Tag: astronomy

A galaxy as seen by Hubble and Webb

9:23 am

A galaxy seen by Hubble and Webb
Click for original image.

Cool image time. The picture to the right, cropped and reduced to post here, was taken on March 20, 2026 in a coordinated observations by both the Hubble and Webb space telescopes.

This March 20, 2026, image of Messier 64, or the Black Eye Galaxy, is a composite view from NASA’s Hubble Space Telescope and James Webb Space Telescope. It shows Messier 64 captured at near- and mid-infrared wavelengths by Webb, while Hubble’s image shows the galaxy in ultraviolet, visible, and near-infrared light.

Messier 64 is characterized by its bizarre internal motion. The gas in the outer regions of this spiral galaxy is rotating in the opposite direction from the gas and stars in its inner regions. This strange behavior may be the result of a merger between M64 and a satellite galaxy over a billion years ago.

The red in this image is dust, as the galaxy gets its nickname from the dark streak that wraps around its nucleus on its left side. In optical that streak is dark. Here Webb’s infrared view sees it in false color red.

READERS: It appears that it is a very slow news day today. Other than SpaceX’s IPO, which is on-going and too soon to post any reports, I can so far find nothing much of great significance on which to report.

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Evidence of supernova remnant near the center of the Milky Way?

10:21 am

Supernova remnant near the Milky Way's center
Click for original image.

Using two X-ray space telescopes, astronomers now think they have detected evidence of a supernova remnant very close to the center of the Milky Way.

You can read their paper here [pdf]. The image to the right is a composite of optical (the stars), radio (the red nebula), and Chanda’s X-ray data (the blue nebula). From the press release:

The evidence for the new supernova remnant, located about 26,000 light-years from Earth, comes from X-ray data from Chandra and XMM-Newton. The X-ray data reveals a “blob” of X-ray emission [indicated by blue] that may come from the remains of a massive star that self-destructed as a supernova, buried within the larger cloud of expanding gas.

The location of this suspected supernova remnant in the image is [that blue region]. It is in bubble of gas [the surrounding larger and smaller red objects] that has had electrons stripped away from hydrogen — called an “H II region” — surrounding a massive, young star. If this is indeed a supernova remnant, then it is expanding at about two million miles per hour and is at least about 1,700 years old.

,..The long filaments seen in the radio image are caused by energetic particles travelling along magnetic fields that are mostly directed perpendicular to the plane of the galaxy.

According to the paper, this supernova remnant is found on the western edge of a vast energized gas cloud called the Central Molecular Zone (CMZ), 1,600 to 1,900 light years across, that spans the Milky Way’s center. The features seen in the image above are part of a feature on the CMZ’s western edge called Sagittarius C, which apparently has not been studied as much as other parts of the CMZ.

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Astronomers find another quasar in the early universe that really shouldn’t be there

9:28 am

The uncertainty of science: Using archival data from the WISE space telescope, astronomers have now identified another unexpected quasar in the early universe, only 850 million years after the Big Bang, that also flickers in several wavelengths.

The quasar’s flicker enabled the researchers to determine that, surprisingly, the ancient quasar’s whirlpool of gas and dust, known as an accretion disk, resembled a flat pancake, similar in shape to that of more modern-day quasars.

Their findings add to a longstanding mystery in cosmology: Why do supermassive black holes exist so early in the universe’s history? Physicists have assumed that a flat accretion disk reflects a relatively mature black hole that is in a calm and stable state. Black holes that are just starting to form, like those in the very early universe, should be more unsettled systems, with accretion disks that appear more puffy and chaotic.

The flat accretion disk around this very early quasar heightens the mystery of how supermassive black holes can grow and mature in a very short amount of cosmic time.

They estimate the quasar energy output is equivalent to about 12 trillion suns. Its flickering, ranging about 20% in power, makes it the first such flickering quasar found this early in time. Such early quasars however are not unique. Astronomers have found about 200, all of which should not exist, based upon present Big Bang cosmology. There simply hasn’t been enough time for them to evolve, based on present theories of galactic formation.

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Astronomers measure weight of supermassive black hole 10 billion light years away

9:13 am

In a new record for the farthest measurement yet achieved (10 billion light years away), astronomers have now used the Webb Space Telescope obtain a reasonably accurate measurement of the mass of supermassive black hole in the early universe, estimated to be six billion times the mass of our Sun.

The stars orbiting Sag A*
The stars orbiting Sag A* at the center of our own
galaxy, the Milky Way. Click for original image.

The black hole’s mass is about 6 billion times that of the sun, and is being observed at a time when the universe was only about 3 billion years old, about a quarter of its current age, offering unprecedented details into black holes in the early universe.

To find this, the team used data from NASA’s James Webb Space Telescope to track the motion of stars orbiting around the otherwise invisible black hole to measure its mass. Though the technique – known as stellar dynamics – has been used to measure dormant black holes in galaxies much closer to Earth, this is the first time it has been used to weigh one located such a great (cosmological) distance away.

For comparison, the Milky Way’s central super-massive black hole, Sagittarius A* (pronounced “A-star”), has been estimated at four million solar masses, using this same technique. The graphic to the right shows the various stars orbiting Sagittarius A* that have been tracked now for several decades in the infrared. As their orbits are refined, astronomers can use those orbits to determine the mass of the central object.

The scientists have now been able to do the same with this galaxy ten billion light years away. These observations however are certainly preliminary, and will be refined in the coming decades as more data is obtained.

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The wind speeds on seven exoplanets also suggest presence of magnetic fields

10:54 am

Astronomers using two different ground-based telescopes were able to measure the wind speeds on seven different gas giant exoplanets, and found the speeds also suggested the presence of planetary magnetic fields, the first time such magnetic fields have been deduced on an exoplanet.

In the study, the researchers investigated the wind speeds on seven exoplanets orbiting different stars. These are gas giants similar to Jupiter, which are very close to their star. Elspeth Lee explains: “The rotation of the planets was synchronized with their orbits by the tidal forces of the parent star. Just as we only ever see one side of the moon, these planets always have one side facing the star. Thus, a glowing hot day side and a permanently dark night side have formed on the planets. The extreme temperature differences in turn lead to the generation of extremely strong winds.”

…The research team was able to show that wind speeds of around 7,200 km/h to over 25,000 km/h prevail on the exoplanets. For comparison: the fastest winds measured on Jupiter reach speeds of around 1,500 km/h.

The data showed that the hotter the planet, the slower the wind, the opposite of what was expected. The scientists believe that each planet’s magnetic field is acting to brake the winds, with the hotter planets likely having more powerful fields.

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Webb detects methane being released by interstellar comet 3I/Atlas

9:21 am

Comet 3I/Atlas's methane as seen by Webb
Comet 3I/Atlas’s methane as seen by Webb.
Click for full image.

Using the Webb Space Telescope, astronomers have now detected methane in the cloud of material released by the interstellar comet 3I/Atlas as it zipped past the Sun last fall.

The observations were taken using Webb’s MIRI (Mid-Infrared Instrument) on two separate dates as the comet traveled back out of our solar system after whipping around the Sun (post-perihelion). The first observation occurred Dec. 15 to 16, when the comet was about 205 million miles from the Sun. This was followed by a second observation Dec. 27, when the comet was about 236 million miles from the Sun.

For the first time on an interstellar visitor, Webb directly detected methane gas. Methane is highly volatile, meaning it sublimates from solid ice into a gas very easily. Its delayed appearance in comet 3I/ATLAS suggests it was buried below the comet’s top surface layer and protected from sublimation until heat from the comet’s close pass to the Sun reached deeper parts of the icy subsurface. The amount of methane relative to water found is surprisingly high, with few similar analogs in our own solar system.

Webb’s observations also confirmed that comet 3I/ATLAS remains unusually rich in carbon dioxide, releasing far more carbon dioxide relative to water when compared to typical solar system comets.

You can read their peer-reviewed paper here [pdf]. This new data confirms that Comet 3I/Atlas is not from our solar system, as its make-up is sufficiently different from solar system comets to show this. It also gives us a hint as to the solar system it came from. At the same time, the comet’s behavior is remarkably similar to solar system comets, suggesting our solar system evolved much like others.

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An active galaxy peered at by Webb in the infrared

10:57 am

M77 as seen by Webb
Click for original image.

Cool image time! The false-color infrared image to the right, cropped and reduced to post here, was taken by the Webb Space Telescope as part of a research of “massive, nearby, star-forming galaxies.” It shows Messier 77 (M77), a barred spiral galaxy located 45 million light-years away.

What makes the image cool are the eight diffraction spikes, which are an artifact of Webb and its camera.

Called diffraction spikes, they are created because the intense light from the unresolved AGN is bent (“diffracted”) very slightly at the edges of Webb’s hexagonal mirror panels and around one of the struts that hold up its secondary mirror. This distinctive six-plus-two-pointed pattern is the same for any image taken by Webb. For diffraction spikes to appear, the light source has to be very bright and very concentrated, so they’re most often seen on stars. But in some galaxies, as here, the nucleus is bright and compact enough to make diffraction spikes appear as well.

In the case of M77, the nucleus is especially bright.

At the heart of M77 is a compact region filled with hot gas that handily outshines the rest of the galaxy put together, even overcoming the light-gathering capacity of Webb’s cameras. This is an active galactic nucleus (AGN), and it’s powered by M77’s central supermassive black hole, which is eight million times as massive as our Sun. Gas in the galaxy’s central regions is pulled by the strong gravity into a tight and rapid orbit around the black hole, where it crashes together and heats up, releasing tremendous amounts of radiation.

The result is this very cool image that also highlights a great deal about galaxies and their evolution.

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Using Webb astronomers think they have detected daily weather changes on exoplanet

9:27 am

The data confirming explanet's existence from 2014 paper
Figure 1 from the 2014 paper confirming exoplanet’s existence.

Using the Webb Space Telescope’s infrared spectroscopic data astronomers believe they have detected the daily weather changes on exoplanet WASP-94A b, a hot gas giant about half the mass of Jupiter that orbits its star every four days.

Observations revealed that mornings and evenings on WASP-94A b have extremely different weather patterns: Mornings are riddled with clouds made of magnesium silicate, a common mineral found in rocks, while the evening has clear skies.

The star itself is about 700 light years away, and is known to have two exoplanets circling it.

The scientists proposed two explanations for their data. Either strong winds are clearing the air in the evening, or the clouds are the equivalent of morning fog on Earth that naturally dissipates as the day brightens.

Note that there is great uncertainty with these results, as we are only getting a very limited view from 700 light years away. In a sense, our knowledge of these exoplanets is comparable to what we knew of our own solar system’s planets prior to the space age. Once we got our first close looks at the planets almost everything we thought we knew beforehand turned out to be either wrong or misguided, due to the limited nature of the data.

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An amoeba in space more than a light year in size

12:59 pm

An amoeba in space more than a light year in size
Click for original image.

Time for another cool image. The picture to the right, cropped and reduced to post here, was released today by the science team of the 8.1 meter Gemini North telescope on Mauna Kea in Hawaii. It provides a close-up view of the central blob that forms NGC 1514, a planetary nebula located about 1,500 light years away and nicknamed the Crystal Ball Nebula by Gemini’s PR team.

They might think it resembles a crystal ball, but to my eye this is an amoeba undulating in weightlessness.

Planetary nebulae form when a low- or intermediate-mass star ejects its outer layers near the end of its life, forming a somewhat spherical cloud of gas. They typically have smoother, spherical shapes, making the Crystal Ball Nebula unique for its bumpy shells of gas. As the central star casts away this gas, its inner core is exposed. Radiation from the core energizes the gas, giving it a scorching temperature and chromatic glow. The Crystal Ball Nebula, for example, has an estimated temperature of 15,000 K.

…While it may appear in this image as if there is a single shining light source at the heart of the Crystal Ball Nebula, as Herschel saw, it actually contains two stars. These two stars orbit each other with a period of around nine years — the longest known for any binary pair within a planetary nebula. Scientists believe that one of these stars, which was once several times more massive than our Sun, released its outer layers while in the throes of death. As the progenitor star and its binary companion orbit each other, they mold the expanding shell of gas with their strong, asymmetrical winds, forming the lumpy layers we see today.

The analogy I like to use for this process is that of a blender. The two stars act like the blender’s blades, mixing the outflowing gas from the stars into these spectacular shapes.

The Webb Space Telescope took its own infrared image of this nebula, and showed that its is surrounded by two larger rings of material, also expanding outward.

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Psyche approaches Mars

8:30 am

Mars as seen by Psyche
Click for original image.

The asteroid probe Psyche is now approaching Mars for a May 15, 2026 fly-by that will slingshot it out to the metal asteroid Psyche in 2029.

The image to the right, cropped and expanded to post here, was taken on May 3, 2026 when the spacecraft was still about three million miles away.

The observation was acquired by the multispectral imager instrument’s panchromatic or broadband filter, with an exposure time of just 2 milliseconds. Even with this very short exposure time, the crescent is extremely bright and parts of the image are oversaturated. The light seen here is sunlight reflected off the surface of Mars and also scattered by dust particles in its atmosphere. Because the quantity of dust in the atmosphere can vary rapidly over time, the anticipated brightness of the crescent was hard to predict before this early image was acquired.

The dustiness of Mars leads to sunlight being scattered by its atmosphere, making the crescent appear to extend farther around the planet than if it had no atmosphere (as with our Moon).Of note, on the right side of the extended crescent, there appears to be a gap, which coincides with the planet’s icy north polar cap. The cap is currently in winter and mission specialists hypothesize that seasonal clouds and hazes may be forming in that region, possibly blocking the atmospheric dust’s ability to scatter sunlight like it does elsewhere around the planet.

Though the spacecraft had had a thruster issue last year, all seems well at this time.

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Katalyst completes final ground testing of its Swift rescue spacecraft

8:01 am

Katalyst's proposed Swift rescue mission
Katalyst’s proposed Swift rescue mission.
Click for original image.

The orbital servicing startup Katalyst has now successfully completed the final ground testing of its Swift rescue spacecraft, dubbed LINK, that it hopes will be able to catch the Gehrels-Swift Telescope and raise its orbit, thus saving the telescope.

During vibration testing at NASA Goddard, engineers mimicked the shaking the spacecraft will experience during its launch from a Northrop Grumman Pegasus rocket. In the footsteps of Swift itself and NASA’s upcoming Nancy Grace Roman Space Telescope, the Katalyst team also used NASA Goddard’s Space Environment Simulator for thermal vacuum testing.

Once the air was pumped out of this 27-foot-wide chamber, LINK experienced space-like hot and cold temperature extremes. The team also practiced firing the satellite’s three xenon-powered ion thrusters and deployed one of the arms.

After some more testing in Arizona, the spacecraft will be integrated in June onto Northrop Grumman’s Pegasus rocket — the last one in its inventory — and launched later that month.

Katalyst has never done this before. It was preparing LINK as a demo mission when NASA requested bids for saving Swift. It proposed reconfiguring LINK for that purpose, and won the contract in September 2025, only eight months ago.

If this mission succeeds it will be a big feather in Katalyst’s cap.

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New data says interstellar Comet 3I/Atlas IS different from comets in our solar system

10:42 am

Using spectroscopic data from the ALMA telescope in Chile, astronomers have determined that interstellar comet 3I/Atlas is enriched in deuterium (sometimes called “heavy water”), with quantities as much as 30 times that found in ordinary solar system comets and 40 times that found in Earth’s oceans.

You can read the peer-reviewed paper here. From its abstract:

3I/ATLAS shows a deuterium enrichment exceeding Earth’s ocean value by more than a factor of about 40 and typical Solar System cometary values by more than a factor of about 30. The elevated deuterium enrichment points to water that formed under colder, less irradiated conditions and from less thermally processed material, consistent with an origin in a planetary system that formed under different physical and chemical conditions than our own.

In other words, the conditions in which Comet 3I/Atlas’ solar system formed were very different from those when our own solar system formed.

This conclusion is wonderful, but it raises more questions than it answers. Since we do not know how old the comet is, nor do we really know where it came from, there is little else we can glean from this result, other than it proves the conditions when solar systems form can vary widely.

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Hubble looks at the Trifid Nebula again

9:59 am

Trifid Nebula as seen by Hubble
Click for original image.

Cool image time! The picture to the right, cropped to post here, was taken by the Hubble Space Telescope and released today. It shows a small section of the Trifid Nebula, located about 5,000 light years away.

This location has been imaged numerous times in the past by Hubble. The area shown illustrates some fundamental aspects of stellar and nebula formation. The dark area in the lower right is a thick dust cloud. Several energetic O and B supermassive stars are out of view at the top. The radiation from these stars (indicated by the blue), is hitting that dust cloud and literally destroying it. It appears that the foreground “horn” exists because a larger object is blocking the radiation, allowing dust to survive in the background.

I have no explanation for the background “horn”.

This new image was taken in parallel with an image of the entire Trifid Nebula, taken by the new Rubin Telescope in Chile. Though Rubin cannot see with the same resolution as Hubble, its image is quite worthwhile viewing.

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Final ground testing begins of Katalyst’s Swift rescue spacecraft

5:46 am

Katalyst's proposed Swift rescue mission
Katalyst’s proposed Swift rescue mission.
Click for original image.

Only seven months after NASA awarded the satellite repair startup Katalyst the contract to save the Gehrels-Swift space telescope, the company has delivered the completed LINK spacecraft to the Goddard Space Flight Center in Maryland for final ground testing.

Katalyst will move forward with LINK’s vibration and thermal tests using NASA Goddard’s in-house facilities in the coming weeks before installation into Northrop Grumman’s Pegasus rocket at the agency’s Wallops Flight Facility in Virginia.

Gehrels-Swift has been one of NASA’s most productive space telescopes. Unfortunately its orbit is decaying and if nothing is done to raise that orbit it will burn up in the atmosphere in 2029 or so. To extend this timeline engineers have stopped almost all science work in February.

Katalyst hopes to launch LINK as soon as later this year. It was able to get it built so quickly because it was already under construction as the company’s first demo of its repair technology. When NASA put out a bid for boosting Swift, the company shifted gears and reconfigured LINK for this mission.

If successfully, the achievement will be a major coup for this startup.

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DESI telescope completes its nominal mission, mapping more than 47 million galaxies

9:56 am

DESI map
Click for original image.

The Dark Energy Spectroscopic Instrument (DESI) on the Mayall 4-meter telescope at Kitt Peak in Arizona, in Arizona has now completed its initial five-year nominal mission, mapping more than 47 million galaxies to produce a rough 3D map of the universe.

By comparing how galaxies clustered in the past with their distribution today, researchers can trace dark energy’s influence over 11 billion years of cosmic history. Surprising results using DESI’s first three years of data hinted that dark energy, once thought to be a “cosmological constant,” might be evolving over time. With the full set of five years of data, researchers will have significantly more information to test whether that hint disappears or grows. If confirmed, it would mark a major shift in how we think about our Universe and its potential fate, which hinges on the balance between matter and dark energy.

The image to the right shows the map, with the blank areas to the left and right regions blocked by the Milky Way.

DESI will continue mapping for at least another three years, refining its data. I suspect when scientists begin analyzing this information they will find there are more than one way to interpret it.

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The new Rubin telescope discovers over 11,000 new asteroids in first observations

11:07 am

Rubin's first asteroid discoveries
Click for full animation.

The new Rubin Observatory, a ground-based telescope in Chile, has discovered over 11,000 new asteroids in its first preliminary observations, with most in the main asteroid belt but a large number in the Kuiper Belt beyond Neptune and 33 previously unknown near-Earth asteroids.

The graphic to the right, annotated by me to post here, shows all of Rubin’s asteroid detections in light blue.

The submission to MPC [Minor Planet Center] comprises approximately one million observations, taken over the span of a month and a half, of over 11,000 new asteroids and more than 80,000 already known asteroids, including some that had previously been observed but were later “lost” because their orbits were too uncertain to predict their future locations. You can interact with all of Rubin’s asteroid discoveries in the Rubin Orbitviewer, which uses real data to provide an intuitive way to explore the structure of our cosmic backyard in three dimensions and in real time. Also, visit the Rubin Asteroid Discoveries Dashboard to learn about the new objects Rubin has uncovered.

…Among the newly identified objects are 33 previously unknown near-Earth objects (NEOs), which are small asteroids and comets whose closest approach to the Sun is less than 1.3 times the distance between Earth and the Sun. None of the newly discovered NEOs pose a threat to Earth, and the largest is about 500 meters wide.

Astronomers predict that Rubin will eventually find 90,000 new near-Earth objects, with some expected to pose a risk of hitting the Earth. It does this by repeatedly surveying the southern sky with its large mirror, then identifying new objects with its sophisticated software.

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A soft barred galaxy with an active nucleus

9:56 am

A barred galaxy with an active galactic nucleus
Click for original image.

Cool image time! The picture to the right, cropped, reduced, and sharpened to post here, was taken by the Hubble Space Telescope as part of two different surveys aimed at studying galaxies with what scientists call active galactic nuclei.

IC 486 lies right on the edge of the constellation Gemini (the Twins), around 380 million light-years from Earth. Classified as a barred spiral galaxy, it features a bright central bar-shaped structure from which its spiral arms unfurl, wrapping around the core in a smooth, almost ring-like pattern.

…At the galaxy’s center a noticeable white glow outshines the starlight around it. This is light given off by IC 486’s active galactic nucleus (AGN), powered by a supermassive black hole more than 100 million times the mass of the Sun. Every sufficiently large galaxy hosts a supermassive black hole at its center, but some of these black holes are particularly ravenous, marshaling vast amounts of gas and dust into swirling accretion discs from which they feed. The intense heat generated by the orbiting disc of material generates intense radiation up to and including X-rays, which can outshine the entire rest of the galaxy. In these cases, the galaxy is known as an active galaxy, with an AGN at its center.

For comparison, the relatively inactive supermassive black hole at the center of the Milky Way has a mass of about four million Suns, considerably smaller than IC 486’s. Why one is active and the other not however is not yet truly understood, though their different masses might provide part of the explanation.

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Changes to the Crab Nebula after a quarter century

9:44 am

The Crab Nebula, changes after a quarter century
For original images go here and here.

Using the Hubble Space Telescope, astronomers have obtained a new high resolution image of the Crab Nebula, and by comparing it with earlier Hubble images taken in 1999/2000 have been able to track the continuing expansion and evolution of this supernova remnant over a period now covering almost a quarter century.

The supernova itself became visible on Earth in 1054, though it actually erupted about 6,500 years earlier, as the Crab Nebula is 6,500 light years away. In the 25 years Hubble has been tracking the remnant’s expansion astronomers estimate it is expanding at about 3.4 million miles per hour.

[William Blair of Johns Hopkins University] noted that filaments around the periphery of the nebula appear to have moved more compared to those in the center, and that rather than stretching out over time, they appear to have simply moved outward. This is due to the nature of the Crab as a pulsar wind nebula powered by synchrotron radiation, which is created by the interaction between the pulsar’s magnetic field and the nebula’s material. In other well-known supernova remnants, the expansion is instead driven by shockwaves from the initial explosion, eroding surrounding shells of gas that the dying star previously cast off.

The new, higher-resolution Hubble observations are also providing additional insights into the 3D structure of the Crab Nebula, which can be difficult to determine from a 2D image, Blair said. Shadows of some of the filaments can be seen cast onto the haze of synchrotron radiation in the nebula’s interior. Counterintuitively, some of the brighter filaments in the latest Hubble images show no shadows, indicating they must be located on the far side of the nebula.

A movie showing the changes between these two images can be seen here. It is worth your while to take a look. These optical images will be further enhanced as the Webb Space Telescope gathers infrared data.

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Scientists compile catalog of the 69 known rocky exoplanets in the habitable zone

12:49 pm

Graph of the 45 most habitable known exoplanets
Credit: Gillis Lowry / Pablo Carlos Budassi.
Click for original at full resolution.

Scientists reviewing the more than 6,000 exoplanets so far discovered have now compiled a detailed catalog describing the 69 known rocky exoplanets that are also in the habitable zone.

The graph to the right, cropped and reduced to post here, shows the 45 exoplanets most likely to be habitable, with the amount of energy they get from their star measured relative to that of Earth and the Sun (shown center top). You can read their paper here. From the press release:

The researchers pinpointed 45 rocky worlds that may support life in the habitable zone, and another 24 in a narrower 3D habitable zone that makes a more conservative assumption of how much heat a planet can take before it loses its habitability.

They include some famous exoplanets, including Proxima Centauri b, TRAPPIST-1f and Kepler 186f, as well as others that are not as well known, such as TOI-715 b. The most interesting planets of those listed, according to the authors, are TRAPPIST-1 d, e, f and g, which are 40 light-years from Earth, as well as LHS 1140 b, which is 48 light-years away. Whether these planets could have liquid water depends in part if they can hold an atmosphere.

The worlds that get light from their stars most similar to what modern Earth receives from the Sun are the transiting planets TRAPPIST-1 e, TOI-715 b, Kepler-1652 b, Kepler-442 b, Kepler-1544 b and the planets Proxima Centauri b, GJ 1061 d, GJ 1002 b, and Wolf 1069 b, which make their stars wobble.

The paper includes tables listing the best exoplanets that do transits of their stars, the best with the oldest estimated ages, and the best for testing the limits of the habitable zone itself. As the researchers say in their abstract:

The resulting list of rocky exoplanet targets in the HZ will allow observers to shape and optimize search strategies with space- and ground-based telescopes – such as the James Webb Space Telescope (JWST), Extremely Large Telescope (ELT), Habitable Worlds Observatory (HWO), and Large Interferometer For Exoplanets (LIFE) – and design new observing strategies and instruments to explore these worlds, addressing the question of the limits of exoplanet surface habitability.

In other words, the focus of exoplanet research is now shifting from simply finding these planets to studying them directly, with the potentially habitable worlds listed above the most interesting of all. Astronomers might not find alien life or civilizations on these worlds, but at a minimum they will be doing the first preliminary scouting for humanity’s the first interstellar missions, with the Trappist-1 solar system appearing to head the list.

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Uranus’s moon Oberon, of which we know little

11:38 am

Uranus' five biggest moonsThe historically known moons of Uranus. Click for original NASA press release.

Oberon, as seen by Voyager-2
Click for original image.

Today we finish our week-long tour of the five largest moons of Uranus, all discovered by astronomers before the start of the space age, and imaged successfully if not very completely by Voyager-2 when it did its fly-by of the planet on January 24, 1986. The gallery of these moons above was taken by the spacecraft when it was on approach, still about three million miles from Uranus, and shows them in order from the innermost on the left to the outermost on the right. They are also scaled to show their relative sizes. To see Voyager-2’s close-up images of the four inner moons, posted earlier this week, go here, here, here, and here.

The picture to the right, cropped slightly to post here, is Voyager-2’s only high resolution image of Oberon, the outermost moon of this group. From NASA’s press release:

This Voyager 2 picture of Oberon is the best the spacecraft acquired of Uranus’ outermost moon. The picture was taken shortly after 3:30 a.m. PST on Jan. 24, 1986, from a distance of 410,000 miles. The color was reconstructed from images taken through the narrow-angle camera’s violet, clear and green filters.

The picture shows features as small as 7 miles on the moon’s surface. Clearly visible are several large impact craters in Oberon’s icy surface surrounded by bright rays similar to those seen on Jupiter’s moon Callisto. Quite prominent near the center of Oberon’s disk is a large crater with a bright central peak and a floor partially covered with very dark material. This may be icy, carbon-rich material erupted onto the crater floor sometime after the crater formed. Another striking topographic feature is a large mountain, about 6 km (4 mi) high, peeking out on the lower left limb.

Oberon is about 946 miles in diameter, making it the tenth-largest moon in the solar system. Because of the quickness of Voyager-2’s fly-by, it could get no closer images, and none of the planet’s nightside. Thus, only 40% of the surface has been photographed, and at not very high resolution.

Later spectroscopy from Hubble and other telescopes suggests there is water ice on the surface. Other data suggests Oberon may have a liquid underground ocean, but that conclusion is highly uncertain. Other than these vague facts and the image to the right, we essentially know almost nothing about this moon. Like Titiania, Uranus’s largest moon, Voyager-2’s data merely gave us a tantalizing glimpse, and that glimpse is now forty years old. No other mission has been there since, and none is planned in the near future.

Tomorrow, to summarize this tour, I will outline further what little we know of Uranus and its moons

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