Visit to an Asteroid

NASA to Launch New Science Mission to Asteroid 1999 RQ36

Well, it’s official. A new planetary science mission called OSIRIX-REx will be launched in 2016 to visit an asteroid in 2020, pluck up some samples from its surface, and return them to Earth. NASA  just made the announcement about this mission, which has the lengthy name “Origins-Spectral Interpretation-Resource Identification-Security-Regolith Explorer”, or OSIRIS-REx. It will be the first U.S. mission to carry samples from an asteroid back to Earth and studies of this asteroid will have far-reaching implications, not only in our understanding of their formation (and the information they carry about conditions in the early solar system), but also will help astronomers better predict the orbital paths of asteroids that come close to our planet.

Conceptual image of OSIRIS-REx. Credit: NASA/Goddard/University of Arizona

So, what can an asteroid tell us? These chunks of leftover debris from the solar system’s formation some 4.5 billion years ago, contain the original material from the solar nebula from which the Sun and planets formed. Study that material and you can learn a huge amount of information about conditions in the nebula at the time the solar system was born. Along with comets, which were formed largely in the outer reaches of the solar system, asteroids are essentially treasure caches of material that “remembers” what it was like back in the early epochs of solar system history.

Asteroid 1999 RQ 36 is about the size of five football fields and is very likely rich in carbon and other elements that are useful in the creation of life. Organic molecules have been found in meteorite and comet samples, indicating some of life’s ingredients can be created in space. Scientists want to see if they also are present on RQ36.

Aside from doing a little “gardening” on the asteroid’s surface, the mission will also measure something called the “Yarkovsky effect.”   It’s a small shove that the Sun’s radiation gives to an asteroid. The way it works is that an asteroid’s surface absorbs sunlight, just as Earth’s surface does. The asteroid’s surface then radiates that heat back out to space, and in the process, that gives a little “push” to the body.  Now, this wouldn’t ordinarily be of  much concern for asteroids that never get close to our planet. But, occasionally some do, and knowing the effect of the Sun’s warming on such a body helps astronomers predict their orbital paths (and possibly whether one could be a threat to our planet).

It’s interesting work because while we’ve studied most of the other planets and many of their moons, observations and visits to asteroids and comets are a bit rarer in planetary science.

Galaxies Are Like People

They Come in All Shapes and Sizes

Artist's concept of the Milky Way Galaxy. Credit: NASA JPL

You grew up in this galaxy.  It’s what astronomers call a “barred spiral” and if you were an alien living on a planet a galaxy with a “top down” view of the Milky Way, this is what the view would be.  The central area, called the “bulge” is filled with stars and, of course, our own supermassive black hole.  The bar of light extending out from the center is a sort of “transport” mechanism for gas and other materials toward the core. The spiral arms are where a lot of the latest star-forming (and star death) action is taking place.  Our planet is about 2/3 of the way out from the center, between a pair of spiral arms. We don’t live in the center of this stellar city, but more like in the outskirts where the action is a bit quieter. That’s good for us, since being too close to the center might not be good for our solar system’s health.

Astronomers are well aware that not all galaxies look like this. In fact, the Milky Way didn’t always look as it does now. It has evolved, just as all other galaxies have throughout the cosmos. To study the changes that galaxies go through, astronomers have categorized them by shape (their “morphology”) and their sizes, as well as other characteristics like the ages of their stars and the metal content they have.

A new, colorful collection of galaxy specimens has been released by NASA's Wide-field Infrared Survey Explorer, or WISE, mission. Image credit: NASA/JPL-Caltech/UCLA

NASA’s WISE mission (the Wide-field Infrared Survey Explorer), is studying distant galaxies and today has released images of an assort mix of colorful and shapely galaxies. Just as people come in all sizes and variations on the two-arms, two-legs, height and weight arrangements of our bodies, galaxies also exhibit a wide array of variations on the standard theme.

The new collection of nine galaxies shows off this diversity, with members of different sizes, colors and shapes. Infrared light from the galaxies, which we can’t see with our eyes, has been translated into visible-light colors that we can see. Blue colors show older populations of stars, while yellow indicates dusty areas where stars are forming.

This collage of WISE images shows everything from “grand design spirals,” with their elegant swirling arms, to so-called “flocculent” galaxies, which look more patchy and nebulous.  All these galaxies are close enough to us that WISE can see details of their structures. Some show sinuous arms and central bulges filled with packed-together stellar populations and possibly even central supermassive black holes.

Some of the galaxies are oriented toward us nearly face-on, such as Messier 83, and others are partly angled away from us, for example Messier 81. One galaxy, NGC 5907, is oriented completely edge-on, so that all we can see is its profile. The edge of its main galaxy disk appears pencil-thin, and its halo of surrounding stars is barely visible as a green glow above and below the disk.

The arms of the galaxies come in different shapes too. Messier 51 has arms that look like a spiral lollipop, while the arms of the flocculent galaxy NGC 2403 look choppy, perhaps more like layered frosting. Astronomers think that gravitational interactions with companion galaxies may lead to more well-defined spiral arms. One such companion can be seen near Messier 51 in blue. Some of the galaxies also have spokes, or spurs, that join the arms together, such as those in IC 342.

As astronomers scan the universe, they’ll be able to dig more deeply into the different galaxy shapes they see. Just as images of different people at different ages tell us about how humans are born, age, and die, images such as these give important clues about a galaxy’s evolutionary history and the stars it contains. Not only will this work help us understand the life stories of all galaxies, it contributes to a greater appreciation of our own Milky Way and the changes it went through that led to the creation of our own Sun and planets.