Tag Archives: interstellar matter

This image shows an artist’s impression of what the surface of the 2I/Borisov comet might look like.  2I/Borisov was a visitor from another planetary system that passed by our Sun in 2019, allowing astronomers a unique view of an interstellar comet. While telescopes on Earth and in space captured images of this comet, we don’t have any close-up observations of 2I/Borisov. It is therefore up to artists to create their own ideas of what the comet’s surface might look like, based on the scientific information we have about it. (SO/M. Kormesser)

Interstellar visitor 2I/Borisov is the most pristine comet ever observed

As an interstellar visitor–an object from outside the solar system–the rogue comet 2I/Borisov is already a source of great interest for astronomers. But researchers have now also discovered that this interstellar comet is composed of pristine material similar to that which exists when star systems first form.

Not only does this make 2I/Borisov even more exciting than previously believed, it means that studying the material that composes it and its coma –an envelope of gas and dust that surround comets– could unlock secrets of planetary system formation.

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. (ESO/O. Hainaut)
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. (ESO/O. Hainaut)

“2I/Borisov could represent the first truly pristine comet ever observed,” says Stefano Bagnulo of the Armagh Observatory and Planetarium, Northern Ireland, UK. The astronomer tells ZME Science: “We presume this is because it has travelled in the interstellar medium without interacting with any other stars before reaching the Sun.”

Bagnulo is the lead author of one of two papers published in the Nature family of journals detailing new in-depth analysis of 2I/Borisov.

Reflecting on 2I/Borisov

The team was able to make its detailed study of 2I/Borisov–the second interstellar comet found trespassing in our solar system after the cigar-shaped Oumuamua–using the Very Large Telescope (VLT) located in the Acatma Desert, Northern Chile.

In particular, they employed the FOcal Reducer and low dispersion Spectrograph (FORS2) instrument–a device capable of taking mages of relatively large areas of the sky with very high sensitivity–and a technique called polarimetry to unlock the comet’s secrets.

“Sunlight scattered by material, for instance, reflected by a surface, is partially polarised,” explains Bagnulo comparing this to polaroid sunglasses which absorb the polarised component of the light and thus dampen reflected light suppressing glare. “In astronomy, we are interested in that polarised radiation because it carries information about the structure and composition of the reflecting surface or scattering material.”

Bagnulo continues by explaining that because light reflected by a darker object is polarised more than the light reflected by a brighter object, polarimetry may be used to estimate the albedo of an asteroid. This makes it a tool regularly used to study comets and allowed the team to compare 2I/Borisov to comets that begin life in our solar system.

“We found that the polarimetric behaviour of 2I/Borisov is different than that of all other comets of our solar system, except for one, Comet Hale-Bopp,” Bagnulo says. “We suggest that this is because Hale-Bopp is a pristine comet.”

It also implies that 2I/Borisov and Halle-Bopp formed in similar environments, thus giving us a good picture of conditions in other planetary systems.

Whilst, Bagnulo and his team were conducting this research with data collected by the VLT, another team was using a different method to examine the material that comprises this interstellar comet.

The Secrets in the Dust of 2I/Borisov

Bin Yang, is an astronomer at ESO in Chile, who also took advantage of 2I/Borisov’s intrusion into the solar system to study this mysterious comet, but using the Atacama Large Millimeter/submillimeter Array (ALMA).

This image shows an artist’s impression of what the surface of the 2I/Borisov comet might look like.     2I/Borisov was a visitor from another planetary system that passed by our Sun in 2019, allowing astronomers a unique view of an interstellar comet. While telescopes on Earth and in space captured images of this comet, we don’t have any close-up observations of 2I/Borisov. It is therefore up to artists to create their own ideas of what the comet’s surface might look like, based on the scientific information we have about it. (SO/M. Kormesser)
This image shows an artist’s impression of what the surface of the 2I/Borisov comet might look like.  2I/Borisov was a visitor from another planetary system that passed by our Sun in 2019, allowing astronomers a unique view of an interstellar comet. While telescopes on Earth and in space captured images of this comet, we don’t have any close-up observations of 2I/Borisov. It is therefore up to artists to create their own ideas of what the comet’s surface might look like, based on the scientific information we have about it. (SO/M. Kormesser)

“I had the idea of observing the thermal emission from the dust particles in the coma of 2I/Borisov using ALMA. My co-author Aigen Li constructed theoretical models to fit the ALMA observation and set constraints on the dust properties,” Yang, the lead author of the second paper detailing the 2I/Borisov investigation, tells ZME Science. “The composition of 2I/Borisov is similar to solar system comets, consists of dust and various ices. The major ices are water ice, carbon monoxide ice and the minor species include hydrogen cyanide and ammonia.”

Yang goes on to explain that the team was not able to precisely determine the composition of 2I/Borisov’s dust component. The astronomer adds that it could be composed of silicates or carbonaceous materials or a mixture of both.

This image shows an artist’s close-up view of what the surface of the comet might look like.  2I/Borisov was a visitor from another planetary system that passed by our Sun in 2019, allowing astronomers a unique view of an interstellar comet. While telescopes on Earth and in space captured images of this comet, we don’t have any close-up observations of 2I/Borisov. It is therefore up to artists to create their own ideas of what the comet’s surface might look like, based on the scientific information we have about it. (ESO/M. Kormesser)
This image shows an artist’s close-up view of what the surface of the comet might look like.  2I/Borisov was a visitor from another planetary system that passed by our Sun in 2019, allowing astronomers a unique view of an interstellar comet. While telescopes on Earth and in space captured images of this comet, we don’t have any close-up observations of 2I/Borisov. It is therefore up to artists to create their own ideas of what the comet’s surface might look like, based on the scientific information we have about it. (ESO/M. Kormesser)

The team also found that the comet’s coma contains compact pebbles and grains of around 1mm and above.

Additionally, as 2I/Borisov neared the Sun the relative amounts of water and carbon they detected from it changed quite drastically.

“We found that the dust coma of Borisov consists of compact, millimeter-sized and larger pebble-like grains, which formed in the inner region near the central star,” Yang says. “We also found the cometary nucleus consists of components formed at different locations in its home system.”

“Our observations suggest that Borisov’s system exchanged materials between the inner regions and the outer regions that are far from the central star, perhaps due to gravitational stirring by giant planets much like in our own solar system.”

Bin Yang, ESO.

These characteristics indicate that 2I/Borisov formed by collecting materials from different locations in its own planetary system. It also imnplies that the system from which it originated likelty featured the exchange of materials between its inner and outer regions. Something that Yang says is also common in our solar system.

“So, it is possible that chaotic material exchanging processes are common phenomena for young planetary systems,” says Yang. “We want to know if other planetary systems form like our own. But we cannot study these systems to the level of their individual comets.”

“Interstellar objects represent the building blocks of planets around other stars. Comet Borisov provides a rare and valuable link between our own solar system and other planetary systems.”

The Journey of 2I/Borisov

2I/Borisov was first discovered by Gennedy Borisov, an amateur astronomer and telescope maker, in August 2019. It was only the second visitor from outside the solar system to be found within our planetary system. That means that as it passed the Sun it presented a unique opportunity to compare conditions in our small corner of the galaxy to those found in other planetary systems.

“2I/Borisov is quite a small comet and it didn’t get very close to the Earth and the Sun, so the emission from this comet is quite weak. We were happily surprised that we actually detected the thermal emission from this alien comet. Because of this detection, we are able to set constraints on the dust properties of this comet,” says Yang. “Comets in other planetary systems are simply too far away and too small to be seen by our telescopes.

“We are extremely lucky to find a comet that is from a planetary system far far away from us. Even more luckily, we managed to take many pictures and spectra of this alien comet during its short visit.”

Bin Yang, ESO.

As Yang points out, 2I/Borisov is only in our solar system for a short time before it must continue its interstellar journey, so the time available to astronomers to study it is limited. But, with interstellar visitors to the solar system believed to be fairly common, but difficult to spot, improving telescope technology could offer future opportunities to study other objects with similar interstellar origins.

Bagnulo points to both the upcoming Vera C Rubin telescope and ESA’s comet interceptor, set to launch in 2029, as future technology that could help us spot and investigate interstellar comets.

“We expect to detect at least one interstellar object per year,” Yang concludes. “So, we will have more opportunities to study alien materials.”

Buckyballs in space: how complex carbon molecules form in space

An artist’s conception showing spherical carbon molecules known as buckyballs coming out from a planetary nebula — material shed by a dying star. Researchers at the University of Arizona have now created these molecules under laboratory conditions thought to mimic those in their ‘natural’ habitat in space. NASA/JPL-Caltech

The mystery of how complex carbon molecules with a ‘soccer-ball’ type structure–nicknamed buckyballs–came to be found in interstellar space has puzzled scientists for some time.

But now, a team of researchers from the University of Arizona have proposed a potential formation mechanism for carbon-60 (C60)–a spherical molecule comprised of 60 carbon atoms in ring-like structures–in space.

The team discovered that silicon carbide dust left behind by dying stars then bombarded by high energy particles and extreme temperatures could shed silicates leaving behind pure carbon needed to create C60.

Their results are published in the journal Astrophysical Journal Letters.

The detection of buckyballs–named for their similarity to the dome-like architecture of Buckminister Fuller– and even larger C70 molecules a few years ago caused a rethink of the theory that such molecules could only be formed in the lab.

Additionally, and more importantly, the discovery overturned the idea that only light molecules–up to around 10 atoms–could be found scattered through interstellar space.

Another surprise emerged from the fact that the molecules detected were pure carbon.

In the lab, C60 is created by blasting together pure carbons sources such as graphite. This process should be almost impossible in the planetary nebulae that the interstellar C60 was found. This is because this environment– debris created in the violent death throes of stars–has about 10,000 hydrogen molecules for every carbon molecule.

“Any hydrogen should destroy fullerene synthesis,” says Jacob Bernal, an astrobiology and chemistry doctoral student and lead author of the paper. “If you have a box of balls, and for every 10,000 hydrogen balls you have one carbon, and you keep shaking them, how likely is it that you get 60 carbons to stick together?

“It’s very unlikely.”


Bernal and his team began investigating this conundrum with the aim of uncovering a potential C60 formation mechanism when they realised that the transmission electron microscope (TEM) located at the Kuiper Materials Imaging and Characterization Facility at the University of Arizona, was able to simulate the planetary nebula environment fairly well.

TEM’s 200,000-volt electron beam is able to probe matter down to 78 picometers in order to see individual atoms. The beam also operates in a vacuum with extremely low pressures. The incredibly low-pressure in TEM is very close to the pressure found in circumstellar environments. But this is more by luck than design.

“It’s not that we necessarily tailored the instrument to have these specific kinds of pressures,” explains study co-author Tom Zega, an associate professor in the Univerity of Arizona Lunar and Planetary Lab. “These instruments operate at those kinds of very low pressures not because we want them to be like stars, but because molecules of the atmosphere get in the way when you’re trying to do high-resolution imaging with electron microscopes.”

The team drafted the assistance of the U.S. Department of Energy’s Argonne National Lab, Chicago, which has a TEM capable of studying the radiation responses of materials. Placing silicon carbide–a common form of dust produced by stars– in the low-pressure environment of the TEM, the team in Chicago subjected it to temperatures up to 1,830 degrees Fahrenheit whilst bombarding it with high-energy xenon ions.

Tom Zega at the control panel of the 12-foot tall transmission electron microscope at the Kuiper Materials Imaging and Characterization Facility at the UArizona Lunar and Planetary Lab. The instrument revealed that buckyballs had formed in samples exposed to conditions thought to reflect those in planetary nebulae. Daniel Stolte/University Communications

Following this, the sample was returned to the University of Arizona so researchers could employ the higher resolution and better analytical capabilities of the TEM located there. The team’s hypothesis would be validated if they observed the silicon shedding and exposing pure carbon.

“Sure enough, the silicon came off, and you were left with layers of carbon in six-membered ring sets called graphite,” adds co-author Lucy Ziurys, Regents Professor of astronomy, chemistry and biochemistry. “And then when the grains had an uneven surface, five-membered and six-membered rings formed and made spherical structures matching the diameter of C60.

“So, we think we’re seeing C60.”

This work suggests that C60 is derived from the silicon carbide dust made by dying stars–hit by high temperatures, shockwaves and high energy particles. These violent conditions leech silicon from the surface and leaving carbon behind.

These big molecules are dispersed because dying stars eject their material into the interstellar medium – the spaces in between stars – thus accounting for their presence outside of planetary nebulae.

Buckyballs are very stable to radiation, allowing them to survive for billions of years if shielded from the harsh environment of space.

“The conditions in the universe where we would expect complex things to be destroyed are actually the conditions that create them,” says Bernal, also adding that the implications of the findings are endless.

“If this mechanism is forming C60, it’s probably forming all kinds of carbon nanostructures,” Ziurys concludes. “And if you read the chemical literature, these are all thought to be synthetic materials only made in the lab, and yet, interstellar space seems to be making them naturally.”

Original research: “Formation of Interstellar C60 from Silicon Carbide Circumstellar Grains,” The Astrophysical Journal Letters, 2019.

The most exotic material on the planet: researchers find dust from beyond the solar system

Seven particles of dust brought back to Earth by a spacecraft nearly a decade ago appear originate from beyond our solar system. The exotic dust was identified by researchers with the help of 30,000 worldwide citizens.

An optical microscope image of a track through aerogel made by Orion, one of the dust particles believed to be from interstellar space. Photograph: D Frank/Nasa/JSC

The material was collected by the Stardust spacecraft, a 300-kilogram robotic space probe launched by NASA on February 7, 1999. Its primary mission was to collect dust samples from the coma of comet Wild 2, as well as samples of cosmic dust, and return these to Earth for analysis. It was the first such spacecraft of its kind. It featured detectors which worked like cosmic fly-paper, gathering as much dust as possible. In 2006, the shuttle parachuted the detectors onto Earth, where they started to be analyzed.

The specks have all the hallmarks of being created in interstellar space. If the analysis is confirmed, it would be the first time interstellar particles are brought back to Earth to be studied. The dust was probably created by a supernova explosion millions of years ago and shaped by exposure to the harsh extremes of space.

“These are very precious particles,” said Andrew Westphal, a physicist at the University of California in Berkeley, who worked on the dust.

Virtually everything we know about interstellar matter, either ground based, or with space telescopes; studying it directly could provide valuable insights.

 “We seem to be getting our first glimpse of the surprising diversity of interstellar dust particles, which is impossible to explore through astronomical observations alone,” Westphal added.

Aside for these exotic particles, researchers found  more than 50 other particles of spacecraft debris in the Stardust detectors, according to a report published in ScienceAnton Kearsley, a microanalyst who took part in the study at the Natural History Museum in London, says that identifying them is a huge challenge:

“In the end, 30,000 people around the world worked through thousands of digital microscope images of the main part of the collector, the aerogel, and eventually found the tracks that included interstellar dust particles,” he said.

“As the results came in, the numbers and sizes of dust grains were not what we’d expected, and many seemed to have come from strange directions,” he added. “Only by careful plotting of impact directions was the team able to identify the seven particles that must have come from outside the solar system.”