Astronomers detect the first comet whose nucleus’ reversed its rotation

Astronomers using data collected by the orbiting Gehrels Swift and Hubble space telescopes now think the nucleus of a small comet reversed its rotation sometime in 2017, caused by the force of the material sublimated off its surface.

From the abstract of their paper [pdf]:

The rotations of cometary nuclei are known to change in response to outgassing torques. The nucleus of the Jupiter-family comet 41P/Tuttle–Giacobini–Kresak exhibited particularly dramatic rotational changes when near perihelion in 2017 April. Here, we use archival Hubble Space Telescope observations from 2017 December to study the postperihelion lightcurve of the nucleus and to assess the nucleus size.

From both Hubble photometry and nongravitational acceleration measurements, we find a diminutive nucleus with effective radius 500 ± 100 meters. Systematic optical variations are consistent with a two-peaked (i.e., rotationally symmetric) lightcurve with period 0.60 ± 0.01 days, substantially different from periods measured earlier in 2017. The spin of the nucleus likely reversed between perihelion in 2017 April and December as a result of the outgassing torque.

In plain English: the thrust of the material being thrown from the surface as the comet made its close approach to the Sun was sufficient to slow and then reverse the nucleus’s rotation. This process was helped by the relatively small size of the nucleus compared to the material being sublimated from it.

The data also suggests the nucleus was once much larger, and has been whittled down to its present small size as it made its multiple close fly-bys of the Sun during the past 1,500 years. Rather than break-up, as most comets do at some point as their nucleus gets smaller, this comet’s nucleus simply kept shrinking, to the point that the thrust of that material could change its rotation.

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All space stocks soar in anticipation of SpaceX’s impending IPO

It appears SpaceX’s upcoming initial public offering (IPO) of publicly-traded stocks, now anticipated to raise as much as $75 billion for the company, has caused stock investors to also pour their money into a whole range of space stocks, causing them all to soar in value.

Initially, it was expected that the IPO could raise $50 billion for the company, but the latest report indicates it could raise as much as $75 billion, with a valuation as high as $1.75 trillion. The colossal figures being thrown around on Wednesday have garnered excitement among investors for other space stocks that are already publicly traded.

Here were the top gainers in the session:

  • Firefly Aerospace: +19%
  • Intuitive Machines: +11%
  • AST SpaceMobile: +9%
  • EchoStar Corporation: 9%
  • Rocket Lab Corporation: +8%

The most recent indications suggest SpaceX will file the offering’s prospectus in the next week or so. If the predictions about it are correct, and SpaceX does raise $75 billion, it would then have on hand more than three times the cash that Congress normally budgets annually to NASA, with an ability to use that money far more effectively.

As I have been saying now for more than a year, the real space program for the United States is being run by SpaceX, not NASA. Expect SpaceX to outpace NASA in their parallel and complementary efforts to build a moonbase.

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Webb and Hubble take a look at Saturn

Saturn seen by Webb and Hubble

Astronomers using both the Hubble Space Telescope and the Webb Space Telescope have produced new complementary views of the ringed planet Saturn.

Those photographs are shown above, with Webb’s false-color infrared image to the left and Hubble’s optical image to the right. From the press release:

In the Webb image, a long-lived jet stream known as the “ribbon wave” meanders across the northern mid-latitudes, influenced by otherwise undetectable atmospheric waves. Just below that, a small spot represents a lingering remnant from the “Great Springtime Storm” of 2010 to 2012. Several other storms dotting the southern hemisphere of Saturn are visible in Webb’s image, as well. All these features are shaped by powerful winds and waves beneath the visible cloud deck, making Saturn a natural laboratory for studying fluid dynamics under extreme conditions.

…In Webb’s infrared image, the rings are extremely bright because they are made of highly reflective water ice. In both images, we’re seeing the sunlit face of the rings, a little less so in the Hubble image, hence the shadows visible underneath on the planet.

There are also subtle ring features such as spokes and structure in the B ring (the thick central region of the rings) that appear differently between the two observatories. The F ring, the outermost ring, looks thin and crisp in the Webb image, while it only slightly glows in the Hubble image.

The press release says little about the Hubble image, mostly because it shows little new by itself. It however is part of an on-going decade-long survey using Hubble to track Saturn’s changing weather patterns.

While both images are valuable, they also highlight our present limits in observing Saturn. Views from Earth can only see so much. It is like trying to watch a football game from ten miles away, with binoculars. And sadly, no mission is presently planned to return to Saturn.

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China launches two radar satellites

China today successfully placed two radar satellites into orbit, its Long March 2D rocket lifting off from its Taiyuan spaceport in north China.

China’s state-run press provided no information about where the rocket’s lower stages, using very toxic hypergolic fuels, crashed inside China.

The leaders in the 2026 launch race:

37 SpaceX
14 China
4 Rocket Lab
4 Russia

SpaceX continues to lead the entire world combined in total launches, as it did in both ’24 and ’25.

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Isar’s second launch attempt scrubbed due to abort at T-0 seconds

Proposed or active spaceports in North Europe
Proposed or active spaceports in North Europe

The German rocket startup Isar Aerospace was today forced to scrub its second attempt to launch its Spectrum rocket from Norway’s Andoya spaceport when the rocket aborted the launch at T-0 seconds.

The launch was then scrubbed for the day because the launch window was only 15 minutes long. An earlier hold due to a boat violating the range had used up most of the window, leaving no time to recycle the rocket to try again.

No word yet on when the company will try again. At the moment Isar is in the lead to be the first new European startup to get off the ground, though Rocket Factory Augsburg from Germany and PLD from Spain are not far behind. Isar’s first launch attempt in March 2025 had failed seconds after lift-off due to a loss of attitude control.

Andoya is also in the lead to be the first European spaceport to complete an orbital launch, though SaxaVord on the Shetland Islands hopes to see that Rocket Factory launch in the coming months.

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Triton: Neptune’s largest moon

The southern mid-latitudes of Neptune's moon Trident
Click for original image.

Triton

Today’s cool image begins a new tour I plan on doing over the next week or so of the few close-up photographs we have of Neptune and its moons, sent back by Voyager-2 when it did its close fly-by of this distant planet on August 25, 1989. That fly-by was almost 37 years ago, and it remains our only close look. While at the time it shined a quick flashlight of new knowledge on Neptune, its moons, and its ring system, we remain generally in the dark about what’s there, despite some good imagery produced in subsequent years by Hubble and some ground-based telescopes.

The image above, cropped and enhanced to post here, shows a portion of the southern mid-latitudes of Triton, Neptune’s largest moon, as Voyager-2 made its closest pass at a distance of about 25,000 miles. The photo to the right, cropped and reduced, shows a more global view to provide some context, with the box indicating the approximate area covered by the upper image. It was taken when Voyager-2 was on approach, at a distance of about 330,000 miles. The top picture captures several dozen black plumes that appear to vent material from below. From the caption:

The plumes originate at very dark spots generally a few miles in diameter and some are more than 100 miles long. The spots which clearly mark the source of the dark material may be vents where gas has erupted from beneath the surface and carried dark particles into Triton’s nitrogen atmosphere. Southwesterly winds then transported the erupted particles, which formed gradually thinning deposits to the northeast of most vents.

It is possible that the eruptions have been driven by seasonal heating of very shallow subsurface deposits of volatiles, and the winds transporting particles similarly may be seasonal winds. The polar terrain, upon which the dark streaks have been deposited, is a region of bright materials mottled with irregular, somewhat dark patches. The pattern of irregular patches suggests that they may correspond to lag deposits of moderately dark material that cap the bright ice over the polar terrain.

As we only have a few images of this planet, and those provided views of only about 40% of its surface, any theory that tries to explain the weird geology here is certain to be wrong to some degree.

More to come in the next few days. As much as we think we know, these pictures are going instead highlight how sparse that knowledge really is.

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Intuitive Machines wins $180.4 million new NASA lunar lander contract

Intuitive Machines' Nova-D lunar lander
Click for original.

The lunar lander startup Intuitive Machines announced yesterday that it has won its fifth contract from NASA, a $180.4 million deal to place its larger upgraded Nova-D lander near the Moon’s south pole.

The IM-5 mission will target Mons Malapert, a ridge near the Lunar South Pole that offers continuous Earth visibility, stable illumination conditions, and access to permanently shadowed regions. These characteristics make the site a compelling location for future communications, navigation, and surface infrastructure.

The artist’s rendering to the right shows this Nova-D lander. What stands out immediately is its low-slung appearance. Intuitive Machines’ smaller Nova-C lander was tall (see this image), with a high center of gravity. In its only two landing attempts on the Moon it tipped over both times after touchdown. It appears the company has finally recognized the issue and reworked this new lander to make it more stable after touchdown.

This contract award appears to be part of the accelerated program by NASA administrator Jared Isaacman to land 30 unmanned rovers on the moon in three years, beginning in 2027. Mons Malapert is a plateau that Intuitive Machines second lander tipped over on. It is also the landing site for Astrobotics’ Griffin lander, as well as a candidate landing site for the first Artemis manned missions.

Note the small rover on the right in the graphic. While the mission will carry seven NASA science instrument payloads, it will also carry this commercial rover, built by Honeybee Robotics, a subsidiary of Blue Origin. As the company states above, the lander on this mission also has additional available payload capacity for more commercial customers.

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Lunar Gateway dead as NASA announces major changes to its future space station, lunar, and Mars plans

Capitalism in space As part of the reshaping of NASA being pushed by NASA administrator Jared Isaacman, the agency today announced major changes to its future programs in low Earth orbit, on the Moon, and in exploring Mars. Video of these changes can be viewed here and here.

The Moon

NASA will now focus all work in its lunar program on getting to the surface of the Moon. Lunar Gateway is “paused,” though the language of NASA’s press release suggests more strongly that it is dead, with the agency already trying to figure out ways to “repurpose” its already built components. NASA will instead ask for proposals from private industry and its international Artemis partners to ramp up as soon as possible a phased program to establish the infrastructure on the Moon needed for the lunar base. This new focus begins with “up to 30 robotic landings in three years, starting in 2027,” and at least two manned landings per year beginning in 2028.

The graph below, presented during today’s announcement, shows the basic plan for the next few Artemis missions, which will act as the manned foundation for this entire surface-focused program. The overall program will build out the lunar base in three phases, first to test some basic infrastructure using these smaller lunar landers, second to begin establishing the base’s foundational components with intermittent manned missions, and third to begin long-term human occupancy.
» Read more

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Satellite repair startup Katalyst awards Arianespace and its Ariane-6 rocket a launch contract

The satellite repair startup Katalyst has chosen Arianespace’s Ariane-6 rocket to launch its first Nexus servicing satellite to geosynchronous orbit in late 2027, where it will demonstrate its capabilities by servicing a Space Force satellite.

The choice of Ariane-6 is intriguing, as it is much more expensive that a Falcon-9. Either the satellite is too heavy for the Falcon-9 (unlikely), or the Space Force for political reasons pressured Katalyst to use Europe’s rocket. It is also possible Katalyst choose Arianespace to stimulate interest in its robotic repair satellites within Europe, thus increasing its chances of winning contracts from there.

Either way, this is one of the few contracts outside of Amazon’s Leo constellation and European government launches that Ariane-6 has gotten. As I already mentioned, it costs more to use than other rockets, as it is entirely expendable. I think it is only surviving at this point because there are not a lot of options available. This is going to change, however, in the next decade as new rocket companies gear up to meet the demand.

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Russia launches the first 16 satellites in its own internet satellite constellation

In a rare unannounced launch, Russia yesterday placed the first 16 satellites in its proposed 700+ satellite Rassvet internet constellation into orbit, its Soyuz-2 rocket lifting off from its Plesetsk spaceport in northeast Russia in a polar orbit that dumped the rocket’s lower stages in the Arctic ocean.

The satellites are built by the Russian pseudo-company Bureau-1440, which hopes to have the entire constellation in orbit by 2035. Considering that this constellation is designed to compete with Starlink, its pace of launch is ridiculously low. SpaceX can generally launch 700 Starlink satellites in about a month, not ten years. By the time Russia gets this constellation in orbit it will be woefully obsolete.

The launch was originally supposed to occur several days earlier, but for reasons that were never explained never took place. This was not a classified military launch, but one that Russia wants to publicize as it struggles to compete with SpaceX and China in launching new satellite constellations. That Russia provided no details beforehand suggests that the increasingly successful use of drones by the Ukraine on Russian assets forced that secrecy.

The leaders in the 2026 launch race:

37 SpaceX
13 China
4 Rocket Lab
4 Russia

SpaceX continues to lead the entire world combined in total launches, as it did in both ’24 and ’25.

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Progress docks with ISS

A Russian astronaut successfully docked a Progress cargo capsule with ISS early today, using the manual TORU joystick system inside the station.

Sergey Kud-Sverchkov manually piloted the spacecraft during docking using the TORU (Telerobotically Operated Rendezvous System) control panel inside the space station’s Zvezda Service Module after one of the spacecraft’s two KURS automated rendezvous antennas failed to deploy after launch.

Normally each Progress docks autonomously, using the Kurs radar antennas to determine distance and location. With one antenna out Kud-Sverchkoy controlled the capsule remotely. This back-up system has been used successfully a number of times previously, but when it was first being tested on Mir in the 1990s one of those earlier tests resulted in a collision that almost destroyed Mir. It did damage one module badly enough that it leaked from then on, requiring that module to be sealed off for the rest of Mir’s life.

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Juno data suggests lightning on Jupiter is a hundred to a million times more powerful than lightning on Earth

The uncertainty of science: Using data from the orbiter Juno as it passed multiple times above a storm on Jupiter, scientists now believe lightning bolts on Jupiter could be a hundred to a million times more powerful than lightning bolts on Earth.

Juno made 12 passes over isolated storms during that period, and was close enough on four of them to measure microwave static from lightning. The flashes averaged three per second during these passes; on one flyover, Juno detected 206 separate pulses of microwave radiation. Of a total of 613 pulses measured, Wong calculated that the power ranged from about that of a lightning bolt on Earth to 100 or more times the power of an Earth bolt. Because he compared Earth lightning emissions at one radio wavelength to Jupiter lightning emissions at a different wavelength, there’s some uncertainty in the comparison, Wong cautioned. Based on one study of lightning radio emissions on Earth, Jupiter’s bolts could have been a million times more powerful than those on Earth.

Lots of uncertainty and assumptions in these conclusions, but they are not only not surprising, they fit earlier data collected before Juno.

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