Category Archives: Astronomy

This image, taken with the Atacama Large Millimeter/submillimeter Array (ALMA), in which ESO is a partner, shows the young planetary system PDS 70, located nearly 400 light-years away from Earth. The system features a star at its centre, around which the planet PDS 70 b (highlighted with a solid yellow circle) is orbiting. On the same orbit as PDS 70b, indicated by a solid yellow ellipse, astronomers have detected a cloud of debris (circled by a yellow dotted line) that could be the building blocks of a new planet or the remnants of one already formed. The ring-like structure that dominates the image is a circumstellar disc of material, out of which planets are forming. There is in fact another planet in this system: PDS 70c, seen at 3 o’clock right next to the inner rim of the disc.

Using the Atacama Large Millimeter/submillimeter Array (ALMA), astronomers have found the possible ‘sibling’ of a planet orbiting a distant star. The team has detected a cloud of debris that might be sharing this planet’s orbit and which, they believe, could be the building blocks of a new planet or the remnants of one already formed. If confirmed, this discovery would be the strongest evidence yet that two exoplanets can share one orbit.

“Two decades ago it was predicted in theory that pairs of planets of similar mass may share the same orbit around their star, the so-called Trojan or co-orbital planets. For the first time, we have found evidence in favour of that idea,”

says Olga Balsalobre-Ruza, a student at the Centre for Astrobiology in Madrid, Spain who led the paper published today in Astronomy & Astrophysics.

Trojans, rocky bodies in the same orbit as a planet, are common in our own Solar System [1], the most famous example being the Trojan asteroids of Jupiter — more than 12 000 rocky bodies that are in the same orbit around the Sun as the gas giant. Astronomers have predicted that Trojans, in particular Trojan planets, could also exist around a star other than our Sun, but evidence for them is scant.

“Exotrojans [Trojan planets outside the Solar System] have so far been like unicorns: they are allowed to exist by theory but no one has ever detected them,”

says co-author Jorge Lillo-Box, a senior researcher at the Centre for Astrobiology.

Now, an international team of scientists have used ALMA, in which ESO is a partner, to find the strongest observational evidence yet that Trojan planets could exist — in the PDS 70 system. This young star is known to host two giant, Jupiter-like planets, PDS 70b and PDS 70c. By analysing archival ALMA observations of this system, the team spotted a cloud of debris at the location in PDS 70b’s orbit where Trojans are expected to exist.

Trojans occupy the so-called Lagrangian zones, two extended regions in a planet’s orbit where the combined gravitational pull of the star and the planet can trap material. Studying these two regions of PDS 70b’s orbit, astronomers detected a faint signal from one of them, indicating that a cloud of debris with a mass up to roughly two times that of our Moon might reside there.

The team believes this cloud of debris could point to an existing Trojan world in this system, or a planet in the process of forming.

“Who could imagine two worlds that share the duration of the year and the habitability conditions? Our work is the first evidence that this kind of world could exist,” […] “We can imagine that a planet can share its orbit with thousands of asteroids as in the case of Jupiter, but it is mind blowing to me that planets could share the same orbit.”

[says Balsalobre-Ruza.]

“Our research is a first step to look for co-orbital planets very early in their formation,”

says co-author Nuria Huélamo, a senior researcher at the Centre for Astrobiology.

“It opens up new questions on the formation of Trojans, how they evolve and how frequent they are in different planetary systems,”

adds Itziar De Gregorio-Monsalvo, ESO Head of the Office for Science in Chile, who also contributed to this research.

To fully confirm their detection, the team will need to wait until after 2026, when they will aim to use ALMA to see if both PDS 70b and its sibling cloud of debris move significantly along their orbit together around the star.

“This would be a breakthrough in the exoplanetary field,”

says Balsalobre-Ruza.

“The future of this topic is very exciting and we look forward to the extended ALMA capabilities, planned for 2030, which will dramatically improve the array’s ability to characterise Trojans in many other stars,”

concludes De Gregorio-Monsalvo.

Notes

[1] When asteroids in Jupiter’s orbit were first discovered, they were named after heroes of the Trojan war , giving rise to the name Trojans to refer to these objects.

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Night sky highlights for July 2023

July 2, 2023 TopSpacer

** What’s Up: July 2023 Skywatching Tips from NASA – NASA JPL

What are some skywatching highlights in July 2023?

Mars and Venus start the month close together, but part ways and head lower as July goes on. Mars appears very near Regulus in Leo on the 9th and 10th. Saturn and Jupiter rule the night, along with bright star Fomalhaut. And July is prime time for viewing the Milky Way core from dark sky locations.

0:00 Intro
0:12 Mars & Venus in the evening
0:31 Mars close to Regulus
1:07 Saturn & Jupiter in the morning
1:49 Fomalhaut’s debris disk
2:38 Viewing the Milky Way
3:17 July Moon phases

Additional information about topics covered in this episode of What’s Up, along with still images from the video, and the video transcript, are available at https://solarsystem.nasa.gov/skywatch….

** Tonight’s Sky: July 2023 – Space Telescope Science Institute – Tonight’s Sky

In July, find the Scorpius constellation to identify the reddish supergiant Antares, which will lead you to discover a trio of globular star clusters. Keep watching for space-based views of these densely packed, spherical collections of ancient stars, as well as three nebulas: the Swan Nebula, the Lagoon Nebula, and the Trifid Nebula.

** What to see in the night sky: July 2023 – BBC Sky at Night Magazine

Pete Lawrence and Paul Abel reveal what’s visible in the night sky this month, including Mercury and Venus, a (somewhat) brightening Jupiter, the Perseid meteor shower, minor planet Vesta, and Comet C/2020 V2 (ZTF).

** Sky & Telescope’s Sky Tour Podcast – July 2023 – Sky & Telescope Youtube

Our monthly Sky Tour #astronomy #podcast provides an informative and entertaining 10-minute guided tour of the nighttime sky. Listen to the July episode and take the measure of #Earth’s orbit; track down #mars, #mercury, and #venus, and take a poke at the celestial scorpion, #scorpious.

Listen and subscribe to this podcast at https://skyandtelescope.org/observing/ and don’t forget to subscribe to S&T’s YouTube channel to get alerts about new videos, including this monthly podcast.

Night sky highlights for June 2023

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** What’s Up: June 2023 Skywatching Tips from NASA – NASA JPL

What are some skywatching highlights in June 2023?
Mars and Venus draw closer throughout the month, while Saturn leads Jupiter into the morning sky. Bright stars Spica and Arcturus shine brightly overhead on June evenings, along with the Summer Triangle. And the June solstice, on the 21st, has a special claim to fame.

0:00 Intro
0:13 Mars & Venus in the evening
1:00 Saturn & Jupiter in the morning
1:19 Bright stars of June
2:22 June solstice
3:42 June Moon phases

** Tonight’s Sky: June 2023 – Space Telescope Science Institute – Tonight’s Sky

Though the nights are shorter in June, they are filled with fine sights. Look for the Hercules constellation, which will lead you to a globular star cluster with hundreds of thousands of densely packed stars. You can also spot Draco the dragon, which will point you to the Cat’s Eye Nebula. Keep watching for space-based views of globular star clusters and the nebula.

** What to see in the night sky: June 2023 – BBC Sky at Night Magazine

Pete Lawrence and Paul Abel reveal what you can see in the night sky this month, including Mars, Venus and the Beehive Cluster, the Summer Solstice and the Summer Triangle.

** Sky & Telescope’s Sky Tour Podcast – June 2023 – Sky & Telescope Youtube

Our monthly Sky Tour #astronomy #podcast provides an informative and entertaining 10-minute guided tour of the nighttime sky. Listen to the June episode and mark the Sun’s #solstice; follow the #Moon through its phases; watch #Venus and #Mars dance in the evening sky; track down a couple of faint #constellations; and shine a spotlight on the #star #Arcturus.

ESO: Observation of distant gas clouds formed from the first stars

May 3, 2023 TopSpacer

The latest report from the European Southern Observatory (ESO):

Astronomers find distant gas clouds
with leftovers of the first stars

This artist’s impression shows a distant gas cloud that contains different chemical elements, illustrated here with schematic representations of various atoms. Using ESO’s Very Large Telescope, astronomers have detected three distant gas clouds whose chemical composition matches what we expect from the explosions of the first stars that appeared in the Universe. These early stars can be studied indirectly by analysing the chemical elements they dispersed into the surrounding environment after they died in supernova explosions. The three distant gas clouds detected in this study are rich in carbon, oxygen, and magnesium, but poor in iron. This is exactly the signature expected from the explosions of the first stars.

Using ESO’s Very Large Telescope (VLT), researchers have found for the first time the fingerprints left by the explosion of the first stars in the Universe. They detected three distant gas clouds whose chemical composition matches what we expect from the first stellar explosions. These findings bring us one step closer to understanding the nature of the first stars that formed after the Big Bang.

“For the first time ever, we were able to identify the chemical traces of the explosions of the first stars in very distant gas clouds,”

says Andrea Saccardi, a PhD student at the Observatoire de Paris – PSL, who led this study during his master’s thesis at the University of Florence.

Researchers think that the first stars that formed in the Universe were very different from the ones we see today. When they appeared 13.5 billion years ago, they contained just hydrogen and helium, the simplest chemical elements in nature [1]. These stars, thought to be tens or hundreds of times more massive than our Sun, quickly died in powerful explosions known as supernovae, enriching the surrounding gas with heavier elements for the first time. Later generations of stars were born out of that enriched gas, and in turn ejected heavier elements as they too died. But the very first stars are now long gone, so how can researchers learn more about them?

“Primordial stars can be studied indirectly by detecting the chemical elements they dispersed in their environment after their death,”

says Stefania Salvadori, Associate Professor at the University of Florence and co-author of the study published today in the Astrophysical Journal.

Using data taken with ESO’s VLT in Chile, the team found three very distant gas clouds, seen when the Universe was just 10–15% of its current age, and with a chemical fingerprint matching what we expect from the explosions of the first stars. Depending on the mass of these early stars and the energy of their explosions, these first supernovae released different chemical elements such as carbon, oxygen and magnesium, which are present in the outer layers of stars. But some of these explosions were not energetic enough to expel heavier elements like iron, which is found only in the cores of stars. To search for the telltale sign of these very first stars that exploded as low energy supernovae, the team therefore looked for distant gas clouds poor in iron but rich in the other elements. And they found just that: three faraway clouds in the early Universe with very little iron but plenty of carbon and other elements — the fingerprint of the explosions of the very first stars.

This peculiar chemical composition has also been observed in many old stars in our own galaxy, which researchers consider to be second-generation stars that formed directly from the ‘ashes’ of the first ones. This new study has found such ashes in the early Universe, thus adding a missing piece to this puzzle.

“Our discovery opens new avenues to indirectly study the nature of the first stars, fully complementing studies of stars in our galaxy,”

explains Salvadori.

This diagram illustrates how astronomers can analyse the chemical composition of distant clouds of gas using the light of a background object like a quasar as a beacon. When the light of the quasar passes through the gas cloud, the chemical elements in it absorb different colours or wavelengths, leaving dark lines in the spectrum of the quasar. Each element leaves a different set of lines, so by studying the spectrum astronomers can work out the chemical composition of the intervening gas cloud.

To detect and study these distant gas clouds, the team used light beacons known as quasars — very bright sources powered by supermassive black holes at the centres of faraway galaxies. As the light from a quasar travels through the Universe, it passes through gas clouds where different chemical elements leave an imprint on the light.

To find these chemical imprints, the team analysed data on several quasars observed with the X-shooter instrument on ESO’s VLT. X-shooter splits light into an extremely wide range of wavelengths, or colours, which makes it a unique instrument with which to identify many different chemical elements in these distant clouds.

This study opens new windows for next generation telescopes and instruments, like ESO’s upcoming Extremely Large Telescope (ELT) and its high-resolution ArmazoNes high Dispersion Echelle Spectrograph (ANDES).

“With ANDES at the ELT we will be able to study many of these rare gas clouds in greater detail, and we will be able to finally uncover the mysterious nature of the first stars,”

concludes Valentina D’Odorico, a researcher at the National Institute of Astrophysics in Italy and co-author of the study.

Notes

[1] Minutes after the Big Bang the only elements present in the Universe were the three lightest ones: hydrogen, helium and very small traces of lithium. Heavier elements were formed much later on in stars.

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Night sky highlights for May 2023

May 1, 2023 TopSpacer

** What’s Up: May 2023 Skywatching Tips from NASA – NASA JPL

What are some skywatching highlights in May 2023?

Venus reaches its highest point in the evening sky for the year, while Jupiter disappears behind the Moon for some U.S. observers. Plus, some key differences in the Southern Hemisphere’s skies compared to those of the North.

0:00 Intro
0:12 Moon & planet pairings
1:16 Venus at its highest
1:38 Skies of the Southern Hemisphere
3:48 May Moon phases

** Tonight’s Sky: May 2023 – Space Telescope Science Institute – Tonight’s Sky

In May, we are looking away from the crowded, dusty plane of our own galaxy toward a region where the sky is brimming with distant galaxies. Locate Virgo to find a concentration of roughly 2,000 galaxies and search for Coma Berenices to identify many more. Keep watching for space-based views of galaxies like the Sombrero Galaxy, M87, and M64.

** What to see in the night sky: May 2023 – BBC Sky at Night Magazine

Astronomers Pete Lawrence and Paul Abel reveal the best things to see in the night sky this month, including catching Venus before it disappears, the daytime lunar occultation of Jupiter, the Moon and the tongue-twisting stars of Libra!

** Sky & Telescope’s Sky Tour Podcast – May 2023 – Sky & Telescope Youtube

Our monthly Sky Tour #astronomy #podcast provides an informative and entertaining 10-minute guided tour of the nighttime sky. Listen to the May episode and look for tiny bits of #halleyscomet; watch the #Moon cover up #Jupiter; track down a couple of evening #planets; and take stock of bright #stars in the late-spring sky.