Astronomy.com blog : Daniel Pendick

August 2009 web extras for magazine subscribers

Karri Ferron — Tue, 23 Jun 2009 21:30:00 GMT

Now that the August 2009 issue of Astronomy is in the mail or already in hand, we’ve updated Astronomy.com with our newest web extras to give subscribers exclusive complementary information to this special issue about our return to the Moon.

Take a sneak peek inside the August 2009 Astronomy magazine.

If you subscribe to Astronomy, make sure you’re registered with Astronomy.com so you can access these great extras.

Here are this issue's highlights:

Senior Editor Richard Talcott shares a NASA video animation preview of the Constellation program that will put humans back on lunar soil in “Return to the Moon.”

Associate Editor Daniel Pendick explores the opinions on NASA’s concept of “Moon first, then Mars” in “Should we go to the Moon first?”

Pendick also explains the uncertain effects of long-term exposure to space radiation and low gravity in “What are the health risks of a Mars mission?”

Senior Editor Michael E. Bakich offers an in-depth preview of the LRO and LCROSS missions that jointly launched June 18 in “NASA's next Moon mission.”

Pendick answers the “Ask Astro” question: “How warm does it get on Mars?”

And I’ve included a few more Q&As with Frank Shu and Joan Najita in “Astro Confidential: Extending the conversations.”

Of course, we’ve also posted “Bob Berman’s Strange Universe,” “Glenn Chaple’s Observing Basics,” “Stephen James O’Meara’s Secret Sky,” and “David Levy’s Evening Stars.” There are also August’s “The Sky this Month” and five “Ask Astro” questions.

Related:

Astronomy.com's Lunar Reconnaissance Orbiter mission page

LRO scientist Michael Wyatt blogs for Astronomy

Daniel Pendick — Tue, 16 Jun 2009 19:39:00 GMT

If all goes as planned, the Lunar Reconnaissance Orbiter (LRO) will launch from Cape Canaveral either Thursday or Friday, depending on the launch of space shuttle Endeavour. Brown University professor and LRO researcher Michael Wyatt is at the launch site, and starting today, Wyatt will share his impressions of this historic mission — the opening maneuver in the United States return to the Moon — with all of you. Thanks, Michael!

We'll post Michael's updates to this article in our news section, "Exclusive: Lunar Reconnaissance Orbiter updates from mission scientist."

Your Mars questions, Dr. C answers

Daniel Pendick — Fri, 05 Jun 2009 15:33:00 GMT

The Jet Propulsion Laboratory’s Mars Exploration Program web site has a fun new feature — Ask Dr. C, “your personal Mars expert.” You can type in a simple question — the simpler, the better — and get a pretty good answer. A computer program tries to match your question with an extensive database of responses.

The real Dr. C is Phil Christensen, a planetary scientist at Arizona State University. Christensen is the Principal Investigator for the 2001 Mars Odyssey Thermal Emission Imaging System (THEMIS) instrument, and the Thermal Emission System instrument on Mars Global Surveyor.

I decided to put the virtual Dr. C through a few paces. Here’s the result.

Dr. C: Hello ... it is a great day to learn about Mars! Please feel free to ask me any questions you would like about Mars ... or even about myself.

Pendick: Does NASA really have enough money to replace the shuttle by 2014, or should we just rename the Russian space program "NASA Moscow"?

Dr. C: I am sorry, I am not sure what you are asking. You might want to try rephrasing your question, searching for it on the Internet, or visiting http://mars.jpl.nasa.gov.

Pendick: OK, fine. I’ll stick to Mars questions then. Anti-global-warming bloggers say that because the martian south pole is currently in a warming trend, this means rising global temperatures on Earth are also "natural" and not manmade. Is it just me, Dr. C, or is that the stupidest thing you ever heard?

Dr. C: I am sorry, I am not sure what you are asking. You might want to try rephrasing your question, searching for it on the Internet, or visiting http://mars.jpl.nasa.gov.

Pendick: OK! OK! I’ll throw you a bone. Here’s an easy one. Why is Mars red?

Dr. C: Mars looks red due to a combination of the fact that its surface is comprised of iron-rich minerals that essentially rust (or oxidize) and that the dust made of these minerals is kicked up into the atmosphere, giving the atmosphere a reddish hue. The Martian surface is not all rust-colored, however, because depending on the oxidation process, the minerals can be a range of colors from butterscotch to rust.

Pendick: Nice answer! So, what is the warmest it ever gets on Mars?

Dr. C: Did you mean to ask "What is it like on Mars?" or "What is Mars?"?

Pendick: No, I am asking you how warm it gets on Mars.

Dr. C: If you were asking: How warm is Mars?, the answer is: Sometimes people think Mars is hot because it is red but, due to its distance from the sun, Mars is actually very cold (its average temperature is minus 81 degrees Fahrenheit!). However, the temperature on Mars may reach a high of about 70 degrees Fahrenheit (20 degrees Celsius) at noon, at the equator in the summer.

Pendick: Just one more question for now. Do you know of an aerospace stock that will rise, say, 40 percent over the next 6 months? I need to buy a new telescope.

Dr. C: I am sorry, I am not sure what you are asking. You might want to try rephrasing your question, searching for it on the Internet, or visiting http://mars.jpl.nasa.gov.

Sorting through the wreckage in the Andromeda Galaxy, an in-depth interview with an Andromeda expert

Daniel Pendick — Fri, 29 May 2009 16:16:00 GMT

Thanks to painstaking observations and computer modeling, astronomers have discovered that the Milky Way Galaxy is littered with the debris of stellar cannibalism. Small galaxies unlucky enough to be captured by our powerful gravity get torn to shreds and consumed.

It’s sometimes hard to sort out our galaxy’s complex history because we are buried in the midst of it — an astronomical “can’t see the forest through the trees” dilemma. So astronomers have turned to our closest neighbor in the Local Group of galaxies, Andromeda (M31), for a different perspective.

Recently I was updating a feature story about galactic cannibalism by Astronomy Contributing Editor Ray Jayawardhana, “How the Milky Way devours its neighbors.” It appears in our new collector’s edition, The Milky Way Inside and Out on newsstands June 16.

Go inside The Milky Way Inside and Out.

In the course of making sure the research in the article was as current as possible, I had the good fortune of corresponding with Puragra (Raja) Guhathakurta of the University of California, Santa Cruz. He generously brought me up to speed on research in the past decade on Andromeda’s violent history.

Studies suggest that Andromeda has consumed a dwarf galaxy within the past 1 to 2 billion years, possibly a disk-shaped galaxy. Astronomers have found a trail of stars, called the Giant Southern Stream (GSS), falling toward Andromeda’s massive center from behind the galaxy.

In a series of published studies since 2006, Guhathakurta and his students and collaborators have connected the GSS to several other features, called “shelves,” within Andromeda’s disk of stars and gas. They believe the GSS and the shelves mark a continuous trail left behind by the doomed dwarf. Read onward for more details:

PENDICK: When and how did you get interested in the history of the Andromeda Galaxy?

GUHATHAKURTA: I first got interested in the Andromeda Galaxy in the early 1990s. My longtime friend and fellow astronomer Somak Raychaudhury got me hooked. At the time, he was finishing up his Ph.D. on the Local Group at the Institute of Astronomy (IAS) in Cambridge, and I was a postdoc at the Institute for Advanced Studies (IAS) in Princeton, fresh out of graduate school at Princeton University.

Our initial interest in Andromeda involved using it as a tool to pin down the distance scale in the universe and thereby measure the Hubble constant, which in turn relates to the expansion rate of the universe.

Andy Gould, my fellow postdoc at the IAS, got me interested in using Andromeda as a test bed to study the formation and evolution of large galaxies like our own. I continued to get more and more interested in this latter aspect of Andromeda — the history of its formation and evolution — after I moved to UC-Santa Cruz as an assistant professor. Two of my early students, David Reitzel and Phil Choi, carried out their Ph.D. thesis research on this general topic.

PENDICK: Now let's talk a little about the Giant Southern Stream (GSS). Rodrigo Ibata and his collaborators discovered this apparent flow of stars into the Andromeda Galaxy. At the time no one knew for sure what it was, right? What possibilities were you and other researchers thinking about at that time?

GUHATHAKURTA: When Ibata’s group published their first star-count map of Andromeda in 2001, their survey had covered only a relatively small region on the southeastern side of the galaxy. The most prominent feature of their map was a concentration of stars forming a linear streak protruding from the inner parts of the galaxy — the Giant Southern Stream (GSS).

The authors naturally concluded that this stream consisted of the remains of a dwarf galaxy, destroyed by the gravitational (tidal) forces of the Andromeda Galaxy. It was unclear whether the progenitor dwarf galaxy had been completely disrupted or if the central core of the progenitor was still intact.

Around that time, Phil Choi, my Ph.D. student at UCSC, was finishing up a paper on the structure of the nearby Andromeda satellites M32 and NGC 205 showing clear signs of tidal distortion in their outer parts. We added to speculation by Ibata and his colleagues that the GSS may consist of stars ripped out of M32 or NGC 205. There was no hard evidence to support such an association — and such evidence has never been found.

PENDICK: OK, so now we are at the point (in 2001) where people had discovered the Giant Southern Stream but weren’t sure what it is. What have scientists discovered since then?

GUHATHAKURTA: When Ibata and his collaborators reported the discovery of the GSS, they realized what it was. It was pretty obvious that the GSS represented material from a tidally disrupted dwarf satellite galaxy. What wasn't clear yet was which dwarf satellite galaxy. That still isn't clear today.

The following year (2002), our group and Ibata’s started obtaining spectra of individual stars in the GSS to determine their motions. Both groups reported that the stars in the GSS were moving toward us at a higher speed than the speed at which the center of Andromeda was moving toward us. Around that time, Alan McConnachie reported that the GSS was farther away from us than the center of Andromeda. That is, the GSS was behind Andromeda.

PENDICK: What did that mean?

GUHATHAKURTA: The implication of the speed measurements was that the GSS was falling into Andromeda from the back/far side.

PENDICK: And people started to find other features — other debris from the dwarf captured and disrupted by Andromeda.

GUHATHAKURTA: In 2002, Annette Ferguson, Ibata, and other collaborators published a paper showing other concentrations of stars within Andromeda, including the Northeast Shelf. A couple of years later, our group pointed out the existence of the Western Shelf in the map Ferguson and the others made. In the same paper, we presented a computer model in which the GSS was connected to the Northeast and Western shelves as a continuous stream.

The model also predicted that there should be a Southeast shelf present as well. A few months later, we found a definite pattern in our set of stellar velocities indicating the presence of the Southeast shelf. The pattern we saw in our data set was exactly the pattern predicted by our computer model.

PENDICK: What’s left to do to understand these features like the GSS? What are you and your students up to right now?

GUHATHAKURTA: For the GSS itself, it is important to carry out a detailed, statistically robust, forensic reconstruction of this cosmic collision. Such an exercise can tell us what the dwarf galaxy progenitor of the GSS looked like BEFORE it got tidally shredded by Andromeda — i.e. a glimpse into its history. For example, did the dwarf galaxy progenitor consist of a rotating disk of stars? Did it contain gas in the form of neutral hydrogen, and could that explain some of the gas astronomers have recently seen in the vicinity of the GSS?

More generally, it is important to understand how unique such forensic reconstructions are. How precisely can one pin down the orbit and internal properties of the progenitor? This question can be applied to the GSS but should also be applied to debris from other merger events in Andromeda. Astronomers have long known about similar features in other galaxies, and these are starting to get studied in detail.

My students and I are actively studying the many different stages of the hierarchical process through which a large galaxy like Andromeda or the Milky Way is built up from smaller systems of stars (dwarf galaxies). In the context of galactic cannibalism, we are studying the digested material that forms the large belly of Andromeda the cannibal (its smooth stellar halo), the relation of this belly to the cannibal's other internal organs (disk, bulge/inner spheroid), partially digested entrails (GSS and other tidal streams), and the survivors (present day intact dwarf satellite galaxies).

Related content:
See more images of the Andromeda Galaxy (M31) in our Online Reader Gallery.

Updated: Historical telescopes at the Adler Planetarium

Daniel Pendick — Thu, 21 May 2009 19:20:00 GMT

***Images updated.***

Next week, you can check out the rich collection of astronomical instruments at the Adler Planetarium in Chicago. In celebration of the 400th anniversary of the telescope, the planetarium opens its a new exhibition, “Telescopes: Through the Looking Glass,” on May 22. The show spotlights technology used to gather information about our universe since Galileo’s day and includes hands-on interactive exhibits.

The trumpet-shaped telescope is a rare type with few surviving examples. Its distinctive feature is a front end that flares outward to the instrument’s objective lens. The Adler show will take you from the 1600s, when this beauty was made in Italy, to the reign of the Hubble Space Telescope, now being refurbished in orbit by a space shuttle crew.

Dating from around 1630, this beautiful Italian refracting telescope is the only early telescope found outside of Europe. Part of the Adler's world-famous Mensing Collection, this rare trumpet-shaped telescope's main tube tapers outward from the eyepiece. ©Adler Planetarium]

This 1977 pocket telescope, created by noted English craftsman Peter Dollond, is encased in tortoise shell inlaid with silver. The tubes are made of pasteboard with an interior surface that's matte black to reduce stray reflections. Red leather tooled in platinum covers the single draw, with the overall design based on leafy vines. ©Adler Planetarium

Owning a Dollond telescope carried a great deal of social weight. This elaborately decorated piece from 1843 is made of gold-plated sterling silver. The main tube shows raised scrollwork and foliate decoration, its case red Moroccan leather with elaborate gold tooling. A Turkish noble likely commissioned it. ©Adler Planetarium

William Herschel, a German musician turned astronomer, discovered Uranus in 1781 using a reflector identical to this 7-foot instrument made in 1788. Herschel's passion for astronomy led him to build the most powerful telescopes in the world. He also invented a mount that allowed the eyepiece to stay at the same level while the tube and mirror moved to locate celestial objects. ©Adler Planetarium

SETI's "Earth Speaks" lets you suggest a message to alien civilizations

Daniel Pendick — Tue, 19 May 2009 21:07:00 GMT

On May 15, the SETI Institute — the planet’s leading extraterrestrial searchers — launched “Earth Speaks.” The project invites the public to submit proposed messages to alien civilizations. According to Thomas Pierson, CEO of the SETI Institute in Mountain View, California, “By submitting text messages, pictures, and sounds from across the globe, people from all walks of life will contribute to a dialogue about what humanity might say to intelligent beings on other worlds.”

For a half-century, scientists have scanned the skies for radio messages from intelligent life. So far, not so good — no “You’ve got mail” window has popped up on SETI laptops.

But if we did get the call, what would we say in reply? Think it over carefully.

“The initial messages we send to an extraterrestrial civilization could set the tone for a conversation lasting hundreds or thousands of years,” says Douglas Vakoch, Director of Interstellar Message Composition at the SETI Institute. Man, wouldn’t you like to have a business card with THAT job description on it!

I think one useful message could be, “We taste bad. Tough to chew. Stay away.” You know, like in that old science-fiction plot about aliens coming to Earth to turn us into a 6-billion-member herd of cows.

Or how about, “Does God exist? If so, please forward a contact number.”

Or “LOL/2BZ4UQT” (Laughing Out Loud/Too Busy For You Cutey)

Or maybe, “Sorry, currently perturbing climate on a global scale and using up all energy resources. Will try to respond next week. If you have a working design for a fusion reactor or a perpetual motion machine, please forward.”

If you have something to say to the aliens, submit your messages, sound, or image to Earth Speaks.

More SETI news from Astronomy.com:

The biggest model rocket in history

Daniel Pendick — Thu, 07 May 2009 21:15:00 GMT

On April 25, Steve Eves of Ohio launched the largest model rocket in history: a 1,700-pound, 36-foot-high replica of the legendary Saturn V booster that took the first astronauts to the Moon. It rose to about 4,400 feet, deployed chutes, and settled to the ground — upright.

Check out this YouTube video. Listen to that thing roar!

Model rocketeer and Fresno, California, lawyer Mark Canepa provided the photos. Check out his
outstanding pre-launch profile of the project in Rockets magazine, “One man's quest to honor America's Saturn V rocket.”

Here’s Canepa’s take on the amazingness of Steve Eves’ successful launch in a Maryland farm field:

“Steve Eves not only built the world's largest flying model rocket, but he also allowed thousands of people to share in the recreation of one of the greatest events in history, the launch of Apollo 11. To see his rocket lit up by floodlights on the pad, the night before the launch, was incredible. All morning on Saturday, people of all ages walked a quarter of a mile from the parking and spectator area just to see the rocket up close, and to touch this replica of the Saturn V. For a moment, you felt like a child again, that this was Cape Kennedy in 1969, and anything was possible.”

Writing about this event has brought back some memories for me, too. I was born in 1963, when the Saturn V hadn’t left the pad yet. I’d love to tell you John F. Kennedy’s stirring speeches sent me on some inevitable path leading to my desk at Astronomy magazine. But I never heard the speeches — I wasn’t born yet — and I have no specific memory of seeing astronauts cavorting on the lunar surface.

In truth, it was Estes — not Apollo — that fired my boyhood imagination. Estes made model rocket kits, a product for which I had an insatiable hunger. Just flipping through the catalog was a thrill.

Other aerospace initiatives followed into my teenage years. One was building a glider with a 4-foot wingspan using individually fabricated teardrop-shaped spars covered with doped wing paper. After its last and longest flight, my stepfather accidentally ran it over with his Ford Econoline van. Oh, the humanity!

All photos courtesy Mark Canepa

All the pretty mergers

Daniel Pendick — Thu, 30 Apr 2009 14:27:00 GMT

Here is what the future of computer-simulated galaxy mergers may look like. This image to the right — unusual for its vivid color and detail — shows five stages of a collision between two virtual galaxies, cooked up by computer programs that simulate the processes at work.

View a bigger version of this image.

The image is part of an ongoing project to visualize simulated mergers in a more realistic manner — to produce something more like what you would see through a telescope. T.J. Cox, an astrophysicist at the Harvard Center for Astrophysics, is a member of the team. He kindly provided this work in progress.

Computer models, Cox explains, track the mass and velocity of stars in response to the gravitational disruptions unleashed by close encounters of the galactic kind. But when the Hubble Space Telescope and other observatories view mergers, they see the light emitted by billions of individual stars across a range of wavelengths.

The simplest merger visualizations look like churning swarms of little white “particles” standing in for concentrations of mass (stars) as they interact gravitationally. These visualizations are, as they say, “nothing to look at.”

To get truly realistic mergers, computer models need to include more than just mass particles tugging on each other. The simulations also need to include the effects of gas heating and cooling, star formation, supernova explosions, and absorption of light by interstellar dust.

Cox says that realistic visualizations will make it easier for astronomers to compare theoretical mergers with observations of actual mergers. It would provide modelers and observers a new way to compare notes. And that would make it easier for the theoreticians and observers to interact — much like the colliding galaxies they study. “In a sense,” Cox says, “this enables a feedback loop where the models and observations work in concert to clarify the underlying astrophysics for galaxy formation.”

Check out this realistic-looking animation of a galaxy merger by Patrik Jonsson, another scientist working on the project.

Related:

Low-mass extrasolar planets aplenty

Daniel Pendick — Wed, 22 Apr 2009 21:14:00 GMT

Tuesday at the European Week of Astronomy and Space Science meeting in Hatfield, England, astronomers announced a new milestone: an extrasolar planet with the lowest confirmed mass of any yet discovered around a normal star.

“Confirmed” . . . “normal star” . . . seems like a lot of caveats, doesn’t it? Let me explain.

The planet is called Gliese 581 e, and the research says it contains 1.9 times Earth’s mass. Earth-mass planets are the holy grails of extrasolar studies right now. That’s because planets about the size and (rocky) composition of Earth — assuming the right surface conditions and the presence of liquid water — could potentially give rise to life in a form that would be familiar to us. You know, biological bug-eyed monster-type thingies. Or at least a brightly colored slime mold or bacterial colony.

The caveats gum up the works a bit, but they are essential. For instance, it’s important to include “confirmed,” because there is an unconfirmed contender for the lightweight-earthlike-exoplanet crown: MOA-2007-BLG-192-L b.

This little guy might be a mere 1.4 Earth masses, but that depends on certain assumptions being correct — like estimates of how big the planet’s parent star is. The mass of the star could affect the calculated mass of MOA-2007-BLG-192-L b.

And it’s also important to say “normal star” because smaller and lighter planets exist around decidedly abnormal stars called pulsars. A pulsar is the superdense core of an aged star that spins rapidly, causing energy radiating from hotspots on the star to appear to pulsate as seen from a distance, as if you were watching a faraway lighthouse. One known pulsar, called PSR B1620-26, hosts a planet significantly LESS massive than Earth.

The downside for science writers is that when reporting biggest/smallest/fastest scientific discoveries, those caveats sure get in the way of a snappy headline. But in science, the caveats are everything. Scientists are obsessively precise about their claims. They have to be. It’s what we pay them to do – to be careful.

We struggle every day with how to handle those caveats. We want to describe discoveries in the most simple, direct, and clear way possible. But to be accurate, we have to find ways to sneak in the important caveats without tripping up the reader. It’s hard to do, but never impossible.

My first editor — um, let me qualify that: my first editor at a paying professional science-writing job — assured me that the English language is powerful and flexible enough to solve any problem. You just have to work hard to find that perfect turn of phase, that vivid verb, or that ideal sentence structure that does the job.

But I wonder if she ever had to write about low-mass exoplanets.

AT LAST! The next-next big thing in space telescopes?

Daniel Pendick — Thu, 16 Apr 2009 16:39:00 GMT

Astronomers eagerly anticipate the final Hubble Space Telescope (HST) servicing mission, set to blast off May 12 from NASA's Kennedy Space Center in Florida. And they are already hard at work designing the observatory that will take over after Hubble sees its final light.

Hubble is, in the lingo of telescope engineering, a UVOIR instrument: Its 2.4-meter light-collecting mirror samples wavelengths of light in the ultraviolet (UV), optical (O), and near-infrared (IR).

The James Webb Space Telescope, slated for launch in 2013, will have a much larger light-collecting mirror — 6.5 meters — than Hubble. But it will operate in the infrared.

No one knows how long HST will continue to function after the final servicing mission. It’s been in space since 1990 — 19 years and counting.

HST’s presumptive successor is ATLAST: the Advanced Technology Large-Aperture Space Telescope. I came across a detailed report on the telescope, authored by a large group of scientists and engineers from companies and scientific institutions — including Marc Postman of the Space Telescope Science Institute.

The Postman report is part of Astro2010, the ongoing “decadal survey” in astronomy and astrophysics. Every 10 years, the National Research Council of The National Academy of Sciences undertakes the surveys to recommend scientific priorities for the coming decade. ATLAST is just one idea vying for support.

ATLAST’s primary mirror would be 8 to 16 meters wide. The 8-meter concept (pictured above) assumes a solid mirror, like that of HST. The 16-meter version would have to be an unfolding assembly of segmented mirrors, like the one on the James Webb Space Telescope. Postman’s group projects the telescope could be ready for launch by 2025. Technology development, design, and planning would cost hundreds of millions of dollars.

For one thing, ATLAST would have the ability to actually detect oxygen, ozone, water, and other possible life signs (“biosignatures”) in the atmospheres of extrasolar planets. It could probe deeper than ever into the processes that create stars. And, we can assume, it will send home spectacular images of the cosmos in even greater detail than HST has captured.

Image credit: Frassanito & Associates, Inc. and the Future In-Space Operations Working Group