Observation of Specific Objects


Welcome to using GORT to observe the night sky! There are many objects that you could choose to observe. Astrothemes is a great place to learn more about the types of objects you can observe. If you need help picking an object, continue reading to learn how to observe the objects to the left. To discover which objects are visible in the night’s sky using Stellarium, see the Finding Objects chapter.

Astronomy from Home has its own robotic telescope, called GORT. Since 2004, GORT has been used to take digital photographs of parts of the night sky that contain stars that vary in brightness over time. These stars are called variable stars. Cepheids are one example of variable stars who’s change in apparent brightness is due to their cyclical rate of expansion and contraction. When planets orbit a star other than our own Sun, they are called exoplanets. Sometimes exoplanets are large enough that they can make a star appear to be variable, since exoplanets can block some of the starlight. Both variable stars and exoplanet systems can be successfully observed using robotic telescopes, leading to important scientific results. Once images are taken of these fluctuations, a light curve can be created to track changes in brightness over time and identify the cause.

Nebulae can also be observed using GORT. Analyzing clouds of matter can offer us both beautiful images as well as information about their composition, temperature, and velocity. After taking images of a nebula of your choice, you can apply false-color images to view your target in detail.

See the Additional Resources tab on the left for more information on how to start analyzing image data.

Eclipsing Binary Systems (EBs)

Eclipsing binary star systems consist of two stars in mutual orbit around their center of gravity. Depending on the size of the binary system, EBs can have orbital periods ranging from a few hours to several decades. However, most of the known eclipsing systems have periods of a few days, which is most likely due to the difficulty in finding longer period systems. As in transiting exoplanet systems, the light can be dimmed if a smaller star blocks some of the light from the larger, brighter star. Unlike exoplanet systems, however, both stars emit light so the resulting lightcurves can be complicated. Basic research activities involve measuring precise times of occurrence for eclipses and the depths of the eclipses. A detailed and complete light curve can used to determine the sizes of the stars in the system, as well as the tilt of the orbital plane with respect to an observer on Earth. The figure illustrates the eclipses seen in the Kepler 16 system, which consists of two stars that are each smaller than our Sun. This system also contains at least one exoplanet.

Image from Wiki Commons. Diagram of eclipsing binary stars, shown with corresponding light curve.
Eclipsing binary star Kepler 16 light curve Image Credit

See the Additional Resources tab on the left.


Supernovae (SNs) are produced in many different ways as stars evolve. In all cases, an extremely bright outburst is observed, which declines over many weeks – months as the explosion propagates outward, creating a supernova remnant. Type II supernovae are the result of massive stars exploding when they run out of nuclear fuel. Type 1a supernovae result from collapsing white dwarf stars which have gotten too heavy to sustain nuclear burning.

Image from Wiki Commons. Type 1a supernova remnant G299 as seen in X-ray light by NASA’s Chandra Observatory, superimposed on an infrared image of background stars.
Type 1a supernova remnant G299 as seen in X-ray light by NASA’s Chandra Observatory, superimposed on an infrared image of background stars.
Credit: X-ray: NASA/CXC/U.Texas/S.Post et al, Infrared: 2MASS/UMass/IPAC-Caltech/NASA/NSF

See the Additional Resources tab on the left.

Unusual stars with outbursts or other unpredictable activity

Monitor stars with known unpredictable activity. (note: Professional observatories generally do not allocate observing time for such observations.) Normally such stars are quiescent and not active. These stars should be monitored because such events are unpredictable. When such events occur, the astronomical community should be notified so specialized instrumentation at professional facilities can be used to study these events.

Stars with unpredictable activity:
  • Cataclysmic variables (CVs)
  • ⁃ Dwarf novae
    ⁃ Recurrent novae
    ⁃ Novae
    ⁃ Polars
  • RCB stars (inverse novae)
  • YSOs (Young Stellar Objects)
  • Variable nebulae (likely illuminated by YSOs)
  • SR stars (semi-regular variables)

Follow the decline of a supernova. Supernovae (SNs) are classified as cataclysmic variables, but the outburst is far brighter than other forms of CVs.

Remnants of a type 1A supernova


Before the discovery of Cepheid variable stars, there was no way to accurately measure the distance to objects outside of our own Milky Way Galaxy. As discovered by Henrietta Leavitt in 1907 (and now known as Leavitt’s Law), the pulsation period of a Cepheid star is related to its absolute brightness. Cepheids pulse in size (and therefore in brightness) in a very regular pattern, which takes longer to complete the bigger they are. Comparing the pulsation period (how long it takes for the star to brighten, dim and brighten again) to the Cepheid’s maximum observed brightness, allows a determination of the distance to the star. This is similar to estimating the distance to a streetlight on the highway – the farther away it is, the dimmer it looks. Astronomers used Cepheid variable stars to determine distances to galaxies for the first time, when no one really understood just how far away they were (or that some Cepheids were in neighboring galaxies). NASA’s Hubble Space Telescope still performs distance measurements using Cepheid stars today, in order to more precisely measure the expansion rate of the nearby Universe. Cepheids form the first rung of the cosmic distance ladder, connecting our galaxy to its nearest neighbors. Subsequent rungs on the ladder connect our local group of galaxies to others that are more distant, and in which we cannot measure individual Cepheids.

Cepheid light curve, repeating rise and falls in intensity. From Wikicommons.
Light curve of Cepheid variable V1 in our neighbor, the Andromeda galaxy. Red points denote data taken by amateur astronomers and stars indicate four observations by the Hubble Space Telescope.
Illustration: NASA, ESA, and Z. Levay (STScI);
Science: NASA, ESA, the Hubble Heritage Team (STScI/AURA), and the American Association of Variable Star Observers;
Acknowledgment: T. Rector (University of Alaska, Anchorage)

See the Additional Resources tab on the left for more information on Cepheids.

Active Galactic Nuclei

Long Term Goals

The goal should be to achieve a time resolution of 1 month for a number of years. Multiple filter observations for a broad range of objects should be obtained at least once a month. A relatively small collection of observatories could produce an impressive collection of data with a time resolution on the order of 0.1 years. Ideally, any unusual variations would be reported and thus serve as a trigger for more intensive observation campaigns.

Interday Goals

The goal should be to establish targeted campaigns to achieve a true time resolution of 1 day for a period of several weeks. Objects exhibiting unusual variation in the long term studies, or objects selected for other reasons, can be placed on special focused campaigns. For such a campaign, cooperating observatories will attempt to obtain an observation once a night for an extended, but finite span of time. A modest distribution of observatories would be expected to produce surveillance data with a time resolution on the order of a day. Such campaigns might extend for 4, 8, or 12 weeks.

Microvariability Goals

The goal should be to establish targeted campaigns to achieve a true time resolution of several minutes for a period of several days. Objects exhibiting unusual night-to-night variations, or objects selected for other reasons, can be placed on special microvariability campaigns. For such a campaign, cooperating observatories with appropriate equipment will attempt to observe a designated target nearly continuously for several/many hours at a time throughout the night. Such a campaign should last for an extended but finite span of time. With proper planning and a uniform distribution of observatories in longitude, this should make it possible to keep a target under virtually continuous surveillance with a time resolution on the order of minutes. Such campaigns might extend for 5, 10, or 15 days.

Additional Resources

Click on each chapter below for more information on the topic.

Introduction Resources
  • To start analyzing image data in FITS files, go to the MicroObservatory Analysis page and drag the file from your computer into the Js9-4L online software program.
  • Follow the instructions on that site for analyzing the image. To learn how to determine the brightness of specific objects in an image, go to Astronomy from Home Discover page This page has links to analysis examples for different types of objects.

Observing Nebulae Resources
  • To learn how to process images of nebulae, visit the “Coloring the Universe with False-Color Images” chapter in Analysis.

Exoplanet Transit Resources

Cepheid Resources

Eclipsing Binary Star System Resources

Supernovae Resources
  • To learn more about supernova light curves, and how they can be used to measure the expansion of the Universe, see Discover Supernova.
  • Click here to see how analyzing the light from a supernova allows us to see its properties.
    Supernova E0102.