Trans-Neptunian object

24978

24978 (1998 HJ151)

Where is it now

Distance from Sun: 43.215 AU
True anomaly: 94.42°
Distance from Earth: 43.708 AU
As of: 19 October 2026

Two-body Kepler propagation — accurate to ~0.1% for major planets over decades, less so for highly-perturbed bodies. Use JPL Horizons for high precision.

Seen from above the ecliptic, north up, to scale. Grid: Earth's orbit in blue. 24978 is 43.708 AU from Earth today (6.1 light-hours).

In the sky

Right ascension: 17h 42m 44s
Declination: -24° 47′ 53″
Constellation: Ophiuchus
Distance from Earth: 43.71 AU
Elongation from the Sun: 59.28° — near the Sun — look low at dusk or dawn

Favours the southern hemisphere; low or below the horizon from far north.

From your location

See how high it is right now, whether it is up after civil twilight, and when it rises and sets where you are.

Paste a location

How do I find my coordinates?

Google Maps on a computer

Right-click the spot where you'll be observing.
The first line of the menu is the coordinates, e.g. 51.50722, -0.12758 — click it and they're copied.
Paste them above.

Google Maps on a phone

Press and hold the spot to drop a pin.
The coordinates appear in the search bar (or on the pin's card) — tap to copy, then paste above.

A full Google Maps link works too, but the short maps.app.goo.gl share links don't carry coordinates — copy the numbers instead. We round to about a kilometre; that's all the sky calculation needs.

Know your what3words address? Paste it, e.g. ///filled.count.soap. This is optional — the three words are sent to what3words to convert them, and we don't store the address or the result.

Your location stays in your browser and is sent only for this calculation. Using a what3words address is optional; if you do, the three words go to what3words to be converted and we don't record them. Set a location first, then you can save an email alert for this object. See our privacy policy.

Two-body approximation, good to about a degree for the planets — enough to find the constellation and know whether it is up.

Orbital elements

Semi-major axis: 43.156 AU
Eccentricity: 0.0497
Inclination: 2.39°
Orbital period: 283.5 years
Perihelion: 41.011 AU
Aphelion: 45.301 AU
Longitude of ascending node: 50.44°
Argument of periapsis: 122.38°
Epoch · J2000: 2461200.5
Orbit class · TNO: Trans-Neptunian object
Earth MOID · 15,573.7 LD: 40.0175 AU
Tisserand (Jupiter): 5.868

Orbit quality

Orbit reasonably well determined (uncertainty code 4).

Observations used: 30
Data arc: 9.04 years
First observed: 28 April 1998
Last observed: 12 May 2007
Residual RMS: 0.16 ″
Solution · Otto Matic: 13 April 2021

Visual & observation

Absolute magnitude (H): 7.28

Discovery & classification

Discovered by: Luu, J. X., Trujillo, C. A., Tholen, D. J., Jewitt, D. C.
Discovery date: 28 April 1998
Discovery site: Mauna Kea

Also known as 1998 HJ151

TNO

Sources

visual properties: JPL SBDB (lookup)
orbital elements: JPL SBDB