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

First ever binary star found near
our galaxy’s supermassive black hole

An international team of researchers has detected a binary star orbiting close to Sagittarius A*, the supermassive black hole at the centre of our galaxy. It is the first time a stellar pair has been found in the vicinity of a supermassive black hole. The discovery, based on data collected by the European Southern Observatory’s Very Large Telescope (ESO’s VLT), helps us understand how stars survive in environments with extreme gravity, and could pave the way for the detection of planets close to Sagittarius A*.

“Black holes are not as destructive as we thought”

says Florian Peißker, a researcher at the University of Cologne, Germany, and lead author of the study published today in Nature Communications. Binary stars, pairs of stars orbiting each other, are very common in the Universe, but they had never before been found near a supermassive black hole, where the intense gravity can make stellar systems unstable.

This new discovery shows that some binaries can briefly thrive, even under destructive conditions. D9, as the newly discovered binary star is called, was detected just in time: it is estimated to be only 2.7 million years old, and the strong gravitational force of the nearby black hole will probably cause it to merge into a single star within just one million years, a very narrow timespan for such a young system.

“This provides only a brief window on cosmic timescales to observe such a binary system — and we succeeded!”

explains co-author Emma Bordier, a researcher also at the University of Cologne and a former student at ESO.

For many years, scientists also thought that the extreme environment near a supermassive black hole prevented new stars from forming there. Several young stars found in close proximity to Sagittarius A* have disproved this assumption. The discovery of the young binary star now shows that even stellar pairs have the potential to form in these harsh conditions.

“The D9 system shows clear signs of the presence of gas and dust around the stars, which suggests that it could be a very young stellar system that must have formed in the vicinity of the supermassive black hole”

explains co-author Michal Zajaček, a researcher at Masaryk University, Czechia, and the University of Cologne.

The newly discovered binary was found in a dense cluster of stars and other objects orbiting Sagittarius A*, called the S cluster. Most enigmatic in this cluster are the G objects, which behave like stars but look like clouds of gas and dust.

It was during their observations of these mysterious objects that the team found a surprising pattern in D9. The data obtained with the VLT’s ERIS instrument, combined with archival data from the SINFONI instrument, revealed recurring variations in the velocity of the star, indicating D9 was actually two stars orbiting each other.

“I thought that my analysis was wrong,” Peißker says, “but the spectroscopic pattern covered about 15 years, and it was clear this detection is indeed the first binary observed in the S cluster.”

The results shed new light on what the mysterious G objects could be. The team proposes that they might actually be a combination of binary stars that have not yet merged and the leftover material from already merged stars.

The precise nature of many of the objects orbiting Sagittarius A*, as well as how they could have formed so close to the supermassive black hole, remain a mystery. But soon, the GRAVITY+ upgrade to the VLT Interferometer and the METIS instrument on ESO’s Extremely Large Telescope (ELT), under construction in Chile, could change this. Both facilities will allow the team to carry out even more detailed observations of the Galactic centre, revealing the nature of known objects and undoubtedly uncovering more binary stars and young systems.

“Our discovery lets us speculate about the presence of planets, since these are often formed around young stars. It seems plausible that the detection of planets in the Galactic centre is just a matter of time”

concludes Peißker.

Links

• Research paper
• Photos of the VLT
• Find out more about ESO’s Extremely Large Telescope on our dedicated website and press kit
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When the Heavens Went on Sale:
The Misfits and Geniuses Racing to Put Space Within Reach

Check out the night sky this month, December 2024. Here are videos and links to websites highlighting the top sights to observe.

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

What are some skywatching highlights in December 2024?

This month, enjoy dazzling views of Venus as the “Evening Star,” Jupiter at its brightest during opposition, and Mars doubling in brightness, and look for the Winter Triangle. The Geminid meteor shower peaks under challenging moonlight conditions, but you might get lucky and catch a shooting star that week before sunrise!

0:00 Intro
0:14 December planet highlights
1:31 The Winter Stars
1:57 The Winter Triangle
2:42 Geminid Meteor Shower
3:14 December 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….

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

Pete Lawrence and Paul Abel reveal their pick of the best things to see in the night sky this month.

** Sky & Telescope’s Sky Tour Podcast – December 2024 | Jupiter Shines, Winter Stars, and Many Meteors – Sky & Telescope Youtube

Our monthly Sky Tour #astronomy #podcast provides an informative and entertaining 10-minute guided tour of the #night #sky. Join us for the December 2024 episode and mark the #solstice, be amazed by #Jupiter, welcome the arrival of winter’s bright #stars, and prep for what’s usually the year’s best #meteorshower.

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.

See also

• Sky Tour Astronomy Podcast: Upcoming Celestial Events | Sky & Telescope
• Interactive Sky Chart | Map Your Night Sky – Sky & Telescope
• Astronomy Pictures: Sky & Telescope’s Online Gallery Archives | Sky & Telescope

** What’s in the Night Sky: December 2024 – National Space Centre

What’s in the Night Sky: December 2024

Venus, Jupiter, and Mars
Ray Craters on the Moon
✨ Constellation of the Month: Pisces

** What’s in the Sky this Month | December 2024 – High Point Scientific on Youtube

In this episode of What’s in the Sky this Month, Teagan reviews some of the beautiful celestial objects you can see in December 2024!

Chapters
00:00 – Introduction
00:36 – Nearest Neighbors
01:56 – Jupiter at Opposition
02:51 – Geminid Meteor Shower
03:13 – Melotte 20
04:04 – Algol
04:30 – Pleiades
05:37 – Conclusion

** Night Sky Notebook December 2024– Peter Detterline

What you see when you look up into the night skies of December 2024.

** See also:

• • December Night Sky Guide (December 2024) | Farmers’ Almanac
  • December 2024 Night Sky Calendar | Voyageurs Conservancy
  • December 2024: What’s in the sky this month? | Astronomy.com
  • Night sky, December 2024: What you can see tonight [maps] | Space .com
  • Visible planets and night sky guide for December | EarthSky.org
  • 23 Must-See Astronomy Events in the December Night Sky (2024) | SpaceTourismGuide.com
  • Astronomical Events December 2024 | Star Walk

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Stellaris: People of the Stars

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

Astronomers take the first close-up picture
of a star outside our galaxy

“For the first time, we have succeeded in taking a zoomed-in image of a dying star in a galaxy outside our own Milky Way,”

says Keiichi Ohnaka, an astrophysicist from Universidad Andrés Bello in Chile. Located a staggering 160 000 light-years from us, the star WOH G64 was imaged thanks to the impressive sharpness offered by the European Southern Observatory’s Very Large Telescope Interferometer (ESO’s VLTI). The new observations reveal a star puffing out gas and dust, in the last stages before it becomes a supernova.

“We discovered an egg-shaped cocoon closely surrounding the star,” says Ohnaka, the lead author of a study reporting the observations published today in Astronomy & Astrophysics. “We are excited because this may be related to the drastic ejection of material from the dying star before a supernova explosion.”

While astronomers have taken about two dozen zoomed-in images of stars in our galaxy, unveiling their properties, countless other stars dwell within other galaxies, so far away that observing even one of them in detail has been extremely challenging. Up until now.

The newly imaged star, WOH G64, lies within the Large Magellanic Cloud, one of the small galaxies that orbits the Milky Way. Astronomers have known about this star for decades and have appropriately dubbed it the ‘behemoth star’. With a size roughly 2000 times that of our Sun, WOH G64 is classified as a red supergiant.

Ohnaka’s team had long been interested in this behemoth star. Back in 2005 and 2007, they used ESO’s VLTI in Chile’s Atacama Desert to learn more about the star’s features, and carried on studying it in the years since. But an actual image of the star had remained elusive.

For the desired picture, the team had to wait for the development of one of the VLTI’s second-generation instruments, GRAVITY. After comparing their new results with other previous observations of WOH G64, they were surprised to find that the star had become dimmer over the past decade.

“We have found that the star has been experiencing a significant change in the last 10 years, providing us with a rare opportunity to witness a star’s life in real time,”

says Gerd Weigelt, an astronomy professor at the Max Planck Institute for Radio Astronomy in Bonn, Germany and a co-author of the study. In their final life stages, red supergiants like WOH G64 shed their outer layers of gas and dust in a process that can last thousands of years.

“This star is one of the most extreme of its kind, and any drastic change may bring it closer to an explosive end,”

adds co-author Jacco van Loon, Keele Observatory Director at Keele University, UK, who has been observing WOH G64 since the 1990s.

The team thinks that these shed materials may also be responsible for the dimming and for the unexpected shape of the dust cocoon around the star. The new image shows that the cocoon is stretched-out, which surprised scientists, who expected a different shape based on previous observations and computer models. The team believes that the cocoon’s egg-like shape could be explained by either the star’s shedding or by the influence of a yet-undiscovered companion star.

As the star becomes fainter, taking other close-up pictures of it is becoming increasingly difficult, even for the VLTI. Nonetheless, planned updates to the telescope’s instrumentation, such as the future GRAVITY+, promise to change this soon.

“Similar follow-up observations with ESO instruments will be important for understanding what is going on in the star,”

concludes Ohnaka.

More information

ESO’s Very Large Telescope Interferometer is able to combine light collected by the telescopes of ESO’s Very Large Telescope (VLT), either the four 8-metre Unit Telescopes or the four smaller Auxiliary Telescopes, creating highly detailed pictures of the cosmos. Effectively, this makes the VLTI a “virtual” telescope with a resolution equivalent to the maximum distance between the individual telescopes. This process is highly complex and needs instruments especially dedicated to this task. Back in 2005 and 2007 Ohnaka’s team had access to the first generation of these instruments: MIDI. While impressive for its time, those observations with MIDI only combined the light from two telescopes. Now, researchers have access to GRAVITY, a second-generation instrument able to capture the light of four telescopes. Its improved sensitivity and resolution made the image of WOH G64 possible. But there is more to come. GRAVITY+ is a planned upgrade of GRAVITY which will be able to take advantage of different technological updates performed at the VLTI and VLT. With these, the VLTI will be able to see objects fainter and farther than ever before.

This research was presented in a paper to appear in Astronomy and Astrophysics (https://www.aanda.org/10.1051/0004-6361/202451820).

…

Links

• Research paper
• Photos of the VLT and the VLTI
• For journalists: subscribe to receive our releases under embargo in your language
• For scientists: got a story? Pitch your research

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