Jay Pasachoff Archives

June 23, 2011April 26, 2016 by Nancy Atkinson

Double Occultations This Week Will Reveal More Details About Pluto

Several teams of astronomers are taking advantage of a rare double event this week to learn more about the atmosphere and makeup of Pluto and its moons. The dwarf planet will occult, or pass in front of two different stars this week. One of the best viewing sites for these two events is in Hawaii, and eclipse-chaser Dr. Jay Pasachoff is there to record both events. “To see those occultations, we have to be in a particular set of places on Earth, those over which the shadow of the object in starlight passes,” Pasachoff wrote in a guest post on the Planet Hunters blog. “Since the stars are so far away, their light is essentially parallel and the shadows of the objects on Earth are the same as the sizes of the objects.”

If all goes well, we will know a lot more about the Pluto system, Pasachoff said.

Map of where the occultation would be visible on June 22-23, 2011.

Last night, June 22/23, both Pluto and its moon Charon occulted a magnitude 14.4 star, with each occultation lasting a minute or so and separated from each other by 12 minutes. “The event is particularly exciting because if we capture both Pluto and Charon nearly simultaneously, we can find out about the system’s internal orbits with higher precision than before, perhaps allowing a refinement of the center of mass and thus the masses and densities of each object,” Pasachoff said.

Also, the first deployment for an occultation of the NASA/German SOFIA observatory took place last night to view the Pluto occultation, flying at an altitude of 43,000 feet off the west coast of Central America.

“The scientific goal is to catch the ‘central flash,’ which conveys vital information about conditions in Pluto’s global atmosphere,” wrote American Astronomical Society press officer Rick Fienberg on Twitter. Fienberg was part of the press corps that was accompanying the flight.

On Sunday/Monday night, June 26/27, Pluto will occult a different star, and over a much narrower path, its small moon Hydra might also occult another star.

Pasachoff said that the most recent predictions for last night’s occulations shifted the prediction south, so that Hawaii is slightly off the main predicted path, to its north. But other teams are in Cairns, Australia, to see if it goes that far south.

For the June 26/27 event (June 27 UT but June 26 in Hawaii), the star is magnitude 13.6. “That is a couple of magnitudes brighter than most of the stars we have observed being occulted,” Pasachoff said, “so the data would be particularly low-noise. In addition to the occultation of Pluto itself, whose southern limit is predicted to pass through the Hawaiian islands, the tiny Pluto moon Hydra is to be occulted, though that narrow path’s prediction now passes north of the Hawaiian islands. We have arranged for telescopes in Yunnan, China, in Japan, Taiwan, and Thailand to observe with us, and MIT’s Matt Lockhart is en route to Yunnan with one of our POETS (Portable Occultation, Eclipse, and Transit System) cameras. We have Australian sites still observing as well, just in case the actual path is hundreds of kilometers south of the predictions.”

Earlier occultations by Pluto studied by Pasachoff and his colleagues showed that Pluto’s atmosphere was warming and that the atmosphere would probably remain warm enough by 2015 for the New Horizons spacecraft to detect and study it with its on-board instruments, and was part of the incentive for the mission to launch when it did.

To learn more about the occultations and the research, check out this main stellar occultation website from Williams College, where Pasachoff is located, which has links to the work of other researchers as well.

Maps and details of the predictions can be found here, and more details about Pluto occultations websites can be found here.

We’ll try to provide an update of the events when details become available.

You can follow Universe Today senior editor Nancy Atkinson on Twitter: @Nancy_A. Follow Universe Today for the latest space and astronomy news on Twitter @universetoday and on Facebook.

December 23, 2010January 22, 2021 by Nancy Atkinson

Upcoming Solar Eclipse on January 4, 2011

Williams astronomer Jay Pasachoff during the partial phase of the March 29, 2006 solar eclipse. Photo by Anna Tsykalova.

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Some of the world will be able to greet the first part of the new year with a solar eclipse. On the morning of Tuesday, January 4, 2011, an eclipse of the Sun will be widely visible across Europe and as far east as India. The eclipse won’t be visible in North and South America, however. Jay Pasachoff of Williams College in the US is the Chair of the International Astronomical Union’s Working Group on Eclipses, and says that even at a maximum, this eclipse will be only partial, with some of the Sun always visible. Because the Sun is too bright to look at safely, Pasachoff stresses that special solar filters or projection methods should always be used to protect the eyes.

Pasachoff will be in Tel Aviv to view the eclipse, and since partial eclipses are usually not very scientifically useful, he is looking forward to just enjoying the eclipse instead of scrambling to set up various scientific equipment.

“Partial eclipses are fun, and much more relaxing for a total-eclipse scientist like me, since the pressure on me is low and nothing happens too fast,” he told Universe Today. “Seeing a partial or other solar eclipse happen right on time, to the second, can be inspirational to students to study hard so that they, too, can understand the Universe.”

This will be Pasachoff’s 52nd solar eclipse.

Radio astronomers do find partial eclipses useful, as with a radio telescope, or in the ultraviolet or x-rays from spacecraft, scientists can use the timing of when solar active regions are covered and uncovered to study the structure of solar storms in better detail than is otherwise possible, Pasachoff said.

For this eclipse, people in Western Europe will find the Sun already eclipsed as the day begins, with the eclipse lasting about 80 minutes more. On January 4, the Moon will gradually cover the Sun, over a period of about 3 hours. At maximum, the eclipse will be at the horizon at sunrise in England, with 75% of the Sun’s diameter covered, and then gradually emerge over the next hour and 20 minutes. In Paris or Berlin, 80% of the Sun will be covered near sunrise. Farther east, the Sun will be a bit higher in the sky at maximum, 22° high with 67% covered in Athens. In Israel and Egypt, the Sun will be 33° high with over 55% coverage at maximum.

The most important thing, Pasachoff said, is to view an eclipse safely.

“Whenever the ordinary Sun is visible, even only part of it, you should not stare at it,” he said. “Special solar filters are available cheaply, or dense welders’ glass will do. Another method of seeing that the Sun is eclipsed is to punch a hole a few millimeters across in a piece of cardboard and hold it up to the Sun while you face away from the Sun and see the Sun’s image projected on the ground or onto another piece of cardboard. This method is called projection with a pinhole camera. It is rare that haze or clouds are sufficient to reduce the Sun’s intensity enough that one can see a partially covered Sun safely.”

2011 is unusual in that it has only four partial solar eclipses, for all of which the darkest part of the Moon’s shadow passes off the Earth’s surface. In 2012, an annular eclipse in which the Moon’s disk is a little too small to cover the entire Sun will pass from Japan over the Pacific to California and farther into the U.S. on May 20. On November 14, 2012, a total solar eclipse, in which it becomes dark as twilight, will start in northeastern Australia and cross a broad swath of the South Pacific.

For further information:

The International Astronomical Union’s website about eclipses with information on how to view an eclipse safely and why solar eclipses are interesting.

NASA’s website from Fred Espenak with maps, and tables for cities around the world.

Webcasts:
Israel Astronomy Society at Givatayim Observatory
www.astronomy.org.il
www.education.org.il

University of Barcelona’s Department of Astronomy and Meteorology.

Bareket Observatory, a private observatory in Israel.

July 9, 2010December 24, 2015 by Nancy Atkinson

July 11 Total Eclipse Among the Mysterious Moai

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A group of astronomers are now on the mysterious Easter Island, one of the few solid places to stand on Earth where a total solar eclipse will be visible on July 11, 2010. The majority of the eclipse’s path is over the ocean, so this will be one of the least observed eclipses ever. “This is one of the most interesting things that is possible for anyone on Earth to see in one of the most interesting places on the Earth that people can go,” said Jay Pasachoff from Williams College, who is the Chair of the International Astronomical Union’s Working Group on Eclipses. This will be his 51st eclipse.

While the eclipse is thousands of miles long in its is path of totality on Earth, it is just a few hundred miles wide. It will pass through French Polynesia on the Cook Islands, but, Pasachoff said, it doesn’t go through any of the main islands. “It misses Tahiti, but there are some atolls off the side of the path, and some eclipse scientists and ecotourists will be on cruise ships that are going into the path of totality. There will also be a group on an airplane observing the eclipse and we hope to compare all the other observations with the ones we get from Easter Island,” he said.

Easter Island is 4023 km (2,500 miles) west of Chile, and is famous for the Moai, giant statutes that were left by a Polynesian culture that mysteriously disappeared. But while the statues’ constant gaze look outward, all human eyes will be on the skies on July 11.

“The actual four minutes and forty-five seconds of totality that we are scheduled to have at Easter Island will be very exciting, as the last sliver of the sun is covered we can then take off the protective filters we’ve been using,” Pasachoff said, “and look at the next few minutes without any protection because the solar corona is about the same brightness as the full moon and is equally safe to look at. In fact we’ve been having a debate recently about whether we can get a very brief warning on the so-called eclipse glasses that many people use because those glasses are only for when any of the everyday sun is visible. They are so dense that they block the solar corona entirely, and the few people who don’t understand what is going on enough to take those glasses off during totality miss the whole event. There are people who have missed past eclipses by not knowing they had to take their glasses off.”

Pasachoff is joined by Professor Marek Demianski and two students. They will be carrying out high-resolution imaging to look for motions in the corona and to follow the varying magnetic-field configuration in the solar-corona as a function of the solar-activity cycle. Though the sunspot cycle remains in an extreme low, some other indications of solar activity have been increasing and we are eager to see the condition of the low and middle corona. They expect to see motions at least in polar plumes.

Also, they will be using the images to fill in gaps between the observations of the corona on the solar disk taken with NASA’s new Solar Dynamics Observatory and the observations of the outer corona taken with the Naval Research Laboratory’s coronagraph on the Solar and Heliospheric Observatory. Pasachoff and his team have contributed to similar images for the past several eclipses but now will have the improved SDO images as part of their montage. Several of the cameras will be computer controlled using software called Solar Eclipse Maestro written by Xavier Jubier of France.

Universe Today hopes to talk with Pasachoff after the eclipse to hear about his experiences.

The Williams College team is accompanied by a documentary crew filming for National Geographic Channel, and their activities will be covered in a special program entitled Easter Island Eclipse partly pre-recorded and partly expected to have new eclipse footage that will air on the National Geographic Channel on the evening of July 11th, at 11 pm.

Here are some resource Pasachoff provided for the eclipse:

On Sunday, July 11th: total solar eclipse on Easter Island (same time zone as Mountain Time in the US)
Partial eclipse begins 12:40:36 Altitude of Sun: 40°
Totality begins 14:08:30 Altitude of Sun: 40°
Totality ends 14:13:10 Altitude of Sun: 39°
Partial eclipse ends 15:34:16 Altitude of Sun: 32°
Duration of totality: 4 minutes and 40 seconds

Times in UT:
18:40 UT 1st contact
20:08 UT 2nd contact: total eclipse begins
20:13 UT 3rd contact: total eclipse ends

His eclipse site for the International Astronomical Union

Google maps by Xavier Jubier and Fred Espenak

Espenak’s NASA Website, with maps and details

An interactive map

An animation of eclipse phenomena

Also, Pasachoff will talk about the eclipse on the July 10 365 Days of Astronomy podcast.

Here’s a link to USTREAM channel of the eclipse.

Update: I just received a note from Robin Zimmerman at DISH Network, and for those of you who have the DISH Network, there is a special channel, DishEARTH, Ch. 287, that features live 24/7 views of the earth from space and this Sunday the eclipse be shown. Robin said their network will allow people in the US to see the phenomena, live.

And here’s a video from National Geographic:

June 18, 2010December 24, 2015 by Nancy Atkinson

Occultation Reveals Distant Kuiper Belt Object is Surprisingly Icy Bright

An artist's rendering of a Kuiper Belt object. Image: NASA

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How do you study an extremely small planetary body in the dim outer reaches of our solar system? Get all your friends from around the world to wait for a very elusive – if not short-lived – special event. And in doing so, you may find something completely unexpected. Enter James Elliot from MIT, who worked with dozens of observatories and astronomers across the globe, including Jay Pasachoff from Williams College in Massachusetts, in an attempt to make observations of the Kuiper Belt Object 55636, (also known as 2002 TX300) a small body orbiting about 48 AU away from the Sun. Since this KBO is too small and distant for direct observations of its surface, the astronomers tracked and plotted its course, figuring out when it would pass in front of a distant star.

The KBO occulted, or passed in front of a bright background star, an event which lasted only 10 seconds. But in that short amount of time, the astronomers were able to determine the object’s size and albedo. Both of these results were surprising.

55636 was found to be smaller than previously thought, 300km in diameter, but it is highly reflective, meaning it is covered in fresh, white ice.

Most known KBOs have dark surfaces due to space weathering, dust accumulation and bombardment by cosmic rays, so 55636’s brightness implies it has an active resurfacing mechanism, or perhaps that in some cases, fresh water ice can persist for billions of years in the outer reaches of the Solar System.

One graph of the occultation from the Las Cumbres Observatory. Credit: Elliot, et al.

42 astronomers from 18 observatories located in Australia, New Zealand, South Africa, Mexico and the US were part of the observations, but because of weather and timing, only two observatories, both in Hawaii, were able to detect the occultation. Working with Wayne Rosing, Pasachoff coordinated the observations at the Las Cumbres Observatory Global Telescope Network located at Haleakala Crater on Maui, Hawaii, which made the best observations.

But Pasachoff told Universe Today that having two different angles of view to work with provided the ability to make quite precise measurements of the KBO.

“It was absolutely crucial to have the second observation site,” he said. “Without it, we
would not have known where on a round or elliptical body the chord, the line of occultation, passed and we could not have set an upper limit to the size of the body.”

A chord near the edge of a huge body can be vanishingly small, Pasachoff added, illustrating why they needed at least two chords.

Although the surfaces of other highly reflective bodies in the solar system, such as the dwarf planet Pluto and Saturn’s moon Enceladus, are continuously renewed with fresh ice from the condensation of atmospheric gases or by cryovolcanism that spews water instead of lava, 55636 is too small for these mechanisms to be at work.

“The surprising thing in a billion-year-old object that is so reflective is that it maintained or renewed its reflectivity,” said Pasachoff, “so possibilities include the darkening that we know takes place in the inner solar system is much less way out there; or the object renews its ice or frost from inside. We need new observations or more KBO’s with occultations, and we need more theoretical work.”

This was the first successful “planned” observation of a KBO using the stellar occultation method. In 2009 another team scoured through four and a half years of Hubble data to find on occultation of an extremely small KBO 975 meters (3,200 feet) across and a whopping 6.7 billion kilometers (4.2 billion miles) away.

For several years, Pasachoff and his team from Williams College have worked with Elliot and others from MIT, as well as Amanda Gulbis of the South African Astronomical Observatory to study Pluto by occultation. With careful measurements of a star’s brightness as Pluto hides or occults it, they have shown that Pluto’s atmosphere was slightly warming or expanding. A main goal now is to find out how the atmosphere is changing. This will be especially significant with the New Horizons spacecraft en route to Pluto.

Pasachoff said he knew 55636’s albedo would be bright, but was surprised how bright it was. The origins of this object is believed to come from a collision that occurred one billion years ago between one of the three known dwarf planets in the Kuiper Belt, Haumea and another object that caused Haumea’s icy mantle to break into a dozen or so smaller bodies, including 55636.

“Mike Brown (KBO and dwarf planet hunter from Caltech) told me last year, before the observations, that the object would be reflective since it is in the Haumea family, and Haumea itself has a high albedo,” Pasachoff said.

Pasachoff worked with Brown and his team last year in trying to capture the mutual occultations of transits of Haumea with its moon Namaka using the Palomar 5-meter telescope, but they weren’t successful in detecting the extremely small effect, given Haumea’s rapid rotation period.

Elliot used the occultation method to discover the rings of Uranus decades ago and continues to champion the method.

Pasachoff said the recent observation of 55636 was very rewarding. “It was an incredible observation, and I was very pleased to be part of it.” He said. “I am proud that all three of the graphs in the Nature article, and both of the successful observations, were arranged or made by our Williams College team.”

He added that any such observation includes at least these four elements: astrometric predictions, observations, reduction of data, interpretation.

“We were very fortunate and interested in being successful with observations,” Pasachoff said. “But it is important to note that Jim Elliot and his colleagues at MIT and Lowell Observatory have been working for years to refine the methods of predictions to get them accurate enough for this purpose. And this event was the first time that the predictions had been accurate enough to merit the all-out press of telescopes that we assembled. That we picked up the event, near the center of the prediction to boot, is a credit to the astrometry team.”

Note: This article was updated on 6/20.

The team’s paper was published in the journal Nature.

Sources: Williams College,(and email exchange with Jay Pasachoff), MIT, BBC, Nature

January 18, 2010April 26, 2016 by Nancy Atkinson

Annular Eclipse Photos, Videos From Earth and Space

Caption: Annular solar eclipse on January 15, 2009. Courtesy Daniel Fischer, “cosmos4u” on Twitter.

The first of two solar eclipses to occur in 2010 took place Friday, January 15. This was an annular eclipse, which means the Sun was not totally covered by the Moon, creating a “ring of fire.” The eclipse was visible from a 300-km-wide track that passed over central Africa, across the Indian Ocean, over the southern tip of India and the northern end of Sri Lanka, and then across parts of Bangladesh and Myanmar. At the center of the track, the eclipse endured for 11 minutes and eight seconds, setting a record that won’t be beaten until December 23, 3043. Weather cooperated in many regions, allowing good viewing conditions. Here are a few images and videos from Daniel Fischer, who was in Varkala, India, and another group who calls themselves Eclipse Hunt 2010 crew were in Jaffna, Sri Lanka. The image above is from Fischer, who said via Twitter that his travels to view the eclipse was a total success. “Deep blue sky, not a single cloud all day, photo plans worked.”

Annular eclipse, Jan 15, 2010 by Shehal Joseph and Romayne Anthony. Courtesy Elipse Hunt 2010 website

This image is from the Eclipse Hunt 2010 crew, in northern Sri Lanka. It was taken by Shehal Joseph and Romayne Anthony. They used a Celestron NexStar 5se telescope with a focal length of 1.25m, and an energy rejection filter.

Why the “ring of fire?” During an annular eclipse, the moon is a little further than average away from the earth and its angular size in the sky is therefore slightly smaller than the angular size of the sun. So it is like the Moon is silhouetted against the Sun, and it doesn’t cover the Sun entirely. A a ring, or annulus, of sunlight can be seen around the black disk of the moon.

The Moon casts a shadow on Earth, as seen by NASA's Aqua satellite from space. Credit: NASA

NASA’s Aqua satellite was looking down from space at 1:15 p.m. Calcutta time (7:45 UTC) on January 15, 2010, and saw the Moon’s shadow cast on Earth. The Moderate Resolution Imaging Spectroradiometer (MODIS) on Aqua images this shadowed area in India and the Bay of Bengal. The shadow spanned a north-south distance of about 300 kilometers (185 miles) on the surface, with the darkest part near the mid-point of the span.

The Sun's chromosphere was visible in a long exposure. Credit: T. Kampschulte

This is another image from the Fischer’s group of astrophotographers in India. By taking a long-exposure image, the sun’s chromosphere was able to be seen.

Normally with an annular eclipse, not a lot of science is able to be done, said Jay Pasachoff, who leads the IAU’s working group on eclipses. “Because it doesn’t get completely dark, we won’t be able to see the solar corona, the diamond ring, or the fantastically interesting and beautiful phenomena that one sees at a total solar eclipse, but still annular eclipses are interesting to see,” Pasachoff said on the 365 Days of Astronomy podcast. “You have to keep a solar filter on to look through for the whole time. The partial phases that last an hour and a half and the annular phase, which, for this eclipse, lasts, in many places, over ten minutes – very long for an eclipse.”

Interestingly, the images shown here by Fischer’s group used a very low-tech combination of a compact camera and their filters were two “rescue sheets,” the thin aluminum foil-like thermal blankets usually given out during emergency situations, such as the recent earthquake in Haiti.

The Eclipse Hunt 2010 crew took a few videos of the eclipse, using the projection method. See more of their videos here at their You Tube page. And see more images on their website, Eclipse 2010. Special thanks to Prasanna Deshapriya, one of the members of the Eclipse Hunt 2010 crew, who shared these images. Check out his website about the IYA in Sri Lanka.

A high resolution image from a telescope in India. Credit: T. Kampschulte

This high-resolution image obtained using a telescope was taken by Fischer’s group in India. “The Ring of Fire is closed, but just barely; it measures a few arc seconds only in places in this super-sharp telescopic image,” said Fischer, via Twitter.

For more eclipse images go to:

Spaceweather.com’s eclipse gallery

Flickr’s eclipse thread