Reflected Glory

The nebula Messier 78 takes centre stage in this image taken with the Wide Field Imager on the MPG/ESO 2.2-metre telescope at the La Silla Observatory in Chile, while the stars powering the bright display take a backseat. The brilliant starlight ricochets off dust particles in the nebula, illuminating it with scattered blue light. Igor Chekalin was the overall winner of ESO’s Hidden Treasures 2010 astrophotography competition with his image of this stunning object.

Messier 78 is a fine example of a reflection nebula. The ultraviolet radiation from the stars that illuminate it is not intense enough to ionise the gas to make it glow — its dust particles simply reflect the starlight that falls on them. Despite this, Messier 78 can easily be observed with a small telescope, being one of the brightest reflection nebulae in the sky. It lies about 1350 light-years away in the constellation of Orion (The Hunter) and can be found northeast of the easternmost star of Orion’s belt.

This new image of Messier 78 from the MPG/ESO 2.2-metre telescope at the La Silla Observatory is based on data selected by Igor Chekalin in his winning entry to the Hidden Treasures competition [1].

The pale blue tint seen in the nebula in this picture is an accurate representation of its dominant colour. Blue hues are commonly seen in reflection nebulae because of the way the starlight is scattered by the tiny dust particles that they contain: the shorter wavelength of blue light is scattered more efficiently than the longer wavelength red light.

This image contains many other striking features apart from the glowing nebula. A thick band of obscuring dust stretches across the image from the upper left to the lower right, blocking the light from background stars. In the bottom right corner, many curious pink structures are also visible, which are created by jets of material being ejected from stars that have recently formed and are still buried deep in dust clouds.

Two bright stars, HD 38563A and HD 38563B, are the main powerhouses behind Messier 78. However, the nebula is home to many more stars, including a collection of about 45 low mass, young stars (less than 10 million years old) in which the cores are still too cool for hydrogen fusion to start, known as T Tauri stars. Studying T Tauri stars is important for understanding the early stages of star formation and how planetary systems are created.

Remarkably, this complex of nebulae has also changed significantly in the last ten years. In February 2004 the experienced amateur observer Jay McNeil took an image of this region with a 75 mm telescope and was surprised to see a bright nebula — the prominent fan shaped feature near the bottom of this picture — where nothing was seen on most earlier images. This object is now known as McNeil’s Nebula and it appears to be a highly variable reflection nebula around a young star.

This colour picture was created from many monochrome exposures taken through blue, yellow/green and red filters, supplemented by exposures through an H-alpha filter that shows light from glowing hydrogen gas. The total exposure times were 9, 9, 17.5 and 15.5 minutes per filter, respectively.
Notes

[1] Igor Chekalin from Russia uncovered the raw data for this image of Messier 78 in ESO’s archives in the competition Hidden Treasures (eso1102). He processed the raw data with great skill, claiming first prize in the contest for his final image (Flickr link). ESO’s team of in-house image processing experts then independently processed the raw data at full resolution to produce the image shown here.

Get Ready for a Solar-System Bonanza

Don't get me wrong: I would never suggest that NASA throttle back its efforts to explore the worlds around us. But I have to admit that, even for folks like me who follow space activities closely, things are getting a little crazy. Over the next several months, interplanetary exploration will rev up to a dizzying pace.

The first event occurred just a few days ago, when the twin STEREO spacecraft finally took up positions on opposite sides of the Sun. (We space junkies sometimes forget that the Sun is part of our solar system.) For the first time, solar scientists can monitor all of the Sun's disk at once — and that'll pay big dividends as solar activity ramps up in the months ahead.

An artist's portrayal of the Stardust spacecraft approaching Comet Tempel 1 on February 14, 2011.

Coming up fast is a return visit to Comet 9P/Tempel 1. You'll recall that this 5-by-3-mile iceberg was the target of NASA's Deep Impact mission on July 4, 2005. When a 815-pound (370-kg) projectile slammed into the comet's nucleus, it unleashed an unexpected fireworks display of gas and dust.

Since then Tempel 1 has made one complete trip around the Sun, and on February 14th it'll again be in the crosshairs (this time just with instruments) of the Stardust
spacecraft. This is a great example of how old spacecraft can do new tricks: Stardust completed its primary mission five years ago after zipping through the coma of Comet Wild 2 in early 2004 and dropping off a sample capsule when it swung past Earth. But the main spacecraft remained in solar orbit, and now it's posed to reconnoiter a second
comet.

(Officially, the mission's name is now Stardust-NeXT — that latter bit standing for "New Exploration of Tempel 1" — but it's just too much of a stretch for my taste.)

In the best of all worlds, Stardust's camera would record the crater made by Deep Impact's copper-cored cannonball. But even if the nucleus has rotated it from view, there's still plenty to look at. The nucleus of Tempel 1 appears to have multiple layers and bizarre flows. Can a mountain-size blob of ice and dirt be geologically active? We'll have more answers to that question very soon.

There's no letup in the pace of solar-system exploration once Stardust has its hi-and-bye. In fact, NASA officials
have dubbed 2011 the "Year of the Solar System." Well, truth be told, in their minds YSS began last October, when Deep Impact visited its second comet, 103P/Hartley 2, and it won't end until August 2012, when the not-even-launched-yet rover Curiosity (a.k.a. Mars Science Laboratory) reaches Mars.

Whatever. Here's a rundown of the other interplanetary headlines you can expect to see in the coming months:

March 18: After three warm-up flybys, NASA's Messenger
spacecraft will fire its braking rocket and slip into a looping polar
orbit around Mercury that comes within 125 miles (200 km) of its
surface. Equipped with seven very capable cameras, spectrometers, and
other instruments, Messenger has already made a trove of new
discoveries about the innermost planet. But the real science
breakthroughs (such as its interior structure) will come after the
orbiter has made long-term observations. Messenger is a contraction of
"Mercury Surface, Space Environment, Geochemistry, and Ranging."

July 16:
The Dawn spacecraft will reach 4 Vesta, which is hands down the
asteroid belt's most amazing chunk of rock: it's thought to have an
iron–nickel core, a rocky olivine mantle, a crust, lava flows, and a
giant crater. The spacecraft has been almost gliding toward Vesta using
ion-fueled thrusters, and it will remain in orbit for a year before
easing away and setting course for 1 Ceres. (Remarkably, Dawn isn't an
acronym and doesn't stand for anything.) This mission's website is here, and I highly recommend the "Dawn Journal" written by chief engineer Marc Rayman.

August 5: The launch date for NASA's ambitious Juno
spacecraft. This is the first outer-planet-bound spacecraft to use
solar-cell arrays, rather than plutonium power packs, to generate
electricity. When it reaches Jupiter in 2016, Juno is to slip into a
looping polar orbit that will both subject it to dangerously high
radiation levels and, its science team hopes, answer key questions
about the planet's composition, its interior structure, and from those
how our solar system formed. Also not an acronym, Juno is named for the
jealous god-sister-wife of Jupiter in Roman mythology.

September 8: Lunar scientists will look on expectantly as the twin GRAIL
spacecraft rocket skyward from Cape Canaveral, Florida. The Gravity
Recovery and Interior Laboratory mission intends to fly these craft in
tandem just 30 miles (50 km) above the lunar surface. By carefully
tracking how the Moon's gravity alters the crafts' orbital motion,
scientists hope to map the Moon's gravity field with unprecedented
detail and, using that, derive the detailed structure of the lunar
interior from crust to core.

November 8: If everything comes together in time, the Russian Space Agency plans to launch its problematic Phobos-Grunt mission. (Grunt is Russian for "ground".) Talk about a checkered history!
Conceived in 1996 to land on the larger of Mars's two satellites and
return a sample to Earth, this spacecraft has had more transformations
than Cher at the Academy Awards! In its latest configuration, the
spacecraft will carry a passenger, the Chinese-built spacecraft Yinghou
1, which will detach from Phobos-Grunt and orbit Mars for up to a year.
Plans still call for the main spacecraft to land on Phobos, scoop up
several samples totaling a total of 3 to 5½ ounces (85 to 160 g), and
return them to Earth by early 2013.

November 25: Another troubled mission, Mars Science Laboratory,
will begin its flight to Mars. The primary scientific objective is
straightforward: assess whether the Red Planet ever had an environment
conducive to life — or still does. But MSL, renamed Curiosity after a Disney-inspired contest in 2009, has had a world of trouble getting to the launch pad. The beefy 1-ton lander should have already reached Mars, but development problems caused a two-year launch delay and ballooned its price tag to $2½ billion.

All these dates are subject to change, so to keep up to date I recommend that you check Ron Baalke's comprehensive Space Calendar for the latest schedules.

Earth-Size Planet Candidates Found in Habitable Zone

PASADENA, Calif. -- NASA's Kepler mission has discovered its first Earth-size planet candidates and its first candidates in the habitable zone, a region where liquid water could exist on a planet's surface. Five of the potential planets are near Earth-size and orbit in the habitable zone of smaller, cooler stars than our sun.

Candidates require follow-up observations to verify they are actual planets. Kepler also found six confirmed planets orbiting a sun-like star, Kepler-11. This is the largest group of transiting planets orbiting a single star yet discovered outside our solar system.

"In one generation we have gone from extraterrestrial planets being a mainstay of science fiction, to the present, where Kepler has helped turn science fiction into today's reality," said NASA Administrator Charles Bolden. "These discoveries underscore the importance of NASA's science missions, which consistently increase understanding of our place in the cosmos."

The discoveries are part of several hundred new planet candidates identified in new Kepler mission science data, released on Tuesday, Feb. 1. The findings increase the number of planet candidates identified by Kepler to-date to 1,235. Of these, 68 are approximately Earth-size; 288 are super-Earth-size; 662 are Neptune-size; 165 are the size of Jupiter and 19 are larger than Jupiter. Of the 54 new planet candidates found in the habitable zone, five are near Earth-sized. The remaining 49 habitable zone candidates range from super-Earth size -- up to twice the size of Earth -- to larger than Jupiter.

The findings are based on the results of observations conducted May 12 to Sept. 17, 2009, of more than 156,000 stars in Kepler's field of view, which covers approximately one four-hundredth of the sky.

"The fact that we've found so many planet candidates in such a tiny fraction of the sky suggests there are countless planets orbiting sun-like stars in our galaxy," said William Borucki of NASA's Ames Research Center in Moffett Field, Calif., the mission's science principal investigator. "We went from zero to 68 Earth-sized planet candidates and zero to 54 candidates in the habitable zone, some of which could have moons with liquid water."

Among the stars with planetary candidates, 170 show evidence of multiple planetary candidates. Kepler-11, located approximately 2,000 light years from Earth, is the most tightly packed planetary system yet discovered. All six of its confirmed planets have orbits smaller than Venus, and five of the six have orbits smaller than Mercury's. The only other star with more than one confirmed transiting planet is Kepler-9, which has three. The Kepler-11 findings will be published in the Feb. 3 issue of the journal Nature.

"Kepler-11 is a remarkable system whose architecture and dynamics provide clues about its formation," said Jack Lissauer, a planetary scientist and Kepler science team member at Ames. "These six planets are mixtures of rock and gases, possibly including water. The rocky material accounts for most of the planets' mass, while the gas takes up most of their volume. By measuring the sizes and masses of the five inner planets, we determined they are among the lowest-mass confirmed planets beyond our solar system."

All of the planets orbiting Kepler-11 are larger than Earth, with the largest ones being comparable in size to Uranus and Neptune. The innermost planet, Kepler-11b, is 10 times closer to its star than Earth is to the sun. Moving outward, the other planets are Kepler-11c, Kepler-11d, Kepler-11e, Kepler-11f, and the outermost planet, Kepler-11g, which is half as far from its star as Earth is from the sun.

The planets Kepler-11d, Kepler-11e and Kepler-11f have a significant amount of light gas, which indicates that they formed within a few million years of the system's formation.

"The historic milestones Kepler makes with each new discovery will determine the course of every exoplanet mission to follow," said Douglas Hudgins, Kepler program scientist at NASA Headquarters in Washington.

Kepler, a space telescope, looks for planet signatures by measuring tiny decreases in the brightness of stars caused by planets crossing in front of them. This is known as a transit. Since transits of planets in the habitable zone of sun-like stars occur about once a year and require three transits for verification, it is expected to take three years to locate and verify Earth-size planets orbiting sun-like stars.

The Kepler science team uses ground-based telescopes and NASA's Spitzer Space Telescope to review observations on planetary candidates and other objects of interest the spacecraft finds. The star field that Kepler observes in the constellations Cygnus and Lyra can only be seen from ground-based observatories in spring through early fall. The data from these other observations help determine which candidates can be validated as planets.

Ames manages Kepler's ground system development, mission operations and science data analysis. NASA's Jet Propulsion Laboratory in Pasadena, Calif., managed Kepler mission development. Ball Aerospace & Technologies Corp. in Boulder, Colo., developed the Kepler flight system and supports mission operations with the Laboratory for Atmospheric and Space Physics at the University of Colorado in Boulder. The Space Telescope Science Institute in Baltimore archives, hosts and distributes the Kepler science data. Kepler is NASA's 10th Discovery Mission and is funded by NASA's Science Mission Directorate at the agency's headquarters. JPL is a division of the California Institute of Technology in Pasadena.