FAQ

Frequently Asked Questions

Send us your questions through the Talk page! We'll pick the most frequently asked ones and answer them here.

Did you find a super interesting object? Consider filling out our variable form! This form helps us find particularly interesting objects in addition to the data we collect about classifications.

Table of Contents

Why Are We Called "Exoasteroids"?

Exoasteroids is the title of this citizen science project because we aim to detect asteroids outside our solar system, mainly those that impact white dwarfs. These exoasteroids provide valuable insights into the formation and composition of other planetary systems in the universe, they may even have ingredients for life in other solar systems. The study of exoasteroids is part of the broader field of exoplanetary science, which investigates the properties and characteristics of planets, moons, and other celestial bodies outside our solar system.

What is Citizen Science?

Citizen science is a form of scientific collaboration and communication between scientists and volunteers around the globe. NASA has pushed for citizen science to become a larger part of the scientific community as a result of the talent of everyone from around the world being vital for the next generation of astronomy. Exoasteroids requires no prior experience and welcomes participants of any background. Any training required for this project will be provided here or in the flipbooks in this project.

Questions About Objects in Space

What is an Asteroid?

An asteroid is a small rocky body that orbits the Sun, mostly found in a region called the asteroid belt between Mars and Jupiter. They are leftover building materials from the formation of our solar system. During the formation of the solar system, impacting asteroids is what formed planets like Mercury, Venus, Earth, and Mars. Unlike planets, asteroids are much smaller and don't have atmospheres. Some are only a few feet across, while others can be hundreds of miles wide. As a result of the small size of these asteroids they take decades to centuries to complete one orbit around the Sun.


(Credit: NASA/Asteroids)

What is an "Exoasteroid"?

An exoasteroid is an asteroid that exists outside our solar system, orbiting around a different star than our own. Just like the asteroids we have in our own solar system, these exoasteroids are made of rocks and metal. Scientists have started to discover exoasteroids by observing variability in the atmospheres of stars, which is caused by the exoasteroid impacting the star.

What is a Comet?

A comet is a chunk of ice, dust, and rocky material that orbits the Sun, very similar to asteroids. When a comet gets close to the Sun, it heats up and releases gas and dust, creating a tail pointing toward the Sun called a coma. Comets come from two main regions in our solar system. The closest region to Earth is the Kuiper Belt which is beyond Neptune. The second region comets are found is in the Oort Cloud which is a loose gathering of comets and asteroids on the very edge of the solar system.

What Are Circumstellar Disks and Debris Disks?

Circumstellar disks are rings of gas, dust, and other material that surround a young star. These disks are the birthplaces of planets, moons, and other objects in a solar system. As the material in the disk collides and sticks together, it can form larger bodies over millions of years. Debris disks are a type of circumstellar disk that is mainly made up of dust and small rocks, usually left over from the formation of planets.

What is a White Dwarf?

A white dwarf is a type of "stellar corpse" of a main-sequence star. These objects are incredibly small, roughly the size of Earth. After a normal star uses up all of its fuel the star explodes and the core collapses into what becomes the white dwarf. Although they no longer undergo nuclear fusion, which keeps stars like the Sun alive, white dwarfs shine for billions of years making them one of the last objects to exist in the universe.

What is a Main Sequence Star?

A main sequence star is a normal star as when you learned in school, they undergo nuclear fusion to stay bright and win against gravity, which goes on for billions of years. For example, the Sun is a main sequence star that is classified as a G2. Main Sequence stars have different names based on their mass and temperature, these names are called spectral types and are classified as: O, B, A, F, G, K, M (where O is the hottest and M is the coldest). Most of the stars we see in the night sky are in the main sequence phase.


(Credit: ESO)

What is a Variable Star?

A variable star is a star whose brightness changes over time. This variation can happen for different reasons: the star itself changes in size and temperature, a planet or another star can move in front of it, or material is impacting the star. Some variable stars change brightness regularly, while others do so irregularly. In Exoasteroids we are looking for material, such as dust and exoasteroids, impacting the star that changes the brightness irregularly with time. Seen below is an example variable white dwarf seen by the Exoasteroid flipbook.

Questions About Flipbooks

What is an "Optical Ghost"?

An "Optical Ghost" refers to a false object that appears in an observation due to reflections or scattering of light within the telescope. They can be seen as orange and will be varing in brightness, and therefore show up as fake variable white dwarfs. One example of an optical ghost in the WISE data is shown below:

What is a "Diffraction Spike"?

A "Diffraction Spike" is light that enters the WISE telescope, the support beams which hold the secondary mirror cause light to be diffracted. They will appear around bright stars as spikey components of the bright star itself and can be misinterpreted as variability in the white dwarf. One example of a diffraction spike is shown below:

What is a "Crowded Field"?

A "crowded field" is an area of the sky such as the plane of the Milky Way Galaxy with lots of stars, therefore it is not a result of the telescope but the structure of the Milk Way. These fields can be more difficult to comprehend, both for computer programs and humans. One example of a crowded field example is shown below:

Why do empty sky regions look white in the Exoasteroids project while stars and galaxies look dark? Shouldn't it be the other way around?

In the Exoasteroids project, the images are false-color infrared images from the WISE space telescope. These images are inverted causing what would be the black background to become white and the white objects to become black. When looking at time-series imaging, the white background is better to help the user see fluctuations in brightness

Questions About Other Webpages

What is SIMBAD?

SIMBAD (the Set of Identifications, Measurements, and Bibliography for Astronomical Data) is a handy, although more complicated, database of astronomical objects used by professional astronomers and a crucial tool for us at Exoasteroids. This blog post explains in detail how to use it to check whether an object you have found is already a known variable.

We've included a direct SIMBAD link to the object you are viewing on Zooniverse in the subject metadata. You can access it by clicking the (i) button on the bottom right of the flipbook, and then clicking the SIMBAD link.

If SIMBAD only finds one source on the image you're looking at, it will take you directly to a page of information about that source. Otherwise, SIMBAD will show you a list of astronomical objects listed in order of their distance from the center of the field of view. Click on the links to learn more about the objects that SIMBAD finds! If there are no sources in SIMBAD, you have found a white dwarf that has yet to be published yet!

SIMBAD uses a long list of abbreviations in its tables. For example, V* = Variable, WD* = white dwarf, PM* = high proper motion Star. You can learn more about SIMBAD from this Users Guide.

One of the most useful features of SIMBAD is that for each object in the catalog, it pulls up a list of papers that have been written mentioning that object. Scroll down and 3/4 down the page you should see "References". You can click "sort references" and see the titles of papers where your favorite object has been mentioned or discussed, if there are any. Be sure to browse through these; your favorite object may already be the focus of a huge international debate--or it may just have played a bit part as a calibrator or an astrometric reference.

What is ViZieR?

If you can't find what you are looking for in SIMBAD, you can use VizieR to query a longer list of astronomical catalogs, almost every catalog that has been published! You'll find a much more thorough introduction to VizieR in this blog post. But here are a few basic tips.

Like with SIMBAD, you can find a VizeR link to the object you are viewing in Zooniverse in the metadata tab of each subject.

Unlike SIMBAD, VizieR gives you LOTS of source lists, one for each of the many catalogs it searches. Each list is in order of distance from location you searched (either the coordinates you estimated, or the center of the field of view). Each catalog it searches has its own special focus and caveats, so you may have to do some reading to get the most from this powerful tool. Try combing the query results for references to "variable" since you are most likely to have identified a variable object.

What is WiseView?

Perhaps the easiest (and quickest) way to check if an object has already been published is by using WiseView. WiseView is an online tool built to view flipbooks of WISE data similar to the subjects you are viewing on Zooniverse. However, unlike the Zooniverse flipbooks, in WiseView you have the ability to change a number of different settings that are fixed in Zooniverse. These include the minbright and maxbright parameters (which set the contrast of the image), the sliding window (which controls how adjacent frames are blended into each other to reduce noise), and the Gaia overlay. Gaia is a database of known objects in the night sky.

We've included a link to the WiseView site for each subject in the metadata tab.

What is the Gaia Catalog?

The vast majority of objects presented in the Exoasteroids flipbooks are from a study that found 1.3 million candidate white dwarfs in Gaia early data release 3. Therefore, most of the objects in this Zooniverse page will be found in the Gaia catalogs. This catalog is a powerful tool to provide additional information about the white dwarf you are searching for variability around. Here is a blog post about how to use the Gaia catalog to search for various different information about the white dwarf. Some such information includes temperature, surface gravity, and distance.

The Gaia Catalog link for each object is not provided in the metadata tab.

Questions About Research

Could we end up discovering exocomets rather than exoasteroids?

Exocomets would be extremely similar to exoasteroids, where they would be comets orbiting around solar systems outside of our own. Due to their similarity to exoasteroids, it would be very plausible to find exocomets in this Zooniverse project. However, when looking more in-depth and seeing the photometric light-curve of the white dwarf the general shape will be different than an exoasteroid. This is a result of comets having more of an icy outer shell compared to asteroids, causing sublimation to happen as the exocomet gets close to the white dwarf. However, as of the current moment no exocomet impact on white dwarfs has been discovered, therefore you may be the one that can discover the first exocomet.

What other types of white dwarf behaviors could cause brightness changes, other than exoasteroids?

White dwarfs can exhibit brightness changes due to various phenomena beyond impacting exoasteroids. One common explanation for the brightness changes is the presence of a companion star in a binary system. If the secondary star is aligned with the line of sight of Earth we would see periodic changes in brightness. Additionally, if the companion star is either a main sequence star or another white dwarf, material from the secondary star may accrete onto the surface of the observed white dwarf which can lead to periodic increases in brightness, known as dwarf novae. As the accreted material undergoes nuclear reactions to stay bright and win against gravity, on the surface of the white dwarf. Additionally, if the accretion process becomes unstable, it can lead to more explosive events like supernovae. These events can be seen as changes in brightness that are irregular in period.

Furthermore, white dwarfs can also exhibit brightness variations due to pulsations in their atmospheres. These pulsations can occur from the white dwarf cooling with time or the presence of certain chemical elements in its atmosphere. These variations in brightness, known as pulsating white dwarfs, can occur on timescales ranging from minutes to hours.

Therefore, while exoasteroids can contribute to brightness changes in white dwarfs, other phenomena within the white dwarf itself can also play significant roles in variation in brightness.