Article about VASCO in Forskning & Framsteg, Vol 6 2018

innehal

In the early spring, we were interviewed

about VASCO for the Swedish popular science journal, “Forskning & Framsteg” for its June issue. You can currently buy it in Pressbyrån in Sweden or online (at http://fof.prenservice.se/KodLandning/Index/?Internetkod=057-0571311&gclid=EAIaIQobChMI1PGSw46G3AIVkYKyCh35nAC4EAAYASAAEgI6J_D_BwE).

You can also read an online version: (link: https://fof.se/tidning/2018/6/artikel/jakten-efter-forsvunna-stjarnor)

— Beatriz Villarroel

Article about VASCO in Forskning & Framsteg, Vol 6 2018

What Drake’s equation says about the nature of probability

Drake’s equation (i.e. a decomposition of the probability that alien life must exist as a chain of conditional probabilities which sound more reasonable. After a beer or two. Or three) makes an interesting case for thinking about the nature of probabilities. What do we mean really when saying ‘those aliens must in all likelihood exist‘? No way it can point to a relative frequency. Maybe a propensity interpretation? But statements as ‘they tend to exist‘ make not much sense either. The only viable option – as far as I can see – is that evidence suggested by Drake should be in the eye of the beholder. Subjective. Belief-based. Bayes. In the good ol’ De Finetti sense. Earthlings and any alien civilisation far far away must be exchangeable. We are as curious for them as they for us. This seems a solid foundation for educated guessing about this.

-Kristiaan

What Drake’s equation says about the nature of probability

New questions and old observations: How the front line of astronomy benefits from its history

Considering the history of astronomy, we see that several phenomena known today were within observational reach much earlier than when they were actually discovered. Heinrich Schwabe discovered the solar cycle in the 1840s, after almost two decades of diligent telescopic observations. Numerous records of sunspots visible to the naked eye are preserved from ancient cultures, though, and it is known (see e.g. Schaefer 1991) that the number of sunspots visible to the naked eye follows the same 11 yr cycle as the relative sunspot number (found via observations with telescopes). Using suitable eye protection or taking advantage of when e.g. thick clouds dampen the sunlight sufficiently, an observer in ancient times with enough stamina could (as others have pointed out) have discovered the solar cycle.

However, just because a phenomenon is within technological reach to observe does not mean that there is sufficient awareness or interest to even ask the questions leading up to its discovery. The Sun had already been under scrutiny with telescopes for over 200 years when Schwabe made his discovery, and there is slight reason to believe that ancient solar observers would have been able to pose questions leading to a prolonged observing campaign revealing the solar activity cycle. Today, the scant ancient observations of naked eye sunspots are being collected (see e.g. Wittmann & Xu 1987) for use in modern solar studies.

What else could be hiding in ancient astronomical records? Studies of transient celestial phenomena such as comets, meteor showers and supernova explosions have used pre-telescopic observations to gain valuable insights. As astronomy develops, new questions are raised, and even gamma-ray bursts (GRBs) have been addressed from the perspective of historical records. These short (seconds to hours), extremely luminous bursts of gamma rays happen anywhere in the sky and are found at a rate of  about one per day. GRBs usually occur at distances of billions of light years and likely arise from either certain types of supernovae or from merging neutron stars. Their optical afterglow is usually invisible to the naked eye, with at least one clear exception. The GRB 080319B, observed on 2008 March 19, reached peak visual magnitude 5.3 and was within naked eye visibility for about 30 sec (Racusin et al. 2008).

This GRB inspired Strom, Zhao & Zhang (2012) to see if any historical record of other naked-eye GRBs could be found, also asking what any such historical record could tell us. Using statistics of optical counterparts of GRBs from 1997-2010, they demonstrate that at least 10 GRBs of about the same magnitude as GRB 080319B happen per century, and that 2 GRBs per century should reach magnitude 3 (a brightness comparable to the faintest star in the Big Dipper). A handful of times per millennium, they estimate, a magnitude 0 GRB (bright as Vega) could appear in the sky. While unlikely, a naked-eye observer with good knowledge of the night sky could notice a visual GRB during the seconds or minutes it is visible. Vetting old Chinese records, Strom, Zhao & Zhang found a handful of candidate events, an interesting one coming from 1855 August 16 (of a “star of red color” visible “in the southeast” for “about 7 minutes”). The vagueness of the record prevents further follow-up, though. Discussing the use of a possible recovery of a naked-eye GRB from historical records, Strom, Zhao & Zhang argues that a study of the GRB remnant after several centuries could maybe benefit. Even without a GRB remnant identification, they point at how identification of a historical naked-eye GRB could help constrain the rates of such rare events.

With the above examples from investigations inspired by observations made with the naked eye throughout history, it is staggering to think about what can be learned from renewed investigations of such a rich material as the photographic plates taken at observatories around the globe during the past century and a half. While our knowledge will never be complete, we nevertheless have the ability today to address astrophysical questions undreamt-of when the plates were taken decades ago. Extreme phenomena and beautiful patterns of nature likely hide within plain sight in photographic plates and other records from the recent past of astronomy. The VASCO (Vanishing & Appearing Sources during a Century of Observations) project intends to explore this.

Anders Nyholm

New questions and old observations: How the front line of astronomy benefits from its history

Life vs Dark Energy

An amazing paper by Dan Hooper appeared on the arXiv preprint server in the past week: “Life Versus Dark Energy: How An Advanced Civilization Could Resist the Accelerating Expansion of the Universe”. The idea is that extremely advanced alien civilizations seeking to maximize the energy available to them billions to trillions of years into the future might want to start gathering distant stars and bringing them closer to home. By moving the stars at relativistic velocities, one could prevent them from being carried outside the horizon by the accelerating cosmic expansion due to dark energy. However, since stars of all masses are not equally suitable for this relocation trick, the end product may be large groups or clusters of galaxies with pretty unusual spectral properties.
Link to paper: https://arxiv.org/abs/1806.05203

– Erik Zackrisson

Life vs Dark Energy

Some thoughts after the VASCO-i event

The first VASCO workshop that was held in Uppsala 1 – 3rd of February 2018. It took place in a small room at the ITC – in the former military quarters which now is part of the physical science and engineering campus of Uppsala University. The workshop was a joint astronomy and IT workshop, where transient astronomy, SETI and machine learning were in focus. The VASCO project itself is a cross-disciplinary IT/astronomy project, where the latest progresses in machine learning are used to create the tools necessary to carry out the conceptually easy-but-technically advanced project of ours. During the workshop, we heard contrasting talks which yet complemented each other as they targeted different perspectives needed to carry out our project. To mention just a few (while I’d love to mention all of them!), Pete Worden, chairman of the Breakthrough Prize Foundation and executive director of Breakthrough Starshot, gave an inspiring and optimistic talk about their activities. Lawrence Murray showed a powerful code developed for probabilistic programming, that can be particularly useful in ranking the “vanishing candidates” we find by interestingness. Machine learning and its role in studying football players and the movement of fish, were demonstrated by David Sumpter. On the last day, we discussed the prospects for making the VASCO-machinery we have built and designed to actually run and work with the acquired samples.

Perhaps, this is what makes VASCO a “recyclable” SETI-project; while the ultimate goals may be typical of any high-risk, ultra-high gain project in science where the gains are uncertain and with fairly unpredictable implications, the challenges we face on our way there will certainly provoke new development in IT methods. Likewise, other extremely variable sources that we expect to find along the way will make the effort more than meaningful, even if we wouldn’t discover a single physically vanishing star. By making sure that side results happen, the risky nature of the ultimate goal is transformed into a valuable road for both IT experts and astronomers. Meanwhile, we can run VASCO and carefully study whatever object the exotic Universe will serve us.

– Beatriz Villarroel

Some thoughts after the VASCO-i event