RX J0852.0−4622 (also known as G266.2−1.2) is a supernova remnant. The remnant is located in the southern sky in the constellation Vela ("sail"), and sits (in projection) inside the much larger and older Vela Supernova Remnant. For this reason, RX J0852.0−4622 is often referred to as Vela Junior (Vela Jr.).^[1][2] There have been a minority of suggestions that the remnant may be a spurious identification of a complicated substructure within the larger and better studied Vela SNR, but most studies accept that G266.2−1.2 is a SNR in its own right. Indeed, its detection in the high energy Teraelectronvolt range by the High Energy Stereoscopic System in 2005 is strong confirmation of such.^[3]

Quick Facts Event type, Date ...

RX J0852.0−4622 or Vela Junior

The purple in this image is a false color indication of the x-rays detected by the Chandra X-Ray Observatory emanating from the edge of the supernova remnant due to a shockwave front. The center of the remnant is out of frame, off to the left.
Event type	Supernova remnant
SN
Date	1998
Constellation	Vela
Right ascension	08h 52m
Declination	−46° 22′
Epoch	J2000.0
Galactic coordinates	286.9460 +42.4568 (34" W, 10" S)
Distance	>1500 ly
Remnant	CXOU J085201.4-461753
Notable features	central object in SNR RX J0852.0−4622 = AX J0851.9−4617.
Other designations	SNR G266.2-01.2, SNR G266.3-01.2, 3FHL J0851.9-4620e, RX J0852.0-4622, 2FGL J0851.7-4635, 3FGL J0852.7-4631e, 2FHL J0852.8-4631, 2FHL J0852.8-4631e
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Close

It was found in 1998 with an analysis of data from the ROSAT x-ray telescope.^[4] Published simultaneously with its discovery was a claimed detection by the Compton Gamma Ray Observatory of a gamma ray spectral line of ⁴⁴Ti which has a half-life of 60 years and therefore seemed to indicate a young provenance for the supernova, perhaps the youngest one yet discovered.^[5] Later independent groups could not reproduce the detection, and so the consensus is that the identification of this line was likely spurious.^[6] Since the age and distance are correlated, a young, nearby supernova like this has inspired some detective work to identify evidence that such a supernova may have been observed and recorded by groups of people,^[7] and geochronologists have looked for evidence of a young supernova in tree ring^[8] and ice core data,^[9] but identification of claimed correlate signals have not been conclusively made.^[2] The latest analyses of the remnant indicate an age of at least 2400 years (and possibly much older), a distance of no less than 500 parsecs, and a radial size of at least 8 parsecs.^[2]

The central compact object (CCO) was discovered in 2001.^[10] In the initial Chandra X-ray image and deeper images thereafter, no pulsations were detected from the compact remnant, which is believed to be the neutron star CXOU J085201.4-461753. A different pulsar was suggested as the remnant,^[11] but its kinematics do not conform as well to the observed kinematics of the remnant shell.^[2]