Tag: astronomy

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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