PDS 70
 PDS 70的原行星盘与位于右侧的行星PDS 70b | |
| 观测资料 历元 J2000 | |
|---|---|
| 星座 | 半人马座 |
| 星官 | |
| 赤经 | 14h 08m 10.15455s[1] |
| 赤纬 | -41° 23′ 52.5733″[1] |
| 视星等（V） | 12[2] |
| 特性 | |
| 演化阶段 | 主序前星 （金牛T星） |
| 光谱分类 | K7[3] |
| U−B 色指数 | 0.71[4] |
| B−V 色指数 | 1.06[4] |
| 天体测定 | |
| 径向速度 (Rv) | 0.74±3.22[1] km/s |
| 自行 (μ) | 赤经：-29.697 mas/yr 赤纬：-24.041 mas/yr |
| 视差 (π) | 8.8975 ± 0.0191[1] mas |
| 距离 | 366.6 ± 0.8 ly (112.4 ± 0.2 pc) |
| 详细资料 | |
| 质量 | 0.76 ± 0.02[3] M☉ |
| 半径 | 1.26 ± 0.15[3] R☉ |
| 亮度 | 0.35 ± 0.09[3] L☉ |
| 温度 | 3972 ± 36[3] K |
| 自转 | ~50 days[5] |
| 自转速度 (v sin i) | ~10[5] km/s |
| 年龄 | 5.4 ± 1[3] Myr |
| 其他命名 | |
| 参考数据库 | |
| SIMBAD | 资料 |
PDS 70（半人马座V1032）是在半人马座的一颗非常年轻的金牛T星。它距离地球 370光年（110秒差距），它的质量为0.76 M☉，年龄大约只有540万年[3]。这颗恒星有一个原行星盘，包含两颗新生的系外行星，分别命名为PDS 70b和PDS 70c。这两颗行星已经被欧洲南方天文台的甚大望远镜直接成像。PDS 70b是第一个被确认直接成像的原行星 [6][7][3]。
发现和命名[编辑]
这颗恒星名称中的“PDS”代表Pico dos Dias天文台一项基于IRAS卫星对主序前星颜色的调查[9]。 根据这些红外颜色，PDS70在1992年被确认为金牛座T变星[10]。PDS 70的亮度准周期性变化，在可见光下以百分之几星等的幅度变动[11]。天文文献中对该恒星周期的量测不一致，从3.007天到5.1或5.6天不等[12][13]。
原行星盘[编辑]
在1992年，PDS 70首次被假设周围存在着原行星盘[14]，并于2006年在甚大望远镜上使用相位掩星日冕仪进行全面成像[2]，得到盘的半径约为140 au。在2012年，在盘中发现一个巨大的空隙（~65 au），这被认为是由行星形成引起的[5][15]。
后来发现该空隙有多个区域：在80 au中不存在大尘埃颗粒，而仅在先前观察到的65 au中不存在小尘埃颗粒。空隙的整体形状存在不对称性；这些因素表明，可能有多个行星影响空隙的形状和尘埃分布[16]。
行星系统[编辑]
| 成员 (依恒星距离) |
质量 | 半长轴 (AU) |
轨道周期 (天) |
离心率 | 倾角 | 半径 |
|---|---|---|---|---|---|---|
| b | 7.0+0.5 − MJ |
22.7+2.0 −0.5 |
45108+3580 −1790 |
0.17+0.06 −[19] |
131.0+2.9 −2.6[19]° |
1.75+0.75 − RJ |
| c | 4.4+1.1 − MJ |
30.2+2.0 −2.4 |
69945+5771 −11500 |
0.037+0.041 −0.025[19] |
130.5+2.5 −2.4[19]° |
— |
| 原行星盘 | ~65 — 140 AU | ~130° | — | |||
在2018年发表的结果中，盘中的一颗名为PDS 70 b的行星在甚大望远镜（VLT）上用SPHERE行星成像仪成像[3][7]。据估计，这颗行星的质量是木星的几倍，被认为温度约为1000 °C，和云雾缭绕的大气层；它的轨道半径近似3.22 × 109千米（21.5天文单位），公转一圈大约需要120年的时间。
行星PDS 70b的发射光谱是灰色的，没有任何特征，到2021年还没有检测到任何分子物种[20]。
第二颗行星，PDS 70 c，于2019年使用VLT的MUSE（积分场光谱仪）发现[21]。这颗行星绕主恒星运行的距离为5.31 × 109千米（35.5天文单位），比PDS 70 b更远[21]。PDS 70 c与PDS 70 b接近1:2轨道共振，这意味着PDS 70 b每完成近两圈，PDS 70 c就完成近一圈[21]。
环行星盘[编辑]
建模预测PDS 70 b已经获得了自己的吸积盘[6][22]。吸积盘在2019年的观测得到证实[23]，并且测得吸积率至少为每年5*10−7木星质量[24]。2021年，采用更新方法和数据的一项研究表明，吸积率较低，为1.4+0.2
−*10−8 MJ/年[25]。目前尚不清楚如何将这些结果相互协调以及与现有的行星吸积模型相协调；未来对吸积机制和Hα排放产生的研究应该能提供清晰的思路[26]。吸积盘的光学厚度半径3.0+0.2
− RJ，比行星本身大得多。其测热温度为1193+20
− K[17]。
2019年7月，使用阿塔卡玛大型毫米及次毫米波阵列（ALMA）的天文学家报告了有史以来首次探测到卫星形成的环行星盘。在PDS 70 c附近检测到该圆盘，在PDS 70 b附近观察到一个潜在的圆盘[27][28][29]。该圆盘由加州理工领导的研究人员使用毛纳基山的凯克天文台确认，其研究于2020年5月发表[30]。PDS 70 c周围的环行星盘影像于2021年11月被公布[31]。
可能的同轨天体[编辑]
在2023年7月，宣布可能探测到与PDS 70b行星共轨的碎片云。这些碎片的质量被认为是月球质量的0.03-2倍，可能是特洛伊行星或正在形成的行星的证据[32][33]。
相关条目[编辑]
参考资料[编辑]
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外部链接[编辑]
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