Cosmic Rays Erode Away All But the Largest Interstellar Objects

Artist’s impression of the first interstellar asteroid/comet, "Oumuamua". This unique object was discovered on 19 October 2017 by the Pan-STARRS 1 telescope in Hawaii. Credit: ESO/M. Kornmesser

So far we know of only two interstellar objects (ISO) to visit our Solar System. They are ‘Oumuamua and 2I/Borisov. There’s a third possible ISO named CNEOS 2014-01-08, and research suggests there should be many more.

But a new research letter shows that cosmic ray erosion limits the lifespan of icy ISOs, and though there may be many more of them, they simply don’t last as long as thought. If it’s true, then ‘Oumuamua was probably substantially larger when it started its journey, wherever that was.

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Protoplanetary Disks Throw Out More Material Than Gets Turned Into Planets

When a young solar system gets going it’s little more than a young star and a rotating disk of debris. Accepted thinking says that the swirling debris is swept up in planet formation. But a new study says that much of the matter in the disk could face a different fate.

It may not have the honour of becoming part of a nice stable planet, orbiting placidly and reliably around its host star. Instead, it’s simply discarded. It’s ejected out of the young, still-forming solar system to spend its existence as interstellar objects or as rogue planets.

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When Stars Get Too Close to Each Other, They Cast Out Interstellar Comets and Asteroids

Artist’s impression of the first interstellar asteroid/comet, "Oumuamua". This unique object was discovered on 19 October 2017 by the Pan-STARRS 1 telescope in Hawaii. Credit: ESO/M. Kornmesser

In October 2017, humanity caught its first-ever glimpse of an interstellar object – a visitor from beyond our solar system – passing nearby the Sun. We named it Oumuamua, and its unusual properties fascinated and confounded astronomers. Less than two years later, amateur astronomer Gennady Borisov found a second interstellar object: a comet-like body that began to disintegrate as it passed within 2 AU of the Sun (1 AU equals the distance from Earth to the Sun). Where do these interstellar objects come from? How common are they? With a sample size of just two, it’s difficult to make any generalizations just yet. On the other hand, given what we know about star formation, we can begin to make some inferences about the likely origins of these objects, and what we are likely to see of them in the future.

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Interstellar Comet Borisov is so Pristine, it’s Probably Never Been Close to a Star Before

This image was taken with the FORS2 instrument on ESO’s Very Large Telescope in late 2019, when comet 2I/Borisov passed near the Sun. Since the comet was travelling at breakneck speed, around 175 000 kilometres per hour, the background stars appeared as streaks of light as the telescope followed the comet’s trajectory. The colours in these streaks give the image some disco flair and are the result of combining observations in different wavelength bands, highlighted by the various colours in this composite image.

By comparing our local Comet Hale-Bopp to the interstellar visitor 2I/Borisov, a team of astronomers have concluded that the interloper is perhaps one of the most pristine comets we’ve ever seen.

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Oumuamua Isn’t an Alien Probe, Because Aliens can Learn Everything They Need About us With Telescopes

Artist’s impression of the interstellar object, `Oumuamua, experiencing outgassing as it leaves our Solar System. Credit: ESA/Hubble, NASA, ESO, M. Kornmesser

In the Fall of 2017, the first known interstellar object passed through the Solar System, triggering a revolution in astronomy. Because of the amonolous nature of the object, astronomers from all over the world were at a loss to explain what it was. Neither comet, nor asteroid, nor any other conventional object appeared to fit the bill, leading to all kinds of “exotic” explanations.

A particularly exotic explanation was offered by Harvard Professor Avi Loeb and his former postdoc (Dr. Shmuel Bialy), who hypothesized that ‘Oumuamua could have been an extraterrestrial lightsail. Whereas most rebuttal papers questioned the evidence presented, a new study by astrophysicist and UCLA emeritus professor Ben Zuckerman questioned something else: why would an extraterrestrial civilization want to send a probe our way?

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There Should be About 7 Interstellar Objects Passing Through the Inner Solar System Every Year

A Hubble image of Comet 2IBorisov from October 2019. Image Credit: By NASA, ESA, and D. Jewitt (UCLA) - https://imgsrc.hubblesite.org/hvi/uploads/image_file/image_attachment/31897/STSCI-H-p1953a-f-1106x1106.png, Public Domain, https://commons.wikimedia.org/w/index.php?curid=83146132

In October 19th, 2017, the first interstellar object ever detected flew past Earth on its way out of the Solar System. Less than two years later, a second object was detected, an easily-identified interstellar comet designated as 2I/Borisov. The appearance of these two objects verified earlier theoretical work that concluded that interstellar objects (ISOs) regularly enter our Solar System.

The question of how often this happens has been the subject of considerable research since then. According to a new study led by researchers from the Initiative for Interstellar Studies (i4is), roughly 7 ISOs enter our Solar System every year and follow predictable orbits while they are here. This research could allow us to send a spacecraft to rendezvous with one of these objects in the near future.

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Earth and the Moon Might Have Captured an Old Upper Stage Rocket

The crescent Earth rises above the lunar horizon in this spectacular photograph taken by the Apollo 17 crew in lunar orbit in December, 1972, during NASA’s final lunar landing mission in the Apollo program. Credit: NASA. Image editing and enhancement: Kevin Gill.

Back in September, the Pan-STARRS1 survey telescope noticed an object that followed a slight but distinctly curved path in the sky, a telltale sign that it was captured by Earth’s gravity. Initially, this object was thought to be a near-Earth Asteroid (NEA) and was given a standard designation by the Minor Planet Center (2020 SO). However, the Center for Near-Earth Object Studies (CNEOS) at NASA JPL had another theory.

Based on its orbit and the way solar radiation appeared to be pushing it off course, NASA scientists have since concluded that the object might actually be the spent upper stage booster of the Centaur rocket that launched the Surveyor 2 spacecraft towards the Moon in 1966. This finding could have implications for future surveys that pick up mysterious objects near Earth (‘Oumuamua occur).

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Vera Rubin Should be Able to Detect a Couple of Interstellar Objects a Month

The Vera C. Rubin Observatory is under construction at Cerro Pachon, in Chile. This image shows construction progress in late 2019. The VCO should be able to spot interstellar objects like Oumuamua. Image Credit: Wil O'Mullaine/LSST CC BY-SA 4.0, https://en.wikipedia.org/w/index.php?curid=62504391

The Vera C. Rubin Observatory, formerly the Large Synoptic Survey Telescope (LSST), will commence operations sometime next year. Not wanting to let a perfectly good acronym go to waste, its first campaign will be known as the Legacy Survey of Space and Time (LSST). This ten-year survey will study everything from dark matter and dark energy to the formation of the Milky Way, and small objects in our Solar System.

According to a new study by Amir Siraj and Prof. Abraham Loeb of Harvard University, another benefit of this survey will be the discovery of interstellar objects that regularly enter the Solar Systems. These results, when combined with physical characterizations of the objects, will teach us a great deal about the origin and nature of planetary systems (and could even help us spot an alien probe or two!)

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We Have the Technology to Retrieve a Sample From an Interstellar Object Like Oumuamua

Artist’s impression of the interstellar object, `Oumuamua, experiencing outgassing as it leaves our Solar System. Credit: ESA/Hubble, NASA, ESO, M. Kornmesser

On October 19th, 2017, astronomers were astounded to learn that an interstellar object (named ‘Oumuamua) flew by Earth on its way out of the Solar System. Years later, astronomers are still debating what this object was – a comet fragment, a hydrogen iceberg, or an extraterrestrial solar sail? What’s more, the arrival of 2I/Borisov two years later showed how interstellar objects (ISOs) regularly enter our Solar System (some even stay!)

It’s little wonder then why proposals are in place to design missions that could rendezvous with an interstellar object the next time one passes by. One such mission is Project Lyra, a concept proposed by researchers from the Initiative for Interstellar Studies (i4is). Recently, an international team led from the I4IS drafted a White Paper that was submitted to the 2023-2032 Planetary Science and Astrobiology Decadal Survey.

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Interstellar Comet 2I/Borisov Formed in a Very Cold Environment

Credit: NRAO/AUI/NSF, S. Dagnello

In the summer of 2019, a team of astronomers from NASA, the ESA, and the International Scientific Optical Network (ISON) announced the detection of the comet 2I/Borisov. This comet was the only second interstellar visitor observed passed through our Solar System, coming on the heels of the mysterious ‘Oumuamua. For this reason, astronomers from all over the world watched this comet intently as it made its closest pass to the Sun.

One such group, led by Martin Cordiner and Stefanie Milam of NASA’s Goddard Space Flight Center, observed 2I/Borisov using the ESO’s Atacama Large Millimeter/submillimeter Array (ALMA) in the Chilean Andes. This allowed them to observe the gases 2I/Borisov released as it moved closer to our Sun, thus providing the first-ever chemical composition readings of an interstellar object.

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