Check out the night sky this month, April 2024. Here are videos highlighting the top sights to observe.
** What’s Up: April 2024 Skywatching Tips from NASA – NASA JPL
What are some skywatching highlights in April 2024? Catch Mars and Saturn rising, and Jupiter hangs out with Comet 12P. Plus NASA has you covered for the total eclipse whether you’re headed to totality or watching from afar.
0:00 Intro 0:14 Moon & planet highlights 0:57 Comet 12p/Pons-Brooks 1:38 Total solar eclipse 3:45 April 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….
Clear April nights are filled with starry creatures. Near the Big Dipper, you will find several interesting binary stars. You can also spot galaxies like the Pinwheel Galaxy, M82, and M96—the last of which is an asymmetric galaxy that may have been gravitationally disrupted by encounters with its neighbors. Keep watching for space-based views of these celestial objects.
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.
Pete Lawrence and Paul Abel reveal what’s in the night sky this month, including Comet 12P/Pons Brooks, the Moon and the Pleiades, the April 8 solar eclipse, Lyrid Meteor Shower and the Plough asterism.
00:00 Intro 00:18 Inner planets 02:23 Outer planets 07:31 Comet 12P/Pons-Brooks 10:54 Solar eclipse 12:38 Moon and the Pleiades 13:16 Jewelled Handle 13:48 Lyrid Meteor Shower 14:22 Summer Triangle 15:20 Comet C/2021 S3 PANSTARRS 16:30 The Plough 21:03 Deep-sky objects
This research brings together observations of more than 80 young stars that might have planets forming around them in spectacular discs. This small selection from the survey shows 10 discs from the three regions of our galaxy observed in the papers. V351 Ori and V1012 Ori are located in the most distant of the three regions, the gas-rich cloud of Orion, some 1600 light-years from Earth. DG Tau, T Tau, HP Tau, MWC758 and GM Aur are located in the Taurus region, while HD 97048, WW Cha and SZ Cha can be found in Chamaeleon I, all of which are about 600 light-years from Earth. The images shown here were captured using the Spectro-Polarimetric High-contrast Exoplanet REsearch (SPHERE) instrument mounted on ESO’s Very Large Telescope (VLT). SPHERE’s state-of-the-art extreme adaptive optics system corrects for the turbulent effects of Earth’s atmosphere, yielding crisp images of the discs around stars. The stars themselves have been covered with a coronagraph — a circular mask that blocks their intense glare, revealing the faint discs around them. The discs have been scaled to appear roughly the same size in this composition.
In a series of studies, a team of astronomers has shed new light on the fascinating and complex process of planet formation. The stunning images, captured using the European Southern Observatory’s Very Large Telescope (ESO’s VLT) in Chile, represent one of the largest ever surveys of planet-forming discs. The research brings together observations of more than 80 young stars that might have planets forming around them, providing astronomers with a wealth of data and unique insights into how planets arise in different regions of our galaxy.
“This is really a shift in our field of study,”
says Christian Ginski, a lecturer at the University of Galway, Ireland, and lead author of one of three new papers published today in Astronomy & Astrophysics.
“We’ve gone from the intense study of individual star systems to this huge overview of entire star-forming regions.”
To date more than 5000 planets have been discovered orbiting stars other than the Sun, often within systems markedly different from our own Solar System. To understand where and how this diversity arises, astronomers must observe the dust- and gas-rich discs that envelop young stars — the very cradles of planet formation. These are best found in huge gas clouds where the stars themselves are forming.
Much like mature planetary systems, the new images showcase the extraordinary diversity of planet-forming discs.
“Some of these discs show huge spiral arms, presumably driven by the intricate ballet of orbiting planets,”
says Ginski.
“Others show rings and large cavities carved out by forming planets, while yet others seem smooth and almost dormant among all this bustle of activity,”
adds Antonio Garufi, an astronomer at the Arcetri Astrophysical Observatory, Italian National Institute for Astrophysics (INAF), and lead author of one of the papers.
Planet-forming discs around young stars and their location within the gas-rich cloud of Orion, roughly 1600 light-years from Earth. The mesmerising images of the discs were captured using the Spectro-Polarimetric High-contrast Exoplanet REsearch (SPHERE) instrument mounted on ESO’s Very Large Telescope (VLT). In total, the team observed 23 stars in the Orion region, detecting planet-forming discs around 10 of them. The uneven appearance of some of the discs in this region might suggest that massive planets are embedded within them, since these could cause the discs to warp and become misaligned. The background image shows an infrared view of Orion captured by the Infrared Astronomical Satellite.
The team studied a total of 86 stars across three different star-forming regions of our galaxy: Taurus and Chamaeleon I, both around 600 light-years from Earth, and Orion, a gas-rich cloud about 1600 light-years from us that is known to be the birthplace of several stars more massive than the Sun. The observations were gathered by a large international team, comprising scientists from more than 10 countries.
The team was able to glean several key insights from the dataset. For example, in Orion they found that stars in groups of two or more were less likely to have large planet-forming discs. This is a significant result given that, unlike our Sun, most stars in our galaxy have companions. As well as this, the uneven appearance of the discs in this region suggests the possibility of massive planets embedded within them, which could be causing the discs to warp and become misaligned.
Planet-forming discs around young stars and their location within the gas-rich cloud of Taurus, roughly 600 light-years from Earth. The stunning images of the discs were captured using the Spectro-Polarimetric High-contrast Exoplanet REsearch (SPHERE) instrument mounted on ESO’s Very Large Telescope (VLT). In total, the team observed 43 stars in the Taurus region, all of which are pictured here (though planet-forming discs were only detected in 39 of these targets). The background image shows an infrared view of Taurus captured by the Infrared Astronomical Satellite.
While planet-forming discs can extend for distances hundreds of times greater than the distance between Earth and the Sun, their location several hundreds of light-years from us makes them appear as tiny pinpricks in the night sky. To observe the discs, the team employed the sophisticated Spectro-Polarimetric High-contrast Exoplanet REsearch instrument (SPHERE) mounted on ESO’s VLT. SPHERE’s state-of-the-art extreme adaptive optics system corrects for the turbulent effects of Earth’s atmosphere, yielding crisp images of the discs. This meant the team were able to image discs around stars with masses as low as half the mass of the Sun, which are typically too faint for most other instruments available today. Additional data for the survey were obtained using the VLT’s X-shooter instrument, which allowed astronomers to determine how young and how massive the stars are. The Atacama Large Millimeter/submillimeter Array (ALMA), in which ESO is a partner, on the other hand, helped the team understand more about the amount of dust surrounding some of the stars.
Planet-forming discs around young stars and their location within the gas-rich cloud of Chamaeleon I, roughly 600 light-years from Earth. The stunning images of the discs were captured using the Spectro-Polarimetric High-contrast Exoplanet REsearch (SPHERE) instrument mounted on ESO’s Very Large Telescope (VLT). In total, the team observed 20 stars in the Chamaeleon I region, detecting discs around 13. The background image shows an infrared view of Chamaeleon I captured by the Herschel Space Observatory.
As technology advances, the team hopes to delve even deeper into the heart of planet-forming systems. The large 39-metre mirror of ESO’s forthcoming Extremely Large Telescope (ELT), for example, will enable the team to study the innermost regions around young stars, where rocky planets like our own might be forming.
For now, these spectacular images provide researchers with a treasure trove of data to help unpick the mysteries of planet formation.
“It is almost poetic that the processes that mark the start of the journey towards forming planets and ultimately life in our own Solar System should be so beautiful,”
concludes Per-Gunnar Valegård, a doctoral student at the University of Amsterdam, the Netherlands, who led the Orion study. Valegård, who is also a part-time teacher at the International School Hilversum in the Netherlands, hopes the images will inspire his pupils to become scientists in the future.
This composite image shows the MWC 758 planet-forming disc, located about 500 light-years away in the Taurus region, as seen with two different facilities. The yellow colour represents infrared observations obtained with the Spectro-Polarimetric High-contrast Exoplanet REsearch (SPHERE) instrument on ESO’s Very Large Telescope (VLT). The blue regions on the other hand correspond to observations performed with the Atacama Large Millimeter/submillimeter Array (ALMA), in which ESO is a partner. These facilities allow astronomers to map how dust is distributed around this and other stars in different but complementary ways. SPHERE captures light from the host star that has been scattered by the dust around it, whereas ALMA registers radiation directly emitted by the dust itself. These observations combined help astronomers understand how planets may form in the dusty discs surrounding young stars.
Check out the night sky this month, March 2024. Here are videos highlighting the top sights to observe.
** What’s Up: March 2024 Skywatching Tips from NASA – NASA JPL
What are some skywatching highlights in March 2024? Jupiter plows through the Pleiades on March 14, a chance to spot Mercury at month’s end along with a subtle lunar eclipse, and a comet worth keeping an eye on!
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….
In March, the stars of spring lie eastward: Look for the constellations Gemini and Cancer to spot interesting celestial features like star clusters M35 and the Beehive Cluster, and NGC 3923, an oblong elliptical galaxy with an interesting ripple pattern. Keep watching for space-based views of the galaxies.
Pete Lawrence and Paul Abel reveal what’s in the sky this month, including Jupiter, the Moon, Comet C/2021 S3 PANSTARRS and a tour through Coma Berenices and the Bowl of Virgo.
00:00 Intro 00:15 Inner planets 03:56 Jupiter and Saturn 04:40 Uranus and Neptune 05:50 Juno 05:58 The Moon 11:40 Comet C/2021 S3 PANSTARRS 12:05 Constellations 16:00 Leo Triplet 17:50 Coma Berenices 21:05 Bowl of Virgo
** Sky & Telescope’s Sky Tour Podcast – March 2024 | Sirius and the Moon Phases – Sky & Telescope Youtube
Astronomers have found water vapour in a disc around a young star exactly where planets may be forming. In this image, the new observations from the Atacama Large Millimeter/submillimeter Array (ALMA), in which ESO is a partner, show the water vapour in shades of blue. Near the centre of the disc, where the young star lives, the environment is hotter and the gas brighter. The red-hued rings are previous ALMA observations showing the distribution of dust around the star.
Researchers have found water vapour in the disc around a young star exactly where planets may be forming. Water is a key ingredient for life on Earth, and is also thought to play a significant role in planet formation. Yet, until now, we had never been able to map how water is distributed in a stable, cool disc — the type of disc that offers the most favourable conditions for planets to form around stars. The new findings were made possible thanks to the Atacama Large Millimeter/submillimeter Array (ALMA), in which the European Southern Observatory (ESO) is a partner.
“I had never imagined that we could capture an image of oceans of water vapour in the same region where a planet is likely forming,”
says Stefano Facchini, an astronomer at the University of Milan, Italy, who led the study published today in Nature Astronomy. The observations reveal at least three times as much water as in all of Earth’s oceans in the inner disc of the young Sun-like star HL Tauri, located 450 light-years away from Earth in the constellation Taurus.
“It is truly remarkable that we can not only detect but also capture detailed images and spatially resolve water vapour at a distance of 450 light-years from us ,”
adds co-author Leonardo Testi, an astronomer at the University of Bologna, Italy. The ‘spatially resolved’ observations with ALMA allow astronomers to determine the distribution of water in different regions of the disc.
“Taking part in such an important discovery in the iconic HL Tauri disc was beyond what I had ever expected for my first research experience in astronomy,”
adds Mathieu Vander Donckt from the University of Liège, Belgium, who was a master’s student when he participated in the research.
A significant amount of water was found in the region where a known gap in the HL Tauri disc exists. Ring-shaped gaps are carved out in gas- and dust-rich discs by orbiting young planet-like bodies as they gather up material and grow.
Our recent images reveal a substantial quantity of water vapour at a range of distances from the star that include a gap where a planet could potentially be forming at the present time,”
says Facchini. This suggests that this water vapour could affect the chemical composition of planets forming in those regions.
This is the sharpest image ever taken by ALMA — sharper than is routinely achieved in visible light with the NASA/ESA Hubble Space Telescope. It shows the protoplanetary disc surrounding the young star HL Tauri. These new ALMA observations reveal substructures within the disc that have never been seen before and even show the possible positions of planets forming in the dark patches within the system.
Observing water with a ground-based telescope is no mean feat as the abundant water vapour in Earth’s atmosphere degrades the astronomical signals. ALMA, operated by ESO together with its international partners, is an array of telescopes in the Chilean Atacama Desert at about 5000 metres elevation that was built in a high and dry environment specifically to minimise this degradation, providing exceptional observing conditions.
“To date, ALMA is the only facility able to spatially resolve water in a cool planet-forming disc,”
says co-author Wouter Vlemmings, a professor at the Chalmers University of Technology in Sweden [1].
“It is truly exciting to directly witness, in a picture, water molecules being released from icy dust particles,”
says Elizabeth Humphreys, an astronomer at ESO who also participated in the study. The dust grains that make up a disc are the seeds of planet formation, colliding and clumping into ever larger bodies orbiting the star. Astronomers believe that where it is cold enough for water to freeze onto dust particles, things stick together more efficiently — an ideal spot for planet formation.
“Our results show how the presence of water may influence the development of a planetary system, just like it did some 4.5 billion years ago in our own Solar System,”
Facchini adds.
With upgrades happening at ALMA and ESO’s Extremely Large Telescope (ELT) coming online within the decade, planet formation and the role water plays in it will become clearer than ever. In particular METIS, the Mid-infrared ELT Imager and Spectrograph, will give astronomers unrivalled views of the inner regions of planet-forming discs, where planets like Earth form.
Notes
[1] The new observations used the Band 5 and Band 7 receivers on ALMA. Bands 5 and 7 were European developments, at Chalmers/NOVA (Netherlands Research School for Astronomy) and IRAM (Institut de radioastronomie millimétrique), respectively, with involvement of ESO. Band 5 expanded ALMA into a new frequency range specifically for detecting and imaging water in the local Universe. In this study, the team observed three spectral lines of water across the two receiver frequency ranges to map gas at different temperatures within the disc.
This artist’s impression shows the magnetic white dwarf WD 0816-310, where astronomers have found a scar imprinted on its surface as a result of having ingested planetary debris. When objects like planets or asteroids approach the white dwarf they get disrupted, forming a debris disc around the dead star. Some of this material can be devoured by the dwarf, leaving traces of certain chemical elements on its surface. Using ESO’s Very Large Telescope, astronomers found that the signature of these chemical elements changed periodically as the star rotated, as did the magnetic field. This indicates that the magnetic fields funneled these elements onto the star, concentrating them at the magnetic poles and forming the scar seen here.
When a star like our Sun reaches the end of its life, it can ingest the surrounding planets and asteroids that were born with it. Now, using the European Southern Observatory’s Very Large Telescope (ESO’s VLT) in Chile, researchers have found a unique signature of this process for the first time — a scar imprinted on the surface of a white dwarf star. The results are published today in The Astrophysical Journal Letters.
“It is well known that some white dwarfs — slowly cooling embers of stars like our Sun — are cannibalising pieces of their planetary systems. Now we have discovered that the star’s magnetic field plays a key role in this process, resulting in a scar on the white dwarf’s surface,”
says Stefano Bagnulo, an astronomer at Armagh Observatory and Planetarium in Northern Ireland, UK, and lead author of the study.
The scar the team observed is a concentration of metals imprinted on the surface of the white dwarf WD 0816-310, the Earth-sized remnant of a star similar to, but somewhat larger than, our Sun.
“We have demonstrated that these metals originate from a planetary fragment as large as or possibly larger than Vesta, which is about 500 kilometres across and the second-largest asteroid in the Solar System,”
says Jay Farihi, a professor at University College London, UK, and co-author on the study.
The observations also provided clues to how the star got its metal scar. The team noticed that the strength of the metal detection changed as the star rotated, suggesting that the metals are concentrated on a specific area on the white dwarf’s surface, rather than smoothly spread across it. They also found that these changes were synchronised with changes in the white dwarf’s magnetic field, indicating that this metal scar is located on one of its magnetic poles. Put together, these clues indicate that the magnetic field funneled metals onto the star, creating the scar [1].
“Surprisingly, the material was not evenly mixed over the surface of the star, as predicted by theory. Instead, this scar is a concentrated patch of planetary material, held in place by the same magnetic field that has guided the infalling fragments,”
says co-author John Landstreet, a professor at Western University, Canada, who is also affiliated with the Armagh Observatory and Planetarium.
“Nothing like this has been seen before.”
To reach these conclusions, the team used a ‘Swiss-army knife’ instrument on the VLT called FORS2, which allowed them to detect the metal scar and connect it to the star’s magnetic field.
“ESO has the unique combination of capabilities needed to observe faint objects such as white dwarfs, and sensitively measure stellar magnetic fields,”
says Bagnulo. In their study, the team also relied on archival data from the VLT’s X-shooter instrument to confirm their findings.
Harnessing the power of observations like these, astronomers can reveal the bulk composition of exoplanets, planets orbiting other stars outside the Solar System. This unique study also shows how planetary systems can remain dynamically active, even after ‘death’.
Notes
[1] Previously, astronomers have observed numerous white dwarfs polluted by metals that were scattered over the surface of the star. These are known to originate from disrupted planets or asteroids that veer too close to the star, following star-grazing orbits similar to those of comets in our Solar System. However, for WD 0816-310, the team is confident that vaporised material was ionised and guided onto the magnetic poles by the white dwarf’s magnetic field. The process shares similarities to how auroras form on Earth and on Jupiter.
