How Do We Know What We Don’t Know About Asteroids?

What does guessing the number of jelly beans in a jar have to do with political polls and counting asteroids?  They all have something in common: all three use statistical samples to predict a result. In other words, without having to ask every single person in the country how they’ll vote, it’s possible to pick a group of people who we think are likely to be a good representation of everyone and just ask them how they’re going to vote. From this representative sample, we can predict what everyone else will do.

Similarly, we don’t have to count every single jelly bean in the jar to get a good estimate of how many there are. Instead, we can figure out about how big each bean is, and roughly how big the jar is, and from there, we can make a pretty solid guess about how many beans the jar holds.

When it comes to asteroids, those bits of rock, ice, and dust zooming around in our solar system, one of the first questions a lot of people ask is how many are there, and how do we know that? We certainly haven’t found all the asteroids yet, so how can we be sure how many there really are, and how many more are left to discover?

The Wide-field Infrared Survey Explorer (WISE) mission captured this infrared view of an Earth-orbiting satellite (green streak, lower right), the Main Belt Asteroid Regina (which appears as a string of orange dots, upper right), and the Triangulum Galaxy (center left), one of the closest galaxies to our own Milky Way. In this heat-sensitive infrared image, the shortest wavelengths are color-coded blue, and the longest are shown as red. Regina was detected by the WISE's mission asteroid-finding pipeline, known as NEOWISE. From its infrared signature, we can measure its size and the reflectivity of its surface. Regina is 47 km across, and its surface is as dark as black ink. It appears red in this image because it is much cooler than the stars, which are thousands of degrees. The string of red dots represents the multiple exposures of it that were collected by the WISE spacecraft. The satellite appears as a streak because it is much closer than the asteroid, so it appears to move much faster. Although the galaxy is moving incredibly fast, it is so far away that it appears stationary. Its blue stars are very hot, thousands of degrees, and the red regions highlight the cool, dusty locations where new stars are forming. Credit: NASA.

The Wide-field Infrared Survey Explorer (WISE) mission captured this infrared view of an Earth-orbiting satellite (green streak, lower right), the Main Belt Asteroid Regina (which appears as a string of orange dots, upper right), and the Triangulum Galaxy (center left), one of the closest galaxies to our own Milky Way. In this heat-sensitive infrared image, the shortest wavelengths are color-coded blue, and the longest are shown as red. Regina was detected by the WISE’s mission asteroid-finding pipeline, known as NEOWISE. From its infrared signature, we can measure its size and the reflectivity of its surface. Regina is 47 km across, and its surface is as dark as black ink. It appears red in this image because it is much cooler than the stars, which are thousands of degrees. The string of red dots represents the multiple exposures of it that were collected by the WISE spacecraft. The satellite appears as a streak because it is much closer than the asteroid, so it appears to move much faster. Although the galaxy is moving incredibly fast, it is so far away that it appears stationary. Its blue stars are very hot, thousands of degrees, and the red regions highlight the cool, dusty locations where new stars are forming. Credit: NASA.

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Astronomical molecules revealed by infrared light

Light can be thought as a collection of radiation of different wavelengths. Our eyes have evolved in such way that they are able to detect light of wavelengths within 390 and 700 nanometres (nm), wherein one nanometer corresponds to one meter divided into one billion equal parts. This is the so called visible light. The information carried on by this light are processed by our brains, and than we can interpret the world that we see. Besides visible light, radiation of many other wavelengths exist, which our eyes cannot detect, but instruments that we create can. Those radiation which are invisible for our eyes can still be very useful for a large range of human activities. For instance, X-ray (0.01nm – 10nm) is important in medicine, and microwaves (1 million nm – 1 billion nm) are important for heating up our food. These radiation are important in astronomy as well, since stars also emit different kinds of invisible radiation. Extremely valuable information about the Universe can be revealed by analyzing all kinds of radiation emitted by the astronomical objects. Here we are going to explore the so called infrared light – which wavelengths lay within the range between 700 nm and 1 million nm – and how it can help on the comprehension of the chemical properties of star forming regions.

Artist’s impression of a young star surrounded by a protoplanetary disc in which planets are forming. Credit: ESO/L. Calçada.

Artist’s impression of a young star surrounded by a protoplanetary disc in which planets are forming. Credit: ESO/L. Calçada.

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