PS1SC Blog

The vicinity of the Solar system, the nearby few hundred light-years, has been a prime source of astronomical discoveries for many centuries. The average distance to stars that are similar to the Sun and visible to the naked eye is less than 120 light-years. This is the very neighborhood of the Sun when you think that the center of our Galaxy is located some 25,000 light-years away! Those are the stars that made up the “sphere of the fixed”, past the Moon, against which astrologers and early astronomers such as Kepler measured the movement of celestial bodies of the Solar system and eventually, let Galileo and Newton discover the law of gravity.

When the invention of the telescope in the 17th century allowed astronomers to observer fainter stars and accurately measure their position, it appeared that the “fixed stars” were not that fixed. Many showed small motions compared to other stars over the years, and some additionally show a circular, yearly motion, reflecting the revolution of the Earth around the Sun. These motions, which are greatest for the stars closest to the Earth, allowed scholars to discover the Sun’s neighbors and to measure their distance.

In the 20th century, the observations of the sky with photographic plates led to the discovery of most nearby stars more massive than a few tenths of the Sun’s mass. Today, Pan-STARRS 1 will use exactly the same methods, with greater accuracy and sensitivity, to detect all nearby stars in the Northern sky and measure their distance. The greater accuracy will allow us to expand the “Solar neighborhood” to about 250 light-years, and the greater sensitivity to detect the coolest stars, as well as compact objects not massive enough to burn hydrogen as stars do, which are called brown dwarfs.

One key project of the Pan-STARRS 1 Science Consortium is dedicated to the study of our stellar backyard. Astronomers from across the PS1SC including Eugene Magnier and Michael Liu from the University of Hawaii and I have been working to take a complete census of the nearby low-mass objects, both stars and brown dwarfs. The detection of all very-low mass stars and brown dwarfs in the Solar neighborhood may reveal the closest Solar neighbor, possibly closer than the current holder of that record, Proxima Centauri at 4 light-years. Because they are close, those objects are the brightest among their peers, so that it is possible to observe and characterize them with greater details.

2MASS J09201223+3517429 imaged by Pan-STARRS 1, indicated by an arrow. While it appears as a single red dot, it is actually a binary pair of brown dwarfs. Pan-STARRS 1 will discover hundreds of new brown dwarfs. Credit: PS1SC

Like stars, brown dwarfs form from the collapse of a huge cloud of gas. However unlike stars they cool and dim with time, because they lack an internal energy source. This makes it difficult to determine important parameters like age or mass, because a young, low-mass brown dwarf will look like an older, more massive one. Sometimes we can learn more from a stellar companion, or from the stellar cluster if the brown dwarf belongs to one.

The atmospheres of very low-mass stars and brown dwarfs have temperatures of a few hundred degrees to a few thousands Fahrenheit. Because of such a large range of temperatures, the atmospheric chemistry is diverse and complex. We know that dust clouds are present, but sometimes hidden below a layer of water and methane. The coolest known dwarfs have ammonia; even cooler dwarfs may have water ices. It seems that different dust properties change the colors of brown dwarfs, as well as the proportion of heavier elements they have, or ages. Only when we discover and characterize more objects will we understand better their properties. This will also help us to understand the atmospheres of gas giant planets around other stars. But these cold brown dwarfs won’t be the only near neighbors of the Sun we will search for with PS1.

Most of the stars in the Solar neighborhood belong to a flattened structure of our Galaxy called the Thin Disk, which we see as the Milky Way on the sky. That disk sits in a dimmer and older structure, almost spheroidal, called the Halo, which extends to great distances. A small fraction of the nearby objects are actually members of that Halo. Detecting and studying them, for instance old white dwarfs, which are the dead remnants of aged stars which were originally similar to the Sun, provides information on the Halo, such as its age and origin.

On the contrary, another small fraction of the Solar neighborhood is made of young objects which just escaped their stellar nursery, or maybe were born in isolation. Again studying them with great precision allows us to understand the formation of very low-mass stars and brown dwarfs, which may differ from both higher-mass stars, and lower-mass extrasolar planets. We can also search for young planets and gas and dust disks orbiting the young dwarfs. With the present instrument those are visible only close to the Earth.

Finally, thanks to our repeated observations of the whole Northern sky, we will discover most variable stars having variations as small as 1% in their light output. These stars may be young stars, still erratically accreting material from disks of material left over from their formation; or eclipsing stars, whose light is occasionally blocked by a companion or a planet; or magnetically active stars which show variations due to massive flares in their atmosphere.

The Solar neighborhood is a diverse mixture of stellar populations reflecting the past and present of the Galaxy. As we come to describe it more completely, we learn about the life of stars from birth to death, or their companions and planets, and of the physics that control their atmospheres and their evolutions. Pan-STARRS 1 will be a key tool in these investigations over the coming years.

One of the many exciting aspects of being involved in the Pan-STARRS PS1 survey is the potential to utilize its data products for education and public outreach purposes (EPO). Members of the PS1SC have recently completed some extremely successful work with the International Astronomical Search Collaboration to allow high school students in Germany, Texas, and Hawaii an opportunity to use images collected by PS1 to make asteroid discoveries. This first “pilot project” of 10 schools will be expanded to about 30 schools in a second “campaign” to be conducted during Spring 2011, and eventually the expansion could reach several hundred or even a thousand schools (thousands of students). And because of the vast amount of data produced by the wide field PS1 images, it requires only a handful of images to support such a large number of schools. For me the most gratifying part of bringing asteroid searches into the classroom is the high enthusiasm expressed by both the students and their teachers for participating in this program.

For the past few months we have teamed up the Pan-STARRS 1 telescope, designed to become one of the world’s most powerful asteroid hunters, with school students from the USA and Germany to discover and study asteroids – clumps of rock, between a couple and a few hundred kilometers in size, that cruise through our Solar System. At the close of the campaign, which was coordinated by the International Astronomical Search Collaboration, the students can look back on exciting eight weeks of asteroid search, which included the confirmation of four “Near-Earth Objects” (asteroids passing relatively close to Earth) and the discovery of what could turn out to be more than 170 previously undiscovered asteroids.

Asteroid 2010 UR7, confirmed as a Near Earth Object by students at Gymnasium Neckargemünd near Heidelberg. The object is indicated by the white box and appears as a faint streak as it moves through the solar system so fast it is blurred out in even a 40s image! Credit: PS1SC

As the 1.8 meter (71-inch) Pan-STARRS 1 telescope (PS1), one of the most powerful current survey telescopes, scans the night sky, its 1400 Megapixel digital camera takes more than 500 exposures per night. Between October 25 and December 21, 2010, a small fraction of these data found its way into classrooms in the USA and in Germany, where high-school students have used it to track known asteroids, and also to discover candidate objects that could be previously unknown asteroids. When Hawaiian skies were overcast, schools also received data taken with a telescope operated by the Astronomical Research Institute (ARI) in Westfield, Illinois.

Over the Internet, the participating schools received series of astronomical images. Each series included images of one specific region of the sky, taken an hour apart. During this hour, the image of a main belt asteroid (one lying between Mars and Jupiter) would have moved noticeably (in the images in question: about 100 pixels) relative to the distant background stars. The students examined the images for exactly this kind of position change, carefully sorting image artifacts from moving celestial objects, and reported back to the International Astronomical Search Collaboration, whose volunteers then checked the results and arranged for follow-up observations.

Some of the most interesting student observations during the project concerned “Near-Earth Objects” (NEO), asteroids or similar objects whose orbits bring them into the inner Solar System. Some NEOs might turn out to be potential “killer asteroids” that are bound to collide with our home planet; finding these is one main goal of the PS1 telescope. In order to keep track of NEOs, at least two separate observations at different times are required. Katharina Stöckler (age 17), an 11th grade student at Gymnasium Neckargemünd near Heidelberg, explains:

“We obtained a ‘NEO confirmation’ for the asteroid 2010 UR7 – the second observation ever made of that object, which confirmed the asteroid’s existence and gave crucial information about its orbit.”

Three additional such “NEO confirmations” were made during the project; in addition, 64 of the students’ observations amounted to the third or fourth time a specific NEO had been observed. All these observations provide important additional data to scientists studying the motion of NEOs.

In the course of the project, the students also observed 151 candidate objects in the Pan-STARRS data (plus an additional 20 candidates in the ARI/Westfield telescope data) that could be newly discovered main belt asteroids, which orbit the Sun between the orbits of Mars and Jupiter. In one case, students from Benedikt Stattler Gymnasium, a high-school in Bavaria, Germany, discovered 7 such candidate objects in a single night! Before the students’ finds are confirmed as discoveries, however, and assigned provisional designation numbers, they will need to be observed again – for a number of the candidates, this is going to prove impossible; on the other hand, some are likely to turn out to have been previously known, after all. Once a newly found object has been observed over at least a whole orbit (which typically lasts 3 to 6 years), it is assigned a definite numerical identifier, and can also be given a proper name.

IASC director Dr. Patrick Miller, of Hardin-Simmons University in Abilene, Texas, says:

“Pan-STARRS images contain an amazing amount of data, providing students with opportunities for literally hundreds of new discoveries. With this amount of data, we could expand our campaign to a thousand schools a year, and tens of thousands of students, which is very exciting, and is an unbelievable opportunity for high schools and colleges!”

It is incredibly exciting that we can use a state-of-the-art system such as Pan-STARRS to allow students around the world to learn astronomy with real research quality images. We hope we’ve made this a valuable and enjoyable experience for both the students and their teachers. Hopefully this is only the first step in eventually involving as many as a thousand schools around the world.

If you’re interested in your school getting involved please email me at burgett AT ifa.hawaii.edu

More information can be found in this press release:

“Successful hunt for asteroids in the classroom”
Dr. Markus Pössel, Center for Astronomy Education and Outreach
Max-Planck-Institute for Astronomy

The participating international teams of schools were:

1. Luitpold-Gymnasium, Munich, Germany
Ranger High School, Ranger, Texas

2. Christoph-Probst-Gymnasium, Munich, Germany
May High School, May, Texas

3. Benediktinergymnasium Ettal, Germany
Vernon High School, Vernon, Texas

4. Benedikt-Stattler-Gymnasium, Bad Kötzting, Germany
Bullard High School, Bullard, Texas

5. Werdenfels-Gymnasium, Garmisch-Partenkirchen, Germany
Colleyville Heritage High School, Colleyville, Texas

6. St. Anna-Gymnasium, Munich, Germany
El Campo High School, El Campo, Texas

7. Helmholtz-Gymnasium, Heidelberg, Germany
Tarrant County College, Hurst, Texas

8. Gymnasium Neckargemünd, Neckargemünd, Germany
Brookhaven College, Farmers Branch, Texas

9. Lessing-Gymnasium, Lampertheim, Germany
Madisonville High School, Madisonville, Texas, and Baldwin High School, Wailuku, Hawaii

10. Life Science Lab, Heidelberg, Germany
Collin County College, Plano, Texas

The PS1 Observatory on Haleakala. Photo Credit: Rob Ratkowski, PS1SC

Hello and welcome to Pan-STARRS 1 Science Consortium blog. Pan-STARRS is a planned system of four telescopes (funded by the US Air Force) that will repeatedly survey the sky visible from Hawai’i. The first of these eyes on the sky, Pan-STARRS 1 (PS1), began operations on Haleakala on Maui in May 2010. While its primary purpose is to scan the skies for asteroids that could one day hit the Earth, it will also discover comets, study the coolest, faintest neighbours of our Sun, search for planets around other stars, explore the structure of our Galaxy and its siblings, seek out distant black holes and exploding stars and even probe the mysterious dark matter and dark energy that make up over 90% of our universe. This groundbreaking telescope is operated by the Pan-STARRS 1 Science Consortium consisting of the Institute for Astronomy, the University of Hawai’i, the Max Planck Institute for Astronomy, Heidelberg and the Max Planck Institute for Extraterrestrial Physics, Garching, The Johns Hopkins University, the University of Durham, the University of Edinburgh, the Queen’s University Belfast, the Harvard-Smithsonian Center for Astrophysics, the Las Cumbres Observatory Global Telescope Network and the National Central University of Taiwan and also receives funding from NASA.

Pan-STARRS 1, a 1.8m telescope, comes equipped with the worlds largest digital camera which has 1.4 billion pixels (over 250 times the number of pixels in an iPhone’s camera). This along with the telescope’s design allows it to observe with a three degree field of view (six full moons across), meaning it can cover the sky visible from Hawai’i 20 times per year.

Over the next few months we’ll be bringing you posts outlining the exciting science PS1 will be uncovering in the years ahead. That isn’t to say that it hasn’t yielded any scientific discoveries yet, in September last year PS1 data was used to identify a potentially hazardous asteroid which subsequently came close to the Earth in October. Here’s the ever telegenic Rob Jedicke being interviewed for the local news in Honolulu about this asteroid.