PHA Database Page 2

PHA Catalogue Vol. II — NASA/JPL CNEOS

Radar imaging: Delay-Doppler radar (Goldstone / Arecibo) has resolved ~900 NEAs, revealing shapes, rotation, binaries and surface features. Pioneered by the JPL/Caltech radar group (Ostro, Hudson et al.). Each pixel = metres of resolution at close approach.

Palermo Technical Scale — context

<−2 Negligible −2→0 Monitor 0→2 Elevated >2 Certain

Torino 0 — No hazard Torino 1 — Very low Torino 2–3 — Attention Torino 4+ — Concern

Designation / Name H mag Diam. MOID Period Torino

Large & well-characterised PHAs

(887) Alinda

Alinda RADAR 2025

Amor · S-type · 1:3 resonance

13.8

~6.6 km

0.0449 au

3.91 yr

Discovered

1918 Jan 3

Discoverer

M. Wolf (Heidelberg)

Albedo

~0.12

Rotation period

~28–74 h (NPA suspect)

Eccentricity

0.568

Semi-major axis

2.477 au

Inclination

9.4°

Perihelion

1.062 au

Long axis (radar)

≥ 5.2 km (Goldstone)

Impact prob.

None known

One of the three oldest known PHAs (discovered 1918). Alinda-class objects occupy the 1:3 mean-motion resonance with Jupiter (~3.91 yr period), which pumps their eccentricity over time until they become Earth-crossers. Goldstone radar imaging in Jan 2025 revealed a minimum long-axis of 5.2 km, confirming it as one of the largest known PHAs. Source: JPL SBDB · JPL Radar echo.jpl.nasa.gov (Alinda 2025)

(433) Eros

Eros NEAR Shoemaker

Amor · S-type · First numbered NEA

11.2

~16.8 km

0.1498 au

1.76 yr

Discovered

1898 Aug 13

Discoverers

G. Witt & A. Charlois

Dimensions

34.4 × 11.2 × 11.2 km

Albedo

0.25

Rotation period

5.270 h

Eccentricity

0.223

Semi-major axis

1.458 au

Inclination

10.8°

NEAR landing

2001 Feb 12 (first ever)

Mass

6.69 × 10¹⁵ kg

MOID note

Amor — does not cross Earth orbit

Impact prob.

None known

First known near-Earth asteroid (discovered 1898) and first NEA visited by spacecraft. NASA's NEAR Shoemaker orbited Eros for a year (2000–2001) and then landed — the first soft landing on an asteroid. Its MOID of 0.149 au technically makes it a PHA only for the very largest size class; H=11.2 is far below H=22. Eros is an Amor, so its orbit does not currently cross Earth's. Source: JPL SBDB · NEAR mission final report · MPC

(2100) Ra-Shalom

Ra-Shalom RADAR

Aten · C/K-type

16.1

~2.3 km

0.0185 au

0.76 yr

Discovered

1978 Sep 10

Discoverer

E. Helin (Palomar)

Dimensions (radar)

2.8 × 2.4 × 1.8 km

Effective diameter

2.3 ± 0.2 km

Albedo

0.13 ± 0.03

Rotation period

19.793 h

Eccentricity

0.437

Semi-major axis

0.832 au

Inclination

15.8°

Yarkovsky det.

Confirmed (Nugent et al.)

Thermal inertia

~103 J m⁻² s⁻⁰·⁵ K⁻¹

Impact prob.

None known

Largest confirmed PHA in the Aten class (semi-major axis < 1 au). Named after the Egyptian sun-disc god Ra and the Hebrew "Shalom" (peace), reflecting its binational discovery. Radar imaging at Goldstone and Arecibo across multiple apparitions (1981–2003) produced a detailed 3-D shape model with 1,148 facets at ~90 m resolution. Surface features resemble those seen on Eros. Yarkovsky drift confirmed by Nugent et al. (2012). Source: Shepard et al. (2008) Icarus · JPL SBDB

First radar-imaged & milestone PHAs

(4769) Castalia

Castalia FIRST RADAR MODEL

Apollo · S-type · Contact binary

18.0

~1.4 km

0.0402 au

1.10 yr

Discovered

1989 Aug 9

Discoverer

E. Helin (Palomar 18")

Albedo

~0.12

Rotation period

4.095 h

Eccentricity

0.483

Semi-major axis

1.063 au

Inclination

8.9°

Radar model

Hudson & Ostro (1994)

Shape

Two-lobe contact binary

Impact prob.

None known

Historic milestone: the first asteroid ever modelled in 3-D from radar data (Hudson & Ostro, Science 1994). Delay-Doppler observations during its Aug 1989 close approach revealed a bi-lobed "peanut" shape — two ~0.8 km lobes in contact, suggesting a low-speed merger of two bodies. This shape is now known to be common among PHAs. Source: JPL Radar Group · Science 270, 84 (1995) · JPL SBDB

(6489) Golevka

Golevka YARKOVSKY DET.

Apollo · Q/V-type · Cubic shape

19.2

~530 m

0.0397 au

3.99 yr

Discovered

1991 May 10 (1991 JX)

Discoverers

E. Helin et al. (Palomar)

Radar cross-section

~0.1 km²

Albedo (radar OC)

0.18 ± 0.09

Rotation period

6.026 h

Eccentricity

0.598

Semi-major axis

2.516 au

Inclination

2.3°

Yarkovsky drift

First direct detection (2003)

Drift rate

~15 km/yr (Chesley et al.)

Intercontinental radar

Goldstone–VLA–Evpatoria–Kashima

Impact prob.

None known

Science landmark: the first direct detection of the Yarkovsky effect in an asteroid (Chesley et al., Science 2003). By comparing Goldstone radar astrometry from 1991 and 1995 against predictions, a drift of ~15 km/yr was detected — demonstrating that solar radiation pressure can measurably alter asteroid orbits. Also notable for a 1995 intercontinental bistatic radar experiment involving four observatories. Source: Chesley et al. (2003) Science 302 · Hudson et al. (2000) Icarus

(1620) Geographos

Geographos RADAR

Apollo · S-type · Most elongated body

15.6

~2.5 km

0.0301 au

1.39 yr

Provisional desig.

1951 RA

Discovered

1951 Sep 14

Discoverers

A.G. Wilson & R. Minkowski (Palomar)

Dimensions

5.11 × 1.84 × 1.55 km (elongated)

Albedo

0.26

Rotation period

5.222 h

Eccentricity

0.335

Semi-major axis

1.246 au

Inclination

13.3°

Clementine target

1994 (mission lost before flyby)

Named after

National Geographic Society

Impact prob.

None known

Radar imaging during the 1994 close approach revealed Geographos to be the most elongated object in the Solar System at the time — aspect ratio ~2.76:1. Intended target of NASA's Clementine spacecraft in 1994, but a software error caused Clementine to exhaust its thruster fuel, ending the mission before the flyby. Named for the National Geographic Society in recognition of its support for the Palomar Observatory Sky Survey. Source: Ostro et al. (1996) Icarus · JPL SBDB

Historic alarms & close approach PHAs

(35396) 1997 XF11

1997 XF11

Apollo · Xk-type · 1998 media panic

17.0

~0.7–1.4 km

0.0006 au

1.73 yr

Discovered

1997 Dec 6

Discoverer

Spacewatch (T. Gehrels)

Precovery

1990 Mar 22 (recovered)

Albedo

~0.14

Rotation period

3.26 h

Eccentricity

0.484

Semi-major axis

1.332 au

Inclination

4.1°

2028 flyby

~960,000 km (Oct 26)

1998 impact claim

Retracted within 24 hours

Impact prob.

None known

On 1998 Mar 11, the IAU issued a circular stating 1997 XF11 had a small but non-zero chance of Earth impact in 2028 — the announcement triggered a global media panic. Within 24 hours, precovery images from 1990 were identified, extending the orbital arc and eliminating all impact risk entirely. Became a landmark event in establishing proper impact announcement protocols and the Torino Scale (formalised 1999). Source: IAU CBAT 1997 XF11 · Marsden (1998) · JPL SBDB

(153814) 2001 WN5

2001 WN5

Apollo · S-type · Sub-lunar flyby

18.2

~0.9 km

0.00175 au

2.24 yr

Discovered

2001 Nov 20

Survey

LONEOS

Diameter (NEOWISE)

0.9 km

Eccentricity

0.558

Semi-major axis

1.655 au

Inclination

1.0°

2028 flyby

2028 Jun 26 (~250,000 km)

Flyby distance

~0.65 lunar distances

Apparent mag. at flyby

~6.7 (binocular)

Sentry listing

Removed 2002

Impact prob.

None known

Will pass at ~250,000 km on 2028 Jun 26 — inside the orbit of the Moon — reaching apparent magnitude ~6.7 (just visible to the naked eye in good conditions). This makes it a potential "rehearsal" close-approach target ahead of Apophis's 2029 flyby. Briefly on the Sentry risk list in early 2002 before more observations ruled out impact. Source: Thirouin et al. (2021) ADS abstract · CNEOS · MPC

2007 FT3

2007 FT3 ◆ LOST

Apollo (provisional) · Lost asteroid

22.3

~340 m

~0.00 au

~1.36 yr

Discovered

2007 Mar 20

Last observed

2007 Mar 21 (1-day arc)

Size estimate

~340 m (brightness-based)

Orbital arc

Very short — uncertain orbit

Oct 2024 impact prob.

0.0000087% (1:11.5M)

Mar 2030 impact prob.

0.0000096% (1:10M)

Impact energy

~2.6 Gt TNT equiv.

Sentry status

Active (uncertainty-driven)

2030 impact probability

1 in 10M

A "lost asteroid" — observed only on two nights in March 2007 (1-day arc), then never recovered. The extremely short arc means its orbit is poorly constrained, and many of the virtual orbits computed within uncertainties intersect Earth on various dates. Sentry listing reflects orbital uncertainty, not a genuine elevated risk. Impact energy of ~2.6 Gt TNT would cause major regional damage but not a global catastrophe. Source: NASA CNEOS · Live Science (NASA source data) · JPL Sentry

Apollo namesake & Aten class

(1862) Apollo

Apollo CLASS NAMESAKE

Apollo · Q-type · Binary

16.3

~1.5 km

0.0247 au

1.81 yr

Discovered

1932 Apr 24

Discoverer

K. Reinmuth (Heidelberg)

Lost / recovered

Lost 1932; recovered 1973

Albedo

0.26

Rotation period

3.065 h

Eccentricity

0.560

Semi-major axis

1.471 au

Inclination

6.4°

Moonlet (S/2005)

~80 m diameter; 3.1 km sep.

Impact prob.

None known

Class namesake for all Apollo-type asteroids — objects whose semi-major axis exceeds 1 au and whose perihelion is within Earth's orbit. Discovered in 1932 by Karl Reinmuth, then lost for 41 years before being recovered in 1973. A small moonlet (~80 m) was discovered in 2005 via radar, making it a confirmed binary system. Source: JPL SBDB · MPC · Ostro et al. (2005) radar binary detection

(2062) Aten

Aten CLASS NAMESAKE

Aten · S-type · First Aten discovered

16.8

~0.9 km

0.0191 au

0.95 yr

Discovered

1976 Jan 7

Discoverer

E. Helin (Palomar)

Albedo

~0.20

Rotation period

40.77 h

Eccentricity

0.182

Semi-major axis

0.967 au

Inclination

18.9°

Perihelion

0.790 au

Aphelion

1.143 au (barely crosses)

Impact prob.

None known

Class namesake for Aten-type asteroids — NEAs with a semi-major axis less than 1 au, meaning they spend most of their orbit inside Earth's orbit. When discovered in 1976 by Eleanor Helin, it was the first asteroid found with an orbit mostly inside Earth's. Named after the Egyptian sun-disc deity. Only ~2,000 Atens are known (about 7% of all NEAs). Source: JPL SBDB · Helin (1976) IAUC 2901 · MPC

(25143) Itokawa

Itokawa Hayabusa

Apollo · Sq-type · Rubble pile

19.1

~330 m

0.0130 au

1.52 yr

Discovered

1998 Sep 26 (1998 SF36)

Survey

LINEAR

Dimensions

535 × 294 × 209 m

Albedo

0.23

Rotation period

12.132 h

Eccentricity

0.280

Semi-major axis

1.324 au

Inclination

1.65°

Sample returned

2010 Jun 13 (1,500 grains)

Structure

Rubble pile (~40% void)

Impact prob.

None known

Target of JAXA's original Hayabusa mission (2005–2010) — the first asteroid sample return. Itokawa is a classic S-type rubble pile: two distinct lobes (Itokawa Head and Body) loosely bound, with ~40% porosity. ~1,500 grains of olivine-rich material were returned in June 2010. Named after Hideo Itokawa, "father of Japanese rocketry." Source: JAXA Hayabusa mission · Science (Fujiwara et al. 2006) · MPC NHATS

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