Tag: astronomy

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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A July 4th Hubble image of Saturn

10:27 am

Saturn as seen by Hubble on July 4, 2020
Click for full image, annotated.

Cool image time! The photo to the right, cropped and reduced to post here, was taken by the Hubble Space Telescope on July 4, 2020, and shows Saturn, its rings, plus several moons, in all their glory.

The dot near the bottom center is Enceladus. The dot at center right is Mimas. If you click on the annotated full image it will show the locations of several other smaller moons much harder to see.

This new Saturn image was taken during summer in the planet’s northern hemisphere.

Hubble found a number of small atmospheric storms. These are transient features that appear to come and go with each yearly Hubble observation. The banding in the northern hemisphere remains pronounced as seen in Hubble’s 2019 observations, with several bands slightly changing color from year to year. The ringed planet’s atmosphere is mostly hydrogen and helium with traces of ammonia, methane, water vapor, and hydrocarbons that give it a yellowish-brown color.

Hubble photographed a slight reddish haze over the northern hemisphere in this color composite. This may be due to heating from increased sunlight, which could either change the atmospheric circulation or perhaps remove ices from aerosols in the atmosphere. Another theory is that the increased sunlight in the summer months is changing the amounts of photochemical haze produced.

The distance across from one end of the rings to the other is about 150,000 miles, about two thirds the distance from the Earth to the Moon.

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First image of multi-exoplanets around young sunlike star

10:00 am

Two exoplanets in one image

Worlds without end: Using the Very Large Telescope (VLT) in Chile, astronomers have taken the first image that captures two different exoplanets circling a young sunlike star.

The star’s light is partly blocked in the upper left of the photo to the right, cropped slightly to post here.

You can read the paper here [pdf]. The star itself, though similar in mass to the Sun, is thought to be only seventeen million years old.

But the system, dubbed TYC 8998-760-1, is nothing like our solar system. One of the star’s companions straddles the line that defines planets, with a mass 14 times Jupiter’s; the other has a mass of six Jupiters. Both orbit far from the star, about 160 and 320 times the average distance between Earth and the Sun. That puts them more than four times farther out than Pluto is from the Sun.

The size and distance of these giant planets were why they could be imaged from the ground.

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After releasing its Ryugu samples Hayabusa-2’s mission will continue

8:33 am

Japan’s space agency JAXA has revealed that it is looking at two fast-spinning asteroids as possible destinations for its Hayabusa-2 spacecraft after it has dropped off its samples from the asteroid Ryugu on December 6.

The candidate asteroids on the agency’s list are asteroid 2001AV43 which Hayabusa2 would reach in November 2029 after flying by Venus, and asteroid 1998KY26 which the probe would reach in July 2031 after passing by another asteroid.

JAXA says both asteroids are rotating on their axis once every 10 minutes. The high-speed spinning indicates that the asteroids’ inner structures are likely different from that of asteroid Ryugu on the first mission, which consists of pieces of rocks.

The spacecraft will no longer have the equipment for returning additional samples, but everything else is functioning and it has the fuel.

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Active volcanoes on Venus?

9:25 am

Using computer models and past radar images from orbiters, scientists now believe that Venus could have as many as 37 active volcanoes.

The type of feature on Venus they think might still be active is called a coronae, circular features detected by radar and distinct to this planet that have been thought to be inactive ancient volcanic features.

In the new study, the researchers used numerical models of thermo-mechanic activity beneath the surface of Venus to create high-resolution, 3D simulations of coronae formation. Their simulations provide a more detailed view of the process than ever before.

The results helped Montési and his colleagues identify features that are present only in recently active coronae. The team was then able to match those features to those observed on the surface of Venus, revealing that some of the variation in coronae across the planet represents different stages of geological development. The study provides the first evidence that coronae on Venus are still evolving, indicating that the interior of the planet is still churning.

Lots of uncertainty here, but nonetheless this is good science. It also reinforces other evidence in recent years that has suggested active volcanism on Venus.

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The magnetic field of a spiral galaxy

9:05 am

Magnetic field of a spiral galaxy
Click for full image.

Using a variety of telescopes, especially the Jansky Very Large Array radio telescope, astronomers have successfully mapped the magnetic field lines of a spiral galaxy seen edge on and 67 million light years away.

The image to the right, cropped and reduced to post here, shows what they have found.

The magnetic field lines extend as much as 22,500 light-years beyond the galaxy’s disk. Scientists know that magnetic fields play an important role in many processes, such as star formation, within galaxies. However, it is not fully understood how such huge magnetic fields are generated and maintained. A leading explanation, called the dynamo theory, suggests that magnetic fields are generated by the motion of plasma within the galaxy’s disk. Ideas about the cause of the kinds of large vertical extensions seen in this image are more speculative, and astronomers hope that further observations and more analysis will answer some of the outstanding questions.

Our understanding of these kinds of gigantic magnetic fields is poor, to put it mildly. This data really only begins the research.

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No TMT construction until 2021, according to its builders

9:19 pm

According to the university consortium building the Thirty Meter Telescope (TMT), they will make no attempt to begin construction until the end of winter in 2021.

According to the official spokesman, the consortium remains committed to building the telescope in Hawaii on Mauna Kea, but I do not see how it will ever happen. The present Democratic government supports the protesters, and there is no chance that government will ever be voted out of power.

Based on this information, I do not think TMT will ever be built, anywhere.

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Comet Neowise: NOW is the time to go see it

8:59 am

Comet Neowise is now visible each evening just after sunset. This article shows a bunch of images produced by people worldwide.

The comet will not be back for thousands of years, so this will be your only chance to see it. And usually good evening-view comets occur only once every few decades, usually not more than once or thrice every century. If you want to see a comet in all its glory, Comet Neowise is giving you a chance, and now is the time to look.

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It appears we will have a comet show in July!

8:55 am

After two other comets this spring suggested they might become bright naked eye objects and then fizzled, it now appears that Comet NEOWISE will deliver, having survived its closest approach to the Sun to now brighten towards first magnitude.

For the northern hemisphere, this is what to expect if you wish to see it:

In the morning sky, the first views of NEOWISE could come as early as July 5 or 6 in the morning sky, very low above the northeast horizon. By around July 11, the comet will reach an altitude of nearly 10 degrees — for comparison, 10 degrees is roughly equal to the width of your fist held at arm’s length. Then over the next 10 days it will gradually slide back down toward the north-northeast horizon, eventually disappearing from dawn visibility.

A far-better viewing perspective will become available in the evening sky starting around July 12, when it will appear low in the northwest sky. In the evenings to follow, the comet will rapidly climb higher in the sky.

On July 22, NEOWISE will make its closest approach to the Earth, a distance of 64 million miles (103 million km). By July 25, the comet will appear 30 degrees (“three fists”) up from the west-northwest horizon as darkness falls. And on July 30-31st, the comet will be passing just to the north of the fine star cluster of Coma Berenices or Berenice’s Hair.

Will this comet brighten more to become comparable to glorious Comet Hale-Bopp in 1997? Keep your fingers crossed.

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New storm outbreak on Jupiter

10:00 am

Clyde's Spot
Click for full image.

A new storm, dubbed Clyde’s spot after its discoverer, developed suddenly in late May on Jupiter, and has been imaged by Juno during its most recent close fly-by of the gas giant planet.

The image to the right, cropped to post here, focuses in on this spot. It is the feature in the center of the full image, with the Great Red Spot to the upper left.

The new feature was discovered by amateur astronomer Clyde Foster of Centurion, South Africa. Early on the morning of May 31, 2020, while imaging Jupiter with his telescope, Foster noticed a new spot, which appeared bright as seen through a filter sensitive to wavelengths of light where methane gas in Jupiter’s atmosphere has strong absorption. The spot was not visible in images captured just hours earlier by astronomers in Australia.

On June 2, 2020, just two days after Clyde Foster’s observations, Juno performed its 27th close flyby of Jupiter. The spacecraft can only image a relatively thin slice of Jupiter’s cloud tops during each pass. Although Juno would not be travelling directly over the outbreak, the track was close enough that the mission team determined the spacecraft would obtain a detailed view of the new feature, which has been informally dubbed “Clyde’s Spot.”

The feature is a plume of cloud material erupting above the upper cloud layers of the Jovian atmosphere. These powerful convective “outbreaks” occasionally erupt in this latitude band, known as the South Temperate Belt

The coolest thing about this is that the storm was spotted by an amateur, using a ground-based telescope, within hours of its inception.

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Calling this exoplanet alien is an understatement

10:03 am

Worlds without end: Using the space telescope TESS astronomers have determined that one of the hottest exoplanets known, with surface temperatures as much as 7,800 degrees Fahrenheit (hotter than our Sun), is even stranger than expected.

Not only does the exoplanet have a polar orbit around its star, that star rotates so fast that its equator bulges out, actually making its poles as much as 1,500 degrees F hotter than the equator.

With each orbit, KELT-9 b twice experiences the full range of stellar temperatures, producing what amounts to a peculiar seasonal sequence. The planet experiences “summer” when it swings over each hot pole and “winter” when it passes over the star’s cooler midsection. So KELT-9 b experiences two summers and two winters every year, with each season about nine hours.

The star, about 670 light years away, is thought to be twice as massive as the Sun, with the exoplanet having a mass 2.9 times that of Jupiter. Whether it is a gas giant like Jupiter or has an atmosphere is entirely unknown. At these temperatures the situation is so alien we really only know the orbit and approximate range of temperatures.

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Giant dark starspots explain Betelgeuse’s dimming last year

9:42 am

Astronomers now think that unusually large dark starspots on the face of the red supergiant star Betelgeuse caused its dimming from October 2019 to April 2020.

“Corresponding high-resolution images of Betelgeuse from December 2019 show areas of varying brightness. Together with our result, this is a clear indication of huge star spots covering between 50% and 70% of the visible surface and having a lower temperature than the brighter photosphere,” said co-author Peter Scicluna from the European Southern Observatory (Eso).

“For comparison, a typical sunspot is the size of the Earth. The Betelgeuse star spot would be a hundred times larger than the Sun. The sudden fading of Betelgeuse does not mean it is going supernova. It is a supergiant star growing a super-sized star spot.” said co-author Prof Albert Zijlstra from The University of Manchester, UK

Starspots have been identified on the surface of Betelgeuse previously, so what is interesting here is how large these spots were.

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Two super-Earths found orbiting nearby red dwarf star

2:40 pm

Worlds without end: Astronomers have detected evidence of two super-Earths orbiting Gliese 887, only 11 light years away and the brightest red dwarf star in the night sky.

They used a technique known as “Doppler wobble”, which enables them to measure the tiny back and forth wobbles of the star caused by the gravitational pull of the planets. The regular signals correspond to orbits of just 9.3 and 21.8 days, indicating two super-Earths – Gliese 887b and Gliese 887c – both larger than the Earth yet moving rapidly, much faster even than Mercury. Scientists estimate the temperature of Gliese 887c to be around 70oC.

Because Gliese 887 is a very constant star, not very active, and with relatively few strong flares, they think these planets have a chance of retaining their atmospheres.

Be aware that these are like most exoplanets only candidate exoplanets. Until their existence is confirmed by other researchers, it is possible the detection is a false one.

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A host of new solar systems

11:20 am

A gallery of baby solar systems

Worlds without end: Astronomers this month released a large collection of images taken during the past four years by the Gemini South Telescope in Chile of young stars that also have debris disks and are likely solar systems in the process of forming.

The image to the right, reduced slightly to post here, is only a sampling of the 26 disk systems found out of 104 young stars photographed. Go to the link to see some higher resolution examples.

Of the 26 images of debris disks obtained by the Gemini Planet Imager (GPI), 25 had “holes” around the central star that likely were created by planets sweeping up rocks and dust. Seven of the 26 were previously unknown; earlier images of the other 19 were not as sharp as those from GPI and often didn’t have the resolution to detect an inner hole. The survey doubles the number of debris disks imaged at such high resolution.

“One of the things we found is that these so-called disks are really rings with inner clearings,” said Esposito, who is also a researcher at the SETI Institute in Mountain View, California. “GPI had a clear view of the inner regions close to the star, whereas in the past, observations by the Hubble Space Telescope and older instruments from the ground couldn’t see close enough to the star to see the hole around it.”

The data strongly confirms most theories about planet formation in these debris disks, as one of the youngest stars did not have any gaps in its disk, suggesting no larger bodies had yet formed to clear out a region.

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Astronomers claim discovery of six exomoons

9:03 am

The uncertainty of science: Astronomers are now claiming they have detected evidence of the existence of six exomoons orbiting different stars with transiting exoplanets.

“These exomoon candidates are so small that they can’t be seen from their own transits. Rather, their presence is given away by their gravitational influence on their parent planet,” Wiegert said.

If an exoplanet orbits its star undisturbed, the transits it produces occur precisely at fixed intervals.

But for some exoplanets, the timing of the transits is variable, sometimes occurring several minutes early or late. Such transit timing variations – known as TTVs – indicate the gravity of another body. That could mean an exomoon or another planet in the system is? affecting the transiting planet.

What they have basically done is applied the technique used to identify exoplanet candidates when the planet does NOT transit the star (the wobble caused by gravity and indicated by spectral changes), and looked to see if they can see the same variations in these exoplanets.

This is fun stuff, but it is so uncertain as to be almost laughable. If you read the press release closely, you will discover that their work has been submitted for publication, but has not yet been even peer reviewed.

Their concept is good, but I would not pay much attention to these “results.”

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Two new multi-wavelength Hubble images of planetary nebulae

11:05 am

Hubble images of the Butterfly and Jewel Bug planetary nebulae
Click for full image.

Cool images from Hubble! Astronomers have used the Hubble Space Telescope’s entire suite of instruments to produce spectacular new multi-wavelength images of two planetary nebulae, stars that for some reasons not yet entirely understood are surrounded by breath-taking jets and cloud-formations of all shapes and sizes.

The two images are to the right, cropped and reduced to post here.

Planetary nebulas, whose stars shed their layers over thousands of years, can turn into crazy whirligigs while puffing off shells and jets of hot gas. New images from the Hubble Space Telescope have helped researchers identify rapid changes in material blasting off stars at the centers of two nebulas — causing them to reconsider what is happening at their cores.

In the case of NGC 6302, dubbed the Butterfly Nebula, two S-shaped streams indicate its most recent ejections and may be the result of two stars interacting at the nebula’s core. In NGC 7027, a new cloverleaf pattern — with bullets of material shooting out in specific directions — may also point to the interactions of two central stars. Both nebulas are splitting themselves apart on extremely short timescales, allowing researchers to measure changes in their structures over only a few decades.

This is the first time both nebulas have been studied from near-ultraviolet to near-infrared light, a complex, multi-wavelength view only possible with Hubble.

The press release suggests that the most likely and popular explanation for the formation of planetary nebula is the interaction of two closely orbiting stars. While this might be true, it remains only one theory among many, all of which explain some of what we see and none of which explain everything. As I noted in my November 2014 cover story about planetary nebulae for Sky & Telescope:
» Read more

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A fast radio burst that beats every sixteen days

11:59 am

Astronomers have now added to the mystery of fast radio bursts (FRBs), of which about a hundred are known, by discovering one in a nearby galaxy that has a regular outburst every 16.35 days.

Earlier this year CHIME worked with astronomers in Europe to pinpoint the origin of a particular FRB emission — called FRB 180916.J0158+65 — to a galaxy located 500 million light years from Earth.

Now CHIME has determined that FRB 180916 pulses at predictable intervals more than two weeks apart. “It tells us that the origin of at least some FRBs is astrophysically regular in nature, but on long enough time scales that they may be tied to something different than a rotating, compact object — perhaps something like an orbiting system,” said Newburgh, whose lab builds instrumentation for collecting data about the history of the cosmos

Or to put it another way, they really haven’t any idea yet what exactly causes these bursts. The new data however will help formulate better theories, that I guarantee will be contradicted by subsequent new data. At the moment there is so little known about FRBs that any theory must be looked at with great skepticism.

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Astronomers discover giant arc spanning a third of the night sky

9:05 am

Astronomers have discovered a giant arc of hydrogen gas near the Big Dipper that span a third of the night sky and is thought to be the leftover shockwave from a supernova.

Ultraviolet and narrowband photography have captured the thin and extremely faint trace of hydrogen gas arcing across 30°. The arc, presented at the recent virtual meeting of the American Astronomical Society, is probably the pristine shockwave expanding from a supernova that occurred some 100,000 years ago, and it’s a record-holder for its sheer size on the sky.

Andrea Bracco (University of Paris) and colleagues came upon the Ursa Major Arc serendipitously when looking through the ultraviolet images archived by NASA’s Galaxy Evolution Explorer (GALEX). They were looking for signs of a straight, 2° filament that had been observed two decades ago — but they found out that that length of gas was less straight than they thought, forming instead a small piece of a much larger whole.

This is a great illustration of the uncertainty of science. Earlier observations spotted only 2 degrees of this arc, and thus thought it was a straight filament. Newer more sophisticated observations show that this first conclusion was in error, that it was much bigger, and curved.

I wonder what even more and better observations would reveal.

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Antares’ vast blobby atmosphere

9:12 am

The atmosphere of Antares
Click for full image.

Using the Atacama Large Millimeter/submillimeter Array (ALMA) and the Jansky Very Large Array (VLA), astronomers have been able to map out the gigantic atmosphere of gas that surrounds the red gas supergiant star Antares, the closest such star to our solar system.

The ALMA and VLA map of Antares is the most detailed radio map yet of any star, other than the Sun. ALMA observed Antares close to its surface (its optical photosphere) in shorter wavelengths, and the longer wavelengths observed by the VLA revealed the star’s atmosphere further out. As seen in visible light, Antares’ diameter is approximately 700 times larger than the Sun. But when ALMA and the VLA revealed its atmosphere in radio light, the supergiant turned out to be even more gigantic.

“The size of a star can vary dramatically depending on what wavelength of light it is observed with,” explained Eamon O’Gorman of the Dublin Institute for Advanced Studies in Ireland and lead author of the study published in the June 16 edition of the journal Astronomy & Astrophysics. “The longer wavelengths of the VLA revealed the supergiant’s atmosphere out to nearly 12 times the star’s radius.”

The image to the right, cropped and reduced to post here, is what these two telescopes detected. As you can see, the outer atmosphere of the star is very uneven, confirming what other observations of both Antares and Betelgeuse has seen.

These stars are giant gasbags. It appears their shape fluctuates depending on the local “weather” in each star’s atmosphere.

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Lego Antikythera Mechanism

6:01 pm

An evening pause: From the youtube webpage:

The Antikythera Mechanism is the oldest known scientific computer, built in Greece at around 100 BCE. Lost for 2000 years, it was recovered from a shipwreck in 1901. But not until a century later was its purpose understood: an astronomical clock that determines the positions of celestial bodies with extraordinary precision. In 2010, we built a fully-functional replica out of Lego.

Hat tip Shaun Karry.

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New Horizons sees stellar parallax

3:04 pm

New Horizons is now far enough away from Earth that its perspective of the universe shifts at least two nearby stars into slightly different positions than seen on Earth.

On April 22-23, the spacecraft turned its long-range telescopic camera to a pair of the closest stars, Proxima Centauri and Wolf 359, showing just how they appear in different places than we see from Earth. Scientists have long used this “parallax effect” – how a star appears to shift against its background when seen from different locations — to measure distances to stars.

An easy way to see parallax is to place one finger at arm’s length and watch it jump back and forth when you view it successively with each eye. Similarly, as Earth makes it way around the Sun, the stars shift their positions. But because even the nearest stars are hundreds of thousands of times farther away than the diameter of Earth’s orbit, the parallax shifts are tiny, and can only be measured with precise instrumentation. “No human eye can detect these shifts,” Stern said.

But when New Horizons images are paired with pictures of the same stars taken on the same dates by telescopes on Earth, the parallax shift is instantly visible. The combination yields a 3D view of the stars “floating” in front of their background star fields.

The resulting 3D image, available at the link, is very cool. Both stars clearly appear closer than the surrounding background stars, which of course is true as they are among the closest stars to the Sun.

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NASA confirms Webb launch delayed again

9:16 am

NASA officials yesterday confirmed that, due to the new work conditions and the lock down imposed by the Wuhan flu panic, the launch of the James Webb Space telescope will not occur in March 2021.

“We will not launch in March,” said Thomas Zurbuchen, the space agency’s associate administrator for science. “Absolutely we will not launch in March. That is not in the cards right now. That’s not because they did anything wrong. It’s not anyone’s fault or mismanagement.”

Zurbuchen made these comments at a virtual meeting of the National Academies’ Space Studies Board. He said the telescope was already cutting it close on its schedule before the COVID-19 pandemic struck the agency and that the virus had led to additional lost work time. “This team has stayed on its toes and pushed this telescope forward at the maximum speed possible,” he said. “But we’ve lost time. Instead of two shifts fully staffed, we could not do that for all the reasons that we talk about. Not everybody was available. There were positive cases here and there (in the surrounding area, not on site). And so, perhaps, we had only one shift.”

No new target date has been set, though the comments even hinted that they might not be able to do it in 2021.

Webb will cost 20 times more than originally budgeted ($500 million vs $10 billion) and is now more than a decade behind schedule. In the process, those overages and delays wiped out almost all of NASA’s other astronomy projects during the 2010s.

But don’t worry! Once Webb launches the task of wiping out more astronomy projects with overages and delays will be courageously taken up by NASA’s Roman Space Telescope (formerly WFIRST), already behind schedule and over budget, and it is still only in the design phase.

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Rethinking the theories that explain some supernovae

10:30 am

The uncertainty of science: New data now suggests that the previous consensus among astronomers that type Ia supernovae were caused by the interaction of a large red giant star with a white dwarf might be wrong, and that instead the explosion might be triggered by two white dwarfs.

If this new origin theory turns out to be correct, then it might also throw a big wrench into the theory of dark energy.

The evidence that twin white dwarfs drive most, if not all, type Ia supernovae, which account for about 20% of the supernova blasts in the Milky Way, “is more and more overwhelming,” says Dan Maoz, director of Tel Aviv University’s Wise Observatory, which tracks fast-changing phenomena such as supernovae. He says the classic scenario of a white dwarf paired with a large star such as a red giant “doesn’t happen in nature, or quite rarely.”

Which picture prevails has impacts across astronomy: Type Ia supernovae play a vital role in cosmic chemical manufacturing, forging in their fireballs most of the iron and other metals that pervade the universe. The explosions also serve as “standard candles,” assumed to shine with a predictable brightness. Their brightness as seen from Earth provides a cosmic yardstick, used among other things to discover “dark energy,” the unknown force that is accelerating the expansion of the universe. If type Ia supernovae originate as paired white dwarfs, their brightness might not be as consistent as was thought—and they might be less reliable as standard candles.

If type Ia supernovae are not reliable standard candles, then the entire Nobel Prize results that discovered dark energy in the late 1990s are junk, the evidence used to discover it simply unreliable. Dark energy might simply not exist.

What galls me about this possibility is that it was always the case. The certainty in the 1990s about using type Ia supernovae as a standard candle to determine distance was entirely unjustified. Even now astronomers do not really know what causes these explosions. To even consider them to always exhibit the same energy release was just not reasonable.

And yet astronomers in the 1990s did, and thus they fostered the theory of dark energy upon us — that the universe’s expansion was accelerating over vast distances — while winning Nobel Prizes. They still might be right, and dark energy might exist, but it was never very certain, and still is not.

Much of the fault in this does not lie with the astronomers, but with the press, which always likes to sell new theories as a certainty, scoffing over the doubts and areas of ignorance that make the theories questionable. This is just one more example of this, of which I can cite many examples, the worst of all being the reporting about global warming.

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Exoplanet in Earth-like orbit circling Sun-type star

9:54 am

Worlds without end: Astronomers have found evidence suggesting the existence of an exoplanet about twice as massive as the Earth and orbiting a solar-twin star in an orbit almost the same as the Earth’s.

The star, Kepler-160, is about 3,000 light years away, and had previously discovered to have two exoplanets.

“Our analysis suggests that Kepler-160 is orbited not by two but by a total of four planets,” Heller summarizes the new study. One of the two planets that Heller and his colleagues found is Kepler-160d, the previously suspected planet responsible for the distorted orbit of Kepler-160c. Kepler-160d does not show any transits in the light curve of the star and so it has been confirmed indirectly. The other planet, formally a planet candidate, is KOI-456.04, probably a transiting planet with a radius of 1.9 Earth radii and an orbital period of 378 days. Given its Sun-like host star, the very Earth-like orbital period results in a very Earth-like insolation from the star – both in terms of the amount of the light received and in terms of the light color. Light from Kepler-160 is visible light very much like sunlight. All things considered, KOI-456.04 sits in a region of the stellar habitable zone – the distance range around a star admitting liquid surface water on an Earth-like planet – that is comparable to the Earth’s position around the Sun.

“KOI-456.01 is relatively large compared to many other planets that are considered potentially habitable. But it’s the combination of this less-than-double the size of the Earth planet and its solar type host star that make it so special and familiar,” Heller clarifies. As a consequence, the surface conditions on KOI-456.04 could be similar to those known on Earth, provided its atmosphere is not too massive and non-Earth-like. The amount of light received from its host star is about 93 percent of the sunlight received on Earth. If KOI-456.04 has a mostly inert atmosphere with a mild Earth-like greenhouse effect, then its surface temperature would be +5 degrees Celsius on average, which is about ten degrees lower than the Earth’s mean global temperature.

These results have many uncertainties, so we should not be surprised if further research produces significant revisions in these conclusions. Nonetheless, the number of Earth-like planets orbiting Sun-like stars in orbits like the Earth’s continues to rise.

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Second exoplanet confirmed orbiting Proxima Centauri

12:51 pm

Worlds without end: Using archived Hubble data, astronomers have now independently confirmed the existence of a second exoplanet orbiting the nearest star, Proxima Centauri.

Dubbed Proxima c, this is not the same Earth-sized exoplanet confirmed to orbit the star last week. That planet, Proxima b, orbits close to the star every 11.2 days. The new planet is much farther out.

Benedict found a planet with an orbital period of about 1,907 days buried in the 25-year-old Hubble data. This was an independent confirmation of the existence of Proxima Centauri c.

Shortly afterward, a team led by Raffaele Gratton of INAF published images of the planet at several points along its orbit that they had made with the SPHERE instrument on the Very Large Telescope in Chile.

Benedict then combined the findings of all three studies: his own Hubble astrometry, Damasso’s radial velocity studies, and Gratton’s images to greatly refine the mass of Proxima Centauri c. He found that the planet is about 7 times as massive as Earth.

Though I am unaware of any hints of additional planets orbiting Proxima Centauri, the presence of two strongly implies the likelihood of more.

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