NGC 1817

NGC 1817
Observation data (J2000 epoch)
Constellation	Taurus
Right ascension	05^h 12^m 15.(0)^s^[1]
Declination	+16° 41′ 2(4)″^[1]
Distance	6,430 ly (1,972 pc)^[2]
Apparent magnitude (V)	7.0^[3]
Apparent dimensions (V)	17.0′^[3]
Physical characteristics
Estimated age	0.8−1.2^[4] Gyr
Other designations	C 0509+166, Collinder 60

NGC 1817 is an open cluster of stars in the constellation Taurus. It was discovered by English astronomer William Herschel in February 1784.^[5] With an apparent magnitude of 7 and spanning 17 arc minutes across the sky, it is separated from the NGC 1807 cluster by just a few degrees.^[3] Indeed, the two may actually be parts of a single extended cluster.^[5]

The NGC 1817 cluster is around the same age as the Hyades, or perhaps a little younger at 0.8−1.2 billion years. The turnoff point for this cluster—where stars above a certain mass are evolving through the red giant stage—is twice the mass of the Sun.^[6] The cluster is situated in the opposite side of the sky from the Galactic Core at a separation of 32 kly (9.9 kpc) from the core,^[6] and is around 1.3 kly (0.4 kpc) away from the Galactic plane.^[4]

Measurements of the proper motion of 810 stars within a 1.5° region centered on the cluster suggest that it has at least 169 members.^[7] Of these, there is a total of 26 variable stars, including three candidate Gamma Doradus variable stars and sixteen Delta Scuti variables.^[8] This unusually high proportion of Delta Scuti variables is likely the result of the turnoff point being located within the instability strip.^[5]

References

1 2 Wu, Zhen-Yu; et al. (November 2009), "The orbits of open clusters in the Galaxy", Monthly Notices of the Royal Astronomical Society, 399 (4): 2146–2164, arXiv:0909.3737, Bibcode:2009MNRAS.399.2146W, doi:10.1111/j.1365-2966.2009.15416.x.
↑ Kharchenko, N. V.; et al. (August 2005). "Astrophysical parameters of Galactic open clusters". Astronomy and Astrophysics. 438 (3): 1163–1173. arXiv:astro-ph/0501674. Bibcode:2005A&A...438.1163K. doi:10.1051/0004-6361:20042523.
1 2 3 Gilmour, Jess K. (2012), The Practical Astronomer’s Deep-sky Companion, The Patrick Moore Practical Astronomy Series, Springer Science & Business Media, p. 123, ISBN 1447100719.
1 2 Donati, P.; et al. (January 2014), "NGC 1817, NGC 2141 and Berkeley 81: three BOCCE clusters of intermediate age", Monthly Notices of the Royal Astronomical Society, 437 (2): 1241−1258, arXiv:1311.2469, Bibcode:2014MNRAS.437.1241D, doi:10.1093/mnras/stt1944.
1 2 3 O'Meara, Stephen James (2011), Deep-Sky Companions: The Secret Deep, 4, Cambridge University Press, p. 84, ISBN 1139500074.
1 2 Reddy, Arumalla B. S.; et al. (January 2012), "Comprehensive abundance analysis of red giants in the open clusters NGC 752, 1817, 2360 and 2506", Monthly Notices of the Royal Astronomical Society, 419 (2): 1350−1361, arXiv:1109.2678, Bibcode:2012MNRAS.419.1350R, doi:10.1111/j.1365-2966.2011.19791.x.
↑ Balaguer-Núñez, L.; Jordi, C.; Galadí-Enríquez, D.; Zhao, J. L. (November 2004), "New membership determination and proper motions of NGC 1817. Parametric and non-parametric approach", Astronomy and Astrophysics, 426: 819−826, arXiv:astro-ph/0407455, Bibcode:2004A&A...426..819B, doi:10.1051/0004-6361:20041332.
↑ Andersen, M. F.; et al. (July 2009), "NGC 1817: the richest population of delta Scuti stars", Communications in Asteroseismology, 160: 9, Bibcode:2009CoAst.160....9A.

New General Catalogue 1500 to 1999

NGC 1500 NGC 1501 NGC 1502 NGC 1503 NGC 1504 NGC 1505 NGC 1506 NGC 1507 NGC 1508 NGC 1509 NGC 1510 NGC 1511 NGC 1512 NGC 1513 NGC 1514 NGC 1515 NGC 1516 NGC 1517 NGC 1518 NGC 1519 NGC 1520 NGC 1521 NGC 1522 NGC 1523 NGC 1524 NGC 1525 NGC 1526 NGC 1527 NGC 1528 NGC 1529 NGC 1530 NGC 1531 NGC 1532 NGC 1533 NGC 1534 NGC 1535 NGC 1536 NGC 1537 NGC 1538 NGC 1539 NGC 1540 NGC 1541 NGC 1542 NGC 1543 NGC 1544 NGC 1545 NGC 1546 NGC 1547 NGC 1548 NGC 1549 NGC 1550 NGC 1551 NGC 1552 NGC 1553 NGC 1554 NGC 1555 NGC 1556 NGC 1557 NGC 1558 NGC 1559 NGC 1560 NGC 1561 NGC 1562 NGC 1563 NGC 1564 NGC 1565 NGC 1566 NGC 1567 NGC 1568 NGC 1569 NGC 1570 NGC 1571 NGC 1572 NGC 1573 NGC 1574 NGC 1575 NGC 1576 NGC 1577 NGC 1578 NGC 1579 NGC 1580 NGC 1581 NGC 1582 NGC 1583 NGC 1584 NGC 1585 NGC 1586 NGC 1587 NGC 1588 NGC 1589 NGC 1590 NGC 1591 NGC 1592 NGC 1593 NGC 1594 NGC 1595 NGC 1596 NGC 1597 NGC 1598 NGC 1599 NGC 1600 NGC 1601 NGC 1602 NGC 1603 NGC 1604 NGC 1605 NGC 1606 NGC 1607 NGC 1608 NGC 1609 NGC 1610 NGC 1611 NGC 1612 NGC 1613 NGC 1614 NGC 1615 NGC 1616 NGC 1617 NGC 1618 NGC 1619 NGC 1620 NGC 1621 NGC 1622 NGC 1623 NGC 1624 NGC 1625 NGC 1626 NGC 1627 NGC 1628 NGC 1629 NGC 1630 NGC 1631 NGC 1632 NGC 1633 NGC 1634 NGC 1635 NGC 1636 NGC 1637 NGC 1638 NGC 1639 NGC 1640 NGC 1641 NGC 1642 NGC 1643 NGC 1644 NGC 1645 NGC 1646 NGC 1647 NGC 1648 NGC 1649 NGC 1650 NGC 1651 NGC 1652 NGC 1653 NGC 1654 NGC 1655 NGC 1656 NGC 1657 NGC 1658 NGC 1659 NGC 1660 NGC 1661 NGC 1662 NGC 1663 NGC 1664 NGC 1665 NGC 1666 NGC 1667 NGC 1668 NGC 1669 NGC 1670 NGC 1671 NGC 1672 NGC 1673 NGC 1674 NGC 1675 NGC 1676 NGC 1677 NGC 1678 NGC 1679 NGC 1680 NGC 1681 NGC 1682 NGC 1683 NGC 1684 NGC 1685 NGC 1686 NGC 1687 NGC 1688 NGC 1689 NGC 1690 NGC 1691 NGC 1692 NGC 1693 NGC 1694 NGC 1695 NGC 1696 NGC 1697 NGC 1698 NGC 1699 NGC 1700 NGC 1701 NGC 1702 NGC 1703 NGC 1704 NGC 1705 NGC 1706 NGC 1707 NGC 1708 NGC 1709 NGC 1710 NGC 1711 NGC 1712 NGC 1713 NGC 1714 NGC 1715 NGC 1716 NGC 1717 NGC 1718 NGC 1719 NGC 1720 NGC 1721 NGC 1722 NGC 1723 NGC 1724 NGC 1725 NGC 1726 NGC 1727 NGC 1728 NGC 1729 NGC 1730 NGC 1731 NGC 1732 NGC 1733 NGC 1734 NGC 1735 NGC 1736 NGC 1737 NGC 1738 NGC 1739 NGC 1740 NGC 1741 NGC 1742 NGC 1743 NGC 1744 NGC 1745 NGC 1746 NGC 1747 NGC 1748 NGC 1749 NGC 1750 NGC 1751 NGC 1752 NGC 1753 NGC 1754 NGC 1755 NGC 1756 NGC 1757 NGC 1758 NGC 1759 NGC 1760 NGC 1761 NGC 1762 NGC 1763 NGC 1764 NGC 1765 NGC 1766 NGC 1767 NGC 1768 NGC 1769 NGC 1770 NGC 1771 NGC 1772 NGC 1773 NGC 1774 NGC 1775 NGC 1776 NGC 1777 NGC 1778 NGC 1779 NGC 1780 NGC 1781 NGC 1782 NGC 1783 NGC 1784 NGC 1785 NGC 1786 NGC 1787 NGC 1788 NGC 1789 NGC 1790 NGC 1791 NGC 1792 NGC 1793 NGC 1794 NGC 1795 NGC 1796 NGC 1797 NGC 1798 NGC 1799 NGC 1800 NGC 1801 NGC 1802 NGC 1803 NGC 1804 NGC 1805 NGC 1806 NGC 1807 NGC 1808 NGC 1809 NGC 1810 NGC 1811 NGC 1812 NGC 1813 NGC 1814 NGC 1815 NGC 1816 NGC 1817 NGC 1818 NGC 1819 NGC 1820 NGC 1821 NGC 1822 NGC 1823 NGC 1824 NGC 1825 NGC 1826 NGC 1827 NGC 1828 NGC 1829 NGC 1830 NGC 1831 NGC 1832 NGC 1833 NGC 1834 NGC 1835 NGC 1836 NGC 1837 NGC 1838 NGC 1839 NGC 1840 NGC 1841 NGC 1842 NGC 1843 NGC 1844 NGC 1845 NGC 1846 NGC 1847 NGC 1848 NGC 1849 NGC 1850 NGC 1851 NGC 1852 NGC 1853 NGC 1854 NGC 1855 NGC 1856 NGC 1857 NGC 1858 NGC 1859 NGC 1860 NGC 1861 NGC 1862 NGC 1863 NGC 1864 NGC 1865 NGC 1866 NGC 1867 NGC 1868 NGC 1869 NGC 1870 NGC 1871 NGC 1872 NGC 1873 NGC 1874 NGC 1875 NGC 1876 NGC 1877 NGC 1878 NGC 1879 NGC 1880 NGC 1881 NGC 1882 NGC 1883 NGC 1884 NGC 1885 NGC 1886 NGC 1887 NGC 1888 NGC 1889 NGC 1890 NGC 1891 NGC 1892 NGC 1893 NGC 1894 NGC 1895 NGC 1896 NGC 1897 NGC 1898 NGC 1899 NGC 1900 NGC 1901 NGC 1902 NGC 1903 NGC 1904 NGC 1905 NGC 1906 NGC 1907 NGC 1908 NGC 1909 NGC 1910 NGC 1911 NGC 1912 NGC 1913 NGC 1914 NGC 1915 NGC 1916 NGC 1917 NGC 1918 NGC 1919 NGC 1920 NGC 1921 NGC 1922 NGC 1923 NGC 1924 NGC 1925 NGC 1926 NGC 1927 NGC 1928 NGC 1929 NGC 1930 NGC 1931 NGC 1932 NGC 1933 NGC 1934 NGC 1935 NGC 1936 NGC 1937 NGC 1938 NGC 1939 NGC 1940 NGC 1941 NGC 1942 NGC 1943 NGC 1944 NGC 1945 NGC 1946 NGC 1947 NGC 1948 NGC 1949 NGC 1950 NGC 1951 NGC 1952 NGC 1953 NGC 1954 NGC 1955 NGC 1956 NGC 1957 NGC 1958 NGC 1959 NGC 1960 NGC 1961 NGC 1962 NGC 1963 NGC 1964 NGC 1965 NGC 1966 NGC 1967 NGC 1968 NGC 1969 NGC 1970 NGC 1971 NGC 1972 NGC 1973 NGC 1974 NGC 1975 NGC 1976 NGC 1977 NGC 1978 NGC 1979 NGC 1980 NGC 1981 NGC 1982 NGC 1983 NGC 1984 NGC 1985 NGC 1986 NGC 1987 NGC 1988 NGC 1989 NGC 1990 NGC 1991 NGC 1992 NGC 1993 NGC 1994 NGC 1995 NGC 1996 NGC 1997 NGC 1998 NGC 1999

Astronomical catalog List of NGC objects

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