Category Archives: Space Science

ESO: Planet discovered orbiting Barnard’s star, closest single star to our Sun

A new report from the European Southern Observatory (ESO):

Scientists discover planet orbiting closest single star to our Sun

This artist’s impression shows Barnard b, a sub-Earth-mass planet that was discovered orbiting Barnard’s star. Its signal was detected with the ESPRESSO instrument on ESO’s Very Large Telescope (VLT), and astronomers were able to confirm it with data from other instruments. An earlier promising detection in 2018 around the same star could not be confirmed by these data. On this newly discovered exoplanet, which has at least half the mass of Venus but is too hot to support liquid water, a year lasts just over three Earth days.

Using the European Southern Observatory’s Very Large Telescope (ESO’s VLT), astronomers have discovered an exoplanet orbiting Barnard’s star, the closest single star to our Sun. On this newly discovered exoplanet, which has at least half the mass of Venus, a year lasts just over three Earth days. The team’s observations also hint at the existence of three more exoplanet candidates, in various orbits around the star.

Located just six light-years away, Barnard’s star is the second-closest stellar system — after Alpha Centauri’s three-star group — and the closest individual star to us. Owing to its proximity, it is a primary target in the search for Earth-like exoplanets. Despite a promising detection back in 2018, no planet orbiting Barnard’s star had been confirmed until now.

The discovery of this new exoplanet — announced in a paper published today in the journal Astronomy & Astrophysics — is the result of observations made over the last five years with ESO’s VLT, located at Paranal Observatory in Chile.

“Even if it took a long time, we were always confident that we could find something,”

says Jonay González Hernández, a researcher at the Instituto de Astrofísica de Canarias in Spain, and lead author of the paper. The team were looking for signals from possible exoplanets within the habitable or temperate zone of Barnard’s star — the range where liquid water can exist on the planet’s surface. Red dwarfs like Barnard’s star are often targeted by astronomers since low-mass rocky planets are easier to detect there than around larger Sun-like stars. [1]

Barnard b [2], as the newly discovered exoplanet is called, is twenty times closer to Barnard’s star than Mercury is to the Sun. It orbits its star in 3.15 Earth days and has a surface temperature around 125 °C.

“Barnard b is one of the lowest-mass exoplanets known and one of the few known with a mass less than that of Earth. But the planet is too close to the host star, closer than the habitable zone,” explains González Hernández. “Even if the star is about 2500 degrees cooler than our Sun, it is too hot there to maintain liquid water on the surface.

For their observations, the team used ESPRESSO, a highly precise instrument designed to measure the wobble of a star caused by the gravitational pull of one or more orbiting planets. The results obtained from these observations were confirmed by data from other instruments also specialised in exoplanet hunting: HARPS at ESO’s La Silla Observatory, HARPS-N and CARMENES. The new data do not, however, support the existence of the exoplanet reported in 2018.

In addition to the confirmed planet, the international team also found hints of three more exoplanet candidates orbiting the same star. These candidates, however, will require additional observations with ESPRESSO to be confirmed.

“We now need to continue observing this star to confirm the other candidate signals,”

says Alejandro Suárez Mascareño, a researcher also at the Instituto de Astrofísica de Canarias and co-author of the study.

But the discovery of this planet, along with other previous discoveries such as Proxima b and d, shows that our cosmic backyard is full of low-mass planets.”

ESO’s Extremely Large Telescope (ELT), currently under construction, is set to transform the field of exoplanet research. The ELT’s ANDES instrument will allow researchers to detect more of these small, rocky planets in the temperate zone around nearby stars, beyond the reach of current telescopes, and enable them to study the composition of their atmospheres.

Graphic representation of the relative distances between the nearest stars and the Sun. Barnard’s star is the second closest star system to the Sun, and the nearest single star to us.

Notes

[1] Astronomers target cool stars, like red dwarfs, because their temperate zone is much closer to the star than that of hotter stars, like the Sun. This means that the planets orbiting within their temperate zone have shorter orbital periods, allowing astronomers to monitor them over several days or weeks, rather than years. In addition, red dwarfs are much less massive than the Sun, so they are more easily disturbed by the gravitational pull of the planets around them and thus they wobble more strongly.

[2] It’s common practice in science to name exoplanets by the name of their host star with a lowercase letter added to it, ‘b’ indicating the first known planet, ’c’ the next one, and so on. The name Barnard b was therefore also given to a previously suspected planet candidate around Barnard’s star, which scientists were unable to confirm.

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When the Heavens Went on Sale:
The Misfits and Geniuses Racing to Put Space Within Reach

ESO telescope captures most detailed infrared map of Milky Way ever

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

ESO telescope captures
the most detailed infrared map ever of our Milky Way

This collage highlights a small selection of regions of the Milky Way imaged as part of the most detailed infrared map ever of our galaxy. Here we see, from left to right and top to bottom: NGC 3576, NGC 6357, Messier 17, NGC 6188, Messier 22 and NGC 3603. All of them are clouds of gas and dust where stars are forming, except Messier 22, which is a very dense group of old stars. The images were captured with ESO’s Visible and Infrared Survey Telescope for Astronomy (VISTA) and its infrared camera VIRCAM. The gigantic map to which these images belong contains 1.5 billion objects. The data were gathered over the course of 13 years as part of the VISTA Variables in the Vía Láctea (VVV) survey and its companion project, the VVV eXtended survey (VVVX).

Astronomers have published a gigantic infrared map of the Milky Way containing more than 1.5 billion objects ― the most detailed one ever made. Using the European Southern Observatory’s VISTA telescope, the team monitored the central regions of our Galaxy over more than 13 years. At 500 terabytes of data, this is the largest observational project ever carried out with an ESO telescope.

We made so many discoveries, we have changed the view of our Galaxy forever,

says Dante Minniti, an astrophysicist at Universidad Andrés Bello in Chile who led the overall project.

This record-breaking map comprises 200 000 images taken by ESO’s VISTA ― the Visible and Infrared Survey Telescope for Astronomy. Located at ESO’s Paranal Observatory in Chile, the telescope’s main purpose is to map large areas of the sky. The team used VISTA’s infrared camera VIRCAM, which can peer through the dust and gas that permeates our galaxy. It is therefore able to see the radiation from the Milky Way’s most hidden places, opening a unique window onto our galactic surroundings.

This gigantic dataset [1] covers an area of the sky equivalent to 8600 full moons, and contains about 10 times more objects than a previous map released by the same team back in 2012. It includes newborn stars, which are often embedded in dusty cocoons, and globular clusters –– dense groups of millions of the oldest stars in the Milky Way. Observing infrared light means VISTA can also spot very cold objects, which glow at these wavelengths, like brown dwarfs (‘failed’ stars that do not have sustained nuclear fusion) or free-floating planets that don’t orbit a star.

This image from ESO’s VISTA telescope captures a celestial landscape of vast, glowing clouds of gas and tendrils of dust surrounding hot young stars. This infrared view reveals the stellar nursery known as NGC 6357 in a new light. It was taken as part of the VISTA Variables in the Vía Láctea (VVV) survey, which is currently scanning the Milky Way in a bid to map our galaxy’s structure and explain how it formed.

The observations began in 2010 and ended in the first half of 2023, spanning a total of 420 nights. By observing each patch of the sky many times, the team was able to not only determine the locations of these objects, but also track how they move and whether their brightness changes. They charted stars whose luminosity changes periodically that can be used as cosmic rulers for measuring distances [2]. This has given us an accurate 3D view of the inner regions of the Milky Way, which were previously hidden by dust. The researchers also tracked hypervelocity stars — fast-moving stars catapulted from the central region of the Milky Way after a close encounter with the supermassive black hole lurking there.

The new map contains data gathered as part of the VISTA Variables in the Vía Láctea (VVV) survey [3] and its companion project, the VVV eXtended (VVVX) survey.

The project was a monumental effort, made possible because we were surrounded by a great team,”

says Roberto Saito, an astrophysicist at the Universidade Federal de Santa Catarina in Brazil and lead author of the paper published today in Astronomy & Astrophysics on the completion of the project.

The VVV and VVVX surveys have already led to more than 300 scientific articles. With the surveys now complete, the scientific exploration of the gathered data will continue for decades to come. Meanwhile, ESO’s Paranal Observatory is being prepared for the future: VISTA will be updated with its new instrument 4MOST and ESO’s Very Large Telescope (VLT) will receive its MOONS instrument. Together, they will provide spectra of millions of the objects surveyed here, with countless discoveries to be expected.

Notes

[1] The dataset is too large to release as a single image, but the processed data and objects catalogue can be accessed in the ESO Science Portal.

[2] One way to measure the distance to a star is by comparing how bright it appears as seen from Earth to how intrinsically bright it is; but the latter is often unknown. Certain types of stars change their brightness periodically, and there is a very strong connection between how quickly they do this and how intrinsically luminous they are. Measuring these fluctuations allows astronomers to work out how luminous these stars are, and therefore how far away they lie.

[3] Vía Láctea is the Latin name for the Milky Way.

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When the Heavens Went on Sale:
The Misfits and Geniuses Racing to Put Space Within Reach

ESO: Surface bubbles of another star tracked in highest detail ever

A new report from the European Southern Observatory (ESO):

Astronomers track bubbles on star’s surface
in most detailed video yet

Astronomers have captured a sequence of images of a star other than the Sun in enough detail to track the motion of bubbling gas on its surface. The images of the star, R Doradus, were obtained with the Atacama Large Millimeter/submillimeter Array (ALMA), a telescope co-owned by ESO, in July and August 2023. This panel shows three of these real images, taken with ALMA on 18 July, 27 July and 2 August 2023. The giant bubbles — 75 times the size of the Sun — seen on the star’s surface are the result of convection motions inside the star. The size of the Earth’s orbit is shown for scale.

For the first time, astronomers have captured images of a star other than the Sun in enough detail to track the motion of bubbling gas on its surface. The images of the star, R Doradus, were obtained with the Atacama Large Millimeter/submillimeter Array (ALMA), a telescope co-owned by the European Southern Observatory (ESO), in July and August 2023. They show giant, hot bubbles of gas, 75 times the size of the Sun, appearing on the surface and sinking back into the star’s interior faster than expected.

“This is the first time the bubbling surface of a real star can be shown in such a way,“ [1]

says Wouter Vlemmings, a professor at Chalmers University of Technology, Sweden, and lead author of the study published today in Nature.

“We had never expected the data to be of such high quality that we could see so many details of the convection on the stellar surface.”

Stars produce energy in their cores through nuclear fusion. This energy can be carried out towards the star’s surface in huge, hot bubbles of gas, which then cool down and sink — like a lava lamp. This mixing motion, known as convection, distributes the heavy elements formed in the core, such as carbon and nitrogen, throughout the star. It is also thought to be responsible for the stellar winds that carry these elements out into the cosmos to build new stars and planets.

Convection motions had never been tracked in detail in stars other than the Sun, until now. By using ALMA, the team were able to obtain high-resolution images of the surface of R Doradus over the course of a month. R Doradus is a red giant star, with a diameter roughly 350 times that of the Sun, located about 180 light-years away from Earth in the constellation Dorado. Its large size and proximity to Earth make it an ideal target for detailed observations. Furthermore, its mass is similar to that of the Sun, meaning R Doradus is likely fairly similar to how our Sun will look like in five billion years, once it becomes a red giant.

“Convection creates the beautiful granular structure seen on the surface of our Sun, but it is hard to see on other stars,”

adds Theo Khouri, a researcher at Chalmers who is a co-author of the study.

“With ALMA, we have now been able to not only directly see convective granules  — with a size 75 times the size of our Sun! — but also measure how fast they move for the first time.”

The granules of R Doradus appear to move on a one-month cycle, which is faster than scientists expected based on how convection works in the Sun.

“We don’t yet know what is the reason for the difference. It seems that convection changes as a star gets older in ways that we don’t yet understand,”

says Vlemmings. Observations like those now made of R Doradus are helping us to understand how stars like the Sun behave, even when they grow as cool, big and bubbly as R Doradus is.

“It is spectacular that we can now directly image the details on the surface of stars so far away, and observe physics that until now was mostly only observable in our Sun,”

concludes Behzad Bojnodi Arbab, a PhD student at Chalmers who was also involved in the study.

Notes

[1] Convection bubbles have been previously observed in detail on the surface of stars, including with the PIONIER instrument on ESO’s Very Large Telescope Interferometer. But the new ALMA observations track the motion of the bubbles in a way that was not possible before.

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When the Heavens Went on Sale:
The Misfits and Geniuses Racing to Put Space Within Reach

ESO: Galaxy suddenly brightened by massive black hole

A new report from the European Southern Observatory (ESO):

Astronomers see a massive black hole awaken in real time

In late 2019, the galaxy SDSS1335+0728 suddenly started shining brighter than ever before and was classified as having an active galactic nucleus, powered by a massive black hole in the galaxy’s core. This is the first time the awakening of a massive black hole has been observed in real time. This artist’s impression shows the growing disc of material being pulled in by the black hole as it feeds on the gas available in its surroundings, making the galaxy light up.

In late 2019 the previously unremarkable galaxy SDSS1335+0728 suddenly started shining brighter than ever before. To understand why, astronomers have used data from several space and ground-based observatories, including the European Southern Observatory’s Very Large Telescope (ESO’s VLT), to track how the galaxy’s brightness has varied. In a study out today, they conclude that they are witnessing changes never seen before in a galaxy — likely the result of the sudden awakening of the massive black hole at its core.

Imagine you’ve been observing a distant galaxy for years, and it always seemed calm and inactive,

says Paula Sánchez Sáez, an astronomer at ESO in Germany and lead author of the study accepted for publication in Astronomy & Astrophysics.

“Suddenly, its [core] starts showing dramatic changes in brightness, unlike any typical events we’ve seen before.”

This is what happened to SDSS1335+0728, which is now classified as having an ‘active galactic nucleus’ (AGN) — a bright compact region powered by a massive black hole — after it brightened dramatically in December 2019 [1].

Some phenomena, like supernova explosions or tidal disruption events — when a star gets too close to a black hole and is torn apart — can make galaxies suddenly light up. But these brightness variations typically last only a few dozen or, at most, a few hundreds of days. SDSS1335+0728 is still growing brighter today, more than four years after it was first seen to ‘switch on’. Moreover, the variations detected in the galaxy, which is located 300 million light-years away in the constellation Virgo, are unlike any seen before, pointing astronomers towards a different explanation.

The team tried to understand these brightness variations using a combination of archival data and new observations from several facilities, including the X-shooter instrument on ESO’s VLT in Chile’s Atacama Desert [2]. Comparing the data taken before and after December 2019, they found that SDSS1335+0728 is now radiating much more light at ultraviolet, optical, and infrared wavelengths. The galaxy also started emitting X-rays in February 2024.

“This behaviour is unprecedented,”

says Sánchez Sáez, who is also affiliated with the Millennium Institute of Astrophysics (MAS) in Chile.

The most tangible option to explain this phenomenon is that we are seeing how the [core] of the galaxy is beginning to show (…) activity,”

says co-author Lorena Hernández García, from MAS and the University of Valparaíso in Chile.

If so, this would be the first time that we see the activation of a massive black hole in real time.

Massive black holes — with masses over one hundred thousand times that of our Sun — exist at the centre of most galaxies, including the Milky Way.

These giant monsters usually are sleeping and not directly visible,”

explains co-author Claudio Ricci, from the Diego Portales University, also in Chile.

In the case of SDSS1335+0728, we were able to observe the awakening of the massive black hole, [which] suddenly started to feast on gas available in its surroundings, becoming very bright.

[Hernández García says,]

[This] process (…) has never been observed before,”

[…]  Previous studies reported inactive galaxies becoming active after several years, but this is the first time the process itself — the awakening of the black hole — has been observed in real time. Ricci, who is also affiliated with the Kavli Institute for Astronomy and Astrophysics at Peking University, China, adds:

This is something that could happen also to our own Sgr A*, the massive black hole (…) located at the centre of our galaxy,”

but it is unclear how likely this is to happen.

Follow-up observations are still needed to rule out alternative explanations. Another possibility is that we are seeing an unusually slow tidal disruption event, or even a new phenomenon. If it is in fact a tidal disruption event, this would be the longest and faintest such event ever observed.

Regardless of the nature of the variations, [this galaxy] provides valuable information on how black holes grow and evolve,”

Sánchez Sáez says.

We expect that instruments like [MUSE on the VLT or those on the upcoming Extremely Large Telescope (ELT)] will be key in understanding [why the galaxy is brightening].”

Notes

[1] The SDSS1335+0728 galaxy’s unusual brightness variations were detected by the Zwicky Transient Facility (ZTF) telescope in the US. Following that, the Chilean-led Automatic Learning for the Rapid Classification of Events (ALeRCE) broker classified SDSS1335+0728 as an active galactic nucleus.

[2] The team collected archival data from NASA’s Wide-field Infrared Survey Explorer (WISE) and Galaxy Evolution Explorer (GALEX), the Two Micron All Sky Survey (2MASS), the Sloan Digital Sky Survey (SDSS), and the eROSITA instrument on IKI and DLR’s Spektr-RG space observatory. Besides ESO’s VLT, the follow-up observations were conducted with the Southern Astrophysical Research Telescope (SOAR), the W. M. Keck Observatory, and NASA’s Neil Gehrels Swift Observatory and Chandra X-ray Observatory.

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An Infinity of Worlds:
Cosmic Inflation and the Beginning of the Universe

Night sky highlights for May 2024

Check out the night sky this month, May 2024. Here are videos highlighting the top sights to observe.

** What’s Up: May 2024 Skywatching Tips from NASA – NASA JPL

What are some skywatching highlights in May 2024?

Mars and Saturn tussle with the Moon, Mercury makes a brief a.m. appearance, East Coasters can see red giant star Antares emerge from behind the Moon, and the eta Aquariid meteors peak on May 6th.

0:00 Intro
0:15 Moon & planet highlights
1:06 Moon occults Antares
1:53 eta Aquariid meteor shower
3:54 May 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: May 2024 – Space Telescope Science InstituteTonight’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.

About this Series … “Tonight’s Sky” is a monthly video of constellations you can observe in the night sky. The series is produced by the Space Telescope Science Institute, home of science operations for the Hubble Space Telescope, in partnership with NASA’s Universe of Learning. This is a recurring show, and you can find more episodes—and other astronomy videos—at https://hubblesite.org/resource-gallery/tonights-sky.

** What to see in the night sky: May 2024BBC Sky at Night Magazine

What can you see in the night sky tonight? Pete Lawrence and Paul Abel reveal the best things to see in the night sky this month, including the Eta Aquariid meteor shower, Asteroid Pallas at opposition, noctilucent clouds and a tantalising lunar occultation of star cluster M4.

00:00 Intro
00:21 Solar System planets
04:39 Eta Aquariid meteor shower
05:29 The Moon
10:52 Minor planet (2) Pallas opposition
11:16 Noctilucent Clouds
12:39 Lunar occultation of M4
14:03 Arcturus and Boötes
17:45 Corona Borealis
19:47 Keystone asterism in Hercules
21:05 Globular cluster M13
25:19 Spica
26:00 Virgo
27:17 Antares

** Sky & Telescope’s Sky Tour Podcast – May 2024 | Full Moon and the Swiss Army knife of the Sky – Sky & Telescope Youtube

Our monthly Sky Tour #astronomy #podcast provides an informative and entertaining 10-minute guided tour of the nighttime sky. Join us for the May 2024 episode where we highlight this month’s #lunar phases, track down three #planets before dawn, keep alert for bits of #Halley’s #Comet, and get to know the Swiss Army knife of the #night #sky.

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

Learn more about #observing and #stargazing on our website, https://skyandtelescope.org/ and subscribe to our monthly magazine at https://skyandtelescope.org/subscribe.

See also

** Night Sky Notebook May 2024Peter Detterline

** See also:

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Stellaris: People of the Stars