How to Use the JPL Small-Body Database and Horizons

What the tools are

The database has two main doors. Database Lookup, as JPL describes it, shows the available data for one object when you give a designation. That data includes orbital elements, physical parameters and discovery circumstances. Database Query does the opposite: it finds all small bodies that match the limits you set, and returns either a count of matches or the fields you choose. Horizons is a separate service that computes highly accurate ephemerides, which are tables of an object's position over time, for asteroids, comets, planetary satellites, planets, the Sun and some spacecraft.

JPL's small-body page lists several more tools that are easy to overlook.

Looking up an object

You give the lookup tool a designation for the object, such as the number 433 for Eros or the comet number 1P for Halley's Comet. Comets share the database with asteroids, so the same page layout serves both. The guide to how asteroids and comets get their names explains how to decode numbers and codes such as these.

The record is divided into sections. Here is the Eros record as the database returned it on November 11, 2026.

The guide to reading an orbit explains the elements in more detail. A few points deserve extra attention here.

First, the data arc and the number of observations tell you how much to trust the orbit. Eros was first observed on October 29, 1893 and last used in this solution on May 13, 2021, which gives it a very long record. A newly found object may have an arc of only days, and its orbit will have wide uncertainty.

Second, absolute magnitude, or H, is defined in the database documentation as the magnitude an object would have at 1 AU from both the Sun and the observer. It is a brightness, not a size. Brighter objects have lower H values. A dark object and a shiny one with the same H can have very different diameters, which is why the database lists albedo and diameter separately when they are known.

Third, not every field is filled. The discovery section, for example, exists only for numbered asteroids and comets, and many small objects have no measured diameter or albedo. A missing field means the value is not known, not that it is zero.

Counting and filtering with Query

The query tool and its programming interface can count objects by type. Using them on November 11, 2026 gave these totals.

• Asteroids in the database: 1,580,112, of which 895,910 were numbered and 684,202 were not.
• Comets in the database: 4,088.

Both counts change as new objects are added. Query also lets you ask for chosen fields, such as the name, semi-major axis, eccentricity, inclination and absolute magnitude, for every object that matches your limits. That is the way to answer questions like "which numbered asteroids have an orbit tilted more than 30 degrees?" The programming interface returns the same data as structured text, in sections for the object, the orbit, physical parameters, discovery, close approaches and more. It is the route to use if you want a spreadsheet instead of a web page.

How do the numbers get there? Observers send position measurements to the Minor Planet Center, which handles designations. The overview of how minor planets are discovered follows that path from first image to recorded orbit.

Finding a body in the sky with Horizons

An orbit alone does not tell you where to point a telescope. Horizons does the calculation. In the web app you choose the target, the observer's location and a span of dates with a step size, and the service returns a table of positions. JPL says the web app offers nearly all of the command-line capabilities, but not searches across whole populations of small bodies or custom close-approach tables. For those, the database's Query tool is the better fit. Horizons can also be reached by email batch files, by a command-line connection and by a programming interface.

JPL adds a warning that it is a best-effort service. It cites historical uptime above 99.9 percent, but anything critical should allow for outages.

If you do not know which object you are looking for, the Identification tool works the other way around. Give it a date, a time and a patch of sky, and it lists the known small bodies there. For planning, the What's Observable? tool lists bodies observable from a given site under your own criteria.

A real telescope session needs one more reminder. Most asteroids are far fainter than anything you can see by eye, and never aim binoculars or a telescope at the Sun without a proper solar filter made for that purpose. Use the positions to plan a night session, not to look during the day.

Common mistakes and myths

"The database tells you if an asteroid will hit Earth." The record shows the orbit and a list of close approaches computed from it. It is not a risk assessment. For a well-known case, the story of the Apophis flyby covers what space agencies say about one asteroid's close approach.

"H is the diameter." H is brightness at a standard distance. Size needs albedo too.

"A blank field means zero." It means unknown.

"The numbers are final." Orbits are refined as new observations arrive, and counts grow every night. Always note the date.

"Horizons positions are exact for any object." The accuracy follows the orbit. An object observed for only a few days gives much weaker predictions than Eros, which has been tracked since 1893.

Frequently asked questions

Are comets in the same database as asteroids?

Yes. Halley's Comet has a record under 1P and Comet NEOWISE has one under C/2020 F3. Both return orbital elements in the same layout as an asteroid record.

Why does the database show a different diameter than another website?

Sizes come from different methods and different dates, and each carries an uncertainty. Eros is listed at 16.84 km plus or minus 0.06. Check the plus-or-minus figure before comparing.

What does epoch mean on an orbit page?

It is the date to which the orbital elements apply. Because planets tug on small bodies, the elements are tied to that moment and refreshed when new data arrive.

Is the database the same as the Minor Planet Center?

They are separate. The Minor Planet Center receives observations and assigns designations. JPL's database presents orbit solutions, physical data and discovery details for each object.