Bigger Isn't Always Better.

If you read the post below or the JPL press release on the exoplanets photographed with the Hale Telescope you may have been wondering what was meant by the term in the headline "small, ground-based telescope" or the fact that the image "was captured using just a 1.5-meter-diameter (4.9-foot) portion of the Hale telescope's mirror". Isn't the Hale a 5.1 meter (200-inch) telescope?

Yes, the Hale Telescope's primary mirror is indeed 5.1 meters across. So why would anyone chose to make a big telescope smaller?

If you look at the photo below, you can see that the Hale's prime focus cage, which hangs over the center hole in the mirror is held up by relatively thin "spider vanes" that obstruct small portions of the primary mirror.

This is a feature of virtually all reflecting telescopes. The astronomers who imaged the planets orbiting the star HR 8799 used an 1.5-meter unobstructed portion of the mirror.

Check out the cartoon version below to see what I mean:


The yellow circle represents the portion of the mirror that was used. This avoids any diffraction caused as the light goes past the spider vanes. Further, the adaptive optics system, which normally corrects over the full aperture of the mirror was used to correct over just the 1.5 meter aperture--giving a much higher level of corrections for distortions caused by Earth's atmosphere.

So by effectively making the Hale Telescope smaller, the research team lead by Gene Serabyn was able to achieve results that had previously been obtained by 8 and 10-meter class telescopes.
Cool stuff.

Exoplanets Imaged with Hale Telescope

From the JPL Press Release:

Small, Ground-Based Telescope Images Three Exoplanets

April 14, 2010

PASADENA, Calif. -- Astronomers have snapped a picture of three planets orbiting a star beyond our own using a modest-sized telescope on the ground. The surprising feat was accomplished by a team at NASA's Jet Propulsion Laboratory in Pasadena, Calif., using a small portion of the Palomar Observatory's Hale Telescope, north of San Diego.

The planets had been imaged previously by two of the world's biggest ground-based telescopes -- one of the two 10-meter (33-foot) telescopes of W.M. Keck Observatory and the 8.0-meter (26-foot) Gemini North Observatory, both on Mauna Kea in Hawaii. The planets, which orbit the star HR 8799, were among the very first to be directly imaged, a discovery announced in Nov. of 2008.

The new image of the planets, taken in infrared light as before, was captured using just a 1.5-meter-diameter (4.9-foot) portion of the Hale telescope's mirror. The astronomy team took painstaking efforts to push current technology to the point where such a small mirror could be used. They combined two techniques -- adaptive optics and a coronagraph -- to minimize the glare from the star and reveal the dim glow of the much fainter planets.

"Our technique could be used on larger ground-based telescopes to image planets that are much closer to their stars, or it could be used on small space telescopes to find possible Earth-like worlds near bright stars," said Gene Serabyn, an astrophysicist at JPL and visiting associate in physics at the California Institute of Technology in Pasadena. Serabyn is lead author of a report on the findings in the April 15 issue of the journal Nature.

The three planets, called HR8799b, c and d, are thought to be gas giants similar to Jupiter, but more massive. They orbit their host star at roughly 24, 38 and 68 times the distance between our Earth and sun, respectively (our Jupiter resides at about five times the Earth-sun distance). It's possible that rocky worlds like Earth circle closer to the planets' star, but with current technology, they would be impossible to see under the star's glare.

The star HR 8799 is a bit more massive than our sun, and much younger, at about 60 million years, compared to our sun's approximately 4.6 billion years. It is 120 light-years away in the constellation Pegasus. This star's planetary system is still active, with bodies crashing together and kicking up dust, as recently detected by NASA's Spitzer Space Telescope (http://spitzer.caltech.edu/news/1000-feature09-16-Unsettled-Youth-Spitzer-Observes-a-Chaotic-Planetary-System). Like fresh-baked bread out of the oven, the planets are still warm from their formation and emit enough infrared radiation for telescopes to see.

To take a picture of HR 8799's planets, Serabyn and his colleagues first used a method called adaptive optics to reduce the amount of atmospheric blurring, or to take away the "twinkle" of the star. This technique was optimized by using only a small piece of the telescope. Once the twinkle was removed, the light from the star itself was blocked using the team's coronograph, an instrument that selectively masks out the star. A novel "vortex coronagraph," invented by team member Dimitri Mawet of JPL, was used for this step. The final result was an image showing the light of three planets.

"The trick is to suppress the starlight without suppressing the planet light," said Serabyn.

The technique can be used to image the space lying just fractions of a degree from a star (about one degree divided by roughly 10,000). This is as close to the star as that achieved by Gemini and Keck -- telescopes that are about five and seven times larger, respectively.

Keeping telescopes small is critical for space missions. "This is the kind of technology that could let us image other Earths," said Wesley Traub, the chief scientist for NASA's Exoplanet Exploration Program at JPL. "We are on our way toward getting a picture of another pale blue dot in space."

JPL is a partner with the California Institute of Technology in Pasadena in the Palomar Observatory. Caltech manages JPL for NASA. More information about exoplanets and NASA's planet-finding program is at http://planetquest.jpl.nasa.gov . More information about the Palomar Observatory is at http://www.astro.caltech.edu/palomar/ .

New Exoplanets

Yesterday at the winter meeting of the American Astronomical Association the team from the Kepler mission announced the discovery of five new exoplanets. Palomar's 200-inch Hale Telescope was one of several ground-based telescopes that helped to confirm the discoveries. These discoveries came from just the first few weeks of observations and many, many more exoplanets are expected as the mission continues.

In addition to the five new exoplanets the team also announced the discovery of what might be a new class of astronomical object. Stay tuned as the science from this mission is just beginning.

This and That

Palomar Observatory is now back on its regular winter hours and open to visitors 9 am - 3 pm daily.


Astrobiology Magazine has named the discovery of exoplanet VB 10b, found using Palomar's Hale Telescope, as one of their Astrobiology Top 10 for the year.

Remember the 365 Days of Astronomy podcasts are continuing for 2010, but there still many open dates, even for the month of January.

Miller McCune magazine published an article on the dark-skies movement in Borrego Springs, CA: Stary, Stary Skies California desert town takes back the night, wins rare "Dark Sky" award.

A Companion for Alcor

The Big Dipper, isn't a constellation (technically it is an asterism), but it is one of the most famous groups of stars in the sky. Nestled within the handle of the Dipper are some famous stars. The middle star of the handle is called Mizar. Next to Mizar is another star that has often been used to test visual acuity--Alcor.


Can you spot the Big Dipper with Mizar and Alcor in this photo taken from the catwalk of the Hale Telescope? Click to embiggen and hopefully the stars will be easy to spot.

The close proximity of Alcor to Mizar make the stars great targets for casual evening stargazing. Pointing a small telescope at the pair gives a nice surprise as Mizar is revealed to be not one star, but two. Further spectroscopic studies have revealed that Mizar is made up of more stars that are unseen because they too close to each other to be resolved as individual stars. But what of Alcor?

You may remember Project 1640, one of new instruments commissioned for the 200-inch telescope lat year. Project 1640 makes use of the Hale Telescope's adaptive optics system, which gives the Hale a view almost equal to what can be obtained from in space. The instrument also has the ability to block out the light of a star, allowing faint objects located next to a star to be seen. This technique should soon be revealing previously unseen exoplanets. The Hale, armed with Project 1640, was pointed at Alcor earlier this year and found that it isn't a single star. Alcor has a small stellar companion that hadn't been seen before.

What is it like? The companion, Alcor B, is a small, dim red dwarf star about one fourth the mass of our Sun.

Caption: Alcor is a star in the handle of the Big Dipper. This discovery image shows Alcor B, marked with the green arrow in the inset. Alcor B is a newly found red dwarf companion of Alcor. Project 1640 astronomers discovered the faint star by blocking out almost all of Alcor's light with a coronagraphic mask, the darker circular region in the middle of the image. Although the vast majority of Alcor’s light has been blocked out, a residual halo of speckles remains because of minute imperfections in the camera’s optics. The actual diameter of either of the stars far smaller than a pixel in this image. This residual glare is what makes finding faint companions of bright stars difficult.

Credit: Project 1640, American Museum of Natural History, Digital Universe Atlas

For those who are so inclined, here is a link to where you can find the scientific paper on the discovery. The press release is announcing the discovery is below. Note the nod to Galileo in both the press release and the scientific paper, making this a nice discovery for the International Year of Astronomy.

A Faint Star Orbiting the Big Dipper’s Alcor discovered

Project 1640 Uses a Novel Technique with Ties to Galileo to See the Unknown

Next time you spy the Big Dipper, keep in mind that there is another star invisibly (at least to the unaided eye) contributing to this constellation. According to a new paper published in The Astrophysical Journal, one of the stars that makes the bend in the ladle’s handle, Alcor, has a smaller red dwarf companion. Newly discovered Alcor B orbits its larger sibling, caught in the act with an innovative technique called “common parallactic motion” by members of Project 1640, an international collaborative team that includes astrophysicists at the American Museum of Natural History, the University of Cambridge’s Institute of Astronomy, the California Institute of Technology, and NASA’s Jet Propulsion Laboratory.

“We used a brand new technique for determining that an object orbits a nearby star, a technique that’s a nice nod to Galileo,” says Ben R. Oppenheimer, Curator and Professor in the Department of Astrophysics at the Museum. “Galileo showed tremendous foresight. Four hundred years ago, he realized that if Copernicus was right—that the Earth orbits the Sun—they could show it by observing the “parallactic motion” of the nearest stars. Incredibly, Galileo tried to use Alcor to see it but didn’t have the necessary precision.” If Galileo had been able to see change over time in Alcor’s position, he would have had conclusive evidence that Copernicus was right. “Parallactic motion” is the way nearby stars appear to move in an annual, repeatable pattern relative to much more distant stars, simply because the observer on Earth is circling the Sun and seeing these stars from different places over the year.

Alcor is a relatively young star twice the mass of the Sun. Stars this massive are relatively rare (less than a few percent of all stars), short-lived, and bright. Alcor and its cousins in the Big Dipper formed from the same cloud of matter about 500 million years ago, something unusual for a constellation since most of these patterns in the sky are composed of unrelated stars. Alcor shares a position in the Big Dipper with another star, Mizar. In fact, both stars were used as a common test of eyesight—being able to distinguish “the rider from the horse”—among ancient people. One of Galileo’s colleagues observed that Mizar itself is actually a double, the first binary star system resolved by a telescope. Many years later, the two components Mizar A and B were themselves determined each to be tightly orbiting binaries, altogether forming a quadruple system.

Now, Alcor, which is near the four stars of the Mizar system, also has a companion. This March, members of Project 1640 attached their coronagraph and adaptive optics to the 200-inch Hale Telescope at the Palomar Observatory in California and pointed to Alcor. “Right away I spotted a faint point of light next to the star,” says Neil Zimmerman, a graduate student at Columbia University who is doing his PhD dissertation at the Museum. “No one had reported this object before, and it was very close to Alcor, so we realized it was probably an unknown companion star.”

The team retuned a few months later and re-imaged the star, hoping to prove that the two stars are companions by mapping the tiny movement of both in relation to very distant background stars as the Earth moves around the Sun, parallactic motion. If the proposed companion were just a background star, it wouldn’t move along with Alcor.

“We didn’t have to wait a whole year to get the results,” says Oppenheimer. “We went back 103 days later and found the companion had the same motion as Alcor. Our technique is powerful and much faster than the usual way of confirming that objects in the sky are physically related.” The more typical method involves observing the pair of objects over much longer periods of time, even years, to show that the two are moving through space together.

Alcor and its newly found, smaller companion, Alcor B, are both about 80 light-years away and orbit each other every 90 years or more. Over one year, the Alcor pair moves in an ellipse on the sky about 0.08 arc seconds in width because of the Earth’s orbit around the Sun. This amount of motion, 0.08 arcsec, is about 1000 times smaller than the eye can discern, and a fraction of this motion was easily measured by the Project 1640 scientists.

The team was also able to determine the color, brightness and even rough composition of Alcor B because the novel method of observation that Project 1640 uses records images at many different colors simultaneously. The team determined that Alcor B is a common type of M-dwarf star or red dwarf that is about 250 times the mass of Jupiter, or roughly a quarter of the mass of our Sun. The companion is much smaller and cooler than Alcor A.

“Red dwarfs are not commonly reported around the brighter higher mass type of star that Alcor is, but we have a hunch that they are actually fairly common,” says Oppenheimer. “This discovery shows that even the brightest and most familiar stars in the sky hold secrets we have yet to reveal.”

The team plans to use parallactic motion again in the future. “We hope to use the same technique to check that other objects we find like exoplanets are truly bound to their host stars,” says Zimmerman. “In fact, we anticipate other research groups hunting for exoplanets will also use this technique to speed up the discovery process.”

In addition to Zimmerman and Oppenheimer, authors include Anand Sivaramakrishnan and Douglas Brenner of the Astrophysics Department at the Museum; Sasha Hinkley, Lynne Hillenbrand, Charles Beichman, Justin Crepp, Antonin Bouchez and Richard Dekany of the California Institute of Technology; Ian Parry, David King, and Stephanie Hunt of the Institute of Astronomy at Cambridge University; Rémi Soummer of the Space Telescope Institute in Baltimore; and Gautam Vasisht, Rick Burruss, Michael Shao, Lewis Roberts, and Jennifer Roberts of the Jet Propulsion Laboratory at California Institute of Technology. Project 1640 is funded by the National Science Foundation.

Goodbye to Sleuth

From 2003 - 2007 the tiny, robotic 4-inch sleuth telescope spent its nights at Palomar Observatory hunting down exoplanets. The telescope was part of the Trans-Atlantic Exoplanet Survey (TrES), a network of three such telescope dedicated to looking for exoplantes that are seen to directly transit across the face of their parent star.

At the time the survey began, there was just one known transiting exoplanet. TrES added four more exoplanets to the list. Not bad for such little telescopes.

The project was set up by then Caltech postdoc David Charbonneau (now with Harvard) who returned to Palomar earlier this week to to retrieve his little telescope. Even though the telescope had already been out of service for almost two years it was a bittersweet moment. Nobody like to see a telescope retired. The good news is that Dr. Charbonneau is leaving behind a 10-inch telescope ("Sherlock") that was also used for the project. This telescope, which helped to remove false detections from the list of possible exoplanets, will eventually be used for our public outreach programs.

The enclosure that was occupied by Sleuth will be put back into use again. More on that later.

Still Inovating After All These Years

SPIE was at Palomar a couple of weeks ago to conduct some interviews. The first one, Palomar's 200-inch telescope: still innovating after 60 years of science, is now posted on their website. It is an interview with our Superintendent, Dan McKenna. In the interview Dan talks about the Observatory's mission and some new observing projects we have going on. I am biased, but it is cool stuff.

Palomar Planet VB10b makes APOD & Dedication Day!

You saw it here first, but VB10b, the latest exoplanet discovered at Palomar Observatory, is today's Astronomy Picture of the Day. Be sure to click on over, because APOD always has cool links for you to explore.

By the way, today is also the 61st anniversary of the dedication of the 200-inch Telescope. It was a magical day, but the real magic happens each and every clear night at Palomar as the Hale Telescope and the others here continue our mission of astronomical research as we turn starlight into knowledge.

Exoplanet in the News

Our announcement last week of the new exoplanet discovery has gotten pretty good press with coverage from Scientific American, National Geographic, Sky & Telescope, Astronomy Magazine, Space.com, Nature, Centauri Dreams, Bad Astronomy, the BBC, Science News and many more.

It is nice to see that this story has been getting around. Next week there will be another press release to look forward to. Stay tuned.

A New Exoplanet from an Old Technique

Back when I was a kid space exploration was flying high, astronauts were on the Moon, there were big plans for orbital cities and an astronomer had just announced the discovery of a system of planets orbiting a nearby star. It didn’t take much for my imagination to leap forward to my eventual trip into space. I was even sure that things would progress to the point where we would eventually be sending missions to explore the planets in orbit around Barnard’s Star. Alas, just about all of that has evaporated, even the planets.

Barnard’s Star is red dwarf star located just six light years from our solar system. Its small size and close proximity make it a great target to hunt for exoplanets. Back in the late 1960s astronomer Peter van de Kamp announced (see The Myserious Companions of Barnard's Star from Time Magazine's April 25, 1969 issue) the discovery of two planets in orbit about Barnard’s Star. B1, was slightly more massive than Jupiter and had an orbital period of 26 years and B2 was slightly less massive than Jupiter and had an orbital period of 12 years. All of this was pretty reasonable compared to our own solar system and life was good.

Peter Van de Kamp used a technique known as astrometry. The idea is to take very precise images of the star’s exact position relative to any background stars. As a planet orbits about the star its gravity will slightly pull the star toward the planet, making a change in its position. If all goes well a repeatable wobble, directly related to the orbital period of the planet will be detected.

van de Kamp knew that Barnard’s star was small, which was good because that makes it easier for a planet to deflect its position. He also knew that it was close, which was also good because it makes the tiny wobble easier to find. Unfortuately, what he didn’t know was that his technique was flawed. No other survey technique has been able to confirm his observations. Barnard’s Star apparently has no planets.

Planet hunters have not given up and new techniques have arisen. The number of known exoplanets now stands at almost 350. But what of van de Kamp’s method of astrometry? It was all but dead for many years, but two JPL astronomers resurrected it. For a little over a decade Steven Pravdo and Stuart Shaklan have been coming to Palomar to use their instrument called STEPS (STellar Planet Survey).


STEPS, seen above, is a large-format CCD camera that gets occasionally mounted at the Hale Telescope’s Cassegrain focus. The CCD has 4096 x 4096 pixels. The payoff of years of observing, an exoplanet discovery, is a difficult one to make. The elusive wobble that Peter van de Kamp thought he had found is small, just 1 milli-arcsecond in size -- that is the angle subtended by a human hair (about 50 microns wide) as seen from a distance of 30 miles!

I am happy to tell you that Pravdo and Shaklan have indeed found an exoplanet using this technique!


The tiny star known as VB 10 is located 20 light years away in the constellation Aquila and is now the smallest star known to have an exoplanet. The planet, VB 10b, is six times more massive than Jupiter, but just about the same size as Jupiter. Notice in the artwork above that the two are pretty close to being the same size.

VB 10b has a nine month orbital period and is just 30 million miles from its star, that puts it a little closer to its star than Mercury is to ours. See below for the comparison.

This is not Palomar's first exoplanet, but congratulations still go out to Steven Pravdo and Stuart Shaklan on their discovery and for mastering the astrometric method of planet hunting.

You can read more about their find from JPL (it even has a movie) here, or here from Bad Astronomy or even here from space.com.

Kepler Catches TRES-2

You remember TRES-2, don't you? Just take a good look at the star known as GSC 03549-02811 and you can't miss it. That's because TRES-2 is an exoplanet and every 2.47 it passes directly between its parent star (GSC 03549-02811) and us. As it does it produces a sort of mini eclipse known as a transit.

Above is some artwork showing a transiting exoplanet. Why artwork? Astronomers can not actually see the exoplanet, just the dimming of the star caused by the planet as it passes in front of its parent star. Click here to see a graphic of what I am talking about.

TRES-2 gets its unique name from being the 2nd planet discovered as a part of TrES, the Trans-atlantic Exoplanet Survey. The planet was found by this network of three small-aperture telescopes, one of which was based at Palomar. The network was made up of: Sleuth (Palomar Observatory, Southern California), the PSST (Lowell Observatory, Northern Arizona) and STARE (Observatorio del Teide, Canary Islands, Spain).

Transits are all the rage for finding exoplanets and NASA's Kepler mission is banking on the success of this technique. One of the things that makes TRES-2 so exciting is that it is located in the same part of the sky that Kepler will be staring at. They hope to find many, many exoplanets, including Earth-sized worlds (which TRES-2 certainly isn't). Since the Kepler team already knows that TRES-2 is there they can use it as sort of a calibrator for finding unknown exoplanets.

The team released their first images today and you can see TRES-2's parent star (GSC 03549-02811) in all its glory.

By the way the little 4-inch Sleuth telescope is no longer in operation on Palomar, but it had a good run in helping to discover several exoplanets.

Exoplanet Hunter to be Honored

Last week the National Science Foundation announced that former Caltech astronomer David Charbonneau will be awarded the Alan T. Waterman Award in May.

Dave has been a leader in the field of exoplanets and here at Palomar he established the now retired 4-inch Sleuth telescope which found a few exoplanets of its own.

Be sure to check his photo from National Geographic Magazine.

Sci Fi Science on TV

Look for Palomar Observatory on Sci Fi Science on Science Channel. If I recall correctly the topic of exoplanets will be discussed and you may be seeing the Palomar Testbed Interferometer, the Sleuth telescope and myself.

The show will air Sunday October 26 at 9:00PM Eastern and Pacific/ 8:00pm Central. As always it is a good idea to check your local listings.

Project 1640: installed

You may remember my New Instrument. New Planets? post from late June. Well, the time has finally come for Project 1640 to get installed on the 200-inch Hale Telescope.

Below is a shot from earlier today as the new instrument was brought into the Hale's Cassegrain cage and attached to the adaptive optics unit.

All seemed to go well and the unit is safely in place.

With any luck in a day or two I'll have a time-lapse movie for everyone to view of the installation.

Tonight begins the first of three engineering nights - that's time to make sure the instrument works and to prepare for future science operations.

New Instrument. New Planets?

Project 1640, a new instrument for the Hale Telescope has arrived. With this new instrument astronomers hope to actually photograph exoplanets--planets that orbit other stars.

The instrument was built by the American Museum of Natural History and the Institute of Astronomy at University of Cambridge. It has only just arrived at Palomar. Today's big event was to make sure that it would properly attach to the telescope and its adaptive optics system. Over the next week and a half the instrument will get fine tuned in preparation for first light.

The new instrument can be seen at left on its cart prior to its fitting test earlier today.

Once it is up and running it will use adaptive optics to correct for distortions in the atmosphere and then a coronagraph which will shield the bright light of a star allowing for the direct photography of an exoplanet. Lots more information is at the Project 1640 link above, but it is certainly worth the time to visit http://lyot.org/.

Stay tuned for updates after the instrument gets some telescope time.

Good Planets are Hard to Find

TEDI, the TripleSpec - Exoplanet Discovery Instrument saw "first light" on the 200-inch Hale Telescope last night.

The Hale is nearly 60 years old and observers are still building new instruments to keep this venerable telescope in the modern era. To the best of my knowledge TEDI is the first instrument fielded specifically for finding planets that orbit cool stars. It is in the commissioning phase now, but the observing program to come will survey the smallest dwarf stars - those classified as M, L and T.TEDI was created to work with Cornell's near-infrared Triple Spectrograph. The TripleSpec arrived at Palomar just last fall. TEDI was developed with the Cornell team and people from Space Sciences Lab at the University of California, Berkeley and Lawerence Livermore National Lab. Hunting for exoplanets isn't something new for Palomar. Little Sleuth has found several, including what is currently the largest known exoplanet, while the Palomar Testbed Interferometer is involved in a search of its own. The Lyot Project, coming to the 200" in the spring, will add the power of adaptive optics to the search.