2月2日可观测绿色彗星 上次到访太阳系在5万年前
转自：CGTN
一颗绿色彗星正“逼近”地球，预计于北京时间2月2日经过近地点，届时若观测条件良好，肉眼或清晰可见这位“天外来客”的身影。
美联社援引美国国家航空航天局消息报道，这颗编号C/2022E3的彗星将以每小时逾20万千米的相对速度掠过近地点。距离最近时，它距离地球约0.28个天文单位，即4200万千米。
1个天文单位指太阳到地球的平均距离，约为1.5亿千米。
C/2022E3彗星来自距离太阳5万至10万个天文单位的奥尔特星云，研究人员去年3月首次发现它。随着它离地球越来越近，去年12月以来，北半球越来越多天文爱好者报告用小型望远镜或双筒望远镜观测到它。至今年1月末，从地球上观测，这颗彗星在地平线上升得越来越高、越来越亮。
AgreencometismakingitsclosestapproachtoEarthandislikelytobevisibletothenakedeyeundertherightconditions.
Thecomet,withacumbersomenameC/2022E3(ZTF),wasfirstseenlastMarchbyastronomersusingtheZwickyTransientFacility,awidefieldcameraatCaltech'sPalomarObservatory.
Ithasalongorbitalperiodof50,000yearsaccordingtoNASA'sJetPropulsionLaboratory(NASAJPL)andistravelingclosesttoEarthonthenightofFebruary1toFebruary2atadistanceofaround42millionkilometers.
Withtheassistanceofbinocularsandsmalltelescopes,thecomethasbecomevisibleinthenorthernskysinceitsclosestapproachtothesun,itsperihelion,onJanuary12.
AnobservationteaminBeijingcapturesthe"greencomet"C/2022E3(ZTF)onJanuary29,2023./BeijingPlanetarium
Toobserversonthenorthernhemisphere,justlookinthenorthernskiesjustaftersunsetandtrytocatchthecomet'sgorgeousgreentailcausedbychemicalparticles,especiallydiatomiccarbonandcyanogen,initsgascloud,orcoma.
AccordingtoSpace.com,C/2022E3(ZTF)willbecomevisibleataround2349GMTonFebruary1whenitisat49degreesoverthenorthernhorizonandwillclimbtoitshighestpointinthesky,58degreesoverthenorthernhorizon,ataround0246GMT.
Afterthecomet'sperigee,thecometwillstillbevisibleinearlyFebruarybutwillgraduallydimasittravelssouthwardandpassesthroughtheAurigaconstellationfollowedbyitsshinenearMarsintheTaurusconstellation.Luckily,skygazersinthesouthernhemispherewillhaveagoodchanceofspottingitthen.
Herearesomegeneraltipsforcatchingthiscomet:
1.Getawayfromcitylightandfindasafedarkplace.Thecomet'smagnitudeisjustdimlyvisibletothenakedeyebutmostviewerswillneedaninstrument.
2.LookforthePolaris,ortheNorthStar.ThecometwillbejustabovethePolarisatitsperigee.