Even as I’ve been writing about the need to map out regions just outside the Solar System, I’ve learned of a new study that finds (admittedly scant) evidence for a Planet 9 candidate. I won’t get into that one today but save it for the next post, as we need to dispose of the New Horizons news first. But it’s exciting that a region extending from the Kuiper Belt to the inner Oort is increasingly under investigation, and the very ‘walls’ of the plasma bubble within which our system resides are slowly becoming defined. And if we do find Planet 9 some time soon, imagine the focus that will bring to this region.
As to New Horizons, there are reasons for building spacecraft that last. The Voyagers may be nearing the end of their lives, but given that they were only thought to be operational for a scant five years, I’d say their 50-year credentials are proven. And because they had the ability to hang in there, they’ve become our first interstellar mission, still reporting data, indispensable. Now we can hope that New Horizons carries on that tradition, since so far it has proven equally robust and remains productive.
Image: This is Figure 1 from the paper we’ll be discussing today (citation below). Caption: The trajectories of the five spacecraft currently leaving the solar system: Pioneer 10 and 11 (orange and light green, respectively), Voyager 1 and 2 (gray and green, respectively), and New Horizons (NH, red) are shown projected onto the plane of the ecliptic, along with several planet orbits (black) and the direction of the flow of interstellar hydrogen atoms (purple arrows). The locations where great-circle scans of interplanetary medium (IPM) Lyα [a uniquely useful spectral line of hydrogen] were made with the NH Alice UV spectrograph are indicated (red), including the all-sky Lyα map described here, which was executed during 2023 September 2–11 at a distance from the Sun of 56.9 au. Credit: Gladstone et al.
To understand the image, we have to talk about ultraviolet Lyman-alpha (Lya) emissions, which happen when an electron in hydrogen transitions from the second energy level (n=2) down to the ground state (n=1). It is the transition that results in the production of a Lyman-alpha photon with a wavelength of about 121.6 nanometers. Since we’ve been talking about the interstellar medium lately, it’s helpful to know that photons in this far-ultraviolet part of the spectrum are absorbed and re-emitted by interstellar gas. They’re useful in the study of star-forming regions and molecular hydrogen clouds.
These emissions are at the heart of a new paper using data from New Horizons that has just appeared from the spacecraft’s team, under the guidance of Randy Gladstone, lead investigator and first author. Says Gladstone:
“Understanding the Lyman-alpha background helps shed light on nearby galactic structures and processes. This research suggests that hot interstellar gas bubbles like the one our solar system is embedded within may actually be regions of enhanced hydrogen gas emissions at a wavelength called Lyman alpha.”
So what we have in these Lyman-alpha emissions is a wavelength of ultraviolet light that is an outstanding tool for the study of the interstellar medium, not to mention our Solar System’s immediate surroundings within the Milky Way. The beauty of having New Horizons in the Kuiper Belt is that along the way to Pluto, the spacecraft was bankrolling Lya emissions with its ultraviolet spectrograph, charmingly dubbed Alice. Developed at SwRI, Alice was turned to the task of surveying Lya activity as the craft continued to travel ever farther from the Sun. One set of scans mapped 83% of the sky.
Image: The SwRI-led NASA New Horizons mission’s extensive observations of Lyman-alpha emissions have resulted in the first-ever map from the galaxy in Lyman-alpha light. This SwRI-developed Alice spectrograph map (in ecliptic coordinates, centered on the direction opposite the Sun) depicts the relatively uniform brightness of the Lyman-alpha background surrounding our heliosphere. The black dots represent approximately 90,000 known UV-bright stars in our galaxy. The north and south galactic poles are indicated (NGP & SGP, respectively), along with the flow direction of the interstellar medium through the solar system (both upstream and downstream). Credit: Courtesy of SwRI.
The method is about what you would assume: The New Horizons team could subtract the Lya activity from the Sun from the rest of the spectrographic data so as to get a read on the rest of the sky at the Lyman-alpha wavelength. What the team has found is a Lya sky about 10 times stronger than was expected from earlier estimates. And now we turn back to the issue of that hot bubble of gas – the Local Bubble – we talked about last time. 300 light years wide, the hot ionized plasma of the bubble was created by supernovae between 10 and 20 million years ago. The Sun resides within the Bubble along with low-density clouds of neutral hydrogen atoms, as we saw yesterday.
New Horizons has charted the emission of Lyman-alpha photons in the shell of the bubble, but the hydrogen ‘wall’ that has been theorized at the edge of the heliosphere, and the nearby cloud structures, show no correlation with the data. It is in the Local Interstellar Medium (LISM) background that the relatively bright and uniform signature of Lya is most apparent, evidently the result of hot, young stars within the Local Bubble shining on its interior walls. But as the authors note, this is currently just a conjecture. Further work from the doughty spacecraft may be in the cards. From the paper:
The NH Alice instrument has been used to obtain the first detailed all-sky map of Lyα emission observed from the outer solar system, where the Galactic and solar contributions to the observed brightness are comparable, and the solar contribution can be reasonably removed….A follow-up NH Alice all-sky Lyα map may be made in the future, if possible, and combining that map with this map could result in a considerable improvement in angular resolution. Finally, the maps presented here were obtained using the Alice spectrograph as a photometer, since its spectral resolution is too coarse to resolve the details of the Lyα line structure. However, there are instruments capable of resolving the Lyα line profile (e.g., J. T. Clarke et al. 1998; S. Hosseini & W. M. Harris 2020) which could possibly study this emission in more detail, and thus (even from Earth orbit) provide a new window on the LISM and H populations in the heliosphere.
Thus we learn something more about the boundary between our system and the interstellar medium in a map that should provide plenty of ground for new investigations at these wavelengths. And we’re reminded of the tenacity of well-built spacecraft and their continuing ability to return solid data well beyond their initial mission plan. Where and when the next interstellar craft gets built remains an open question, but for now New Horizons seems capable of a great deal more exploration.
The paper is Gladstone et al., “The Lyα Sky as Observed by New Horizons at 57 au,” The Astronomical Journal Vol. 169, No. 5 (25 April 2025), 275. Full text.
Let’s hope that the future value of these probes in exploration doesn’t fall prey to huge science funding cuts at NASA. NH was always on the edge of cancellation after the Pluto flyby, so any NASA cuts could end it, as well as other NASA-funded science. Congress needs to step up and prevent these cuts.
The way I see the modern NASA as leading the design of instruments and spacecraft. And leave the heavy lifting to other private companies like SpaceX. There are too many hanger-on’s and waste in NASA IMO.
Things like New Horizon is what NASA should be doing. What NASA should NOT be doing is running a space transportation company. Having NASA build and launch rockets is like the government being both an aircraft manufacturer and an airline. This latter makes absolutely no sense at all.
@Abelard
The analogy to civil aviation is not really valid. NASA is neither a manufacturer of space transportation (it is specified, and a contractor builds it to spec), nor a “spaceline” as it is not offering a service to anyone other than its own personnel (astronauts). I think of NASA JPL as more like a laboratory where instruments are designed and run. The human spaceflight is not that different, but they use a specialized transport system supporting the missions.
It would be better if there were a way to create useful transportation systems that could be mass-produced and sold to those needing that transport system, but that is like selling a railway rather than making the rail system infrastructure available for use.
It was somewhat laughable when the Space Shuttle was described as a “truck”, as it was a rather specialized and expensive piece of machinery. Expensive to manufacture, operate, and maintain. Not something with the features we associate with a truck.
Interestingly, Virgin Galactic and Blue Origin are both building their transportation system and being their own airline. Neither has positive ROI AFAIK.
Historically, airlines were started with surplus aircraft from WWI and WWII that could be reconfigured as passenger aircraft. There is no equivalent for spacecraft.
There are many people who think that the SLS should be canceled (but others disagree). JPL has done very well with designing and building various robotic probes and rovers. Why cancel that division. The ISS is a huge money pit, and has to be ended before the end of this decade.
While the commercial companies do build hardware, e.g. Boeing, and NASA has contracted out much more on their commercial programs, there is a problem with the business model. Ideally, commercial contracts should translate into usable hardware for commercial operations, e.g. like civil aviation. However, there is no good business for humans in space. It is all “Build it and they will come” hopes. AFAIK, the only viable space businesses are unmanned satellites, of which communicatons is expandng wth LEO swarms like Starlink. Others are arrivng. But orbital trips with/without hotel stays? The cost to access space will have to decrease by at least another order of magnitude or two from SpaceX lowered prices before they is more than a handful of passengers to take the trip. Space resources are not viable if they are to be returned to Earth rather than used in space.
Elon Musk has fantasies of a self-supportng colony on Mars. Bezos similarly with O’Neill-inspired space colonies. These may all be possible, eventually, but not in the timeframe either hopes to achieve. If there was a 2nd Earth without an advanced species to travel to in our system, then colonization might make sense. But since that is not the case, humans have to be carefully protected in space, with considable costs of life support provided from Earth.
really don’t want to see a few oligarchs trying to fulfill their space colonization dreams supported by impoverishing people on Earth to pay for them. This is Heinlein D D Harriman Libertarian stuff. It sounds great until you realize the realities. Greg Benford wrote a similar story about such a driven businessman who managed to reach another star despite Earth authorities trying to prevent him. It is so much Ayn Rand’s “Galt’s Gulch” in nature.
To launch a generation ship is a venture for a greatly expanded global economy, probably centuries in the future. However, there are increasing signs that economies cannot keep growing and that we may already have exceeded the Earth’s ability to support our current economies. Maybe this is all a temporary bottleneck until we have learned to use only renewable energy (however delivered) and recycled all our wastes, and intelligent machines have increased productivity and wealth creation whose output is widely shared, rather than rewarding the few and immiserating the rest of us. Reality however, suggests otherwise and that we are reaching the limits to growth, and the transition to post-industrial economies reduces growth to a very low percentages, pushing out the time to reach the size needed for a starship mission. Maybe we get advances to allow FTL starships like those in Star Wars and humans can then easily colonize the galaxy. At this time, this seems like a fantasy hoping for a “new physics miracle”.
Bottom line. To create a commercial space operation that supports human colonization of space that supports some expanding opportunities for economic growth, requires a number of technological advances that we can see need to be solved but cannot with the technology we have, and the design of the economy we have.
Alex
‘really don’t want to see a few oligarchs trying to fulfill their space colonization dreams supported by impoverishing people on Earth to pay for them.’
I don’t see this, I mean Starship will be a dual recyclable system, it can throw a lot of mass into space, ferry people about and deliver satellite constellations for communications. The last people i trust is the government, you see this in the Uk and the USA !
@Michael
Did you miss that Bezos’ flights were paid for by keeping his AMZN workers stressed, underpaid, and blocking unionization?
Or perhaps Musk, currently taking a chainsaw to the federal government while also getting contracts moved to SpaceX, like the FAA’s ATC system and the US broadband expansion? [And let’s not forget he trashed Twitter and treated the employees like dirt.]
If you work for a corrupt employer you can always leave and go to another company, but imagine working for a corrupt government and you have no escape. Twitter still works after removing I think around 80 % of the staff, so they were dead wood anyway. As for spacex if they can deliver a cheaper service good for them.
Hi Paul
Yes it’s great this mission is still producing some amazing science results.
I will be looking forward to your next post
Thanks Edwin
Yeah, Alex, I substantially agree that they’re too far out over their skis in terms of many things, including in particular settling Mars.
SpaceX may have the transport system in the Starship to actually – get – there much more economically than was conceivable before as a practical matter.
But it’s all the untested infrastructure necessary to maintain a going settlement – where everything has to work together robustly and continuously for people just to be able to breathe, not suffer the effects of depressurization, not freeze, be able to drink potable water, and eat on a sustained 24.6/7/687 basis (or however those units work up there).
Any one of those systems fails, along with its particular redundant systems, and they’re, uh . . . screwed.
And when they talk about staying within safe radiation exposure levels by not engaging in sundry activities for too long and further then refer to that village in Iran (Talesh Mahalleh in Ramsar, Iran, thank you, Grok) where people live at a high exposure level, I just think: “They really, really don’t have a truly effective strategy for radiation yet.”
If task-oriented people regularly have to break off tasks before they’ve completed them, that’s not going to tend to work on a sol-to-sol basis. Critical tasks – including fixing robots that do the underlying tasks – either aren’t going to get done (contributing to the risk of cascade failure of necessary systems) or people are going to fairly routinely exceed their cumulative radiation exposure limits (including from the trip over).
And, most of all, we still don’t yet – know – how the human organism is going to fare at 0.38 g on a – permanent – basis. Maybe humans will adapt and evolve over the generations, assuming they’re able to successfully reproduce along the way. But we have no idea how smooth any such transition to next-gen native Martians will be.
To me – although this tends to be fighting words for Mars advocates, who don’t want to see the resources diverted – we really, really need to test much of the infrastructure first on the Moon, where they’re only a couple of days or so free fall away (once back in space) from safety. Different conditions to be sure, but there’s enough of an overlap to use the Moon as a test bed for much of the infrastrucure. To paraphrase Frank, if you can – reliably – grow crops there . . . .
And also get more data on how the human organism fares for a prolonged time at low gravity as opposed to microgravity, at least at 0.16 g.
I would get the technology readiness level up on a number of infrastructure technologies and further learn about how humans do in low gravity before even thinking of staking out a timeline for – settling as opposed to exploring – Mars.
And, in that vein, there’s plenty of exploration to do first on Mars to (a) fully rule out the possibility of microbial subsurface life there; and (b) otherwise prepare for long term bases or settlements by, e.g., identifying specific resources at various locations and also testing infrastructure technology without risking larger populations.
But, there’s “go fever” to go there now, well, in the political winds of the moment anyway, so I’ve tasked myself as we’ve discussed to finishing up that constitutional project. Which I need to finish up “at some point” anyway, given the vicissitudes of life.
Per my new friend Grok, astrobiology Professor Cockell of the University of Edinburgh “emphasizes the need for future Martian societies to develop their own constitutions, arguing against pre-drafting by Earth-based entities.” (quoting Grok)
I can fully sympathize with that sentiment as I’ve been very concerned about Terran interests – of sundry different stripes – trying to dictate to Martian settlers what their constitution should include.
But the still-continuing work that I’ve done spread over the past decade plus further reinforces to me that it’s something that the ultimate settlers, not folks staying here, should do some advance consideration of. “It’s a fair undertaking,” once you delve into the nuts and bolts of it. The working draft on my proposed constitution itself – not including also the Federalist Paper type explainer essays that I’m currently working through – weighs in at the moment at about 22,500 words. Long for a strictly national constitution but this constitution is for a standalone city-state exercising what would be national, state and local authority in the Terran context. So it’s more akin to a U.S. state constitution in terms of length, although it in broad brush follows the format of the U.S. federal constitution.
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If you really want to see someone take the billionaire buddies to task on space policy, including specifically as to Mars, check out this piece by Robert Zubrin:
https://unherd.com/2025/04/the-flaws-in-musks-mars-mission/
I note that it was published on April First, but I don’t think any of it was tongue in cheek. That the criticism is coming from the perhaps top proponent of human settlement of Mars (along with also Buzz Aldrin), who otherwise might be expected to cheer on Martian go fever, is a stark contrast.
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As we’ve discussed before, we really need to get out of this loop of resetting our space exploration goals every 4 to 8 years with the changeover in administrations. Planning needs of course needs to be much more long term than that.
Can’t imagine building a Gothic cathedral that way back in the day.
Not without perhaps encountering surrealist architecture a few centuries early.
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Hey, I’m actually finding AI – specifically Grok so far, on the fly – helpful.
I’m impressed with both how quickly it comes back with a detailed answer and how on point that answer then is, including indicating precisely why a more precise answer was not available in one case. Along with, on Grok as an X subscriber IIRC, links to supporting and further material.
With none of that sophmoric handwavium inserted like in those Grok news summary pieces I referred to the last time we discussed AI.
Which by the way aren’t there anymore on my X feed. Was it maybe my critique that sent them back to the drawing board? lol
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Now, as to these UV Lyman-alpha emissions, if I understand correctly (always a dicey prospect) we’re apparently talking about photons possibly shining on the interior walls of the Local Bubble in which, inter alia, our solar system resides.
That has such a warm, cozy feel to it, like the light of a fire reflecting off the cabin walls.
Hopefully, Alice has a long future still to go.