<span XXXX-state="XXXXXX"></span&XX;
&XX;span XXXX-XXXXX="XXXXXX">&XX;/span>
XXXXXXX stars
XXX XXXXX+21 – first XXXXXX XXXXXXXXXX (1967), XXXXX once XXXXX X.XXX seconds.
XXXXXXXX sgr XXXX–20 – extremely strong XXXXXXXX XXXXX; XXXX XXXXXXX the brightest XXXXX-ray burst observed from XXXXX in XXXX.
black XXXXX
XXXXXX x-1 – XXXXX strong black XXXX candidate discovered; ~XX m☉, in a XXXXXX system with a blue XXXXXXXXXX.
sagittarius a* – XXXXXXXXXXXX XXXXX hole (~X million m☉) XX XXX center of the XXXXX XXX.
XXXXXXX XXXXX = collapsed XXXXXXX cores supported XX neutron XXXXXXXXXX pressure, XXXXXXXXX dense, small, XXX often XXXXXXXXXX as XXXXXXX or magnetars.
black holes = XXXXXXXXX XXXXXXX beyond neutron star mass XXXXX, XXXX an event XXXXXXX, extreme XXXXXXX, and XX XXXXXXX.
XXXX form XXXX massive stars XXX supernovae, but the XXXXXXXX factor XX XXX XXXXX core XXXX.