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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.

Graphic: International Observe the Moon Night - 2019

Save the Date! International Observe the Moon Night will take place on October 5th 2019.

Stephens Memorial Observatory of Hiram College will host a Public Night Saturday, October 5, from 7:00 to 9:00 p.m. Earth’s Moon will be featured as our local participation in International Observe the Moon Night — a worldwide appreciation of Earth’s nearest neighbor in space. As an exciting bonus, planet Saturn will float near Moon in our skies and will also be observed. Other objects may also be viewed. Given good viewing conditions the Observatory’s 1901 vintage telescope delivers outstanding detail of the Moon and impressive views of Saturn with its distinctive rings.

An interesting activity any time of year is to make note of the daily changes we see in the phases of Moon. Open the PDF to print a handy guide and journal for lunar observation: Moon-Observation_Journal.

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.

Image: Saturn and Moons

Simulated View: Saturn and Moons, September 14, 2019 at 9:30 PM EDT. Image via Gas Giants

 

UPDATE: Thanks to the 29 visitors, of a wide variety of ages, who came out Saturday night to share the view with us. Early arrivals got good views of Saturn. In the middle of our evening our guests saw Saturn under improving conditions and the rising Moon as it cleared neighboring trees. Those who visited or stayed late viewed the Full Harvest Moon (sometimes through tree leaves). Our Moon, though fascinating to view through our telescope even when Full or nearly so, created huge amounts of natural light “pollution” as it illuminated atmospheric haze and thin clouds — we were unable to see the Great Andromeda Galaxy or the M15 star cluster. The Moon got tangled in trees again as it arced higher into the sky. Our final visitors of the evening, however, were rewarded for their patience with views of the Perseus Double Cluster after it cleared trees. We love trees but not so close to the observatory!

Stephens Memorial Observatory of Hiram College will host a Public Night Saturday, September 14, from 9:00 to 11:00 PM. On the observing list are: Earth’s Moon, Saturn, the Messier 15 star cluster, and, if sky conditions permit, the Andromeda Galaxy, and Perseus Double star cluster. Given good viewing conditions the Observatory’s 1901 vintage telescope delivers outstanding detail of the Moon and impressive views of Saturn and distinctive rings.

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.

Photo: Jupiter as imaged by the Hubble Space Telescope June 27, 2019.

The NASA/ESA Hubble Space Telescope reveals the intricate, detailed beauty of Jupiter’s clouds in this new image taken on June 27, 2019 by Hubble’s Wide Field Camera 3, when the planet was 644 million kilometers from Earth — its closest distance this year. The image features the planet’s trademark Great Red Spot and a more intense color palette in the clouds swirling in the planet’s turbulent atmosphere than seen in previous years. The observations of Jupiter form part of the Outer Planet Atmospheres Legacy (OPAL) program. Credit: NASA, ESA, A. Simon (Goddard Space Flight Center), and M.H. Wong (University of California, Berkeley)  — Click image to view full-size!

 
Among the most striking features in the image are the rich colors of the clouds moving toward the Great Red Spot. This huge anticyclonic storm is roughly the diameter of Earth and is rolling counterclockwise between two bands of clouds that are moving in opposite directions toward it.

As with previous images of Jupiter taken by Hubble, and other observations from telescopes on the ground, the new image confirms that the huge storm which has raged on Jupiter’s surface for at least 150 years continues to shrink. The reason for this is still unknown so Hubble will continue to observe Jupiter in the hope that scientists will be able to solve this stormy riddle. Much smaller storms appear on Jupiter as white or brown ovals that can last as little as a few hours or stretch on for centuries.

The worm-shaped feature located south of the Great Red Spot is a cyclone, a vortex spinning in the opposite direction to that in which the Great Red Spot spins. Researchers have observed cyclones with a wide variety of different appearances across the planet. The two white oval features are anticyclones, similar to small versions of the Great Red Spot.

The Hubble image also highlights Jupiter’s distinct parallel cloud bands. These bands consist of air flowing in opposite directions at various latitudes. They are created by differences in the thickness and height of the ammonia ice clouds; the lighter bands rise higher and have thicker clouds than the darker bands. The different concentrations are kept separate by fast winds which can reach speeds of up to 650 kilometers per hour.

These observations of Jupiter form part of the Outer Planet Atmospheres Legacy (OPAL) program, which began in 2014. This initiative allows Hubble to dedicate time each year to observing the outer planets and provides scientists with access to a collection of maps, which helps them to understand not only the atmospheres of the giant planets in the Solar System, but also the atmosphere of our own planet and of the planets in other planetary systems.

Saturn and Moons, July 10, 2019. Simulation via Gas Giants.

 

Stephens Memorial Observatory of Hiram College will host a Public Night Saturday, August 10, from 9:00 to 11:00 PM. On the observing list are two Stephens favorites: Earth’s Moon, and the Ringed World – Saturn! Other objects of interest may also be viewed using the Observatory’s 1901 vintage telescope. Given good viewing conditions the telescope delivers outstanding detail of the Moon and impressive views of Saturn and distinctive rings.

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.

Our 2019 Schedule

StephensAstro —  July 13, 2019 — Leave a comment

Personal, atmospheric, and astronomic factors have played havoc with planning our 2019 public observing schedule. We have, however, finally posted a list of Open Nights for the remainder of the year; it includes a special night and time in December in an effort to show off the Great Orion Nebula — something we’ve not done in years!

To view and/or print a copy of the newly-published schedule, CLICK HERE.

Please note that we may make changes as the season progresses. Of course weather plays a dominant factor and cloudy skies can, and often do, cancel scheduled events. Please check this website and our Twitter feed for updates

Keep looking up!