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GJ 758 B: The planet that wasn't is probably a star that nearly isn't. And in the end it's all about the nature of scientific evidence and how we decide something is true

September 30, 2010 3 comments
image of GJ 758 made with mmt telescope

Thayne Currie and his colleagues created this image of GJ 758 using observations collected earlier this year with the 6.5-meter MMT telescope. The central speckled white region is the star. GJ 758 B lies below and slightly to the right of center.

Well, GJ 758 B, you were almost a planet. But it sure looks like you aren’t anymore, so be big grown-up brown dwarf and get over it, ok?

Last year, it sure seemed like the object dubbed GJ 758 B could be a giant gaseous planet circling a star a lot like our own. It sparked more than a few headlines in the science press, including this one: “First Cool Exoplanet Around Sun-like Star Imaged”

Although the headline seemed to confer planethood on GJ 758 B, the writer included this caveat in the text:

“With an estimated mass of 10 – 40 times Jupiter’s mass, GJ 758 B is either a giant planet or a lightweight brown dwarf.”

A lightweight brown dwarf, y’understand, is a dim, cool ball of gas too big to be a planet but too small to ignite fusion of hydrogen into helium in its core so it can radiate lots of energy and thus claim star status.

Brown dwarfs are the almost-but-not-quites of the stellar zoo. Sure, they can fuse a slightly heavier form of hydrogen, deuterium. But that doesn’t make it a full-fledged star. Brown dwarfs are, in astro-speak, “sub-stellar.”

Recently a team led by Goddard’s Thayne Currie reported new information about GJ 758 B. Here is his one-sentence summary of his research paper, published September 13 in Astrophysical Journal Letters:

“We confirm that GJ 758b is the coldest, faintest object that has ever been imaged around a star like the sun, but show that it is probably not a planet, as was originally claimed by some scientists.”

In 2009, a different team reported a preliminary mass estimate for GJ 758 B of “10 to 40” times the mass of Jupiter. Exoplanet people use such “Jupiter masses” as a convenient way to talk about the heft of big planets. Read all the details in a Centauri Dreams post from last year.

click to make me bigger!

The Subaru Telescope captured this image of the sunlike star GJ 758 in August 2009. The light of the star is blocked out, leaving the near-infrared glow of two other objects. New observations suggest GJ 758 B is not a gas giant planet, as previously suspected. There is weak evidence that another object, called GJ 758 C, also orbits the star.

When someone spots a really big ball of gas orbiting another star, mass is the key issue. When does a planet get too big for itself and then have to be called something else?

Currie and his colleagues used the 6.5-meter MMT telescope earlier this year to observe GJ 758 B and get better measurements of its temperature and luminosity (the rate at which the star radiates light). And that allowed them to come up with a better estimate for the object’s mass.

The answer: GJ 758 B most likely exceeds the 13-Jupiter-mass threshold at which sunlike balls of gas start fusing deuterium and are no longer considered planets.

If it all still sounds uncertain, it is. Or should I say: Of course it is.

Reporters and bloggers prefer clear, simple answers. But that is not what science usually provides. Science builds up better and better evidence for a particular interpretation of evidence, called a hypothesis.

I asked Currie how sure he was that GJ 758 B is not a planet. He said:

“Well, as with all things in science, we don’t have ‘proof.’ However, a couple of highly improbable things would have to conspire together in order to make its mass be consistent with a planet.”

One of those improbables is that the star would have to be much younger — less than a billion years old — than all the signs point to.

For instance, there is a sign called chromospheric activity, which is associated with the amount of heating that occurs above the visible surface of a star. Chromospheric activity decreases with age. And the degree of it we see from the star GJ 758 is similar to that of our own sun — our middle-aged, 4.6-billion year-old sun. Hold that thought for a moment.

Theories of planet formation say that if GJ 758 B is less than 13 Jupiter masses, and therefore a planet, it’s home star should be about a billion years old. But it would be very strange indeed for a star that young to have the relatively low level of chromospheric activity that we see.

Get it? Given all the information we have, it’s more likely that GJ 758 B is a brown dwarf.

So in the end, whether GJ 758 B is a planet depends on other things being correct or incorrect, including theoretical models for how planets form and how old certain types of stars are based on things we can measure, like chromospheric activity.

If you unpack the whole GJ 758 B discussion/debate, it actually turns out to be about something much bigger: What constitutes evidence, and how do we come to trust a particular interpretation of it?

Well, that sure sounds like the essence of the debate over global climate change. And the controversy over “intelligent design” vs. Darwinian evolution. And part of the reason why millions of middle-aged women were given estrogen replacement therapy only to find out later that it was associated with an unexpectedly large risk for cancer and heart disease.

Who knew a story about a little star called GJ 758 would actually turn out to be a lesson in the philosophy of science?

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OH AND DID I MENTION? All opinions and opinionlike objects in this blog are mine alone and NOT those of NASA or Goddard Space Flight Center. And while we’re at it, links to websites posted on this blog do not imply endorsement of those websites by NASA.

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The Sun Gets Loopy (again): Blogolicious Image of the Day

September 28, 2010 2 comments

This week the Solar and Heliospheric Observatory (SOHO) “Pick of the Week” offers a video clip of a massive loop of hot plasma caught by one of NASA’s twin STEREO spacecraft. Here’s a video loop of the event, compressing hours of time into a few seconds.

http://www.youtube.com/v/dLqfcHE95V0?fs=1&hl=en_US

Says the SOHO website:

The STEREO (Ahead) spacecraft watched as an eruptive prominence near the back of the Sun arched up but then headed back to the Sun’s surface over a few hours (Sept. 19, 2010). Prominence eruptions occur fairly frequently and with both STEREO spacecraft now able to see most of the Sun, we do observe more of them.



And one great prominence deserves another. Check out this whopper from back in April:

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OH AND DID I MENTION? All opinions and opinionlike objects in this blog are mine alone and NOT those of NASA or Goddard Space Flight Center. And while we’re at it, links to websites posted on this blog do not imply endorsement of those websites by NASA.

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Gogblog vodcast #2: Watch an Atlas 5 launch of a military satellite from Goddard's Flight Dynamics Facility

September 27, 2010 1 comment

One recent Saturday in August, I woke at 4:30 a.m., rubbed my eyes in the early morning darkness, and headed for Goddard Space Flight Center to watch the launch of an Atlas 5. The rocket blasted off from Cape Canaveral in Florida, carrying a military communications satellite into high geosynchronous orbit.

My perch: the Flight Dynamics Facility, which I described in an earlier post about FDF’s support of Shuttle and Space Station missions.

The FDF operations area is a large room packed with computer workstations. The mission of the FDF is to provide precise pointing coordinates to enable ground stations and satellites to track launch vehicles like the Atlas V into space. FDF also pitches in to track the Shuttle orbiter and the Space Station in low-Earth orbit to maintain links to the ground.

This video, with voiceover by FDF junior systems engineer Jason Laing, explains some of the major events in the launch of the Atlas V:

http://www.youtube.com/v/XRKWewWDP_E?fs=1&hl=en_US

Today the Atlas will carry the Advanced Extremely High Frequency (AEHF) satellite, the first of three. The system will provide secure global military communications between ground, sea, and air.

Start of show: I got in at around 6 a.m. and met the lead engineer for this launch, Syed Hasan. Bleary-eyed but alert, he got in at 12:30 a.m. to begin check-outs of the computer and communications systems. By Syed’s side for the launch: James Cappellari. A nearly 50-year veteran of NASA, Cappellari helped to develop and implement the Space Network. I deposited the obligatory bucket of donut-like objects in the FDF break room and got ready for “start of show.”

Start of show in the FDF is 10 minutes before launch, which today is slated for 7:07 a.m. At start of show, a TDRS satellite hovering above the U.S. East Coast will start tracking the Atlas right on the pad. Today it is TDRS 10, but TDRS 4 is also available for East Coast launches.

artist concept of the AEHF satellite

The AEHF satellite

FDF’s partner in this and other launches is the White Sands Complex in New Mexico, which controls the satellites comprising NASA’s Space Network. Eight TDRS satellites currently provide global tracking, communications, and data links for manned and unmanned spacecraft. When rockets phone home, it is often via the TDRS network.

About the time I arrived at FDF, Syed sent something to White Sands called an autothroughput test vector. This tests the system that would allow FDF to send pointing data directly to the TDRS satellites during launch, bypassing White Sands.

But that would only happen if the satellites drifted off their targets and needed to be repointed. Throughout the launch the ELV (expendable launch vehicle) team at FDF watches to make sure the satellites are pointing at the rocket and able to track it accurately. FDF supports 10 to 15 ELV launches per year.

The rocket “talks” to the ground via data links, so accurate pointing is important. During Space Station missions, accurate pointing of TDRS’ high bandwidth antennas allows astronauts and cosmonauts to wave hello to us earthlings via video downlink. Scientific spacecraft also use TDRS to pipe data to the surface on a regular basis. Without accurate pointing of the TDRS satellites, NASA’s operations in low-earth orbit would be much more limited.

photo of Syed Hasan and James Cappellari

Syed Hasan (left) and James Cappellari

As lead engineer on the ELV team today, Syed runs some FDF software called acquisition data generator, which he would use to create and send a pointing correction vector during launch, if needed. Rows of numbers on his monitor allows Syed to keep an eye on the actual “beam angles” of the TDRS antennas indicating what direction they point.

But FDF now has another tool in their kit for making sure the Space Network is on target. It’s called the SN Beams Display, and it was developed by FDF engineers with a combination of commercial and in-house software code. Today, FDF’s John Bez is manning the SN Beams.

The SN Beams creates a live view of the spacecraft from pad to orbit as well as the TDRS “beams.” Each beam is a cone of space, rendered in green or white, that indicates the position and coverage of the antenna. When a launch vehicle or satellite leaves the beam, it is out of range to that particular satellite, and another in the network must pick up the tracking — sort of like relay racers passing the baton.

During launches, the SN Beams provides visual clues to the FDF about the difference between where each satellite is supposed to be pointing (green), based on pre-calculated pointing data, and where the satellites are actually pointing (white).

Two other members of the team, Eric Smith and Jason Laing, are on hand to check the position of the launch vehicle at several key stages of the launch based on actual telemetry data from the rocket. For this they use two terminals running the “LRP” software, for Launch Reentry Processor. If the craft is not where it’s supposed to be, it might be necessary to adjust the pointing data for the TDRS satellites.

Here is a video of the launch of the AEHF rocket! This is video from the launch contractor, ULA:

http://www.youtube.com/v/eqymxhJCEU0&hl=en_US&feature=player_embedded&version=3

Atlas away! The magic moment finally comes at 7:07 a.m., when the Russian-made RD-180 main engine roars to life, supplemented by four solid rocket boosters strapped onto the first stage.

10…9…8…7… you know the rest. There is something about a countdown that is thrilling. It’s a high-stakes game when you launch a multi-billion dollar satellite. There is little room for error.

The early events happen quickly.

At 1:40 into the launch the SRBs cut out; 16 seconds later they jettison. The SN Beams shows this in detail, as three little cartoon SRBs pop off the Atlas V booster and fall into the video game Atlantic Ocean. The live feed from Florida just shows the brilliant plume of the rocket receding into the blue sky.

At 3:27 the faring on the front of the Atlas pops open like two clamshells, exposing the satellite mounted to the top of a Centaur second-stage booster. The main engine is still burning.

At 4:17 the main engine shuts down, an event FDF people call MECO (“mee-koe”), for main engine cut-off. After a short coast, the second stage “Centaur” fires up.

photo of engineers in FDF during atlas launch

Light that candle!

At 14:08, the Centaur shuts off and the vehicle coasts for almost 8 minutes. Then, at 22:17, it fires up again for about 5 minutes to accelerate the satellite into the higher geosynchronous orbit. The Centaur will cut out and finally release the AEHF satellite 51 minutes into the launch.

Two hours after launch, it’s “end of show” for the FDF. At this point, FDF no longer has responsibility for supplying pointing data to White Sands. However, they continue to monitor for some time, just in case their services are needed.

Big fat planet: I have to say, watching this all on the SN Beams was a real surprise to me, because it shows just how huge Earth is and how puny even the mighty Atlas V is in comparison. After the rocket had been blasting away furiously for almost five minutes, it was still barely over the Atlantic Ocean, heading east.

At 10 minutes, the launch vehicle was screaming through the atmosphere at more than 15,000 mph, the Centaur was still firing. After 20 minutes, the craft was barely over West Africa. At the moment the satellite was released, 51 minutes into the launch, it hadn’t completed a single orbit yet.

This tells you that Earth is BIG and massive. Escaping its gravity to a geosynchronous altitude of 22,500 miles requires a lot of fuel and a lot of time.

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OH AND DID I MENTION? All opinions and opinionlike objects in this blog are mine alone and NOT those of NASA or Goddard Space Flight Center. And while we’re at it, links to websites posted on this blog do not imply endorsement of those websites by NASA.

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That Was The Week That Was, September 19-24, 2010. . . A Digest of Goddard People, Science, & Media, PLUS Historical Tidbits and Our Best Stuff in the Blogpodcastotwittersphere

September 24, 2010 Leave a comment

photo of laser ranging system firing beamSUNDAY September 19: On this day in 1961, NASA Administrator James E. Webb announced that the site of the NASA center dedicated to human space flight would be Houston, Texas. This became the Manned Spacecraft Center, renamed the Lyndon B. Johnson Space Center in 1973.

MONDAY September 20: Goddard Flickr site features an image of the big green laser beam taking a distance-measuring shot at the Lunar Reconnaissance Orbiter — and other pix from Saturday’s International Observe the Moon Night.

Lightning bug: a football-sized nanosatellite gets ready to investigate mysterious gamma-ray flashes above storm clouds.

Blueshift: Weekly Awesomeness Round Up features a dwarf galaxy, a lunar pit crater, and other highlights from astronomy and space science.

Try, try again: On this day in 1966, Surveyor 2 launched to the moon. It was the second of a series designed to achieve a soft landing on the moon and to return lunar surface photography for determining characteristics of the lunar terrain for Apollo lunar landing missions. But due to an engine misfire in space, the craft tumbled out of control and made a new crater on the moon 3 days later.

photo of milky way from orbitTUESDAY September 21: Robert Simmon’s Elegant Figures blog resurrects a haunting photo of the Milky Way from orbit snapped by a Shuttle astronaut.

WEDNESDAY September 22: Hubble zooms in on the Lagoon Nebula in vivacious HD video. Cue angelic choir music. . .

Strike zone: The What On Earth blog features a “bedazzling” time-lapsed display of lightning over less than 30 seconds across the Pawnee National Grasslands, as first shown in the Earth science Picture of the Day (EPOD).

Lungfull: a new global map of fine particles of unhealthy air pollution. Later in the week, What On Earth posts audio interviews with the scientists who made the map.

Have a ball: NASA Blueshift takes a road trip to the set of the Big Bang Theory TV show to see a cosmic beachball.

satellite image of fiji firesTHURSDAY September 23: A new computer simulation shows what dust in our solar system may look like to faraway alien astronomers. And Geeked On Goddard talks about the challenges of simulating a billion billion billion interplanetary dust bunnies.

Trouble in paradise: MODIS Image of the Day spots fires on Fiji.

Life science: Inside Astrobiology profiles NASA meteorite researcher Danny Glavin in a new video.

FRIDAY September 24: NASA’s traveling museum exhibition, New Views of the Universe, featuring the Hubble and James Webb Space Telescopes, opens at Imagination Station museum in Toledo today.

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OH AND DID I MENTION? All opinions and opinionlike objects in this blog are mine alone and NOT those of NASA or Goddard Space Flight Center. And while we’re at it, links to websites posted on this blog do not imply endorsement of those websites by NASA.

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Bodies in motion: a computer modeling trick developed at Goddard allows us to simulate what our solar system looks like to aliens

September 23, 2010 1 comment

A few years ago, a University of Maryland graduate student, Christopher Stark, crossed paths with NASA astrophysicist Marc Kuchner. “He landed in my office and asked me if I had any projects,” Kuchner recalls.

Stark needed to do some interesting and original science so he could become a professional scientist instead of a professional student; Kuchner needed help with his interesting and original research on how planets sculpt the disks of dust and gas in alien star systems, creating features like rings, gaps, and clumps.

And maybe, just maybe, by imaging those rings, gaps, and clumps in disks of dust around alien star systems, we might be able to discover planets. In other words, we might find planets by spotting their gravitational pull on their surroundings, as opposed to taking a picture of the actual planets, which is a rare and delicate trick.


http://www.youtube.com/v/BYQZRgWwXgQ?fs=1&hl=en_US


New model

Fast forward to summer 2010. Stark finishes his PhD thesis on computer modeling of dust disks around alien stars, gets a sweet job at Carnegie Institution for Science in Washington, D.C., and is the lead author on a paper describing aforementioned interesting and original science in the September 7, 2010, Astronomical Journal. Life is good!

Read the Goddard Space Flight Center press release and video for the science details. Stark and Kuchner basically simulated the dust in our own solar system and showed what it would look like to alien astronomers observing from afar. (Hint: they can see a ring-shaped collection of dust with a gap due to the influence of Neptune.)

Here, let’s talk about how Stark and Kuchner simulated dusty solar systems in the supercomputer down the hall from me.

neptune_dust_202

click to make me bigger!

The “debris disks” around stars contain an unimaginable number of tiny grains of dust — “dust” being tiny clots of crusty minerals and frozen vapors. Fluffy interplanetary dust bunnies, really.

As planets orbit, their gravity can induce rings and clumps in the dust. And because warm interplanetary dust radiates infrared energy, telescopes trillions of miles away can actually SEE the rings and clumps even though they can’t see the planets creating them.

Kuchner and Stark decided to build a more realistic computer simulation of dusty disks with planets. It could prove a pretty handy tool for spotting planets someday.

The problem: too many dust bunnies! Getting a computer to track the movements and interactions of so many bits of stuff is, well, practically impossible.

Ever heard of the “three body problem”? For physicists of olde like Sir Isaac Newton, calculating the motions of three gravitating bodies in free space was enough to induce cardiac arrest. Dauntingly, terrifyingly, slide-rule-breakingly hard.

“How,” Kuchner asks, “do you figure out the answer without having to figure out a billion billion billion collisions?”

Stalking dust bunnies

Tracking a billion billion billion dust bunnies is not even worth considering, even with the formidable computing resources down the hall from me at Goddard, that being the Discover supercomputer.

But Stark and Kuchner found a way. They call it the collisional grooming algorithm.

An algorithm is a precise set of mathematical rules that describes how to solve a problem. Stark and Kuchner used it to simulate 75,000 virtual dust particles and track their motions and number in response to grain-grain collisions and the gravitational tug of planets.

But what about all the other dust bunnies, the billion-billion-billion?

“We allow each single integrated particle to represent many dust grains,” Stark explains. “We scale the number of dust grains up and down to control how much dust is in the disk, even though we only actually integrate 75,000 particles.”

But let nobody leave the room thinking that approximating the behavior of 10 billion billion billion dust bunnies is easy.

At Goddard, we have a supercomputer called Discover. The thingies that do the actual data processing in a computer are called processors, and Discover presently has about 15,000 of them. That’s the number of processors in 7,500 MacBook Pro laptops like the one I used to write this blog post. Which is to say, my laptop packs an Intel Core Duo, or two processors, whereas the Discover supercomputer packs about 15,000 processors. Soon, Discover will double in capacity to nearly 30,000 processors.

To run Stark and Kuchner’s interplanetary dust bunny simulation required about 3,000 processors — the equivalent of 1,500 MacBook Pro’s — running for 24 hours!

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OH AND DID I MENTION? All opinions and opinionlike objects in this blog are mine alone and NOT those of NASA or Goddard Space Flight Center. And while we’re at it, links to websites posted on this blog do not imply endorsement of those websites by NASA.

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That Was The Week That Was, September 12-18, 2010. . . A Digest of Goddard People, Science, & Media, PLUS Historical Tidbits and Our Best Stuff in the Blogpodcastotwittersphere

September 17, 2010 Leave a comment
Mae_Jemison_202

Mae Jemison

Sunday September 12: “…but because it’s hard.” On this day in 1962, President John F. Kennedy delivered his famous moon speech at Rice Stadium and inspired a generation. Mae Jemison had a dream, which was to fly in space. And she did it on this day in 1992 as the first African American woman in orbit.

Monday September 13: See the sea ice snapshot of the Arctic by the Aqua satellite.

NASA Blueshift: Weekly Awesomeness Round Up looks at highlights of the past week, including planet-eating stars and a golden moment for the Webb Telescope’s mirrors.

Wednesday September 15: The Lunar Reconnaissance looked
over its shoulder at Earth on September 9 and captured
this global portrait.

sea-ice_202

Sea ice



Thursday September 16: The lunar surface is more complicated than you think. Lunar Reconnaissance Orbiter reveals why. Don’t miss the cool video about LRO’s crater counting laser altimeter instrument.

The sun gets loopy: see a new video of looping prominences on the surface of the sun.

Antarctic ozone hole: watch the latest satellite snapshot.


Friday September 17: What On Earth blogger Adam Voiland’s Earth Buzz features Beetle-mania, Igor the Beautiful, and IceSat’s icy adventures.

Rooftop robots: check out a video of robotic instruments on the roof of Building 33 at Goddard.

Big chill: NASA Goddard technicians prep Webb Telescope parts for deep freeze test.

Saturday September 18: Got moon? Earth’s moon, that is. Join the global gathering International Observe the Moon Night this Saturday night to celebrate our companion in the solar system.

lnOMNLogo_circleLg_594

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OH AND DID I MENTION? All opinions and opinionlike objects in this blog are mine alone and NOT those of NASA or Goddard Space Flight Center. And while we’re at it, links to websites posted on this blog do not imply endorsement of those websites by NASA.

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The Sun gets loopy: blogolicious image of the day

September 15, 2010 Leave a comment

Steele Hill, Goddard’s salesman of all things solar, just posted the latest weekly release of Sun imagery, courtesy of NASA’s Solar Dynamics Observatory. Steele dubs it “The South Rises Again”

SDO watched as an active region in the Sun’s southern hemisphere produced a whole series of looping arcs of plasma in profile (Sept. 11-13, 2010).  The arcs are actually charged particles spiraling along magnetic field lines.  The images were taken in extreme ultraviolet light and reveal the dynamic activity visible above active regions.  The material seen here is ionized iron heated to about one million degrees.  We have seen very little activity in this hemisphere as opposed to the northern one, hence the tongue in cheek title.

This image is a feast, but it’s true beauty shines through when you play the video. It’s a whopper of a file, so make sure you’ve got a fast Internet connection and give it a few seconds to download.

Loop_profile_608

click to zoom in on the action

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OH AND DID I MENTION? All opinions and opinionlike objects in this blog are mine alone and NOT those of NASA or Goddard Space Flight Center. And while we’re at it, links to websites posted on this blog do not imply endorsement of those websites by NASA.

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Chillaxing in deep space with the James Webb Space Telescope: Stay frosty, little mercury cadmium telluride infrared detector chip!

September 14, 2010 2 comments

webb art
With a 6.5 meter diameter mirror, the James Webb Space Telescope will operate at a temperature of only 35 degrees above absolute zero in a deep space orbit.


Imagine you are a mercury cadmium telluride infrared detector chip, chillaxing in deep space nearly a million miles from Earth.

(OK, I know it’s a stretch, but give it a try.)

You are riding on the James Webb Space Telescope, the most high-tech space observatory ever attempted. But in the end, mission success rides on you, little infrared photon detector chip! You are the retinas of this great observatory. It sees only as well as YOU see.

So you are sitting there, peering out at the darkness, waiting for a photon from the dawn of the universe to pierce your semiconductor crystal matrix and knock an electron out of its comfy valence shell and into the conduction band. This generates the faintest of electric currents. This means data: the stuff of astronomical discoveries.

But 12 times an hour, the humming of electrons in your crystal guts is an illusion, a lie. Infrared telescope scientists call it dark current.

I learned about dark current at a recent colloquium here at Goddard. Three heavy hitters in the Webb Telescope project gave an update on the fabrication and testing of this multi-billion dollar space telescope.

Mark Clampin, the Webb Telescope project scientist, brought us up to speed on the observatory as a whole. He mentioned that 17 percent of Webb’s “flight mass” — the stuff that will blast into space on a giant Arianne launch vehicle — is now built. That represents about a billion dollars in gear.

Randy Kimble also spoke. He is the Webb mission’s Integration & Test Project Scientist. He gave us a progress report on the telescope’s instruments. And it was all good news: The flight versions of the instruments — again, the ones that will actually go into space — will begin arriving at Goddard next summer to be shaken, frozen, and irradiated during a series of grueling tests.

But the first speaker — the one who introduced “dark current” to my vocabulary — was John Mather. He gave a concise summary of the observatory’s science mission.

At one point, he bragged up Webb’s detectors. These are the chips, like the CCD in your digital camera, that turn infrared photons from farthest cosmos into trickley little electric currents and, ultimately, astronomical data.

(You may recall that John C. Mather shared the 2006 the Nobel Prize in Physics with George F. Smoot for their discoveries related to the microwave background glow from the Big Bang, using the COBE satellite.)

The detectors are kept cold by a combination of the ambient chill of deep space and a lot of clever engineering to block the sun’s rays and isolate the instruments from 220 watts of heat radiating from the telescope’s on-board electronics. Mather bragged that Webb’s infrared detectors have “dark currents measured in a few electrons per hour per pixel.”

Huh? Dark what? The phrase “dark current” and the idea of measuring single electrons per hour set off my cool-o-meter.

As the colloquium ended, I hurried to the head of the room hoping to grab Mather’s attention before someone else got to him. “The statistic you mentioned about dark currents. Can you explain?”

He said that each pixel of each detector spontaneously generates about a dozen electrons per hour — that’s the dark current — simply staring off into empty space. Hence the term: dark current. A perfect detector would produce nothing, just total silence, unless an actual infrared photon came in and bonked one of its atoms.

But, hey, 12 electrons per hour is pretty dark! And out of that darkness, we hope, will come the data to illuminate our understanding of the birth of the first stars, the evolution of galaxies, and the nature of planetary systems around other stars.

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OH AND DID I MENTION? All opinions and opinionlike objects in this blog are mine alone and NOT those of NASA or Goddard Space Flight Center. And while we’re at it, links to websites posted on this blog do not imply endorsement of those websites by NASA.

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Gogblog Monday Video Rewind Picture Show: What Fueled 2005's Hurricane Season from Hell? Here it is A to Z.

September 13, 2010 Leave a comment
27stormsTitle

CLICK ME to open a new window and watch the video

It’s hurricane season. And if you live on the Atlantic Coast, like gogblog, you sometimes get to wondering. . . What gives birth to these giant storms? How do tropical storms grow into hurricanes? Why do some fade early, while others reach category 5?

Watch this colorful and dynamic Goddard TV web short to get the answers: 27 Storms: Arlene to Zeta. It looks back on the destructive 2005 hurricane season — the one that gave us Katrina and the New Orleans catastrophe. The season birthed an astounding 27 named storms, beating 1933’s record of 21 nameable storms.

Got FiOS or some other fast Internet access? Go to the Scientific Visualization Studio website to download high-resolution versions of the video.

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OH AND DID I MENTION? All opinions and opinionlike objects in this blog are mine alone and NOT those of NASA or Goddard Space Flight Center. And while we’re at it, links to websites posted on this blog do not imply endorsement of those websites by NASA.

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That Was The Week That Was, September 6-10, 2010. . . A Digest of Goddard People, Science, & Media, PLUS Historical Tidbits and Our Best Stuff in the Blogpodcastotwittersphere

September 10, 2010 Leave a comment

moon_202MONDAY September 6: Blueshift’s Weekly Awesomeness Round Up highlights Stephen Colbert’s astronaut encounter, an image from an Indian radio telescope, America’s top chef in orbit, and other astronomical-scientific tidbits of the previous week.

TUESDAY September 7: Sensors on Terra and Aqua satellites spot fires for a new United Nations website.


WEDNESDAY September 8: LROC Image of the Day: the moon seen from the east.

It’s a blast: Sunspot 1108 erupts!

Dick_Ewers_202GRIPping tale: On the What On Earth blog, Q&A with Dryden Flight Research Center DC-8 pilot Dick Ewers and the GRIP mission.

Bug attack: Satellite data reveals beetle’s deadly attack.

Special delivery: The Canadian Space Agency ships a test unit of the Fine Guidance Sensor for the James Webb Space Telescope to Goddard.


THURSDAY September 9: Planets torn apart by solar tides! And what the Christian Science Monitor had to say.

Hail and farewell: On this day in 1975, Viking 2 blasted off for Mars.

hot_jupiters_202RATS! Two Goddard scientists head for the Arizona desert to test technology and procedures for exploring other planets.

Southern sizzle: MODIS Image of the Day shows fires in Brazil.

Gold record: the first Webb Telescope mirror gets its final reflective coating.


FRIDAY September 10: New video profiles Goddard astrobiologist Geronimo Villanueva.

River of sorrow: NASA Earth Observatory Image of the Day shows the swollen Indus River and flooded fields from orbit.

Say what? The What On Earth bloggers have posted an Earth-related mystery sound. Well, THAT narrows it down! See if you can guess what it is.

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OH AND DID I MENTION? All opinions and opinionlike objects in this blog are mine alone and NOT those of NASA or Goddard Space Flight Center. And while we’re at it, links to websites posted on this blog do not imply endorsement of those websites by NASA.

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