Jump to content

Searching for Artificial Light Sources in the Solar System Based on the Loeb-Turner Test

Avi Loeb Medium
 Share

Recommended Posts

Avi Loeb Medium Newbie

Avi Loeb Medium

Posted
Posted
1*3HCx4pAItEULUKc4_shtLA.jpeg
An image of the city of Dubai from the International Space Station in 2012. (Image credit: NASA)

In 2010, I attended the official inauguration conference of a new campus of New-York University in Abu Dhabi, along with my Princeton colleague, Ed Turner. As we were touring Abu Dhabi and Dubai, the tour guide bragged that Dubai’s city lights at night time can be seen all the way from the Moon.

Ed and I were instantly inspired to consider the question: How far away can city lights be observed in the Solar System? In particular, we Googled Tokyo which had its official luminosity listed online, and calculated during some of the boring talks at the conference that Tokyo would detectable at the distance of Pluto by deep exposures of the Hubble Space Telescope. In other words, if a city like Tokyo existed on Pluto, then the Hubble Space Telescope could detect its lights!

But detecting a source of light from an unknown object is insufficient. How can we infer that the light originates from an artificial source rather than the reflection of sunlight from a rock or iceberg? In principle, this can be done by taking a spectrum, namely studying the intensity of the light source as a function of wavelength. Artificial light would typically have a different spectrum than sunlight. However, it is challenging to obtain a spectrum of a faint source of light. Is there another way?

A self-luminous source behaves like a light bulb. It fades inversely with distance squared. However, an object illuminated by a lamppost fades inversely with distance to the fourth power. Ed and I reckoned: all we need to do is measure the change in the source brightness as a function of its distance from the Sun in order to infer whether it reflects sunlight or produces its own light. This was the idea conveyed in a paper that we published in 2012 here.

A few years earlier, I published another original idea here with Ed Turner and Amaya Moro-Martin, where we were first to predict quantitatively that interstellar objects could be detected with survey telescopes, like the NSF-DOE Rubin Observatory. This idea is coming to fruition right now, although the first paper to suggest it is forgotten. This appears to be the fate of pioneering ideas ahead of their time. In 1952, the astronomer Otto Struve suggested in a paper published here the practical methods for discovering Jupiter-mass planets in close-proximity to Sun-like stars. His idea was ignored for 43 years until the first discovery was reported here in 1995 by Michel Mayor and Didier Queloz who won the Nobel Prize for it. Their discovery paper does not reference Struve’s paper. Why is science so inefficient?

The application of the Loeb-Turner test to interstellar objects allows us to distinguish between natural interstellar rocks which reflect sunlight and technological objects which produce their own light. But a much larger population of objects is known to reside inside the Solar System. Have we actually checked whether all known objects beyond Neptune, the so-called trans-Neptunian objects, only reflect sunlight?

When Mike Brown from Caltech, who pioneered the discovery of trans-Neptunian objects, visited my Harvard office a decade ago, I asked him: Did you check whether their brightness declines as expected for the reflection of sunlight? Mike replied: “Why should I check? They are obviously just reflecting sunlight.” His response explains why Struve’s idea in 1952 did not translate to the discovery of a hot-Jupiter decades earlier than 1995. Observers assumed that they understood why Jupiter is far from the Sun and so they chose not to waste observing time searching for Jupiter-mass planets in close proximity to their host star. This led me to wonder: How many scientific discoveries end up as “unborn babies” because of prejudice?

And so today, my brilliant new postdoc, Omer Eldadi, completed a detailed paper in collaboration with me, studying all existing data on the brightness variation of trans-Neptunian objects with distance from the Sun. By applying the Loeb-Turner test to all objects, we have found that the current data available in the Minor Planet Center archive is of insufficient quality to conduct the test. Of all trans-Neptunian data bins, 53 consistent with reflected sunlight, 24 with self-luminous emission, and 109 appear anomalous. The anomalous bins exhibit slopes outside the expected range, consistent with uncorrected instrument calibration offsets rather than any particular physical mechanism. However, we find that the NSF-DOE Rubin Observatory’s ten-year survey will deliver uniform single-instrument calibration on a tenfold larger sample and resolve the Loeb-Turner test with a statistical confidence better than 10 standard deviations on hundreds of trans-Neptunian objects.

Here’s hoping that thanks to the NSF-DOE Rubin Observatory, we will be able to know within the coming years whether there are any spacecraft with city-scale lights within the Solar System.

ABOUT THE AUTHOR

1*LE3Xlzc3hNG5VDAGlDP8KQ.jpeg
(Image Credit: Chris Michel, National Academy of Sciences, 2023)

Avi Loeb is the head of the Galileo Project, founding director of Harvard University’s — Black Hole Initiative, director of the Institute for Theory and Computation at the Harvard-Smithsonian Center for Astrophysics, and the former chair of the astronomy department at Harvard University (2011–2020). He is a former member of the President’s Council of Advisors on Science and Technology and a former chair of the Board on Physics and Astronomy of the National Academies. He is the bestselling author of “Extraterrestrial: The First Sign of Intelligent Life Beyond Earth” and a co-author of the textbook “Life in the Cosmos”, both published in 2021. The paperback edition of his new book, titled “Interstellar”, was published in August 2024.

Professional website:

https://lweb.cfa.harvard.edu/~loeb/

Social media:

https://avi-loeb.medium.com/
https://www.youtube.com/@ProfessorAviLoeb

https://open.spotify.com/show/1zhndXkvSY2b8FdjspFpCd
https://x.com/ProfAviLoeb

stat?event=post.clientViewed&referrerSou

View the full article

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

×
 Share
Go to topic listing

  • Similar Topics

    • CosmicSignals
      Researchers Propose Searching The Moon For Microscopic Technosignatures
      By CosmicSignals
      A recent study presents a novel idea for searching for signs of extraterrestrial intelligence: examining lunar regolith for microscopic engineered particles. Led by Dr. Lewis Pinault from the SETI Institute, this research outlines a quantitative framework for investigating whether tiny, durable particles from past technological civilizations could have accumulated on the Moon over billions of years.
      The researchers suggest that instead of focusing solely on radio or laser signals from potential alien civilizations, we might find evidence of their existence in the form of microscopic debris. This approach is intriguing because the Moon, lacking an atmosphere, flowing water, or tectonic activity, has preserved material from across the Solar System for approximately four billion years. This stability makes it a unique archive of the Milky Way’s history.
      Dr. Pinault points out that the Moon has been continuously collecting dust and materials, much of which could predate the Moon itself. The hope is that if advanced civilizations produce durable microscopic debris—either as a direct result of their activities or as unintended byproducts—some of that material could be embedded in the lunar soil.
      The study emphasizes that while it does not claim to have found extraterrestrial technosignatures, it lays out a practical observational framework for future lunar sample-return missions. The authors propose that by carefully analyzing about one cubic meter of lunar regolith with modern microscopy and AI-assisted imaging, we could begin to determine the presence of artificial materials that might hint at past technological life.
      The methodology outlined involves using advanced techniques such as tomography and spectroscopy to sift through lunar soil. Such techniques could help establish limits on the amount of artificial material produced by technological civilizations throughout the history of the Galaxy. This information could then shed light on how many technologically capable civilizations might have existed in our Milky Way.
      One aspect that stands out in this proposal is how it reframes our search for extraterrestrial intelligence. Traditionally, SETI has concentrated on signals sent from other civilizations, but looking for physical remnants could reveal a broader narrative of intelligent life in the cosmos. It raises questions about how we define evidence of alien life and what forms that evidence might take.
      However, the study does have limitations. It does not provide evidence of such particles existing on the Moon, nor does it guarantee that future missions will find them. The success of this approach depends heavily on the next steps taken by lunar exploration missions, which will need to incorporate these new methodologies into their sampling and analysis processes.
      As we delve deeper into this line of inquiry, it poses a fascinating question: if we were to find signs of past civilizations on the Moon, what would that mean for our understanding of life in the universe? Could we be on the verge of discovering that we are not alone, but rather part of a much larger historical tapestry of intelligent life? The implications could be profound not only for astrobiology but for humanity's place within the cosmos.
    • CosmicSignals
      New Framework For Searching The Moon For Microscopic Technosignatures
      By CosmicSignals
      A recent study suggests that the Moon could be a key site for searching for microscopic technosignatures—tiny, engineered particles left behind by technological civilizations. This idea shifts the focus from traditional methods like radio signal detection to examining lunar regolith, which has been collecting material from space for billions of years. Lead researcher Dr. Lewis Pinault from the SETI Institute outlines a framework for detecting these potential remnants of past civilizations.
      One striking detail is that, unlike Earth, the Moon has no atmosphere or flowing water to erode ancient material. This makes the lunar surface a stable archive, allowing for the possibility that microscopic debris from advanced civilizations could have survived the passage of time. The study emphasizes the potential for discovering evidence that might have been overlooked in other searches.
      The researchers propose that if advanced civilizations create durable microscopic debris, this material could become embedded in the Moon's surface. Over a four-billion-year period, the lunar regolith has collected dust and particles from the Solar System and beyond, creating a unique historical record. The study does not claim to have found these technosignatures but sets the groundwork for future lunar missions to search for them.
      Using modern microscopy and AI-assisted imaging techniques, scientists could analyze one cubic meter of lunar regolith to establish limits on the amount of artificial material present. This could provide insights into the number of technologically capable civilizations that may have existed in our galaxy. The framework proposed could pave the way for future missions to test these hypotheses, potentially revolutionizing our understanding of life beyond Earth.
      The notion that the Moon could hold remnants of ancient technologies raises intriguing questions about our own search for extraterrestrial life. If tiny particles from lost civilizations have made their way to the Moon, what other secrets might our celestial neighbor hold? This study urges us to reconsider how we approach the search for life beyond our planet by expanding our focus to include the Moon as a site of potential discovery.
      As the lunar surface continues to be explored, the potential for uncovering these technosignatures invites further investigation. What might we learn about the history of civilizations, both terrestrial and extraterrestrial? The challenge lies in devising methods to distinguish natural lunar materials from those that may be artificial in origin.
      Given the exciting possibilities ahead, how might future lunar sample-return missions adapt their methods to search specifically for these microscopic traces of technology? The answers could significantly impact our understanding of life in the universe.
    • UAPResearcher
      What Insights Can Failed Solar Eruptions Provide About Space Weather?
      By UAPResearcher
      A recent discussion highlighted the mystery behind a failed solar eruption observed in March 2024. Researchers, including Dr. Kathy Reeves, focused on understanding the conditions that prevent some solar eruptions from escaping the Sun's atmosphere. This is particularly intriguing because solar eruptions can have significant effects on space weather and, by extension, our planet's atmosphere and technology.
      When a solar eruption occurs, it can eject large amounts of plasma and magnetic fields into space, commonly known as a coronal mass ejection (CME). However, not all solar flares lead to eruptions. The distinction is crucial: flares can happen without an eruption, and an eruption can occur without a flare. This relationship complicates predictions about space weather events.
      The March 2024 event was noteworthy because researchers had a wealth of data from multiple spacecraft, including NASA's Solar Dynamics Observatory and JAXA’s Hinode. These instruments provided different perspectives on the eruption, offering insights into the conditions that lead to a successful eruption versus a failed one. For instance, Dr. Reeves mentioned that knowing when a flare might not lead to an eruption is valuable for understanding solar activity.
      The coordinated observations from various spacecraft allowed scientists to analyze the solar event in detail, utilizing extreme ultraviolet and X-ray data, as well as magnetic-field measurements. This comprehensive approach helps researchers identify the factors that determine whether material will escape the Sun.
      What makes this line of inquiry particularly relevant is its potential to inform our understanding of space weather's impact on Earth. Solar eruptions can disrupt satellite communications, power grids, and various technologies. Understanding why some eruptions fail could enhance our ability to predict and mitigate these disruptions, thereby protecting our technological infrastructure.
      Given the importance of solar activity in affecting life on Earth and possibly beyond, what can we learn from these failed eruptions? Could this knowledge lead to improved models for predicting space weather events that might have implications for future explorations and our understanding of life in the cosmos? There's a lot to unpack regarding how solar dynamics interact with the broader universe, especially if we consider life beyond our planet. This could fundamentally change how we assess habitability not just on Earth, but on exoplanets that experience similar solar phenomena.
      As we continue to study the Sun and its behavior, the question remains: how might insights from failed solar eruptions shape our understanding of both our solar system and the potential for life elsewhere?
    • SpaceObserver
      Why Do Some Solar Eruptions Fail?
      By SpaceObserver
      Full sun views from different NASA solar cameras of a failed solar eruption from data collected in March 2024. Credit: Tingyu Gou A solar eruption begins to rise from the Sun. Then, instead of continuing outward, it stops. Why? What makes one eruption escape while another never makes it out? That was the question at the center of a recent SETI Live conversation between host Dr. Becca Robinson, heliophysicist, Director of Education, and MUSE Outreach Lead at the SETI Institute, and Dr. Kathy Reeves, a senior astrophysicist at the Center for Astrophysics | Harvard & Smithsonian. Dr. Reeves studies solar eruptions using both observations and simulations. In the conversation, she discussed research based on data collected from a particularly well-observed failed solar eruption, one that gave her team an unusually detailed view of what happens when an eruption begins to rise but does not make
      The source gives us a useful starting point, but the underlying details and evidence are still worth examining closely.
      Which detail in this report do you think deserves the closest follow-up?
      https://www.seti.org/news/why-do-some-solar-eruptions-fail
    • DeepSkyExplorer
      New AARO Reports Shed Light on Military UAP Encounters
      By DeepSkyExplorer
      Hey everyone, I just came across some recent reports from the All-domain Anomaly Resolution Office (AARO) regarding various military encounters with UAPs. The findings are available through a government document search at war.gov, and it's fascinating to read about the specifics of these incidents. The reports seem to provide a more structured approach to analyzing these encounters compared to previous attempts, which is a step in the right direction for transparency.
      One thing that stood out to me was the emphasis on data collection and the various methods being employed to make sense of these sightings. It’s clear that there’s a serious effort underway to understand what’s out there, especially considering the technology involved in some of these military encounters. I noticed they’re not just looking at visual data but also incorporating radar and other sensor inputs, which could lead to a more comprehensive understanding of these phenomena.
      However, while some reports do confirm UAP sightings, they often stop short of identifying what these phenomena actually are, which leaves a lot to speculation. It’s a bit frustrating because we know there are instances where these objects have exhibited capabilities far beyond our current technology. But the reports do seem to be taking a more scientific approach to investigation, which is encouraging.
      I’m curious if anyone else has had a chance to dive into these documents? What do you think about the level of detail and the investigation methods being used? Do you feel like we’re getting closer to some real answers, or is this just another round of vague acknowledgments? You can check out the details of these reports on the AARO’s page linked here: https://www.war.gov/UFO/search/uap/. Would love to hear your thoughts on this!
×
×
  • Create New...