Something’s cooking

As it sometimes happen in astronomy, very peculiar signals that could potentially represent a groundbreaking discovery turns out to come not from the far reaches of space, but from a much more local source, like the case of the potassium flaring stars. These incidents illustrate the rigorous testing and investigations that occurs when unexpected signals are present in the data, before a solid discovery can be claimed.

Another example of such a story involves the Parkes Observatory Radio Telescope and the search for fast radio bursts. Fast radio bursts are high-energy astrophysical signals lasting only a few milliseconds, and they are believed to originate from outside of the Milky Way. They were first observed in 2001 and to date only around 20 of these bursts have been detected. Their origin is still a mystery, but astronomers have proposed merging black holes, merging neuron stars, flaring magnetars or collapsing pulsars as the source of these bursts, but these explanations are all somewhat speculative. It is naturally of great interest to discover more of these bursts, to hopefully learn more about their origin.

When observing at radio frequencies, especially when looking for something as rare as fast radio bursts, it is important to rule out any kind of radio interference originating from Earth that could potentially mimic the astrophysical signal. A certain type of interference observed at Parkes has been labelled “perytons” after the mythological Peryton creature. They are short-lived burst of radiation at around 1.4GHz, with a shape that is somewhat similar to a bona fide fast radio burst signal.

While it was pretty clear to the astronomers that the perytons arose from some source on Earth (they were observed over a large field of view), it was not evident what was causing them. The radio astronomers at Parkes Observatory began a meticulous investigation to pin this down. One hint to the source was that they only appeared when the telescope was pointed in certain directions (towards the Visitors Center and the staff building). Furthermore, they mostly appeared between 9am and 6pm, clustering just around lunchtime.

The hunt then began for equipment localized in those two buildings that might emit signals in the right frequency range. Immediately, microwave ovens were suspected as the source, as the magnetron inside these operates at 2.4GHz. This is not too far from the 1.4GHz perytons detected with the radio dish. Several tests were performed, to see if there were malfunctioning microwave ovens that would emit at the right frequency. This initial effort did not produce any perytons, but by further experimentation it was found that if the door of the microwave was opened prematurely, a short 1.4GHz radio burst would escape from the oven. So something had definitely been cooking in the data. Take-away lesson: Save those microwave popcorn for when you’re not observing.

While this may seem like a silly investigation, it nevertheless underlines an important scientific principle, namely that when seeing a strange new signal, it is important to rule out sources of terrestrial origin, before a discovery can be claimed. This particular case also has the advantage that perytons have now been properly characterized and this can be used when trying to identify proper astrophysical signals. While peryton signals looks similar to fast radio bursts, they are not identical. Thus investigations like these helps astronomers in their search for more of these mysterious signals.

For the interested readers, a full paper describing the investigation of the perytons can be found here.

Shooting for the stars

Just like any other field of science, astronomy has had its share of colorful characters over the years. One of the more recent ones was no doubt Fritz Zwicky (1898-1947). Zwicky was a Swiss astronomer, who came to California Institute of Technology as a graduate student, and ended up as a full professor, spending the rest of his life in Pasadena.

Zwicky was known for his antics and sometimes odd behaviour, both during social gatherings, but also during scientific work. In terms of the latter, one could probably consider him thinking very far outside the box. One of the more famous episodes happened during a night of observing with the 200″ Hale telescope at Mt. Palomar Observatory;

One of the challenges when observing objects close to the Earth, is the ability for the telescopes to track fast-moving objects. You want your telescope to be able to move fast across the sky. At the same time, it needs to move smoothly enough so that the object you are tracking stays on the same spot on your detector. This is far from trivial, and even with modern telescopes, accurate tracking of near Earth objects can be quite challenging.

In the days of Fritz Zwicky this was even more true than today. And understandably it was of interest to determine just how fast and accurate it was possible to track objects with the Hale Telescope. Zwicky took an somewhat unconventional approach to testing this.

The 200-inch Hale Telescope at Palomar Observatory

The 200″ Hale Telescope. Photo credit: Palomar/Caltech.

Together with his night assistant, Ben Traxler, he conducted an experiment, where several shots were fired with a rifle out through the dome slit. Zwicky would then attempt to track the bullets with the Hale Telescope. There are no reports as to how successful this experiment was, but  it is definitely an example of Zwicky’s outside-the-box thinking. The incident did however, result in Zwicky being temporarily banned from using the Hale telescope.

On the other hand, his way of thinking did lead to groundbreaking research in supernovae amongst other things. He also proposed several ideas that were subsequently confirmed, like neutron stars, gravitational lensing and dark matter, many of which were not taken seriously at the time.

To my knowledge, Zwicky has been the only astronomer who was literally “shooting for the stars”. Which should probably be considered a good thing.

Thanks to Barbarina Zwicky for providing details for this story.

The casket with an IMPACT

Most astronomical instruments do not come in anything that resembles standard shapes and sizes of normal cargo. It’s not like you go down to the local post office and ask for “one of those boxes for shipping satellites you have out back”. Getting the instruments from A to B usually requires a little more effort, as it is sensitive equipment, often in odd shapes. But sometimes you are in the lucky situation where a more ordinary container can be used with success.

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Artists’ illustration of one of the STEREO satellites. Photo credit: NASA STEREO

In October 2006, NASA launched the STEREO mission, which consists of two, nearly identical satellites, with the purpose of making stereoscopic observations of the Sun to study, for instance, coronal mass ejections and other Solar phenomena. But first the satellite and the instruments on board had to be assembled, which involved shipping some instrument parts in… non-standard containers.

The IMPACT instrument, which is used to study the energetic particles from the Sun, is mounted on a large extendable boom that would be deployed after the satellite had launched. But first the boom and the instrument had to get to the facility where the satellite would be assembled.

On one of many travels from a STEREO meeting, the IMPACT project manager, Dave Curtis, and IMPACT engineer Jeremy McCauley were discussing the status of the instrument. They had come up with a stable and functional design for the boom, but schedule was getting tight. The boom had to be sent to Los Angeles for testing, only a few weeks in the future.

Jeremy had been running the preliminary design numbers and figured that they needed a roughly man-sized box to transport the boom. To this, Dave quipped, “Wouldn’t it be great if we could just use a coffin?” They had a good laugh about that, and went back to work.

STEREOTransportCaseEricBellm

The STEREO boom transport case. Thanks to Eric Bellm for providing the photo.

A few days later, Jeremy returned to Dave’s office, asking if he had been serious about using a coffin. He had researched both options, and learned some interesting facts about caskets along the way.

Caskets can be made from metal, which was a requirement for STEREO, and one could be bought for $6000 and delivered within two days. For comparison, a custom built metal case would’ve cost more than $12,000 and taken 6 weeks to get delivered. Being on a tight schedule, the choice was obvious. A casket was ordered, and the boom shipped to LA in this rather unconventional container.

One additional thing had made using a casket especially attractive – it turned out that every wide-body airplane has a special space for a casket to be transported in the nose of the plane.  So, not only was it cheaper and faster, but shipping was significantly easier since it was a container in a standard form that people were used to dealing with.

This shipment no doubt raised more than a few eyebrows, and one can only imagine what went through the heads of the people dealing with it. Was some old, worn-out instrument getting retired and transported to its final resting place? Do NASA really send dead aliens in caskets? Or had some high-ranking official within the organization passed away? Sadly it was not nearly that interesting, it was merely some astronomers being dead serious about getting their instruments delivered on time.

It’s also a good example that not everything in astronomy needs to be custom-made. Sometimes less will do just fine, even if less means something unconventional.

Thanks to Jeremy McCauley for providing this anecdote.

Rest in peace

Astronomers are normally very dedicated to their work, and many an astronomer spend an entire lifetime unravelling the mysteries of the Universe. When they pass away, some desire to be buried at the places where they lived their lives, rather than in an anonymous cemetery somewhere.

When the new Allegheny Observatory was built, a storage vault was constructed in the pier of the middle sized telescope. This area is one floor below the main basement and it was quickly decided that it was much too damp to store anything of value.

James Keeler, who was the second director of the Allegheny Observatory had left to be the director of the Lick Observatory right before construction began on the new Allegheny Observatory. Unfortunately Keeler died in 1900 at the young age of 43.  Keeler’s widow wanted to have her husbands remains interred at the Lick Observatory but James Lick was already buried there.  The University of California Board of Regents decided that “The great telescope should stand sentinel over James Lick’s body alone.”

John Brashear, who was busily constructing Allegheny Observatory, then decided to make the storage area under the pier into an ornate crypt.  James Keeler was the first person interred at the Observatory crypt in 1906, but not the only one. He was followed by John Brashear himself and his wife Phoebe, who are together in the same burial urn.  James Keeler‘s son Henry died at the very young age of 25, he was buried in the same notch as his father in 1918. James Keeler‘s widow lived until 1944, she died in Arkansas Kansas and was buried all by herself.  Her great, great grandson found her remains and brought her to the Observatory to be reunited with her husband and son on April 15th, 2007.

Allegheny Observatory is not the only observatory to double as a burial ground for astronomers. In Australia, the astronomer Walter G. Duffield was instrumental in the decision to build a solar observatory on the top of Mount Stromlo, called the Commonwealth Solar Observatory, on the site that today hosts the Mount Stromlo Observatory.

Duffield was appointed first director of the Commonwealth Solar Observatory in January 1924, but as a chronic asthmatic, he died of pneumonia on 1 August 1929 at Mount Stromlo while work was still in the preliminary stages. After his death he was put to rest on the western slopes of Mount Stromlo, from which he is overlooking the observatory. His grave is only a short walk from today’s observatory site.

Also Percival Lowell, the founder of the Lowell Observatory, is buried on Mars Hill, near the observatory he helped construct.

No doubt there are more astronomers sleeping the long sleep at other observatories around the world. Here, they can forever watch over the buildings they helped construct, and follow how we keep pushing the boundaries of our knowledge, building on their pioneering work.

“Mind your words, young man”

Astronomical observations are naturally very sensitive to light pollution, which is why you typically place observatories in desolate locations. Even there, you are not guaranteed success, as someone may turn on the light in the dome, shine a flashlight towards the telescope etc. meaning that your observations will be ruined.

Young George Coyne was observing at the Vatican Observatory in Castle Gandolfo, when someone opened the door to the observatory and let in a lot of light, ruining the exposure. George shouted “close that bloody door”, after which the visitor promptly vanished, closing the door behind him. George then continued his observations for the remainder of the night, without further interruptions.

The following day, Pope Paul VI reminded him “my son, you should be in better control of your temper.”

Guess you never know who might be popping by the observatory at night…

The potassium flare stars

In astronomy, we sometimes make discoveries that really make us scratch our heads. Observations that appear to contradict what we believe we know about the Universe. These kind of discoveries are always exciting, as it gives us an opportunity to learn new things about the Universe, and gain a deeper understanding of the world around us. It is certainly something that most astronomers hope for, at some point in their career. That whatever you are researching into, does something unexpected. I mean, who wouldn’t want to have your name associated with a new astrophysical phenomenon?

Thus, one can imagine the excitement, when, in 1962, the French astronomers Daniel Barbier and Nina Morguleff looked at a spectrum they had taken of the G5 dwarf star HD117034 (yes, we’re good with names), and observed two bright emission lines of neutral potassium. A spectra taken the following night, showed no sign of these emission lines. They quickly wrote a summary of their observations and announced the discovery of this new class of “potassium flare stars” in the Astrophysical Journal.

It is not an unknown phenomenon that low-mass stars exhibit flares. These intense, short, outbursts of energy we know even from our own Sun, the solar flares, which are typically followed by coronal mass ejections. However, flaring stars often show emission lines from multiple elements, like silicon, iron and oxygen. Thus, it was a surprise to discover this new class of stars, that seemed to show emission only in the same two potassium lines. Over the next couple of years, another two potassium flaring stars were discovered, both observed from Observatorie de Haute-Provence, as was the case for the initial discovery. Again, the potassium emission lines were only visible in a single spectrum. Adding to the mystery was the fact that the three flaring stars were of wildly different spectral types, namely a G5 dwarf, a K7 dwarf and a B9 dwarf, where particularly the latter stands out, as B-type stars pumps out a lot of energy, meaning that potassium should be fully ionized and no emission lines from neutral potassium would be expected.

Nevertheless, since this had now been observed in different stars at different times, it would appear that a real, transient, astrophysical phenomenon had been discovered, although no one was able to explain it. This spawned a lot of interest, and an extensive search was carried out by Robert F. Wing, Manuel Peimbert and Hyron Spinrad at Lick Observatory, to discover more of these mysterious objects. Although they surveyed 162 stars, not a single potassium flare was observed. Thus, the head-scratching began. Had the astronomers who discovered the three flare stars just been incredibly lucky and made a serendipitous discovery? Or might the explanation be something a bit more down to Earth?

It had previously been suggested that the emission lines could be originating in the Earth’s atmosphere, but in this case the emission lines should have been very narrow, which was not what was observed. The astronomers at Lick Observatory then began looking for other sources of potassium emission. After some experimentation, it was found that the observed emission spectra matched quite closely the spectra of ordinary matches, if the light from the matches were able to reach the spectrograph. Several different types of matches were used, and all produced similar results. The same thing was also tested at the Observatorie de Haute-Provence, and it was found that, in certain positions, the light from the matches did indeed reach the spectrograph. The full paper can be read here.

Thus it would appear that the potassium flaring stars was in reality a potassium flaring member of the observatory staff, who had lit up briefly in the science literature. Following this, I bet this observatory may have been the first to see a smoking ban on the premises. Or at least anywhere near the spectrograph.

This is also a perfect example of how astronomy, and science in general, works when something weird and unexpected it found (remember the super luminal neutrinos?). Such findings need to be independently confirmed and checked rigorously, to rule out other potential explanations. In many cases these things can be explained by already known phenomenon, or an overlooked mistake somewhere, but sometimes genuinely new things are discovered, which is amazing!

As a side-note, the extensive testing of the spectra of matches also showed that French and American matches were very similar products, in terms of composition, so there’s no blaming foreign matches when you can’t light your fire.

Under pressure

At the Australian Astronomical Observatory, there had been a problem with irregular air pressure in the mechanics for the robot positioning the optical fibers for the AAOmega multi-object spectrograph, mounted on the 3.9m Anglo-Australian Telescope. This is of course not ideal, since it is crucial that the optical fibers are positioned accurately and correctly. If not, they will fail to catch the light from the stars they are meant to observe, and no light will reach the spectrograph. What was needed, was something that could even out those irregularities, and maintain the pressure at a steady level, so one did not suddenly have a fault at a critical time during observing.

Naturally, this calls for specialized equipment, which here means something like “reach for the nearest container that can withstand some pressure and attach to instrument.” Luckily, a very specific kind of container is usually found in ample supply around telescopes. These containers can withstand a pressure of around 100 PSI, or approximately 7 bar, before they burst, so unless you are dealing with really high pressure, they are fairly sturdy.

The high tech pressure vessel attached to the 2dF fiber positioner robot at the AAT. Photo credit: Anna Sippel

The high tech pressure vessel attached to the 2dF fiber positioning robot at the AAT. Photo credit: Anna Sippel

They look something like what you see in this photo, it should be familiar to most people. This “pressure vessel” did perform its job well, and managed to even out the irregularities in the pressure, so the instrument could continue to perform observations as planned. It was kept as a working solution for a couple of weeks, until a more suitable solution was found and installed.

The replacement happened to be installed just before the Minister of Science was due to visit the telescope. Not that these things were necessarily connected, but one could envision a few raised eyebrows, had the bottle still been on when the officials were given the grand tour of the telescope.

Good thing that astronomers need lots and lots of sugary, caffeinated drinks to keep them going through the long hours of observing. So keep drinking that coke. It may not be healthy, but you never know when you’ll be in urgent need of a pressure container to keep your instrument running!