Hubble Space Telescope Images of SN 1987A: Evolution of the Ejecta and the Equatorial Ring from 2009 to 2022

Abstract

Supernova (SN) 1987A offers a unique opportunity to study how a spatially resolved SN evolves into a young SN remnant. We present and analyze Hubble Space Telescope (HST) imaging observations of SN 1987A obtained in 2022 and compare them with HST observations from 2009 to 2021. These observations allow us to follow the evolution of the equatorial ring (ER), the rapidly expanding ejecta, and emission from the center over a wide range in wavelength from 2000 to 11,000 Å. The ER has continued to fade since it reached its maximum ∼8200 days after the explosion. In contrast, the ejecta brightened until day ∼11,000 before their emission levelled off; the west side brightened more than the east side, which we attribute to the stronger X-ray emission by the ER on that side. The asymmetric ejecta expand homologously in all filters, which are dominated by various emission lines from hydrogen, calcium, and iron. From this overall similarity, we infer the ejecta are chemically well mixed on large scales. The exception is the diffuse morphology observed in the UV filters dominated by emission from the Mg ii resonance lines that get scattered before escaping. The 2022 observations do not show any sign of the compact object that was inferred from highly ionized emission near the remnant’s center observed with JWST. We determine an upper limit on the flux from a compact central source in the [O iii] HST image. The nondetection of this line indicates that the S and Ar lines observed with JWST originate from the O free inner Si–S–Ar-rich zone and/or that the observed [O iii] flux is strongly affected by dust scattering.

Planetary Nebula Morphologies Indicate a Jet-Driven Explosion of SN 1987A and Other Core-Collapse Supernovae

“…In an earlier paper (Soker 2024c [71]), I determined that the 'keyhole' of SN 1987A has a rim-nozzle asymmetry, in which the front of one bubble (cavity; lobe) in a pair is closed by a rim, which is a dense cap in three dimensions, or a partial shell, projected as an arc onto the plane of the sky, while the opposite bubble (cavity; lobe) has a nozzle on its front, namely, a low-intensity opening. I present the rim-nozzle asymmetry in Section 2, where I also show the new high-quality observations by Rosu et al (2024) [57] that allowed me to identify the rim-nozzle asymmetry in the ejecta of SN 1987A; in some places, I will refer to SN 1987A as CCSNR 1987A. In Section 3, I present PNe with the rim-nozzle asymmetry; in Section 4, I study three other CCSNRs with the rim-nozzle asymmetry.…”

“…The high-quality HST observations that Rosu et al (2024) [57] published recently led me to identify the 'keyhole' structure of SN 1987A ejecta as having rim-nozzle asymmetry (Soker 2024c [71]). In Figure 1, I present images that Rosu et al (2024; for the keyhole, see also Matsuura et al 2024 [38]) took 12,980 days after the explosion in nine filters.…”

“…In Section 4, I present SNR G309.2-00.6, which, like SN 1987A, has both the rim-nozzle asymmetry and two crescents (arcs). [57], with the marks identifying the bubbles (black arrows), nozzle, and rim (red arrows), from Soker (2024c [71]). The bright structure with the low-intensity inner zones inside the purple line in the lower-right panel is the 'keyhole'.…”

“…Figure 2 shows that the galaxy group NGC 5813 has several bubbles. I refer to the inner pair of bubbles, which possesses a rim-nozzle asymmetry, as the marks in Figure 2 [57], with the marks identifying the bubbles (black arrows), nozzle, and rim (red arrows), from Soker (2024c [71]). The bright structure with the low-intensity inner zones inside the purple line in the lower-right panel is the 'keyhole'.…”

“…Figure 1. HST/WFC3 images of SN 1987A in nine filters and at 35.5 years post-explosion, adapted from Rosu et al (2024)[57], with the marks identifying the bubbles (black arrows), nozzle, and rim (red arrows), from Soker (2024c[71]). The bright structure with the low-intensity inner zones inside the purple line in the lower-right panel is the 'keyhole'.…”