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Archive: March 2012

Hubble Planet Discovery Clouded by Spitzer

March 20, 2012 by Frank Summers
A white box indicates Fomalhaut b's suspected location (top). A magnified view of the planet in question shows different positions in its orbit (bottom).

A white box indicates Fomalhaut b's suspected location (top). A magnified view of the planet in question shows different positions in its orbit (bottom).

One of Hubble’s most celebrated discoveries is the November 2008 announcement of the first visible-light image of a planet orbiting another star. Along with several infrared observations announced by other observatories, that month marked the historic beginning of direct detections of extrasolar planets. Previous discoveries were indirect, deduced from the way the gravity, size, or motion of the planet affects the light from its host (or another) star. Since then, we’ve also been able to see infrared images of a few planets in other solar systems.

Hubble’s discovery, however, has been literally clouded from the start. The star Fomalhaut is 25 light-years away from Earth. The planet, dubbed “Fomalhaut b,” has an orbit more than 100 times larger than Earth’s orbit, and a size estimated to be about three times the mass of Jupiter. Considering the star’s brightness and distance, as well as the planet’s orbit and size, the object Hubble sees is too bright to be just the planet. The explanation has been that a huge ring of ice and dust around the planet is reflecting the extra starlight.

Observers using the Spitzer Space Telescope have recently questioned that explanation. As reported by Universe Today, a paper will appear in the “Astrophysicial Journal” that argues a better interpretation of the image is a “transient or semi-transient dust cloud.” This conclusion is based on infrared observations that fail to show the expected emission from a planet. Because planets are brighter at infrared wavelengths, the astronomers concluded that the visible-light observation is only from dust and not from a planet. While the gravitational argument for a planet remains solid, the research team found that the observed light source is “highly unlikely” to be a giant planet.

As one might expect, the original researchers disagree with these findings. They considered the dust cloud idea, but ruled it out. In their opinion, the resolution and sensitivity of Spitzer is too low to warrant such conclusions, and their postulated ring around the planet fits with the infrared observations.

One could promote this as the NASA Great Observatories in a scientific smackdown. Hubble punches with a planet. Spitzer counterattacks with a dust cloud. It’s an astronomical battle royale for extrasolar supremacy! But that would be silly.

This discussion is just the natural progress of science. Results, especially the really significant ones, must be checked and re-checked by many astronomers at many observatories before they become fully accepted. The original paper clearly identified the discrepancy of the extra light observed. The follow-up paper does a great service for everyone by providing more data to examine. Neither explanation is completely convincing at this time.

Eventually, more data will reveal what is truly being observed. In particular, the James Webb Space Telescope has the resolution of Hubble in the infrared wavelengths of Spitzer. JWST is slated for launch in 2018, and its observations should be able to distinguish between the two hypotheses. Or, more dramatically, JWST will be the ultimate referee of this cosmic clash of telescopic titans.

Taming the Data

March 12, 2012 by Alberto Conti
Artist's concept of the Galaxy Evolution Explorer (GALEX)

Artist's concept of the Galaxy Evolution Explorer (GALEX)

My name is Alberto Conti and I am an astrophysicist and the James Webb Space Telescope (JWST) Innovation Scientist at the Space Telescope Science Institute (STScI). I’ve been at STScI since 2003.

I am going to use these posts to tell you a little bit about my interests, what inspires me and makes me come to work daily. In doing so, I will try to underscore how science in general, and astronomy in particular, has changed over the course of my lifetime in ways that still amaze me.

I came to STScI to contribute to the development of the archive for the Galaxy Evolution Explorer (GALEX) mission. As a space mission, GALEX was unique in many ways. GALEX brought us the first detailed look at the entire sky in ultraviolet light, a range of radiation just above the shortest wavelengths visible to the human eye. Led by the California Institute of Technology, GALEX conducted several first-of-a-kind surveys, contributing significantly to our understanding of the processes that give raise to galaxy formation and evolution. One of GALEX’s main goals was to analyze ultraviolet light from millions of distant galaxies, thereby providing key evidence for the history of star formation over 10 billion years of cosmic history — or about 70 percent of the life of our universe.

All data collected by GALEX is stored at STScI in Multimission Archive (MAST), which is NASA’s optical and ultraviolet data archive. MAST’s primary focus is to support the astronomical community by providing access tools to sets of data, or “datasets,” in the optical, ultraviolet, and near-infrared parts of the spectrum. MAST currently hosts data for over 20 missions, including the Hubble Space Telescope, the Kepler terrestrial planet finder telescope, and GALEX.

I have always been fascinated with how astronomical data is collected, stored, retrieved, visualized, and used to understand the properties of our universe or discover new, exciting ones. Over the past 25 years, astronomers have become much more efficient at collecting photons from distant galaxies with larger mirrors in space and on the ground. However, our ability to build larger telescopes has been outshined by the exponential growth of detectors. Thanks to advances in detector technology, a relatively small telescope like GALEX, for instance, was able to collect data on over 200 million ultraviolet sources.

As a result, astronomical data doubles every two years or so, and profound changes have occurred in the astronomical community as a result. While I had worked with moderately large datasets during my postdoctoral work at the University of Pittsburgh, GALEX was where my love (most would say obsession) for data really began.

Storing information on details such as brightness, size, distance, color and many, many other items for over 200 million GALEX sources required detailed planning. Imagine a spreadsheet with more than 200 million rows and 300 columns, and you’ll have an idea of the task at hand. Developing the tools to search, retrieve and visualize this data was only possible with the dedicated work of the whole MAST GALEX team. I look back at my time on GALEX as a very exciting part of my life. It seemed that our team was making data discovery possible, enabling the mining of millions of objects in a matter of seconds.

It was during this time that I learned about databases, data mining technologies, data visualization techniques, and the importance of preserving the integrity of the data for the community. Many of the lessons learned during this time still guide my judgment when thinking about the next generation data archives for JWST. I’ll elaborate on this in my future posts.

Astronomy is an elegant science because each instrument we use to reveal the nature of our universe is nothing but a small piece of a larger puzzle we are all working on. This is true for GALEX. As a mission it would not have been as successful if it were not for its surveying capabilities, which represent a great complement to other space-based missions such as the Hubble Space Telescope and the Far Ultraviolet Spectroscopic Explorer, but also for ground-based surveys like the Sloan Digital Sky Survey at optical wavelengths.

I use GALEX data to this day looking for transient object (object whose properties change over time), hot white dwarfs, and quasars in a long-standing collaboration with Johns Hopkins University astronomer Luciana Bianchi. I feel very privileged to be able to work in field so intellectually and professionally rewarding, but mostly I feel humbled to have the teammates I have, starting with my GALEX friends.

More about me:
Wikipedia: Alberto Conti
AlbertoConti.com

We Live in a Compulsive Universe

March 6, 2012 by Ray Villard
An impression of how common planets are around the stars in the Milky Way

An impression of how common planets are around the stars in the Milky Way

There is a “big bang” going on in the search for planets outside of our solar system.

Nearly 2,500 have been discovered so far. And galactic survey estimates have skyrocketed to 100 billion. That’s one planet for every person who has ever lived on the Earth.

Many of the discoveries have come from NASA’s Kepler space observatory. Kepler’s ongoing planet discoveries have overwhelmed the astronomy community.

Gravitational lensing surveys, which look for the distortion of light by an invisible foreground planet, have lead us to the conclusion that planets equal or outnumber the stars in our Milky Way galaxy. This means that within 50 light-years of Earth there could be several dozen habitable planets.

Unlike the Kepler planets, which are very far away, these nearby worlds will be ripe for further scrutiny by the Hubble Space Telescope and its successor, the James Webb Space Telescope. Hubble and Webb will be able to study the structure and chemical content of these planets’ atmospheres. If they have oceans, Webb should be able to detect them.

Kepler’s jaw-dropping observations show that the types of planets and planetary systems out there are so varied that just about anything is possible. The far-flung worlds certainly do not fit our textbook definition of our solar system. Our neighborhood is beginning to look like the oddball.

“Nature must like to form planets because it’s forming them in places that are kind of difficult to do,” says William Welsh of San Diego State University.

If you can imagine it, it exists somewhere, adds Virginia Trimble of the University of California at Irvine. “Exoplanet discoveries have shown us that if it isn’t forbidden by the laws of thermodynamics and Newtonian physics, then it is compulsive.”

The idea of a compulsive universe is as old as Greek philosophy. “There are infinite worlds both like and unlike this world of ours . . .we must believe that in all worlds there are living creatures . . .” wrote Epicurus in 200 B.C.

Galileo’s contemporary, Giordano Bruno, correctly predicted that planets orbiting other stars were too faint to be seen by the newly invented telescope.

But just three decades ago notion of the planets around other stars was still dismissed by some astronomers as unscientifically presumptive. A colleague of mine was almost fired from his planetarium job by an astronomy professor because he wrote a program script that speculated about visiting worlds around other stars. (No doubt the professor was no fan of the “Star Trek” TV series.)

Even in 1980, estimates for the chances for planet around stars ranged from zero to 100 percent.

Things started to shift with discoveries in the 1990s. In 1995, Hubble captured images of the long-hypothesized, planet-forming dust disks around newborn stars, and astronomers found a Jupiter-sized planet orbiting the Sun-like star 51 Pegasi.

The giant planet orbits its star much closer that Mercury does to our Sun, the first hint that the possibilities for exoplanets characteristics might outstrip our imaginations.

At first the planet’s strange orbit seemed like a fluke. It was just some extremely odd happenstance in nature that a giant planet would wind up so close to its star. We expected to find more solar systems like ours, in which the giant planets reside farther away from their stars, and the small, rocky planets hover closer to the center.

But within a decade astronomers were estimating there are nearly 10 billion of these “hot Jupiters” across the galaxy.

Kepler and other searches have now shown that planets can orbit binary stars, that they can whip around their star in very eccentric orbits, and that planets can have the anemic density of Styrofoam or be tougher than solid steel.

Still, there are hardcore skeptics dismissing the possibility of extraterrestrial life on these worlds, even in light of our planet bonanza.

“Extrasolar systems are far more diverse than we expected, and that means very few are likely to support life,” insists Howard Smith of the Harvard Smithsonian Center for Astrophysics. Smith believes that we are the only intelligent life in the universe. But are we really the best that nature can do?

Radio astronomer Seth Shostak, on the other hand, estimates that there are at least 10 trillion trillion Earth-like planets in the entire universe. “You would have to believe in miracles if E.T. did not exist,” he asserts.

I agree with Shostak. Anything is possible in a compulsive universe.

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