Pluto: Preparing for the Perfect Alignment (earthsky.org) {CORRECTED}

[eppur_se_muova]

Last edited Wed Jul 4, 2018, 11:31 AM - Edit history (1)

By EarthSky Voices in Human World | Space | July 3, 2018

On July 12, 2018, Earth will cross the sun’s face, seen from Pluto. Doing so requires a near-perfect alignment that hasn’t happened since 1931, around the time of Pluto’s discovery. Astronomer Anne Verbiscer explains why, around this event, earthly telescopes will be aimed Pluto’s way.

This article – by astronomer Anne Verbiscer at the University of Virginia – was originally published by NASA’s Pluto New Horizons website. Reprinted here with permission. {links to older page}

Every year, planets orbiting the sun beyond Earth’s orbit reach what astronomers call opposition, when they appear in the sky at the position opposite that of the sun. At opposition, the planet, satellite or asteroid and the sun line up with Earth between them. Pluto and its moons will be at opposition in 2018 on July 12 at 09:42 UTC; translate UTC to your time. Sometimes these alignments are so precise that if you were standing on the surface of one of these bodies and looking back at Earth, you would see our planet transit (or move across) the solar disk.

These “special” oppositions take place when the planet is near what is called the line of nodes. The line of nodes is the intersection of the plane of the Earth’s orbit and a planet’s orbit. Look back at the image above. The line of nodes is the intersection between the orbital plane of Pluto (purple) and that of Earth (white). Because Pluto’s orbit is significantly inclined relative to the ecliptic plane, node crossings are rare, and because Pluto’s orbit is eccentric, they occur in 87- and 161-year intervals.

If the planet is near one of these intersection points at the time of its yearly opposition, it is in near-perfect alignment with the Earth and sun. Such is the case in 2018.

Pluto was last near one of these intersection points in 1931. On July 12, 2018, as seen from Pluto, Earth will cross the sun’s face. It will not be a central transit, but it will be a transit nonetheless.
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more: http://earthsky.org/space/pluto-july-12-2018-opposition-nodes-earth-transit

[Princess Turandot]

1. This is from 2016; you might want to add '2016' to the title...

...especially since the article references 'July 8' as being in the past.

BTW, New Horizon's next planetoid rendezvous is coming up fast: it's on track for its Kuiper belt object reconnaissance on New Years Day!

[eppur_se_muova]

2. Thanks for catching this -- I tried to post from the original source, messed it up.

The article originally posted is linked in the new post -- apparently it was intended for background info.

[Judi Lynn]

3. This image at the link is amazing, as well:

When the Earth and moon transit the sun, seen from an outer planet, they might
be seen as dark dots crossing the sun’s face. On July 12, 2018, though, an
observer on Pluto would need special equipment to detect the transit, because –
at Pluto’s average distance of 3.67 billion miles (about 6 billion km) – the sun
appears only marginally larger than Jupiter does from Earth. Image via P. Molaro,
et al., from arXiv 1509.01136, 2015/NASA New Horizons blog.

Thank you for the information.