New observations with the European Southern Observatory’s Very Large Telescope (ESO’s VLT) indicate that the rogue comet 2I/Borisov, which is only the second and most recently detected interstellar visitor to our Solar System, is one of the most pristine ever observed. Astronomers suspect that the comet most likely never passed close to a star, making it an undisturbed relic of the cloud of gas and dust it formed from.

2I/Borisov was discovered by amateur astronomer Gennady Borisov in August 2019 and was confirmed to have come from beyond the Solar System a few weeks later. “2I/Borisov could represent the first truly pristine comet ever observed,” says Stefano Bagnulo of the Armagh Observatory and Planetarium, Northern Ireland, UK, who led the new study published today in Nature Communications. The team believes that the comet had never passed close to any star before it flew by the Sun in 2019.

Bagnulo and his colleagues used the FORS2 instrument on ESO's VLT, located in northern Chile, to study 2I/Borisov in detail using a technique called polarimetry [1]. Since this technique is regularly used to study comets and other small bodies of our Solar System, this allowed the team to compare the interstellar visitor with our local comets.

The team found that 2I/Borisov has polarimetric properties distinct from those of Solar System comets, with the exception of Hale–Bopp. Comet Hale–Bopp received much public interest in the late 1990s as a result of being easily visible to the naked eye, and also because it was one of the most pristine comets astronomers had ever seen. Prior to its most recent passage, Hale–Bopp is thought to have passed by our Sun only once and had therefore barely been affected by solar wind and radiation. This means it was pristine, having a composition very similar to that of the cloud of gas and dust it — and the rest of the Solar System — formed from some 4.5 billion years ago.

By analysing the polarisation together with the colour of the comet to gather clues on its composition, the team concluded that 2I/Borisov is in fact even more pristine than Hale–Bopp. This means it carries untarnished signatures of the cloud of gas and dust it formed from.

“The fact that the two comets are remarkably similar suggests that the environment in which 2I/Borisov originated is not so different in composition from the environment in the early Solar System,” says Alberto Cellino, a co-author of the study, from the Astrophysical Observatory of Torino, National Institute for Astrophysics (INAF), Italy.

Olivier Hainaut, an astronomer at ESO in Germany who studies comets and other near-Earth objects but was not involved in this new study, agrees. “The main result — that 2I/Borisov is not like any other comet except Hale–Bopp — is very strong,” he says, adding that “it is very plausible they formed in very similar conditions.”

“The arrival of 2I/Borisov from interstellar space represented the first opportunity to study the composition of a comet from another planetary system and check if the material that comes from this comet is somehow different from our native variety,” explains Ludmilla Kolokolova, of the University of Maryland in the US, who was involved in the Nature Communications research. 

Bagnulo hopes astronomers will have another, even better, opportunity to study a rogue comet in detail before the end of the decade. “ESA is planning to launch Comet Interceptor in 2029, which will have the capability of reaching another visiting interstellar object, if one on a suitable trajectory is discovered,” he says, referring to an upcoming mission by the European Space Agency.

New Hubble Data Suggests There is an Ingredient Missing from Current Dark Matter Theories

 

Observations by the NASA/ESA Hubble Space Telescope and the European Southern Observatory’s Very Large Telescope (VLT) in Chile have found that something is missing.

This missing ingredient may explain why researchers have uncovered an unexpected discrepancy between observations of the dark matter concentrations in a sample of massive galaxy clusters and theoretical computer simulations of how dark matter should be distributed in clusters. 

The new findings indicate that some small-scale concentrations of dark matter produce lensing effects that are 10 times stronger than expected.

The release, images and videos are available on:
https://www.spacetelescope.org/news/heic2016/

Dark matter is the invisible glue that keeps stars, dust, and gas together in a galaxy. This mysterious substance makes up the bulk of a galaxy's mass and forms the foundation of our Universe's large-scale structure. Because dark matter does not emit, absorb, or reflect light, its presence is only known through its gravitational pull on visible matter in space. Astronomers and physicists are still trying to pin down what it is.

Galaxy clusters, the most massive and recently assembled structures in the Universe, are also the largest repositories of dark matter. Clusters are composed of individual member galaxies that are held together largely by the gravity of dark matter.

Mystery of the Dimming of Betelgeuse

 

New observations by the NASA/ESA Hubble Space Telescope suggest that the unexpected dimming of the supergiant star Betelgeuse was most likely caused by an immense amount of hot material ejected into space, forming a dust cloud that blocked starlight coming from Betelgeuse’s surface.

Betelgeuse is an aging, red supergiant star that has swelled in size as a result of complex, evolving changes in the nuclear fusion processes in its core. The star is so large that if it replaced the Sun at the centre of our Solar System, its outer surface would extend past the orbit of Jupiter. 

The unprecedented phenomenon of Betelgeuse’s great dimming, eventually noticeable to even the naked eye, began in October 2019. By mid-February 2020, the brightness of this monster star had dropped by more than a factor of three. 

Read the full release online at: https://www.spacetelescope.org/news/heic2014/?lang

First Observation of a Total Lunar Eclipse By a Space Telescope

 

Taking advantage of a total lunar eclipse, astronomers using the NASA/ESA Hubble Space Telescope have detected ozone in Earth’s atmosphere. This method serves as a proxy for how they will observe Earth-like planets around other stars in the search for life. 

This is the first time a total lunar eclipse was captured from a space telescope and the first time such an eclipse has been studied in ultraviolet wavelengths.

In a new study, Hubble did not look at Earth directly. Instead, astronomers used the Moon as a mirror that reflects the sunlight that has been filtered through Earth’s atmosphere. 

Using a space telescope for eclipse observations is cleaner than ground-based studies because the data is not contaminated by looking through Earth’s atmosphere.

Read the whole news story online at: 

https://www.spacetelescope.org/news/heic2013/?lang

First Ever Image of a Multi-Planet System around a Sun-like Star Captured by ESO Telescope

The European Southern Observatory’s Very Large Telescope (ESO’s VLT) has taken the first ever image of a young, Sun-like star accompanied by two giant exoplanets. Images of systems with multiple exoplanets are extremely rare, and — until now — astronomers had never directly observed more than one planet orbiting a star similar to the Sun. The observations can help astronomers understand how planets formed and evolved around our own Sun.

Just a few weeks ago, ESO revealed a planetary system being born in a new, stunning VLT image. Now, the same telescope, using the same instrument, has taken the first direct image of a planetary system around a star like our Sun, located about 300 light-years away and known as TYC 8998-760-1.

“This discovery is a snapshot of an environment that is very similar to our Solar System, but at a much earlier stage of its evolution,” says Alexander Bohn, a PhD student at Leiden University in the Netherlands, who led the new research published today in The Astrophysical Journal Letters. 

“Even though astronomers have indirectly detected thousands of planets in our galaxy, only a tiny fraction of these exoplanets have been directly imaged,” says co-author Matthew Kenworthy, Associate Professor at Leiden University, adding that “direct observations are important in the search for environments that can support life.”

 The direct imaging of two or more exoplanets around the same star is even more rare; only two such systems have been directly observed so far, both around stars markedly different from our Sun. The new ESO’s VLT image is the first direct image of more than one exoplanet around a Sun-like star. ESO’s VLT was also the first telescope to directly image an exoplanet, back in 2004, when it captured a speck of light around a brown dwarf, a type of ‘failed’ star.

“Our team has now been able to take the first image of two gas giant companions that are orbiting a young, solar analogue,” says Maddalena Reggiani, a postdoctoral researcher from KU Leuven, Belgium, who also participated in the study. The two planets can be seen in the new image as two bright points of light distant from their parent star, which is located in the upper left of the frame (click on the image to view the full frame). 

By taking different images at different times, the team were able to distinguish these planets from the background stars.

PR Image eso2011a

First ever image of a multi-planet system around a Sun-like star

PR Image eso2011b

First ever image of a multi-planet system around a Sun-like star (uncropped, with annotations)

PR Image eso2011c

First ever image of a multi-planet system around a Sun-like star (uncropped, without annotations)

PR Image eso2011d

Location of TYC 8998-760-1 in the constellation of Musca

The two gas giants orbit their host star at distances of 160 and about 320 times the Earth-Sun distance. This places these planets much further away from their star than Jupiter or Saturn, also two gas giants, are from the Sun; they lie at only 5 and 10 times the Earth-Sun distance, respectively. 

The team also found the two exoplanets are much heavier than the ones in our Solar System, the inner planet having 14 times Jupiter’s mass and the outer one six times.

Bohn’s team imaged this system during their search for young, giant planets around stars like our Sun but far younger. The star TYC 8998-760-1 is just 17 million years old and located in the Southern constellation of Musca (The Fly). Bohn describes it as a “very young version of our own Sun.”

Links

• Research paper
• Photos of the VLT
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New All-Sky X-Ray Map from eRosita Space Telescope

This annotated version of the all-sky map points out several galaxy clusters (e.g., Coma, Virgo, Fornax, and Perseus), point sources (e.g., Sco X-1), and extended supernova remnants (SNR). One of the most conspicuous sources is the North Polar Spur, a bubble of hot gas. Its distance is unknown, so astronomers aren't sure if it's a nearby supernova remnant, or a larger shell associated with the galactic center. 
J. Sanders, H. Brunner & eSASS team (MPE) / E. Churazov, M. Gilfanov (on behalf of IKI)

Read more online at: https://skyandtelescope.org/astronomy-news/first-all-sky-map-j