Jupiter Impactor Probably an Asteroid

What was it that left such an interesting infrared signature in Jupiter’s atmosphere on July 19, 2009? The images below, made with a wide variety of instruments, show what appears to be the debris of an object that collided with the planet. The event was first noted by amateur astronomer Anthony Wesley in Australia, who tipped off an international team of scientists that went on to combine data from three infrared telescopes to study the impact, looking at atmospheric temperatures and the chemical signatures of the debris. The conclusion: The object was most likely an asteroid.

Image (click to enlarge): Eight different looks at the aftermath of a body — probably an asteroid — hitting Jupiter on July 19, 2009. Amateur astronomer Anthony Wesley was the first to capture an image of the impact, with a visible-light camera attached to his telescope in Australia. A NASA Hubble Space Telescope image was obtained in visible light. Infrared images were obtained by NASA’s Infrared Telescope Facility and the Gemini North Telescope, both atop Mauna Kea, Hawaii, and the European Southern Observatory’s Very Large Telescope in Chile. The images were taken between July 19 and 26, 2009. Credit: NASA/JPL-Caltech/IRTF/STScI/ESO/Gemini Observatory/AURA/A. Wesley.

The results, reported in two papers in Icarus, show that the impact debris in 2009 was denser than debris from comet Shoemaker-Levy 9, which broke apart and impacted Jupiter in 1994. Jupiter is getting to be a lively place now that we have so many eyes on it — remember the two impacts in the summer of 2010 — but the 2009 event is proving useful indeed, given the amount of data available and the fact that the evidence points to an asteroid impact. Until recently, icy ‘Jupiter-family’ comets were the only objects thought likely to strike Jupiter.

So is the giant planet unable to clear its orbit completely when it comes to small objects like asteroids? Perhaps so. In any case, the asteroid signature seems strong. Here’s Leigh Fletcher (Oxford University) on the matter:

“Comparisons between the 2009 images and the Shoemaker-Levy 9 results are beginning to show intriguing differences between the kinds of objects that hit Jupiter. The dark debris, the heated atmosphere and upwelling of ammonia were similar for this impact and Shoemaker-Levy, but the debris plume in this case didn’t reach such high altitudes, didn’t heat the high stratosphere, and contained signatures for hydrocarbons, silicates and silicas that weren’t seen before. The presence of hydrocarbons, and the absence of carbon monoxide, provide strong evidence for a water-depleted impactor in 2009.”

A cometary nucleus would have been unlikely to have penetrated as far into the Jovian atmosphere as this impactor, and the detection of silica in the debris firms up the idea that we’re dealing with a strong rocky body that exploded deep in the clouds. Going under the assumption that the object had a density of around 2.5 grams per cubic centimeter, the researchers calculate its diameter at 200 to 500 meters. An object called 2005 TS100, though not the impactor in this event, has made several close approaches to Jupiter in computer models, demonstrating a chaotic orbit of the kind that could have brought this object into contact with the planet.

JPL points out in this news release that asteroids of this size hit the Earth about once every 100,000 years, but we don’t have a good idea what the frequency of asteroid strikes on Jupiter is. But the diversity of objects hitting the giant planet seems to be raising eyebrows. Paul Chodas works at NASA’s Near-Earth Object Program Office at JPL:

“We weren’t expecting to find that an asteroid was the likely culprit in this impact, but we’ve now learned Jupiter is getting hit by a diversity of objects. Asteroid impacts on Jupiter were thought to be quite rare compared to impacts from the so-called ‘Jupiter-family comets,’ but now it seems there may be a significant population of asteroids in this category.”

The 200 trillion trillion ergs of energy (the equivalent of 5 gigatons of TNT) released in this event not only created a channel of super-heated atmospheric gases and debris but also launched debris back above the cloud tops that splashed down a second time into the atmosphere, dredging up gases like ammonia from the troposphere and heating the lower stratosphere by as much as 4 degrees Kelvin, a significant amount of energy given the area affected. As we continue to learn, the outer Solar System can be a violent place, and it’s heartening to see amateur astronomy feeding professional follow-ups that help us learn more about it.

The papers are Orton et al., “The atmospheric influence, size and possible asteroidal nature of the July 2009 Jupiter impactor,” Icarus Vol. 211, Issue 1, pp. 587-602 (abstract) and Fletcher et al., “The aftermath of the July 2009 impact on Jupiter: Ammonia, temperatures and particulates from Gemini thermal infrared spectroscopy,” Icarus Vol. 211, Issue 1, pp. 568-586 (abstract).


100 Year Starship Meeting: A Report

by Marc Millis

On January 11 & 12, I participated in a gathering of roughly 30 individuals to learn about and discuss the DARPA/Ames 100-year Starship Study. In addition to reporting on those events, I’ve included my personal commentary at the end of this report.

Recall that in October 2010, the Director of NASA/Ames, Pete Worden, inadvertently revealed that DARPA was funding Ames to the tune of $1M for such a study. This triggered something of a media flurry and shortly thereafter DARPA issued this press release. This January meeting was the first step in their process to involve the insights of others. I requested and was granted an invitation.

The gathering was held in a 1903 fort that had been converted a couple of years ago into a modern lodge and meeting area (Fort Baker, now Cavallo Point). Its location near the base of the Golden Gate Bridge provided a calm, out-of-the-way location with few distractions. The meeting began at noon on the first day, carried on (with breaks) through cocktails and dinner, and then resumed on the second day, running through lunch. The organizers invited Peter Diamandis (ISU founder, X Prize Founder, etc) to facilitate the meeting and Peter did an excellent job of stepping through the original agenda and giving everyone a chance to be heard.


Of the roughly 30 attendees (not including supporting staff, such as the stenographers), about half were from NASA/Ames and DARPA. Aside from one NASA HQ representative (the new resurrected NIAC lead, Jay Falker), no other NASA center was represented. In alphabetical order:

DARPA Attendees
Paul Eremenko
Roger Hall
David Neyland – Progenitor of this 100-year study

NASA Attendees
Matt Daniels (Ames & Stanford PhD student)
Jay Falker (NASA-HQ & new NIAC lead)
Rachel Hoover (Ames, Public Affairs)
Peter Klupar (Ames)
Larry Lemke (Ames)
Creon Levit (Ames – assigned to lead this 100-yr study)
Lisa Lockyer (Ames)
Alex MacDonald (Ames)
Dawn McIntosh (Ames – on temporary assignment to DARPA)
Alen Weston (Ames)
Pete Worden (Ames Director)

Other Attendees
Elizabeth Bear (Science Fiction writer)
Jim Benford (Microwave Sciences)
Peter Diamandis (Xprize Foundation, etc)
Lou Friedman (Planetary Society [retired])
Joe Haldeman (Science Fiction writer)
Barbara Marx Hubbard (Foundation for Conscious Evolution)
Mae Jemison (Former Astronaut, now active in various educational endeavors)
Harry Kloor (Chief science advisor for the X Prize organization)
Marc Millis (Tau Zero Foundation)
Alexander Rose (Long Now Foundation)
Jack Sarfatti (StarDrive.org)
Dan Shekow (Global Universal Entertainment)
Jill Tarter (Search for Extraterrestrial Intelligence – SETI Inst.)
Jacques Vallée (Euro-America Ventures & Co-developer of ARPANET [led to Internet])
Craig Venter (J. Craig Venter Institute, first to sequence the human genome)
Claudia Welss (Assistant to Barbara Marx Hubbard)

The planned agenda consisted of cycling through 3 break-out discussions (10 to a team), to discuss respectively the “why, what, and how” of an organization, where each cycle consisted of one team reviewing the notes of the prior team. The overall goal of the organization is to sustain research that will lead to the creation of a starship in roughly 100-years, and to inspire students along the way. By asking “why-what-how,” it was hoped to flesh out some substance to define that organization.


This brings me to an important point. The meeting and the DARPA funding is about creating an organization that could last for 100-years, rather than about the technological and sociological advancements necessary to eventually create starships. In fact, the funding is not allowed to be spent on any research or educational activities related to interstellar flight, but instead can only be used to define that organization. As much as I really like the name, “100-yr starship,” this study should instead be called the “100-yr organization study.”



Although there was some debate challenging the assumption that one lasting organization is the key element to make interstellar flight happen, the attendees followed that premise and the “why-what-how” cycle of questions. Next are some preliminary results of those discussions, but it must be stressed that these do not constitute conclusions passed on to DARPA/Ames, but rather reflect the provisional thoughts that came out in the course of this first set of discussions. This is not the final word.

Also, I am not endorsing, nor dismissing, these results, but rather I am simply reporting them to the limits of my abilities and my own biases. I post my own comments at the end of this report.

WHY go to the Stars?
After much discussion, the key motivations for interstellar flight were distilled down to the five items listed in the first column of the table and then voting was used to compare their relative importance from three different perspectives: (1) what the attendees felt for themselves, (2) the anticipated priorities of fund sources, and (3) the anticipated priorities of the general public. Again, these reflect the discussions rather than being “THE” final answers.

LanguageSpecific spoken and gestural (bodily) systems of communication, including vocabularies and grammars.Some languages assign gender to nouns, while others do not.
EthicsConcepts of right and wrong, justice, and fairness.Some cultures execute murderers, while others do not.
Social RolesRights and responsibilities differ by categories such as age (child, adult), gender (man, woman), and status (peasant, King).Cultures differ in the ages at which people take on certain rights and responsibilities, and specifically what those rights and responsibilities are.
The SupernaturalConcepts regarding a universe considered fundamentally different from daily experience.Different cultures worship different gods, goddesses, and other supernatural entities.
Styles of Bodily DecorationHuman identity is often communicated by bodily decoration, either directly on the body or with clothing.Some cultures heavily tattoo the body while others communicate identity more with clothing styles
Family StructureConcepts of kinship or relations between kin, and associated ideas such as inheritanceSome cultures are polygynous, where males have several wives, and some are polyandrous, where females have several husbands.
Sexual BehaviorRegulation of sexual behavior, including incest rules.Cultures differ in the age at which sexual activity is permitted.
Food PreferencesConcepts of what are appropriate food and drink in certain situations.Some cultures eat certain animals while others consider them unfit to eat.
AestheticsConcepts of ideals, beauty, and their opposites.Some cultures value visual arts more than song, and vice versa.
Ultimate Sacred PostulatesCentral, unquestionable concepts about the nature of reality.Some cultures consider time to be cyclic while others consider it linear.

In contrast, here is what I jotted in my notes from my own impulsive thoughts:

• For humanity to survive and thrive
• To conquer frontiers instead of each other
• Because its just so damn cool
• To find out what’s really out there

Two other provocative subjects that came up in the course of these discussions were, should this be an international or USA organization, and should humans be considered part of eventual interstellar voyages? Regarding international or USA, the group eventually reached a consensus (not unanimous) for an international effort. And after lively discussion about robotics, transhumanism, and who would likely go on the first missions, it became obvious that human survival, via expansion into space, was a key motivation.

Although the agenda questions included “Who should go?” it became clear that this question was premature. It is way too early to judge such things, and nothing done today about this would still be valid by the time human interstellar flight actually becomes possible. In the course of reaching this conclusion, there were several well-made, yet contrary opinions.

WHAT does the organization need to do to fulfill those motivations?
Rather than sticking to the task of defining what an organization needs to do to last long enough to enable interstellar flight, the discussion turned instead to contemplating some of the milestones that would have to occur toward enabling interstellar flight. This is what they came up with. Please note: I do not agree with much of this list. I’m simply reporting it:

5 yrs:
• Prove other habitable worlds exist
• Create a credible plan
• Create a world view of hope
• $500 million (receipts) blockbuster movie

10 yrs:
• Land humans on Mars
• Communicate faster than light-speed
• Generation of life from computer code without a biological cell
• Ability to sink carbon on Earth faster than we’re creating it (leads to terraforming Mars and other planets)

20 yrs:
• Image of other Earth-like planet
• Telepresent probe on the surface of Europa
• ECLSS (Closed-loop life support)

25 yrs:
• Reflect energy off an exoplanet

30 yrs:
• Non-propellant satellite to Oort Cloud

With the exception of echoing the need for closed-loop life support, I personally refrained from most of this discussion so as to not impede their own flow of thoughts. We (at Tau Zero) are already working to define such next-steps and I wanted to use this as an opportunity to hear an independent set of views.

HOW can an organization be created and how can it achieve such milestones?
This part of the discussion never really jelled for a number of reasons. First, little time was left after distilling the “Why” and “What” sections. Next, the agenda was adjusted on the second day to give 1 minute each for existing interstellar organizations to describe themselves to the group. And lastly, this discussion met with very divergent points of view – too many to distill down to a set of key points in the remaining time. Despite that understandable lack of resolution, here are some of the interesting debates:

Origins of Organizations
The ingoing assumption by DARPA/Ames is that a new organization is needed for interstellar flight, and that need is enough to warrant a $1-million dollar study for its creation. That assumption was challenged by more than just myself. In addition to my own lessons, others also asserted that organizations come into existence after pioneers start making progress, rather than the other way around. Tsiolkovsky and Oberth, for example, did their work before there were rocket societies. Inspired by such pioneers, such rocket societies were later created to accelerate progress. [That pattern is exactly the strategy of Tau Zero: find the pioneers and help accelerate their progress through the collaboration and support.] Eventually the rocket societies and clubs led to government-supported work when their promising innovations looked like they could meet national goals (such as Apollo or the bombing of London with V2 rockets).

The main DARPA/Ames counterpoint was that if the right organization can be created and funded sufficiently, the rest would follow.

Type of Organization
While the consensus was that this should not be a government organization, most of the points and counterpoints were just anecdotal. The antigovernment stance seemed rooted in the frustrations felt by many. The US government in particular was criticized as being too short-term in its thinking and more self-serving than meeting the needs of governance. Nonprofit groups seemed to be the crowd favorite for a time, but the power of for-profit corporations was raised clearly as well. The point counterpoints involved the altruistic stance of nonprofits versus the power of commercialism – even if self-serving. When it came to the features of longevity and the ability to accomplish huge tasks, the role of government once again emerged. In contrast to the ingoing premise of a single, long-lived organization, the cycling of this discussion did more to accentuate how great accomplishments need a mix of organizations rather than one organization to do it all.

The point of longevity and the ability to raise funds also evoked discussion of religion. Several times throughout the other “why” and “what” discussion, religion also came up. I regret that I do not have the talent to capture accurately all those points and counterpoints. Those comments flew too fast and varied to be captured dispassionately. What is certain is the religious discussions got quite righteous and divisive. No overall consensus was reached regarding whether religious organizations should be a part of such endeavors, or even act as a role model for such endeavors.

Fundraising & Resources
Assuming a non-government entity, the prevailing notion was to secure wealthy supporters and establish lasting endowments… and to capitalize heavily on the fruits of the labor, even marketing the branding of such cool-sounding names as the “100-year starship.” Ideas for block-buster movies were provisionally mentioned.

Credibility was also raised as a necessary point in fundraising, but here I got confused. To me, credibility means that the organization has demonstrated that it produces reliable and relevant progress that others can rely upon to guide future decisions. In the context of this group, however, “credibility” was seen in terms of getting “big-name” supporters to first back the idea and then use their name recognition to bring in other supporters. The idea of putting an ad in the New York Times with the top 100 supporters of the 100-year starship organization was enthusiastically discussed.

While the prominent notions of “resources” were in terms of funding, a few participants brought up the fact that people are a resource, including the individuals who are making progress today and the students who will become tomorrow’s pioneers.

Lessons from Other Organizations
In addition to my own overt frustration that other organizations were not considered in the formation of this study, a few others echoed this issue. The omission of the British Interplanetary Society (which is just two decades short of a century in longevity) was brought up. To accommodate these concerns, the agenda of the second day was changed. Rather than using the remaining time to distill the “how” discussions to a short list , each of the represented organizations was given one-minute to address the whole group. I regret that my note-taking did not keep up with all those who spoke, but at least I jotted notes on the following (alphabetical by speaker):

Jim Benford: Spoke about Project Icarus (and as part of the Tau Zero Foundation)

Lou Friedman: Although retired from The Planetary Society, Lou spoke of the TPS and his own attempts to launch a solar sail mission

Barbara Marx Hubbard: Spoke of her Foundation for Conscious Evolution, which deals, in part, with the spiritual evolution of humanity

Mae Jemison: Discussed her numerous educational organizations and the importance of involving parents

Marc Millis: Obviously I spoke of the recent accomplishments of the Tau Zero Foundation, and our strategy to find and support the collaboration of pioneers and to keep the public informed via our Centauri Dreams news forum.

Alexander Rose: Introduced the Long Now Foundation, mentioned that it gets funding largely through a few wealthy folks, and spoke about their millennia clock project.

Jack Sarfatti: Briefly mentioned wanting to start the equivalent of “Star Fleet Academy” in the Presidio in the Bay Area, and his StarDrive.org.

Dan Shekow: As a part of his Global Universal Entertainment company, spoke of the possibility of producing block-buster, society-changing movies to drive public interest.

Jill Tarter : Described the SETI Institute (Search for Extraterrestrial Intelligence) and its long history of listening for intelligent signals from space, and the support from Paul Allen for its latest antenna array.

Final Discussions
While wrapping up, each person at the meeting was given a chance to make closing remarks, many of which echoed ongoing discussions. Here is a condensed set of those parting comments:
• When another habitable world is found, the interest in interstellar flight will bloom
• Define the “Big Questions” whose solutions are needed
• Be sure to involve other existing organizations in future discussions
• Be sure to involve a mixture of disciplines. Social sciences and other nations/cultures were not adequately represented at this meeting
• Capitalize on the “coolness” factor

The DARPA/Ames folks said they needed to digest these discussions before embarking on a next step, but one thing mentioned several times was to have a “bidders conference” in preparation for a solicitation about studies to define the organization. No funding will be allowed for research or educational activities toward interstellar flight. No timeline was mentioned for when the next step would be announced.


When I heard about this study back in October, including the way it was disclosed, I was not sure if this “100-year starship study” was an opportunity or the emergence of a new competitor to an already limited market. I hoped that this meeting would clarify that, but I remain uncertain.

When faced with confusing situations, I prepare by devising a number of divergent hypotheses. Then, as the evidence unfolds, I see which hypotheses seem most consistent with the evidence. From my over 30 years in NASA, I have witnessed the extremes of well-intentioned, honorable initiatives all the way to the other extreme of self-serving earmarks with good-old-boy networking. Accordingly, my ingoing hypotheses spanned those possibilities. Frankly, what I saw in the meeting reminded me of both those extremes, and I am still not sure how this study will transpire.

The emphasis on creating a new organization was loud and clear. Since the funding is constrained to support only the definition of an organization (no research, no education), and since other organizations already exist that are devoted to meeting the topic challenges (Tau Zero, British Interplanetary Society, The Planetary Society, and others with their niches, such as SETI) there is already a disconnect between the premise of this study and what is already happening in the world.

I must also be frank in my own self-serving biases. I started Tau Zero to chip away at the unknowns toward making interstellar flight an eventual reality, and with the help of dozens of others, we investigated the issues and options to arrive at our strategy of finding and supporting the pioneers, and using journalists and artists to tell their story along the way. Hence, I have a great deal of possessiveness regarding how interstellar flight should be organizationally pursued. In my mind and with most (not all) of my network, we are doing exactly what fits current realities. Adding another organization in the mix would be more disruptive than fruitful. Instead I would love to apply that $1M to the 30+ task proposals we have in our queue, and to finally fund the admin support we need to deal with the dozens of offers of volunteer help and permanently fix our damn, broken website (volunteers are wonderful, but can only do so much).

Regardless of how this DARPA/Ames study plays out, my cohorts and I will continue to pursue interstellar flight as we have – which includes forging collaborations with other complimentary organizations. That collaboration might now have to be accelerated to respond to any RFPs (Requests for Proposals) issued by Ames. At the meeting, Lou Friedman suggested forming some sort of “Interstellar Alliance” to respond, and I recently learned that such notions are shared by others who were not invited to the January meeting.

When DARPA/Ames does announce their next step, I hope that all of us can respond in a constructive way, to help shape this initiative into something for the greater good. Time will tell.

In the meantime, we at Tau Zero will continue our efforts. As stated in our November status report, we are beginning active fundraising this year and plan to shift from a donations-only model to a membership format. Also, the results of our November organization meeting – with more details about our priorities and how we operate – will be revealed here on Centauri Dreams when ready.


Good News from Both Sail Missions

Good fortune continues to smile on Japan’s IKAROS solar sail. First of all, we can point to the image at left, a small shot to be sure but an amazing one nonetheless. Emily Lakdawalla explains on the Planetary Society’s blog that IKAROS’ transmitter is not powerful, so that it took a full two weeks to transmit the image from the spacecraft to Earth, and at that, it’s just a thumbnail. But take a look — what you see is the sail itself and, in the background, Venus. Think about it: A solar sail has successfully made an interplanetary crossing.

Yesterday the JAXA controllers behind the IKAROS mission confirmed that its first six months of life have been all but flawless, and the mission has been extended to March of 2012. This includes the deployment of its 20-meter diagonal, 0.0075 milimeter thick polyimide sail — you may remember that was a bit of a nail-biter from here because I was trying to translate tweets in Japanese and follow the incoming imagery, which at one point seemed to show a snarled cable. But that turned out to be a mis-reading, and full sail deployment was subsequently confirmed.

Almost as significant as actual deployment, though, was the success of the attitude control system JAXA built into the sail, which includes liquid crystal devices that can be turned on and off to vary the reflectivity of the sail, and thus creates changes in photon pressure for maneuvering. During the subsequent cruise operations on the way to Venus, IKAROS collected information on space dust and was used for very long baseline interferometry observations of deep sky objects. Up next: A suite of navigational studies, including varying the sail’s angle to the Sun and changing trajectory, maneuvers that will model the sail’s response for future missions.

The success of IKAROS to this point bodes well for the next major Japanese sail attempt, which will involve a sail ten times the size of this one paired with an ion propulsion unit on a mission to Jupiter. Launch is currently planned for 2019 or 2020, and this article in Science notes that there are plans to operate in conjunction with US and European missions to conduct joint observations of the giant planet. IKAROS mission manager Osamu Mori is looking ahead: “In half a year, we accomplished all the mission objectives. Now we’ve set new objectives.”

Tracking NanoSail-D

Meanwhile, NASA’s NanoSail-D is 650 kilometers up, having unfurled its own 10-meter square sail. Unlike IKAROS, NanoSail-D’s mission is much closer to home, according to principal investigator Dean Alhorn (NASA MSFC):

“Our mission is to circle Earth and investigate the possibility of using solar sails as a tool to de-orbit old satellites and space junk,” explains Alhorn. “As the sail orbits our planet, it skims the top of our atmosphere and experiences aerodynamic drag. Eventually, this brings it down.”

Atmospheric drag will indeed return NanoSail-D to Earth, where it will burn up in the atmosphere in 70 to 120 days. What’s ahead are useful observations measuring the effect of sunlight on the sail. It’s possible that atmospheric drag will mask the effect, but just how the orbit decays will help to answer that question. NanoSail-D may be the harbinger for future ‘drag sails’ that de-orbit satellites after their missions are over, a necessity given the amount of orbital debris building up around the Earth. But a successful sail deployment also gives hope to those who believe a robust future lies ahead for solar sailing as a way to move payloads around the inner system.

For those with an interest in seeing NanoSail-D, bear in mind that the sail is quite reflective. If Venus appears to us at an apparent magnitude of -5 at its brightest and the full Moon hits magnitude -13, NanoSail-D should be able to show up at -10, a substantial target when sunlight glints off the sail. A new contest encourages amateur photographers and astronomers to submit photos of the sail to help NASA monitor the condition of the spacecraft. A series of cash prizes are offered, with contest rules and a submission link at the site.

Image: The NanoSail-D team after a deployment test. Credit: NASA/MSFC.

Remember, too, that the NanoSail-D mission dashboard is here, while you can track satellite flybys at the spaceweather.com site. The contest has already begun and will end when the spacecraft re-enters the atmosphere in three months or so. So have some fun with NanoSail-D while it’s up there, and let’s hope that both it and IKAROS are joined soon by another solar sail in the form of the Planetary Society’s LightSail-1. The solar sail era is coming upon us, slowly but surely, and the advantages of leaving propellant behind will one day make these technologies indispensable.


The Most Distant Galaxy Yet?

As we improve our ability to look back to the early universe, the changes we see in galaxies at this period compared to later eras are striking. A new study, using data from the Hubble Space Telescope’s Wide Field Planetary Camera 3 has been gathering infrared imagery back to a period as early as 480 million years after the Big Bang. What stands out in this work is the rate of star formation. In the period between 480 million to 650 million years after the Big Bang, the rate of star birth increased ten times. Garth Illingworth (UC-Santa Cruz) calls the result “…an astonishing increase in such a short period, just 1 percent of the current age of the universe.”

Moreover, the number of galaxies themselves showed a marked change. Says Illingworth:

“We’re getting back very close to the first galaxies, which we think formed around 200 to 300 million years after the Big Bang… Our previous searches had found 47 galaxies at somewhat later times when the universe was about 650 million years old. However, we could only find one galaxy candidate just 170 million years earlier. The universe was changing very quickly in a short amount of time.”

Among the galaxies studied is a candidate that appears to be the most distant galaxy ever observed, some 13.2 billion light years from Earth. The newly found galaxy has a redshift value (z) of 10.3, which places it just 480 million years after the birth of the universe. Remember that these redshifts are not Doppler shifts, which would be caused by the physical motion of the galaxies as they moved away from us in space. Rather, they are ‘cosmological’ redshifts. The photons being emitted from the galaxies are stretched as they travel through an expanding spacetime.

Image: The farthest and one of the very earliest galaxies ever seen in the universe appears as a faint red blob in this ultra-deep-field exposure taken with NASA’s Hubble Space Telescope. This is the deepest infrared image taken of the universe. Based on the object’s color, astronomers believe it is 13.2 billion light-years away. (Credit: NASA, ESA, G. Illingworth (University of California, Santa Cruz), R. Bouwens (University of California, Santa Cruz, and Leiden University), and the HUDF09 Team).

The concept goes back to the Dutch astronomer Willem de Sitter, who went to work on Einstein’s general theory of relativity not long after it was published and discovered that a stretching of space itself would cause light from more distant objects to appear redder than light from nearby objects. Hubble’s later observations could then be explained using de Sitter’s concept as indications that space and the photons in it are being stretched as the universe expands. David Weintraub tackles the subject in depth in his new book How Old Is the Universe (Princeton University Press, 2011:

Space that is empty of matter does not and never did exist. The distances between galaxies, galaxies being dense pockets of matter in an otherwise rarefied universe, are increasing with time but the galaxies themselves are not speeding through space. On the grandest scale (that is, ignoring small local motions that all galaxies have as they interact with nearby galaxies), galaxies are fixed in their locations in space. They do not move through space. Yet the distances between galaxies grow rapidly because the fabric of space in between the galaxies is continually being stretched, taffy-like, with the galaxies patiently riding along at fixed locations in the taffy.

Sorry for the digression, but I finished Weintraub’s book a few weeks back and have been paging back through it now and then with these concepts in mind. I’ll review the book soon. In any case, I hope the digression helps to put the new work in context, and points out how significant finding a galaxy with a z value of 10.3 is. The finding and the analysis of galaxies at slightly lower redshifts allows us to start building up a population of very early galaxies, and that should offer useful information re how galaxies form, particularly because the number of galaxies in this period increases so rapidly.

All of this work involves data originally collected from the Hubble Ultra Deep Field (a small region in the constellation Fornax) which were gathered during two four-day stretches in 2009 and 2010, focusing Hubble’s WFC3 infrared camera on a tiny part of the HUDF for a total exposure time of 87 hours. What also emerges from this work is that galaxies this faint and small (the Milky Way is 100 times larger) will need the resources of the James Webb Space Telescope for follow-up study beyond redshift 10.