Tag: astronomy

A stellar interloper in the Milky Way?

10:16 am

The uncertainty of science: Astronomers have identified a star inside the Milky Way whose chemical compositions suggests it was formed and originally came from a nearby dwarf galaxy.

This is the first discovery of a star having such extreme abundance ratios among Milky Way stars. On the other hand, several examples of stars having similar abundance ratios are known in dwarf galaxies. This result suggests that this star has formed in a dwarf galaxy, and has accreted onto the Milky Way in the process of galaxy formation. The abundance ratios of this star provide the clearest signature of merger events of dwarf galaxies in stellar chemical abundances known to date.

Though presently unique, this star probably is not the only such interloper in the Milky Way. It is believed by astronomers that our galaxy has absorbed a number of dwarf galaxies as it formed and grew, so we should expect more such stars to be discovered with time.

At the same time, we also must exercise some skepticism. Our understanding of galaxy formation is very preliminary, and thus the astronomers might be assuming too much about the chemical composition of dwarf galaxies in coming to this conclusion.

Posted at Los Angeles Airport on my way to Cannon Beach, Oregon, for a short vacation with friends.

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New Hubble data baffles cosmologists about universe’s expansion rate

10:15 am

The uncertainty of science: New and very firm data from the Hubble Space Telescope on the universe’s expansion rate conflicts with just-as-firm data obtained by Europe’s Planck astronomical probe.

According to Planck, the present universe should be expanding at a rate of 67 kilometers per second per megaparsec. According to Hubble, the actual expansion rate is 74 kilometers per second per megaparsec.

And according to the scientists involved, both data sets are reliable and trustworthy, leaving them baffled at the difference.

“This is not just two experiments disagreeing,” explained [lead researcher and Nobel laureate Adam Riess of the Space Telescope Science Institute (STScI) and Johns Hopkins University, in Baltimore, Maryland.] “We are measuring something fundamentally different. One is a measurement of how fast the universe is expanding today, as we see it. The other is a prediction based on the physics of the early universe and on measurements of how fast it ought to be expanding. If these values don’t agree, there becomes a very strong likelihood that we’re missing something in the cosmological model that connects the two eras.”

Ya think? Any cosmologist who claims we really understand what is going on, based on our present fragile and very limited knowledge, is either fooling him or herself or is trying to fool us.

I should note that there seems to be an effort, based on the press release above as well as this second one, to downplay the amount of uncertainties that exist in this cosmological work. Both releases fail to note that when scientists announced their first expansion rate estimate from Hubble’s first data back in 1995, those scientists claimed with absolute certainty that the expansion rate was 80 kilometers per second per megaparsec. At the time some scientists, led by the late Allan Sandage of the Carnegie Observatory, disputed this high number, claiming the number could be as low as 50. Some even said it could be as low as 30 kilometers. Sandage especially found himself poo-pooed by the cosmological community for disputing that the 80 number pushed by Hubble’s scientists in 1995.

In the end, the Hubble scientists in 1995 were closer to today’s Hubble number than Sandage, but his estimate was not wrong by that much more, and he was right when he said the number had to be lower. Either way, Hubble’s modern estimate of 74 for the present expansion rate is very well constrained, and is a far more trustworthy number than previous estimates.

However, do we know with any reliability what the expansion rate was billions of years ago? No. Cosmologists think it was faster, based on supernovae data, which is where the theory of dark energy comes from. It is also where Planck’s predictions come from.

That early expansion rate, however, is based on such tentative data, containing so many assumptions and such large margins of error, that no serious scientist should take it too seriously. It suggests things, but it certainly doesn’t confirm them.

This is why their faith in the numbers derived from Planck puzzles me. It is based on a “prediction,” as Riess admits in the quote above, which means it is based on a theoretical model. It is also based on that very tentative early supernovae data, which makes it very suspect to me.

The Hubble data is real data, obtained by looking at nearby stars in a very precise matter. Its margin of error is very small. It contains only a few assumptions, mostly involving our understanding of the Cepheid variable stars that Hubble observed. While skepticism is always called for, trusting this new Hubble data more is perfectly reasonable.

In the end, to really solve this conflict will require better data from the early universe. Unfortunately, that is not something that will be easy to get.

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Hubble celebrates 29 years in orbit

10:01 am

Hubble's 29th anniversary image

Click for full image.

In celebration of the 29th anniversary of the launch of the Hubble Space Telescope, the Space Telescope Science Institute (STScI) that operates the telescope has released a new image of one of the more spectacular astronomical objects in the southern hemisphere, what astronomers have dubbed the Southern Crab Nebula. I have cropped and reduced the image slightly to post it to the right.

The nebula, officially known as Hen 2-104, is located several thousand light-years from Earth in the southern hemisphere constellation of Centaurus. It appears to have two nested hourglass-shaped structures that were sculpted by a whirling pair of stars in a binary system. The duo consists of an aging red giant star and a burned-out star, a white dwarf. The red giant is shedding its outer layers. Some of this ejected material is attracted by the gravity of the companion white dwarf.

The result is that both stars are embedded in a flat disk of gas stretching between them. This belt of material constricts the outflow of gas so that it only speeds away above and below the disk. The result is an hourglass-shaped nebula.

The bubbles of gas and dust appear brightest at the edges, giving the illusion of crab leg structures. These “legs” are likely to be the places where the outflow slams into surrounding interstellar gas and dust, or possibly material which was earlier lost by the red giant star.

The outflow may only last a few thousand years, a tiny fraction of the lifetime of the system. This means that the outer structure may be just thousands of years old, but the inner hourglass must be a more recent outflow event. The red giant will ultimately collapse to become a white dwarf. After that, the surviving pair of white dwarfs will illuminate a shell of gas called a planetary nebula.

Hubble first revealed this nebula’s shape in a photograph taken in 1999.

The telescope was initially designed for a fifteen year mission. It is about to double that, assuming its last remaining gyroscopes can hold on through next year.

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Five exoplanets discovered with orbits from 15 to 40 years long

9:30 am

Twenty years of observations have now resulted in the discovery of five exoplanets with long solar orbits ranging from 15 to 40 years.

“As early as 1998, a planetary monitoring programme was set up and carried out scrupulously by the many … observers [using the EULER telescope belonging to Geneva University, Switzerland,] who took turns every two weeks in La Silla [Chile] for 20 years”, says Emily Rickman. The result is remarkable: five new planets have been discovered and the orbits of four others known have been precisely defined. All these planets have periods of revolution between 15.6 and 40.4 years, with masses ranging approximately from 3 to 27 times that of Jupiter. This study contributes to increasing the list of 26 planets with a rotation period greater than 15 years.

The press release is very poorly written. It does not explain how 21 years of observations pinpointed the orbit of an exoplanet of forty years. I suspect they have seen enough of the star’s wobble to extrapolate that orbit, but the press release should have explained this.

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Did an interstellar meteor hit the Earth in 2014?

5:55 am

By analyzing the speed in which it traveled through the atmosphere, astronomers propose that a meteor that hit the ground in 2014 was probably an interstellar object.

The scientists analyzed the Center for Near-Earth Object Studies’ catalog of meteor events detected by U.S. government sensors. They focused on the fastest meteors, because a high speed suggests a meteor is potentially not gravitationally bound to the sun and thus may originate from outside the solar system.

The researchers identified a meteor about 3 feet (0.9 meters) wide that was detected on Jan. 8, 2014, at an altitude of 11.6 miles (18.7 kilometers) over a point near Papua New Guinea’s Manus Island in the South Pacific. Its high speed of about 134,200 mph (216,000 km/h) and its trajectory suggested it came from outside the solar system, the scientists said. “We can use the atmosphere of the Earth as the detector for these meteors, which are too small to otherwise see,” Loeb told Space.com.

The meteor’s velocity suggested it received a gravitational boost during its journey, perhaps from the deep interior of a planetary system, or a star in the thick disk of the Milky Way.

To put it mildly, there are a lot of uncertainties about this conclusion. Nonetheless, their approach and hypothesis is very intriguing, and seems logical.

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Tess finds Earth-sized planet?

9:24 am

Scientists using the space telescope TESS think they may have found its first Earth-sized planet.

Its host star has about 80 percent of the mass of our Sun and is found about 53 light-years distant from Earth. HD 21749b has about 23 times Earth’s mass and a radius of about 2.7 times Earth’s. Its density indicates the planet has substantial atmosphere but is not rocky, so it could potentially help astronomers understand the composition and evolution of cooler sub-Neptune planet atmospheres.

Excitingly, the longer period sub-Neptune planet in this system is not alone. It has a sibling planet, HD 21749c, which takes about eight days to orbit the host star and is much smaller—similar in size to Earth. “Measuring the exact mass and composition of such a small planet will be challenging, but important for comparing HD 21749c to Earth,” said Wang. “Carnegie’s PFS team is continuing to collect data on this object with this goal in mind.”

In other words, they know almost nothing yet about the smaller exoplanet. They think it is similar in size to the Earth, but they don’t know its mass or composition.

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Astronomers take highest resolution radio image of black hole

9:54 am

shadow of black hole

Using a network of ground-based radio telescopes astronomers today released the highest resolution radio image of black hole ever produced.

Before giving more details, I must correct every other news report, as well as all of the press releases about this image. It is not “The first image of a black hole!” as these releases are claiming breathlessly. Radio telescope arrays have taken such images in the past, but their resolution was poor, so the result was not very imagelike. Instead, it showed contour lines in a coarse manner. Moreover, the coarseness of the resolution prevented them from seeing the black hole’s shadow itself.

This image now produced has the highest resolution ever for such a radio image, but believe me, it is still coarse. Nonetheless, it represents a giant technological leap forward. The effort required upgrades to many of these telescopes, along with significantly improved computer analysis. Now for some details:

Black holes are extraordinary cosmic objects with enormous masses but extremely compact sizes. The presence of these objects affects their environment in extreme ways, warping spacetime and super-heating any surrounding material. “If immersed in a bright region, like a disc of glowing gas, we expect a black hole to create a dark region similar to a shadow — something predicted by Einstein’s general relativity that we’ve never seen before,” explained chair of the EHT Science Council Heino Falcke of Radboud University, the Netherlands. “This shadow, caused by the gravitational bending and capture of light by the event horizon, reveals a lot about the nature of these fascinating objects and allowed us to measure the enormous mass of M87’s black hole.”

The image reveals the black hole at the center of Messier 87, a massive galaxy in the nearby Virgo galaxy cluster. This black hole resides 55 million light-years from Earth and has a mass 6.5-billion times that of the Sun.

…Multiple calibration and imaging methods have revealed a ring-like structure with a dark central region — the black hole’s shadow — that persisted over multiple independent EHT observations. “Once we were sure we had imaged the shadow, we could compare our observations to extensive computer models that include the physics of warped space, superheated matter and strong magnetic fields. Many of the features of the observed image match our theoretical understanding surprisingly well,” remarks Paul T.P. Ho, EHT Board member and Director of the East Asian Observatory. “This makes us confident about the interpretation of our observations, including our estimation of the black hole’s mass.” [emphasis mine]

Note the highlighted words. To create this image they needed to combine data from numerous radio telescopes. Such work requires extensive calibration. The resulting image is manufactured, though without doubt it is manufactured from real radio data accumulated by multiple telescopes. Because those telescopes are separated by distance, however, there will always be gaps between their images, and it is in the calibration and imaging methods that the gaps are extrapolated away.

I don’t wish to imply that this image is fake. It is not. That the features persisted over multiple observations confirms that they were actually seeing the black hole’s shadow. It also confirms that these new interferometry techniques work.

However, much of the press hyperbole today is an effort to justify the many millions in tax dollars spent on this effort. The effort was absolutely worthwhile scientifically, but government bureaucracies always feel a need to oversell their work. That is partly what is happening here.

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Fragment of a long dead planet’s iron core found orbiting white dwarf

8:25 am

Astronomers have identified the fragment of a long dead planet’s iron core orbiting a white dwarf star 410 light years away.

The [data] suggested its source was a solid object some 600 kilometers across—a suspected planetary core, with a density between 7.7 and 39 grams per cubic meter, comparable to the pure iron found within Earth’s core. “The density of the piece of rock is consistent with what we think the cores of planets [are],” says Luca Fossati of the Austrian Academy of Sciences, who was not involved in the paper.

It orbits the star every two hours, the fastest exoplanet orbit yet found. This alone should rip it apart, providing further evidence that the object’s density is very high.

The astronomers theorize that this object is likely the remains of a planet that existed when this star was young, and was destroyed as the star aged to become a red giant, expanding to swallow it. Later, when the star collapsed to become a tiny white dwarf, the core remained, its density allowing it survive as the planet’s outer crust was torn away.

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Telescope store sues Asian telescope manufacturers for fixing prices

11:21 am

A San Francisco store that sells telescopes to the public is suing two Asian telescope manufacturers — who make almost all recreational telescopes sold in the U.S. — for conspiring together to fix prices and create that monopoly.

Orion Telescopes and Binoculars, which is headquartered in Watsonville and has stores there and in Cupertino, is seeking more than $180 million in damages in a lawsuit. A federal court in Northern California said the complaint against telescope maker Ningbo Sunny, filed in 2016, can go to trial. A subsidiary of Ningbo Sunny, a Chinese company, bought Irvine telescope maker Meade Instruments in 2013.

In the complaint, Orion alleges that Ningbo Sunny and a Taiwanese telescope manufacturer, Synta Technology, shared confidential information that competitors normally would not share, including product pricing, order forecasts and credit arrangements.

My question is this: Why are no American telescope manufacturers competing in this market? Are our labor costs too high? Our government regulations too restrictive? A little bit of competition could easily end this collusion by these Asian manufacturers, assuming it is happening.

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Hubble’s main camera resumes science work

8:41 am

The main camera on the Hubble Space Telescope has resumed science operations after going into safe mode last week.

At 8:31 p.m. EST on Feb. 28, the Advanced Camera for Surveys aboard NASA’s Hubble Space Telescope suspended operations after an error was detected as the instrument was performing a routine boot procedure. The error indicated that software inside the camera had not loaded correctly in a small section of computer memory. The Hubble operations team ran repeated tests to reload the memory and check the entire process. No errors have been detected since the initial incident, and it appears that all circuits, computer memory and processors that are part of that boot process are now operating normally. The instrument has now been brought back to its standard operating mode for normal operations.

From the press release, it appears that they have not been able to trace why the error occurred. However, much like a typical Windows computer, after a mysterious crash and reboot now all appears well, so they have shrugged their shoulders and moved on.

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New analysis suggests photon could make dark matter unnecessary

1:28 pm

The uncertainty of science: A new analysis by physicists that assumes a very very low mass for the photon, the particle that transmits light, could very well explain the motions of stars in galaxies and make dark matter unnecessary.

Professor Dmitri Ryutov, who recently retired from the Lawrence Livermore National Laboratory in California, USA, is an expert in plasma physics. He was awarded the American Physical Society’s (APS) 2017 Maxwell Prize for Plasma Physics for his achievements in the field. Physicists generally credit Ryutov with establishing the upper limit for the mass of the photon. As this mass, even if it is nonzero, is extremely small, it is usually ignored when analyzing atomic and nuclear processes. But even a vanishingly tiny mass of the photon could, according to the scientists’ collaborative proposal, have an effect on large-scale astrophysical phenomena.

While visiting Johannes Gutenberg University Mainz (JGU), Ryutov, his host Professor Dmitry Budker of the Helmholtz Institute Mainz (HIM), and Professor Victor Flambaum, Fellow of the Gutenberg Research College of Mainz University, decided to take a closer look at the idea. They were interested in how the infinitesimally small mass of the photon could have an effect on massive galaxies. The mechanism at the core of the physicists’ assumption is a consequence of what is known as Maxwell-Proca equations. These would allow additional centripetal forces to be generated as a result of the electromagnetic stresses in a galaxy.

Are the effects as strong as those exerted by dark matter?

“The hypothetical effect we are investigating is not the result of increased gravity,” explained Dmitry Budker. This effect may occur concurrently with the assumed influence of dark matter. It may even – under certain circumstances – completely eliminate the need to evoke dark matter as a factor when it comes to explaining rotation curves. Rotation curves express the relationship between the orbital speeds of stars in a galaxy and their radial distance from the galaxy’s center. “By assuming a certain photon mass, much smaller than the current upper limit, we can show that this mass would be sufficient to generate additional forces in a galaxy and that these forces would be roughly large enough to explain the rotation curves,” said Budker. “This conclusion is extremely exciting.” [emphasis mine]

They readily admit that this first analysis is very preliminary, and causes some additional theoretical problems that conflict with known data. Nonetheless, this simple idea could eliminate the need for the additional dark matter particle that physicists have had trouble explaining or even finding.

In fact, I am somewhat baffled why physicists had not proposed this decades ago. It provides a much more straightforward explanation for the higher rotational curves in the outer parts of galaxies, and does not require any new physics.

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Hubble’s main camera down

1:36 pm

The main camera on the Hubble Space Telescope has suspended operations, and remains so as engineers troubleshoot the problem.

According to NASA, at 8:31 p.m. EST Feb. 28 (01:31 GMT March 1), 2019, the Advanced Camera for Surveys, or ACS, suspended its operations when an error was detected while the instrument was performing a routine boot procedure. “The error indicated that software inside the camera had not loaded correctly,” a statement from NASA reads. “A team of instrument system engineers, flight software experts and flight operations personnel quickly organized to download and analyze instrument diagnostic information.

They have not yet pinpointed the cause of the problem. The telescope has other cameras, however, though one of which had problems several months ago.

It is ten years since the last shuttle repair mission. That mission was expected to extend the telescope’s life for five years. Thus, the end Hubble’s life is getting closer and closer.

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Scientists confirm first exoplanet candidate found by Kepler

1:07 pm

Worlds without end: Ten years after Kepler was launched into space to find exoplanets, astronomers have finally confirmed one of the space telescopes thousands of candidates.

Despite being the very first planet candidate discovered by NASA’s Kepler Space Telescope, the object now known as Kepler-1658 b had a rocky road to confirmation. The initial estimate of the size of the planet’s host star was incorrect, so the sizes of both the star and Kepler-1658 b were vastly underestimated. It was later set aside as a false positive when the numbers didn’t quite make sense for the effects seen on its star for a body of that size. Fortuitously, Chontos’ first year graduate research project, which focused on re-analyzing Kepler host stars, happened at just the right time.

“Our new analysis, which uses stellar sound waves observed in the Kepler data to characterize the host star, demonstrated that the star is in fact three times larger than previously thought. This in turn means that the planet is three times larger, revealing that Kepler-1658 b is actually a hot Jupiter-like planet,” said Chontos. With this refined analysis, everything pointed to the object truly being a planet, but confirmation from new observations was still needed.

“We alerted Dave Latham (a senior astronomer at the Smithsonian Astrophysical Observatory, and co-author on the paper) and his team collected the necessary spectroscopic data to unambiguously show that Kepler-1658 b is a planet,” said Dan Huber, co-author and astronomer at the University of Hawaiʻi. “As one of the pioneers of exoplanet science and a key figure behind the Kepler mission, it was particularly fitting to have Dave be part of this confirmation.”

It is important to remember that until scientists obtain independent data on each of these candidates, they are not yet confirmed as exoplanets, and might only be false positives. To do this, however, is going to take a lot of work and time.

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No laser communications system at Tabby’s Star

10:32 am

If alien megastructures exist at Tabby’s Star, new research has precluded the likelihood that those aliens are using lasers for communications within those gigantic structures.

[The scientists checked] for laser signatures, on the not unreasonable grounds that any structure large enough to encase a star – Boyajian [Tabby’s Star] is almost one-and-a-half times the mass of the sun – would have an internal communication system, for which lasers would represent a good candidate medium.

In the latest research, Lipman and colleagues decided to test the idea. They analysed 177 high-resolution spectra from the star, gathered by the Lick Observatory’s Automated Planet Finder telescope as part of the Breakthrough Listen Project. They estimated that the data was so detailed that lasers with power greater than 24 megawatts should show up. To hunt for them, the researchers developed an algorithm to perform a pixel-by-pixel analysis of each spectrum in order to identify “spatially unresolved emission lines that meet the criteria for an artificial laser signal”.

The good news is that they found several. The bad news is that a secondary multi-step analysis designed to pick up false positives discounted them all. “The top candidates from the analysis can all be explained as either cosmic ray hits, stellar emission lines or atmospheric air glow emission lines,” they conclude.

We must remember that alien megastructures are the most unlikely explanation for the random light fluctuations of Tabby’s Star. This research helps to strengthen that conclusion.

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Astronomer discovers newest farthest solar system object

8:16 am

Worlds without end: An astronomer leading a team looking for a large planet beyond Pluto has broken their own record and found a new solar system object that is the farthest known from the Sun.

That’s when he saw it, a faint object at a distance 140 times farther from the sun than Earth — the farthest solar system object yet known, some 3.5 times more distant than Pluto. The object, if confirmed, would break his team’s own discovery, announced in December, of a dwarf planet 120 times farther out than Earth, which they nicknamed “Farout.” For now, they are jokingly calling the new object “FarFarOut”. “This is hot off the presses,” he said during his rescheduled talk on 21 February.

I like the names for both.

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New sky survey uncovers hundreds of thousands of previously unknown galaxies

11:02 am

Galaxies without end: A new radio telescope sky survey has discovered hundreds of thousands of previously unknown galaxies.

This discovery is part of a major release of papers outlining a number of discoveries made by this new sky survey.

I could of course also subheaded this post “The uncertainty of science.” Wanna bet that even with this discovery we have only seen the tip of the iceberg of the number of galaxies out there?

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A very old white dwarf star with rings?

10:19 am

The uncertainty of science: A citizen scientist has discovered a very old white dwarf star that apparently has one or more dust rings it should not have.

The star, LSPM J0207+3331 or J0207 for short, is forcing researchers to reconsider models of planetary systems and could help us learn about the distant future of our solar system. “This white dwarf is so old that whatever process is feeding material into its rings must operate on billion-year timescales,” said John Debes, an astronomer at the Space Telescope Science Institute in Baltimore. “Most of the models scientists have created to explain rings around white dwarfs only work well up to around 100 million years, so this star is really challenging our assumptions of how planetary systems evolve.”

In other words, we don’t really yet understand the processes that form solar systems or even stars. This isn’t because we can’t figure this out, but because we don’t yet have enough information on hand. What we do know tells us that stars and solar systems both form from accretion disks. The information also gives us a general idea of the pattern of formation, but not much more.

For example, one question I have asked a number of astronomers is: Why are some stars gigantic monsters and others dwarfs? Based on present theories of stellar evolution, it seems to me that all stars should be the same size, as accretion is thought to end when the star reaches a heavy enough mass to ignite its nuclear engine. Yet this is not what we find. Why? I’ve never gotten a good answer.

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IAU approves China’s proposed names for Chang’e-4 landing site

10:07 am

That was fast! The International Astronomical Union (IAU) has approved all of the proposed names that China submitted for the features at or near Chang’e-4 landing site.

The IAU Working Group for Planetary System Nomenclature has approved the name Statio Tianhe for the landing site where the Chinese spacecraft Chang’e-4 touched down on 3 January this year, in the first-ever landing on the far side of the Moon. The name Tianhe originates from the ancient Chinese name for the Milky Way, which was the sky river that separated Niulang and Zhinyu in the folk tale “The Cowherd and the Weaver Girl”.

Four other names for features near the landing site have also been approved. In keeping with the theme of the above-mentioned folk tale, three small craters that form a triangle around the landing site have been named Zhinyu, Hegu, and Tianjin, which correspond to characters in the tale. They are also names of ancient Chinese constellations from the time of the Han dynasty. The fifth approved name is Mons Tai, assigned to the central peak of the crater Von Kármán, in which the landing occurred. Mons Tai is named for Mount Tai, a mountain in Shandong, China, and is about 46 km to the northwest of the Chang’e-4 landing site.

Compare this fast action with the IAU’s approval process for the names the New Horizons team picked for both Pluto and Ultima Thule. It took the IAU more than two years to approve the Pluto names, and almost three years to approve the Charon names. It is now almost two months after New Horizons’ fly-by of Ultima Thule, and the IAU has not yet approved the team’s picks for that body.

Yet it is able to get China’s picks approved in less than a month? Though it is obviously possible that there is a simple and innocent explanation for the differences here, I think this illustrates well the biases of the IAU. Its membership does not like the United States, and works to stymie our achievements if it can. This factor played a part in the Pluto/planet fiasco. It played a part in its decision to rename Hubble’s Law. And according to my sources, it was part of the background negotiations in the naming of some lunar craters last year to honor the Apollo 8 astronauts.

The bottom line remains: The IAU has continually tried to expand its naming authority, when all it was originally asked to do was to coordinate the naming of distant astronomical objects. Now it claims it has the right to approve the naming of every boulder and rock anywhere in the universe. At some point the actual explorers are going to have to tell this organization to go jump in a lake.

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Asteroid to eclipse Sirius, the sky’s brightest star, on February 18

8:46 am

On February 18, 2019 a four-mile wide asteroid is going to pass in front of Sirius, the sky’s brightest star, and block its light for just under two seconds.

Can a 7-kilometer-wide asteroid make Sirius disappear? You bet it can. That just might happen on Monday night, February 18th. That evening around 10:30 p.m. MST (5:30 UT February 19th), there’s a good probability that the 17th-magnitude 4388 Jürgenstock will occult the sky’s brightest star for up to 1.8 seconds. Visibility stretches along a narrow path from the southern tip of Baja California to the Las Cruces–El Paso region, up through the Great Plains, and north to the Winnipeg area. While only a limited number of people may see this event, anytime Sirius disappears, however briefly, it’s news!

In the U.S. the narrow path cuts through New Mexico, Colorado, Nebraska, South Dakota, and North Dakota. If you live in or near this path, this is definitely worth watching, especially since it will be happening at a convenient hour in the evening.

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Recent Cuba meteorite estimated to have weighed about 360 tons

1:36 pm

Using its imaged track from several sources, scientists have now estimated the size and weight of the recent spectacular fireball over Cuba as being several meters across and weighing about 360 tons.

After reconstructing the trajectory in the atmosphere, the Colombian astronomers “played back” the impact and found that the culprit, a rock with an estimated size of several meters and a weight of about 360 tons, came from an eccentric orbit around the Sun with an average distance to our star of 1.3 astronomical units (1 astronomical-unit = 150 million km). Before impacting the Earth, the rock completed a turn around the Sun every 1.32 years. All that came to an end on February 1, 2019 when both, the rock and the Earth, found themselves at the same point in space, at the same time. The worse part was for the rock!

The article spends most of its time selling a computer model the scientists have developed that they claim can predict the approach trajectory of meteorites, something I find quite unconvincing. However, the result above is important for different reasons. Routinely astronomers today discover new small asteroids just days before they zoom harmlessly past the Earth. Each time one of these new near Earth asteroids is found, the press automatically goes into “Chicken Little mode,” suggesting that should this object have hit the Earth it would have caused massive damage.

Most of these newly discovered asteroids are about the same size as the Cuba meteorite, if not smaller. Thus, this meteorite gives us a clear idea of how completely harmless these other near Earth asteroids are. In fact, this impact suggests to me that in most cases an asteroid would have to be about ten times larger to pose a significant threat.

Keep this number — 360 tons — in mind the next time another near Earth asteroid is discovered.

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Rare asteroid orbiting near Venus discovered

11:51 am

The Zwicky Transient Facility (ZTF), a new sky survey telescope whose main goal is to find Near Earth asteroids, has discovered a rare asteroid orbiting near Venus.

A state-of-the-art sky-surveying camera, the Zwicky Transient Facility, or ZTF, detected the asteroid on January 4, 2019. Designated 2019 AQ3, the object has the shortest “year” of any recorded asteroid, with an orbital period of just 165 days. It also appears to be an unusually big asteroidal specimen. “We have found an extraordinary object whose orbit barely strays beyond Venus’ orbit—that’s a big deal,” said Quanzhi Ye, a postdoctoral scholar at IPAC, a data and science center for astronomy at Caltech. Ye called 2019 AQ3 a “very rare species,” further noting that “there might be many more undiscovered asteroids out there like it.”

…The orbit, as it turns out, is angled vertically, taking 2019 AQ3 above and below the plane where the planets run their laps around the sun. Over its short year, 2019 AQ3 plunges inside of Mercury, then swings back up just outside of Venus’ orbit.

The telescope, in operation since March 2018, and so far found

nearly 60 new near-Earth asteroids. Two of these were spotted in July 2018 mere hours before they gave Earth quite a close shave. Designated 2018 NW and 2018 NX, the duo of bus-sized asteroids whipped past at a distance of about 70,000 miles, or only a third of the way to the moon. Fortunately, the newfound 2019 AQ3 poses no threat; the closest it ever comes to Earth is about 22 million miles.

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New Hubble images of Uranus and Neptune

9:28 am

Uranus (top) and Neptune

The Hubble Space Telescope’s new annual images of Uranus (top) and Neptune (bottom) has revealed new atmospheric features for both, a giant north pole cloud cap on Uranus and a new dark storm developing on Neptune.

For Neptune:

The new Hubble view of Neptune shows the dark storm, seen at top center. Appearing during the planet’s southern summer, the feature is the fourth and latest mysterious dark vortex captured by Hubble since 1993. Two other dark storms were discovered by the Voyager 2 spacecraft in 1989 as it flew by the remote planet. Since then, only Hubble has had the sensitivity in blue light to track these elusive features, which have appeared and faded quickly. A study led by University of California, Berkeley, undergraduate student Andrew Hsu estimated that the dark spots appear every four to six years at different latitudes and disappear after about two years.

Hubble uncovered the latest storm in September 2018 in Neptune’s northern hemisphere. The feature is roughly 6,800 miles across.

For Uranus:

The snapshot of Uranus, like the image of Neptune, reveals a dominant feature: a vast bright cloud cap across the north pole.

Scientists believe this feature is a result of Uranus’ unique rotation. Unlike every other planet in the solar system, Uranus is tipped over almost onto its side. Because of this extreme tilt, during the planet’s summer the Sun shines almost directly onto the north pole and never sets. Uranus is now approaching the middle of its summer season, and the polar-cap region is becoming more prominent. This polar hood may have formed by seasonal changes in atmospheric flow.

The images are part of an annual program that monitors both planets with images every year when the Earth is best placed to view them. This allows scientists to track atmospheric changes over time.

The sharpness of both images matches that of previous Hubble images, so these photographs do not show any decline in the telescope’s image capability. However, when they lose that next gyroscope and shift to one gyroscope mode, I believe it will be very difficult to get images even this sharp of the outer planets. In fact, I suspect this monitoring program will likely have to end, or will be badly crippled.

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The Milky Way is warped?

8:39 am

The uncertainty of science: Distance data of more than 1,300 Cepheid variable stars gathered by the Wide-field Infrared Explorer (WISE) space telescope now suggests to astronomers that the disk of the Milky Way galaxy is warped.

Trying to determine the real shape of our galaxy is like standing in a Sydney garden and trying to determine the shape of Australia. But, for the past 50 years there have been indications that the hydrogen clouds in the Milky Way are warped. The new map shows that the warped Milky Way disc also contains young stars. It confirms that the warped spiral pattern is caused by torque from the spinning of the Milky Way’s massive inner disc of stars.

This research is good and helpful in getting us closer to a real picture of our Milky Way galaxy. However, need I say that this result carries with it a great deal of uncertainty? Or should I let my kind readers outline for me the many aspects of this research that leave me with doubts?

I think I want to do the latter. Where do you think the uncertainties are in this research? What assumptions are they making? Where is their data sparse or weak? Feel free to list them in the comments.

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China’s unsupervised radio antenna in Argentina

12:01 pm

A Chinese invasion? A Chinese radio antenna in Argentina, initially proposed as a communications facility for use with China’s space program, operates without any supervision by the Argentinian government and appears to have military links.

Though U.S. government officials are pushing the idea that this facility is being used by China to eavesdrop on foreign satellites, and though China’s space program is without doubt a major arm of its military, I doubt the radio antenna is being put to military use. As the story notes

Tony Beasley, director of the U.S. National Radio Astronomy Observatory, said the station could, in theory, “listen” to other governments’ satellites, potentially picking up sensitive data. But that kind of listening could be done with far less sophisticated equipment. “Anyone can do that. I can do that with a dish in my back yard, basically,” Beasley said. “I don’t know that there’s anything particularly sinister or troubling about any part of China’s space radio network in Argentina.”

It was installed to support China’s effort to send spacecraft to the Moon and Mars, and that is likely its main purpose. China does not wish to be dependent on the U.S.’s Deep Space Network for such interplanetary communications. This facility helps make that independence possible.

At the same time, the fact that China has been allowed to establish a remote facility in another country and operate it with no oversight is definitely an issue of concern. Essentially, China has obtained control over a piece of Argentinian territory, and unless the Argentine government takes action, China can do whatever it wants there. While the antenna itself might not be an issue, the facility itself is.

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The unfinished search for the Hubble constant

10:40 am

The uncertainty of science: Scientists continue to struggle in their still unfinished search for determining the precise expansion rate for the universe, dubbed the Hubble constant in honor of Edwin Hubble, who discovered that expansion.

The problem is, the values obtained from [two different] methods do not agree—a discrepancy cosmologists call “tension.” Calculations from redshift place the figure at about 73 (in units of kilometers per second per megaparsec); the CMB estimates are closer to 68. Most researchers first thought this divergence could be due to errors in measurements (known among astrophysicists as “systematics”). But despite years of investigation, scientists can find no source of error large enough to explain the gap.

I am especially amused by these numbers. Back in 1995 NASA had a big touted press conference to announce that new data from the Hubble Space Telescope had finally determined the exact number for the Hubble constant, 80 (using the standard above). The press went hog wild over this now “certain” conclusion, even though other astronomers disputed it, and offered lower numbers ranging from 30 to 65. Astronomer Allan Sandage of the Carnegie Observatories was especially critical of NASA’s certainty, and was dully ignored by most of the press.

In writing my own article about this result, I was especially struck during my phone interview with Wendy Friedman, the lead scientist for Hubble’s results, by her own certainty. When I noted that her data was very slim, the measurements of only a few stars from one galaxy, she poo-pooed this point. Her result had settled the question!

I didn’t buy her certainty then, and in my article, for The Sciences and entitled most appropriately “The Hubble Inconstant”, made it a point to note Sandage’s doubts. In the end it turns out that Sandage’s proposed number then of between 53 and 65 was a better prediction.

Still, the science for the final number remains unsettled, with two methods coming up with numbers that are a little less than a ten percent different, and no clear explanation for that difference. Isn’t science wonderful?

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Moon hit by small meteorite during eclipse

12:57 pm

During the lunar eclipse two days ago on January 20, 2018 amateur astronomers were able to record the impact of a small meteorite.

The MIDAS survey is a Moon-watching that scours video of its surface in the hopes of detecting the tiny flashes associated with meteorite impacts. In this case, MIDAS scored a home run, and it was the first time the system was able to spot an impact during a total lunar eclipse.

“In total I spent almost two days without sleeping, including the monitoring time during the eclipse,” [Jose] Madiedo explained to Gizmodo. “I was exhausted when the eclipse ended—but when the automatic detection software notified me of a bright flash, I jumped out of my chair. It was a very exciting moment because I knew such a thing had never been recorded before.”

The meteorite itself wasn’t terribly large, and is estimated to have only been around 22 pounds.

I have embedded the video of the impact below the fold. It is very short, and the flash is not very impressive, but it still is quite cool.
» Read more

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Is the pole of the Milky Way’s central black hole pointing directly at us?

9:42 am

The uncertainty of science: New data obtained using a constellation of Earth-based telescopes, working as a unit, strongly suggests that the pole of the Milky Way7s supermassive central black hole, dubbed Sagittarius A* (pronounced A-star), is pointing directly at us.

The high quality of the unscattered image has allowed the team to constrain theoretical models for the gas around Sgr A*. The bulk of the radio emission is coming from a mere 300 milllionth of a degree, and the source has a symmetrical morphology. “This may indicate that the radio emission is produced in a disk of infalling gas rather than by a radio jet,” explains Sara Issaoun, graduate student at the Radboud University Nijmegen in the Netherlands, who leads the work and has tested several computer models against the data. “However, that would make Sgr A* an exception compared to other radio emitting black holes. The alternative could be that the radio jet is pointing almost at us”.

The German astronomer Heino Falcke, Professor of Radio Astronomy at Radboud University and PhD supervisor of Issaoun, calls this statement very unusual, but he also no longer rules it out. Last year, Falcke would have considered this a contrived model, but recently the GRAVITY team came to a similar conclusion using ESO’s Very Large Telescope Interferometer of optical telescopes and an independent technique. “Maybe this is true after all”, concludes Falcke, “and we are looking at this beast from a very special vantage point.”

If this is true, it might explain why Sgr A* is generally observed to be one of the quietest central supermassive black holes known. Compared to many others, its flux of emissions is far less.

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Democratic House threatens Webb cancellation

8:35 pm

The House, now controlled by the Democratic Party, has threatened cancellation of the James Webb Space Telescope should that project, already overbudget by $8 billion and 9 years behind schedule, fail to meet its present budget limits.

[The House budget] bill includes the full $304.6 million requested for JWST in 2019, but the report accompanying the bill offered harsh language, and a warning, regarding the space telescope given the cost overruns and schedule delays announced last year.

“There is profound disappointment with both NASA and its contractors regarding mismanagement, complete lack of careful oversight, and overall poor basic workmanship on JWST,” the report states. “NASA and its commercial partners seem to believe that congressional funding for this project and other development efforts is an entitlement, unaffected by failures to stay on schedule or within budget.”

The bill does increase the cost cap for JWST by about $800 million, to a little more than $8.8 billion, to address the latest overruns. “NASA should strictly adhere to this cap or, under this agreement, JWST will have to find cost savings or cancel the mission,” the report states.

I really don’t take this Congressional threat seriously. Our Congress is universally known in Washington as an easy mark for big money. The technique is called a buy-in, where you initially lowball the budget of your project, get it started, and then when it goes overbudget, Congress routinely shovels out the money to continue. Webb is a classic and maybe the worst example of this, but this game has been going on since the 1960s, with no sense that the Congresses of the last half century have had any problem with it.

And I especially don’t take it seriously from the Democrats who, even more than the Republicans, like to shovel money out.

The bankrupt unwillingness of both parties to care for the interest of the country for the past few decades in this matter explains why we have federal debt exceeding $20 trillion.

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