Tag: astronomy

New analysis throws wrench in formation theory of spirals in galaxies

8:29 am

The uncertainty of science: A new analysis of over 6000 galaxies suggests that a long-held model for the formation of spirals in galaxies is wrong.

[Edwin] Hubble’s model soon became the authoritative method of classifying spiral galaxies, and is still used widely in astronomy textbooks to this day. His key observation was that galaxies with larger bulges tended to have more tightly wound spiral arms, lending vital support to the ‘density wave’ model of spiral arm formation.

Now though, in contradiction to Hubble’s model, the new work finds no significant correlation between the sizes of the galaxy bulges and how tightly wound the spirals are. This suggests that most spirals are not static density waves after all.

Essentially, we still have no idea why spirals form in galaxies.

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Astronomers call for regulations to stop commercial satellite constellations

8:12 am

The astronomical community is now calling for new regulations to restrict the number of satellites that can be launched as part of the coming wave of new commercial constellations due to a fear these satellites will interfere with their observations.

Not surprising to me, it is the International Astronomical Union (IAU) that is taking the lead here.

The IAU statement urges satellite designers and policymakers to take a closer look at the potential impacts of satellite constellations on astronomy and how to mitigate them.

“We also urge appropriate agencies to devise a regulatory framework to mitigate or eliminate the detrimental impacts on scientific exploration as soon as practical,” the statement says. “We strongly recommend that all stakeholders in this new and largely unregulated frontier of space utilisation work collaboratively to their mutual advantage.”

When it comes to naming objects in space, the IAU likes to tell everyone else what to do. That top-down approach is now reflected in its demand that these commercial enterprises, with the potential to increase the wealth and knowledge of every human on Earth, be shut down.

The astronomy community has a solution, one that it has been avoiding since they launched Hubble in 1990, and that is to build more space-telescopes. Such telescopes would not only leap-frog the commercial constellations, it would routinely get them better results, far better than anything they get on Earth.

But no, they’d rather squelch the efforts of everyone else so they can maintain the status quo. They should be ashamed.

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VLT snaps image of double asteroid zipping past Earth

9:04 am

Double asteroid imaged by VLT

The Very Large Telescope (VLT) in Chile was successfully able to photograph the double asteroid that flew past the Earth on May 25 at a distance of 3.2 million miles and a speed of 43 thousand miles per hour.

The left image on the right is the raw image, while the right image is their reconstruction after applying adaptive-optics (AO) to the raw image. From the press release:

Bin Yang, VLT astronomer, declared “When we saw the satellite in the AO-corrected images, we were extremely thrilled. At that moment, we felt that all the pain, all the efforts were worth it.” Mathias Jones, another VLT astronomer involved in these observations, elaborated on the difficulties. “During the observations the atmospheric conditions were a bit unstable. In addition, the asteroid was relatively faint and moving very fast in the sky, making these observations particularly challenging, and causing the AO system to crash several times. It was great to see our hard work pay off despite the difficulties!”

To put it mildly, that right image is a fantasy. Astronomers love to tout the wonders of adaptive optics, but no matter how good it might be, it still is garbage-in-garbage-out, a computer simulation based on their guess at what the object would look like if there was no atmosphere in the way. In this particular case, they are being especially fantastic, and guaranteed to be wrong. It is impossible for them to extrapolate such minute surface details from the fuzzy image on the left.

Still, getting an image of this asteroid as it zipped by at that speed using such a large telescope is an achievement, and bodes well for the use of ground-based astronomy of near Earth asteroids.

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First movie of solar eclipse rediscovered

9:56 am

The first movie ever made of a solar eclipse, taken in 1900, has been rediscovered and restored.

The film was taken by British magician turned pioneering filmmaker Nevil Maskelyne on an expedition by the British Astronomical Association to North Carolina on 28 May, 1900. This was Maskelyne’s second attempt to capture a solar eclipse. In 1898 he travelled to India to photograph an eclipse where succeeded but the film can was stolen on his return journey home. It was not an easy feat to film. Maskelyne had to make a special telescopic adapter for his camera to capture the event. This is the only film by Maskelyne that we know to have survived.

I have embedded the movie below the fold.
» Read more

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Three exocomets found circling Beta Pictoris

7:31 am

The uncertainty of science: By analyzing data from the new space telescope TESS, astronomers think they have identified three exocomets orbiting the nearby star Beta Pictoris.

Why do I label this uncertain? Let the scientists themselves illustrate my doubt:

Sebastian Zieba, Master’s student in the team of Konstanze Zwintz at the Institute of Astro- and Particle Physics at the University of Innsbruck, discovered the signal of the exocomets when he investigated the TESS light curve of Beta Pictoris in March this year. “The data showed a significant decrease in the intensity of the light of the observed star. These variations due to darkening by an object in the star’s orbit can clearly be related to a comet,” Sebastian Zieba and Konstanze Zwintz explain the sensational discovery.

The press release provides no other information about why they think this darkening is because of comets rather than exoplanets or some other phenomenon. Based on this alone, I find this report very doubtful and highly speculative.

In related news, astronomers now claim they have detected eighteen more Earth-sized exoplanets in the data produced by Kepler, and they have done so by applying new algorithms to the data.

Large planets tend to produce deep and clear brightness variations of their host stars so that the subtle center-to-limb brightness variation on the star hardly plays a role in their discovery. Small planets, however, present scientists with immense challenges. Their effect on the stellar brightness is so small that it is extremely hard to distinguish from the natural brightness fluctuations of the star and from the noise that necessarily comes with any kind of observation. René Heller’s team has now been able to show that the sensitivity of the transit method can be significantly improved, if a more realistic light curve is assumed in the search algorithm. “Our new algorithm helps to draw a more realistic picture of the exoplanet population in space,” summarizes Michael Hippke of Sonneberg Observatory. “This method constitutes a significant step forward, especially in the search for Earth-like planets.”

This makes sense, but it must be understood that these are only candidate exoplanets, unconfirmed as yet. I would not be surprised if a majority are found to be false positives.

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More gravitational waves detected

9:47 am

Using the LIGO and Virgo gravitational wave telescopes astronomers have detected two more gravitational waves.

On April 25, 2019, one of the twin LIGO instruments and the Virgo detector observed a candidate signal which – if confirmed – would be the first binary neutron star merger during the third observation run, which began on April 1. A second candidate signal was seen on April 26, which – if confirmed – could be a never-observed-before collision of a neutron star with a black hole. The latter candidate was observed by both LIGO instruments and the Virgo detector. Dozens of telescopes on the Earth and in space are searching for electromagnetic or astro-particle counterparts. No identification with an electromagnetic transient signal nor a host galaxy has been made to date for either candidate.

The resolution of LIGO and VIRGO are somewhat limited, so other telescopes have to scan a very large part of the sky to spot a counterpart. It is therefore likely that it will be years before the first counterpart event is identified. When it is however it will tell us how far away the event was and confirm what kind of event it was. Right now, they are only making educated guesses.

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Lunar eclipse meteorite hit the Moon at almost 38,000 mph

10:33 am

By analyzing the data obtained of the meteorite impact that hit the Moon during the January 21 lunar eclipse, astronomers now estimate it crashed into the surface at almost 38,000 miles per hour and would have produced a crater about 50 feet across.

They also estimate that the meteorite itself had a mass of about 100 pounds with a diameter of between one to two feet.

The new crater itself has not yet been spotted, and probably can only be photographed with the high resolution camera on Lunar Reconnaissance Orbiter (LRO). I expect the LRO science team has already scheduled observations for this location. It will be interesting to see if the actual crater corresponds to the estimates of these astronomers.

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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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