This chart is intended for skywatchers who want to find the Matariki/Pleiades star cluster in the dawn sky.
This year the brilliant planet Venus crosses the region around the same time that Matariki becomes visible. The cluster is first seen by eye in the dawn around June 14 each year. By chance Venus happens to be to the right of Matariki around the date of first visibility.
The position of Venus on June 15 is shown by the large filled circle. The planet’s position five days before and at five-day intervals afterwards is shown by the open circles.
The Matariki/Pleiades/Subaru cluster is quite faint. So even in a dark sky it has to be well above the eastern horizon before it is visible. It is also easily hidden by twilight and artificial light. Together the need for some elevation and not too much twilight mean the cluster is hidden till mid-June.
As the Earth moves around the Sun the Sun appears to move against the background stars. We can’t see the stars in daytime so this isn’t obvious. What we see is the stars being a little further west each night. Because of the tilt of the Earth’s axis the Sun’s track is tilted. At this time of year the Sun is well north of the equator. Astronomers call the Sun’s track the ecliptic. That’s because the Moon has to be on this track and either near the Sun in the sky, or opposite the Sun in the sky for a solar or lunar eclipse to occur.
The cluster is also north of the equator and not far from the ecliptic. So the cluster disappears from the evening sky around March as the Sun moves toward it from the west, from below in our evening sky view. It remains hidden through April and May as the Sun passes it by. Then it reappears in the dawn as the Sun moves east of the cluster, or downward and away in our dawn-sky view. This happens regardless of where one is in the world because the Sun’s track passes near the cluster.
Alan Gilmore 27 May 2019
For more information, visit the Royal Astronomical Society of New Zealand’s website where Peter Jacquiery has added to the event’s description.