The NSF Rubin Observatory Credit: Rubin Observatory/NOIRLab/NSF/AURA/P. Horálek (Institute of Physics in Opava) government photograph in the public domain.

Comets are deeply mysterious and have sought since antiquity. The earliest written records of comets date back to ancient Babylon, around 500 BC, and many cultures interpreted these celestial phenomena as omens or messages from the gods. However, it wasn’t until the 16th century that the scientific study of comets began to truly take shape.

In 1531, the German astronomer Michael Maestlin documented the return of a comet, marking one of the first instances where an astronomer connected a comet’s periodic nature with the idea that it was an object in orbit around the Sun. Later, in 1682, the famous English astronomer Edmond Halley observed that a comet which had appeared in 1607 and 1682 was the same object, suggesting comets had elliptical orbits. Halley’s Comet, helped establish the idea that comets were not random in their appearance but part of our solar system’s clockwork mechanism.

The first comet discovered through a telescope was in 1618, when Johannes Kepler used his observations of the night sky to note the presence of a comet near the constellation of Andromeda. The 19th and early 20th centuries saw an expansion of observatories and technological advancements in telescopes. The invention of photographic plates in the late 1800s allowed astronomers to capture images of the night sky with far more detail than ever before. As a result, astronomers could begin scanning vast sections of the sky in search of moving objects that could be comets.

In the 20th century, the rise of professional comet hunting truly took off with large telescopes, and the introduction of wide-field surveys helped make discoveries more routine. Observatories like the Mount Wilson Observatory in California, the Palomar Observatory, and the Mauna Kea Observatory in Hawaii became central to the discovery of new comets, some of which became famous in their own right, such as Comet Hale-Bopp (1995) and Comet NEOWISE (2020).

Today, many of the world’s most powerful telescopes are still in use for comet hunting. These observatories often employ both optical and infrared technologies to scan the night sky for signs of a comet’s unique characteristics: a bright core (nucleus) and a long tail.

Some of the most notable modern observatories include:

• The Pan-STARRS (Panoramic Survey Telescope and Rapid Response System): Located in Hawaii, Pan-STARRS is known for its wide-field sky surveys. This observatory has discovered hundreds of asteroids and comets, often catching those that could potentially impact Earth.
• The Sloan Digital Sky Survey (SDSS): Using the Apache Point Observatory in New Mexico, SDSS has mapped a vast portion of the sky, leading to the discovery of several comets, as well as asteroids, galaxies, and other astronomical phenomena.
• The Catalina Sky Survey: Based in Arizona, this project focuses on detecting near-Earth objects (NEOs), including comets. It is part of the search for hazardous asteroids and comets that could pose a threat to Earth.
• The European Southern Observatory (ESO): Operating several telescopes across Chile, the ESO is instrumental in comet research, providing valuable data to both professional and amateur astronomers.

If you look in a modern comet observing guide, such as Sky Safari, you will often see the names of these observatories and widefield comet scans attached to some of the major and most dramatic modern comets. This includes the comet that we have been talking about C/2023 Tsuchinshan Atlas A3. What’s in a name. Tsuchinshan: This part of the name is derived from the Tsuchinshan Observatory, which is located in China. Atlas: This part refers to the ATLAS (Asteroid Terrestrial-impact Last Alert System) survey, which is an automated system that scans the sky for asteroids and comets, especially those that could potentially impact Earth.  A3: This part of the name is used to indicate the sequence of the comet’s discovery within that particular year. In this case, A3 signifies that this is the third comet discovered in 2023 that has been assigned a name in the “A” group. The “A” typically represents the first half of the year.

However, as I write there is a major game changer in comet, and asteroid, and novae  on the horizon [sic]. Coming on line this year is the launch of  Vera C. Rubin Observatory in Chile’s Atacama Desert. It will feature  a 8.4-meter telescope. If like me, you grew up when the 200 inch telescope at Palomar was king, pause a moment and recognize that that is ~328 inches.  The telescope is equipped with a state-of-the-art camera with a field of view larger than that of any previous sky survey telescope. It can capture the entire sky continuously every three nights looking for the telltale changes due to asteroids, comets, and novae. The observatory’s primary mission is to conduct the Legacy Survey of Space and Time (LSST), a 10-year project that will scan the entire sky repeatedly, providing a treasure trove of data on asteroids, comets, and other celestial objects.

The camera at the Vera Rubin Observatory has an extremely wide field of view that spans about 9.6 square degrees (that’s ~ twenty moon diameters). Its 3.2 gigapixel detector, will be the largest digital camera in the world. All of this boils down to a spatial resolution of about 0.2 arcseconds per pixel.

It once was true that revolution was rare, particularly scientific revolution. Now as we aspire to the singularity they are ever more familiar. Ten years from now we will speak very differently about the solar system and the universe. Vera Rubin will enable us to lift up a thousand veils and extend relentlessly the margins of the known universe.

I am part of all that I have met;
Yet all experience is an arch wherethrough
Gleams that untraveled world, whose margin fades
For ever and for ever when I move.

Ulysses

Alfred, Lord Tennyson