Archives For astronomy

Observations made with the European Southern Observatory’s Very Large Telescope (ESO’s VLT) have revealed the telltale signs of a star system being born. Credit: ESO/Boccaletti et al.

Observations made with the European Southern Observatory’s Very Large Telescope (ESO’s VLT) have revealed the telltale signs of a star system being born. Credit: ESO/Boccaletti et al.

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May 20 — “Thousands of exoplanets have been identified so far, but little is known about how they form,” says Anthony Boccaletti who led the study from the Observatoire de Paris, PSL University, France. Astronomers know planets are born in dusty discs surrounding young stars, like AB Aurigae, as cold gas and dust clump together. The new observations with ESO’s VLT, published in Astronomy & Astrophysics, provide crucial clues to help scientists better understand this process.
“We need to observe very young systems to really capture the moment when planets form,” says Boccaletti. But until now astronomers had been unable to take sufficiently sharp and deep images of these young discs to find the ‘twist’ that marks the spot where a baby planet may be coming to existence.

The new images feature a stunning spiral of dust and gas around AB Aurigae, located 520 light-years away from Earth in the constellation of Auriga (The Charioteer). Spirals of this type signal the presence of baby planets, which ‘kick’ the gas, creating “disturbances in the disc in the form of a wave, somewhat like the wake of a boat on a lake,” explains Emmanuel Di Folco of the Astrophysics Laboratory of Bordeaux (LAB), France, who also participated in the study. As the planet rotates around the central star, this wave gets shaped into a spiral arm. The very bright yellow ‘twist’ region close to the center of the new AB Aurigae image, which lies at about the same distance from the star as Neptune from the Sun, is one of these disturbance sites where the team believe a planet is being made.

 

The images of the AB Aurigae system showing the disc around it. The image on the right is a zoomed-in version of the area indicated by a red square on the image on the left. It shows the inner region of the disc, including the very-bright-yellow ‘twist’ (circled in white) that scientists believe marks the spot where a planet is forming. This twist lies at about the same distance from the AB Aurigae star as Neptune from the Sun. The blue circle represents the size of the orbit of Neptune. The images were obtained with the SPHERE instrument on ESO’s Very Large Telescope in polarized light. Credit: ESO/Boccaletti et al.

The images of the AB Aurigae system showing the disc around it. The image on the right is a zoomed-in version of the area indicated by a red square on the image on the left. It shows the inner region of the disc, including the very-bright-yellow ‘twist’ (circled in white) that scientists believe marks the spot where a planet is forming. This twist lies at about the same distance from the AB Aurigae star as Neptune from the Sun. The blue circle represents the size of the orbit of Neptune. The images were obtained with the SPHERE instrument on ESO’s Very Large Telescope in polarized light. Credit: ESO/Boccaletti et al.

 

Observations of the AB Aurigae system made a few years ago with the Atacama Large Millimeter/submillimeter Array (ALMA), in which ESO is a partner, provided the first hints of ongoing planet formation around the star. In the ALMA images, scientists spotted two spiral arms of gas close to the star, lying within the disc’s inner region. Then, in 2019 and early 2020, Boccaletti and a team of astronomers from France, Taiwan, the US and Belgium set out to capture a clearer picture by turning the SPHERE instrument on ESO’s VLT in Chile toward the star. The SPHERE images are the deepest images of the AB Aurigae system obtained to date.

With SPHERE’s powerful imaging system, astronomers could see the fainter light from small dust grains and emissions coming from the inner disc. They confirmed the presence of the spiral arms first detected by ALMA and also spotted another remarkable feature, a ‘twist’, that points to the presence of ongoing planet formation in the disc. “The twist is expected from some theoretical models of planet formation,” says co-author Anne Dutrey, also at LAB. “It corresponds to the connection of two spirals  — one winding inwards of the planet’s orbit, the other expanding outwards — which join at the planet location. They allow gas and dust from the disc to accrete onto the forming planet and make it grow.”

ESO is constructing the 39-meter Extremely Large Telescope, which will draw on the cutting-edge work of ALMA and SPHERE to study extrasolar worlds. As Boccaletti explains, this powerful telescope will allow astronomers to get even more detailed views of planets in the making. “We should be able to see directly and more precisely how the dynamics of the gas contributes to the formation of planets,” he concludes.

Photo: Comet 17P/Holmes by James Guilford

Comet Redux. Reprocessing old images shot through the Stephens Observatory telescope shows Comet 17P/Holmes as it appeared October 28, 2007. The two dots are bright stars shining through the comet’s coma. Photo by James Guilford.

Back in 2007 astronomers were excited by a comet known as 17P/Holmes. What was so exciting was that the seemingly ordinary visitor from distant parts of the Solar System suddenly put on a great show. In October, the usually dim 17P/Holmes changed from an unremarkable telescopic object to become visible to the unaided eye, appearing as a yellow “star” in constellation Perseus. It was briefly the largest object in the Solar System. The outburst was believed to be similar to one that took place in 1892 making it visible to amateur astronomer Edwin Holmes, credited with its discovery on November 6 of that year. The reason for the sudden brightening or outbursts remains unknown.

I used my little Canon Rebel XT digital camera attached to the vintage Cooley Telescope at Stephens and attempted to capture images of the comet. The effort and the camera were pretty primitive compared with what we can do now but I got some images and they were the best I could manage at the time. Comet 17P/Holmes faded from visibility over the next several weeks. The somewhat odd appearance of the comet — no classic head and tail — is the result of our perspective: looking straight down its tail instead of from the side.

Recently I viewed a television show about comets and the strange behavior of 17P/Holmes was discussed. That program reminded me of the 2007 apparition and to look at my old images. There wasn’t much image data to work with but I reprocessed what I have and produced a new image a bit better than my first try; that image, shot through our old telescope, appears above.

The “P” in the comet’s designation stands for periodic, meaning after a period of time 17P will return to loop, once again, around Sun. In March 2014 (a seven-year period) the loop was made without an outburst. The next close approach to our Sun, perihelion, will take place on February 19, 2021. Will we be treated to another show?

— James Guilford

This image is one of the most photogenic examples of the many turbulent stellar nurseries the NASA/ESA Hubble Space Telescope has observed during its 30-year lifetime. The portrait features the giant nebula NGC 2014 and its neighbor NGC 2020 which together form part of a vast star-forming region in the Large Magellanic Cloud, a satellite galaxy of the Milky Way, approximately 163,000 light-years away.

Photo: Asteroid/dwarf planet Hygiea. Credit: ESO/P. Vernazza et al./MISTRAL algorithm (ONERA/CNRS)

A new SPHERE/VLT image of Hygiea, which could be the Solar System’s smallest dwarf planet yet. As an object in the main asteroid belt, Hygiea satisfies right away three of the four requirements to be classified as a dwarf planet: it orbits around the Sun, it is not a moon and, unlike a planet, it has not cleared the neighborhood around its orbit. The final requirement is that it have enough mass that its own gravity pulls it into a roughly spherical shape. This is what VLT observations have now revealed about Hygiea. Credit: ESO/P. Vernazza et al./MISTRAL algorithm (ONERA/CNRS)

Astronomers using ESO’s SPHERE instrument at the Very Large Telescope (VLT) have revealed that the asteroid Hygiea could be classified as a dwarf planet. The object is the fourth largest in the asteroid belt after Ceres, Vesta and Pallas. For the first time, astronomers have observed Hygiea in sufficiently high resolution to study its surface and determine its shape and size. They found that Hygiea is spherical, potentially taking the crown from Ceres as the smallest dwarf planet in the Solar System.

As an object in the main asteroid belt, Hygiea satisfies right away three of the four requirements to be classified as a dwarf planet: it orbits around the Sun, it is not a moon and, unlike a planet, it has not cleared the neighborhood around its orbit. The final requirement is that it has enough mass for its own gravity to pull it into a roughly spherical shape. This is what VLT observations have now revealed about Hygiea.

“Thanks to the unique capability of the SPHERE instrument on the VLT, which is one of the most powerful imaging systems in the world, we could resolve Hygiea’s shape, which turns out to be nearly spherical,” says lead researcher Pierre Vernazza from the Laboratoire d’Astrophysique de Marseille in France. “Thanks to these images, Hygiea may be reclassified as a dwarf planet, so far the smallest in the Solar System.”

The team also used the SPHERE observations to constrain Hygiea’s size, putting its diameter at just over 430 km. Pluto, the most famous of dwarf planets, has a diameter close to 2,400 km, while Ceres is close to 950 km in size.

Surprisingly, the observations also revealed that Hygiea lacks the very large impact crater that scientists expected to see on its surface, the team report in the study published today in Nature Astronomy. Hygiea is the main member of one of the largest asteroid families, with close to 7,000 members that all originated from the same parent body. Astronomers expected the event that led to the formation of this numerous family to have left a large, deep mark on Hygiea.

“This result came as a real surprise as we were expecting the presence of a large impact basin, as is the case on Vesta,” says Vernazza. Although the astronomers observed Hygiea’s surface with a 95 percent coverage, they could only identify two unambiguous craters. “Neither of these two craters could have been caused by the impact that originated the Hygiea family of asteroids whose volume is comparable to that of a 100 km-sized object. They are too small,” explains study co-author Miroslav Brož of the Astronomical Institute of Charles University in Prague, Czech Republic.

The team decided to investigate further. Using numerical simulations, they deduced that Hygiea’s spherical shape and large family of asteroids are likely the result of a major head-on collision with a large projectile of diameter between 75 and 150 km. Their simulations show this violent impact, thought to have occurred about 2 billion years ago, completely shattered the parent body. Once the left-over pieces reassembled, they gave Hygiea its round shape and thousands of companion asteroids. “Such a collision between two large bodies in the asteroid belt is unique in the last 3–4 billion years,” says Pavel Ševeček, a PhD student at the Astronomical Institute of Charles University who also participated in the study.

Studying asteroids in detail has been possible thanks not only to advances in numerical computation, but also to more powerful telescopes. “Thanks to the VLT and the new generation adaptive-optics instrument SPHERE, we are now imaging main belt asteroids with unprecedented resolution, closing the gap between Earth-based and interplanetary mission observations,” Vernazza concludes.

Photo: First Quarter Moon, October 5, 2019.

Our First-Quarter Moon on International Observe the Moon Night, as seen through the Stephens telescope at 9:04 PM EDT. iPhone SE at eyepiece.

 

Our October 5 Open Night was the local event of the International Observe the Moon Night — an annual occurrence meant that encourages observation, appreciation, and understanding of our Moon and its connection to planetary science and exploration. Over the course of the night at Stephens Memorial Observatory some 34 enthusiastic and inquisitive visitors attended and were treated to beautiful and unusual views of Earth’s Moon and planet Saturn.

Unusual? The earliest visitors arrived just as the telescope was set to go … with the sky still bright with twilight. The Moon appeared light and against a power-blue sky background instead of the usual darkness of space. Saturn, invisible to the eye in the bright sky, was also viewed through the telescope in surprising detail.

 

Zooming in on the previous image: That dot in the center of dark-floored crater Alphonsus is its central peak. Over the course of two hours sun rose over that pinnacle making it brighter, and other features began to emerge as we watched. Alphonsus slightly overlaps the crater Ptolemaeus.

After darkness fell enthusiastic visitors took turns looking at a crater and watching a mountain peak become illuminated at sunrise on the Moon! It was a fine night appreciating a sight too often ignored: the wonder of Luna, our nearest neighbor in space.

Photo: August 21, 2017 total solar eclipse. Credits: NASA/Gopalswamy

The corona, a region of the Sun only seen from Earth when the Moon blocks out the Sun’s bright face during total solar eclipses. The corona holds the answers to many of scientists’ outstanding questions about the Sun’s activity and processes. This photo was taken during the total solar eclipse on Aug. 21, 2017. Credits: NASA/Gopalswamy

Be sure to be watching July 2 at 4:00 PM EDT as the total solar eclipse is presented live from Chile, via San Francisco’s Exploratorium. You will not be able to directly see the eclipse from the USA; the total solar eclipse will be visible from a narrow part of the South Pacific Ocean, Chile, and Argentina.

The Exploratorium will be bringing the total solar eclipse to you, no matter where you are. The have sent a team to Chile to broadcast from within the path of totality. Enjoy this full, unnarrated view of the eclipse from the telescopes at the National Science Foundation’s Cerro Tololo Observatory.

Live Telescope View – Not Narrated:
https://www.exploratorium.edu/video/total-solar-eclipse-live-july-2-2019

Live Coverage – Broadcast Style:
https://www.exploratorium.edu/video/total-solar-eclipse-2019-live-coverage

NASA has partnered with the Exploratorium to provide the coverage which it will livestream: three views via separate players on the agency’s website (all times EDT):

  • Live views from telescopes in Vicuna, Chile, without audio, from 3 to 6 PM
  • A one-hour program with live commentary in English, from 4 to 5 PM
  • A one-hour program with live commentary in Spanish, from 4 to 5 PM

NASA Television will also carry the English-language program on its public channel. Both programs will feature updates from NASA’s Parker Solar Probe and Magnetospheric Multiscale missions.

Jupiter and its Galilean Moons as they will appear the night of July 13, 2019. Labels for Ganymede and Io overlap. Simulation via "Gas Giants".

Jupiter and its Galilean Moons as they will appear the night of July 13, 2019. Labels for Ganymede and Io overlap. Simulation via “Gas Giants”.

 

WRAP-UP: We played peek-a-boo through clouds with Moon and Jupiter all evening. When they first became visible from behind neighboring trees, viewing of our Moon and the planet was fair to poor. As time passed and the atmosphere settled down, seeing became better and late visitors were treated to excellent views of Moon and fair to good views of Jupiter with his four Galilean Moons and even the Great Red Spot (GRS). In fact, just before we closed for the night, the GRS showed not just as a thickening in the Southern Equatorial Band but as a definite shape with red coloration! Saturday’s was not the best view we’ve had of Jupiter but in the end, it was pretty good. Thanks to the 34 visitors who came out on a muggy and buggy night to enjoy the sights!

Stephens Memorial Observatory of Hiram College will host a Public Night Saturday, July 13, from 9:30 to 11:00 PM. On the observing list are two Stephens favorites: Earth’s Moon, and planet Jupiter with its moons. Other objects of interest may also be viewed using the Observatory’s 1901 vintage telescope. Given good viewing conditions, organizers say, the telescope delivers outstanding detail of the Moon and impressive views of Jupiter including, when it’s in position as it will be July 13, the planet’s Great Red Spot feature.

Organizers hope for clear skies since recent weather conditions have made scheduled observing impossible. Cloudy skies at the scheduled starting time cancel the event in which case, the observatory will not open. No reservations are required and there is no admission fee for observatory public nights.

The Observatory is located on Wakefield Road (Rt. 82) less than a quarter of a mile west of Route 700 in Hiram. There is no parking at the Observatory. Visitors may park on permissible side streets near the Post Office, a short distance east of the observatory.

Updates on programming are available via the Observatory’s Twitter feed: @StephensObs or its website: StephensObservatory.org.