# Search

#### Help: Search for Asteroids

Our search engine provides a comprehensive exploration of the entire asteroid database, offering a wide range of filtering options based on object group, risk class, orbital parameters, observational properties, physical characteristics, and impact solutions. Orbital elements are presented at the present day, while exceptionally Epoch is queried at the near middle of the observation arc. In the search field, you can use the question mark (?) to substitute for any single character, and the asterisk (*) to replace any sequence of characters.

Below, you'll find descriptions of the parameters utilised by our search engine.

**Object Group**

In this section, you can select one or more asteroid object groups from the following options:

**Atiras**: These asteroids have their aphelion (farthest distance from the Sun) smaller than 0.983 au. Since 0.983 au is also Earth's perihelion, it follows that the orbit of the Atiras is always within that of the Earth.**Atens**: These asteroids have their semi-major axis smaller than 1 astronomical unit (au) and their aphelion greater or equal to 0.983 au. Since their aphelion is greater than Earth's perihelion, their orbits can cross the Earth orbital path.**Apollos**: These asteroids have their semi-major axis greater or equal to 1 astronomical unit (au) and their perihelium smaller or equal to 1.017 au. Since their perihelium in bigger than the Earth’s aphelion, their orbits can cross the Earth orbital path.**Atiras**: These asteroids have the perihelium between 1.017 au and 1.3 au (excluding both limits). Since their perihelion is greater than Earth's aphelion, their orbits are always outside those of the Earth.

**Object Risk Class**

Choose the risk class of the objects you want to search for. Objects can belong to the following categories:

**Risk List**: These are asteroids that have been non-zero probability of hitting the Earth.**PHA (Potentially Hazardous Asteroids)**: These are asteroids having a Minimum Orbit Intersection Distance (MOID) minor or equal to 0.05 au and an absolute magnitude (H) of 22.0 or less.**Both**: Select this option to include asteroids that belong to both the Risk List and the PHA category in your search.**All**: This option allows you to select all asteroids regardless of their class.

**Orbit Properties**

Specify the orbital parameters of the asteroids you are interested in:

**Semimajor Axis**: Semimajor Axis of the asteroid's orbit to the Sun. It can be filtered in meters (m), kilometres (km) or astronomical units (au).**Eccentricity**: Define the eccentricity of the asteroid's orbit. Eccentricity is a measure of how elongated the orbit is and is unitless.**Inclination**: Specify the inclination of the asteroid's orbit relative to the plane of the solar system in degrees (deg) or radians (rad).**Ascending Node**: Define the longitude of the ascending node in degrees (deg) or radians (rad).**Argument of Perihelion**: Provide the argument of perihelion of the orbit in degrees (deg) or radians (rad).**Mean Anomaly**: Specify the mean anomaly of the orbit in degrees.**Epoch (Near-Mid Obs. Arc)**: It is the epoch of observation in Modified Julian Date (MJD) format.**Perihelion**: Define the perihelion distance of the asteroid's orbit in meters (m), kilometres (km) or astronomical units (au).**Aphelion**: Specify the aphelion distance of the asteroid's orbit in meters (m), kilometres (km) or astronomical units (au).**Ascending Node-Earth Sep.**: Define the ascending node-Earth separation in meters (m), kilometres (km) or astronomical units (au).**Descending Node-Earth Sep.**: Define the descending node-Earth separation in meters (m), kilometres (km) or astronomical units (au).**MOID (Minimum Orbit Intersection Distance)**: Specify the Minimum Orbit Intersection Distance in It can be filtered in meters (m), kilometres (km), Earth radii (RE), Lunar distance (LD) or astronomical units (au).**Orbit Period**: Defines the orbital period in days (d).**U Parameter**: Uncertainty parameter indicating the uncertainty of the orbit of the asteroid. It is a number from 0 to 9, where incremental values denote increasing uncertainty. More information on the definition can be found at the Minor Planet Center.

**Observational parameters**

Specify the observational parameters of the asteroids you are interested in. Values refer to the 00:00 UTC epoch of the following day:

**Right ascension**: Value of the right ascension as computed from the ephemeris, referring to the center of the Earth. It can be filtered in degrees (deg) or radians (rad).**Declination**: Value of the declination as computed from the ephemeris, referring to the center of the Earth. It can be filtered in degrees (deg) or radians (rad).**V Magnitude**: Visual magnitude of the object.**Solar Elongation**: Solar elongation of the object. It can be filtered in degrees (deg) or radians (rad).**Galactic Latitude**: Galactic latitude of the object. It can be filtered in degrees (deg) or radians (rad).**Distance from the Earth**: Distance of the asteroid from the center of the Earth. It can be filtered in meters (m), kilometres (km) or astronomical units (au).**Distance from the Sun**: Distance of the asteroid from the Sun. It can be filtered in meters (m), kilometres (km) or astronomical units (au).**Sky Plane Velocity**: Apparent motion of the asteroid in the sky plane, in arcsecond per minute.**Sky Plane Uncertainty**: 1-sigma uncertainty on the celestial sphere. It refers to the 1-sigma uncertainty along the ellipse major axis (see also here). It can be filtered in arcseconds (arcsec), arcminutes (arcmin), or degrees (deg).**Days Unobserved**: Number of days since the asteroid was last observed, in days.**Arc Length**: Number of days elapsed between the first and last observations of the asteroid, in days.**Radar**: Indicates whether the object has radar-derived measurements or not.

**Physical properties**

**Rotation Direction**: Represents the direction of rotation of the asteroid, which can be either prograde (PRO) or retrograde (RETRO).**Taxonomy**: Refers to the type of spectrometric classification of the asteroid. The search allows filtering by both Bus-DeMeo and Tholen taxonomy.**Absolute Magnitude (H)**: Absolute magnitude is a measure of brightness of the asteroid if that the object would have if it were one astronomical unit (au) from both the Sun and the observer at a zero phase angle. It is expressed in absolute magnitudes (mag).**Slope Parameter (G)**: It is a parameter that quantifies the change in the absolute magnitude of an asteroid with the visual angle near opposition. It is expressed in magnitudes (mag).**Albedo**: Albedo is a measure of an astronomical object's reflectivity, indicating how much light the object reflects. The value 0.14 is used by default.**Diameter**: Refers to either the physical or the estimated diameter of the asteroid. This can be estimated based on absolute magnitude or measured using radar. In the case of asteroids with more than one spatial dimension associated with them, the search engine will return the asteroid even if only one of the 3 dimensions is within the search range. The default unit is meters (m). It can be filtered in meters (m) or kilometres (km).**Color Index Information**: Represents the object's brightness through a set of specific wavelength filters. The user can set both the bands used to observe the asteroid and the limits of the asteroid's magnitude.**Spinvector L**: Spinvector L represents the longitude component of the spin vector of an asteroid. It is a measure of the asteroid's rotation direction in degrees (deg) or radians (rad).**Spinvector B**: Spinvector B represents the latitude component of the spin vector of an asteroid. It is a measure of the asteroid's rotation direction in degrees (deg) or radians (rad).**Rotation Period**: Rotation period is the time it takes for an asteroid to complete one full rotation on its axis. It is measured in hours (h) by default. It can be filtered in seconds (s), minutes (min), hours (h), days (d) or years (yr).**Amplitude**: Refers to the variation in an asteroid's brightness during its rotation. It is typically measured in magnitudes (mag) and indicates the difference in brightness between the brightest and dimmest points on the asteroid's surface.**Sightings**: It refers to whether radar, visual data, or both are presented in the literature for the asteroid.

**Impact solutions**

**Palermo Scale**: Further information about the estimation of the diameter can be found in Definitions & Assumptions.**Cumulative Palermo Scale**: Cumulative Palermo scale of all impact solutions.**Impact Probability**: The probability of impact for any virtual impactor of a specific asteroid.**Cumulative Impact Probability**: Cumulative Impact probability of all impact solutions.**Impact Velocity**: The impact velocity of any virtual impactor of a specific asteroid. The value is in km/s.**Torino Scale**: Further information about the estimation of the diameter can be found in Definitions & Assumptions.**Year of Impact**: The year of the impact of any virtual impactor.**Expected Energy**. The expected energy of any virtual impactor. The value is in Mt.