OCA-DLR Asteroid Survey (O.D.A.S.)

1998 SJ₂

This Amor-type Asteroid has been discovered on September 18, 1998.

Latest orbital elements from the Minor Planet Center Data base.

1998 SJ2 

Epoch 1999 Jan. 22.0 TT = JDT 2451200.5                 Williams
M  43.08284              (2000.0)            P               Q
n   0.27712412     Peri.  332.12393     +0.94564983     +0.32394301
a   2.3299852      Node     9.11203     -0.25488593     +0.79263866
e   0.5004052      Incl.   10.33577     -0.20193949     +0.51651222
P   3.56           H   18.0           G   0.15           U   4
From 122 observations 1998 Sept. 18-Nov. 26, mean residual 0".54.
 

Last observed on 1998 Nov. 26. Elements from MPC 33353. 

The orbital evolution of this asteroid has been studied by numerical integration methods, taking into account the perturbations by all major planets (Mercury through Neptune, Earth and Moon were treated as a single body). The time interval from 1900 to 2100 was covered by this calculations.

This figure shows the distance between the asteroid and the Earth, revealing a typical pattern which reflects the geometry of the two orbits. It can be seen that the next favorable apparitions will be in 2005, when it should be observable for southern hemisphere sites. The calculated positional uncertainty will be about 15 arcmin, according to the NEODys ephemeris predictor.

The orbit of the Earth and part of the asteroid's orbits are shown here.

In the left panel the path of the asteroid is represented by the position of the body during the whole time interval, plotting a dot every 20 days. The Earth's orbit is displayed in a similar way. There, the position of the Earth is marked for the summer and winter solstice, and the spring and fall equinox, respectively. Also shown is the line of the mutual nodes, i.e. the orbital intersection points. The ascending node is marked with a capital Omega. The line of apsides is also drawn, marking the point of closest approach to the Sun, Perihelion with the letter q. - The orbital geometry is shown as the projection of the asteroid's orbit onto the plane of the Earth's orbit, i.e. the ecliptic, which will lead to a certain distortion for orbits with larger inclinations. The coordinate system chosen is heliocentric and given in astronomical units (AU), i.e. the mean distance between the Earth and the Sun, equal to 150 Million kilometres.

On the right-hand side of the figure some orbital parameters are given, where a represents the semi-major axis, e the eccentricity, and i the inclination. The closest and farthest point in the asteroid's orbit, perihelion and aphelion, are designated by q and Q, respectively. The orientation of the orbit is described by two angle: the longitude of the ascending node Omega and the argument of perihelion omega. These angles do vary slowly with time, due the effects of the gravitational perturbations by the planets. The range of the values covered during the time interval in consideration is therefore given.

Finally, close approaches with the Earth+Moon barycentre are listed when they occur to within 30 Million kilometres, or 0.2 AU.

A total view of the orbits of the inner planets, Mercury, Venus, Earth and Mars together with the asteroid's path projected onto the ecliptic plane.

An important parameter concerning the orbital characteristics of NEOs is the separation between the orbit of the Earth and the asteroid at the respective crossing points, the ascending and descending nodes. This plot shows the distance at these nodes, and their evolution with time, i.e. during the period 1900 - 2100.

In this table all close approaches found to any major planets are summarized. The various columns contain the date and time of the closest approach, also given in Julian Date (JD), the distance from the Earth (Delta) and from the Sun (R), in AU. The encounter velocity relative to the planet (VP) and the Sun (VH), in km/sec. N