in a unique way!

Categories: astronomy
Tagged: ,

Radio Stars!

March 24, 2010 · Leave a Comment

My buddy and officemate George is going to be on Public Universe at Blog Talk Radio tomorrow morning at 10am EDT. The show is really fun, and they ask some great science questions, so check it out! They have a recording of my chat with them from last week as well, which was a big highlight in my otherwise sleepy sick day.

And, I know I’m late on my AstroJargon of the week… but I’m meeting with my thesis committee tomorrow, so this week’s been… overwhelming. Heee…… :-P

Categories: general
Tagged:

Nan Dieter Conklin: Two Paths to Heaven's Gate

March 24, 2010 · 6 Comments

This year, for Ada Lovelace Day, I’d like to celebrate women in technology and science by celebrating the life of another early pioneer of radio astronomy: Nan Dieter Conklin. (If you haven’t, check out last year’s post on Ruby Payne-Scott!)

A couple of years ago, I picked up Nan’s memoirs, “Two Paths to Heaven’s Gate” which was published by the National Radio Astronomy Observatory. It is a really beautiful memoir, like a conversation over tea. So many of her impressive feats are explained quite humbly, or with an almost childish glee. It is the path of her life, not a great epic tale. She shares nuggets of wisdom, inspiration, and kindness from her mentors, collaborators, and friends throughout her life. I believe that she must also be a good teacher, as her explanation of astronomical terms and processes are quite thorough and accessible and don’t detract from the flow of her story.

Her love affair with astronomy began in college. She was greatly inspired by one teacher, Dr. Helen Dodson, who inspired her to want to do her own research. Nan eventually took her astronomy knowledge to the Naval Research Lab in 1951 to get a job with their brand-new 50-ft radio telescope, just as the field of radio astronomy was finding its feet. Her “male colleagues had no hesitation in working with a young woman.” She began studying solar flares and worked on her first published paper. Her home life was not entirely peaceful as her husband was asked to leave seminary, and they had their first baby. She was lucky enough to find help to raise the little girl so she could continue her career. However, she left with her daughter on her own in 1953, while continuing to work, she says, “not only for the money, but for my sanity.” She went on to co-discover HI (neutral hydrogen) absorption along the line of sight to the center of our Galaxy. She began to long, once again, to direct her own research, which would mean returning for graduate school. Her second husband moved with her to Massachusetts where she got her PhD in astronomy at Harvard, the home of many female astronomy pioneers. And in case getting a PhD isn’t hard enough, she finished her HI studies while being barred from the main observatory due to a false accusation of a fellow student, and she defended her thesis while five months pregnant in 1958. But finally, she could do her own astronomical research.

She went on to continue her contributions to radio astronomy in mapping hydrogen disks in nearby galaxies. She also published a paper on a model of our own Galaxy based on HI observations, but a fundamental error (missed by reviewers) led her to leave modeling to the theorists and stick to observational astronomy. In 1961, after dealing with some troubling medical symptoms, she was diagnosed with multiple sclerosis. She decided to learn as little about the disease as possible and take her own symptoms as they came, since they can vary so much from patient to patient. As her second marriage deteriorated, she found a new life with her girls in Berkeley at the Radio Astronomy Laboratory. A 39-year-old single mother with a 13-year-old and a 6-year-old, she continued to blaze a trail in the radio skies. She and her colleagues probed the Galaxy with observations of the OH molecule, including highly variable OH masers in the star-forming Orion Nebula, with the 85-foot telescope at Hat Creek. She mapped high-velocity HI clouds in the Galaxy with 2500 hours of observing time and, seriously, data printed out on punch cards to be fed to the University’s computer! She later searched for formaldehyde in dark interstellar clouds as the Vietnam war protests of the 1970s raged around Berkeley. She also helped pioneer the technique of very long baseline interferometry, linking together the Hat Creek 85-foot antenna with the 130-foot dish at Owens Valley, 300 miles away.

Images courtesy N. Dieter-Conklin/NRAO/AUI

In 1968, she married Garret Conklin who was to be the love of her life until his death in 2002. With him she shared sailing, fabulous food, their summer house in the mountains, an apartment in Paris, and trip to the USSR. I found this part of the book particularly fascinating as Nan describes her experiences navigating a foreign and, for so many Americans, closed off country during the Cold War. The three month visit was made possible due to her status as a scientist as the trip’s primary purpose was to find out what Soviet researchers had discovered about the interstellar medium for a review article. Her recollections, interspersed with entries from her husband’s travel diary, tell a story of a trip that she describes as “profound,” and my attempt at a summary could never do it justice.

In 1977, Nan retired from astronomy at the age of 51, and set about living first on the Mediterranean island of Menorca for a short while, then Vermont for 17 years. Nan worked on pottery for as long as her MS would let her, then switched to painting. She dealt with chronic pain for a number of years until she beat it with the help of some wonderful visiting nurses, but she still lost the ability to walk. They moved to Seattle to be near Nan’s daughter when Garret’s Alzheimer’s became a strain, and they both moved into an assisted living facility where Nan met the writing group that eventually persuaded her to write the book. After Garret’s death, she moved to a retirement community where her memoirs end in 2005. Her work, however, extends beyond that, as I quickly found a short paper by her in the Astronomical Journal, dated April 2009, on high-resolution observations of interstellar clouds in absorption! (Unfortunately, behind a paywall. Sorry!)

She considered herself, and felt she was always treated like, “an astronomer who happened to be a woman.” However, no one should underestimate the strength and intelligence it took for her to take this journey. I highly recommend her memoirs as the story of a solid researcher and a fascinating woman who happily traveled her parallel paths of the personal and the professional.

I’ll leave with some really poignant observations on a career in astronomy from the conclusion of “Nan Dieter Conklin: A Life in Science,” the precursor to the book:

It is vital, of course, that you carry out the project with absolute integrity, and without emotion, although in order to invest the effort in the first place you need to believe that the project is worth doing. An astronomer, or any scientist, fights a daily battle between emotion and discipline, and the job cannot be done without both.

On the other hand, I have found in astronomy a career always satisfying and occasionally thrilling. One persists through times of routine, demanding hours with the possibility of an extraordinary reward. Make no mistake; the approval of colleagues, especially those not familiar with your work, is wonderful, but it does not hold a candle to the joy in realizing that you are seeing something for the first time. In my experience there are two ways in which real discoveries are made: stumbling on something totally unexpected while looking at something else, and searching for something because you think it might be there. In my own work I found one of each.

Nan, I’ve never met you, but in case you stumble upon this posting, I’d like to tell you that you are an inspiration to me.

Categories: astronomy · science
Tagged: ,

Spacey Carnival and the Ladies of Science

March 23, 2010 · Leave a Comment

This week’s carnival, number 146, is hosted by Simostronomy! I was particularly entertained by the submission from Alice’s AstroInfo, where she compares her own planetarium repair experiences to the last Hubble servicing mission. At the time of the STS-125 mission, I was in Green Bank climbing around on our antenna groundscreens again, doing repair work, remarking that my job was easier than the astronauts’ jobs in many ways, but at least they didn’t have to worry about finding a wasp nest inside Hubble. I found two on PAPER that day.

Tomorrow is a special blogging event… Ada Lovelace Day! I’m looking forward to reading all kinds of stories of trailblazing ladies in science and technology. My own post will go up tonight! It’s not too late to pledge if you want to write about a woman that has inspired you.

Also debuting tomorrow is a project by the lovely Heidi Anderson, SheThought.com. This is going to be a great place to discuss women, skepticism, and science. See you there!

Categories: astronomy · science
Tagged: , ,

My Very First Teaching Gig!

March 17, 2010 · 3 Comments

Okay, I am pretty darn excited. I get to teach my very first class ever this summer! Grad students don’t normally teach astronomy classes at the University of Virginia except during the summer semesters. The classes are a little over two hours a day, five days a week! The topic? Life Beyond Earth. *SQUEE!* Professors in our department have typically used material from Life in the Universe by Jeff Bennett and Seth Shostak. I already love Bennett’s intro astronomy book, so I’m sure I’ll do the same. Now the problem will be not spending all of the next few months excitedly preparing lectures, notes, activities, and assignments when I should be doing research.

Need I say… if you are at UVa and need another science class, come on over! It’ll be awesome.

Categories: astronomy
Tagged:

AstroJargon of the Week: Parsec

March 15, 2010 · 9 Comments

This week I thought I’d scale back from such a rich topic as AGN and tell you a little bit about the parsec. (In this case, I do not mean the podcast awards!)

A parsec is a measure of distance. But, you are thinking, Nicole, don’t you astronomers already use the light year as a measure of distance? A light year is the distance that light travels in one year, so it is a convenient measure of distance to explain. (It’s about 5,878,630,000,000 miles, if you are curious.) However, astronomers actually use a unit of distance that makes more physical sense with respect to how we measure distances.

The name “parsec” is pretty self-explanatory once you know what two jargon-y words it’s made of. It is defined as the distance that an object is from Earth to create a parallax of one arcsecond.

Hold out your finger at arms length. No, really, do it. I’ll wait. I won’t laugh! Promise. Okay, now close one eye and note what your finger is in front of. Now, open that and close the other. Notice a difference? Compared to some background object, your finger has appeared to move, no matter how still you keep it. That is essentially parallax.

Now, take this system on a grander scale. Each one of your eyes was a point of view. Replace that with the orbit of the Earth, with one point of view 180 degrees around the orbit from the other. Your finger is now some star to which you would like to know the distance. The background of your room is the background of more distant stars and galaxies. A parallax observer takes pictures of their target star six months apart and measures the change in position against the background of stars that are too distant to show this effect. From that measurement, they can tell the distance thanks to a little geometry.

This picture is very much NOT to scale since the distance to any star is much, much greater than the size of the Earth’s orbit. So, we can use some handy approximations to calculate the distance. See that right triangle? We can pull out from our trigonometry background that

tan(p) = (distance from Earth to Sun) / (distance from Sun to star).

But with the “small angle approximation” and using the definition of the distance from the Earth to the Sun (Astronomical Unit, AU, approximately 93 million miles), we get

p = 1 AU / d

Using just the right units, and doing a little switching around, we get just

d = 1 / p

The unit of measure for p is arcseconds, which is a tiny, tiny angle. If you break a circle into 360 wedges, each one is one degree. If you break that wedge into 60 wedges, each is an arcminute. Split up one of those 60 ways, and you get an arcsecond. Another way to see how tiny that is…. hold up your index finger at arms length again. The width of your finger is about 1 degree. So an arcsecond is 1/3600 the width of your finger. Need I say… TINY! A star that measures a parallax of one arcsecond is now one parsec away.

So how far is a parsec really? If a one-arcsecond measurement is so tiny, then a distance of one parsec must be really far away. And it is, on human scales, but the nearest star is 1.3 parsecs away. The center of our Milky Way galaxy is almost 8000 parsecs away, or 8 kiloparsecs*. Cygnus A, one of my favorite radio galaxies, is 230 million parsecs (or 230 megaparsecs) away. Yeah, this stuff is FAR!

How do parsecs compare to the more-easily-explained light year? Well, one parsec is approximately 3.26 light years. If you ask me the distance to some celestial object, if I know it at all, I probably know it in parsecs, and will make a quick and dirty calculation in my head to light years before answering. And like its cousin the light year, the parsec has been mistaken for a measure of time.

Now, before you go off on your own parsec-scale adventure, check out the newest Carnival of Space #145 at Crowlspace.


Have an astrophysics jargon suggestion? Email me, and I’ll try and include it!

*Edit: I should be a little more careful with my significant figures. We don’t know the distance all that accurately! Thanks @leifb :-)

Categories: astronomy
Tagged: , ,

And the winner is… SPACE!

March 10, 2010 · Leave a Comment

The ever-fabulous Ian O’Neill hosts this week’s Carnival of Space #144. There are lots of great astronomical highlights from this week, but I’m particularly in love with this gorgeous multi-wavelength image of NGC 1068:

via Chandra, Hubble, and the Very Large Array

Check it all out at Discovery News this week!

Categories: astronomy
Tagged: , ,

What's the message?

March 9, 2010 · Leave a Comment

This past weekend, I batted my eyelashes at Tim to go to the Hayden Planetarium with me once I discovered it was a few blocks away from a wedding we were attending. We took all of Saturday afternoon to catch the latest planetarium show and browse the rest of the American Museum of Natural History. He had never been there, and I gravitated towards my favorite parts of the museum. We wandered around the Rose Center (mostly the Space part) and I rambled on and on about subsections of the exhibits, pointing out where our friends’ research projects lie, and that nice blank part of the universe’s timeline where the epoch of reionization and dark ages research will help fill in. Then, we went straight for the dinosaurs on the fourth floor, because, who doesn’t love dinos?! We wandered around the fossils, dodging kiddies and their overzealous picture-taking parents. There’s only so much of the mass of information that one can hope to absorb in any one visit, and I’m just trying to keep my sauropods and theropods and ornithischians straight. However, I did notice a subtle theme in many of the exhibit commentary. Here’s an example (check out the yellow box in particular):

Click for dinosaurian biggness!

Maybe I’m just paranoid (especially since Tim didn’t pick up on this until I pointed it out) but there were a number of displays asserting that the science doesn’t tell us the truth, or we’ll never know the answers, because the fossil evidence in incomplete or because the animals are not here to study directly. Although it’s a fair point to say that science doesn’t prove any theory beyond a shadow of a doubt, and that extracting answers from the tiny bits of fossils we do find is excruciating, tedious, and not exact, it was an odd point to be hammering home in a science display. After all, I personally marvel at what knowledge we can glean from incomplete evidence and at the self-correcting nature of science. That’s the kind of message I would send, especially in this era of mistrust and misunderstanding of science by so many people.

So, after we got our fill of dino fossils and expensive but admittedly delicious museum food, we headed to one of my other favorite areas, the Hall of Human Origins. I love to wonder what life was like for early hominids, including for those of our own species who were physically identical, but living in a totally different world 150,000 years ago. I marvel at the tenacity of Homo erectus who populated the Earth for 1.5 million years, whereas we’ve been here for a fraction of that. Anyway, as I was browsing, I noticed that the displays read differently than in the fossil halls:

Click for large version.

It asks a question, states that we don’t yet know, but that it is an area of active research. It puts forth a guess based on the best of our knowledge and leaves the reader wondering what we’ll find out next. This, I think, is far more exciting and educational and doesn’t do the whole process of science a disservice.

This was the first time that I looked beyond the information in an exhibit to the style of the presentation. It is important to know who your audience is and what message you want to send whenever doing science outreach or teaching. Students and museum patrons are probably not going to retain much specific information. Good teachers are aware of this and try to get across a general message about science and have to be cognizant of what that message is. It’s not easy to do this, but having a goal is a good start. You can tell that the designers of the different exhibits have different goals, or at least different opinions on what it is about science they want to convey. For what it’s worth, I think the latter example is going to be much more helpful in conveying the true nature of science to those who don’t live it everyday. And after all, isn’t that important? Isn’t that kind of transparency and understanding just what science needs?

Categories: education · outreach · science
Tagged:

AstroJargon of the Week – AGN

March 7, 2010 · 4 Comments

Jeffrey Bennett, astronomer and author, once told us that a typical astronomy textbook has about as many vocabulary words as a typical foreign language textbook. So, in addition to teaching physical and astronomical concepts, we’re teaching a whole new language! Jargon is incredibly useful for making detailed communication within a specific field efficient and convenient, but you have to be aware of it when teaching students or talking with people outside your sub-field. So, I’m going to attempt a weekly series of astrophysics jargon, inspired by the Geology Word of the Week on Skepchick. I’ll try to demystify some terms that you may hear astronomers bandying about!


This week’s jargon is one of my favorites, and it’s one that gets the most quizzical looks when it slips out in a tutoring session. AGN stands for Active Galactic Nucleus (or Nuclei). It is literally when the nucleus, or center, of a galaxy, or vast collection of stars, is active, or really, really bright.

Compare the galaxy with the AGN, or the “active galaxy” on the left with a similar galaxy on the right which is not active. From William Keel, University of Alabama Department of Astronomy & Physics.

There is a whole zoo of subclassifications within the grouping of AGN, mainly due to the various methods by which these galaxies were discovered. However, the basic principle lies with the giant that is at the heart of every major galaxy, a black hole that is millions (or billions) of times the mass of the sun! One of the fascinating results to come from the Hubble Space Telescope is that, everywhere we look, every galaxy (with an appreciable central bulge) has a black hole in its center.

Not only that, but the larger the bulge of stars, the larger the black hole! But that’s a story for another day. From hubblesite.org.

Although we don’t yet know where these super-massive black holes first came from, we do know that they can get bigger if mass falls onto them and becomes part of the black hole. Turns out, this is a really, REALLY energetic process. Black holes have a lot of mass packed into a (relatively) tiny space, so any gas that gets close enough to fall in doesn’t do so right away, but settles into a disk around the black hole to spin around a bunch of times before finally crossing the “point of no return.” The material in the disk gives off a LOT of energy, thus powering the active galactic nucleus.

Artist’s conception of a black hole, disk, and jet. M. Weiss, Chandra X-Ray Observatory

How much energy? A moderate AGN gives off approximately 20 times the light output of a galaxy like the Milky Way! And the light is spread out over all wavelengths, from x-ray and ultraviolet through visible and infrared, and even some in the radio. Because they are so bright, they are powerful probes of the universe at large distances. They may also be intimately involved in the life history of a galaxy, as this bright light from the galaxy’s center has an impact on the environment around it. Also, powerful jets of particles moving at almost the speed of light may be generated near the black hole and affect the galaxy and the galaxy’s environment in a violent way.

One of my favorite radio sources, 3C84 (pink) has jets that have carved out a hole in the x-ray gas (blue) in the Perseus Galaxy Cluster. (Chandra image by A. Fabian, VLA image by G. Taylor)

There are so many cool and interesting subclasses of AGN, and so many structures within and related to the AGN, that it’ll probably take a whole sub-series itself! But I hope this introduction gives a clearer picture of what astronomers means when they say, “That’s my favorite AGN!”


Have an astrophysics jargon suggestion? Email me, and I’ll try and include it!

Categories: astronomy · science
Tagged: , ,