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Hubble Space Telescope Banner

Live from the Hubble Space Telescope


PART 1: Calling all weather watchers....last chance

PART 2: Upcoming live interactions

PART 3: A night of no observing

PART 4: Challenge Questions: an answer at last


The time is NOW to register your class or homeschooler as an OFFICIAL Live From the Hubble Weather Reporter!

Next week, April 15-19, students across the nation will be reporting their daily weather observations (wind speed/direction, cloud type and cover, temperature) in a nationwide effort to provide DATA POINTS across the US (and Canada). The weather data will be incorporated into our web-based Passport to Knowledge weather maps enabling students to make comparative studies, analyses, and predictions of weather on Earth. The student's collaborative efforts parallel our Planetary Advocates analysis of weather and seasons on Neptune and Pluto.

More details can be found at our web site under Featured Activities --- Collaborative Weather Activity or here.

The webless are also invited. They can get more details by sending a mail message here.


The Mountain States--Utah, Montana, Idaho, Colorado, New Mexico, Arizona, Wyoming

Mid-US: South Dakota, Illinois, Wisconsin, Northern Michigan

The South--Louisiana, Arkansas, Mississippi, Alabama, South Carolina and West Virginia

The East--Vermont, New Hampshire, Connecticut, and Massachusetts

It is not too late to register! We have 40 schools from around the United States and Canada, but we WANT YOU!! Join this opportunity to make local weather observations, collect data, and contribute your input and serve as our own special WEATHER WATCHING TEAM.

Fill out this form and mail it hereASAP.


Name of School:
Teacher's Name:
Latitude (given in degrees N):
Longitude (given in degrees W):


This coming week will feature another opportunity for your students to interact with experts of the Hubble team. Please consider joining us.

On Wednesday, April 17, Alex Storrs and Tony Roman from the Space Telescope Science Institute will be available on CU-SeeMe. Their topic will be "How we prepared the HST to make your Pluto and Neptune observations". They will also be able to answer general astronomy questions.

Two separate sessions will be offered: from 9-10am Pacific (noon-1pm Eastern) and 11am-noon Pacific (2-3pm Eastern).

To participate, use the following CU-SeeMe reflector sites: (first choice) and (alternate if the primary experiences problems)


Trisha Borgman

April 11, 1996
Hi everyone! Well, our last night of observing at Kitt Peak was completely washed out by the clouds. We waited in the console room for several hours, hoping that the weather would clear up for us. But, at about midnight, we received a message from the telescope operator at the 4-meter telescope saying that all domes must close due to high winds and blowing snow. We weren't actually getting any snow where we were, but the wind was unbelievably strong. Just before we received that message, though, as we sat quietly in the console room, we heard a loud CRASH! We both jumped out of our seats and ran into the dome, fearing that perhaps the telescope supports and been damaged by the wind, or that some other piece of equipment had crashed into the telescope. We were lucky--the crash had been caused by a safety helmet in the dome which was blown off its hanger on the wall. The helmet flew all the way down the stairs into the hallway outside the console room, where it crashed into the wall. Boy, did that ever wake us up!!!

At one point during that last night, though, it appeared that the weather would, in fact, clear up! We sprang into action and began planning our observations for the rest of the night. This time, it was my turn to do all of the planning. I spent about an hour or more looking through our list of target stars, computing when the observations should be taken, and calculating how long the exposure times should be. But...as soon as we were ready to go, the clouds were back. Even though I only had an hour or so to do the planning, it was a good experience to get all that practice! I just wish we would have been able to observe... It was kind of sad to leave the telescope for the last time--it had become my home for 4 fabulous nights. Maybe I'll be able to go back someday. I sure hope so!

We left the mountain the next day. When I woke up, I looked out the window and said to myself, "Wow--it looks just like we're in an airplane, flying through a cloud!" And then I realized we weren't on an airplane! The clouds had become so thick and so low that, since we were still on top of the mountain, we were actually inside the cloud! It was cold and damp, and so humid that the water condensed on the branches of the trees...then, when the wind blew, it felt like it was raining!

Anyway, I spent another day at home with my parents, then came back to Baltimore. What an experience!!! Wow. I've been looking at some of our images, and they really look fantastic!

Do you remember the mysterious "wispy clouds" we found in one of the images we took? Well, I still haven't figured out what they are. My boss has been out of town, so I haven't been able to ask for his help. Hopefully, he'll be able to take a look at them next week. I promise to keep you posted about what I learn!

Well, I need to get back to work. I will write more next week!
:) Trisha


The week before last, we asked:
Pick two spots on Pluto (other than the poles) that are on opposite hemispheres. From these two vantage points, describe the phases of the moon, Charon, that you would see. (Hint: there are two periods of time to worry about, one long and one short.)

We have two different answers to this question, one from Marc Buie and another from Sanjay Limaye of the University of Wisconsin - Madison:

Marc Buie writes:

There are three parts to this answer.

  1. Let's pick two spots on Pluto. To make life easy, both locations are on the equator, one at 0 degrees longitude (Pluto's equivalent of Greenwich, England), and one at 180 degrees longitude (Pluto's equivalent of the international date line). The trick here is knowing that the length of Pluto's day is exactly the same as Charon's orbital period. That means Pluto always presents the same face toward Charon and Charon always presents the same face toward Pluto. This is just what our own Moon does. What is different, is that standing on Pluto, Charon does not appear to move relative to the horizon. That means you never see a moonrise from Pluto's surface. This also means that over half the planet, you can never see Charon. The longitude system is defined such that 0 degrees longitude is in the center of the hemisphere that can see Charon. So, from 180 degrees you wouldn't see any phases at all. The rest of the answer will deal just with the side of Pluto where you can see Charon.

  2. The quickest change in the phase of Charon happens during one orbit of Charon around Pluto. This orbit takes about 6.4 days. Let's consider the time when the Sun is directly over the equator. This time of "year" coincides with the start of spring. At "new" moon, Charon would be directly in front of the Sun and we'd see an eclipse. Then as Charon moves in it's orbit it would progress through the same phases that our own moon exhibits every month, taking only 6.4 days to complete the cycle.

  3. Another longer term cycle also affects the phases and that is Pluto's orbit around the sun. Since Pluto's rotation axis is tipped on its side, it has very pronounced seasons. Unlike our Moon, Charon also undergoes the same exact seasons. The only time you'd see a completely full moon would be at the start of spring or fall. At the start of summer or winter, just over half the surface would be illuminated at its fullest, either the north or south polar regions depending on the season.
Marc has created diagrams for this answer which can be found here.

Sanjay Limaye from the University of Wisconsin - Madison writes:

What an excellent question! However, the answer is not easy unless you are familiar with the Pluto/Charon geometry. Let's begin at the beginning.

To describe the phase of Charon from Pluto requires a knowledge of

  1. Charon's orbit around Pluto

  2. Pluto's orbit around the Sun

  3. the orientation of Pluto in orbit

Remember, that "phase" describes the amount of illumination from the Sun, so we need to determine the relative positions of the Sun and Charon as seen from a point on the surface of Pluto.

Pluto's orbital is now relatively well known, although future improvements are likely since Pluto has now been observed since its discovery in 1930 for less than one third of its orbit around the sun (one Pluto year equals 248 earth years). Its orientation has been determined from the knowledge of the orbit of its moon, Charon, which has a period of 153 hours 18 minutes (6.38722 days) around Pluto. Charon is believed to be in synchronous rotation around Pluto, meaning that Pluto must also rotate about itself in the same period, 6.38722 days. Further, Charon's orbit is believed to mark the equatorial plane of Pluto, i.e. the spin axis of Pluto is parallel to that of Charon. This direction can be described by the location of Pluto's 'pole' position, or the positive spin axis (don't look up any books on astronomy, you won't find this information there!) which is at 311.63 degrees right ascension and 4.18 degrees declination (right ascension and declination are astronomical equivalents of longitude and latitude in the equatorial co-ordinate system). But exactly where is this direction? Unless you can visualize RA and Dec values into position in the sky, here is a clue. Between 1985 and 1990, we know that earth was in the plane containing the orbital plane of Charon (and hence Pluto). This how the surface of Pluto was first mapped, by observing the obscuration of Pluto by Charon every 153h1 18m apart as Charon came in front of Pluto and went behind it as it moved in its orbit. It is easy to locate earth and Pluto during that period, and that gives a good idea of the orientation of Charon's orbit around Pluto, and hence of where Pluto's spin axis is pointed at. We need to know to see how the phase of Charon would appear from Pluto.

Since the orientation of the spin axes does not change as Pluto and Charon move in their respective orbits, it is clear that at some point in future, roughly a quarter of the orbital period from about 1985, or, around 2050 (=1987+248/4), the equatorial plane would be normal (90 degrees) with the direction to the Sun. At that point, from any point on Pluto, the phase of Charon would be half moon, continuously, from either the north or the south hemispheres of Pluto, and in fact, the entire northern hemisphere of Pluto will be in continuous sunlight and the southern hemisphere will be in continuous darkness (ignoring for the moment the orbital inclination of Pluto, which is actually substantial, 17 degrees). This situation will change when Pluto changes its orbital position enough so that its spin axis is sufficiently away from the direction to the sun from Pluto, until half an orbital period later, when it will recur, except that the dark and lit hemispheres of Pluto will be switched. In between, roughly half an orbital period from 1985-1990, the earth will pass again through the Charon orbital plane, recreating the mutual eclipse events. At that time, Charon will undergo a complete change between new moon and full moon every 153 hours. Of course, Charon and solar eclipses will also occur occasionally,

At other times in its orbit, Charon will depict crescent and gibbous phases repeating every 153 hours or so, never achieving full phase or new moon.

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