Narrative:

At 11;000 feet approximately 30-40 miles from ZZZ; we experienced and complied with TCAS RA. We noticed traffic about 20 miles away climbing toward us and could see traffic both on TCAS and visually. When traffic got inside of 10 miles it was climbing rapidly right toward our flight path. At approximately 5 miles I asked center if [they] were talking to [the] aircraft. No response; then simultaneously our TCAS gave us an RA advisory to climb [at] greater than 1;000 FPM. I disconnected autopilot and put the aircraft into a steep climb to avoid a collision and simultaneously advised [ATC] of climb. During the RA maneuver we observed traffic come within 500 feet of aircraft. After clear of traffic I advised ATC that [we] were descending back down to 11;000. I spoke with center after I landed on phone and was advised they were reviewing the incident. Spoke with center again [the next day]. They called me and said the two aircraft closest points were 1.74 miles and 500 feet. I'm glad I was very alert and my training took over or a lot of lives could have been lost.the cause of this event was ATC controller not recognizing the aircraft was climbing into our flight path and did not advise us of oncoming aircraft.

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Original NASA ASRS Text

Title: CRJ-900 Captain reported an airborne conflict while on approach.

Narrative: At 11;000 feet approximately 30-40 miles from ZZZ; we experienced and complied with TCAS RA. We noticed traffic about 20 miles away climbing toward us and could see traffic both on TCAS and visually. When traffic got inside of 10 miles it was climbing rapidly right toward our flight path. At approximately 5 miles I asked Center if [they] were talking to [the] aircraft. No response; then simultaneously our TCAS gave us an RA advisory to climb [at] greater than 1;000 FPM. I disconnected autopilot and put the aircraft into a steep climb to avoid a collision and simultaneously advised [ATC] of climb. During the RA maneuver we observed traffic come within 500 feet of aircraft. After clear of traffic I advised ATC that [we] were descending back down to 11;000. I spoke with Center after I landed on phone and was advised they were reviewing the incident. Spoke with Center again [the next day]. They called me and said the two aircraft closest points were 1.74 miles and 500 feet. I'm glad I was very alert and my training took over or a lot of lives could have been lost.The cause of this event was ATC controller not recognizing the aircraft was climbing into our flight path and did not advise us of oncoming aircraft.

Data retrieved from NASA's ASRS site and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.