Tag: astronomy

New data: young red dwarf stars are not nice stars for life

12:50 pm

New data from both the Chandra X-ray Observatory and the Hubble Space Telescope has reinforced earlier data that suggested the strong flares emitted by young red dwarf stars make them inhospitable to the development of life on any planet in the habitable zone.

A new study using NASA’s Chandra X-ray Observatory and Hubble Space Telescope examined the red dwarf called Barnard’s Star, which is about 10 billion years old, more than twice the current age of the Sun. Red dwarf stars are much cooler and less massive than the Sun, and are expected to live much longer lives because they do not burn through their fuel as fast. Barnard’s Star is one of the closest stars to Earth at a distance of only 6 light-years.

Young red dwarfs, with ages less than a few billion years, are known as strong sources of high-energy radiation, including blasts of ultraviolet light and X-rays. However, scientists know less about how much damaging radiation red dwarfs give off later in their lifetimes.

The new observations concluded that about 25% of the time, Barnard’s Star unleashes scorching flares, which may damage the atmospheres of planets closely orbiting it. While its only known planet does not have habitable temperatures, this study adds to evidence that red dwarfs may present serious challenges for life on their planets.

It is very important to remember that this data makes difficult the formation of life, as we know it. Since we know so little about such processes, as well as the formation processes of solar systems, it is too early to say whether no life can ever form around such stars.

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Scientists confirm another 44 black hole mergers detected by gravitational waves

12:16 pm

Scientists have now confirmed that since the first detection of a gravitational wave five years ago they have detected another 44 black hole mergers in the same manner.

A global network of scientists has completed the first major analysis of gravitational wave data, providing exciting insights into some of the most exotic objects in the Universe. “We are announcing the discovery of 44 confirmed black hole mergers, which is a more than a four-fold increase in the number of previously known gravitational-wave signals,” says Shanika Galaudage from Australia’s Monash University, who was part of the research team.

…Their results are described in a trio of papers on the pre-print server arXiv. The first paper describes 39 new detections from the first half of the observing run, primarily of binary black hole systems. This brings the total number of gravitational wave events detected to 47, of which 44 are confidently double black holes, two are confidently double neutron stars, and one is still uncertain.

They think they are detecting more black hole mergers because they are heavier and thus emit bigger and more easily detected waves. They are also finding that the black hole mergers fall into two classes, two holes spinning in the same direction and two holes spinning in opposite or randomly different directions. The former formed together as a binary star system. The latter formed independently and somehow ended up linked up and merging.

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Water molecules detected on Moon

10:59 am

Using NASA’s SOFIA airborne telescope, scientists have detected for the first time what they think is a very small amount of actual water molecules in areas of the Moon far from the poles.

SOFIA has detected water molecules (H2O) in Clavius Crater, one of the largest craters visible from Earth, located in the Moon’s southern hemisphere. Previous observations of the Moon’s surface detected some form of hydrogen, but were unable to distinguish between water and its close chemical relative, hydroxyl (OH). Data from this location reveal water in concentrations of 100 to 412 parts per million – roughly equivalent to a 12-ounce bottle of water – trapped in a cubic meter of soil spread across the lunar surface.

This result confirms data obtained by India’s Chandrayaan-1 lunar orbiter about a dozen years ago..

There are many caveats. First and foremost, there remain uncertainties about whether they have actually detected water molecules. From their paper’s abstract:

Widespread hydration was detected on the lunar surface through observations of a characteristic absorption feature at 3 µm by three independent spacecraft. Whether the hydration is molecular water (H2O) or other hydroxyl (OH) compounds is unknown and there are no established methods to distinguish the two using the 3 µm band. However, a fundamental vibration of molecular water produces a spectral signature at 6 µm that is not shared by other hydroxyl compounds. [emphasis mine]

This detection points to water for sure, but it remains very uncertain.

The amount is also very small, and is likely localized, as they also note, “within glasses or in voids between grains sheltered from the harsh lunar environment.” If there it will not be useful for future colonists.

The result is important, however, as it increases the likelihood that there is lots of water ice trapped in the permanently shadowed craters near the poles, in amounts that will be useful to future colonists.

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Astronomers watch star’s destruction as supermassive black hole eats it

10:27 am

Astronomers, using a number of ground-based and orbiting telescopes, successfully observed a star’s destruction as it was ripped apart and eaten by a supermassive black hole at the center of a galaxy 215 million light years away.

The team carried out observations of AT2019qiz, located in a spiral galaxy in the constellation of Eridanus, over a 6-month period as the flare grew in luminosity and then faded away. “Several sky surveys discovered emission from the new tidal disruption event very quickly after the star was ripped apart,” says Wevers. “We immediately pointed a suite of ground-based and space telescopes in that direction to see how the light was produced.”

Multiple observations of the event were taken over the following months with facilities that included X-shooter and EFOSC2, powerful instruments on ESO’s VLT and ESO’s NTT, which are situated in Chile. The prompt and extensive observations in ultraviolet, optical, X-ray and radio light revealed, for the first time, a direct connection between the material flowing out from the star and the bright flare emitted as it is devoured by the black hole. “The observations showed that the star had roughly the same mass as our own Sun, and that it lost about half of that to the monster black hole, which is over a million times more massive,” says Nicholl, who is also a visiting researcher at the University of Edinburgh.

Astronomers have seen similar events previously, but never so close and never so early in the event.

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Radio astronomers claim negative impact from satellite constellations

10:35 am

Put them on the Moon! Radio astronomers have released a paper claiming that the coming large communication satellite constellations, such as Starlink and OneWeb, will seriously impact observations with the Square Kilometer Array (SKA) of radio telescopes being built in the remote western outback of Australia.

Saturation of the instruments: very strong interfering signals can saturate the receiver systems and thereby drown out all other signals seen by the Band 5b receivers. As a consequence, all data in that frequency band would be lost, rendering these receivers useless for a portion of the time. For the first phase of the constellation deployments (about 6,400 satellites in total), saturation is predicted to occur for a few percent of the time assuming there is no direct illumination of the dishes by the satellites. For significantly larger constellation sizes (up to more than 100,000 satellites), saturation would be essentially continuous without significant mitigation measures implemented by the satellite operators.

Based on this conclusion, the astronomers estimate that for observations in this particular band they will need to look about 70% longer to get the same data, thereby cutting the number of observations by about half.

The astronomers propose this solution:

One of these mitigation techniques is for the satellite transmitters not to point their beams near the SKAO dishes. SKAO would require operators to steer their satellites’ beams away from the telescope site, a measure which would require a simple software modification with no repercussion on the constellation’s deployment, positioning or hardware. While a cost-effective implementation of this solution does depend on the hardware and software deployed on the satellites, operators already use this technique to comply with international regulations when their satellites cross the path between geostationary satellites in higher orbit and their receiving ground stations, for example to avoid affecting telecommunications and TV transmissions.

This mitigation could reduce the impact on the SKA by a factor of 10 over that noted previously and result in a 7% increase of integration time for SKA observations within the satellite transmission range 4. While any loss of sensitivity is regrettable, SKAO recognises the need for compromise between the competing scientific and commercial drivers.

The solution seems reasonable, but in truth it is only a temporary one. The permanent and smart solution for the astronomical community is to move their telescopes, in all wavelengths, off the Earth. For radio astronomy the far side of the Moon would be ideal.

And with SpaceX now developing a reusable big rocket, Starship, to put such payloads in orbit at low cost, the astronomers need to start thinking about taking advantage of this engineering. The situation for ground-based astronomer will only get worse.

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Two dozen exoplanets superior to Earth for life?

8:45 am

The uncertainty of science: A team of scientists have now identified 24 exoplanets from the Kepler telescope archive that they propse might actually be better for life than Earth itself.

All the exoplanets are rocky and terrestrial, like the Earth. All are in the habitable zone, meaning that they orbit their star at a distance that makes their general temperature comparable to Earth.

What makes them superior, according to these scientists, are three factors. First, their stars are not G-type stars, like the Sun, but K-types. K-types have much longer lifespans, 70 billion years compared to the Sun’s 8 to 10 billion, allowing more time for life to develop.

Second, the planets have a slightly greater mass than Earth.

Part of the reason the Earth is habitable is because it’s large enough to be geologically active, giving it a protective magnetic field, and has enough gravity to retain an atmosphere. According to the team, if a planet was 10 percent larger, it would have more surface area to live on. If it was 1.5 times as massive as the Earth, its interior would retain more heat from radioactive decay, would remain active longer, and hold onto its atmosphere for a longer time.

Finally, the orbits of these two dozen exoplanets makes them just slighter warmer than Earth, which is thought to be beneficial to life.

This is interesting, but it is pure guesswork. These factors might make our Earth life happier, but these scientists have no idea if such conditions are beneficial or harmful to the creation of life. At present we have zero data on what the ideal conditions would be.

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Hubble creates time lapse movie of fading supernova

10:42 am

Using the Hubble Space Telescope, astronomers have created a time lapse movie showing the fading of a supernova in a nearby galaxy over a year.

The supernova is captured by Hubble in exquisite detail within this galaxy in the left portion of the image. It appears as a very bright star located on the outer edge of one of its beautiful swirling spiral arms. This new and unique time-lapse of Hubble images created by the ESA/Hubble team shows the once bright supernova initially outshining the brightest stars in the galaxy, before fading into obscurity during the year of observations. This time-lapse consists of observations taken over the course of one year, from February 2018 to February 2019.

The video of that time lapse is embedded below the fold.

The galaxy itself is located 70 million light years away. That the supernova of this single star initially outshone the entire galaxy indicates the almost unimaginable power of the explosion.
» Read more

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A UV aurora found on Comet 67P/C-G

9:06 am

Using data from Europe’s now completed Rosetta mission to Comet 67P/C-G, scientists have detected evidence that the comet’s interaction with the Sun’s solar wind creates an aurora above the comet in ultra-violet wavelengths.

The data indicate 67P/C-G’s emissions are actually auroral in nature. Electrons streaming out in the solar wind – the stream of charged particles flowing out from the Sun – interact with the gas in the comet’s coma, breaking apart water and other molecules. The resulting atoms give off a distinctive far-ultraviolet light. Invisible to the naked eye, far-ultraviolet has the shortest wavelengths of radiation in the ultraviolet spectrum.

Labeling this phenomenon as an aurora is a bit of hype, as nothing is visible. However, the discovery does tell scientists how this comet’s coma, produced when the comet heats up in its approach to the Sun, interacts with the solar wind, and this in turn can teach them more about that wind, as well as other comets.

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Mt Wilson Observatory survives wildfire

3:47 pm

Firefighters in the past few days managed to stop the wildfire that had come within 500 feet of the historic Wilson Observatory, saving it from destruction.

There were some tense moments on the afternoon of Tuesday, September 15th, as the Bobcat Fire approached within 500 feet of the observatory complex. The battle was on after a 500–1,000 acre spot fire jumped Highway 2 in the Angeles National Forest. Fire crews rallied, cutting fire lines while aircraft flew fire suppression sorties overhead to defend the observatory. By Tuesday night, the worst had passed, though officials stressed that the effort was far from over.

The article also notes the tragic destruction of an amateur telescope observatory in another California wildfire. It will take $30,000 to local club to rebuild.

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Hubble snaps new hi-res photo of Jupiter

10:01 am

Jupiter, as seen by Hubble in 2020
Click for full image.

Astronomers have used the Hubble Space Telescope to take a new global image of Jupiter, aimed to provide an global census of the gas giant’s storm systems.

This latest image of Jupiter, taken by NASA’s Hubble Space Telescope on August 25, 2020, was captured when the planet was 406 million miles from Earth. Hubble’s sharp view is giving researchers an updated weather report on the monster planet’s turbulent atmosphere, including a remarkable new storm brewing, and a cousin of the famous Great Red Spot region gearing up to change color – again.

The moon seen to the left is Europa. Hubble takes annual images of the planets outward from Earth in order to provide scientists this global view.

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Astronomers detect the first exoplanet orbiting a white dwarf

3:33 pm

Astronomers announced today that they have detected the first exoplanet orbiting a white dwarf, meaning that it somehow survived the star’s expansion into a red giant.

The way a white dwarf is created destroys nearby objects either by incineration or gravitational destruction. White dwarfs form when stars like the Sun near the end of their life cycles. They swell up, expand to hundreds and even thousands of times their regular size, forming a red giant. Eventually, that outer, expanded layer is ejected from the star and only a hot, dense white dwarf core remains.

So how did a planet, known as WD 1856 b, that is Jupiter-like get into such a close proximity that it completes an orbit of the white dwarf (that is only 18,000 km / 11,000 miles across) every 34 hours?

“WD 1856 b somehow got very close to its white dwarf and managed to stay in one piece,” said Andrew Vanderburg, an assistant professor of astronomy at the University of Wisconsin-Madison. “The white dwarf creation process destroys nearby planets, and anything that later gets too close is usually torn apart by the star’s immense gravity. We still have many questions about how WD 1856 b arrived at its current location without meeting one of those fates.”

Here we go again: This news story, as well as all of the press releases for this announcement (here, here, here, and here) — in their effort to hype this release — all conveniently forget to mention that the very first exoplanets ever discovered back in 1992 actually orbited a pulsar, the remains of a star that had not only died but had died in a cataclysmic supernova explosion. Moreover, that discovery was not of one exoplanet, but three, forming a solar system of three rocky terrestrial exoplanets all orbiting the pulsar at distances less than 43 million miles, which would put them inside the orbit of Venus.

How those terrestrial planets survived a supernova was a mystery. Today’s discovery only heightens that same puzzle, as this Jupiter-sized exoplanet orbits much closer to its white dwarf.

Regardless, the press releases from these universities and NASA should have made these facts clear. Instead, they pump up this discovery as if it is the very first ever. Today’s discovery might have unique components (the first hot Jupiter exoplanet orbiting a white dwarf) but it isn’t the first of this kind, not by a long shot.

Expect the press by tomorrow to compound this failure. Modern reporters seem completely uneducated about the subjects they write about, and also seem all-to-willing to accept on faith whatever public relations departments tell them.

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California wildfire threatens Wilson Observatory

10:03 am

One of the many wildfires raging across California has now come with 500 feet of the Mt. Wilson Observatory.

Officials at the observatory said all personnel had been evacuated as the fire was “knocking on our door.”

Firefighters battling the blaze had made slight headway in recent days in trying to control the flames that erupted September 6, but containment shrank from 6 percent to 3 percent Tuesday, according to the Angeles National Forest. “They are in a firefight right now, because it is so close,” LA County Fire Captain David Dantic told the Los Angeles Times, referring to crews positioned at Mt. Wilson.

He said the fire, located about 16 miles (25 kilometers) northeast of downtown Los Angeles, had grown to 40,000 acres (16,200 hectares). “It’s a bigger area now,” Dantic said. “Before, we had 6 percent containment when it was about 30,000 acres, but now the fire has gotten bigger. It’s a bigger footprint. That’s why the containment is down.”

KNX radio said the fire was also threatening broadcast towers in the area worth more than a billion dollars.

If destroyed I doubt seriously there would be money to rebuild Wilson, especially because its location near the bright lights of Los Angeles limits its astronomical value. Astronomers have shifted its use to other purposes that are not as badly affected by the light pollution, but once gone it will be hard to raise the cash to bring it back.

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Tiny amount of rare chemical found on Venus; it is NOT a sign of life

8:53 am

The coming dark age: Scientists today announced that they had detected a tiny amount of the rare chemical phosphine in the upper atmosphere of Venus, and immediately jumped to the absurd conclusion that this was a sign of life.

The international team, which includes researchers from the UK, US and Japan, estimates that phosphine exists in Venus’s clouds at a small concentration, only about twenty molecules in every billion. Following their observations, they ran calculations to see whether these amounts could come from natural non-biological processes on the planet. Some ideas included sunlight, minerals blown upwards from the surface, volcanoes, or lightning, but none of these could make anywhere near enough of it. These non-biological sources were found to make at most one ten thousandth of the amount of phosphine that the telescopes saw.

To create the observed quantity of phosphine (which consists of hydrogen and phosphorus) on Venus, terrestrial organisms would only need to work at about 10% of their maximum productivity, according to the team. Earth bacteria are known to make phosphine: they take up phosphate from minerals or biological material, add hydrogen, and ultimately expel phosphine. Any organisms on Venus will probably be very different to their Earth cousins, but they too could be the source of phosphine in the atmosphere.

To leap from finding twenty molecules out of a billion of a single rare chemical to claiming this is a sign of life is absurd. And yet, this is what these scientists do, in the European Space Agency (ESA) press release at the link above, as well as this Royal Astronomical Society press release.

This discovery is not giving us “a hint of life on Venus.” All these scientists have done is detect a chemical whose formation in Venus’ very alien environment is a mystery. Yes, on Earth this chemical comes from life related activities, but to claim that the presence of biology must explain it on Venus is not science, but witchcraft and the stuff of fantasy. We know practically nothing about the full make-up of Venus’ atmosphere, its chemistry and environment, which makes it impossible to hint at any theories, no less life.

The worst part of this is that we can expect our brainless media to run with these claims, without the slightest effort of incredulity.

We live in a world of make believe and made-up science. Data is no longer important, only the leaps of fantasy we can jump to based on the slimmest of facts. It was this desire to push theories rather than knowledge that locked humanity into a dark age for centuries during the Middle Ages. It is doing it again, now, and the proof is all around you, people like zombies and sheep, wearing masks based not on any proven science but on pure emotions.

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Astronomers look at one patch of sky and see no signs of alien life

9:12 am

Worlds without end: Using an Australian radio telescope array focused in the FM frequencies, astronomers did a seventeen hour sweep of one small of sky and found no evidence of alien transmissions.

“We observed the sky around the constellation of Vela for 17 hours, looking more than 100 times broader and deeper than ever before. With this dataset, we found no technosignatures—no sign of intelligent life.”

Professor Tingay said even though this was the broadest search yet, he was not shocked by the result. “As Douglas Adams noted in The Hitchhikers Guide to the Galaxy, ‘space is big, really big’. … And even though this was a really big study, the amount of space we looked at was the equivalent of trying to find something in the Earth’s oceans but only searching a volume of water equivalent to a large backyard swimming pool.

The radio array used in this search is only a small precursor to a much larger array, dubbed the Square Kilometer Array (SKA), which is under construction and many times more sensitive.

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Newly upgraded solar telescope sees first light

9:39 am

Early image from upgraded solar telescope.

Astronomers have finished a major instrument upgrade of the GREGOR solar telescope in the Canary Islands, making it possible for them to observe features on the Sun’s surface as small as thirty miles in diameter.

The image to the right is an example of the telescope’s new capability, showing the Sun’s granular surface features. From the introduction of the paper describing the upgrade:

GREGOR is Europe’s largest solar telescope. … Its 1.5 m diameter with an optical footprint of 1.44 m allows us to resolve structures on the Sun as small as 50 km at 400 nm.

…A past drawback of GREGOR was that its image quality did not reach the theoretical limit, partly because a risk was taken with untested technologies, such as silicon carbide mirrors, which could not be polished well enough, and partly because of design problems. These difficulties have recently been solved by replacing all silicon carbide mirrors with mirrors made of Zerodur, which can be polished to the required quality, and by redesigning the AO relay optics. GREGOR now operates at its diffraction limit. [emphasis mine]

In other words, the initial mirrors did not work as promised, requiring them to replace them to get the telescope to function as initially designed. By the image above, it looks like their upgrade has worked admirably.

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A star with giant misaligned rings

8:52 am

Star with misaligned rings

Astronomers using the Atacama Large Millimeter/submillimeter Array (ALMA) have detected a nearby star, dubbed GW Ori, with multiple rings of dust with several tilted in relation to the others.

The rings, with dust equaling 75, 170, and 245 Earth masses each, are 46, 188, and 336 astronomical units (au) each from their star. (An au is the distance of the Earth to the Sun.) If you look closely at the image to the right, you can see that the inner rings are circular, while the outer rings appear oval, suggesting that we are looking directly down at the inner rings, but the outer rings are tilted to our line of sight. Moreover, another team of astronomers

…observed GW Ori with ALMA and the European Southern Observatory’s Very Large Telescope (VLT). Near infrared observation with VLT showed for the first time that the innermost ring casts a shadow on the outer rings, which is clear evidence of disk misalignment. Kraus and his colleagues also performed a computer simulation and suggest that the triple star system can create misaligned rings, without gravitational assistance from planets. The two teams have different theories for the origin of the misaligned rings, but no conclusions have been reached so far. Nevertheless, GW Ori is a precious example to understand planet formation in the complex gravitational environment around multiple stars. [emphasis mine]

As noted, there is no agreement on the cause of the misalignment, only that it does exist.

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Biggest black hole merger yet detected by gravitational waves

3:30 pm

The uncertainty of science: In May 2020 scientists using the LIGO and VIGO gravitational waves telescopes detected evidence of a merger from two giant black holes, one of which was of a size that according to all theories had been considered “impossible.”

The short gravitational wave signal, GW190521, captured by the LIGO and Virgo gravitational wave observatories in the United States and Europe on 21 May last year, came from two highly spinning, mammoth black holes weighing in at a massive 85 times and 66 times the mass of the Sun, respectively.

But that is not the only reason this system is very special. The larger of the two black holes is considered `impossible’. Astronomers predict that stars between 65 – 130 times the mass of the Sun undergo a process called pair instability, resulting in the star being blown apart, leaving nothing behind.

With a mass of 85 solar masses, the larger black hole falls squarely in that forbidden range, referred to as the upper black hole mass gap, and should be `impossible’.

The explanation the scientists propose is that this black hole initially formed with a mass smaller than 65 solar masses, and then sucked in matter, including a possible additional black hole merger, that raised its weight to 85 solar masses.

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Hubble maps giant gas halo around Andromeda

11:38 am

Astronomers using the Hubble Space Telescope’s ability to observe in ultraviolet wavelengths have now mapped the giant halo of gas that surrounds the Andromeda galaxy 2.5 million light years away.

The work found that the halo appears to have both an inner and outer shell.

“We find the inner shell that extends to about a half million light-years is far more complex and dynamic,” explained study leader Nicolas Lehner of the University of Notre Dame in Indiana. “The outer shell is smoother and hotter. This difference is a likely result from the impact of supernova activity in the galaxy’s disk more directly affecting the inner halo.”

A signature of this activity is the team’s discovery of a large amount of heavy elements in the gaseous halo of Andromeda. Heavier elements are cooked up in the interiors of stars and then ejected into space—sometimes violently as a star dies. The halo is then contaminated with this material from stellar explosions.

The Andromeda galaxy, also known as M31, is a majestic spiral of perhaps as many as 1 trillion stars and comparable in size to our Milky Way. At a distance of 2.5 million light-years, it is so close to us that the galaxy appears as a cigar-shaped smudge of light high in the autumn sky. If its gaseous halo could be viewed with the naked eye, it would be about three times the width of the Big Dipper. This would easily be the biggest feature on the nighttime sky.

Though there is of course uncertainty here, this research is confirming earlier work, making its conclusions more robust.

A side note: Ultraviolet observations can only be done in space, as the atmosphere blocks it. Hubble I think is the only telescope in space right now with this capability. There used to be others, the most noteworthy of all being the International Ultraviolet Explorer, which functioned from 1978 to 1996 but was then decommissioned because neither NASA nor ESA were willing to fund its operation any longer.

No replacements have been launched because the budget for space astronomy has almost entirely been eaten by the overbudget and long delayed James Webb Space Telescope, with future budgets to be eaten similarly by the Roman.Space Telescope.

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Astronomers discover three merging supermassive black holes

9:03 am

Using telescopes on Mauna Kea in Hawaii, astronomers have discovered three different galaxies that have pairs of supermassive black holes at their center, with all three likely to merge at some point in the future.

First the scientists used the Subaru Telescope to survey more than 34,000 known quasars, high energy supermassive black holes.

The team identified 421 promising cases. However, there was still the chance many of these were not bona-fide dual quasars but rather chance projections such as starlight from our own galaxy. Confirmation required detailed analysis of the light from the candidates to search for definitive signs of two distinct quasars.

Using Keck Observatory’s Low Resolution Imaging Spectrometer (LRIS) and Gemini Observatory’s Near-Infrared Integral Field Spectrometer, Silverman and his team identified three dual quasars, two of which were previously unknown. Each object in the pair showed the signature of gas moving at thousands of kilometers per second under the influence of a supermassive black hole.

From this survey work they now tentatively estimate that only 0.3% of all known quasars are likely made up of a binary, which in turn gives them a rough estimate of how often galaxies with such supermassive black holes collide and merge. This in turn helps them develop theories on galaxy formation.

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Report: Astronomy threatened by satellite constellations

11:31 am

A report issued today, resulting from a video conference of astronomers in July, has concluded that much of ground-based astronomy is threatened by the new large satellite constellations being launched by SpaceX, OneWeb, and others.

The astronomers’ report offers six solutions for solving the problem.

  • Launch fewer or no LEOsats. However impractical or unlikely, this is the only option identified that can achieve zero astronomical impact.
  • Deploy satellites at orbital altitudes no higher than ~600 km.
  • Darken satellites or use sunshades to shadow their reflective surfaces.
  • Control each satellite’s orientation in space to reflect less sunlight to Earth.
  • Minimize or eventually be able to eliminate the effect of satellite trails during the processing of astronomical images.
  • Make more accurate orbital information available for satellites so that observers can avoid pointing telescopes at them.

Notice what solution they don’t offer? Maybe astronomy should focus on building space-based telescopes, where the view would be clear, unimpeded by both the satellites and (much more importantly) the atmosphere.

In fact, the claim in the first solution above, that launching no satellites is “the only option identified that can achieve zero astronomical impact” is intellectually dishonest. All astronomers have to do is get their observatories into space, something that is very doable and affordable with today’s cheaper launch capabilities and technology. In space the impact of the satellites will once again be zero. And they will have the added benefit of getting outside the atmosphere, which by the way is actually a bigger limitation to observations than any satellite constellation.

It seems to me that this report was written by the faction of astronomers who make their living building big ground-based telescopes. Rather than think of solutions, they want to protect their turf by attacking the achievements of others.

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Hubble photographs Comet NEOWISE

12:38 pm

Comet NEOWISE, photographed by the Hubble Space Telescope
Click for full image.

Using the Hubble Space Telescope, astronomers have obtained close-up images of Comet NEOWISE after it had survived its closest approach to the Sun. The photo to the right, cropped and reduced to post here, is one of Hubble’s two images.

Comets often break apart due to thermal and gravitational stresses at such close encounters, but Hubble’s view suggests that NEOWISE’s solid nucleus stayed intact. This heart of the comet is too small to be seen directly by Hubble. The ball of ice may be no more than 4.8 kilometres across. But the Hubble image does captures a portion of the vast cloud of gas and dust enveloping the nucleus, which measures about 18 000 kilometres across in this image.

Hubble’s observation also resolves a pair of jets from the nucleus shooting out in opposite directions. They emerge from the comet’s core as cones of dust and gas, and then are curved into broader fan-like structures by the rotation of the nucleus. Jets are the result of ice sublimating beneath the surface with the resulting dust/gas being squeezed out at high velocity.

Below the fold is a six-second movie made of Hubble’s two images, showing how the jets changed over a three hour time period on August 8th.
» Read more

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Tiny asteroid sets record for closest fly-by of Earth

9:10 am

Astronomers using the robotic Zwicky Transient Facility (ZTF) at the Palomar Observatory in California on August 16 spotted a tiny asteroid just after it had zipped past the Earth at a distance of only 1,830 miles, the closest any asteroid has ever been seen to do so without hitting the ground.

Asteroid 2020 QG is about 10 to 20 feet (3 to 6 meters) across, or roughly the size of an SUV, so it was not big enough to do any damage even if it had been pointed at Earth; instead, it would have burned up in our planet’s atmosphere.

“The asteroid flew close enough to Earth that Earth’s gravity significantly changed its orbit,” says ZTF co-investigator Tom Prince, the Ira S. Bowen Professor of Physics at Caltech and a senior research scientist at JPL, which Caltech manages for NASA. Asteroids of this size that fly roughly as close to Earth as 2020 QG do occur about once a year or less, but many of them are never detected.

The ability to spot these things is continuing to improve, though it does not appear they have yet obtained enough information to predict 2020 QG’s full orbit, or when or if it will return.

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Oumuamua wasn’t made of hydrogen ice

9:45 am

The uncertainty of science: According to a new paper published today, Oumuamua wasn’t a hydrogen iceberg as proposed by other scientists earlier this year.

Traveling at a blistering speed of 196,000mph in 2017, ‘Oumuamua was first classified as an asteroid, and when it later sped up, was found to have properties more akin to comets. But the 0.2km radius interstellar object didn’t fit that category, either, and its point of origin has remained a mystery. Researchers focused on the giant molecular cloud (GMC) W51—one of the closest GMCs to Earth at just 17,000 light years away—as a potential point of origin for ‘Oumuamua, but hypothesize that it simply could not have made the journey intact. “The most likely place to make hydrogen icebergs is in the densest environments of the interstellar medium. These are giant molecular clouds,” said Loeb, confirming that these environments are both too far away and are not conducive to the development of hydrogen icebergs.

The hydrogen iceberg theory was for many reasons very very speculative, and not very convincing, which is why I never posted a link to it when it became clickbait for the mainstream press several months ago. The object’s behavior as it zipped through the solar system, combined with its elongated shape, still leave us with questions. While some scientists have definitely stated it could not have been an alien spacecraft, that likely conclusion remains as uncertain as the theory that it was a hydrogen iceberg.

The only way we will definitely know is to go and look at it. And such a mission remains possible, with launch dates in 2021, 2022, or 2023, with technology we presently have, if we were to move fast.

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Giant impact covered almost half of Gandymede’s surface

9:31 am

Artist's illustration of Ganydmede
Click for full illustration.

The uncertainty of science: Computer modeling and a review of images taken by Voyager 1 and 2 and the Galileo orbiter of Jupiter’s moon Ganymede now suggest the existence of a giant impact so large that it covers almost half the moon’s surface.

The artist’s illustration of Ganymede on the right, based on our presently incomplete set of global images, shows this impact area as the circular dark region.

Many furrows, or trough formations, have been observed on the surface of Ganymede, one of the Jovian moons. This research group comprehensively reanalyzed image data of Ganymede obtained by NASA’s Voyager 1, Voyager 2, and Galileo spacecrafts. The results revealed that almost all of these furrows appear to be arranged in concentric rings centered around a single point, indicating that this global multiring structure may be the remains of a giant crater. The radial extent of the multiring structures measured along Ganymede’s surface is 7800 km. For comparison, the mean circumference of Ganymede is only 16,530 km. If correct, this is the largest crater yet identified in the Solar System. The previous record holder with a 1900 km radius is on Calisto, another Jovian moon.

The conclusion reached here is very uncertain, since we really do not have a high resolution global map of Ganymede. All three spacecraft were only able to send back a scattering of high resolution images. The global map is based on Earth observations and images from the Hubble Space Telescope.

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Betelgeuse dimming caused by outburst

9:08 am

The uncertainty of science: According to new data from the Hubble Space Telescope, astronomers are now proposing that the dimming seen earlier this year in the red giant Betelgeuse was caused not by a known variation cycle or by a large starspot moving across its surface, but by an large outburst of material, thrown out from the star.

Ultraviolet observations by the Hubble Space Telescope suggest that the unexpected dimming was probably caused by an immense amount of superhot material ejected into space. The material cooled and formed a dust cloud that blocked the starlight coming from about a quarter of Betelgeuse’s surface.

That we now have three creditable but different theories, all based on evidence, for explaining the dimming that occurred from October 2019 to April 2020 suggests that we really still have no idea what specifically caused it. All three theories however are based on what we do know about Betelgeuse, that it is giant blobby gasbag that has dark starspots on its surface, that has giant convection cells that bubble up from below and release material periodically, and that it pulses in a variety of cycles predictably over time.

It could be any of these phenomenon that caused last year’s dimming, or even a combination of two or more. The information available so far is just too sketchy to pin this down more precisely.

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Snapped cable damages Arecibo radio telescope

12:25 pm

One of the cables that supports the central platform above the Arecibo Observatory’s giant dish snapped yesterday, damaging the dish and shutting down operations.

The break occurred about 2:45 a.m. When the three-inch cable fell it also damaged about 6-8 panels in the Gregorian Dome and twisted the platform used to access the dome. It is not yet clear what caused the cable to break. “We have a team of experts assessing the situation,” says Francisco Cordova, the director of the observatory. “Our focus is assuring the safety of our staff, protecting the facilities and equipment, and restoring the facility to full operations as soon as possible, so it can continue to assist scientists around the world.”

The radio telescope has not much luck the past few years. It was badly damaged and shut down for a long time after Hurricane Maria in 2017, with repairs from that still on-going.

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TESS completes primary mission

9:33 am

Having now imaged 75% of the entire night sky and completing its primary mission, scientists have now begun the extended mission for the Transiting Exoplanet Survey Satellite (TESS), designed to look for transiting exoplanets.

TESS monitors 24-by-96-degree strips of the sky called sectors for about a month using its four cameras. The mission spent its first year observing 13 sectors comprising the southern sky and then spent another year imaging the northern sky.

Now in its extended mission, TESS has turned around to resume surveying the south. In addition, the TESS team has introduced improvements to the way the satellite collects and processes data. Its cameras now capture a full image every 10 minutes, three times faster than during the primary mission. A new fast mode allows the brightness of thousands of stars to be measured every 20 seconds, along with the previous method of collecting these observations from tens of thousands of stars every two minutes. The faster measurements will allow TESS to better resolve brightness changes caused by stellar oscillations and to capture explosive flares from active stars in greater detail.

These changes will remain in place for the duration of the extended mission, which will be completed in September 2022. After spending a year imaging the southern sky, TESS will take another 15 months to collect additional observations in the north and to survey areas along the ecliptic – the plane of Earth’s orbit around the Sun – that the satellite has not yet imaged.

So far the telescope has spotted more than 2,100 exoplanet candidates, with 66 confirmed.

All told, TESS has divided the sky into 26 sectors, 13 in the north and 13 in the south. It can only look at one at a time for a month, and scientists use that one month data, collected more than once, to see if there are any changes. Because of the gaps in TESS’s view of each sector, however, it is guaranteed to miss some exoplanets (the majority) whose transits occur when it is not looking.

Imagine if we had 25 more of these space telescopes in orbit, so that each sector could be watched continually. This is totally doable now, and would make it possible to soon create a census of transiting exoplanets across the entire sky.

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Astronomers use Hubble to detect ozone on Earth

8:57 am

Using the Hubble Space Telescope, scientists have shown that it will be possible to detect ozone in the atmospheres of exoplanets, using larger telescopes while observing transits of those exoplanets across the face of their star.

What the scientists did was aim Hubble at the Moon during a lunar eclipse. Moreover, they timed the observations so that the sunlight hitting the Moon and reflecting back to Earth (and Hubble) had also traveled through the Earth’s atmosphere on its way to the Moon.

They then looked at the spectrum of that light, and were able to glean from it the spectral signal of ozone in the Earth’s atmosphere. When giant ground-based telescopes under construction now come on line in the coming decades they will have the ability to do this with transiting exoplanets.

The measurements detected the strong spectral fingerprint of ozone, a key prerequisite for the presence – and possible evolution – of life as we know it in an exo-Earth. Although some ozone signatures had been detected in previous ground-based observations during lunar eclipses, Hubble’s study represents the strongest detection of the molecule to date because it can look at the ultraviolet light, which is absorbed by our atmosphere and does not reach the ground. On Earth, photosynthesis over billions of years is responsible for our planet’s high oxygen levels and thick ozone layer. Only 600 million years ago Earth’s atmosphere had built up enough ozone to shield life from the Sun’s lethal ultraviolet radiation. That made it safe for the first land-based life to migrate out of our oceans.

“Finding ozone in the spectrum of an exo-Earth would be significant because it is a photochemical byproduct of molecular oxygen, which is a byproduct of life,” explained Allison Youngblood of the Laboratory for Atmospheric and Space Physics in Colorado, USA, lead researcher of Hubble’s observations.

Ozone does not guarantee the presence of life on an exoplanet, but combined with other detections, such as oxygen and methane, would raise the odds significantly.

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Astronomers find freshly fallen meteorites based on tracking their fall

11:36 am

Australian astronomers have found two meteorites on the ground after spotting them in the sky before they fell, with one found only

The first had been spotted in the sky only a few weeks earlier, while the second had been spotted back in November 2019. They had had to postpone the search for the second until the restrictions for the Wuhan flu were lifted.

The discovery of the first was amusing:

Astronomer Dr Hadrien Devillepoix and planetary geologist Dr Anthony Lagain originally went on a reconnaissance mission to assess the latest fall site near Madura, taking drone imagery of the area. Dr Devillepoix said that as they were walking back to their car along the old telegraph track near Madura Cave, they spotted what appeared to be a real meteorite on the ground just in front of them.

“I thought Anthony was playing a prank on me, that he planted one of the fake meteorites we were using for the drone training session. But after a closer inspection, it was evident that the fist-sized, 1.1 kilogram rock we just found was indeed the meteorite we were after,” Dr Devillepoix said. Dr Devillepoix explained that although the rock was very close to the predicted fall position, the team was not expecting to find it that quickly in this bushy terrain.

Based on its track as it fell, the astronomers think it might be from the Aten family of asteroids, which orbit the Sun between Venus and Earth. Such asteroids are hard to find because of the glare of the Sun, and are thus not as well studied. This makes this find even more significant.

Finds like this, which are beginning to happen more and more, are important because, first, the meteorite doesn’t spend much time in the Earth environment, and second, they can precisely identify where the asteroid came from. Both facts allow scientists a much better understanding of the asteroids themselves.

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Neutron star left over from Supernova 1987A?

8:24 am

The uncertainty of science: Two different teams of astronomers are now suggesting that, based on evidence recently obtained by the Atacama Large Millimeter/submillimeter Array (ALMA), a neutron star is what is left over from the star that caused Supernova 1987A, the only naked eye supernova in the past four hundred years.

Recently, observations from the ALMA radio telescope provided the first indication of the missing neutron star after the explosion. Extremely high-resolution images revealed a hot “blob” in the dusty core of SN 1987A, which is brighter than its surroundings and matches the suspected location of the neutron star.

..The theoretical study by Page and his team, published today in The Astrophysical Journal, strongly supports the suggestion made by the ALMA team that a neutron star is powering the dust blob. “In spite of the supreme complexity of a supernova explosion and the extreme conditions reigning in the interior of a neutron star, the detection of a warm blob of dust is a confirmation of several predictions,” Page explained.

These predictions were the location and the temperature of the neutron star. According to supernova computer models, the explosion has “kicked away” the neutron star from its birthplace with a speed of hundreds of kilometers per second (tens of times faster than the fastest rocket). The blob is exactly at the place where astronomers think the neutron star would be today. And the temperature of the neutron star, which was predicted to be around 5 million degrees Celsius, provides enough energy to explain the brightness of the blob.

They haven’t actually gotten any direct evidence of this stellar remnant, so some healthy skepticism is required. At the same time, the data favors this solution, which means the star did not collapse into a black hole when it exploded.

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