Category Archives: Astronomy

Halley's Comet May 29, 1910

110 Years Ago: Earth’s Passage Through Comet Halley’s Tail Mesmerizes The Public

On May 19 / May 20, 1910, Earth passed through the tail of Halley’s Comet with great fanfare.

The event is meaningful to me for two reasons. First, my grandmother told me about it when I was little. She herself was a little girl in 1910, and her memories were not very detailed. But she recalled, as her strongest memory, the general feeling of excitement among the adults around her. Some must have been genuinely panicked, others were probably nervous, and yet others were mocking those who suffered from vivid superstitions.

From German: “Old woman, close the umbrella. When the comet sees you, it’ll tun around and Earth is saved.”

Today, few people know that there was actually another comet visible in the sky earlier that year of 1910. The “Great January Comet of 1910”, officially designated “C/1910 A1” was a surprise visitor in the sky. Already visible to the naked eye when it was first reported on January 12, it brightened very suddenly, to the point where it eventually became brighter than Venus, and was visible during the day.

First spotted in the southern hemisphere, it reached perihelion on January 17 with a magnitude of –5. It then declined in brightness but became a spectacular sight from the northern hemisphere in the evening twilight. By early February, its curved tail reached 50 degrees into the sky.

There were of course plenty of newspaper accounts. The public, not yet accustomed to front page astronomical news, became highly interested in comets, and in what the experts had to say — especially at a time when superstitions and the belief in metaphysics was much more widespread than today.

At the time, Halley’s Comet, which had been known since ancient times, had been calculated to reach its perihelion on April 20, based on Newtonian physics and the work of Edmond Halley.

Illustration from the January 1910 issue of Popular Science Monthly magazine, showing how Halley’s tail points away from the Sun as it passes through the inner Solar System

Astrophotography and astrospectography were new fields, they were used to detect toxic gas cyanogen gas in the comet’s tail. The highly famous French astronomer and author Nicolas Camille Flammarion speculated that, when Earth passed through the tail, the poison gas “would impregnate the atmosphere and possibly snuff out all life on the planet.”

Flammarion was not only a genius scientist and author, but also a man with rather esoteric beliefs. He believed not only in the transmigration of souls, but also in telepathy, apparitions, hauntings, and “psychic forces”.

Very quickly, all manner of profiteers, charlatans, mystics, and those purporting to possess special astrological insights, seized on the opportunity, and soon, the panicked public was buying up quack “anti-comet pills”, “anti-comet umbrellas” and gas masks. Sadly, we even find newspaper accounts of people committing suicide because they didn’t want to see the catastrophe.

Considering the nature of what left the strongest impression in my grandmother’s memories, I wonder what today’s small children will remember, many decades from now, about the current COVID-19 crisis. Surely, it will be memories about how we adults reacted, which should also give us reason for contemplation.

The other reason why Halley’s Comet interests me is its association with one of my favorite authors and personalities. Mark Twain was born November 30, 1835, exactly two weeks after the comet’s previous perihelion. In his autobiography of 1908, he writes:

I came in with Halley’s comet in 1835. It is coming again next year, and I expect to go out with it. It will be the greatest disappointment of my life if I don’t go out with Halley’s comet. The Almighty has said, no doubt: ‘Now here are these two unaccountable freaks; they came in together, they must go out together.’

Twain died on 21 April 1910, the day following the comet’s subsequent perihelion. This is how the comet looked that day:

Portion of Plate b41215 of Halley’s comet taken on April 21, 1910 from Arequipa, Peru with the 8-inch Bache Doublet, Voigtlander. The exposure was 30 minutes centered on 23h41m29s R.A. and +07d21m09s Declination.

– 30 –

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Light Pollution

Light Pollution

Photo: NASA and NOAA. Click to enlarge.

The natural night skies as seen from Earth are awe inspiring. But ever since the invention of electric lighting, unobstructed dark skies have been disappearing from industrialized, populated areas. Sadly, most people living in the white areas of the picture above have never had a chance to experience the firmament’s full glory.

More information about light pollution and the importance of fighting it:

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Mars, Four Billion Years Ago

Four billion years ago, Earth was a rather hellish place. Its crust was still very thin and unstable. There was heavy and violent volcanic activity. Earthquakes were shaking the ground, liquid lava flowed in many places, and poisonous gases were everywhere. On top of that, our poor little planet was bombarded by a constant barrage of large meteorites. Despite all of that, the first primitive life forms are thought to have appeared during this period.

By contrast, at the same time, Mars was a very tranquil place. Here is a NASA animation, based on the latest data we have, showing what the surface of Mars would likely have looked like at the same time. Blue skies, clouds, oceans, lakes, rivers, mountains and all. Almost like a place for a vacation resort!

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Earth As Seen From Saturn

This picture shows us. All of us on planet Earth. All 7 billion human beings contained one tiny dot of light.

Earth from Saturn

(Click to enlarge)

In this rare image taken on July 19, 2013, the wide-angle camera on NASA’s Cassini spacecraft has captured Saturn’s rings and our planet Earth and its moon in the same frame. It is only one footprint in a mosaic of 33 footprints covering the entire Saturn ring system (including Saturn itself).  At each footprint, images were taken in different spectral filters for a total of 323 images: some were taken for scientific purposes and some to produce a natural color mosaic.  This is the only wide-angle footprint that has the Earth-moon system in it.

The dark side of Saturn, its bright limb, the main rings, the F ring, and the G and E rings are clearly seen; the limb of Saturn and the F ring are overexposed. The “breaks” in the brightness of Saturn’s limb are due to the shadows of the rings on the globe of Saturn, preventing sunlight from shining through the atmosphere in those regions.  The E and G rings have been brightened for better visibility.

Earth, which is 898 million miles (1.44 billion kilometers) away in this image, appears as a blue dot at center right; the moon can be seen as a fainter protrusion off its right side. An arrow indicates their location in the annotated version. (The two are clearly seen as separate objects in the accompanying narrow angle frame: PIA14949.) The other bright dots nearby are stars.

This is only the third time ever that Earth has been imaged from the outer solar system. Continue reading

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Flying Over the Earth at Night

This video is so amazing that I had to repost it as it came. This was originally posted on “Astronomy Picture of the Day“, a daily blog site highly recommended for everyone with an interest in astronomy.

Video Credit: Gateway to Astronaut PhotographyNASA ; Compilation: David Peterson (YouTube);
Music: Freedom Fighters (Two Steps from Hell)

Explanation: Many wonders are visible when flying over the Earth at night. A compilation of such visual spectacles was captured recently from the International Space Station (ISS) and set to rousing music. Passing below are white cloudsorange city lightslightning flashes in thunderstorms, and dark blue seas. On the horizon is the golden haze of Earth’s thin atmosphere, frequently decorated by dancing auroras as the video progresses. The green parts of auroras typically remain below the space station, but the station flies right through the red and purple auroral peaks. Solar panels of the ISS are seen around the frame edges. The ominous wave of approaching brightness at the end of each sequence is just the dawn of the sunlit half of Earth, a dawn that occurs every 90 minutes.


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by Tim Tompson*

Easter Sunday will soon be upon us.

In the year 325 A.D. the First Council of Nicaea defined the date for Easter as the first Sunday following the first Full moon after the Vernal equinox. But astronomically selected dates can move around; e.g., the vernal equinox can happen on 20 March as well as 21 March, and the phases of the moon are not tied either to the civil calendar nor to the equinoxes. So, for the purposes of calculating the date for Easter, the Roman Catholic church defines its own equinox as always happening on 21 March, and they use their own “ecclesiastical full moon”, which by definition always occurs on the 14th day of the ecclesiastical lunar month on the ecclesiastical lunar calendar (which assumes by definition that 19 tropical years equals 235 synodic months exactly [the correct number is 234.997]). In this way, Roman Catholic Easter always falls in the window of 22 March to 25 April.

Roman Catholics use the Gregorian calendar, which was finalized in 1582 for the explicit purpose of returning the date of Easter to the same date it had when the First Council of Nicaea met. In the time between 325 and 1582, the vernal equinox had slipped backwards through the civil calendar to 11 March instead of 21 March, which it was in 325. So when the Gregorian calendar replaced the Julian calendar in 1582, ten days were skipped over, which moved Easter back to 21 March. And by the trick of skipping leap days in years ending in 00, unless they are evenly divisible by 400, the length of the average civil calendar year is shortened from 365.25 days (that is one “tropical year”) to 365.2425 days, the end result of which is that the civil calendar will fall behind the seasons by about one day come the year 3200 (a problem easily solved by skipping the leap day in 3200).

The actual time it takes to go from one vernal equinox to the next is 365.24219878125 days, which should result in an accumulated difference between the seasons and the civil calendar of 3 days, 17 minutes, 33 seconds over 10,000 years. But the mean tropical year is decreasing by 0.53 seconds per 100 years (a slow tidal transfer of energy from sun to Earth), and the mean length of day is decreasing by 0.0015 seconds per 100 years (a slow tidal transfer of energy from Earth to moon). That’s why the calendar can lose a whole day in only about 1200 years. One could cleanup the next few thousand years by skipping the leap day in the year 3200, keep the leap day in 3600 and 4000, and skipping the leap day in 4500 & 5000.

Eastern Christians (mostly the Eastern and Greek Orthodox churches, Eastern Catholic and Coptics) use the old Julian calendar, so they celebrate Easter basically a month later than do the Romans, in the window between 4 April to 8 May.

There are various good reasons for having a civil calendar that is locked to the seasons. But the one that has been most important has proven to be the need to have Easter fall on a fixed time of the civil calendar year.

* The writer is a physicist retired from NASA’s Jet Propulsion Laboratory. Among his main personal interests are astronomy, chess, languages and linguistics, and military history.

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Lowell Observatory: Fundraising To Save Clark Telescope

Percival Lowell observing Venus from the observer's chair of Clark telescope at the Lowell Observatory in 1910.

Percival Lowell observing Venus from the observer’s chair of Clark telescope at the Lowell Observatory in 1910.

Percival Lowell was convinced that there had to be life on Mars, and he spent much of his life trying to prove it. (I often wonder how excited he would be about our Mars rovers).Of course Lowell had no such help. In 1895, the astronomer commissioned a telescope he thought suitable for the visual examination of the surface of Mars. The refracting telescope was made by Alvin Clark & Sons (leading telescope makers of the time) and is housed at Lowell Observatory in Flagstaff. It is among the most important, historical science landmarks.

Today, the 117-year-old “Clark telescope” is in need of major restoration, and the Lowell Observatory is holding a crowdsourcing campaign to raise funds.

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You Are Here

Click to enlarge.

This is the current map of the Milky Way, as best we can make it out from our viewpoint inside. Our home galaxy has about 200 billion to perhaps 500 billion other stars beside our own. Orbiting them are billions to trillions of planets and moons. And that’s just one of billions of galaxies in the universe.

We cannot take pictures of our galaxy, so this image is a model. It is based primarily on results from the Galactic Legacy Infrared Mid-Plane Survey Extraordinaire (GLIMPSE) and the Multiband Imaging Photometer for Spitzer Galactic Plane Survey (MIPSGAL). Both are key projects for the infrared Spitzer Space Telescope. This particular image was released on June 3, 2008 at the 212th meeting of the American Astronomical Society.

I hope your head is spinning. (It should be).

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Transit Of Venus

Like thousands of other people, I watched the Venus transit on my computer, via webcast from the Keck Observatory on the summit of Mauna Kea on Hawaii. (It was amusing to see a bunch of excited scientists trying to keep a TV audience entertained for  6 hours).

There are plenty of great transit photographs taken by amateurs. (The L.A. Times has a nice collection of images from Southern California). But the best view was from space. My favorite image is this one, taken by the Japanese Hinode spacecraft.

(Click to enlarge).

Hinode is a collaboration between the Japanese space agency JAXA and various institutions in the US and the UK. Then known as “Solar-B”, the satellite was launched on a Japanese M-5 rocket in 2006. Earlier this year, Hinode returned  stunning images and data from the Lunar eclipse. Well done, Japan!


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Solar Eclipse

While hiking in the woods yesterday, I spontaneously decided to build an improvised pinhole camera to see the solar eclipse. Materials used: a roll of toilet paper, some aluminum foil I found in a trash can, a notepad from my backpack, and of course, my trusted Swiss army knife. Here is the resulting contraption and the image it produced:

If this does not impress you, here is a more professional image taken by the European Proba-2 microsatellite. (Hey, it cost a bit more). Credit: ESA/Pierre Carril.

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