** What’s Up: August 2021 Skywatching Tips from NASA – NASA JPL
What are some skywatching highlights in August 2021? The best-known meteor shower of the year should be a good time this year on the peak night of Aug. 11, with no bright Moon to interfere. Jupiter and Saturn are at their best all month long. And on Aug. 22, the full moon will be a “seasonal blue moon.” 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/whats-up….
In August, a flock of star-studded figures soars overhead. Look for the Vega and Lyra constellations, which point to Epsilon Lyrae and the Ring Nebula. You can also spot three bright summer stars: Vega, Deneb, and Altair, which form the Summer Triangle. Keep watching for space-based views of these and other stars and nebulas.
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 [Tonight’s Sky].
This image, taken with the Atacama Large Millimeter/submillimeter Array (ALMA), in which ESO is a partner, shows wide (left) and close-up (right) views of the moon-forming disc surrounding PDS 70c, a young Jupiter-like planet nearly 400 light-years away. The close-up view shows PDS 70c and its circumplanetary disc centre-front, with the larger circumstellar ring-like disc taking up most of the right-hand side of the image. The star PDS 70 is at the centre of the wide-view image on the left. Two planets have been found in the system, PDS 70c and PDS 70b, the latter not being visible in this image. They have carved a cavity in the circumstellar disc as they gobbled up material from the disc itself, growing in size. In this process, PDS 70c acquired its own circumplanetary disc, which contributes to the growth of the planet and where moons can form. This circumplanetary disc is as large as the Sun-Earth distance and has enough mass to form up to three satellites the size of the Moon.
Using the Atacama Large Millimetre/submillimeter Array (ALMA), in which the European Southern Observatory (ESO) is a partner, astronomers have unambiguously detected the presence of a disc around a planet outside our Solar System for the first time. The observations will shed new light on how moons and planets form in young stellar systems.
“Our work presents a clear detection of a disc in which satellites could be forming,”
says Myriam Benisty, a researcher at the University of Grenoble, France, and at the University of Chile, who led the new research published today in The Astrophysical Journal Letters.
“Our ALMA observations were obtained at such exquisite resolution that we could clearly identify that the disc is associated with the planet and we are able to constrain its size for the first time,”
she adds.
The disc in question, called a circumplanetary disc, surrounds the exoplanet PDS 70c, one of two giant, Jupiter-like planets orbiting a star nearly 400 light-years away. Astronomers had found hints of a “moon-forming” disc around this exoplanet before but, since they could not clearly tell the disc apart from its surrounding environment, they could not confirm its detection — until now.
In addition, with the help of ALMA, Benisty and her team found that the disc has about the same diameter as the distance from our Sun to the Earth and enough mass to form up to three satellites the size of the Moon.
But the results are not only key to finding out how moons arise.
“These new observations are also extremely important to prove theories of planet formation that could not be tested until now,”
says Jaehan Bae, a researcher from the Earth and Planets Laboratory of the Carnegie Institution for Science, USA, and author on the study.
Planets form in dusty discs around young stars, carving out cavities as they gobble up material from this circumstellar disc to grow. In this process, a planet can acquire its own circumplanetary disc, which contributes to the growth of the planet by regulating the amount of material falling onto it. At the same time, the gas and dust in the circumplanetary disc can come together into progressively larger bodies through multiple collisions, ultimately leading to the birth of moons.
This image, taken with the Atacama Large Millimeter/submillimeter Array (ALMA), in which ESO is a partner, shows a close-up view on the moon-forming disc surrounding PDS 70c, a young Jupiter-like gas giant nearly 400 light-years away. It shows this planet and its disc centre-front, with the larger circumstellar ring-like disc taking up most of the right-hand side of the image. The dusty circumplanetary disc is as large as the Sun-Earth distance and has enough mass to form up to three satellites the size of the Moon.
But astronomers do not yet fully understand the details of these processes.
“In short, it is still unclear when, where, and how planets and moons form,”
explains ESO Research Fellow Stefano Facchini, also involved in the research.
“More than 4000 exoplanets have been found until now, but all of them were detected in mature systems. PDS 70b and PDS 70c, which form a system reminiscent of the Jupiter-Saturn pair, are the only two exoplanets detected so far that are still in the process of being formed,”
explains Miriam Keppler, researcher at the Max Planck Institute for Astronomy in Germany and one of the co-authors of the study [1].
“This system therefore offers us a unique opportunity to observe and study the processes of planet and satellite formation,”
Facchini adds.
PDS 70b and PDS 70c, the two planets making up the system, were first discovered using ESO’s Very Large Telescope (VLT) in 2018 and 2019 respectively, and their unique nature means they have been observed with other telescopes and instruments many times since [2].
The latest high resolution ALMA observations have now allowed astronomers to gain further insights into the system. In addition to confirming the detection of the circumplanetary disc around PDS 70c and studying its size and mass, they found that PDS 70b does not show clear evidence of such a disc, indicating that it was starved of dust material from its birth environment by PDS 70c.
An even deeper understanding of the planetary system will be achieved with ESO’s Extremely Large Telescope (ELT), currently under construction on Cerro Armazones in the Chilean Atacama desert.
“The ELT will be key for this research since, with its much higher resolution, we will be able to map the system in great detail,”
says co-author Richard Teague, a researcher at the Center for Astrophysics | Harvard & Smithsonian, USA. In particular, by using the ELT’s Mid-infrared ELT Imager and Spectrograph (METIS), the team will be able to look at the gas motions surrounding PDS 70c to get a full 3D picture of the system.
Notes
[1] Despite the similarity with the Jupiter-Saturn pair, note that the disc around PDS 70c is about 500 times larger than Saturn’s rings.
[2] PDS 70b was discovered using the Spectro-Polarimetric High-contrast Exoplanet REsearch (SPHERE) instrument, while PDS 70c was found using the VLT’s Multi Unit Spectroscopic Explorer (MUSE). The two-planet system has been investigated using the X-shooter instrument too, also installed on ESO’s VLT.
This image combines observations of the nearby galaxies NGC 1300, NGC 1087, NGC 3627 (top, from left to right), NGC 4254 and NGC 4303 (bottom, from left to right) taken with the Multi-Unit Spectroscopic Explorer (MUSE) on ESO’s Very Large Telescope (VLT). Each individual image is a combination of observations conducted at different wavelengths of light to map stellar populations and warm gas. The golden glows mainly correspond to clouds of ionised hydrogen, oxygen and sulphur gas, marking the presence of newly born stars, while the bluish regions in the background reveal the distribution of slightly older stars. The images were taken as part of the Physics at High Angular resolution in Nearby GalaxieS (PHANGS) project, which is making high-resolution observations of nearby galaxies with telescopes operating across the electromagnetic spectrum.
A team of astronomers has released new observations of nearby galaxies that resemble colourful cosmic fireworks. The images, obtained with the European Southern Observatory’s Very Large Telescope (ESO’s VLT), show different components of the galaxies in distinct colours, allowing astronomers to pinpoint the locations of young stars and the gas they warm up around them. By combining these new observations with data from the Atacama Large Millimeter/submillimeter Array (ALMA), in which ESO is a partner, the team is helping shed new light on what triggers gas to form stars.
This image of the nearby galaxy NGC 1300 was obtained by combining observations taken with the Multi-Unit Spectroscopic Explorer (MUSE) on ESO’s Very Large Telescope (VLT) and with the Atacama Large Millimeter/submillimeter Array (ALMA), in which ESO is a partner. NGC 1300 is a spiral galaxy, with a bar of stars and gas at its centre, located approximately 61 million light-years from Earth in the constellation Eridanus. The image is a combination of observations conducted at different wavelengths of light to map stellar populations and gas. ALMA’s observations are represented in brownish-orange tones and highlight the clouds of cold molecular gas that provide the raw material from which stars form. The MUSE data show up mainly in gold and blue. The bright golden glows map warm clouds of mainly ionised hydrogen, oxygen and sulphur gas, marking the presence of newly born stars, while the bluish regions reveal the distribution of slightly older stars. The image was taken as part of the Physics at High Angular resolution in Nearby GalaxieS (PHANGS) project, which is making high resolution observations of nearby galaxies with telescopes operating across the electromagnetic spectrum.
Astronomers know that stars are born in clouds of gas, but what sets off star formation, and how galaxies as a whole play into it, remains a mystery. To understand this process, a team of researchers has observed various nearby galaxies with powerful telescopes on the ground and in space, scanning the different galactic regions involved in stellar births.
“For the first time we are resolving individual units of star formation over a wide range of locations and environments in a sample that well represents the different types of galaxies,”
says Eric Emsellem, an astronomer at ESO in Germany and lead of the VLT-based observations conducted as part of the Physics at High Angular resolution in Nearby GalaxieS (PHANGS) project.
“We can directly observe the gas that gives birth to stars, we see the young stars themselves, and we witness their evolution through various phases.”
Emsellem, who is also affiliated with the University of Lyon, France, and his team have now released their latest set of galactic scans, taken with the Multi-Unit Spectroscopic Explorer (MUSE) instrument on ESO’s VLT in the Atacama Desert in Chile. They used MUSE to trace newborn stars and the warm gas around them, which is illuminated and heated up by the stars and acts as a smoking gun of ongoing star formation.
The new MUSE images are now being combined with observations of the same galaxies taken with ALMA and released earlier this year. ALMA, which is also located in Chile, is especially well suited to mapping cold gas clouds — the parts of galaxies that provide the raw material out of which stars form.
By combining MUSE and ALMA images astronomers can examine the galactic regions where star formation is happening, compared to where it is expected to happen, so as to better understand what triggers, boosts or holds back the birth of new stars. The resulting images are stunning, offering a spectacularly colourful insight into stellar nurseries in our neighbouring galaxies.
“There are many mysteries we want to unravel,”
says Kathryn Kreckel from the University of Heidelberg in Germany and PHANGS team member.
“Are stars more often born in specific regions of their host galaxies — and, if so, why? And after stars are born how does their evolution influence the formation of new generations of stars?”
Astronomers will now be able to answer these questions thanks to the wealth of MUSE and ALMA data the PHANGS team have obtained. MUSE collects spectra — the “bar codes” astronomers scan to unveil the properties and nature of cosmic objects — at every single location within its field of view, thus providing much richer information than traditional instruments. For the PHANGS project, MUSE observed 30 000 nebulae of warm gas and collected about 15 million spectra of different galactic regions. The ALMA observations, on the other hand, allowed astronomers to map around 100 000 cold-gas regions across 90 nearby galaxies, producing an unprecedentedly sharp atlas of stellar nurseries in the close Universe.
This image of the nearby galaxy NGC 4303 was obtained by combining observations taken with the Multi-Unit Spectroscopic Explorer (MUSE) on ESO’s Very Large Telescope (VLT) and with the Atacama Large Millimeter/submillimeter Array (ALMA), in which ESO is a partner. NGC 4303 is a spiral galaxy, with a bar of stars and gas at its centre, located approximately 55 million light-years from Earth in the constellation Virgo. The image is a combination of observations conducted at different wavelengths of light to map stellar populations and gas. ALMA’s observations are represented in brownish-orange tones and highlight the clouds of cold molecular gas that provide the raw material from which stars form. The MUSE data show up mainly in gold and blue. The bright golden glows map warm clouds of mainly ionised hydrogen, oxygen and sulphur gas, marking the presence of newly born stars, while the bluish regions reveal the distribution of slightly older stars. The image was taken as part of the Physics at High Angular resolution in Nearby GalaxieS (PHANGS) project, which is making high-resolution observations of nearby galaxies with telescopes operating across the electromagnetic spectrum.
In addition to ALMA and MUSE, the PHANGS project also features observations from the NASA/ESA Hubble Space Telescope. The various observatories were selected to allow the team to scan our galactic neighbours at different wavelengths (visible, near-infrared and radio), with each wavelength range unveiling distinct parts of the observed galaxies.
“Their combination allows us to probe the various stages of stellar birth — from the formation of the stellar nurseries to the onset of star formation itself and the final destruction of the nurseries by the newly born stars — in more detail than is possible with individual observations,”
says PHANGS team member Francesco Belfiore from INAF-Arcetri in Florence, Italy.
“PHANGS is the first time we have been able to assemble such a complete view, taking images sharp enough to see the individual clouds, stars, and nebulae that signify forming stars.”
The work carried out by the PHANGS project will be further honed by upcoming telescopes and instruments, such as NASA’s James Webb Space Telescope. The data obtained in this way will lay further groundwork for observations with ESO’s future Extremely Large Telescope (ELT), which will start operating later this decade and will enable an even more detailed look at the structures of stellar nurseries.
“As amazing as PHANGS is, the resolution of the maps that we produce is just sufficient to identify and separate individual star-forming clouds, but not good enough to see what’s happening inside them in detail,”
pointed out Eva Schinnerer, a research group leader at the Max Planck Institute for Astronomy in Germany and principal investigator of the PHANGS project, under which the new observations were conducted.
“New observational efforts by our team and others are pushing the boundary in this direction, so we have decades of exciting discoveries ahead of us.”
[ See also these interactive comparisons of galaxy images with and without the ALMA radio array data:
** What’s Up: July 2021 Skywatching Tips from NASA – NASA JPL
What are some skywatching highlights in July 2021? Venus blazes as the “Evening Star” following the sunset, with a much fainter planet Mars nearby. Catch their super close pairing on July 12. Plus, if you can find your way to dark skies, this is the best time of year to enjoy the magic of the Milky Way.
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/whats-up….
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.
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-galle….
What can you see in the night sky tonight? Astronomers Pete Lawrence and Paul Abel talk us through July’s night-sky highlights.
** What’s in the Night Sky July 2021 #WITNS – Alyn Wallace
In the night sky this month we have a noctilucent clouds, spot the Chinese Space Station Tiangong (Tianhe-1), an awesome conjunction between Mars and Venus and of course the Milky Way.
This month’s Sky Tour astronomy podcast tells you “what’s up” in the evening sky. No experience or equipment is necessary — just download or stream the audio file and take it with you outside. With the last-quarter Moon on July 1st and new Moon on the 9th, your darkest evenings for stargazing are during the first half of the month.
Two of the Sun’s inner planets are doing a little dance over in the west after sunset this month. Look just to the upper left of the sunset point for Venus. This planet is quite bright, but its dazzle is diminished somewhat due to the twilight around it. In early July, a second and much dimmer planet is lurking just to the upper left of Venus. That’s Mars, just 1% as bright as Venus.
[ Update: What’s Up: June 2021 Skywatching Tips from NASA – NASA JPL
What are some skywatching highlights in June 2021? Catch Saturn and Jupiter in the morning, and the constellation Scorpius after dark! Plus skywatchers in the Northeast U.S., Eastern Canada, and Northern Europe can see a partial solar eclipse on June 10th. 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/whats-up….
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 can you see in the night sky tonight? Astronomers Pete Lawrence and Paul Abel guide us through June’s astronomy highlights, including the partial solar eclipse visible on 10 June
** What’s in the Night Sky June 2021 #WITNS – Alyn Wallace
This month we have an annular solar eclipse, noctilucent clouds and Mars passes through the Beehive Cluster.
