The internet was abuzz last week with news of a possible 9th
planet in our Solar System, as well as an opportunity to view all five planets
visible to the naked eye in the sky at the same time for the first time in more
than a decade. Coming on the heels of the BBC StargazingLIVE show,
and ongoing coverage of Tim Peake's mission oboard the International Space Station)
it feels like space and astronomy has never been more at the front of the UK
public’s consciousness.
The possibility of the discovery of a new planet so close to
us might seem to make a mockery of how much we claim to know about the vast
expanse of space. You might ask how we can claim we understand the structure of
galaxies in the distant Universe when we have potentially missed an entire
planet in our own solar system for so long. But this planet, if it turns out to
be real, will be very dark indeed. The predictions suggest it orbits the Sun,
20 times further out that Neptune (which in turn is 30 times further out than
the Earth). At this distance the planet would take 10,000-20,000 years to orbit
the Sun, moving incredibly slowly against the background stars. And the
illumination from the Sun would be over 300,000 times less than it is here at
Earth, making it both a very cold and dark place, as well as an incredibly hard
thing to spot with a telescope. Astronomers all over the world will now be
searching for this tiny speck of light, in an interesting parallel of several
previous searches which have happened following earlier predictions of missing
planets (these earlier searches led to the discover of Neptune, as well as
Ceres and Pluto – two objects we now consider dwarf planets, but which we
initially called planets).
Of course the last time the number of planets in our Solar
System was in the news we all had to come to terms with losing a planet. Pluto
is still exactly where it always was, but in 2006 was reclassified as a dwarf
planet following the discovery of potentially hundreds of Pluto like objects in
the outer solar system. As an astronomer it never fails to surprise me how much
this reclassification, which you might dismiss as an obscure technical discussion,
captures the public imagination. This has recently been back in the news
following the amazing pictures of Pluto sent back by the New Horizons Mission. While I’m often surprised at the interest this generates,
I’m also pleased for the opportunity it gives to remind us all that science
isn’t a fixed and static thing. We reclassify planets on the basis of new
information, and we can still have the opportunity to discover massive new
planets in our own backyard.
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| The already iconic view of Pluto from the NASA New Horizon's Mission. |
If you want to see all six planets visible to the naked eye
at once (Mercury, Venus, Earth, Mars, Jupiter and Saturn) you can get up early
on any clear morning over the next month or so. Venus and Jupiter will be the two
brightest points of light you can find in the sky – Jupiter is to the West, and
Venus to the East. In a rough line between them will be the noticeably orange
tinged Saturn and Mars. Mercury is a challenge as it’ll be a small point of
light fading into the dawn light as the Sun rises – of course Earth you can see
all the time (just look down).
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| A screenshot from the free planetarium software Stellarium showing all 5 visible planets together in the sky at 6.50am on Tue 26th Jan 2016 |
To see the International Space Station and wave at Tim Peake
as he passes by, you can look for notifications of the next visible ISS passesonline. The next ones visible from where I live (in the UK) are Feb 2nd and 3rd in the evening. The ISS looks like a steadily moving constant point of light
to the naked eye, and you see the reflected sunlight off its solar panels.
