Looking for New Light

Jun 19, 2008

In many ways, astronomers are in the dark about asteroids. In the dark depths of the Kuiper Asteroid Belt beyond Neptune's orbit, and even in the nearby Main Belt between Jupiter and Mars, most asteroids are too small to reflect back enough sunlight to be seen by our telescopes. But as cosmic rays travel through our solar system, they may strike a glancing blow off the surface of an asteroid, producing gamma rays (short wavelength light waves). Researchers now report that they can use this gamma ray radiation to infer the number of small asteroids in different groups of small solar system bodies. However, they will have to wait to test their ideas until the new Gamma-ray Large Area Space Telescope (GLAST), launched last week by NASA, returns data.

The paper detailing this new technique will be published by researchers from the Kavli Institute for Particle Astrophysics and Cosmology (KIPAC) and the Santa Cruz Institute for Particle Physics (SCIPP) at U.C. Santa Cruz in the July 10 issue of The Astrophysical Journal.

Although GLAST's sensitivity won't be high enough for the researchers to see the outline of any individual asteroids, it will be able to detect an overall glow of gamma-ray light from large ensembles of these small bodies. The more light detected by GLAST, the more asteroids must exist in that area. To determine the relationship between the brightness of the observed gamma rays and the number of asteroids in a given area, the researchers used the gamma-ray emissions from the moon as a "standard candle" to create a scale. Researchers compared the gamma ray emissions from the moon with its size to create a scale for determining the sizes of unseen asteroids based on the gamma rays they emit.

Knowing the densities of groups of asteroids in our solar system could yield a great deal of information for astronomers. Being able to compare the difference in the asteroid population densities of the Main Asteroid Belt and the Kuiper Asteroid Belt could support or oppose the theory that the Main Belt has had a more violent, collision-filled past than the icy Kuiper Belt. The size distribution of the smallest bodies in our solar system can tell us how the largest bodies (which later became planets) grew in their early stages; and if we can better understand the history of the formation of the solar system, we can apply it to other planetary systems.

This new information will assist astronomers looking at gamma-ray sources toward the Galactic Center as well as outside of the Milky Way. The Galactic Center contains a web of overlapping gamma-ray sources which are difficult to discern from each other and one of the favored places to search for elusive dark matter. The orbital plane of our solar system (the ecliptic) is projected across the Galactic Center, so we cannot look to the Galactic Center without looking through a collection of asteroids. Understanding each source of gamma rays is important in untangling the web.

The paper's authors, Igor Moskalenko (Stanford/KIPAC), Troy Porter (SCIPP), Seth Digel (SLAC/KIPAC), Peter Michelson (Stanford/KIPAC) and Jonathan Ormes (U. Denver and KIPAC), theorize that this measurement will be particularly useful for planetary scientists, the cosmic-ray community and those who search for clues of new physics, including signatures of dark matter, in the Galactic Center and in the unresolved emissions from outside the Galaxy.

Source: Stanford Linear Accelerator Center

Explore further: Astronomers find 'cousin' planets around twin stars

add to favorites email to friend print save as pdf

Related Stories

Dawn spacecraft fills out its Ceres dance card

Dec 04, 2013

(Phys.org) —It's going to be a ball when NASA's Dawn spacecraft finally arrives at the dwarf planet Ceres, and mission managers have now inked in the schedule on Dawn's dance card.

Researcher helping solve moon's water puzzles

Nov 15, 2013

One of the things Dr. Richard Miller thinks is coolest about working as part of a team investigating the origin and mapping of water on the lunar poles is that he can look up at night or when the moon rises ...

Spitzer telescope celebrates ten years in space

Aug 23, 2013

(Phys.org) —Ten years after a Delta II rocket launched NASA's Spitzer Space Telescope, lighting up the night sky over Cape Canaveral, Fla., the fourth of the agency's four Great Observatories continues ...

NASA's Spitzer observes gas emission from comet ISON

Jul 24, 2013

Astronomers using NASA's Spitzer Space Telescope have observed what most likely are strong carbon dioxide emissions from Comet ISON ahead of its anticipated pass through the inner solar system later this ...

Astronomical pranks of April fools' past

Apr 01, 2013

The first day of April is always a traditional time for pranks and puns, and astronomers and scientists aren't above an April Fools' Day shenanigan or two. Hey, I gotta admit, as a freelance science journalist, ...

Recommended for you

How small can galaxies be?

Sep 29, 2014

Yesterday I talked about just how small a star can be, so today let's explore just how small a galaxy can be. Our Milky Way galaxy is about 100,000 light years across, and contains about 200 billion stars. Th ...

The coolest stars

Sep 29, 2014

One way that stars are categorized is by temperature. Since the temperature of a star can determine its visual color, this category scheme is known as spectral type. The main categories of spectral type are ...

Simulations reveal an unusual death for ancient stars

Sep 29, 2014

(Phys.org) —Certain primordial stars—those 55,000 and 56,000 times the mass of our Sun, or solar masses—may have died unusually. In death, these objects—among the Universe's first-generation of stars—would ...

User comments : 0