Wikipedia:Reference desk/Archives/Science/2020 October 31

Welcome to the Wikipedia Science Reference Desk Archives
The page you are currently viewing is a transcluded archive page. While you can leave answers for any questions shown below, please ask new questions on one of the current reference desk pages.

October 31

Halloween eclipse

Speaking of the upcoming Halloween full moon, when was the last time that a lunar eclipse had occurred on October 31 (in the Julian calendar for years prior to 1582, or the Gregorian calendar for years 1582 and later) using UTC? Also, when will be the next occurrence of a lunar eclipse on October 31? GeoffreyT2000 (talk) 02:20, 31 October 2020 (UTC)

1781 Nov 01 at 05:56:11 had an eclipse, in some western timezones this might be visible on 31st. Also 1213 AD Oct 31 04:53:28 might be visible on the really far east timezones. See https://eclipse.gsfc.nasa.gov/LEcat5/LEcatalog.html Graeme Bartlett (talk) 03:36, 31 October 2020 (UTC)

You didn't say whether this needs to be a total or partial eclipse, nor where viewed from. [1] has lots of tables for this, and as it's miserable weather here today I've extracted those for 31 Oct ~UTC+0 anywhere on the globe. Negative numbers are BCE, the rest CE. N is a penumbral eclipse, P partial, and T total:

• -1997 T
• -1951 P
• -1932 T
• -1411 T
• -1392 P
• -928 N
• -890 T
• -871 P
• -426 N
• -407 P
• -388 T
• -350 N
• 95 N
• 114 P
• 133 T
• 152 P
• 171 N
• 236 N
• 635 P
• 654 T
• 673 P
• 692 N
• 757 N
• 1175 T
• 1194 P
• 1213 N (plus one on Oct 01)
• 2096 N
• 2172 N (plus one on Oct 02)
• 2497 N
• 2544 N
• 2851 P
• 2897 T-

Bazza (talk) 15:43, 31 October 2020 (UTC)

Nearby massive black hole or somesuch?

Looking at Nasa's exoplanets web portal, I noticed something I had never seen before:

View of local star clusters

The sun sits center frame. Extending to the right is a bright strand of clusters that reaches pretty much to the center of the Milky Way. Above it spews this nearly conical ejecta. Is there a name for this phenomena? I was thinking perhaps a black hole, or maybe even a pulsar or something. Any ideas?Earl of Arundel (talk) 15:20, 31 October 2020 (UTC)

I think that this just reflects the fact that our sun is relatively far from the centre of the Milky Way. If you zoom out of the image, you'll see more clearly that the bright strand is pointing towards the centre of the galaxy. Given that the plot is of stars now known to have exoplanets, it is inevitable that our (near) earth-based observations have shown up only those star/planet systems that are relatively close to us. So there is a cluster surrounding the sun, then a larger group heading towards the centre of the galaxy, where of course the majority of candidates sit. Mike Turnbull (talk) 16:07, 31 October 2020 (UTC)

This is due to observational bias. The Kepler space telescope spent a lot of time observing one patch of sky, so most exoplanets are found in this field of view. Graeme Bartlett (talk) 20:42, 31 October 2020 (UTC)

Ah, so just an artifact of our interstellar tunnel vision, basically. Thanks everyone! Earl of Arundel (talk) 11:54, 1 November 2020 (UTC)